Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

128 files changed, 43111 insertions, 0 deletions

diff --git a/src/librustdoc/Cargo.toml b/src/librustdoc/Cargo.toml
new file mode 100644
index 000000000..ddaa7438e
--- /dev/null
+++ b/src/librustdoc/Cargo.toml
@@ -0,0 +1,41 @@
+[package]
+name = "rustdoc"
+version = "0.0.0"
+edition = "2021"
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+arrayvec = { version = "0.7", default-features = false }
+askama = { version = "0.11", default-features = false, features = ["config"] }
+atty = "0.2"
+pulldown-cmark = { version = "0.9.2", default-features = false }
+minifier = "0.2.1"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+smallvec = "1.8.1"
+tempfile = "3"
+itertools = "0.10.1"
+regex = "1"
+rustdoc-json-types = { path = "../rustdoc-json-types" }
+tracing = "0.1"
+tracing-tree = "0.2.0"
+once_cell = "1.10.0"
+
+[dependencies.tracing-subscriber]
+version = "0.3.3"
+default-features = false
+features = ["fmt", "env-filter", "smallvec", "parking_lot", "ansi"]
+
+[target.'cfg(windows)'.dependencies]
+rayon = "1.5.1"
+
+[dev-dependencies]
+expect-test = "1.0"
+
+[features]
+jemalloc = []
+
+[package.metadata.rust-analyzer]
+rustc_private = true
diff --git a/src/librustdoc/README.md b/src/librustdoc/README.md
new file mode 100644
index 000000000..5a5f54706
--- /dev/null
+++ b/src/librustdoc/README.md
@@ -0,0 +1,3 @@
+For more information about how `librustdoc` works, see the [rustc dev guide].
+
+[rustc dev guide]: https://rustc-dev-guide.rust-lang.org/rustdoc.html
diff --git a/src/librustdoc/askama.toml b/src/librustdoc/askama.toml
new file mode 100644
index 000000000..0c984f637
--- /dev/null
+++ b/src/librustdoc/askama.toml
@@ -0,0 +1,2 @@
+[general]
+dirs = ["html/templates"]
diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
new file mode 100644
index 000000000..af33c1a6a
--- /dev/null
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -0,0 +1,742 @@
+use rustc_data_structures::fx::FxHashSet;
+use rustc_hir as hir;
+use rustc_hir::lang_items::LangItem;
+use rustc_middle::ty::{self, Region, RegionVid, TypeFoldable, TypeSuperFoldable};
+use rustc_trait_selection::traits::auto_trait::{self, AutoTraitResult};
+
+use std::fmt::Debug;
+
+use super::*;
+
+#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)]
+enum RegionTarget<'tcx> {
+    Region(Region<'tcx>),
+    RegionVid(RegionVid),
+}
+
+#[derive(Default, Debug, Clone)]
+struct RegionDeps<'tcx> {
+    larger: FxHashSet<RegionTarget<'tcx>>,
+    smaller: FxHashSet<RegionTarget<'tcx>>,
+}
+
+pub(crate) struct AutoTraitFinder<'a, 'tcx> {
+    pub(crate) cx: &'a mut core::DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx>
+where
+    'tcx: 'a, // should be an implied bound; rustc bug #98852.
+{
+    pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> Self {
+        AutoTraitFinder { cx }
+    }
+
+    fn generate_for_trait(
+        &mut self,
+        ty: Ty<'tcx>,
+        trait_def_id: DefId,
+        param_env: ty::ParamEnv<'tcx>,
+        item_def_id: DefId,
+        f: &auto_trait::AutoTraitFinder<'tcx>,
+        // If this is set, show only negative trait implementations, not positive ones.
+        discard_positive_impl: bool,
+    ) -> Option<Item> {
+        let tcx = self.cx.tcx;
+        let trait_ref = ty::TraitRef { def_id: trait_def_id, substs: tcx.mk_substs_trait(ty, &[]) };
+        if !self.cx.generated_synthetics.insert((ty, trait_def_id)) {
+            debug!("get_auto_trait_impl_for({:?}): already generated, aborting", trait_ref);
+            return None;
+        }
+
+        let result = f.find_auto_trait_generics(ty, param_env, trait_def_id, |info| {
+            let region_data = info.region_data;
+
+            let names_map = tcx
+                .generics_of(item_def_id)
+                .params
+                .iter()
+                .filter_map(|param| match param.kind {
+                    ty::GenericParamDefKind::Lifetime => Some(param.name),
+                    _ => None,
+                })
+                .map(|name| (name, Lifetime(name)))
+                .collect();
+            let lifetime_predicates = Self::handle_lifetimes(&region_data, &names_map);
+            let new_generics = self.param_env_to_generics(
+                item_def_id,
+                info.full_user_env,
+                lifetime_predicates,
+                info.vid_to_region,
+            );
+
+            debug!(
+                "find_auto_trait_generics(item_def_id={:?}, trait_def_id={:?}): \
+                    finished with {:?}",
+                item_def_id, trait_def_id, new_generics
+            );
+
+            new_generics
+        });
+
+        let polarity;
+        let new_generics = match result {
+            AutoTraitResult::PositiveImpl(new_generics) => {
+                polarity = ty::ImplPolarity::Positive;
+                if discard_positive_impl {
+                    return None;
+                }
+                new_generics
+            }
+            AutoTraitResult::NegativeImpl => {
+                polarity = ty::ImplPolarity::Negative;
+
+                // For negative impls, we use the generic params, but *not* the predicates,
+                // from the original type. Otherwise, the displayed impl appears to be a
+                // conditional negative impl, when it's really unconditional.
+                //
+                // For example, consider the struct Foo<T: Copy>(*mut T). Using
+                // the original predicates in our impl would cause us to generate
+                // `impl !Send for Foo<T: Copy>`, which makes it appear that Foo
+                // implements Send where T is not copy.
+                //
+                // Instead, we generate `impl !Send for Foo<T>`, which better
+                // expresses the fact that `Foo<T>` never implements `Send`,
+                // regardless of the choice of `T`.
+                let raw_generics = clean_ty_generics(
+                    self.cx,
+                    tcx.generics_of(item_def_id),
+                    ty::GenericPredicates::default(),
+                );
+                let params = raw_generics.params;
+
+                Generics { params, where_predicates: Vec::new() }
+            }
+            AutoTraitResult::ExplicitImpl => return None,
+        };
+
+        Some(Item {
+            name: None,
+            attrs: Default::default(),
+            visibility: Inherited,
+            item_id: ItemId::Auto { trait_: trait_def_id, for_: item_def_id },
+            kind: Box::new(ImplItem(Box::new(Impl {
+                unsafety: hir::Unsafety::Normal,
+                generics: new_generics,
+                trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, &[])),
+                for_: clean_middle_ty(ty, self.cx, None),
+                items: Vec::new(),
+                polarity,
+                kind: ImplKind::Auto,
+            }))),
+            cfg: None,
+        })
+    }
+
+    pub(crate) fn get_auto_trait_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
+        let tcx = self.cx.tcx;
+        let param_env = tcx.param_env(item_def_id);
+        let ty = tcx.type_of(item_def_id);
+        let f = auto_trait::AutoTraitFinder::new(tcx);
+
+        debug!("get_auto_trait_impls({:?})", ty);
+        let auto_traits: Vec<_> = self.cx.auto_traits.iter().copied().collect();
+        let mut auto_traits: Vec<Item> = auto_traits
+            .into_iter()
+            .filter_map(|trait_def_id| {
+                self.generate_for_trait(ty, trait_def_id, param_env, item_def_id, &f, false)
+            })
+            .collect();
+        // We are only interested in case the type *doesn't* implement the Sized trait.
+        if !ty.is_sized(tcx.at(rustc_span::DUMMY_SP), param_env) {
+            // In case `#![no_core]` is used, `sized_trait` returns nothing.
+            if let Some(item) = tcx.lang_items().sized_trait().and_then(|sized_trait_did| {
+                self.generate_for_trait(ty, sized_trait_did, param_env, item_def_id, &f, true)
+            }) {
+                auto_traits.push(item);
+            }
+        }
+        auto_traits
+    }
+
+    fn get_lifetime(region: Region<'_>, names_map: &FxHashMap<Symbol, Lifetime>) -> Lifetime {
+        region_name(region)
+            .map(|name| {
+                names_map.get(&name).unwrap_or_else(|| {
+                    panic!("Missing lifetime with name {:?} for {:?}", name.as_str(), region)
+                })
+            })
+            .unwrap_or(&Lifetime::statik())
+            .clone()
+    }
+
+    /// This method calculates two things: Lifetime constraints of the form `'a: 'b`,
+    /// and region constraints of the form `RegionVid: 'a`
+    ///
+    /// This is essentially a simplified version of lexical_region_resolve. However,
+    /// handle_lifetimes determines what *needs be* true in order for an impl to hold.
+    /// lexical_region_resolve, along with much of the rest of the compiler, is concerned
+    /// with determining if a given set up constraints/predicates *are* met, given some
+    /// starting conditions (e.g., user-provided code). For this reason, it's easier
+    /// to perform the calculations we need on our own, rather than trying to make
+    /// existing inference/solver code do what we want.
+    fn handle_lifetimes<'cx>(
+        regions: &RegionConstraintData<'cx>,
+        names_map: &FxHashMap<Symbol, Lifetime>,
+    ) -> Vec<WherePredicate> {
+        // Our goal is to 'flatten' the list of constraints by eliminating
+        // all intermediate RegionVids. At the end, all constraints should
+        // be between Regions (aka region variables). This gives us the information
+        // we need to create the Generics.
+        let mut finished: FxHashMap<_, Vec<_>> = Default::default();
+
+        let mut vid_map: FxHashMap<RegionTarget<'_>, RegionDeps<'_>> = Default::default();
+
+        // Flattening is done in two parts. First, we insert all of the constraints
+        // into a map. Each RegionTarget (either a RegionVid or a Region) maps
+        // to its smaller and larger regions. Note that 'larger' regions correspond
+        // to sub-regions in Rust code (e.g., in 'a: 'b, 'a is the larger region).
+        for constraint in regions.constraints.keys() {
+            match *constraint {
+                Constraint::VarSubVar(r1, r2) => {
+                    {
+                        let deps1 = vid_map.entry(RegionTarget::RegionVid(r1)).or_default();
+                        deps1.larger.insert(RegionTarget::RegionVid(r2));
+                    }
+
+                    let deps2 = vid_map.entry(RegionTarget::RegionVid(r2)).or_default();
+                    deps2.smaller.insert(RegionTarget::RegionVid(r1));
+                }
+                Constraint::RegSubVar(region, vid) => {
+                    let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_default();
+                    deps.smaller.insert(RegionTarget::Region(region));
+                }
+                Constraint::VarSubReg(vid, region) => {
+                    let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_default();
+                    deps.larger.insert(RegionTarget::Region(region));
+                }
+                Constraint::RegSubReg(r1, r2) => {
+                    // The constraint is already in the form that we want, so we're done with it
+                    // Desired order is 'larger, smaller', so flip then
+                    if region_name(r1) != region_name(r2) {
+                        finished
+                            .entry(region_name(r2).expect("no region_name found"))
+                            .or_default()
+                            .push(r1);
+                    }
+                }
+            }
+        }
+
+        // Here, we 'flatten' the map one element at a time.
+        // All of the element's sub and super regions are connected
+        // to each other. For example, if we have a graph that looks like this:
+        //
+        // (A, B) - C - (D, E)
+        // Where (A, B) are subregions, and (D,E) are super-regions
+        //
+        // then after deleting 'C', the graph will look like this:
+        //  ... - A - (D, E ...)
+        //  ... - B - (D, E, ...)
+        //  (A, B, ...) - D - ...
+        //  (A, B, ...) - E - ...
+        //
+        //  where '...' signifies the existing sub and super regions of an entry
+        //  When two adjacent ty::Regions are encountered, we've computed a final
+        //  constraint, and add it to our list. Since we make sure to never re-add
+        //  deleted items, this process will always finish.
+        while !vid_map.is_empty() {
+            let target = *vid_map.keys().next().expect("Keys somehow empty");
+            let deps = vid_map.remove(&target).expect("Entry somehow missing");
+
+            for smaller in deps.smaller.iter() {
+                for larger in deps.larger.iter() {
+                    match (smaller, larger) {
+                        (&RegionTarget::Region(r1), &RegionTarget::Region(r2)) => {
+                            if region_name(r1) != region_name(r2) {
+                                finished
+                                    .entry(region_name(r2).expect("no region name found"))
+                                    .or_default()
+                                    .push(r1) // Larger, smaller
+                            }
+                        }
+                        (&RegionTarget::RegionVid(_), &RegionTarget::Region(_)) => {
+                            if let Entry::Occupied(v) = vid_map.entry(*smaller) {
+                                let smaller_deps = v.into_mut();
+                                smaller_deps.larger.insert(*larger);
+                                smaller_deps.larger.remove(&target);
+                            }
+                        }
+                        (&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => {
+                            if let Entry::Occupied(v) = vid_map.entry(*larger) {
+                                let deps = v.into_mut();
+                                deps.smaller.insert(*smaller);
+                                deps.smaller.remove(&target);
+                            }
+                        }
+                        (&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => {
+                            if let Entry::Occupied(v) = vid_map.entry(*smaller) {
+                                let smaller_deps = v.into_mut();
+                                smaller_deps.larger.insert(*larger);
+                                smaller_deps.larger.remove(&target);
+                            }
+
+                            if let Entry::Occupied(v) = vid_map.entry(*larger) {
+                                let larger_deps = v.into_mut();
+                                larger_deps.smaller.insert(*smaller);
+                                larger_deps.smaller.remove(&target);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        let lifetime_predicates = names_map
+            .iter()
+            .flat_map(|(name, lifetime)| {
+                let empty = Vec::new();
+                let bounds: FxHashSet<GenericBound> = finished
+                    .get(name)
+                    .unwrap_or(&empty)
+                    .iter()
+                    .map(|region| GenericBound::Outlives(Self::get_lifetime(*region, names_map)))
+                    .collect();
+
+                if bounds.is_empty() {
+                    return None;
+                }
+                Some(WherePredicate::RegionPredicate {
+                    lifetime: lifetime.clone(),
+                    bounds: bounds.into_iter().collect(),
+                })
+            })
+            .collect();
+
+        lifetime_predicates
+    }
+
+    fn extract_for_generics(&self, pred: ty::Predicate<'tcx>) -> FxHashSet<GenericParamDef> {
+        let bound_predicate = pred.kind();
+        let tcx = self.cx.tcx;
+        let regions = match bound_predicate.skip_binder() {
+            ty::PredicateKind::Trait(poly_trait_pred) => {
+                tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred))
+            }
+            ty::PredicateKind::Projection(poly_proj_pred) => {
+                tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_proj_pred))
+            }
+            _ => return FxHashSet::default(),
+        };
+
+        regions
+            .into_iter()
+            .filter_map(|br| {
+                match br {
+                    // We only care about named late bound regions, as we need to add them
+                    // to the 'for<>' section
+                    ty::BrNamed(_, name) => Some(GenericParamDef {
+                        name,
+                        kind: GenericParamDefKind::Lifetime { outlives: vec![] },
+                    }),
+                    _ => None,
+                }
+            })
+            .collect()
+    }
+
+    fn make_final_bounds(
+        &self,
+        ty_to_bounds: FxHashMap<Type, FxHashSet<GenericBound>>,
+        ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)>,
+        lifetime_to_bounds: FxHashMap<Lifetime, FxHashSet<GenericBound>>,
+    ) -> Vec<WherePredicate> {
+        ty_to_bounds
+            .into_iter()
+            .flat_map(|(ty, mut bounds)| {
+                if let Some((ref poly_trait, ref output)) = ty_to_fn.get(&ty) {
+                    let mut new_path = poly_trait.trait_.clone();
+                    let last_segment = new_path.segments.pop().expect("segments were empty");
+
+                    let (old_input, old_output) = match last_segment.args {
+                        GenericArgs::AngleBracketed { args, .. } => {
+                            let types = args
+                                .iter()
+                                .filter_map(|arg| match arg {
+                                    GenericArg::Type(ty) => Some(ty.clone()),
+                                    _ => None,
+                                })
+                                .collect();
+                            (types, None)
+                        }
+                        GenericArgs::Parenthesized { inputs, output } => (inputs, output),
+                    };
+
+                    let output = output.as_ref().cloned().map(Box::new);
+                    if old_output.is_some() && old_output != output {
+                        panic!("Output mismatch for {:?} {:?} {:?}", ty, old_output, output);
+                    }
+
+                    let new_params = GenericArgs::Parenthesized { inputs: old_input, output };
+
+                    new_path
+                        .segments
+                        .push(PathSegment { name: last_segment.name, args: new_params });
+
+                    bounds.insert(GenericBound::TraitBound(
+                        PolyTrait {
+                            trait_: new_path,
+                            generic_params: poly_trait.generic_params.clone(),
+                        },
+                        hir::TraitBoundModifier::None,
+                    ));
+                }
+                if bounds.is_empty() {
+                    return None;
+                }
+
+                let mut bounds_vec = bounds.into_iter().collect();
+                self.sort_where_bounds(&mut bounds_vec);
+
+                Some(WherePredicate::BoundPredicate {
+                    ty,
+                    bounds: bounds_vec,
+                    bound_params: Vec::new(),
+                })
+            })
+            .chain(
+                lifetime_to_bounds.into_iter().filter(|&(_, ref bounds)| !bounds.is_empty()).map(
+                    |(lifetime, bounds)| {
+                        let mut bounds_vec = bounds.into_iter().collect();
+                        self.sort_where_bounds(&mut bounds_vec);
+                        WherePredicate::RegionPredicate { lifetime, bounds: bounds_vec }
+                    },
+                ),
+            )
+            .collect()
+    }
+
+    /// Converts the calculated `ParamEnv` and lifetime information to a [`clean::Generics`](Generics), suitable for
+    /// display on the docs page. Cleaning the `Predicates` produces sub-optimal [`WherePredicate`]s,
+    /// so we fix them up:
+    ///
+    /// * Multiple bounds for the same type are coalesced into one: e.g., `T: Copy`, `T: Debug`
+    /// becomes `T: Copy + Debug`
+    /// * `Fn` bounds are handled specially - instead of leaving it as `T: Fn(), <T as Fn::Output> =
+    /// K`, we use the dedicated syntax `T: Fn() -> K`
+    /// * We explicitly add a `?Sized` bound if we didn't find any `Sized` predicates for a type
+    fn param_env_to_generics(
+        &mut self,
+        item_def_id: DefId,
+        param_env: ty::ParamEnv<'tcx>,
+        mut existing_predicates: Vec<WherePredicate>,
+        vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'tcx>>,
+    ) -> Generics {
+        debug!(
+            "param_env_to_generics(item_def_id={:?}, param_env={:?}, \
+             existing_predicates={:?})",
+            item_def_id, param_env, existing_predicates
+        );
+
+        let tcx = self.cx.tcx;
+
+        // The `Sized` trait must be handled specially, since we only display it when
+        // it is *not* required (i.e., '?Sized')
+        let sized_trait = tcx.require_lang_item(LangItem::Sized, None);
+
+        let mut replacer = RegionReplacer { vid_to_region: &vid_to_region, tcx };
+
+        let orig_bounds: FxHashSet<_> = tcx.param_env(item_def_id).caller_bounds().iter().collect();
+        let clean_where_predicates = param_env
+            .caller_bounds()
+            .iter()
+            .filter(|p| {
+                !orig_bounds.contains(p)
+                    || match p.kind().skip_binder() {
+                        ty::PredicateKind::Trait(pred) => pred.def_id() == sized_trait,
+                        _ => false,
+                    }
+            })
+            .map(|p| p.fold_with(&mut replacer));
+
+        let raw_generics = clean_ty_generics(
+            self.cx,
+            tcx.generics_of(item_def_id),
+            tcx.explicit_predicates_of(item_def_id),
+        );
+        let mut generic_params = raw_generics.params;
+
+        debug!("param_env_to_generics({:?}): generic_params={:?}", item_def_id, generic_params);
+
+        let mut has_sized = FxHashSet::default();
+        let mut ty_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default();
+        let mut lifetime_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default();
+        let mut ty_to_traits: FxHashMap<Type, FxHashSet<Path>> = Default::default();
+
+        let mut ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)> = Default::default();
+
+        for p in clean_where_predicates {
+            let (orig_p, p) = (p, p.clean(self.cx));
+            if p.is_none() {
+                continue;
+            }
+            let p = p.unwrap();
+            match p {
+                WherePredicate::BoundPredicate { ty, mut bounds, .. } => {
+                    // Writing a projection trait bound of the form
+                    // <T as Trait>::Name : ?Sized
+                    // is illegal, because ?Sized bounds can only
+                    // be written in the (here, nonexistent) definition
+                    // of the type.
+                    // Therefore, we make sure that we never add a ?Sized
+                    // bound for projections
+                    if let Type::QPath { .. } = ty {
+                        has_sized.insert(ty.clone());
+                    }
+
+                    if bounds.is_empty() {
+                        continue;
+                    }
+
+                    let mut for_generics = self.extract_for_generics(orig_p);
+
+                    assert!(bounds.len() == 1);
+                    let mut b = bounds.pop().expect("bounds were empty");
+
+                    if b.is_sized_bound(self.cx) {
+                        has_sized.insert(ty.clone());
+                    } else if !b
+                        .get_trait_path()
+                        .and_then(|trait_| {
+                            ty_to_traits
+                                .get(&ty)
+                                .map(|bounds| bounds.contains(&strip_path_generics(trait_)))
+                        })
+                        .unwrap_or(false)
+                    {
+                        // If we've already added a projection bound for the same type, don't add
+                        // this, as it would be a duplicate
+
+                        // Handle any 'Fn/FnOnce/FnMut' bounds specially,
+                        // as we want to combine them with any 'Output' qpaths
+                        // later
+
+                        let is_fn = match b {
+                            GenericBound::TraitBound(ref mut p, _) => {
+                                // Insert regions into the for_generics hash map first, to ensure
+                                // that we don't end up with duplicate bounds (e.g., for<'b, 'b>)
+                                for_generics.extend(p.generic_params.clone());
+                                p.generic_params = for_generics.into_iter().collect();
+                                self.is_fn_trait(&p.trait_)
+                            }
+                            _ => false,
+                        };
+
+                        let poly_trait = b.get_poly_trait().expect("Cannot get poly trait");
+
+                        if is_fn {
+                            ty_to_fn
+                                .entry(ty.clone())
+                                .and_modify(|e| *e = (poly_trait.clone(), e.1.clone()))
+                                .or_insert(((poly_trait.clone()), None));
+
+                            ty_to_bounds.entry(ty.clone()).or_default();
+                        } else {
+                            ty_to_bounds.entry(ty.clone()).or_default().insert(b.clone());
+                        }
+                    }
+                }
+                WherePredicate::RegionPredicate { lifetime, bounds } => {
+                    lifetime_to_bounds.entry(lifetime).or_default().extend(bounds);
+                }
+                WherePredicate::EqPredicate { lhs, rhs } => {
+                    match lhs {
+                        Type::QPath { ref assoc, ref self_type, ref trait_, .. } => {
+                            let ty = &*self_type;
+                            let mut new_trait = trait_.clone();
+
+                            if self.is_fn_trait(trait_) && assoc.name == sym::Output {
+                                ty_to_fn
+                                    .entry(*ty.clone())
+                                    .and_modify(|e| {
+                                        *e = (e.0.clone(), Some(rhs.ty().unwrap().clone()))
+                                    })
+                                    .or_insert((
+                                        PolyTrait {
+                                            trait_: trait_.clone(),
+                                            generic_params: Vec::new(),
+                                        },
+                                        Some(rhs.ty().unwrap().clone()),
+                                    ));
+                                continue;
+                            }
+
+                            let args = &mut new_trait
+                                .segments
+                                .last_mut()
+                                .expect("segments were empty")
+                                .args;
+
+                            match args {
+                                // Convert something like '<T as Iterator::Item> = u8'
+                                // to 'T: Iterator<Item=u8>'
+                                GenericArgs::AngleBracketed { ref mut bindings, .. } => {
+                                    bindings.push(TypeBinding {
+                                        assoc: *assoc.clone(),
+                                        kind: TypeBindingKind::Equality { term: rhs },
+                                    });
+                                }
+                                GenericArgs::Parenthesized { .. } => {
+                                    existing_predicates.push(WherePredicate::EqPredicate {
+                                        lhs: lhs.clone(),
+                                        rhs,
+                                    });
+                                    continue; // If something other than a Fn ends up
+                                    // with parentheses, leave it alone
+                                }
+                            }
+
+                            let bounds = ty_to_bounds.entry(*ty.clone()).or_default();
+
+                            bounds.insert(GenericBound::TraitBound(
+                                PolyTrait { trait_: new_trait, generic_params: Vec::new() },
+                                hir::TraitBoundModifier::None,
+                            ));
+
+                            // Remove any existing 'plain' bound (e.g., 'T: Iterator`) so
+                            // that we don't see a
+                            // duplicate bound like `T: Iterator + Iterator<Item=u8>`
+                            // on the docs page.
+                            bounds.remove(&GenericBound::TraitBound(
+                                PolyTrait { trait_: trait_.clone(), generic_params: Vec::new() },
+                                hir::TraitBoundModifier::None,
+                            ));
+                            // Avoid creating any new duplicate bounds later in the outer
+                            // loop
+                            ty_to_traits.entry(*ty.clone()).or_default().insert(trait_.clone());
+                        }
+                        _ => panic!("Unexpected LHS {:?} for {:?}", lhs, item_def_id),
+                    }
+                }
+            };
+        }
+
+        let final_bounds = self.make_final_bounds(ty_to_bounds, ty_to_fn, lifetime_to_bounds);
+
+        existing_predicates.extend(final_bounds);
+
+        for param in generic_params.iter_mut() {
+            match param.kind {
+                GenericParamDefKind::Type { ref mut default, ref mut bounds, .. } => {
+                    // We never want something like `impl<T=Foo>`.
+                    default.take();
+                    let generic_ty = Type::Generic(param.name);
+                    if !has_sized.contains(&generic_ty) {
+                        bounds.insert(0, GenericBound::maybe_sized(self.cx));
+                    }
+                }
+                GenericParamDefKind::Lifetime { .. } => {}
+                GenericParamDefKind::Const { ref mut default, .. } => {
+                    // We never want something like `impl<const N: usize = 10>`
+                    default.take();
+                }
+            }
+        }
+
+        self.sort_where_predicates(&mut existing_predicates);
+
+        Generics { params: generic_params, where_predicates: existing_predicates }
+    }
+
+    /// Ensure that the predicates are in a consistent order. The precise
+    /// ordering doesn't actually matter, but it's important that
+    /// a given set of predicates always appears in the same order -
+    /// both for visual consistency between 'rustdoc' runs, and to
+    /// make writing tests much easier
+    #[inline]
+    fn sort_where_predicates(&self, predicates: &mut Vec<WherePredicate>) {
+        // We should never have identical bounds - and if we do,
+        // they're visually identical as well. Therefore, using
+        // an unstable sort is fine.
+        self.unstable_debug_sort(predicates);
+    }
+
+    /// Ensure that the bounds are in a consistent order. The precise
+    /// ordering doesn't actually matter, but it's important that
+    /// a given set of bounds always appears in the same order -
+    /// both for visual consistency between 'rustdoc' runs, and to
+    /// make writing tests much easier
+    #[inline]
+    fn sort_where_bounds(&self, bounds: &mut Vec<GenericBound>) {
+        // We should never have identical bounds - and if we do,
+        // they're visually identical as well. Therefore, using
+        // an unstable sort is fine.
+        self.unstable_debug_sort(bounds);
+    }
+
+    /// This might look horrendously hacky, but it's actually not that bad.
+    ///
+    /// For performance reasons, we use several different FxHashMaps
+    /// in the process of computing the final set of where predicates.
+    /// However, the iteration order of a HashMap is completely unspecified.
+    /// In fact, the iteration of an FxHashMap can even vary between platforms,
+    /// since FxHasher has different behavior for 32-bit and 64-bit platforms.
+    ///
+    /// Obviously, it's extremely undesirable for documentation rendering
+    /// to be dependent on the platform it's run on. Apart from being confusing
+    /// to end users, it makes writing tests much more difficult, as predicates
+    /// can appear in any order in the final result.
+    ///
+    /// To solve this problem, we sort WherePredicates and GenericBounds
+    /// by their Debug string. The thing to keep in mind is that we don't really
+    /// care what the final order is - we're synthesizing an impl or bound
+    /// ourselves, so any order can be considered equally valid. By sorting the
+    /// predicates and bounds, however, we ensure that for a given codebase, all
+    /// auto-trait impls always render in exactly the same way.
+    ///
+    /// Using the Debug implementation for sorting prevents us from needing to
+    /// write quite a bit of almost entirely useless code (e.g., how should two
+    /// Types be sorted relative to each other). It also allows us to solve the
+    /// problem for both WherePredicates and GenericBounds at the same time. This
+    /// approach is probably somewhat slower, but the small number of items
+    /// involved (impls rarely have more than a few bounds) means that it
+    /// shouldn't matter in practice.
+    fn unstable_debug_sort<T: Debug>(&self, vec: &mut Vec<T>) {
+        vec.sort_by_cached_key(|x| format!("{:?}", x))
+    }
+
+    fn is_fn_trait(&self, path: &Path) -> bool {
+        let tcx = self.cx.tcx;
+        let did = path.def_id();
+        did == tcx.require_lang_item(LangItem::Fn, None)
+            || did == tcx.require_lang_item(LangItem::FnMut, None)
+            || did == tcx.require_lang_item(LangItem::FnOnce, None)
+    }
+}
+
+fn region_name(region: Region<'_>) -> Option<Symbol> {
+    match *region {
+        ty::ReEarlyBound(r) => Some(r.name),
+        _ => None,
+    }
+}
+
+/// Replaces all [`ty::RegionVid`]s in a type with [`ty::Region`]s, using the provided map.
+struct RegionReplacer<'a, 'tcx> {
+    vid_to_region: &'a FxHashMap<ty::RegionVid, ty::Region<'tcx>>,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl<'a, 'tcx> TypeFolder<'tcx> for RegionReplacer<'a, 'tcx> {
+    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
+        (match *r {
+            ty::ReVar(vid) => self.vid_to_region.get(&vid).cloned(),
+            _ => None,
+        })
+        .unwrap_or_else(|| r.super_fold_with(self))
+    }
+}
diff --git a/src/librustdoc/clean/blanket_impl.rs b/src/librustdoc/clean/blanket_impl.rs
new file mode 100644
index 000000000..01dd95e6e
--- /dev/null
+++ b/src/librustdoc/clean/blanket_impl.rs
@@ -0,0 +1,136 @@
+use crate::rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
+use rustc_hir as hir;
+use rustc_infer::infer::{InferOk, TyCtxtInferExt};
+use rustc_infer::traits;
+use rustc_middle::ty::subst::Subst;
+use rustc_middle::ty::ToPredicate;
+use rustc_span::DUMMY_SP;
+
+use super::*;
+
+pub(crate) struct BlanketImplFinder<'a, 'tcx> {
+    pub(crate) cx: &'a mut core::DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
+    pub(crate) fn get_blanket_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
+        let param_env = self.cx.tcx.param_env(item_def_id);
+        let ty = self.cx.tcx.bound_type_of(item_def_id);
+
+        trace!("get_blanket_impls({:?})", ty);
+        let mut impls = Vec::new();
+        self.cx.with_all_traits(|cx, all_traits| {
+            for &trait_def_id in all_traits {
+                if !cx.cache.access_levels.is_public(trait_def_id)
+                    || cx.generated_synthetics.get(&(ty.0, trait_def_id)).is_some()
+                {
+                    continue;
+                }
+                // NOTE: doesn't use `for_each_relevant_impl` to avoid looking at anything besides blanket impls
+                let trait_impls = cx.tcx.trait_impls_of(trait_def_id);
+                for &impl_def_id in trait_impls.blanket_impls() {
+                    trace!(
+                        "get_blanket_impls: Considering impl for trait '{:?}' {:?}",
+                        trait_def_id,
+                        impl_def_id
+                    );
+                    let trait_ref = cx.tcx.bound_impl_trait_ref(impl_def_id).unwrap();
+                    let is_param = matches!(trait_ref.0.self_ty().kind(), ty::Param(_));
+                    let may_apply = is_param && cx.tcx.infer_ctxt().enter(|infcx| {
+                        let substs = infcx.fresh_substs_for_item(DUMMY_SP, item_def_id);
+                        let ty = ty.subst(infcx.tcx, substs);
+                        let param_env = EarlyBinder(param_env).subst(infcx.tcx, substs);
+
+                        let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+                        let trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
+
+                        // Require the type the impl is implemented on to match
+                        // our type, and ignore the impl if there was a mismatch.
+                        let cause = traits::ObligationCause::dummy();
+                        let eq_result = infcx.at(&cause, param_env).eq(trait_ref.self_ty(), ty);
+                        if let Ok(InferOk { value: (), obligations }) = eq_result {
+                            // FIXME(eddyb) ignoring `obligations` might cause false positives.
+                            drop(obligations);
+
+                            trace!(
+                                "invoking predicate_may_hold: param_env={:?}, trait_ref={:?}, ty={:?}",
+                                param_env,
+                                trait_ref,
+                                ty
+                            );
+                            let predicates = cx
+                                .tcx
+                                .predicates_of(impl_def_id)
+                                .instantiate(cx.tcx, impl_substs)
+                                .predicates
+                                .into_iter()
+                                .chain(Some(
+                                    ty::Binder::dummy(trait_ref)
+                                        .to_poly_trait_predicate()
+                                        .map_bound(ty::PredicateKind::Trait)
+                                        .to_predicate(infcx.tcx),
+                                ));
+                            for predicate in predicates {
+                                debug!("testing predicate {:?}", predicate);
+                                let obligation = traits::Obligation::new(
+                                    traits::ObligationCause::dummy(),
+                                    param_env,
+                                    predicate,
+                                );
+                                match infcx.evaluate_obligation(&obligation) {
+                                    Ok(eval_result) if eval_result.may_apply() => {}
+                                    Err(traits::OverflowError::Canonical) => {}
+                                    Err(traits::OverflowError::ErrorReporting) => {}
+                                    _ => {
+                                        return false;
+                                    }
+                                }
+                            }
+                            true
+                        } else {
+                            false
+                        }
+                    });
+                    debug!(
+                        "get_blanket_impls: found applicable impl: {} for trait_ref={:?}, ty={:?}",
+                        may_apply, trait_ref, ty
+                    );
+                    if !may_apply {
+                        continue;
+                    }
+
+                    cx.generated_synthetics.insert((ty.0, trait_def_id));
+
+                    impls.push(Item {
+                        name: None,
+                        attrs: Default::default(),
+                        visibility: Inherited,
+                        item_id: ItemId::Blanket { impl_id: impl_def_id, for_: item_def_id },
+                        kind: Box::new(ImplItem(Box::new(Impl {
+                            unsafety: hir::Unsafety::Normal,
+                            generics: clean_ty_generics(
+                                cx,
+                                cx.tcx.generics_of(impl_def_id),
+                                cx.tcx.explicit_predicates_of(impl_def_id),
+                            ),
+                            // FIXME(eddyb) compute both `trait_` and `for_` from
+                            // the post-inference `trait_ref`, as it's more accurate.
+                            trait_: Some(clean_trait_ref_with_bindings(cx, trait_ref.0, &[])),
+                            for_: clean_middle_ty(ty.0, cx, None),
+                            items: cx.tcx
+                                .associated_items(impl_def_id)
+                                .in_definition_order()
+                                .map(|x| x.clean(cx))
+                                .collect::<Vec<_>>(),
+                            polarity: ty::ImplPolarity::Positive,
+                            kind: ImplKind::Blanket(Box::new(clean_middle_ty(trait_ref.0.self_ty(), cx, None))),
+                        }))),
+                        cfg: None,
+                    });
+                }
+            }
+        });
+
+        impls
+    }
+}
diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
new file mode 100644
index 000000000..f33f5d27d
--- /dev/null
+++ b/src/librustdoc/clean/cfg.rs
@@ -0,0 +1,588 @@
+//! The representation of a `#[doc(cfg(...))]` attribute.
+
+// FIXME: Once the portability lint RFC is implemented (see tracking issue #41619),
+// switch to use those structures instead.
+
+use std::fmt::{self, Write};
+use std::mem;
+use std::ops;
+
+use rustc_ast::{LitKind, MetaItem, MetaItemKind, NestedMetaItem};
+use rustc_data_structures::fx::FxHashSet;
+use rustc_feature::Features;
+use rustc_session::parse::ParseSess;
+use rustc_span::symbol::{sym, Symbol};
+
+use rustc_span::Span;
+
+use crate::html::escape::Escape;
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub(crate) enum Cfg {
+    /// Accepts all configurations.
+    True,
+    /// Denies all configurations.
+    False,
+    /// A generic configuration option, e.g., `test` or `target_os = "linux"`.
+    Cfg(Symbol, Option<Symbol>),
+    /// Negates a configuration requirement, i.e., `not(x)`.
+    Not(Box<Cfg>),
+    /// Union of a list of configuration requirements, i.e., `any(...)`.
+    Any(Vec<Cfg>),
+    /// Intersection of a list of configuration requirements, i.e., `all(...)`.
+    All(Vec<Cfg>),
+}
+
+#[derive(PartialEq, Debug)]
+pub(crate) struct InvalidCfgError {
+    pub(crate) msg: &'static str,
+    pub(crate) span: Span,
+}
+
+impl Cfg {
+    /// Parses a `NestedMetaItem` into a `Cfg`.
+    fn parse_nested(
+        nested_cfg: &NestedMetaItem,
+        exclude: &FxHashSet<Cfg>,
+    ) -> Result<Option<Cfg>, InvalidCfgError> {
+        match nested_cfg {
+            NestedMetaItem::MetaItem(ref cfg) => Cfg::parse_without(cfg, exclude),
+            NestedMetaItem::Literal(ref lit) => {
+                Err(InvalidCfgError { msg: "unexpected literal", span: lit.span })
+            }
+        }
+    }
+
+    pub(crate) fn parse_without(
+        cfg: &MetaItem,
+        exclude: &FxHashSet<Cfg>,
+    ) -> Result<Option<Cfg>, InvalidCfgError> {
+        let name = match cfg.ident() {
+            Some(ident) => ident.name,
+            None => {
+                return Err(InvalidCfgError {
+                    msg: "expected a single identifier",
+                    span: cfg.span,
+                });
+            }
+        };
+        match cfg.kind {
+            MetaItemKind::Word => {
+                let cfg = Cfg::Cfg(name, None);
+                if exclude.contains(&cfg) { Ok(None) } else { Ok(Some(cfg)) }
+            }
+            MetaItemKind::NameValue(ref lit) => match lit.kind {
+                LitKind::Str(value, _) => {
+                    let cfg = Cfg::Cfg(name, Some(value));
+                    if exclude.contains(&cfg) { Ok(None) } else { Ok(Some(cfg)) }
+                }
+                _ => Err(InvalidCfgError {
+                    // FIXME: if the main #[cfg] syntax decided to support non-string literals,
+                    // this should be changed as well.
+                    msg: "value of cfg option should be a string literal",
+                    span: lit.span,
+                }),
+            },
+            MetaItemKind::List(ref items) => {
+                let orig_len = items.len();
+                let sub_cfgs =
+                    items.iter().filter_map(|i| Cfg::parse_nested(i, exclude).transpose());
+                let ret = match name {
+                    sym::all => sub_cfgs.fold(Ok(Cfg::True), |x, y| Ok(x? & y?)),
+                    sym::any => sub_cfgs.fold(Ok(Cfg::False), |x, y| Ok(x? | y?)),
+                    sym::not => {
+                        if orig_len == 1 {
+                            let mut sub_cfgs = sub_cfgs.collect::<Vec<_>>();
+                            if sub_cfgs.len() == 1 {
+                                Ok(!sub_cfgs.pop().unwrap()?)
+                            } else {
+                                return Ok(None);
+                            }
+                        } else {
+                            Err(InvalidCfgError { msg: "expected 1 cfg-pattern", span: cfg.span })
+                        }
+                    }
+                    _ => Err(InvalidCfgError { msg: "invalid predicate", span: cfg.span }),
+                };
+                match ret {
+                    Ok(c) => Ok(Some(c)),
+                    Err(e) => Err(e),
+                }
+            }
+        }
+    }
+
+    /// Parses a `MetaItem` into a `Cfg`.
+    ///
+    /// The `MetaItem` should be the content of the `#[cfg(...)]`, e.g., `unix` or
+    /// `target_os = "redox"`.
+    ///
+    /// If the content is not properly formatted, it will return an error indicating what and where
+    /// the error is.
+    pub(crate) fn parse(cfg: &MetaItem) -> Result<Cfg, InvalidCfgError> {
+        Self::parse_without(cfg, &FxHashSet::default()).map(|ret| ret.unwrap())
+    }
+
+    /// Checks whether the given configuration can be matched in the current session.
+    ///
+    /// Equivalent to `attr::cfg_matches`.
+    // FIXME: Actually make use of `features`.
+    pub(crate) fn matches(&self, parse_sess: &ParseSess, features: Option<&Features>) -> bool {
+        match *self {
+            Cfg::False => false,
+            Cfg::True => true,
+            Cfg::Not(ref child) => !child.matches(parse_sess, features),
+            Cfg::All(ref sub_cfgs) => {
+                sub_cfgs.iter().all(|sub_cfg| sub_cfg.matches(parse_sess, features))
+            }
+            Cfg::Any(ref sub_cfgs) => {
+                sub_cfgs.iter().any(|sub_cfg| sub_cfg.matches(parse_sess, features))
+            }
+            Cfg::Cfg(name, value) => parse_sess.config.contains(&(name, value)),
+        }
+    }
+
+    /// Whether the configuration consists of just `Cfg` or `Not`.
+    fn is_simple(&self) -> bool {
+        match *self {
+            Cfg::False | Cfg::True | Cfg::Cfg(..) | Cfg::Not(..) => true,
+            Cfg::All(..) | Cfg::Any(..) => false,
+        }
+    }
+
+    /// Whether the configuration consists of just `Cfg`, `Not` or `All`.
+    fn is_all(&self) -> bool {
+        match *self {
+            Cfg::False | Cfg::True | Cfg::Cfg(..) | Cfg::Not(..) | Cfg::All(..) => true,
+            Cfg::Any(..) => false,
+        }
+    }
+
+    /// Renders the configuration for human display, as a short HTML description.
+    pub(crate) fn render_short_html(&self) -> String {
+        let mut msg = Display(self, Format::ShortHtml).to_string();
+        if self.should_capitalize_first_letter() {
+            if let Some(i) = msg.find(|c: char| c.is_ascii_alphanumeric()) {
+                msg[i..i + 1].make_ascii_uppercase();
+            }
+        }
+        msg
+    }
+
+    /// Renders the configuration for long display, as a long HTML description.
+    pub(crate) fn render_long_html(&self) -> String {
+        let on = if self.should_use_with_in_description() { "with" } else { "on" };
+
+        let mut msg =
+            format!("Available {on} <strong>{}</strong>", Display(self, Format::LongHtml));
+        if self.should_append_only_to_description() {
+            msg.push_str(" only");
+        }
+        msg.push('.');
+        msg
+    }
+
+    /// Renders the configuration for long display, as a long plain text description.
+    pub(crate) fn render_long_plain(&self) -> String {
+        let on = if self.should_use_with_in_description() { "with" } else { "on" };
+
+        let mut msg = format!("Available {on} {}", Display(self, Format::LongPlain));
+        if self.should_append_only_to_description() {
+            msg.push_str(" only");
+        }
+        msg
+    }
+
+    fn should_capitalize_first_letter(&self) -> bool {
+        match *self {
+            Cfg::False | Cfg::True | Cfg::Not(..) => true,
+            Cfg::Any(ref sub_cfgs) | Cfg::All(ref sub_cfgs) => {
+                sub_cfgs.first().map(Cfg::should_capitalize_first_letter).unwrap_or(false)
+            }
+            Cfg::Cfg(name, _) => name == sym::debug_assertions || name == sym::target_endian,
+        }
+    }
+
+    fn should_append_only_to_description(&self) -> bool {
+        match *self {
+            Cfg::False | Cfg::True => false,
+            Cfg::Any(..) | Cfg::All(..) | Cfg::Cfg(..) => true,
+            Cfg::Not(box Cfg::Cfg(..)) => true,
+            Cfg::Not(..) => false,
+        }
+    }
+
+    fn should_use_with_in_description(&self) -> bool {
+        matches!(self, Cfg::Cfg(sym::target_feature, _))
+    }
+
+    /// Attempt to simplify this cfg by assuming that `assume` is already known to be true, will
+    /// return `None` if simplification managed to completely eliminate any requirements from this
+    /// `Cfg`.
+    ///
+    /// See `tests::test_simplify_with` for examples.
+    pub(crate) fn simplify_with(&self, assume: &Cfg) -> Option<Cfg> {
+        if self == assume {
+            return None;
+        }
+
+        if let Cfg::All(a) = self {
+            let mut sub_cfgs: Vec<Cfg> = if let Cfg::All(b) = assume {
+                a.iter().filter(|a| !b.contains(a)).cloned().collect()
+            } else {
+                a.iter().filter(|&a| a != assume).cloned().collect()
+            };
+            let len = sub_cfgs.len();
+            return match len {
+                0 => None,
+                1 => sub_cfgs.pop(),
+                _ => Some(Cfg::All(sub_cfgs)),
+            };
+        } else if let Cfg::All(b) = assume {
+            if b.contains(self) {
+                return None;
+            }
+        }
+
+        Some(self.clone())
+    }
+}
+
+impl ops::Not for Cfg {
+    type Output = Cfg;
+    fn not(self) -> Cfg {
+        match self {
+            Cfg::False => Cfg::True,
+            Cfg::True => Cfg::False,
+            Cfg::Not(cfg) => *cfg,
+            s => Cfg::Not(Box::new(s)),
+        }
+    }
+}
+
+impl ops::BitAndAssign for Cfg {
+    fn bitand_assign(&mut self, other: Cfg) {
+        match (self, other) {
+            (&mut Cfg::False, _) | (_, Cfg::True) => {}
+            (s, Cfg::False) => *s = Cfg::False,
+            (s @ &mut Cfg::True, b) => *s = b,
+            (&mut Cfg::All(ref mut a), Cfg::All(ref mut b)) => {
+                for c in b.drain(..) {
+                    if !a.contains(&c) {
+                        a.push(c);
+                    }
+                }
+            }
+            (&mut Cfg::All(ref mut a), ref mut b) => {
+                if !a.contains(b) {
+                    a.push(mem::replace(b, Cfg::True));
+                }
+            }
+            (s, Cfg::All(mut a)) => {
+                let b = mem::replace(s, Cfg::True);
+                if !a.contains(&b) {
+                    a.push(b);
+                }
+                *s = Cfg::All(a);
+            }
+            (s, b) => {
+                if *s != b {
+                    let a = mem::replace(s, Cfg::True);
+                    *s = Cfg::All(vec![a, b]);
+                }
+            }
+        }
+    }
+}
+
+impl ops::BitAnd for Cfg {
+    type Output = Cfg;
+    fn bitand(mut self, other: Cfg) -> Cfg {
+        self &= other;
+        self
+    }
+}
+
+impl ops::BitOrAssign for Cfg {
+    fn bitor_assign(&mut self, other: Cfg) {
+        match (self, other) {
+            (Cfg::True, _) | (_, Cfg::False) | (_, Cfg::True) => {}
+            (s @ &mut Cfg::False, b) => *s = b,
+            (&mut Cfg::Any(ref mut a), Cfg::Any(ref mut b)) => {
+                for c in b.drain(..) {
+                    if !a.contains(&c) {
+                        a.push(c);
+                    }
+                }
+            }
+            (&mut Cfg::Any(ref mut a), ref mut b) => {
+                if !a.contains(b) {
+                    a.push(mem::replace(b, Cfg::True));
+                }
+            }
+            (s, Cfg::Any(mut a)) => {
+                let b = mem::replace(s, Cfg::True);
+                if !a.contains(&b) {
+                    a.push(b);
+                }
+                *s = Cfg::Any(a);
+            }
+            (s, b) => {
+                if *s != b {
+                    let a = mem::replace(s, Cfg::True);
+                    *s = Cfg::Any(vec![a, b]);
+                }
+            }
+        }
+    }
+}
+
+impl ops::BitOr for Cfg {
+    type Output = Cfg;
+    fn bitor(mut self, other: Cfg) -> Cfg {
+        self |= other;
+        self
+    }
+}
+
+#[derive(Clone, Copy)]
+enum Format {
+    LongHtml,
+    LongPlain,
+    ShortHtml,
+}
+
+impl Format {
+    fn is_long(self) -> bool {
+        match self {
+            Format::LongHtml | Format::LongPlain => true,
+            Format::ShortHtml => false,
+        }
+    }
+
+    fn is_html(self) -> bool {
+        match self {
+            Format::LongHtml | Format::ShortHtml => true,
+            Format::LongPlain => false,
+        }
+    }
+}
+
+/// Pretty-print wrapper for a `Cfg`. Also indicates what form of rendering should be used.
+struct Display<'a>(&'a Cfg, Format);
+
+fn write_with_opt_paren<T: fmt::Display>(
+    fmt: &mut fmt::Formatter<'_>,
+    has_paren: bool,
+    obj: T,
+) -> fmt::Result {
+    if has_paren {
+        fmt.write_char('(')?;
+    }
+    obj.fmt(fmt)?;
+    if has_paren {
+        fmt.write_char(')')?;
+    }
+    Ok(())
+}
+
+impl<'a> fmt::Display for Display<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self.0 {
+            Cfg::Not(ref child) => match **child {
+                Cfg::Any(ref sub_cfgs) => {
+                    let separator =
+                        if sub_cfgs.iter().all(Cfg::is_simple) { " nor " } else { ", nor " };
+                    for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
+                        fmt.write_str(if i == 0 { "neither " } else { separator })?;
+                        write_with_opt_paren(fmt, !sub_cfg.is_all(), Display(sub_cfg, self.1))?;
+                    }
+                    Ok(())
+                }
+                ref simple @ Cfg::Cfg(..) => write!(fmt, "non-{}", Display(simple, self.1)),
+                ref c => write!(fmt, "not ({})", Display(c, self.1)),
+            },
+
+            Cfg::Any(ref sub_cfgs) => {
+                let separator = if sub_cfgs.iter().all(Cfg::is_simple) { " or " } else { ", or " };
+
+                let short_longhand = self.1.is_long() && {
+                    let all_crate_features = sub_cfgs
+                        .iter()
+                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::feature, Some(_))));
+                    let all_target_features = sub_cfgs
+                        .iter()
+                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::target_feature, Some(_))));
+
+                    if all_crate_features {
+                        fmt.write_str("crate features ")?;
+                        true
+                    } else if all_target_features {
+                        fmt.write_str("target features ")?;
+                        true
+                    } else {
+                        false
+                    }
+                };
+
+                for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
+                    if i != 0 {
+                        fmt.write_str(separator)?;
+                    }
+                    if let (true, Cfg::Cfg(_, Some(feat))) = (short_longhand, sub_cfg) {
+                        if self.1.is_html() {
+                            write!(fmt, "<code>{}</code>", feat)?;
+                        } else {
+                            write!(fmt, "`{}`", feat)?;
+                        }
+                    } else {
+                        write_with_opt_paren(fmt, !sub_cfg.is_all(), Display(sub_cfg, self.1))?;
+                    }
+                }
+                Ok(())
+            }
+
+            Cfg::All(ref sub_cfgs) => {
+                let short_longhand = self.1.is_long() && {
+                    let all_crate_features = sub_cfgs
+                        .iter()
+                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::feature, Some(_))));
+                    let all_target_features = sub_cfgs
+                        .iter()
+                        .all(|sub_cfg| matches!(sub_cfg, Cfg::Cfg(sym::target_feature, Some(_))));
+
+                    if all_crate_features {
+                        fmt.write_str("crate features ")?;
+                        true
+                    } else if all_target_features {
+                        fmt.write_str("target features ")?;
+                        true
+                    } else {
+                        false
+                    }
+                };
+
+                for (i, sub_cfg) in sub_cfgs.iter().enumerate() {
+                    if i != 0 {
+                        fmt.write_str(" and ")?;
+                    }
+                    if let (true, Cfg::Cfg(_, Some(feat))) = (short_longhand, sub_cfg) {
+                        if self.1.is_html() {
+                            write!(fmt, "<code>{}</code>", feat)?;
+                        } else {
+                            write!(fmt, "`{}`", feat)?;
+                        }
+                    } else {
+                        write_with_opt_paren(fmt, !sub_cfg.is_simple(), Display(sub_cfg, self.1))?;
+                    }
+                }
+                Ok(())
+            }
+
+            Cfg::True => fmt.write_str("everywhere"),
+            Cfg::False => fmt.write_str("nowhere"),
+
+            Cfg::Cfg(name, value) => {
+                let human_readable = match (name, value) {
+                    (sym::unix, None) => "Unix",
+                    (sym::windows, None) => "Windows",
+                    (sym::debug_assertions, None) => "debug-assertions enabled",
+                    (sym::target_os, Some(os)) => match os.as_str() {
+                        "android" => "Android",
+                        "dragonfly" => "DragonFly BSD",
+                        "emscripten" => "Emscripten",
+                        "freebsd" => "FreeBSD",
+                        "fuchsia" => "Fuchsia",
+                        "haiku" => "Haiku",
+                        "hermit" => "HermitCore",
+                        "illumos" => "illumos",
+                        "ios" => "iOS",
+                        "l4re" => "L4Re",
+                        "linux" => "Linux",
+                        "macos" => "macOS",
+                        "netbsd" => "NetBSD",
+                        "openbsd" => "OpenBSD",
+                        "redox" => "Redox",
+                        "solaris" => "Solaris",
+                        "wasi" => "WASI",
+                        "windows" => "Windows",
+                        _ => "",
+                    },
+                    (sym::target_arch, Some(arch)) => match arch.as_str() {
+                        "aarch64" => "AArch64",
+                        "arm" => "ARM",
+                        "asmjs" => "JavaScript",
+                        "m68k" => "M68k",
+                        "mips" => "MIPS",
+                        "mips64" => "MIPS-64",
+                        "msp430" => "MSP430",
+                        "powerpc" => "PowerPC",
+                        "powerpc64" => "PowerPC-64",
+                        "riscv32" => "RISC-V RV32",
+                        "riscv64" => "RISC-V RV64",
+                        "s390x" => "s390x",
+                        "sparc64" => "SPARC64",
+                        "wasm32" | "wasm64" => "WebAssembly",
+                        "x86" => "x86",
+                        "x86_64" => "x86-64",
+                        _ => "",
+                    },
+                    (sym::target_vendor, Some(vendor)) => match vendor.as_str() {
+                        "apple" => "Apple",
+                        "pc" => "PC",
+                        "sun" => "Sun",
+                        "fortanix" => "Fortanix",
+                        _ => "",
+                    },
+                    (sym::target_env, Some(env)) => match env.as_str() {
+                        "gnu" => "GNU",
+                        "msvc" => "MSVC",
+                        "musl" => "musl",
+                        "newlib" => "Newlib",
+                        "uclibc" => "uClibc",
+                        "sgx" => "SGX",
+                        _ => "",
+                    },
+                    (sym::target_endian, Some(endian)) => return write!(fmt, "{}-endian", endian),
+                    (sym::target_pointer_width, Some(bits)) => return write!(fmt, "{}-bit", bits),
+                    (sym::target_feature, Some(feat)) => match self.1 {
+                        Format::LongHtml => {
+                            return write!(fmt, "target feature <code>{}</code>", feat);
+                        }
+                        Format::LongPlain => return write!(fmt, "target feature `{}`", feat),
+                        Format::ShortHtml => return write!(fmt, "<code>{}</code>", feat),
+                    },
+                    (sym::feature, Some(feat)) => match self.1 {
+                        Format::LongHtml => {
+                            return write!(fmt, "crate feature <code>{}</code>", feat);
+                        }
+                        Format::LongPlain => return write!(fmt, "crate feature `{}`", feat),
+                        Format::ShortHtml => return write!(fmt, "<code>{}</code>", feat),
+                    },
+                    _ => "",
+                };
+                if !human_readable.is_empty() {
+                    fmt.write_str(human_readable)
+                } else if let Some(v) = value {
+                    if self.1.is_html() {
+                        write!(
+                            fmt,
+                            r#"<code>{}="{}"</code>"#,
+                            Escape(name.as_str()),
+                            Escape(v.as_str())
+                        )
+                    } else {
+                        write!(fmt, r#"`{}="{}"`"#, name, v)
+                    }
+                } else if self.1.is_html() {
+                    write!(fmt, "<code>{}</code>", Escape(name.as_str()))
+                } else {
+                    write!(fmt, "`{}`", name)
+                }
+            }
+        }
+    }
+}
diff --git a/src/librustdoc/clean/cfg/tests.rs b/src/librustdoc/clean/cfg/tests.rs
new file mode 100644
index 000000000..7f72d5d39
--- /dev/null
+++ b/src/librustdoc/clean/cfg/tests.rs
@@ -0,0 +1,467 @@
+use super::*;
+
+use rustc_ast::attr;
+use rustc_ast::Path;
+use rustc_span::create_default_session_globals_then;
+use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::DUMMY_SP;
+
+fn word_cfg(s: &str) -> Cfg {
+    Cfg::Cfg(Symbol::intern(s), None)
+}
+
+fn name_value_cfg(name: &str, value: &str) -> Cfg {
+    Cfg::Cfg(Symbol::intern(name), Some(Symbol::intern(value)))
+}
+
+fn dummy_meta_item_word(name: &str) -> MetaItem {
+    MetaItem {
+        path: Path::from_ident(Ident::from_str(name)),
+        kind: MetaItemKind::Word,
+        span: DUMMY_SP,
+    }
+}
+
+macro_rules! dummy_meta_item_list {
+    ($name:ident, [$($list:ident),* $(,)?]) => {
+        MetaItem {
+            path: Path::from_ident(Ident::from_str(stringify!($name))),
+            kind: MetaItemKind::List(vec![
+                $(
+                    NestedMetaItem::MetaItem(
+                        dummy_meta_item_word(stringify!($list)),
+                    ),
+                )*
+            ]),
+            span: DUMMY_SP,
+        }
+    };
+
+    ($name:ident, [$($list:expr),* $(,)?]) => {
+        MetaItem {
+            path: Path::from_ident(Ident::from_str(stringify!($name))),
+            kind: MetaItemKind::List(vec![
+                $(
+                    NestedMetaItem::MetaItem($list),
+                )*
+            ]),
+            span: DUMMY_SP,
+        }
+    };
+}
+
+#[test]
+fn test_cfg_not() {
+    create_default_session_globals_then(|| {
+        assert_eq!(!Cfg::False, Cfg::True);
+        assert_eq!(!Cfg::True, Cfg::False);
+        assert_eq!(!word_cfg("test"), Cfg::Not(Box::new(word_cfg("test"))));
+        assert_eq!(
+            !Cfg::All(vec![word_cfg("a"), word_cfg("b")]),
+            Cfg::Not(Box::new(Cfg::All(vec![word_cfg("a"), word_cfg("b")])))
+        );
+        assert_eq!(
+            !Cfg::Any(vec![word_cfg("a"), word_cfg("b")]),
+            Cfg::Not(Box::new(Cfg::Any(vec![word_cfg("a"), word_cfg("b")])))
+        );
+        assert_eq!(!Cfg::Not(Box::new(word_cfg("test"))), word_cfg("test"));
+    })
+}
+
+#[test]
+fn test_cfg_and() {
+    create_default_session_globals_then(|| {
+        let mut x = Cfg::False;
+        x &= Cfg::True;
+        assert_eq!(x, Cfg::False);
+
+        x = word_cfg("test");
+        x &= Cfg::False;
+        assert_eq!(x, Cfg::False);
+
+        x = word_cfg("test2");
+        x &= Cfg::True;
+        assert_eq!(x, word_cfg("test2"));
+
+        x = Cfg::True;
+        x &= word_cfg("test3");
+        assert_eq!(x, word_cfg("test3"));
+
+        x &= word_cfg("test3");
+        assert_eq!(x, word_cfg("test3"));
+
+        x &= word_cfg("test4");
+        assert_eq!(x, Cfg::All(vec![word_cfg("test3"), word_cfg("test4")]));
+
+        x &= word_cfg("test4");
+        assert_eq!(x, Cfg::All(vec![word_cfg("test3"), word_cfg("test4")]));
+
+        x &= word_cfg("test5");
+        assert_eq!(x, Cfg::All(vec![word_cfg("test3"), word_cfg("test4"), word_cfg("test5")]));
+
+        x &= Cfg::All(vec![word_cfg("test6"), word_cfg("test7")]);
+        assert_eq!(
+            x,
+            Cfg::All(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+            ])
+        );
+
+        x &= Cfg::All(vec![word_cfg("test6"), word_cfg("test7")]);
+        assert_eq!(
+            x,
+            Cfg::All(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+            ])
+        );
+
+        let mut y = Cfg::Any(vec![word_cfg("a"), word_cfg("b")]);
+        y &= x;
+        assert_eq!(
+            y,
+            Cfg::All(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+                Cfg::Any(vec![word_cfg("a"), word_cfg("b")]),
+            ])
+        );
+
+        let mut z = word_cfg("test8");
+        z &= Cfg::All(vec![word_cfg("test9"), word_cfg("test10")]);
+        assert_eq!(z, Cfg::All(vec![word_cfg("test9"), word_cfg("test10"), word_cfg("test8")]));
+
+        let mut z = word_cfg("test11");
+        z &= Cfg::All(vec![word_cfg("test11"), word_cfg("test12")]);
+        assert_eq!(z, Cfg::All(vec![word_cfg("test11"), word_cfg("test12")]));
+
+        assert_eq!(
+            word_cfg("a") & word_cfg("b") & word_cfg("c"),
+            Cfg::All(vec![word_cfg("a"), word_cfg("b"), word_cfg("c")])
+        );
+    })
+}
+
+#[test]
+fn test_cfg_or() {
+    create_default_session_globals_then(|| {
+        let mut x = Cfg::True;
+        x |= Cfg::False;
+        assert_eq!(x, Cfg::True);
+
+        x = word_cfg("test");
+        x |= Cfg::True;
+        assert_eq!(x, word_cfg("test"));
+
+        x = word_cfg("test2");
+        x |= Cfg::False;
+        assert_eq!(x, word_cfg("test2"));
+
+        x = Cfg::False;
+        x |= word_cfg("test3");
+        assert_eq!(x, word_cfg("test3"));
+
+        x |= word_cfg("test3");
+        assert_eq!(x, word_cfg("test3"));
+
+        x |= word_cfg("test4");
+        assert_eq!(x, Cfg::Any(vec![word_cfg("test3"), word_cfg("test4")]));
+
+        x |= word_cfg("test4");
+        assert_eq!(x, Cfg::Any(vec![word_cfg("test3"), word_cfg("test4")]));
+
+        x |= word_cfg("test5");
+        assert_eq!(x, Cfg::Any(vec![word_cfg("test3"), word_cfg("test4"), word_cfg("test5")]));
+
+        x |= Cfg::Any(vec![word_cfg("test6"), word_cfg("test7")]);
+        assert_eq!(
+            x,
+            Cfg::Any(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+            ])
+        );
+
+        x |= Cfg::Any(vec![word_cfg("test6"), word_cfg("test7")]);
+        assert_eq!(
+            x,
+            Cfg::Any(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+            ])
+        );
+
+        let mut y = Cfg::All(vec![word_cfg("a"), word_cfg("b")]);
+        y |= x;
+        assert_eq!(
+            y,
+            Cfg::Any(vec![
+                word_cfg("test3"),
+                word_cfg("test4"),
+                word_cfg("test5"),
+                word_cfg("test6"),
+                word_cfg("test7"),
+                Cfg::All(vec![word_cfg("a"), word_cfg("b")]),
+            ])
+        );
+
+        let mut z = word_cfg("test8");
+        z |= Cfg::Any(vec![word_cfg("test9"), word_cfg("test10")]);
+        assert_eq!(z, Cfg::Any(vec![word_cfg("test9"), word_cfg("test10"), word_cfg("test8")]));
+
+        let mut z = word_cfg("test11");
+        z |= Cfg::Any(vec![word_cfg("test11"), word_cfg("test12")]);
+        assert_eq!(z, Cfg::Any(vec![word_cfg("test11"), word_cfg("test12")]));
+
+        assert_eq!(
+            word_cfg("a") | word_cfg("b") | word_cfg("c"),
+            Cfg::Any(vec![word_cfg("a"), word_cfg("b"), word_cfg("c")])
+        );
+    })
+}
+
+#[test]
+fn test_parse_ok() {
+    create_default_session_globals_then(|| {
+        let mi = dummy_meta_item_word("all");
+        assert_eq!(Cfg::parse(&mi), Ok(word_cfg("all")));
+
+        let mi =
+            attr::mk_name_value_item_str(Ident::from_str("all"), Symbol::intern("done"), DUMMY_SP);
+        assert_eq!(Cfg::parse(&mi), Ok(name_value_cfg("all", "done")));
+
+        let mi = dummy_meta_item_list!(all, [a, b]);
+        assert_eq!(Cfg::parse(&mi), Ok(word_cfg("a") & word_cfg("b")));
+
+        let mi = dummy_meta_item_list!(any, [a, b]);
+        assert_eq!(Cfg::parse(&mi), Ok(word_cfg("a") | word_cfg("b")));
+
+        let mi = dummy_meta_item_list!(not, [a]);
+        assert_eq!(Cfg::parse(&mi), Ok(!word_cfg("a")));
+
+        let mi = dummy_meta_item_list!(
+            not,
+            [dummy_meta_item_list!(
+                any,
+                [dummy_meta_item_word("a"), dummy_meta_item_list!(all, [b, c]),]
+            ),]
+        );
+        assert_eq!(Cfg::parse(&mi), Ok(!(word_cfg("a") | (word_cfg("b") & word_cfg("c")))));
+
+        let mi = dummy_meta_item_list!(all, [a, b, c]);
+        assert_eq!(Cfg::parse(&mi), Ok(word_cfg("a") & word_cfg("b") & word_cfg("c")));
+    })
+}
+
+#[test]
+fn test_parse_err() {
+    create_default_session_globals_then(|| {
+        let mi = attr::mk_name_value_item(Ident::from_str("foo"), LitKind::Bool(false), DUMMY_SP);
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(not, [a, b]);
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(not, []);
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(foo, []);
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(
+            all,
+            [dummy_meta_item_list!(foo, []), dummy_meta_item_word("b"),]
+        );
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(
+            any,
+            [dummy_meta_item_word("a"), dummy_meta_item_list!(foo, []),]
+        );
+        assert!(Cfg::parse(&mi).is_err());
+
+        let mi = dummy_meta_item_list!(not, [dummy_meta_item_list!(foo, []),]);
+        assert!(Cfg::parse(&mi).is_err());
+    })
+}
+
+#[test]
+fn test_render_short_html() {
+    create_default_session_globals_then(|| {
+        assert_eq!(word_cfg("unix").render_short_html(), "Unix");
+        assert_eq!(name_value_cfg("target_os", "macos").render_short_html(), "macOS");
+        assert_eq!(name_value_cfg("target_pointer_width", "16").render_short_html(), "16-bit");
+        assert_eq!(name_value_cfg("target_endian", "little").render_short_html(), "Little-endian");
+        assert_eq!((!word_cfg("windows")).render_short_html(), "Non-Windows");
+        assert_eq!(
+            (word_cfg("unix") & word_cfg("windows")).render_short_html(),
+            "Unix and Windows"
+        );
+        assert_eq!((word_cfg("unix") | word_cfg("windows")).render_short_html(), "Unix or Windows");
+        assert_eq!(
+            (word_cfg("unix") & word_cfg("windows") & word_cfg("debug_assertions"))
+                .render_short_html(),
+            "Unix and Windows and debug-assertions enabled"
+        );
+        assert_eq!(
+            (word_cfg("unix") | word_cfg("windows") | word_cfg("debug_assertions"))
+                .render_short_html(),
+            "Unix or Windows or debug-assertions enabled"
+        );
+        assert_eq!(
+            (!(word_cfg("unix") | word_cfg("windows") | word_cfg("debug_assertions")))
+                .render_short_html(),
+            "Neither Unix nor Windows nor debug-assertions enabled"
+        );
+        assert_eq!(
+            ((word_cfg("unix") & name_value_cfg("target_arch", "x86_64"))
+                | (word_cfg("windows") & name_value_cfg("target_pointer_width", "64")))
+            .render_short_html(),
+            "Unix and x86-64, or Windows and 64-bit"
+        );
+        assert_eq!(
+            (!(word_cfg("unix") & word_cfg("windows"))).render_short_html(),
+            "Not (Unix and Windows)"
+        );
+        assert_eq!(
+            ((word_cfg("debug_assertions") | word_cfg("windows")) & word_cfg("unix"))
+                .render_short_html(),
+            "(Debug-assertions enabled or Windows) and Unix"
+        );
+        assert_eq!(
+            name_value_cfg("target_feature", "sse2").render_short_html(),
+            "<code>sse2</code>"
+        );
+        assert_eq!(
+            (name_value_cfg("target_arch", "x86_64") & name_value_cfg("target_feature", "sse2"))
+                .render_short_html(),
+            "x86-64 and <code>sse2</code>"
+        );
+    })
+}
+
+#[test]
+fn test_render_long_html() {
+    create_default_session_globals_then(|| {
+        assert_eq!(word_cfg("unix").render_long_html(), "Available on <strong>Unix</strong> only.");
+        assert_eq!(
+            name_value_cfg("target_os", "macos").render_long_html(),
+            "Available on <strong>macOS</strong> only."
+        );
+        assert_eq!(
+            name_value_cfg("target_os", "wasi").render_long_html(),
+            "Available on <strong>WASI</strong> only."
+        );
+        assert_eq!(
+            name_value_cfg("target_pointer_width", "16").render_long_html(),
+            "Available on <strong>16-bit</strong> only."
+        );
+        assert_eq!(
+            name_value_cfg("target_endian", "little").render_long_html(),
+            "Available on <strong>little-endian</strong> only."
+        );
+        assert_eq!(
+            (!word_cfg("windows")).render_long_html(),
+            "Available on <strong>non-Windows</strong> only."
+        );
+        assert_eq!(
+            (word_cfg("unix") & word_cfg("windows")).render_long_html(),
+            "Available on <strong>Unix and Windows</strong> only."
+        );
+        assert_eq!(
+            (word_cfg("unix") | word_cfg("windows")).render_long_html(),
+            "Available on <strong>Unix or Windows</strong> only."
+        );
+        assert_eq!(
+            (word_cfg("unix") & word_cfg("windows") & word_cfg("debug_assertions"))
+                .render_long_html(),
+            "Available on <strong>Unix and Windows and debug-assertions enabled</strong> only."
+        );
+        assert_eq!(
+            (word_cfg("unix") | word_cfg("windows") | word_cfg("debug_assertions"))
+                .render_long_html(),
+            "Available on <strong>Unix or Windows or debug-assertions enabled</strong> only."
+        );
+        assert_eq!(
+            (!(word_cfg("unix") | word_cfg("windows") | word_cfg("debug_assertions")))
+                .render_long_html(),
+            "Available on <strong>neither Unix nor Windows nor debug-assertions enabled</strong>."
+        );
+        assert_eq!(
+            ((word_cfg("unix") & name_value_cfg("target_arch", "x86_64"))
+                | (word_cfg("windows") & name_value_cfg("target_pointer_width", "64")))
+            .render_long_html(),
+            "Available on <strong>Unix and x86-64, or Windows and 64-bit</strong> only."
+        );
+        assert_eq!(
+            (!(word_cfg("unix") & word_cfg("windows"))).render_long_html(),
+            "Available on <strong>not (Unix and Windows)</strong>."
+        );
+        assert_eq!(
+            ((word_cfg("debug_assertions") | word_cfg("windows")) & word_cfg("unix"))
+                .render_long_html(),
+            "Available on <strong>(debug-assertions enabled or Windows) and Unix</strong> only."
+        );
+        assert_eq!(
+            name_value_cfg("target_feature", "sse2").render_long_html(),
+            "Available with <strong>target feature <code>sse2</code></strong> only."
+        );
+        assert_eq!(
+            (name_value_cfg("target_arch", "x86_64") & name_value_cfg("target_feature", "sse2"))
+                .render_long_html(),
+            "Available on <strong>x86-64 and target feature <code>sse2</code></strong> only."
+        );
+    })
+}
+
+#[test]
+fn test_simplify_with() {
+    // This is a tiny subset of things that could be simplified, but it likely covers 90% of
+    // real world usecases well.
+    create_default_session_globals_then(|| {
+        let foo = word_cfg("foo");
+        let bar = word_cfg("bar");
+        let baz = word_cfg("baz");
+        let quux = word_cfg("quux");
+
+        let foobar = Cfg::All(vec![foo.clone(), bar.clone()]);
+        let barbaz = Cfg::All(vec![bar.clone(), baz.clone()]);
+        let foobarbaz = Cfg::All(vec![foo.clone(), bar.clone(), baz.clone()]);
+        let bazquux = Cfg::All(vec![baz.clone(), quux.clone()]);
+
+        // Unrelated cfgs don't affect each other
+        assert_eq!(foo.simplify_with(&bar).as_ref(), Some(&foo));
+        assert_eq!(foobar.simplify_with(&bazquux).as_ref(), Some(&foobar));
+
+        // Identical cfgs are eliminated
+        assert_eq!(foo.simplify_with(&foo), None);
+        assert_eq!(foobar.simplify_with(&foobar), None);
+
+        // Multiple cfgs eliminate a single assumed cfg
+        assert_eq!(foobar.simplify_with(&foo).as_ref(), Some(&bar));
+        assert_eq!(foobar.simplify_with(&bar).as_ref(), Some(&foo));
+
+        // A single cfg is eliminated by multiple assumed cfg containing it
+        assert_eq!(foo.simplify_with(&foobar), None);
+
+        // Multiple cfgs eliminate the matching subset of multiple assumed cfg
+        assert_eq!(foobar.simplify_with(&barbaz).as_ref(), Some(&foo));
+        assert_eq!(foobar.simplify_with(&foobarbaz), None);
+    });
+}
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
new file mode 100644
index 000000000..58d0aedb0
--- /dev/null
+++ b/src/librustdoc/clean/inline.rs
@@ -0,0 +1,727 @@
+//! Support for inlining external documentation into the current AST.
+
+use std::iter::once;
+use std::sync::Arc;
+
+use rustc_ast as ast;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::thin_vec::ThinVec;
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::Mutability;
+use rustc_metadata::creader::{CStore, LoadedMacro};
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_span::hygiene::MacroKind;
+use rustc_span::symbol::{kw, sym, Symbol};
+
+use crate::clean::{
+    self, clean_fn_decl_from_did_and_sig, clean_middle_field, clean_middle_ty,
+    clean_trait_ref_with_bindings, clean_ty, clean_ty_generics, clean_variant_def,
+    clean_visibility, utils, Attributes, AttributesExt, Clean, ImplKind, ItemId, Type, Visibility,
+};
+use crate::core::DocContext;
+use crate::formats::item_type::ItemType;
+
+type Attrs<'hir> = &'hir [ast::Attribute];
+
+/// Attempt to inline a definition into this AST.
+///
+/// This function will fetch the definition specified, and if it is
+/// from another crate it will attempt to inline the documentation
+/// from the other crate into this crate.
+///
+/// This is primarily used for `pub use` statements which are, in general,
+/// implementation details. Inlining the documentation should help provide a
+/// better experience when reading the documentation in this use case.
+///
+/// The returned value is `None` if the definition could not be inlined,
+/// and `Some` of a vector of items if it was successfully expanded.
+///
+/// `parent_module` refers to the parent of the *re-export*, not the original item.
+pub(crate) fn try_inline(
+    cx: &mut DocContext<'_>,
+    parent_module: DefId,
+    import_def_id: Option<DefId>,
+    res: Res,
+    name: Symbol,
+    attrs: Option<Attrs<'_>>,
+    visited: &mut FxHashSet<DefId>,
+) -> Option<Vec<clean::Item>> {
+    let did = res.opt_def_id()?;
+    if did.is_local() {
+        return None;
+    }
+    let mut ret = Vec::new();
+
+    debug!("attrs={:?}", attrs);
+    let attrs_clone = attrs;
+
+    let kind = match res {
+        Res::Def(DefKind::Trait, did) => {
+            record_extern_fqn(cx, did, ItemType::Trait);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::TraitItem(build_external_trait(cx, did))
+        }
+        Res::Def(DefKind::Fn, did) => {
+            record_extern_fqn(cx, did, ItemType::Function);
+            clean::FunctionItem(build_external_function(cx, did))
+        }
+        Res::Def(DefKind::Struct, did) => {
+            record_extern_fqn(cx, did, ItemType::Struct);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::StructItem(build_struct(cx, did))
+        }
+        Res::Def(DefKind::Union, did) => {
+            record_extern_fqn(cx, did, ItemType::Union);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::UnionItem(build_union(cx, did))
+        }
+        Res::Def(DefKind::TyAlias, did) => {
+            record_extern_fqn(cx, did, ItemType::Typedef);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::TypedefItem(build_type_alias(cx, did))
+        }
+        Res::Def(DefKind::Enum, did) => {
+            record_extern_fqn(cx, did, ItemType::Enum);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::EnumItem(build_enum(cx, did))
+        }
+        Res::Def(DefKind::ForeignTy, did) => {
+            record_extern_fqn(cx, did, ItemType::ForeignType);
+            build_impls(cx, Some(parent_module), did, attrs, &mut ret);
+            clean::ForeignTypeItem
+        }
+        // Never inline enum variants but leave them shown as re-exports.
+        Res::Def(DefKind::Variant, _) => return None,
+        // Assume that enum variants and struct types are re-exported next to
+        // their constructors.
+        Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) => return Some(Vec::new()),
+        Res::Def(DefKind::Mod, did) => {
+            record_extern_fqn(cx, did, ItemType::Module);
+            clean::ModuleItem(build_module(cx, did, visited))
+        }
+        Res::Def(DefKind::Static(_), did) => {
+            record_extern_fqn(cx, did, ItemType::Static);
+            clean::StaticItem(build_static(cx, did, cx.tcx.is_mutable_static(did)))
+        }
+        Res::Def(DefKind::Const, did) => {
+            record_extern_fqn(cx, did, ItemType::Constant);
+            clean::ConstantItem(build_const(cx, did))
+        }
+        Res::Def(DefKind::Macro(kind), did) => {
+            let mac = build_macro(cx, did, name, import_def_id);
+
+            let type_kind = match kind {
+                MacroKind::Bang => ItemType::Macro,
+                MacroKind::Attr => ItemType::ProcAttribute,
+                MacroKind::Derive => ItemType::ProcDerive,
+            };
+            record_extern_fqn(cx, did, type_kind);
+            mac
+        }
+        _ => return None,
+    };
+
+    let (attrs, cfg) = merge_attrs(cx, Some(parent_module), load_attrs(cx, did), attrs_clone);
+    cx.inlined.insert(did.into());
+    let mut item = clean::Item::from_def_id_and_attrs_and_parts(
+        did,
+        Some(name),
+        kind,
+        Box::new(attrs),
+        cx,
+        cfg,
+    );
+    if let Some(import_def_id) = import_def_id {
+        // The visibility needs to reflect the one from the reexport and not from the "source" DefId.
+        item.visibility = clean_visibility(cx.tcx.visibility(import_def_id));
+    }
+    ret.push(item);
+    Some(ret)
+}
+
+pub(crate) fn try_inline_glob(
+    cx: &mut DocContext<'_>,
+    res: Res,
+    visited: &mut FxHashSet<DefId>,
+    inlined_names: &mut FxHashSet<(ItemType, Symbol)>,
+) -> Option<Vec<clean::Item>> {
+    let did = res.opt_def_id()?;
+    if did.is_local() {
+        return None;
+    }
+
+    match res {
+        Res::Def(DefKind::Mod, did) => {
+            let mut items = build_module_items(cx, did, visited, inlined_names);
+            items.drain_filter(|item| {
+                if let Some(name) = item.name {
+                    // If an item with the same type and name already exists,
+                    // it takes priority over the inlined stuff.
+                    !inlined_names.insert((item.type_(), name))
+                } else {
+                    false
+                }
+            });
+            Some(items)
+        }
+        // glob imports on things like enums aren't inlined even for local exports, so just bail
+        _ => None,
+    }
+}
+
+pub(crate) fn load_attrs<'hir>(cx: &DocContext<'hir>, did: DefId) -> Attrs<'hir> {
+    cx.tcx.get_attrs_unchecked(did)
+}
+
+/// Record an external fully qualified name in the external_paths cache.
+///
+/// These names are used later on by HTML rendering to generate things like
+/// source links back to the original item.
+pub(crate) fn record_extern_fqn(cx: &mut DocContext<'_>, did: DefId, kind: ItemType) {
+    let crate_name = cx.tcx.crate_name(did.krate);
+
+    let relative =
+        cx.tcx.def_path(did).data.into_iter().filter_map(|elem| elem.data.get_opt_name());
+    let fqn = if let ItemType::Macro = kind {
+        // Check to see if it is a macro 2.0 or built-in macro
+        if matches!(
+            CStore::from_tcx(cx.tcx).load_macro_untracked(did, cx.sess()),
+            LoadedMacro::MacroDef(def, _)
+                if matches!(&def.kind, ast::ItemKind::MacroDef(ast_def)
+                    if !ast_def.macro_rules)
+        ) {
+            once(crate_name).chain(relative).collect()
+        } else {
+            vec![crate_name, relative.last().expect("relative was empty")]
+        }
+    } else {
+        once(crate_name).chain(relative).collect()
+    };
+
+    if did.is_local() {
+        cx.cache.exact_paths.insert(did, fqn);
+    } else {
+        cx.cache.external_paths.insert(did, (fqn, kind));
+    }
+}
+
+pub(crate) fn build_external_trait(cx: &mut DocContext<'_>, did: DefId) -> clean::Trait {
+    let trait_items = cx
+        .tcx
+        .associated_items(did)
+        .in_definition_order()
+        .map(|item| {
+            // When building an external trait, the cleaned trait will have all items public,
+            // which causes methods to have a `pub` prefix, which is invalid since items in traits
+            // can not have a visibility prefix. Thus we override the visibility here manually.
+            // See https://github.com/rust-lang/rust/issues/81274
+            clean::Item { visibility: Visibility::Inherited, ..item.clean(cx) }
+        })
+        .collect();
+
+    let predicates = cx.tcx.predicates_of(did);
+    let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+    let generics = filter_non_trait_generics(did, generics);
+    let (generics, supertrait_bounds) = separate_supertrait_bounds(generics);
+    clean::Trait { def_id: did, generics, items: trait_items, bounds: supertrait_bounds }
+}
+
+fn build_external_function<'tcx>(cx: &mut DocContext<'tcx>, did: DefId) -> Box<clean::Function> {
+    let sig = cx.tcx.fn_sig(did);
+
+    let predicates = cx.tcx.predicates_of(did);
+    let (generics, decl) = clean::enter_impl_trait(cx, |cx| {
+        // NOTE: generics need to be cleaned before the decl!
+        let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+        let decl = clean_fn_decl_from_did_and_sig(cx, Some(did), sig);
+        (generics, decl)
+    });
+    Box::new(clean::Function { decl, generics })
+}
+
+fn build_enum(cx: &mut DocContext<'_>, did: DefId) -> clean::Enum {
+    let predicates = cx.tcx.explicit_predicates_of(did);
+
+    clean::Enum {
+        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        variants: cx.tcx.adt_def(did).variants().iter().map(|v| clean_variant_def(v, cx)).collect(),
+    }
+}
+
+fn build_struct(cx: &mut DocContext<'_>, did: DefId) -> clean::Struct {
+    let predicates = cx.tcx.explicit_predicates_of(did);
+    let variant = cx.tcx.adt_def(did).non_enum_variant();
+
+    clean::Struct {
+        struct_type: variant.ctor_kind,
+        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        fields: variant.fields.iter().map(|x| clean_middle_field(x, cx)).collect(),
+    }
+}
+
+fn build_union(cx: &mut DocContext<'_>, did: DefId) -> clean::Union {
+    let predicates = cx.tcx.explicit_predicates_of(did);
+    let variant = cx.tcx.adt_def(did).non_enum_variant();
+
+    let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+    let fields = variant.fields.iter().map(|x| clean_middle_field(x, cx)).collect();
+    clean::Union { generics, fields }
+}
+
+fn build_type_alias(cx: &mut DocContext<'_>, did: DefId) -> Box<clean::Typedef> {
+    let predicates = cx.tcx.explicit_predicates_of(did);
+    let type_ = clean_middle_ty(cx.tcx.type_of(did), cx, Some(did));
+
+    Box::new(clean::Typedef {
+        type_,
+        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        item_type: None,
+    })
+}
+
+/// Builds all inherent implementations of an ADT (struct/union/enum) or Trait item/path/reexport.
+pub(crate) fn build_impls(
+    cx: &mut DocContext<'_>,
+    parent_module: Option<DefId>,
+    did: DefId,
+    attrs: Option<Attrs<'_>>,
+    ret: &mut Vec<clean::Item>,
+) {
+    let _prof_timer = cx.tcx.sess.prof.generic_activity("build_inherent_impls");
+    let tcx = cx.tcx;
+
+    // for each implementation of an item represented by `did`, build the clean::Item for that impl
+    for &did in tcx.inherent_impls(did).iter() {
+        build_impl(cx, parent_module, did, attrs, ret);
+    }
+}
+
+/// `parent_module` refers to the parent of the re-export, not the original item
+fn merge_attrs(
+    cx: &mut DocContext<'_>,
+    parent_module: Option<DefId>,
+    old_attrs: Attrs<'_>,
+    new_attrs: Option<Attrs<'_>>,
+) -> (clean::Attributes, Option<Arc<clean::cfg::Cfg>>) {
+    // NOTE: If we have additional attributes (from a re-export),
+    // always insert them first. This ensure that re-export
+    // doc comments show up before the original doc comments
+    // when we render them.
+    if let Some(inner) = new_attrs {
+        let mut both = inner.to_vec();
+        both.extend_from_slice(old_attrs);
+        (
+            if let Some(new_id) = parent_module {
+                Attributes::from_ast_with_additional(old_attrs, (inner, new_id))
+            } else {
+                Attributes::from_ast(&both)
+            },
+            both.cfg(cx.tcx, &cx.cache.hidden_cfg),
+        )
+    } else {
+        (Attributes::from_ast(&old_attrs), old_attrs.cfg(cx.tcx, &cx.cache.hidden_cfg))
+    }
+}
+
+/// Inline an `impl`, inherent or of a trait. The `did` must be for an `impl`.
+pub(crate) fn build_impl(
+    cx: &mut DocContext<'_>,
+    parent_module: Option<DefId>,
+    did: DefId,
+    attrs: Option<Attrs<'_>>,
+    ret: &mut Vec<clean::Item>,
+) {
+    if !cx.inlined.insert(did.into()) {
+        return;
+    }
+
+    let _prof_timer = cx.tcx.sess.prof.generic_activity("build_impl");
+
+    let tcx = cx.tcx;
+    let associated_trait = tcx.impl_trait_ref(did);
+
+    // Only inline impl if the implemented trait is
+    // reachable in rustdoc generated documentation
+    if !did.is_local() {
+        if let Some(traitref) = associated_trait {
+            let did = traitref.def_id;
+            if !cx.cache.access_levels.is_public(did) {
+                return;
+            }
+
+            if let Some(stab) = tcx.lookup_stability(did) {
+                if stab.is_unstable() && stab.feature == sym::rustc_private {
+                    return;
+                }
+            }
+        }
+    }
+
+    let impl_item = match did.as_local() {
+        Some(did) => match &tcx.hir().expect_item(did).kind {
+            hir::ItemKind::Impl(impl_) => Some(impl_),
+            _ => panic!("`DefID` passed to `build_impl` is not an `impl"),
+        },
+        None => None,
+    };
+
+    let for_ = match &impl_item {
+        Some(impl_) => clean_ty(impl_.self_ty, cx),
+        None => clean_middle_ty(tcx.type_of(did), cx, Some(did)),
+    };
+
+    // Only inline impl if the implementing type is
+    // reachable in rustdoc generated documentation
+    if !did.is_local() {
+        if let Some(did) = for_.def_id(&cx.cache) {
+            if !cx.cache.access_levels.is_public(did) {
+                return;
+            }
+
+            if let Some(stab) = tcx.lookup_stability(did) {
+                if stab.is_unstable() && stab.feature == sym::rustc_private {
+                    return;
+                }
+            }
+        }
+    }
+
+    let document_hidden = cx.render_options.document_hidden;
+    let predicates = tcx.explicit_predicates_of(did);
+    let (trait_items, generics) = match impl_item {
+        Some(impl_) => (
+            impl_
+                .items
+                .iter()
+                .map(|item| tcx.hir().impl_item(item.id))
+                .filter(|item| {
+                    // Filter out impl items whose corresponding trait item has `doc(hidden)`
+                    // not to document such impl items.
+                    // For inherent impls, we don't do any filtering, because that's already done in strip_hidden.rs.
+
+                    // When `--document-hidden-items` is passed, we don't
+                    // do any filtering, too.
+                    if document_hidden {
+                        return true;
+                    }
+                    if let Some(associated_trait) = associated_trait {
+                        let assoc_kind = match item.kind {
+                            hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
+                            hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
+                            hir::ImplItemKind::TyAlias(..) => ty::AssocKind::Type,
+                        };
+                        let trait_item = tcx
+                            .associated_items(associated_trait.def_id)
+                            .find_by_name_and_kind(
+                                tcx,
+                                item.ident,
+                                assoc_kind,
+                                associated_trait.def_id,
+                            )
+                            .unwrap(); // SAFETY: For all impl items there exists trait item that has the same name.
+                        !tcx.is_doc_hidden(trait_item.def_id)
+                    } else {
+                        true
+                    }
+                })
+                .map(|item| item.clean(cx))
+                .collect::<Vec<_>>(),
+            impl_.generics.clean(cx),
+        ),
+        None => (
+            tcx.associated_items(did)
+                .in_definition_order()
+                .filter(|item| {
+                    // If this is a trait impl, filter out associated items whose corresponding item
+                    // in the associated trait is marked `doc(hidden)`.
+                    // If this is an inherent impl, filter out private associated items.
+                    if let Some(associated_trait) = associated_trait {
+                        let trait_item = tcx
+                            .associated_items(associated_trait.def_id)
+                            .find_by_name_and_kind(
+                                tcx,
+                                item.ident(tcx),
+                                item.kind,
+                                associated_trait.def_id,
+                            )
+                            .unwrap(); // corresponding associated item has to exist
+                        !tcx.is_doc_hidden(trait_item.def_id)
+                    } else {
+                        item.visibility(tcx).is_public()
+                    }
+                })
+                .map(|item| item.clean(cx))
+                .collect::<Vec<_>>(),
+            clean::enter_impl_trait(cx, |cx| {
+                clean_ty_generics(cx, tcx.generics_of(did), predicates)
+            }),
+        ),
+    };
+    let polarity = tcx.impl_polarity(did);
+    let trait_ = associated_trait.map(|t| clean_trait_ref_with_bindings(cx, t, &[]));
+    if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait() {
+        super::build_deref_target_impls(cx, &trait_items, ret);
+    }
+
+    // Return if the trait itself or any types of the generic parameters are doc(hidden).
+    let mut stack: Vec<&Type> = vec![&for_];
+
+    if let Some(did) = trait_.as_ref().map(|t| t.def_id()) {
+        if tcx.is_doc_hidden(did) {
+            return;
+        }
+    }
+    if let Some(generics) = trait_.as_ref().and_then(|t| t.generics()) {
+        stack.extend(generics);
+    }
+
+    while let Some(ty) = stack.pop() {
+        if let Some(did) = ty.def_id(&cx.cache) {
+            if tcx.is_doc_hidden(did) {
+                return;
+            }
+        }
+        if let Some(generics) = ty.generics() {
+            stack.extend(generics);
+        }
+    }
+
+    if let Some(did) = trait_.as_ref().map(|t| t.def_id()) {
+        record_extern_trait(cx, did);
+    }
+
+    let (merged_attrs, cfg) = merge_attrs(cx, parent_module, load_attrs(cx, did), attrs);
+    trace!("merged_attrs={:?}", merged_attrs);
+
+    trace!(
+        "build_impl: impl {:?} for {:?}",
+        trait_.as_ref().map(|t| t.def_id()),
+        for_.def_id(&cx.cache)
+    );
+    ret.push(clean::Item::from_def_id_and_attrs_and_parts(
+        did,
+        None,
+        clean::ImplItem(Box::new(clean::Impl {
+            unsafety: hir::Unsafety::Normal,
+            generics,
+            trait_,
+            for_,
+            items: trait_items,
+            polarity,
+            kind: if utils::has_doc_flag(tcx, did, sym::fake_variadic) {
+                ImplKind::FakeVaradic
+            } else {
+                ImplKind::Normal
+            },
+        })),
+        Box::new(merged_attrs),
+        cx,
+        cfg,
+    ));
+}
+
+fn build_module(
+    cx: &mut DocContext<'_>,
+    did: DefId,
+    visited: &mut FxHashSet<DefId>,
+) -> clean::Module {
+    let items = build_module_items(cx, did, visited, &mut FxHashSet::default());
+
+    let span = clean::Span::new(cx.tcx.def_span(did));
+    clean::Module { items, span }
+}
+
+fn build_module_items(
+    cx: &mut DocContext<'_>,
+    did: DefId,
+    visited: &mut FxHashSet<DefId>,
+    inlined_names: &mut FxHashSet<(ItemType, Symbol)>,
+) -> Vec<clean::Item> {
+    let mut items = Vec::new();
+
+    // If we're re-exporting a re-export it may actually re-export something in
+    // two namespaces, so the target may be listed twice. Make sure we only
+    // visit each node at most once.
+    for &item in cx.tcx.module_children(did).iter() {
+        if item.vis.is_public() {
+            let res = item.res.expect_non_local();
+            if let Some(def_id) = res.mod_def_id() {
+                // If we're inlining a glob import, it's possible to have
+                // two distinct modules with the same name. We don't want to
+                // inline it, or mark any of its contents as visited.
+                if did == def_id
+                    || inlined_names.contains(&(ItemType::Module, item.ident.name))
+                    || !visited.insert(def_id)
+                {
+                    continue;
+                }
+            }
+            if let Res::PrimTy(p) = res {
+                // Primitive types can't be inlined so generate an import instead.
+                let prim_ty = clean::PrimitiveType::from(p);
+                items.push(clean::Item {
+                    name: None,
+                    attrs: Box::new(clean::Attributes::default()),
+                    item_id: ItemId::Primitive(prim_ty, did.krate),
+                    visibility: clean::Public,
+                    kind: Box::new(clean::ImportItem(clean::Import::new_simple(
+                        item.ident.name,
+                        clean::ImportSource {
+                            path: clean::Path {
+                                res,
+                                segments: vec![clean::PathSegment {
+                                    name: prim_ty.as_sym(),
+                                    args: clean::GenericArgs::AngleBracketed {
+                                        args: Default::default(),
+                                        bindings: ThinVec::new(),
+                                    },
+                                }],
+                            },
+                            did: None,
+                        },
+                        true,
+                    ))),
+                    cfg: None,
+                });
+            } else if let Some(i) = try_inline(cx, did, None, res, item.ident.name, None, visited) {
+                items.extend(i)
+            }
+        }
+    }
+
+    items
+}
+
+pub(crate) fn print_inlined_const(tcx: TyCtxt<'_>, did: DefId) -> String {
+    if let Some(did) = did.as_local() {
+        let hir_id = tcx.hir().local_def_id_to_hir_id(did);
+        rustc_hir_pretty::id_to_string(&tcx.hir(), hir_id)
+    } else {
+        tcx.rendered_const(did).clone()
+    }
+}
+
+fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
+    clean::Constant {
+        type_: clean_middle_ty(cx.tcx.type_of(def_id), cx, Some(def_id)),
+        kind: clean::ConstantKind::Extern { def_id },
+    }
+}
+
+fn build_static(cx: &mut DocContext<'_>, did: DefId, mutable: bool) -> clean::Static {
+    clean::Static {
+        type_: clean_middle_ty(cx.tcx.type_of(did), cx, Some(did)),
+        mutability: if mutable { Mutability::Mut } else { Mutability::Not },
+        expr: None,
+    }
+}
+
+fn build_macro(
+    cx: &mut DocContext<'_>,
+    def_id: DefId,
+    name: Symbol,
+    import_def_id: Option<DefId>,
+) -> clean::ItemKind {
+    match CStore::from_tcx(cx.tcx).load_macro_untracked(def_id, cx.sess()) {
+        LoadedMacro::MacroDef(item_def, _) => {
+            if let ast::ItemKind::MacroDef(ref def) = item_def.kind {
+                let vis = clean_visibility(cx.tcx.visibility(import_def_id.unwrap_or(def_id)));
+                clean::MacroItem(clean::Macro {
+                    source: utils::display_macro_source(cx, name, def, def_id, vis),
+                })
+            } else {
+                unreachable!()
+            }
+        }
+        LoadedMacro::ProcMacro(ext) => clean::ProcMacroItem(clean::ProcMacro {
+            kind: ext.macro_kind(),
+            helpers: ext.helper_attrs,
+        }),
+    }
+}
+
+/// A trait's generics clause actually contains all of the predicates for all of
+/// its associated types as well. We specifically move these clauses to the
+/// associated types instead when displaying, so when we're generating the
+/// generics for the trait itself we need to be sure to remove them.
+/// We also need to remove the implied "recursive" Self: Trait bound.
+///
+/// The inverse of this filtering logic can be found in the `Clean`
+/// implementation for `AssociatedType`
+fn filter_non_trait_generics(trait_did: DefId, mut g: clean::Generics) -> clean::Generics {
+    for pred in &mut g.where_predicates {
+        match *pred {
+            clean::WherePredicate::BoundPredicate {
+                ty: clean::Generic(ref s),
+                ref mut bounds,
+                ..
+            } if *s == kw::SelfUpper => {
+                bounds.retain(|bound| match bound {
+                    clean::GenericBound::TraitBound(clean::PolyTrait { trait_, .. }, _) => {
+                        trait_.def_id() != trait_did
+                    }
+                    _ => true,
+                });
+            }
+            _ => {}
+        }
+    }
+
+    g.where_predicates.retain(|pred| match pred {
+        clean::WherePredicate::BoundPredicate {
+            ty: clean::QPath { self_type: box clean::Generic(ref s), trait_, .. },
+            bounds,
+            ..
+        } => !(bounds.is_empty() || *s == kw::SelfUpper && trait_.def_id() == trait_did),
+        _ => true,
+    });
+    g
+}
+
+/// Supertrait bounds for a trait are also listed in the generics coming from
+/// the metadata for a crate, so we want to separate those out and create a new
+/// list of explicit supertrait bounds to render nicely.
+fn separate_supertrait_bounds(
+    mut g: clean::Generics,
+) -> (clean::Generics, Vec<clean::GenericBound>) {
+    let mut ty_bounds = Vec::new();
+    g.where_predicates.retain(|pred| match *pred {
+        clean::WherePredicate::BoundPredicate { ty: clean::Generic(ref s), ref bounds, .. }
+            if *s == kw::SelfUpper =>
+        {
+            ty_bounds.extend(bounds.iter().cloned());
+            false
+        }
+        _ => true,
+    });
+    (g, ty_bounds)
+}
+
+pub(crate) fn record_extern_trait(cx: &mut DocContext<'_>, did: DefId) {
+    if did.is_local() {
+        return;
+    }
+
+    {
+        if cx.external_traits.borrow().contains_key(&did) || cx.active_extern_traits.contains(&did)
+        {
+            return;
+        }
+    }
+
+    {
+        cx.active_extern_traits.insert(did);
+    }
+
+    debug!("record_extern_trait: {:?}", did);
+    let trait_ = build_external_trait(cx, did);
+
+    let trait_ = clean::TraitWithExtraInfo {
+        trait_,
+        is_notable: clean::utils::has_doc_flag(cx.tcx, did, sym::notable_trait),
+    };
+    cx.external_traits.borrow_mut().insert(did, trait_);
+    cx.active_extern_traits.remove(&did);
+}
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
new file mode 100644
index 000000000..929f5f89b
--- /dev/null
+++ b/src/librustdoc/clean/mod.rs
@@ -0,0 +1,2242 @@
+//! This module contains the "cleaned" pieces of the AST, and the functions
+//! that clean them.
+
+mod auto_trait;
+mod blanket_impl;
+pub(crate) mod cfg;
+pub(crate) mod inline;
+mod render_macro_matchers;
+mod simplify;
+pub(crate) mod types;
+pub(crate) mod utils;
+
+use rustc_ast as ast;
+use rustc_attr as attr;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir as hir;
+use rustc_hir::def::{CtorKind, DefKind, Res};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_hir::PredicateOrigin;
+use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
+use rustc_middle::middle::resolve_lifetime as rl;
+use rustc_middle::ty::fold::TypeFolder;
+use rustc_middle::ty::subst::{InternalSubsts, Subst};
+use rustc_middle::ty::{self, AdtKind, DefIdTree, EarlyBinder, Lift, Ty, TyCtxt};
+use rustc_middle::{bug, span_bug};
+use rustc_span::hygiene::{AstPass, MacroKind};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{self, ExpnKind};
+use rustc_typeck::hir_ty_to_ty;
+
+use std::assert_matches::assert_matches;
+use std::collections::hash_map::Entry;
+use std::collections::BTreeMap;
+use std::default::Default;
+use std::hash::Hash;
+use std::{mem, vec};
+
+use crate::core::{self, DocContext, ImplTraitParam};
+use crate::formats::item_type::ItemType;
+use crate::visit_ast::Module as DocModule;
+
+use utils::*;
+
+pub(crate) use self::types::*;
+pub(crate) use self::utils::{get_auto_trait_and_blanket_impls, krate, register_res};
+
+pub(crate) trait Clean<'tcx, T> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> T;
+}
+
+impl<'tcx> Clean<'tcx, Item> for DocModule<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
+        let mut items: Vec<Item> = vec![];
+        let mut inserted = FxHashSet::default();
+        items.extend(self.foreigns.iter().map(|(item, renamed)| {
+            let item = clean_maybe_renamed_foreign_item(cx, item, *renamed);
+            if let Some(name) = item.name {
+                inserted.insert((item.type_(), name));
+            }
+            item
+        }));
+        items.extend(self.mods.iter().map(|x| {
+            inserted.insert((ItemType::Module, x.name));
+            x.clean(cx)
+        }));
+
+        // Split up imports from all other items.
+        //
+        // This covers the case where somebody does an import which should pull in an item,
+        // but there's already an item with the same namespace and same name. Rust gives
+        // priority to the not-imported one, so we should, too.
+        items.extend(self.items.iter().flat_map(|(item, renamed)| {
+            // First, lower everything other than imports.
+            if matches!(item.kind, hir::ItemKind::Use(_, hir::UseKind::Glob)) {
+                return Vec::new();
+            }
+            let v = clean_maybe_renamed_item(cx, item, *renamed);
+            for item in &v {
+                if let Some(name) = item.name {
+                    inserted.insert((item.type_(), name));
+                }
+            }
+            v
+        }));
+        items.extend(self.items.iter().flat_map(|(item, renamed)| {
+            // Now we actually lower the imports, skipping everything else.
+            if let hir::ItemKind::Use(path, hir::UseKind::Glob) = item.kind {
+                let name = renamed.unwrap_or_else(|| cx.tcx.hir().name(item.hir_id()));
+                clean_use_statement(item, name, path, hir::UseKind::Glob, cx, &mut inserted)
+            } else {
+                // skip everything else
+                Vec::new()
+            }
+        }));
+
+        // determine if we should display the inner contents or
+        // the outer `mod` item for the source code.
+
+        let span = Span::new({
+            let where_outer = self.where_outer(cx.tcx);
+            let sm = cx.sess().source_map();
+            let outer = sm.lookup_char_pos(where_outer.lo());
+            let inner = sm.lookup_char_pos(self.where_inner.lo());
+            if outer.file.start_pos == inner.file.start_pos {
+                // mod foo { ... }
+                where_outer
+            } else {
+                // mod foo; (and a separate SourceFile for the contents)
+                self.where_inner
+            }
+        });
+
+        Item::from_hir_id_and_parts(
+            self.id,
+            Some(self.name),
+            ModuleItem(Module { items, span }),
+            cx,
+        )
+    }
+}
+
+impl<'tcx> Clean<'tcx, Option<GenericBound>> for hir::GenericBound<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Option<GenericBound> {
+        Some(match *self {
+            hir::GenericBound::Outlives(lt) => GenericBound::Outlives(clean_lifetime(lt, cx)),
+            hir::GenericBound::LangItemTrait(lang_item, span, _, generic_args) => {
+                let def_id = cx.tcx.require_lang_item(lang_item, Some(span));
+
+                let trait_ref = ty::TraitRef::identity(cx.tcx, def_id).skip_binder();
+
+                let generic_args = generic_args.clean(cx);
+                let GenericArgs::AngleBracketed { bindings, .. } = generic_args
+                else {
+                    bug!("clean: parenthesized `GenericBound::LangItemTrait`");
+                };
+
+                let trait_ = clean_trait_ref_with_bindings(cx, trait_ref, &bindings);
+                GenericBound::TraitBound(
+                    PolyTrait { trait_, generic_params: vec![] },
+                    hir::TraitBoundModifier::None,
+                )
+            }
+            hir::GenericBound::Trait(ref t, modifier) => {
+                // `T: ~const Destruct` is hidden because `T: Destruct` is a no-op.
+                if modifier == hir::TraitBoundModifier::MaybeConst
+                    && cx.tcx.lang_items().destruct_trait()
+                        == Some(t.trait_ref.trait_def_id().unwrap())
+                {
+                    return None;
+                }
+
+                GenericBound::TraitBound(t.clean(cx), modifier)
+            }
+        })
+    }
+}
+
+pub(crate) fn clean_trait_ref_with_bindings<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    trait_ref: ty::TraitRef<'tcx>,
+    bindings: &[TypeBinding],
+) -> Path {
+    let kind = cx.tcx.def_kind(trait_ref.def_id).into();
+    if !matches!(kind, ItemType::Trait | ItemType::TraitAlias) {
+        span_bug!(cx.tcx.def_span(trait_ref.def_id), "`TraitRef` had unexpected kind {:?}", kind);
+    }
+    inline::record_extern_fqn(cx, trait_ref.def_id, kind);
+    let path = external_path(cx, trait_ref.def_id, true, bindings.to_vec(), trait_ref.substs);
+
+    debug!("ty::TraitRef\n  subst: {:?}\n", trait_ref.substs);
+
+    path
+}
+
+fn clean_poly_trait_ref_with_bindings<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    poly_trait_ref: ty::PolyTraitRef<'tcx>,
+    bindings: &[TypeBinding],
+) -> GenericBound {
+    let poly_trait_ref = poly_trait_ref.lift_to_tcx(cx.tcx).unwrap();
+
+    // collect any late bound regions
+    let late_bound_regions: Vec<_> = cx
+        .tcx
+        .collect_referenced_late_bound_regions(&poly_trait_ref)
+        .into_iter()
+        .filter_map(|br| match br {
+            ty::BrNamed(_, name) if name != kw::UnderscoreLifetime => Some(GenericParamDef {
+                name,
+                kind: GenericParamDefKind::Lifetime { outlives: vec![] },
+            }),
+            _ => None,
+        })
+        .collect();
+
+    let trait_ = clean_trait_ref_with_bindings(cx, poly_trait_ref.skip_binder(), bindings);
+    GenericBound::TraitBound(
+        PolyTrait { trait_, generic_params: late_bound_regions },
+        hir::TraitBoundModifier::None,
+    )
+}
+
+impl<'tcx> Clean<'tcx, GenericBound> for ty::PolyTraitRef<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> GenericBound {
+        clean_poly_trait_ref_with_bindings(cx, *self, &[])
+    }
+}
+
+fn clean_lifetime<'tcx>(lifetime: hir::Lifetime, cx: &mut DocContext<'tcx>) -> Lifetime {
+    let def = cx.tcx.named_region(lifetime.hir_id);
+    if let Some(
+        rl::Region::EarlyBound(_, node_id)
+        | rl::Region::LateBound(_, _, node_id)
+        | rl::Region::Free(_, node_id),
+    ) = def
+    {
+        if let Some(lt) = cx.substs.get(&node_id).and_then(|p| p.as_lt()).cloned() {
+            return lt;
+        }
+    }
+    Lifetime(lifetime.name.ident().name)
+}
+
+pub(crate) fn clean_const<'tcx>(constant: &hir::ConstArg, cx: &mut DocContext<'tcx>) -> Constant {
+    let def_id = cx.tcx.hir().body_owner_def_id(constant.value.body).to_def_id();
+    Constant {
+        type_: clean_middle_ty(cx.tcx.type_of(def_id), cx, Some(def_id)),
+        kind: ConstantKind::Anonymous { body: constant.value.body },
+    }
+}
+
+pub(crate) fn clean_middle_const<'tcx>(
+    constant: ty::Const<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> Constant {
+    // FIXME: instead of storing the stringified expression, store `self` directly instead.
+    Constant {
+        type_: clean_middle_ty(constant.ty(), cx, None),
+        kind: ConstantKind::TyConst { expr: constant.to_string() },
+    }
+}
+
+pub(crate) fn clean_middle_region<'tcx>(region: ty::Region<'tcx>) -> Option<Lifetime> {
+    match *region {
+        ty::ReStatic => Some(Lifetime::statik()),
+        ty::ReLateBound(_, ty::BoundRegion { kind: ty::BrNamed(_, name), .. }) => {
+            if name != kw::UnderscoreLifetime { Some(Lifetime(name)) } else { None }
+        }
+        ty::ReEarlyBound(ref data) => {
+            if data.name != kw::UnderscoreLifetime {
+                Some(Lifetime(data.name))
+            } else {
+                None
+            }
+        }
+        ty::ReLateBound(..)
+        | ty::ReFree(..)
+        | ty::ReVar(..)
+        | ty::RePlaceholder(..)
+        | ty::ReEmpty(_)
+        | ty::ReErased => {
+            debug!("cannot clean region {:?}", region);
+            None
+        }
+    }
+}
+
+impl<'tcx> Clean<'tcx, Option<WherePredicate>> for hir::WherePredicate<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Option<WherePredicate> {
+        if !self.in_where_clause() {
+            return None;
+        }
+        Some(match *self {
+            hir::WherePredicate::BoundPredicate(ref wbp) => {
+                let bound_params = wbp
+                    .bound_generic_params
+                    .iter()
+                    .map(|param| {
+                        // Higher-ranked params must be lifetimes.
+                        // Higher-ranked lifetimes can't have bounds.
+                        assert_matches!(
+                            param,
+                            hir::GenericParam { kind: hir::GenericParamKind::Lifetime { .. }, .. }
+                        );
+                        Lifetime(param.name.ident().name)
+                    })
+                    .collect();
+                WherePredicate::BoundPredicate {
+                    ty: clean_ty(wbp.bounded_ty, cx),
+                    bounds: wbp.bounds.iter().filter_map(|x| x.clean(cx)).collect(),
+                    bound_params,
+                }
+            }
+
+            hir::WherePredicate::RegionPredicate(ref wrp) => WherePredicate::RegionPredicate {
+                lifetime: clean_lifetime(wrp.lifetime, cx),
+                bounds: wrp.bounds.iter().filter_map(|x| x.clean(cx)).collect(),
+            },
+
+            hir::WherePredicate::EqPredicate(ref wrp) => WherePredicate::EqPredicate {
+                lhs: clean_ty(wrp.lhs_ty, cx),
+                rhs: clean_ty(wrp.rhs_ty, cx).into(),
+            },
+        })
+    }
+}
+
+impl<'tcx> Clean<'tcx, Option<WherePredicate>> for ty::Predicate<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Option<WherePredicate> {
+        let bound_predicate = self.kind();
+        match bound_predicate.skip_binder() {
+            ty::PredicateKind::Trait(pred) => {
+                clean_poly_trait_predicate(bound_predicate.rebind(pred), cx)
+            }
+            ty::PredicateKind::RegionOutlives(pred) => clean_region_outlives_predicate(pred),
+            ty::PredicateKind::TypeOutlives(pred) => clean_type_outlives_predicate(pred, cx),
+            ty::PredicateKind::Projection(pred) => Some(clean_projection_predicate(pred, cx)),
+            ty::PredicateKind::ConstEvaluatable(..) => None,
+            ty::PredicateKind::WellFormed(..) => None,
+
+            ty::PredicateKind::Subtype(..)
+            | ty::PredicateKind::Coerce(..)
+            | ty::PredicateKind::ObjectSafe(..)
+            | ty::PredicateKind::ClosureKind(..)
+            | ty::PredicateKind::ConstEquate(..)
+            | ty::PredicateKind::TypeWellFormedFromEnv(..) => panic!("not user writable"),
+        }
+    }
+}
+
+fn clean_poly_trait_predicate<'tcx>(
+    pred: ty::PolyTraitPredicate<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> Option<WherePredicate> {
+    // `T: ~const Destruct` is hidden because `T: Destruct` is a no-op.
+    if pred.skip_binder().constness == ty::BoundConstness::ConstIfConst
+        && Some(pred.skip_binder().def_id()) == cx.tcx.lang_items().destruct_trait()
+    {
+        return None;
+    }
+
+    let poly_trait_ref = pred.map_bound(|pred| pred.trait_ref);
+    Some(WherePredicate::BoundPredicate {
+        ty: clean_middle_ty(poly_trait_ref.skip_binder().self_ty(), cx, None),
+        bounds: vec![poly_trait_ref.clean(cx)],
+        bound_params: Vec::new(),
+    })
+}
+
+fn clean_region_outlives_predicate<'tcx>(
+    pred: ty::OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>,
+) -> Option<WherePredicate> {
+    let ty::OutlivesPredicate(a, b) = pred;
+
+    if a.is_empty() && b.is_empty() {
+        return None;
+    }
+
+    Some(WherePredicate::RegionPredicate {
+        lifetime: clean_middle_region(a).expect("failed to clean lifetime"),
+        bounds: vec![GenericBound::Outlives(
+            clean_middle_region(b).expect("failed to clean bounds"),
+        )],
+    })
+}
+
+fn clean_type_outlives_predicate<'tcx>(
+    pred: ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>,
+    cx: &mut DocContext<'tcx>,
+) -> Option<WherePredicate> {
+    let ty::OutlivesPredicate(ty, lt) = pred;
+
+    if lt.is_empty() {
+        return None;
+    }
+
+    Some(WherePredicate::BoundPredicate {
+        ty: clean_middle_ty(ty, cx, None),
+        bounds: vec![GenericBound::Outlives(
+            clean_middle_region(lt).expect("failed to clean lifetimes"),
+        )],
+        bound_params: Vec::new(),
+    })
+}
+
+fn clean_middle_term<'tcx>(term: ty::Term<'tcx>, cx: &mut DocContext<'tcx>) -> Term {
+    match term {
+        ty::Term::Ty(ty) => Term::Type(clean_middle_ty(ty, cx, None)),
+        ty::Term::Const(c) => Term::Constant(clean_middle_const(c, cx)),
+    }
+}
+
+fn clean_hir_term<'tcx>(term: &hir::Term<'tcx>, cx: &mut DocContext<'tcx>) -> Term {
+    match term {
+        hir::Term::Ty(ty) => Term::Type(clean_ty(ty, cx)),
+        hir::Term::Const(c) => {
+            let def_id = cx.tcx.hir().local_def_id(c.hir_id);
+            Term::Constant(clean_middle_const(ty::Const::from_anon_const(cx.tcx, def_id), cx))
+        }
+    }
+}
+
+fn clean_projection_predicate<'tcx>(
+    pred: ty::ProjectionPredicate<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> WherePredicate {
+    let ty::ProjectionPredicate { projection_ty, term } = pred;
+    WherePredicate::EqPredicate {
+        lhs: clean_projection(projection_ty, cx, None),
+        rhs: clean_middle_term(term, cx),
+    }
+}
+
+fn clean_projection<'tcx>(
+    ty: ty::ProjectionTy<'tcx>,
+    cx: &mut DocContext<'tcx>,
+    def_id: Option<DefId>,
+) -> Type {
+    let lifted = ty.lift_to_tcx(cx.tcx).unwrap();
+    let trait_ = clean_trait_ref_with_bindings(cx, lifted.trait_ref(cx.tcx), &[]);
+    let self_type = clean_middle_ty(ty.self_ty(), cx, None);
+    let self_def_id = if let Some(def_id) = def_id {
+        cx.tcx.opt_parent(def_id).or(Some(def_id))
+    } else {
+        self_type.def_id(&cx.cache)
+    };
+    let should_show_cast = compute_should_show_cast(self_def_id, &trait_, &self_type);
+    Type::QPath {
+        assoc: Box::new(projection_to_path_segment(ty, cx)),
+        should_show_cast,
+        self_type: Box::new(self_type),
+        trait_,
+    }
+}
+
+fn compute_should_show_cast(self_def_id: Option<DefId>, trait_: &Path, self_type: &Type) -> bool {
+    !trait_.segments.is_empty()
+        && self_def_id
+            .zip(Some(trait_.def_id()))
+            .map_or(!self_type.is_self_type(), |(id, trait_)| id != trait_)
+}
+
+fn projection_to_path_segment<'tcx>(
+    ty: ty::ProjectionTy<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> PathSegment {
+    let item = cx.tcx.associated_item(ty.item_def_id);
+    let generics = cx.tcx.generics_of(ty.item_def_id);
+    PathSegment {
+        name: item.name,
+        args: GenericArgs::AngleBracketed {
+            args: substs_to_args(cx, &ty.substs[generics.parent_count..], false).into(),
+            bindings: Default::default(),
+        },
+    }
+}
+
+fn clean_generic_param_def<'tcx>(
+    def: &ty::GenericParamDef,
+    cx: &mut DocContext<'tcx>,
+) -> GenericParamDef {
+    let (name, kind) = match def.kind {
+        ty::GenericParamDefKind::Lifetime => {
+            (def.name, GenericParamDefKind::Lifetime { outlives: vec![] })
+        }
+        ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
+            let default = if has_default {
+                Some(clean_middle_ty(cx.tcx.type_of(def.def_id), cx, Some(def.def_id)))
+            } else {
+                None
+            };
+            (
+                def.name,
+                GenericParamDefKind::Type {
+                    did: def.def_id,
+                    bounds: vec![], // These are filled in from the where-clauses.
+                    default: default.map(Box::new),
+                    synthetic,
+                },
+            )
+        }
+        ty::GenericParamDefKind::Const { has_default } => (
+            def.name,
+            GenericParamDefKind::Const {
+                did: def.def_id,
+                ty: Box::new(clean_middle_ty(cx.tcx.type_of(def.def_id), cx, Some(def.def_id))),
+                default: match has_default {
+                    true => Some(Box::new(cx.tcx.const_param_default(def.def_id).to_string())),
+                    false => None,
+                },
+            },
+        ),
+    };
+
+    GenericParamDef { name, kind }
+}
+
+fn clean_generic_param<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    generics: Option<&hir::Generics<'tcx>>,
+    param: &hir::GenericParam<'tcx>,
+) -> GenericParamDef {
+    let did = cx.tcx.hir().local_def_id(param.hir_id);
+    let (name, kind) = match param.kind {
+        hir::GenericParamKind::Lifetime { .. } => {
+            let outlives = if let Some(generics) = generics {
+                generics
+                    .outlives_for_param(did)
+                    .filter(|bp| !bp.in_where_clause)
+                    .flat_map(|bp| bp.bounds)
+                    .map(|bound| match bound {
+                        hir::GenericBound::Outlives(lt) => clean_lifetime(*lt, cx),
+                        _ => panic!(),
+                    })
+                    .collect()
+            } else {
+                Vec::new()
+            };
+            (param.name.ident().name, GenericParamDefKind::Lifetime { outlives })
+        }
+        hir::GenericParamKind::Type { ref default, synthetic } => {
+            let bounds = if let Some(generics) = generics {
+                generics
+                    .bounds_for_param(did)
+                    .filter(|bp| bp.origin != PredicateOrigin::WhereClause)
+                    .flat_map(|bp| bp.bounds)
+                    .filter_map(|x| x.clean(cx))
+                    .collect()
+            } else {
+                Vec::new()
+            };
+            (
+                param.name.ident().name,
+                GenericParamDefKind::Type {
+                    did: did.to_def_id(),
+                    bounds,
+                    default: default.map(|t| clean_ty(t, cx)).map(Box::new),
+                    synthetic,
+                },
+            )
+        }
+        hir::GenericParamKind::Const { ty, default } => (
+            param.name.ident().name,
+            GenericParamDefKind::Const {
+                did: did.to_def_id(),
+                ty: Box::new(clean_ty(ty, cx)),
+                default: default.map(|ct| {
+                    let def_id = cx.tcx.hir().local_def_id(ct.hir_id);
+                    Box::new(ty::Const::from_anon_const(cx.tcx, def_id).to_string())
+                }),
+            },
+        ),
+    };
+
+    GenericParamDef { name, kind }
+}
+
+/// Synthetic type-parameters are inserted after normal ones.
+/// In order for normal parameters to be able to refer to synthetic ones,
+/// scans them first.
+fn is_impl_trait(param: &hir::GenericParam<'_>) -> bool {
+    match param.kind {
+        hir::GenericParamKind::Type { synthetic, .. } => synthetic,
+        _ => false,
+    }
+}
+
+/// This can happen for `async fn`, e.g. `async fn f<'_>(&'_ self)`.
+///
+/// See `lifetime_to_generic_param` in `rustc_ast_lowering` for more information.
+fn is_elided_lifetime(param: &hir::GenericParam<'_>) -> bool {
+    matches!(param.kind, hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Elided })
+}
+
+impl<'tcx> Clean<'tcx, Generics> for hir::Generics<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Generics {
+        let impl_trait_params = self
+            .params
+            .iter()
+            .filter(|param| is_impl_trait(param))
+            .map(|param| {
+                let param = clean_generic_param(cx, Some(self), param);
+                match param.kind {
+                    GenericParamDefKind::Lifetime { .. } => unreachable!(),
+                    GenericParamDefKind::Type { did, ref bounds, .. } => {
+                        cx.impl_trait_bounds.insert(did.into(), bounds.clone());
+                    }
+                    GenericParamDefKind::Const { .. } => unreachable!(),
+                }
+                param
+            })
+            .collect::<Vec<_>>();
+
+        let mut params = Vec::with_capacity(self.params.len());
+        for p in self.params.iter().filter(|p| !is_impl_trait(p) && !is_elided_lifetime(p)) {
+            let p = clean_generic_param(cx, Some(self), p);
+            params.push(p);
+        }
+        params.extend(impl_trait_params);
+
+        let mut generics = Generics {
+            params,
+            where_predicates: self.predicates.iter().filter_map(|x| x.clean(cx)).collect(),
+        };
+
+        // Some duplicates are generated for ?Sized bounds between type params and where
+        // predicates. The point in here is to move the bounds definitions from type params
+        // to where predicates when such cases occur.
+        for where_pred in &mut generics.where_predicates {
+            match *where_pred {
+                WherePredicate::BoundPredicate {
+                    ty: Generic(ref name), ref mut bounds, ..
+                } => {
+                    if bounds.is_empty() {
+                        for param in &mut generics.params {
+                            match param.kind {
+                                GenericParamDefKind::Lifetime { .. } => {}
+                                GenericParamDefKind::Type { bounds: ref mut ty_bounds, .. } => {
+                                    if &param.name == name {
+                                        mem::swap(bounds, ty_bounds);
+                                        break;
+                                    }
+                                }
+                                GenericParamDefKind::Const { .. } => {}
+                            }
+                        }
+                    }
+                }
+                _ => continue,
+            }
+        }
+        generics
+    }
+}
+
+fn clean_ty_generics<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    gens: &ty::Generics,
+    preds: ty::GenericPredicates<'tcx>,
+) -> Generics {
+    // Don't populate `cx.impl_trait_bounds` before `clean`ning `where` clauses,
+    // since `Clean for ty::Predicate` would consume them.
+    let mut impl_trait = BTreeMap::<ImplTraitParam, Vec<GenericBound>>::default();
+
+    // Bounds in the type_params and lifetimes fields are repeated in the
+    // predicates field (see rustc_typeck::collect::ty_generics), so remove
+    // them.
+    let stripped_params = gens
+        .params
+        .iter()
+        .filter_map(|param| match param.kind {
+            ty::GenericParamDefKind::Lifetime if param.name == kw::UnderscoreLifetime => None,
+            ty::GenericParamDefKind::Lifetime => Some(clean_generic_param_def(param, cx)),
+            ty::GenericParamDefKind::Type { synthetic, .. } => {
+                if param.name == kw::SelfUpper {
+                    assert_eq!(param.index, 0);
+                    return None;
+                }
+                if synthetic {
+                    impl_trait.insert(param.index.into(), vec![]);
+                    return None;
+                }
+                Some(clean_generic_param_def(param, cx))
+            }
+            ty::GenericParamDefKind::Const { .. } => Some(clean_generic_param_def(param, cx)),
+        })
+        .collect::<Vec<GenericParamDef>>();
+
+    // param index -> [(DefId of trait, associated type name and generics, type)]
+    let mut impl_trait_proj = FxHashMap::<u32, Vec<(DefId, PathSegment, Ty<'_>)>>::default();
+
+    let where_predicates = preds
+        .predicates
+        .iter()
+        .flat_map(|(p, _)| {
+            let mut projection = None;
+            let param_idx = (|| {
+                let bound_p = p.kind();
+                match bound_p.skip_binder() {
+                    ty::PredicateKind::Trait(pred) => {
+                        if let ty::Param(param) = pred.self_ty().kind() {
+                            return Some(param.index);
+                        }
+                    }
+                    ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, _reg)) => {
+                        if let ty::Param(param) = ty.kind() {
+                            return Some(param.index);
+                        }
+                    }
+                    ty::PredicateKind::Projection(p) => {
+                        if let ty::Param(param) = p.projection_ty.self_ty().kind() {
+                            projection = Some(bound_p.rebind(p));
+                            return Some(param.index);
+                        }
+                    }
+                    _ => (),
+                }
+
+                None
+            })();
+
+            if let Some(param_idx) = param_idx {
+                if let Some(b) = impl_trait.get_mut(&param_idx.into()) {
+                    let p: WherePredicate = p.clean(cx)?;
+
+                    b.extend(
+                        p.get_bounds()
+                            .into_iter()
+                            .flatten()
+                            .cloned()
+                            .filter(|b| !b.is_sized_bound(cx)),
+                    );
+
+                    let proj = projection.map(|p| {
+                        (
+                            clean_projection(p.skip_binder().projection_ty, cx, None),
+                            p.skip_binder().term,
+                        )
+                    });
+                    if let Some(((_, trait_did, name), rhs)) = proj
+                        .as_ref()
+                        .and_then(|(lhs, rhs): &(Type, _)| Some((lhs.projection()?, rhs)))
+                    {
+                        // FIXME(...): Remove this unwrap()
+                        impl_trait_proj.entry(param_idx).or_default().push((
+                            trait_did,
+                            name,
+                            rhs.ty().unwrap(),
+                        ));
+                    }
+
+                    return None;
+                }
+            }
+
+            Some(p)
+        })
+        .collect::<Vec<_>>();
+
+    for (param, mut bounds) in impl_trait {
+        // Move trait bounds to the front.
+        bounds.sort_by_key(|b| !matches!(b, GenericBound::TraitBound(..)));
+
+        if let crate::core::ImplTraitParam::ParamIndex(idx) = param {
+            if let Some(proj) = impl_trait_proj.remove(&idx) {
+                for (trait_did, name, rhs) in proj {
+                    let rhs = clean_middle_ty(rhs, cx, None);
+                    simplify::merge_bounds(cx, &mut bounds, trait_did, name, &Term::Type(rhs));
+                }
+            }
+        } else {
+            unreachable!();
+        }
+
+        cx.impl_trait_bounds.insert(param, bounds);
+    }
+
+    // Now that `cx.impl_trait_bounds` is populated, we can process
+    // remaining predicates which could contain `impl Trait`.
+    let mut where_predicates =
+        where_predicates.into_iter().flat_map(|p| p.clean(cx)).collect::<Vec<_>>();
+
+    // Type parameters have a Sized bound by default unless removed with
+    // ?Sized. Scan through the predicates and mark any type parameter with
+    // a Sized bound, removing the bounds as we find them.
+    //
+    // Note that associated types also have a sized bound by default, but we
+    // don't actually know the set of associated types right here so that's
+    // handled in cleaning associated types
+    let mut sized_params = FxHashSet::default();
+    where_predicates.retain(|pred| match *pred {
+        WherePredicate::BoundPredicate { ty: Generic(ref g), ref bounds, .. } => {
+            if bounds.iter().any(|b| b.is_sized_bound(cx)) {
+                sized_params.insert(*g);
+                false
+            } else {
+                true
+            }
+        }
+        _ => true,
+    });
+
+    // Run through the type parameters again and insert a ?Sized
+    // unbound for any we didn't find to be Sized.
+    for tp in &stripped_params {
+        if matches!(tp.kind, types::GenericParamDefKind::Type { .. })
+            && !sized_params.contains(&tp.name)
+        {
+            where_predicates.push(WherePredicate::BoundPredicate {
+                ty: Type::Generic(tp.name),
+                bounds: vec![GenericBound::maybe_sized(cx)],
+                bound_params: Vec::new(),
+            })
+        }
+    }
+
+    // It would be nice to collect all of the bounds on a type and recombine
+    // them if possible, to avoid e.g., `where T: Foo, T: Bar, T: Sized, T: 'a`
+    // and instead see `where T: Foo + Bar + Sized + 'a`
+
+    Generics {
+        params: stripped_params,
+        where_predicates: simplify::where_clauses(cx, where_predicates),
+    }
+}
+
+fn clean_fn_or_proc_macro<'tcx>(
+    item: &hir::Item<'tcx>,
+    sig: &hir::FnSig<'tcx>,
+    generics: &hir::Generics<'tcx>,
+    body_id: hir::BodyId,
+    name: &mut Symbol,
+    cx: &mut DocContext<'tcx>,
+) -> ItemKind {
+    let attrs = cx.tcx.hir().attrs(item.hir_id());
+    let macro_kind = attrs.iter().find_map(|a| {
+        if a.has_name(sym::proc_macro) {
+            Some(MacroKind::Bang)
+        } else if a.has_name(sym::proc_macro_derive) {
+            Some(MacroKind::Derive)
+        } else if a.has_name(sym::proc_macro_attribute) {
+            Some(MacroKind::Attr)
+        } else {
+            None
+        }
+    });
+    match macro_kind {
+        Some(kind) => {
+            if kind == MacroKind::Derive {
+                *name = attrs
+                    .lists(sym::proc_macro_derive)
+                    .find_map(|mi| mi.ident())
+                    .expect("proc-macro derives require a name")
+                    .name;
+            }
+
+            let mut helpers = Vec::new();
+            for mi in attrs.lists(sym::proc_macro_derive) {
+                if !mi.has_name(sym::attributes) {
+                    continue;
+                }
+
+                if let Some(list) = mi.meta_item_list() {
+                    for inner_mi in list {
+                        if let Some(ident) = inner_mi.ident() {
+                            helpers.push(ident.name);
+                        }
+                    }
+                }
+            }
+            ProcMacroItem(ProcMacro { kind, helpers })
+        }
+        None => {
+            let mut func = clean_function(cx, sig, generics, body_id);
+            clean_fn_decl_legacy_const_generics(&mut func, attrs);
+            FunctionItem(func)
+        }
+    }
+}
+
+/// This is needed to make it more "readable" when documenting functions using
+/// `rustc_legacy_const_generics`. More information in
+/// <https://github.com/rust-lang/rust/issues/83167>.
+fn clean_fn_decl_legacy_const_generics(func: &mut Function, attrs: &[ast::Attribute]) {
+    for meta_item_list in attrs
+        .iter()
+        .filter(|a| a.has_name(sym::rustc_legacy_const_generics))
+        .filter_map(|a| a.meta_item_list())
+    {
+        for (pos, literal) in meta_item_list.iter().filter_map(|meta| meta.literal()).enumerate() {
+            match literal.kind {
+                ast::LitKind::Int(a, _) => {
+                    let gen = func.generics.params.remove(0);
+                    if let GenericParamDef { name, kind: GenericParamDefKind::Const { ty, .. } } =
+                        gen
+                    {
+                        func.decl
+                            .inputs
+                            .values
+                            .insert(a as _, Argument { name, type_: *ty, is_const: true });
+                    } else {
+                        panic!("unexpected non const in position {pos}");
+                    }
+                }
+                _ => panic!("invalid arg index"),
+            }
+        }
+    }
+}
+
+fn clean_function<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    sig: &hir::FnSig<'tcx>,
+    generics: &hir::Generics<'tcx>,
+    body_id: hir::BodyId,
+) -> Box<Function> {
+    let (generics, decl) = enter_impl_trait(cx, |cx| {
+        // NOTE: generics must be cleaned before args
+        let generics = generics.clean(cx);
+        let args = clean_args_from_types_and_body_id(cx, sig.decl.inputs, body_id);
+        let decl = clean_fn_decl_with_args(cx, sig.decl, args);
+        (generics, decl)
+    });
+    Box::new(Function { decl, generics })
+}
+
+fn clean_args_from_types_and_names<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    types: &[hir::Ty<'tcx>],
+    names: &[Ident],
+) -> Arguments {
+    Arguments {
+        values: types
+            .iter()
+            .enumerate()
+            .map(|(i, ty)| {
+                let mut name = names.get(i).map_or(kw::Empty, |ident| ident.name);
+                if name.is_empty() {
+                    name = kw::Underscore;
+                }
+                Argument { name, type_: clean_ty(ty, cx), is_const: false }
+            })
+            .collect(),
+    }
+}
+
+fn clean_args_from_types_and_body_id<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    types: &[hir::Ty<'tcx>],
+    body_id: hir::BodyId,
+) -> Arguments {
+    let body = cx.tcx.hir().body(body_id);
+
+    Arguments {
+        values: types
+            .iter()
+            .enumerate()
+            .map(|(i, ty)| Argument {
+                name: name_from_pat(body.params[i].pat),
+                type_: clean_ty(ty, cx),
+                is_const: false,
+            })
+            .collect(),
+    }
+}
+
+fn clean_fn_decl_with_args<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    decl: &hir::FnDecl<'tcx>,
+    args: Arguments,
+) -> FnDecl {
+    let output = match decl.output {
+        hir::FnRetTy::Return(typ) => Return(clean_ty(typ, cx)),
+        hir::FnRetTy::DefaultReturn(..) => DefaultReturn,
+    };
+    FnDecl { inputs: args, output, c_variadic: decl.c_variadic }
+}
+
+fn clean_fn_decl_from_did_and_sig<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    did: Option<DefId>,
+    sig: ty::PolyFnSig<'tcx>,
+) -> FnDecl {
+    let mut names = did.map_or(&[] as &[_], |did| cx.tcx.fn_arg_names(did)).iter();
+
+    // We assume all empty tuples are default return type. This theoretically can discard `-> ()`,
+    // but shouldn't change any code meaning.
+    let output = match clean_middle_ty(sig.skip_binder().output(), cx, None) {
+        Type::Tuple(inner) if inner.is_empty() => DefaultReturn,
+        ty => Return(ty),
+    };
+
+    FnDecl {
+        output,
+        c_variadic: sig.skip_binder().c_variadic,
+        inputs: Arguments {
+            values: sig
+                .skip_binder()
+                .inputs()
+                .iter()
+                .map(|t| Argument {
+                    type_: clean_middle_ty(*t, cx, None),
+                    name: names.next().map_or(kw::Empty, |i| i.name),
+                    is_const: false,
+                })
+                .collect(),
+        },
+    }
+}
+
+fn clean_trait_ref<'tcx>(trait_ref: &hir::TraitRef<'tcx>, cx: &mut DocContext<'tcx>) -> Path {
+    let path = clean_path(trait_ref.path, cx);
+    register_res(cx, path.res);
+    path
+}
+
+impl<'tcx> Clean<'tcx, PolyTrait> for hir::PolyTraitRef<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> PolyTrait {
+        PolyTrait {
+            trait_: clean_trait_ref(&self.trait_ref, cx),
+            generic_params: self
+                .bound_generic_params
+                .iter()
+                .filter(|p| !is_elided_lifetime(p))
+                .map(|x| clean_generic_param(cx, None, x))
+                .collect(),
+        }
+    }
+}
+
+impl<'tcx> Clean<'tcx, Item> for hir::TraitItem<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
+        let local_did = self.def_id.to_def_id();
+        cx.with_param_env(local_did, |cx| {
+            let inner = match self.kind {
+                hir::TraitItemKind::Const(ty, Some(default)) => AssocConstItem(
+                    clean_ty(ty, cx),
+                    ConstantKind::Local { def_id: local_did, body: default },
+                ),
+                hir::TraitItemKind::Const(ty, None) => TyAssocConstItem(clean_ty(ty, cx)),
+                hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
+                    let m = clean_function(cx, sig, self.generics, body);
+                    MethodItem(m, None)
+                }
+                hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(names)) => {
+                    let (generics, decl) = enter_impl_trait(cx, |cx| {
+                        // NOTE: generics must be cleaned before args
+                        let generics = self.generics.clean(cx);
+                        let args = clean_args_from_types_and_names(cx, sig.decl.inputs, names);
+                        let decl = clean_fn_decl_with_args(cx, sig.decl, args);
+                        (generics, decl)
+                    });
+                    TyMethodItem(Box::new(Function { decl, generics }))
+                }
+                hir::TraitItemKind::Type(bounds, Some(default)) => {
+                    let generics = enter_impl_trait(cx, |cx| self.generics.clean(cx));
+                    let bounds = bounds.iter().filter_map(|x| x.clean(cx)).collect();
+                    let item_type = clean_middle_ty(hir_ty_to_ty(cx.tcx, default), cx, None);
+                    AssocTypeItem(
+                        Box::new(Typedef {
+                            type_: clean_ty(default, cx),
+                            generics,
+                            item_type: Some(item_type),
+                        }),
+                        bounds,
+                    )
+                }
+                hir::TraitItemKind::Type(bounds, None) => {
+                    let generics = enter_impl_trait(cx, |cx| self.generics.clean(cx));
+                    let bounds = bounds.iter().filter_map(|x| x.clean(cx)).collect();
+                    TyAssocTypeItem(Box::new(generics), bounds)
+                }
+            };
+            let what_rustc_thinks =
+                Item::from_def_id_and_parts(local_did, Some(self.ident.name), inner, cx);
+            // Trait items always inherit the trait's visibility -- we don't want to show `pub`.
+            Item { visibility: Inherited, ..what_rustc_thinks }
+        })
+    }
+}
+
+impl<'tcx> Clean<'tcx, Item> for hir::ImplItem<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
+        let local_did = self.def_id.to_def_id();
+        cx.with_param_env(local_did, |cx| {
+            let inner = match self.kind {
+                hir::ImplItemKind::Const(ty, expr) => {
+                    let default = ConstantKind::Local { def_id: local_did, body: expr };
+                    AssocConstItem(clean_ty(ty, cx), default)
+                }
+                hir::ImplItemKind::Fn(ref sig, body) => {
+                    let m = clean_function(cx, sig, self.generics, body);
+                    let defaultness = cx.tcx.impl_defaultness(self.def_id);
+                    MethodItem(m, Some(defaultness))
+                }
+                hir::ImplItemKind::TyAlias(hir_ty) => {
+                    let type_ = clean_ty(hir_ty, cx);
+                    let generics = self.generics.clean(cx);
+                    let item_type = clean_middle_ty(hir_ty_to_ty(cx.tcx, hir_ty), cx, None);
+                    AssocTypeItem(
+                        Box::new(Typedef { type_, generics, item_type: Some(item_type) }),
+                        Vec::new(),
+                    )
+                }
+            };
+
+            let mut what_rustc_thinks =
+                Item::from_def_id_and_parts(local_did, Some(self.ident.name), inner, cx);
+
+            let impl_ref = cx.tcx.impl_trait_ref(cx.tcx.local_parent(self.def_id));
+
+            // Trait impl items always inherit the impl's visibility --
+            // we don't want to show `pub`.
+            if impl_ref.is_some() {
+                what_rustc_thinks.visibility = Inherited;
+            }
+
+            what_rustc_thinks
+        })
+    }
+}
+
+impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
+        let tcx = cx.tcx;
+        let kind = match self.kind {
+            ty::AssocKind::Const => {
+                let ty = clean_middle_ty(tcx.type_of(self.def_id), cx, Some(self.def_id));
+
+                let provided = match self.container {
+                    ty::ImplContainer => true,
+                    ty::TraitContainer => tcx.impl_defaultness(self.def_id).has_value(),
+                };
+                if provided {
+                    AssocConstItem(ty, ConstantKind::Extern { def_id: self.def_id })
+                } else {
+                    TyAssocConstItem(ty)
+                }
+            }
+            ty::AssocKind::Fn => {
+                let generics = clean_ty_generics(
+                    cx,
+                    tcx.generics_of(self.def_id),
+                    tcx.explicit_predicates_of(self.def_id),
+                );
+                let sig = tcx.fn_sig(self.def_id);
+                let mut decl = clean_fn_decl_from_did_and_sig(cx, Some(self.def_id), sig);
+
+                if self.fn_has_self_parameter {
+                    let self_ty = match self.container {
+                        ty::ImplContainer => tcx.type_of(self.container_id(tcx)),
+                        ty::TraitContainer => tcx.types.self_param,
+                    };
+                    let self_arg_ty = sig.input(0).skip_binder();
+                    if self_arg_ty == self_ty {
+                        decl.inputs.values[0].type_ = Generic(kw::SelfUpper);
+                    } else if let ty::Ref(_, ty, _) = *self_arg_ty.kind() {
+                        if ty == self_ty {
+                            match decl.inputs.values[0].type_ {
+                                BorrowedRef { ref mut type_, .. } => {
+                                    **type_ = Generic(kw::SelfUpper)
+                                }
+                                _ => unreachable!(),
+                            }
+                        }
+                    }
+                }
+
+                let provided = match self.container {
+                    ty::ImplContainer => true,
+                    ty::TraitContainer => self.defaultness(tcx).has_value(),
+                };
+                if provided {
+                    let defaultness = match self.container {
+                        ty::ImplContainer => Some(self.defaultness(tcx)),
+                        ty::TraitContainer => None,
+                    };
+                    MethodItem(Box::new(Function { generics, decl }), defaultness)
+                } else {
+                    TyMethodItem(Box::new(Function { generics, decl }))
+                }
+            }
+            ty::AssocKind::Type => {
+                let my_name = self.name;
+
+                fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
+                    match (&param.kind, arg) {
+                        (GenericParamDefKind::Type { .. }, GenericArg::Type(Type::Generic(ty)))
+                            if *ty == param.name =>
+                        {
+                            true
+                        }
+                        (
+                            GenericParamDefKind::Lifetime { .. },
+                            GenericArg::Lifetime(Lifetime(lt)),
+                        ) if *lt == param.name => true,
+                        (GenericParamDefKind::Const { .. }, GenericArg::Const(c)) => {
+                            match &c.kind {
+                                ConstantKind::TyConst { expr } => expr == param.name.as_str(),
+                                _ => false,
+                            }
+                        }
+                        _ => false,
+                    }
+                }
+
+                if let ty::TraitContainer = self.container {
+                    let bounds = tcx.explicit_item_bounds(self.def_id);
+                    let predicates = ty::GenericPredicates { parent: None, predicates: bounds };
+                    let mut generics =
+                        clean_ty_generics(cx, tcx.generics_of(self.def_id), predicates);
+                    // Filter out the bounds that are (likely?) directly attached to the associated type,
+                    // as opposed to being located in the where clause.
+                    let mut bounds = generics
+                        .where_predicates
+                        .drain_filter(|pred| match *pred {
+                            WherePredicate::BoundPredicate {
+                                ty: QPath { ref assoc, ref self_type, ref trait_, .. },
+                                ..
+                            } => {
+                                if assoc.name != my_name {
+                                    return false;
+                                }
+                                if trait_.def_id() != self.container_id(tcx) {
+                                    return false;
+                                }
+                                match **self_type {
+                                    Generic(ref s) if *s == kw::SelfUpper => {}
+                                    _ => return false,
+                                }
+                                match &assoc.args {
+                                    GenericArgs::AngleBracketed { args, bindings } => {
+                                        if !bindings.is_empty()
+                                            || generics
+                                                .params
+                                                .iter()
+                                                .zip(args.iter())
+                                                .any(|(param, arg)| !param_eq_arg(param, arg))
+                                        {
+                                            return false;
+                                        }
+                                    }
+                                    GenericArgs::Parenthesized { .. } => {
+                                        // The only time this happens is if we're inside the rustdoc for Fn(),
+                                        // which only has one associated type, which is not a GAT, so whatever.
+                                    }
+                                }
+                                true
+                            }
+                            _ => false,
+                        })
+                        .flat_map(|pred| {
+                            if let WherePredicate::BoundPredicate { bounds, .. } = pred {
+                                bounds
+                            } else {
+                                unreachable!()
+                            }
+                        })
+                        .collect::<Vec<_>>();
+                    // Our Sized/?Sized bound didn't get handled when creating the generics
+                    // because we didn't actually get our whole set of bounds until just now
+                    // (some of them may have come from the trait). If we do have a sized
+                    // bound, we remove it, and if we don't then we add the `?Sized` bound
+                    // at the end.
+                    match bounds.iter().position(|b| b.is_sized_bound(cx)) {
+                        Some(i) => {
+                            bounds.remove(i);
+                        }
+                        None => bounds.push(GenericBound::maybe_sized(cx)),
+                    }
+
+                    if tcx.impl_defaultness(self.def_id).has_value() {
+                        AssocTypeItem(
+                            Box::new(Typedef {
+                                type_: clean_middle_ty(
+                                    tcx.type_of(self.def_id),
+                                    cx,
+                                    Some(self.def_id),
+                                ),
+                                generics,
+                                // FIXME: should we obtain the Type from HIR and pass it on here?
+                                item_type: None,
+                            }),
+                            bounds,
+                        )
+                    } else {
+                        TyAssocTypeItem(Box::new(generics), bounds)
+                    }
+                } else {
+                    // FIXME: when could this happen? Associated items in inherent impls?
+                    AssocTypeItem(
+                        Box::new(Typedef {
+                            type_: clean_middle_ty(tcx.type_of(self.def_id), cx, Some(self.def_id)),
+                            generics: Generics { params: Vec::new(), where_predicates: Vec::new() },
+                            item_type: None,
+                        }),
+                        Vec::new(),
+                    )
+                }
+            }
+        };
+
+        let mut what_rustc_thinks =
+            Item::from_def_id_and_parts(self.def_id, Some(self.name), kind, cx);
+
+        let impl_ref = tcx.impl_trait_ref(tcx.parent(self.def_id));
+
+        // Trait impl items always inherit the impl's visibility --
+        // we don't want to show `pub`.
+        if impl_ref.is_some() {
+            what_rustc_thinks.visibility = Visibility::Inherited;
+        }
+
+        what_rustc_thinks
+    }
+}
+
+fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
+    let hir::Ty { hir_id: _, span, ref kind } = *hir_ty;
+    let hir::TyKind::Path(qpath) = kind else { unreachable!() };
+
+    match qpath {
+        hir::QPath::Resolved(None, path) => {
+            if let Res::Def(DefKind::TyParam, did) = path.res {
+                if let Some(new_ty) = cx.substs.get(&did).and_then(|p| p.as_ty()).cloned() {
+                    return new_ty;
+                }
+                if let Some(bounds) = cx.impl_trait_bounds.remove(&did.into()) {
+                    return ImplTrait(bounds);
+                }
+            }
+
+            if let Some(expanded) = maybe_expand_private_type_alias(cx, path) {
+                expanded
+            } else {
+                let path = clean_path(path, cx);
+                resolve_type(cx, path)
+            }
+        }
+        hir::QPath::Resolved(Some(qself), p) => {
+            // Try to normalize `<X as Y>::T` to a type
+            let ty = hir_ty_to_ty(cx.tcx, hir_ty);
+            if let Some(normalized_value) = normalize(cx, ty) {
+                return clean_middle_ty(normalized_value, cx, None);
+            }
+
+            let trait_segments = &p.segments[..p.segments.len() - 1];
+            let trait_def = cx.tcx.associated_item(p.res.def_id()).container_id(cx.tcx);
+            let trait_ = self::Path {
+                res: Res::Def(DefKind::Trait, trait_def),
+                segments: trait_segments.iter().map(|x| x.clean(cx)).collect(),
+            };
+            register_res(cx, trait_.res);
+            let self_def_id = DefId::local(qself.hir_id.owner.local_def_index);
+            let self_type = clean_ty(qself, cx);
+            let should_show_cast = compute_should_show_cast(Some(self_def_id), &trait_, &self_type);
+            Type::QPath {
+                assoc: Box::new(p.segments.last().expect("segments were empty").clean(cx)),
+                should_show_cast,
+                self_type: Box::new(self_type),
+                trait_,
+            }
+        }
+        hir::QPath::TypeRelative(qself, segment) => {
+            let ty = hir_ty_to_ty(cx.tcx, hir_ty);
+            let res = match ty.kind() {
+                ty::Projection(proj) => Res::Def(DefKind::Trait, proj.trait_ref(cx.tcx).def_id),
+                // Rustdoc handles `ty::Error`s by turning them into `Type::Infer`s.
+                ty::Error(_) => return Type::Infer,
+                _ => bug!("clean: expected associated type, found `{:?}`", ty),
+            };
+            let trait_ = clean_path(&hir::Path { span, res, segments: &[] }, cx);
+            register_res(cx, trait_.res);
+            let self_def_id = res.opt_def_id();
+            let self_type = clean_ty(qself, cx);
+            let should_show_cast = compute_should_show_cast(self_def_id, &trait_, &self_type);
+            Type::QPath {
+                assoc: Box::new(segment.clean(cx)),
+                should_show_cast,
+                self_type: Box::new(self_type),
+                trait_,
+            }
+        }
+        hir::QPath::LangItem(..) => bug!("clean: requiring documentation of lang item"),
+    }
+}
+
+fn maybe_expand_private_type_alias<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    path: &hir::Path<'tcx>,
+) -> Option<Type> {
+    let Res::Def(DefKind::TyAlias, def_id) = path.res else { return None };
+    // Substitute private type aliases
+    let def_id = def_id.as_local()?;
+    let alias = if !cx.cache.access_levels.is_exported(def_id.to_def_id()) {
+        &cx.tcx.hir().expect_item(def_id).kind
+    } else {
+        return None;
+    };
+    let hir::ItemKind::TyAlias(ty, generics) = alias else { return None };
+
+    let provided_params = &path.segments.last().expect("segments were empty");
+    let mut substs = FxHashMap::default();
+    let generic_args = provided_params.args();
+
+    let mut indices: hir::GenericParamCount = Default::default();
+    for param in generics.params.iter() {
+        match param.kind {
+            hir::GenericParamKind::Lifetime { .. } => {
+                let mut j = 0;
+                let lifetime = generic_args.args.iter().find_map(|arg| match arg {
+                    hir::GenericArg::Lifetime(lt) => {
+                        if indices.lifetimes == j {
+                            return Some(lt);
+                        }
+                        j += 1;
+                        None
+                    }
+                    _ => None,
+                });
+                if let Some(lt) = lifetime.cloned() {
+                    let lt_def_id = cx.tcx.hir().local_def_id(param.hir_id);
+                    let cleaned =
+                        if !lt.is_elided() { clean_lifetime(lt, cx) } else { Lifetime::elided() };
+                    substs.insert(lt_def_id.to_def_id(), SubstParam::Lifetime(cleaned));
+                }
+                indices.lifetimes += 1;
+            }
+            hir::GenericParamKind::Type { ref default, .. } => {
+                let ty_param_def_id = cx.tcx.hir().local_def_id(param.hir_id);
+                let mut j = 0;
+                let type_ = generic_args.args.iter().find_map(|arg| match arg {
+                    hir::GenericArg::Type(ty) => {
+                        if indices.types == j {
+                            return Some(ty);
+                        }
+                        j += 1;
+                        None
+                    }
+                    _ => None,
+                });
+                if let Some(ty) = type_ {
+                    substs.insert(ty_param_def_id.to_def_id(), SubstParam::Type(clean_ty(ty, cx)));
+                } else if let Some(default) = *default {
+                    substs.insert(
+                        ty_param_def_id.to_def_id(),
+                        SubstParam::Type(clean_ty(default, cx)),
+                    );
+                }
+                indices.types += 1;
+            }
+            hir::GenericParamKind::Const { .. } => {
+                let const_param_def_id = cx.tcx.hir().local_def_id(param.hir_id);
+                let mut j = 0;
+                let const_ = generic_args.args.iter().find_map(|arg| match arg {
+                    hir::GenericArg::Const(ct) => {
+                        if indices.consts == j {
+                            return Some(ct);
+                        }
+                        j += 1;
+                        None
+                    }
+                    _ => None,
+                });
+                if let Some(ct) = const_ {
+                    substs.insert(
+                        const_param_def_id.to_def_id(),
+                        SubstParam::Constant(clean_const(ct, cx)),
+                    );
+                }
+                // FIXME(const_generics_defaults)
+                indices.consts += 1;
+            }
+        }
+    }
+
+    Some(cx.enter_alias(substs, |cx| clean_ty(ty, cx)))
+}
+
+pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
+    use rustc_hir::*;
+
+    match ty.kind {
+        TyKind::Never => Primitive(PrimitiveType::Never),
+        TyKind::Ptr(ref m) => RawPointer(m.mutbl, Box::new(clean_ty(m.ty, cx))),
+        TyKind::Rptr(ref l, ref m) => {
+            // There are two times a `Fresh` lifetime can be created:
+            // 1. For `&'_ x`, written by the user. This corresponds to `lower_lifetime` in `rustc_ast_lowering`.
+            // 2. For `&x` as a parameter to an `async fn`. This corresponds to `elided_ref_lifetime in `rustc_ast_lowering`.
+            //    See #59286 for more information.
+            // Ideally we would only hide the `'_` for case 2., but I don't know a way to distinguish it.
+            // Turning `fn f(&'_ self)` into `fn f(&self)` isn't the worst thing in the world, though;
+            // there's no case where it could cause the function to fail to compile.
+            let elided =
+                l.is_elided() || matches!(l.name, LifetimeName::Param(_, ParamName::Fresh));
+            let lifetime = if elided { None } else { Some(clean_lifetime(*l, cx)) };
+            BorrowedRef { lifetime, mutability: m.mutbl, type_: Box::new(clean_ty(m.ty, cx)) }
+        }
+        TyKind::Slice(ty) => Slice(Box::new(clean_ty(ty, cx))),
+        TyKind::Array(ty, ref length) => {
+            let length = match length {
+                hir::ArrayLen::Infer(_, _) => "_".to_string(),
+                hir::ArrayLen::Body(anon_const) => {
+                    let def_id = cx.tcx.hir().local_def_id(anon_const.hir_id);
+                    // NOTE(min_const_generics): We can't use `const_eval_poly` for constants
+                    // as we currently do not supply the parent generics to anonymous constants
+                    // but do allow `ConstKind::Param`.
+                    //
+                    // `const_eval_poly` tries to to first substitute generic parameters which
+                    // results in an ICE while manually constructing the constant and using `eval`
+                    // does nothing for `ConstKind::Param`.
+                    let ct = ty::Const::from_anon_const(cx.tcx, def_id);
+                    let param_env = cx.tcx.param_env(def_id);
+                    print_const(cx, ct.eval(cx.tcx, param_env))
+                }
+            };
+
+            Array(Box::new(clean_ty(ty, cx)), length)
+        }
+        TyKind::Tup(tys) => Tuple(tys.iter().map(|ty| clean_ty(ty, cx)).collect()),
+        TyKind::OpaqueDef(item_id, _) => {
+            let item = cx.tcx.hir().item(item_id);
+            if let hir::ItemKind::OpaqueTy(ref ty) = item.kind {
+                ImplTrait(ty.bounds.iter().filter_map(|x| x.clean(cx)).collect())
+            } else {
+                unreachable!()
+            }
+        }
+        TyKind::Path(_) => clean_qpath(ty, cx),
+        TyKind::TraitObject(bounds, ref lifetime, _) => {
+            let bounds = bounds.iter().map(|bound| bound.clean(cx)).collect();
+            let lifetime =
+                if !lifetime.is_elided() { Some(clean_lifetime(*lifetime, cx)) } else { None };
+            DynTrait(bounds, lifetime)
+        }
+        TyKind::BareFn(barefn) => BareFunction(Box::new(barefn.clean(cx))),
+        // Rustdoc handles `TyKind::Err`s by turning them into `Type::Infer`s.
+        TyKind::Infer | TyKind::Err => Infer,
+        TyKind::Typeof(..) => panic!("unimplemented type {:?}", ty.kind),
+    }
+}
+
+/// Returns `None` if the type could not be normalized
+fn normalize<'tcx>(cx: &mut DocContext<'tcx>, ty: Ty<'_>) -> Option<Ty<'tcx>> {
+    // HACK: low-churn fix for #79459 while we wait for a trait normalization fix
+    if !cx.tcx.sess.opts.unstable_opts.normalize_docs {
+        return None;
+    }
+
+    use crate::rustc_trait_selection::infer::TyCtxtInferExt;
+    use crate::rustc_trait_selection::traits::query::normalize::AtExt;
+    use rustc_middle::traits::ObligationCause;
+
+    // Try to normalize `<X as Y>::T` to a type
+    let lifted = ty.lift_to_tcx(cx.tcx).unwrap();
+    let normalized = cx.tcx.infer_ctxt().enter(|infcx| {
+        infcx
+            .at(&ObligationCause::dummy(), cx.param_env)
+            .normalize(lifted)
+            .map(|resolved| infcx.resolve_vars_if_possible(resolved.value))
+    });
+    match normalized {
+        Ok(normalized_value) => {
+            debug!("normalized {:?} to {:?}", ty, normalized_value);
+            Some(normalized_value)
+        }
+        Err(err) => {
+            debug!("failed to normalize {:?}: {:?}", ty, err);
+            None
+        }
+    }
+}
+
+pub(crate) fn clean_middle_ty<'tcx>(
+    this: Ty<'tcx>,
+    cx: &mut DocContext<'tcx>,
+    def_id: Option<DefId>,
+) -> Type {
+    trace!("cleaning type: {:?}", this);
+    let ty = normalize(cx, this).unwrap_or(this);
+    match *ty.kind() {
+        ty::Never => Primitive(PrimitiveType::Never),
+        ty::Bool => Primitive(PrimitiveType::Bool),
+        ty::Char => Primitive(PrimitiveType::Char),
+        ty::Int(int_ty) => Primitive(int_ty.into()),
+        ty::Uint(uint_ty) => Primitive(uint_ty.into()),
+        ty::Float(float_ty) => Primitive(float_ty.into()),
+        ty::Str => Primitive(PrimitiveType::Str),
+        ty::Slice(ty) => Slice(Box::new(clean_middle_ty(ty, cx, None))),
+        ty::Array(ty, n) => {
+            let mut n = cx.tcx.lift(n).expect("array lift failed");
+            n = n.eval(cx.tcx, ty::ParamEnv::reveal_all());
+            let n = print_const(cx, n);
+            Array(Box::new(clean_middle_ty(ty, cx, None)), n)
+        }
+        ty::RawPtr(mt) => RawPointer(mt.mutbl, Box::new(clean_middle_ty(mt.ty, cx, None))),
+        ty::Ref(r, ty, mutbl) => BorrowedRef {
+            lifetime: clean_middle_region(r),
+            mutability: mutbl,
+            type_: Box::new(clean_middle_ty(ty, cx, None)),
+        },
+        ty::FnDef(..) | ty::FnPtr(_) => {
+            let ty = cx.tcx.lift(this).expect("FnPtr lift failed");
+            let sig = ty.fn_sig(cx.tcx);
+            let decl = clean_fn_decl_from_did_and_sig(cx, None, sig);
+            BareFunction(Box::new(BareFunctionDecl {
+                unsafety: sig.unsafety(),
+                generic_params: Vec::new(),
+                decl,
+                abi: sig.abi(),
+            }))
+        }
+        ty::Adt(def, substs) => {
+            let did = def.did();
+            let kind = match def.adt_kind() {
+                AdtKind::Struct => ItemType::Struct,
+                AdtKind::Union => ItemType::Union,
+                AdtKind::Enum => ItemType::Enum,
+            };
+            inline::record_extern_fqn(cx, did, kind);
+            let path = external_path(cx, did, false, vec![], substs);
+            Type::Path { path }
+        }
+        ty::Foreign(did) => {
+            inline::record_extern_fqn(cx, did, ItemType::ForeignType);
+            let path = external_path(cx, did, false, vec![], InternalSubsts::empty());
+            Type::Path { path }
+        }
+        ty::Dynamic(obj, ref reg) => {
+            // HACK: pick the first `did` as the `did` of the trait object. Someone
+            // might want to implement "native" support for marker-trait-only
+            // trait objects.
+            let mut dids = obj.principal_def_id().into_iter().chain(obj.auto_traits());
+            let did = dids
+                .next()
+                .unwrap_or_else(|| panic!("found trait object `{:?}` with no traits?", this));
+            let substs = match obj.principal() {
+                Some(principal) => principal.skip_binder().substs,
+                // marker traits have no substs.
+                _ => cx.tcx.intern_substs(&[]),
+            };
+
+            inline::record_extern_fqn(cx, did, ItemType::Trait);
+
+            let lifetime = clean_middle_region(*reg);
+            let mut bounds = vec![];
+
+            for did in dids {
+                let empty = cx.tcx.intern_substs(&[]);
+                let path = external_path(cx, did, false, vec![], empty);
+                inline::record_extern_fqn(cx, did, ItemType::Trait);
+                let bound = PolyTrait { trait_: path, generic_params: Vec::new() };
+                bounds.push(bound);
+            }
+
+            let mut bindings = vec![];
+            for pb in obj.projection_bounds() {
+                bindings.push(TypeBinding {
+                    assoc: projection_to_path_segment(
+                        pb.skip_binder()
+                            .lift_to_tcx(cx.tcx)
+                            .unwrap()
+                            // HACK(compiler-errors): Doesn't actually matter what self
+                            // type we put here, because we're only using the GAT's substs.
+                            .with_self_ty(cx.tcx, cx.tcx.types.self_param)
+                            .projection_ty,
+                        cx,
+                    ),
+                    kind: TypeBindingKind::Equality {
+                        term: clean_middle_term(pb.skip_binder().term, cx),
+                    },
+                });
+            }
+
+            let path = external_path(cx, did, false, bindings, substs);
+            bounds.insert(0, PolyTrait { trait_: path, generic_params: Vec::new() });
+
+            DynTrait(bounds, lifetime)
+        }
+        ty::Tuple(t) => Tuple(t.iter().map(|t| clean_middle_ty(t, cx, None)).collect()),
+
+        ty::Projection(ref data) => clean_projection(*data, cx, def_id),
+
+        ty::Param(ref p) => {
+            if let Some(bounds) = cx.impl_trait_bounds.remove(&p.index.into()) {
+                ImplTrait(bounds)
+            } else {
+                Generic(p.name)
+            }
+        }
+
+        ty::Opaque(def_id, substs) => {
+            // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
+            // by looking up the bounds associated with the def_id.
+            let substs = cx.tcx.lift(substs).expect("Opaque lift failed");
+            let bounds = cx
+                .tcx
+                .explicit_item_bounds(def_id)
+                .iter()
+                .map(|(bound, _)| EarlyBinder(*bound).subst(cx.tcx, substs))
+                .collect::<Vec<_>>();
+            let mut regions = vec![];
+            let mut has_sized = false;
+            let mut bounds = bounds
+                .iter()
+                .filter_map(|bound| {
+                    let bound_predicate = bound.kind();
+                    let trait_ref = match bound_predicate.skip_binder() {
+                        ty::PredicateKind::Trait(tr) => bound_predicate.rebind(tr.trait_ref),
+                        ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(_ty, reg)) => {
+                            if let Some(r) = clean_middle_region(reg) {
+                                regions.push(GenericBound::Outlives(r));
+                            }
+                            return None;
+                        }
+                        _ => return None,
+                    };
+
+                    if let Some(sized) = cx.tcx.lang_items().sized_trait() {
+                        if trait_ref.def_id() == sized {
+                            has_sized = true;
+                            return None;
+                        }
+                    }
+
+                    let bindings: Vec<_> = bounds
+                        .iter()
+                        .filter_map(|bound| {
+                            if let ty::PredicateKind::Projection(proj) = bound.kind().skip_binder()
+                            {
+                                if proj.projection_ty.trait_ref(cx.tcx) == trait_ref.skip_binder() {
+                                    Some(TypeBinding {
+                                        assoc: projection_to_path_segment(proj.projection_ty, cx),
+                                        kind: TypeBindingKind::Equality {
+                                            term: clean_middle_term(proj.term, cx),
+                                        },
+                                    })
+                                } else {
+                                    None
+                                }
+                            } else {
+                                None
+                            }
+                        })
+                        .collect();
+
+                    Some(clean_poly_trait_ref_with_bindings(cx, trait_ref, &bindings))
+                })
+                .collect::<Vec<_>>();
+            bounds.extend(regions);
+            if !has_sized && !bounds.is_empty() {
+                bounds.insert(0, GenericBound::maybe_sized(cx));
+            }
+            ImplTrait(bounds)
+        }
+
+        ty::Closure(..) => panic!("Closure"),
+        ty::Generator(..) => panic!("Generator"),
+        ty::Bound(..) => panic!("Bound"),
+        ty::Placeholder(..) => panic!("Placeholder"),
+        ty::GeneratorWitness(..) => panic!("GeneratorWitness"),
+        ty::Infer(..) => panic!("Infer"),
+        ty::Error(_) => panic!("Error"),
+    }
+}
+
+pub(crate) fn clean_field<'tcx>(field: &hir::FieldDef<'tcx>, cx: &mut DocContext<'tcx>) -> Item {
+    let def_id = cx.tcx.hir().local_def_id(field.hir_id).to_def_id();
+    clean_field_with_def_id(def_id, field.ident.name, clean_ty(field.ty, cx), cx)
+}
+
+pub(crate) fn clean_middle_field<'tcx>(field: &ty::FieldDef, cx: &mut DocContext<'tcx>) -> Item {
+    clean_field_with_def_id(
+        field.did,
+        field.name,
+        clean_middle_ty(cx.tcx.type_of(field.did), cx, Some(field.did)),
+        cx,
+    )
+}
+
+pub(crate) fn clean_field_with_def_id(
+    def_id: DefId,
+    name: Symbol,
+    ty: Type,
+    cx: &mut DocContext<'_>,
+) -> Item {
+    let what_rustc_thinks =
+        Item::from_def_id_and_parts(def_id, Some(name), StructFieldItem(ty), cx);
+    if is_field_vis_inherited(cx.tcx, def_id) {
+        // Variant fields inherit their enum's visibility.
+        Item { visibility: Visibility::Inherited, ..what_rustc_thinks }
+    } else {
+        what_rustc_thinks
+    }
+}
+
+fn is_field_vis_inherited(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
+    let parent = tcx.parent(def_id);
+    match tcx.def_kind(parent) {
+        DefKind::Struct | DefKind::Union => false,
+        DefKind::Variant => true,
+        parent_kind => panic!("unexpected parent kind: {:?}", parent_kind),
+    }
+}
+
+pub(crate) fn clean_visibility(vis: ty::Visibility) -> Visibility {
+    match vis {
+        ty::Visibility::Public => Visibility::Public,
+        // NOTE: this is not quite right: `ty` uses `Invisible` to mean 'private',
+        // while rustdoc really does mean inherited. That means that for enum variants, such as
+        // `pub enum E { V }`, `V` will be marked as `Public` by `ty`, but as `Inherited` by rustdoc.
+        // Various parts of clean override `tcx.visibility` explicitly to make sure this distinction is captured.
+        ty::Visibility::Invisible => Visibility::Inherited,
+        ty::Visibility::Restricted(module) => Visibility::Restricted(module),
+    }
+}
+
+pub(crate) fn clean_variant_def<'tcx>(variant: &ty::VariantDef, cx: &mut DocContext<'tcx>) -> Item {
+    let kind = match variant.ctor_kind {
+        CtorKind::Const => Variant::CLike,
+        CtorKind::Fn => Variant::Tuple(
+            variant.fields.iter().map(|field| clean_middle_field(field, cx)).collect(),
+        ),
+        CtorKind::Fictive => Variant::Struct(VariantStruct {
+            struct_type: CtorKind::Fictive,
+            fields: variant.fields.iter().map(|field| clean_middle_field(field, cx)).collect(),
+        }),
+    };
+    let what_rustc_thinks =
+        Item::from_def_id_and_parts(variant.def_id, Some(variant.name), VariantItem(kind), cx);
+    // don't show `pub` for variants, which always inherit visibility
+    Item { visibility: Inherited, ..what_rustc_thinks }
+}
+
+fn clean_variant_data<'tcx>(
+    variant: &hir::VariantData<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> Variant {
+    match variant {
+        hir::VariantData::Struct(..) => Variant::Struct(VariantStruct {
+            struct_type: CtorKind::from_hir(variant),
+            fields: variant.fields().iter().map(|x| clean_field(x, cx)).collect(),
+        }),
+        hir::VariantData::Tuple(..) => {
+            Variant::Tuple(variant.fields().iter().map(|x| clean_field(x, cx)).collect())
+        }
+        hir::VariantData::Unit(..) => Variant::CLike,
+    }
+}
+
+fn clean_path<'tcx>(path: &hir::Path<'tcx>, cx: &mut DocContext<'tcx>) -> Path {
+    Path { res: path.res, segments: path.segments.iter().map(|x| x.clean(cx)).collect() }
+}
+
+impl<'tcx> Clean<'tcx, GenericArgs> for hir::GenericArgs<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> GenericArgs {
+        if self.parenthesized {
+            let output = clean_ty(self.bindings[0].ty(), cx);
+            let output =
+                if output != Type::Tuple(Vec::new()) { Some(Box::new(output)) } else { None };
+            let inputs = self.inputs().iter().map(|x| clean_ty(x, cx)).collect::<Vec<_>>().into();
+            GenericArgs::Parenthesized { inputs, output }
+        } else {
+            let args = self
+                .args
+                .iter()
+                .map(|arg| match arg {
+                    hir::GenericArg::Lifetime(lt) if !lt.is_elided() => {
+                        GenericArg::Lifetime(clean_lifetime(*lt, cx))
+                    }
+                    hir::GenericArg::Lifetime(_) => GenericArg::Lifetime(Lifetime::elided()),
+                    hir::GenericArg::Type(ty) => GenericArg::Type(clean_ty(ty, cx)),
+                    hir::GenericArg::Const(ct) => GenericArg::Const(Box::new(clean_const(ct, cx))),
+                    hir::GenericArg::Infer(_inf) => GenericArg::Infer,
+                })
+                .collect::<Vec<_>>()
+                .into();
+            let bindings =
+                self.bindings.iter().map(|x| clean_type_binding(x, cx)).collect::<Vec<_>>().into();
+            GenericArgs::AngleBracketed { args, bindings }
+        }
+    }
+}
+
+impl<'tcx> Clean<'tcx, PathSegment> for hir::PathSegment<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> PathSegment {
+        PathSegment { name: self.ident.name, args: self.args().clean(cx) }
+    }
+}
+
+impl<'tcx> Clean<'tcx, BareFunctionDecl> for hir::BareFnTy<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> BareFunctionDecl {
+        let (generic_params, decl) = enter_impl_trait(cx, |cx| {
+            // NOTE: generics must be cleaned before args
+            let generic_params = self
+                .generic_params
+                .iter()
+                .filter(|p| !is_elided_lifetime(p))
+                .map(|x| clean_generic_param(cx, None, x))
+                .collect();
+            let args = clean_args_from_types_and_names(cx, self.decl.inputs, self.param_names);
+            let decl = clean_fn_decl_with_args(cx, self.decl, args);
+            (generic_params, decl)
+        });
+        BareFunctionDecl { unsafety: self.unsafety, abi: self.abi, decl, generic_params }
+    }
+}
+
+fn clean_maybe_renamed_item<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    item: &hir::Item<'tcx>,
+    renamed: Option<Symbol>,
+) -> Vec<Item> {
+    use hir::ItemKind;
+
+    let def_id = item.def_id.to_def_id();
+    let mut name = renamed.unwrap_or_else(|| cx.tcx.hir().name(item.hir_id()));
+    cx.with_param_env(def_id, |cx| {
+        let kind = match item.kind {
+            ItemKind::Static(ty, mutability, body_id) => {
+                StaticItem(Static { type_: clean_ty(ty, cx), mutability, expr: Some(body_id) })
+            }
+            ItemKind::Const(ty, body_id) => ConstantItem(Constant {
+                type_: clean_ty(ty, cx),
+                kind: ConstantKind::Local { body: body_id, def_id },
+            }),
+            ItemKind::OpaqueTy(ref ty) => OpaqueTyItem(OpaqueTy {
+                bounds: ty.bounds.iter().filter_map(|x| x.clean(cx)).collect(),
+                generics: ty.generics.clean(cx),
+            }),
+            ItemKind::TyAlias(hir_ty, generics) => {
+                let rustdoc_ty = clean_ty(hir_ty, cx);
+                let ty = clean_middle_ty(hir_ty_to_ty(cx.tcx, hir_ty), cx, None);
+                TypedefItem(Box::new(Typedef {
+                    type_: rustdoc_ty,
+                    generics: generics.clean(cx),
+                    item_type: Some(ty),
+                }))
+            }
+            ItemKind::Enum(ref def, generics) => EnumItem(Enum {
+                variants: def.variants.iter().map(|v| v.clean(cx)).collect(),
+                generics: generics.clean(cx),
+            }),
+            ItemKind::TraitAlias(generics, bounds) => TraitAliasItem(TraitAlias {
+                generics: generics.clean(cx),
+                bounds: bounds.iter().filter_map(|x| x.clean(cx)).collect(),
+            }),
+            ItemKind::Union(ref variant_data, generics) => UnionItem(Union {
+                generics: generics.clean(cx),
+                fields: variant_data.fields().iter().map(|x| clean_field(x, cx)).collect(),
+            }),
+            ItemKind::Struct(ref variant_data, generics) => StructItem(Struct {
+                struct_type: CtorKind::from_hir(variant_data),
+                generics: generics.clean(cx),
+                fields: variant_data.fields().iter().map(|x| clean_field(x, cx)).collect(),
+            }),
+            ItemKind::Impl(impl_) => return clean_impl(impl_, item.hir_id(), cx),
+            // proc macros can have a name set by attributes
+            ItemKind::Fn(ref sig, generics, body_id) => {
+                clean_fn_or_proc_macro(item, sig, generics, body_id, &mut name, cx)
+            }
+            ItemKind::Macro(ref macro_def, _) => {
+                let ty_vis = clean_visibility(cx.tcx.visibility(def_id));
+                MacroItem(Macro {
+                    source: display_macro_source(cx, name, macro_def, def_id, ty_vis),
+                })
+            }
+            ItemKind::Trait(_, _, generics, bounds, item_ids) => {
+                let items =
+                    item_ids.iter().map(|ti| cx.tcx.hir().trait_item(ti.id).clean(cx)).collect();
+
+                TraitItem(Trait {
+                    def_id,
+                    items,
+                    generics: generics.clean(cx),
+                    bounds: bounds.iter().filter_map(|x| x.clean(cx)).collect(),
+                })
+            }
+            ItemKind::ExternCrate(orig_name) => {
+                return clean_extern_crate(item, name, orig_name, cx);
+            }
+            ItemKind::Use(path, kind) => {
+                return clean_use_statement(item, name, path, kind, cx, &mut FxHashSet::default());
+            }
+            _ => unreachable!("not yet converted"),
+        };
+
+        vec![Item::from_def_id_and_parts(def_id, Some(name), kind, cx)]
+    })
+}
+
+impl<'tcx> Clean<'tcx, Item> for hir::Variant<'tcx> {
+    fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
+        let kind = VariantItem(clean_variant_data(&self.data, cx));
+        let what_rustc_thinks =
+            Item::from_hir_id_and_parts(self.id, Some(self.ident.name), kind, cx);
+        // don't show `pub` for variants, which are always public
+        Item { visibility: Inherited, ..what_rustc_thinks }
+    }
+}
+
+fn clean_impl<'tcx>(
+    impl_: &hir::Impl<'tcx>,
+    hir_id: hir::HirId,
+    cx: &mut DocContext<'tcx>,
+) -> Vec<Item> {
+    let tcx = cx.tcx;
+    let mut ret = Vec::new();
+    let trait_ = impl_.of_trait.as_ref().map(|t| clean_trait_ref(t, cx));
+    let items =
+        impl_.items.iter().map(|ii| tcx.hir().impl_item(ii.id).clean(cx)).collect::<Vec<_>>();
+    let def_id = tcx.hir().local_def_id(hir_id);
+
+    // If this impl block is an implementation of the Deref trait, then we
+    // need to try inlining the target's inherent impl blocks as well.
+    if trait_.as_ref().map(|t| t.def_id()) == tcx.lang_items().deref_trait() {
+        build_deref_target_impls(cx, &items, &mut ret);
+    }
+
+    let for_ = clean_ty(impl_.self_ty, cx);
+    let type_alias = for_.def_id(&cx.cache).and_then(|did| match tcx.def_kind(did) {
+        DefKind::TyAlias => Some(clean_middle_ty(tcx.type_of(did), cx, Some(did))),
+        _ => None,
+    });
+    let mut make_item = |trait_: Option<Path>, for_: Type, items: Vec<Item>| {
+        let kind = ImplItem(Box::new(Impl {
+            unsafety: impl_.unsafety,
+            generics: impl_.generics.clean(cx),
+            trait_,
+            for_,
+            items,
+            polarity: tcx.impl_polarity(def_id),
+            kind: if utils::has_doc_flag(tcx, def_id.to_def_id(), sym::fake_variadic) {
+                ImplKind::FakeVaradic
+            } else {
+                ImplKind::Normal
+            },
+        }));
+        Item::from_hir_id_and_parts(hir_id, None, kind, cx)
+    };
+    if let Some(type_alias) = type_alias {
+        ret.push(make_item(trait_.clone(), type_alias, items.clone()));
+    }
+    ret.push(make_item(trait_, for_, items));
+    ret
+}
+
+fn clean_extern_crate<'tcx>(
+    krate: &hir::Item<'tcx>,
+    name: Symbol,
+    orig_name: Option<Symbol>,
+    cx: &mut DocContext<'tcx>,
+) -> Vec<Item> {
+    // this is the ID of the `extern crate` statement
+    let cnum = cx.tcx.extern_mod_stmt_cnum(krate.def_id).unwrap_or(LOCAL_CRATE);
+    // this is the ID of the crate itself
+    let crate_def_id = cnum.as_def_id();
+    let attrs = cx.tcx.hir().attrs(krate.hir_id());
+    let ty_vis = cx.tcx.visibility(krate.def_id);
+    let please_inline = ty_vis.is_public()
+        && attrs.iter().any(|a| {
+            a.has_name(sym::doc)
+                && match a.meta_item_list() {
+                    Some(l) => attr::list_contains_name(&l, sym::inline),
+                    None => false,
+                }
+        });
+
+    if please_inline {
+        let mut visited = FxHashSet::default();
+
+        let res = Res::Def(DefKind::Mod, crate_def_id);
+
+        if let Some(items) = inline::try_inline(
+            cx,
+            cx.tcx.parent_module(krate.hir_id()).to_def_id(),
+            Some(krate.def_id.to_def_id()),
+            res,
+            name,
+            Some(attrs),
+            &mut visited,
+        ) {
+            return items;
+        }
+    }
+
+    // FIXME: using `from_def_id_and_kind` breaks `rustdoc/masked` for some reason
+    vec![Item {
+        name: Some(name),
+        attrs: Box::new(Attributes::from_ast(attrs)),
+        item_id: crate_def_id.into(),
+        visibility: clean_visibility(ty_vis),
+        kind: Box::new(ExternCrateItem { src: orig_name }),
+        cfg: attrs.cfg(cx.tcx, &cx.cache.hidden_cfg),
+    }]
+}
+
+fn clean_use_statement<'tcx>(
+    import: &hir::Item<'tcx>,
+    name: Symbol,
+    path: &hir::Path<'tcx>,
+    kind: hir::UseKind,
+    cx: &mut DocContext<'tcx>,
+    inlined_names: &mut FxHashSet<(ItemType, Symbol)>,
+) -> Vec<Item> {
+    // We need this comparison because some imports (for std types for example)
+    // are "inserted" as well but directly by the compiler and they should not be
+    // taken into account.
+    if import.span.ctxt().outer_expn_data().kind == ExpnKind::AstPass(AstPass::StdImports) {
+        return Vec::new();
+    }
+
+    let visibility = cx.tcx.visibility(import.def_id);
+    let attrs = cx.tcx.hir().attrs(import.hir_id());
+    let inline_attr = attrs.lists(sym::doc).get_word_attr(sym::inline);
+    let pub_underscore = visibility.is_public() && name == kw::Underscore;
+    let current_mod = cx.tcx.parent_module_from_def_id(import.def_id);
+
+    // The parent of the module in which this import resides. This
+    // is the same as `current_mod` if that's already the top
+    // level module.
+    let parent_mod = cx.tcx.parent_module_from_def_id(current_mod);
+
+    // This checks if the import can be seen from a higher level module.
+    // In other words, it checks if the visibility is the equivalent of
+    // `pub(super)` or higher. If the current module is the top level
+    // module, there isn't really a parent module, which makes the results
+    // meaningless. In this case, we make sure the answer is `false`.
+    let is_visible_from_parent_mod = visibility.is_accessible_from(parent_mod.to_def_id(), cx.tcx)
+        && !current_mod.is_top_level_module();
+
+    if pub_underscore {
+        if let Some(ref inline) = inline_attr {
+            rustc_errors::struct_span_err!(
+                cx.tcx.sess,
+                inline.span(),
+                E0780,
+                "anonymous imports cannot be inlined"
+            )
+            .span_label(import.span, "anonymous import")
+            .emit();
+        }
+    }
+
+    // We consider inlining the documentation of `pub use` statements, but we
+    // forcefully don't inline if this is not public or if the
+    // #[doc(no_inline)] attribute is present.
+    // Don't inline doc(hidden) imports so they can be stripped at a later stage.
+    let mut denied = cx.output_format.is_json()
+        || !(visibility.is_public()
+            || (cx.render_options.document_private && is_visible_from_parent_mod))
+        || pub_underscore
+        || attrs.iter().any(|a| {
+            a.has_name(sym::doc)
+                && match a.meta_item_list() {
+                    Some(l) => {
+                        attr::list_contains_name(&l, sym::no_inline)
+                            || attr::list_contains_name(&l, sym::hidden)
+                    }
+                    None => false,
+                }
+        });
+
+    // Also check whether imports were asked to be inlined, in case we're trying to re-export a
+    // crate in Rust 2018+
+    let path = clean_path(path, cx);
+    let inner = if kind == hir::UseKind::Glob {
+        if !denied {
+            let mut visited = FxHashSet::default();
+            if let Some(items) = inline::try_inline_glob(cx, path.res, &mut visited, inlined_names)
+            {
+                return items;
+            }
+        }
+        Import::new_glob(resolve_use_source(cx, path), true)
+    } else {
+        if inline_attr.is_none() {
+            if let Res::Def(DefKind::Mod, did) = path.res {
+                if !did.is_local() && did.is_crate_root() {
+                    // if we're `pub use`ing an extern crate root, don't inline it unless we
+                    // were specifically asked for it
+                    denied = true;
+                }
+            }
+        }
+        if !denied {
+            let mut visited = FxHashSet::default();
+            let import_def_id = import.def_id.to_def_id();
+
+            if let Some(mut items) = inline::try_inline(
+                cx,
+                cx.tcx.parent_module(import.hir_id()).to_def_id(),
+                Some(import_def_id),
+                path.res,
+                name,
+                Some(attrs),
+                &mut visited,
+            ) {
+                items.push(Item::from_def_id_and_parts(
+                    import_def_id,
+                    None,
+                    ImportItem(Import::new_simple(name, resolve_use_source(cx, path), false)),
+                    cx,
+                ));
+                return items;
+            }
+        }
+        Import::new_simple(name, resolve_use_source(cx, path), true)
+    };
+
+    vec![Item::from_def_id_and_parts(import.def_id.to_def_id(), None, ImportItem(inner), cx)]
+}
+
+fn clean_maybe_renamed_foreign_item<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    item: &hir::ForeignItem<'tcx>,
+    renamed: Option<Symbol>,
+) -> Item {
+    let def_id = item.def_id.to_def_id();
+    cx.with_param_env(def_id, |cx| {
+        let kind = match item.kind {
+            hir::ForeignItemKind::Fn(decl, names, generics) => {
+                let (generics, decl) = enter_impl_trait(cx, |cx| {
+                    // NOTE: generics must be cleaned before args
+                    let generics = generics.clean(cx);
+                    let args = clean_args_from_types_and_names(cx, decl.inputs, names);
+                    let decl = clean_fn_decl_with_args(cx, decl, args);
+                    (generics, decl)
+                });
+                ForeignFunctionItem(Box::new(Function { decl, generics }))
+            }
+            hir::ForeignItemKind::Static(ty, mutability) => {
+                ForeignStaticItem(Static { type_: clean_ty(ty, cx), mutability, expr: None })
+            }
+            hir::ForeignItemKind::Type => ForeignTypeItem,
+        };
+
+        Item::from_hir_id_and_parts(
+            item.hir_id(),
+            Some(renamed.unwrap_or(item.ident.name)),
+            kind,
+            cx,
+        )
+    })
+}
+
+fn clean_type_binding<'tcx>(
+    type_binding: &hir::TypeBinding<'tcx>,
+    cx: &mut DocContext<'tcx>,
+) -> TypeBinding {
+    TypeBinding {
+        assoc: PathSegment { name: type_binding.ident.name, args: type_binding.gen_args.clean(cx) },
+        kind: match type_binding.kind {
+            hir::TypeBindingKind::Equality { ref term } => {
+                TypeBindingKind::Equality { term: clean_hir_term(term, cx) }
+            }
+            hir::TypeBindingKind::Constraint { bounds } => TypeBindingKind::Constraint {
+                bounds: bounds.iter().filter_map(|b| b.clean(cx)).collect(),
+            },
+        },
+    }
+}
diff --git a/src/librustdoc/clean/render_macro_matchers.rs b/src/librustdoc/clean/render_macro_matchers.rs
new file mode 100644
index 000000000..ed7683e36
--- /dev/null
+++ b/src/librustdoc/clean/render_macro_matchers.rs
@@ -0,0 +1,238 @@
+use rustc_ast::token::{self, BinOpToken, Delimiter};
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast_pretty::pprust::state::State as Printer;
+use rustc_ast_pretty::pprust::PrintState;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::parse::ParseSess;
+use rustc_span::source_map::FilePathMapping;
+use rustc_span::symbol::{kw, Ident, Symbol};
+use rustc_span::Span;
+
+/// Render a macro matcher in a format suitable for displaying to the user
+/// as part of an item declaration.
+pub(super) fn render_macro_matcher(tcx: TyCtxt<'_>, matcher: &TokenTree) -> String {
+    if let Some(snippet) = snippet_equal_to_token(tcx, matcher) {
+        // If the original source code is known, we display the matcher exactly
+        // as present in the source code.
+        return snippet;
+    }
+
+    // If the matcher is macro-generated or some other reason the source code
+    // snippet is not available, we attempt to nicely render the token tree.
+    let mut printer = Printer::new();
+
+    // If the inner ibox fits on one line, we get:
+    //
+    //     macro_rules! macroname {
+    //         (the matcher) => {...};
+    //     }
+    //
+    // If the inner ibox gets wrapped, the cbox will break and get indented:
+    //
+    //     macro_rules! macroname {
+    //         (
+    //             the matcher ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    //             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!
+    //         ) => {...};
+    //     }
+    printer.cbox(8);
+    printer.word("(");
+    printer.zerobreak();
+    printer.ibox(0);
+    match matcher {
+        TokenTree::Delimited(_span, _delim, tts) => print_tts(&mut printer, tts),
+        // Matcher which is not a Delimited is unexpected and should've failed
+        // to compile, but we render whatever it is wrapped in parens.
+        TokenTree::Token(..) => print_tt(&mut printer, matcher),
+    }
+    printer.end();
+    printer.break_offset_if_not_bol(0, -4);
+    printer.word(")");
+    printer.end();
+    printer.s.eof()
+}
+
+/// Find the source snippet for this token's Span, reparse it, and return the
+/// snippet if the reparsed TokenTree matches the argument TokenTree.
+fn snippet_equal_to_token(tcx: TyCtxt<'_>, matcher: &TokenTree) -> Option<String> {
+    // Find what rustc thinks is the source snippet.
+    // This may not actually be anything meaningful if this matcher was itself
+    // generated by a macro.
+    let source_map = tcx.sess.source_map();
+    let span = matcher.span();
+    let snippet = source_map.span_to_snippet(span).ok()?;
+
+    // Create a Parser.
+    let sess = ParseSess::new(FilePathMapping::empty());
+    let file_name = source_map.span_to_filename(span);
+    let mut parser =
+        match rustc_parse::maybe_new_parser_from_source_str(&sess, file_name, snippet.clone()) {
+            Ok(parser) => parser,
+            Err(diagnostics) => {
+                drop(diagnostics);
+                return None;
+            }
+        };
+
+    // Reparse a single token tree.
+    let mut reparsed_trees = match parser.parse_all_token_trees() {
+        Ok(reparsed_trees) => reparsed_trees,
+        Err(diagnostic) => {
+            diagnostic.cancel();
+            return None;
+        }
+    };
+    if reparsed_trees.len() != 1 {
+        return None;
+    }
+    let reparsed_tree = reparsed_trees.pop().unwrap();
+
+    // Compare against the original tree.
+    if reparsed_tree.eq_unspanned(matcher) { Some(snippet) } else { None }
+}
+
+fn print_tt(printer: &mut Printer<'_>, tt: &TokenTree) {
+    match tt {
+        TokenTree::Token(token, _) => {
+            let token_str = printer.token_to_string(token);
+            printer.word(token_str);
+            if let token::DocComment(..) = token.kind {
+                printer.hardbreak()
+            }
+        }
+        TokenTree::Delimited(_span, delim, tts) => {
+            let open_delim = printer.token_kind_to_string(&token::OpenDelim(*delim));
+            printer.word(open_delim);
+            if !tts.is_empty() {
+                if *delim == Delimiter::Brace {
+                    printer.space();
+                }
+                print_tts(printer, tts);
+                if *delim == Delimiter::Brace {
+                    printer.space();
+                }
+            }
+            let close_delim = printer.token_kind_to_string(&token::CloseDelim(*delim));
+            printer.word(close_delim);
+        }
+    }
+}
+
+fn print_tts(printer: &mut Printer<'_>, tts: &TokenStream) {
+    #[derive(Copy, Clone, PartialEq)]
+    enum State {
+        Start,
+        Dollar,
+        DollarIdent,
+        DollarIdentColon,
+        DollarParen,
+        DollarParenSep,
+        Pound,
+        PoundBang,
+        Ident,
+        Other,
+    }
+
+    use State::*;
+
+    let mut state = Start;
+    for tt in tts.trees() {
+        let (needs_space, next_state) = match &tt {
+            TokenTree::Token(tt, _) => match (state, &tt.kind) {
+                (Dollar, token::Ident(..)) => (false, DollarIdent),
+                (DollarIdent, token::Colon) => (false, DollarIdentColon),
+                (DollarIdentColon, token::Ident(..)) => (false, Other),
+                (
+                    DollarParen,
+                    token::BinOp(BinOpToken::Plus | BinOpToken::Star) | token::Question,
+                ) => (false, Other),
+                (DollarParen, _) => (false, DollarParenSep),
+                (DollarParenSep, token::BinOp(BinOpToken::Plus | BinOpToken::Star)) => {
+                    (false, Other)
+                }
+                (Pound, token::Not) => (false, PoundBang),
+                (_, token::Ident(symbol, /* is_raw */ false))
+                    if !usually_needs_space_between_keyword_and_open_delim(*symbol, tt.span) =>
+                {
+                    (true, Ident)
+                }
+                (_, token::Comma | token::Semi) => (false, Other),
+                (_, token::Dollar) => (true, Dollar),
+                (_, token::Pound) => (true, Pound),
+                (_, _) => (true, Other),
+            },
+            TokenTree::Delimited(_, delim, _) => match (state, delim) {
+                (Dollar, Delimiter::Parenthesis) => (false, DollarParen),
+                (Pound | PoundBang, Delimiter::Bracket) => (false, Other),
+                (Ident, Delimiter::Parenthesis | Delimiter::Bracket) => (false, Other),
+                (_, _) => (true, Other),
+            },
+        };
+        if state != Start && needs_space {
+            printer.space();
+        }
+        print_tt(printer, tt);
+        state = next_state;
+    }
+}
+
+fn usually_needs_space_between_keyword_and_open_delim(symbol: Symbol, span: Span) -> bool {
+    let ident = Ident { name: symbol, span };
+    let is_keyword = ident.is_used_keyword() || ident.is_unused_keyword();
+    if !is_keyword {
+        // An identifier that is not a keyword usually does not need a space
+        // before an open delim. For example: `f(0)` or `f[0]`.
+        return false;
+    }
+
+    match symbol {
+        // No space after keywords that are syntactically an expression. For
+        // example: a tuple struct created with `let _ = Self(0, 0)`, or if
+        // someone has `impl Index<MyStruct> for bool` then `true[MyStruct]`.
+        kw::False | kw::SelfLower | kw::SelfUpper | kw::True => false,
+
+        // No space, as in `let _: fn();`
+        kw::Fn => false,
+
+        // No space, as in `pub(crate) type T;`
+        kw::Pub => false,
+
+        // No space for keywords that can end an expression, as in `fut.await()`
+        // where fut's Output type is `fn()`.
+        kw::Await => false,
+
+        // Otherwise space after keyword. Some examples:
+        //
+        // `expr as [T; 2]`
+        //         ^
+        // `box (tuple,)`
+        //     ^
+        // `break (tuple,)`
+        //       ^
+        // `type T = dyn (Fn() -> dyn Trait) + Send;`
+        //              ^
+        // `for (tuple,) in iter {}`
+        //     ^
+        // `if (tuple,) == v {}`
+        //    ^
+        // `impl [T] {}`
+        //      ^
+        // `for x in [..] {}`
+        //          ^
+        // `let () = unit;`
+        //     ^
+        // `match [x, y] {...}`
+        //       ^
+        // `&mut (x as T)`
+        //      ^
+        // `return [];`
+        //        ^
+        // `fn f<T>() where (): Into<T>`
+        //                 ^
+        // `while (a + b).what() {}`
+        //       ^
+        // `yield [];`
+        //       ^
+        _ => true,
+    }
+}
diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
new file mode 100644
index 000000000..af7813a77
--- /dev/null
+++ b/src/librustdoc/clean/simplify.rs
@@ -0,0 +1,139 @@
+//! Simplification of where-clauses and parameter bounds into a prettier and
+//! more canonical form.
+//!
+//! Currently all cross-crate-inlined function use `rustc_middle::ty` to reconstruct
+//! the AST (e.g., see all of `clean::inline`), but this is not always a
+//! non-lossy transformation. The current format of storage for where-clauses
+//! for functions and such is simply a list of predicates. One example of this
+//! is that the AST predicate of: `where T: Trait<Foo = Bar>` is encoded as:
+//! `where T: Trait, <T as Trait>::Foo = Bar`.
+//!
+//! This module attempts to reconstruct the original where and/or parameter
+//! bounds by special casing scenarios such as these. Fun!
+
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty;
+use rustc_span::Symbol;
+
+use crate::clean;
+use crate::clean::GenericArgs as PP;
+use crate::clean::WherePredicate as WP;
+use crate::core::DocContext;
+
+pub(crate) fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
+    // First, partition the where clause into its separate components.
+    //
+    // We use `FxIndexMap` so that the insertion order is preserved to prevent messing up to
+    // the order of the generated bounds.
+    let mut params: FxIndexMap<Symbol, (Vec<_>, Vec<_>)> = FxIndexMap::default();
+    let mut lifetimes = Vec::new();
+    let mut equalities = Vec::new();
+    let mut tybounds = Vec::new();
+
+    for clause in clauses {
+        match clause {
+            WP::BoundPredicate { ty, bounds, bound_params } => match ty {
+                clean::Generic(s) => {
+                    let (b, p) = params.entry(s).or_default();
+                    b.extend(bounds);
+                    p.extend(bound_params);
+                }
+                t => tybounds.push((t, (bounds, bound_params))),
+            },
+            WP::RegionPredicate { lifetime, bounds } => {
+                lifetimes.push((lifetime, bounds));
+            }
+            WP::EqPredicate { lhs, rhs } => equalities.push((lhs, rhs)),
+        }
+    }
+
+    // Look for equality predicates on associated types that can be merged into
+    // general bound predicates
+    equalities.retain(|&(ref lhs, ref rhs)| {
+        let Some((self_, trait_did, name)) = lhs.projection() else {
+            return true;
+        };
+        let clean::Generic(generic) = self_ else { return true };
+        let Some((bounds, _)) = params.get_mut(generic) else { return true };
+
+        merge_bounds(cx, bounds, trait_did, name, rhs)
+    });
+
+    // And finally, let's reassemble everything
+    let mut clauses = Vec::new();
+    clauses.extend(
+        lifetimes.into_iter().map(|(lt, bounds)| WP::RegionPredicate { lifetime: lt, bounds }),
+    );
+    clauses.extend(params.into_iter().map(|(k, (bounds, params))| WP::BoundPredicate {
+        ty: clean::Generic(k),
+        bounds,
+        bound_params: params,
+    }));
+    clauses.extend(tybounds.into_iter().map(|(ty, (bounds, bound_params))| WP::BoundPredicate {
+        ty,
+        bounds,
+        bound_params,
+    }));
+    clauses.extend(equalities.into_iter().map(|(lhs, rhs)| WP::EqPredicate { lhs, rhs }));
+    clauses
+}
+
+pub(crate) fn merge_bounds(
+    cx: &clean::DocContext<'_>,
+    bounds: &mut Vec<clean::GenericBound>,
+    trait_did: DefId,
+    assoc: clean::PathSegment,
+    rhs: &clean::Term,
+) -> bool {
+    !bounds.iter_mut().any(|b| {
+        let trait_ref = match *b {
+            clean::GenericBound::TraitBound(ref mut tr, _) => tr,
+            clean::GenericBound::Outlives(..) => return false,
+        };
+        // If this QPath's trait `trait_did` is the same as, or a supertrait
+        // of, the bound's trait `did` then we can keep going, otherwise
+        // this is just a plain old equality bound.
+        if !trait_is_same_or_supertrait(cx, trait_ref.trait_.def_id(), trait_did) {
+            return false;
+        }
+        let last = trait_ref.trait_.segments.last_mut().expect("segments were empty");
+        match last.args {
+            PP::AngleBracketed { ref mut bindings, .. } => {
+                bindings.push(clean::TypeBinding {
+                    assoc: assoc.clone(),
+                    kind: clean::TypeBindingKind::Equality { term: rhs.clone() },
+                });
+            }
+            PP::Parenthesized { ref mut output, .. } => match output {
+                Some(o) => assert_eq!(&clean::Term::Type(o.as_ref().clone()), rhs),
+                None => {
+                    if *rhs != clean::Term::Type(clean::Type::Tuple(Vec::new())) {
+                        *output = Some(Box::new(rhs.ty().unwrap().clone()));
+                    }
+                }
+            },
+        };
+        true
+    })
+}
+
+fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId, trait_: DefId) -> bool {
+    if child == trait_ {
+        return true;
+    }
+    let predicates = cx.tcx.super_predicates_of(child);
+    debug_assert!(cx.tcx.generics_of(child).has_self);
+    let self_ty = cx.tcx.types.self_param;
+    predicates
+        .predicates
+        .iter()
+        .filter_map(|(pred, _)| {
+            if let ty::PredicateKind::Trait(pred) = pred.kind().skip_binder() {
+                if pred.trait_ref.self_ty() == self_ty { Some(pred.def_id()) } else { None }
+            } else {
+                None
+            }
+        })
+        .any(|did| trait_is_same_or_supertrait(cx, did, trait_))
+}
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
new file mode 100644
index 000000000..0e6de842c
--- /dev/null
+++ b/src/librustdoc/clean/types.rs
@@ -0,0 +1,2508 @@
+use std::cell::RefCell;
+use std::default::Default;
+use std::hash::Hash;
+use std::path::PathBuf;
+use std::rc::Rc;
+use std::sync::Arc;
+use std::sync::OnceLock as OnceCell;
+use std::{cmp, fmt, iter};
+
+use arrayvec::ArrayVec;
+
+use rustc_ast::attr;
+use rustc_ast::util::comments::beautify_doc_string;
+use rustc_ast::{self as ast, AttrStyle};
+use rustc_attr::{ConstStability, Deprecation, Stability, StabilityLevel};
+use rustc_const_eval::const_eval::is_unstable_const_fn;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::thin_vec::ThinVec;
+use rustc_hir as hir;
+use rustc_hir::def::{CtorKind, DefKind, Res};
+use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
+use rustc_hir::lang_items::LangItem;
+use rustc_hir::{BodyId, Mutability};
+use rustc_index::vec::IndexVec;
+use rustc_middle::ty::fast_reject::SimplifiedType;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_session::Session;
+use rustc_span::hygiene::MacroKind;
+use rustc_span::source_map::DUMMY_SP;
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{self, FileName, Loc};
+use rustc_target::abi::VariantIdx;
+use rustc_target::spec::abi::Abi;
+use rustc_typeck::check::intrinsic::intrinsic_operation_unsafety;
+
+use crate::clean::cfg::Cfg;
+use crate::clean::clean_visibility;
+use crate::clean::external_path;
+use crate::clean::inline::{self, print_inlined_const};
+use crate::clean::utils::{is_literal_expr, print_const_expr, print_evaluated_const};
+use crate::core::DocContext;
+use crate::formats::cache::Cache;
+use crate::formats::item_type::ItemType;
+use crate::html::render::Context;
+use crate::passes::collect_intra_doc_links::UrlFragment;
+
+pub(crate) use self::FnRetTy::*;
+pub(crate) use self::ItemKind::*;
+pub(crate) use self::SelfTy::*;
+pub(crate) use self::Type::{
+    Array, BareFunction, BorrowedRef, DynTrait, Generic, ImplTrait, Infer, Primitive, QPath,
+    RawPointer, Slice, Tuple,
+};
+pub(crate) use self::Visibility::{Inherited, Public};
+
+#[cfg(test)]
+mod tests;
+
+pub(crate) type ItemIdSet = FxHashSet<ItemId>;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
+pub(crate) enum ItemId {
+    /// A "normal" item that uses a [`DefId`] for identification.
+    DefId(DefId),
+    /// Identifier that is used for auto traits.
+    Auto { trait_: DefId, for_: DefId },
+    /// Identifier that is used for blanket implementations.
+    Blanket { impl_id: DefId, for_: DefId },
+    /// Identifier for primitive types.
+    Primitive(PrimitiveType, CrateNum),
+}
+
+impl ItemId {
+    #[inline]
+    pub(crate) fn is_local(self) -> bool {
+        match self {
+            ItemId::Auto { for_: id, .. }
+            | ItemId::Blanket { for_: id, .. }
+            | ItemId::DefId(id) => id.is_local(),
+            ItemId::Primitive(_, krate) => krate == LOCAL_CRATE,
+        }
+    }
+
+    #[inline]
+    #[track_caller]
+    pub(crate) fn expect_def_id(self) -> DefId {
+        self.as_def_id()
+            .unwrap_or_else(|| panic!("ItemId::expect_def_id: `{:?}` isn't a DefId", self))
+    }
+
+    #[inline]
+    pub(crate) fn as_def_id(self) -> Option<DefId> {
+        match self {
+            ItemId::DefId(id) => Some(id),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn krate(self) -> CrateNum {
+        match self {
+            ItemId::Auto { for_: id, .. }
+            | ItemId::Blanket { for_: id, .. }
+            | ItemId::DefId(id) => id.krate,
+            ItemId::Primitive(_, krate) => krate,
+        }
+    }
+}
+
+impl From<DefId> for ItemId {
+    fn from(id: DefId) -> Self {
+        Self::DefId(id)
+    }
+}
+
+/// The crate currently being documented.
+#[derive(Clone, Debug)]
+pub(crate) struct Crate {
+    pub(crate) module: Item,
+    pub(crate) primitives: ThinVec<(DefId, PrimitiveType)>,
+    /// Only here so that they can be filtered through the rustdoc passes.
+    pub(crate) external_traits: Rc<RefCell<FxHashMap<DefId, TraitWithExtraInfo>>>,
+}
+
+impl Crate {
+    pub(crate) fn name(&self, tcx: TyCtxt<'_>) -> Symbol {
+        ExternalCrate::LOCAL.name(tcx)
+    }
+
+    pub(crate) fn src(&self, tcx: TyCtxt<'_>) -> FileName {
+        ExternalCrate::LOCAL.src(tcx)
+    }
+}
+
+/// This struct is used to wrap additional information added by rustdoc on a `trait` item.
+#[derive(Clone, Debug)]
+pub(crate) struct TraitWithExtraInfo {
+    pub(crate) trait_: Trait,
+    pub(crate) is_notable: bool,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct ExternalCrate {
+    pub(crate) crate_num: CrateNum,
+}
+
+impl ExternalCrate {
+    const LOCAL: Self = Self { crate_num: LOCAL_CRATE };
+
+    #[inline]
+    pub(crate) fn def_id(&self) -> DefId {
+        self.crate_num.as_def_id()
+    }
+
+    pub(crate) fn src(&self, tcx: TyCtxt<'_>) -> FileName {
+        let krate_span = tcx.def_span(self.def_id());
+        tcx.sess.source_map().span_to_filename(krate_span)
+    }
+
+    pub(crate) fn name(&self, tcx: TyCtxt<'_>) -> Symbol {
+        tcx.crate_name(self.crate_num)
+    }
+
+    pub(crate) fn src_root(&self, tcx: TyCtxt<'_>) -> PathBuf {
+        match self.src(tcx) {
+            FileName::Real(ref p) => match p.local_path_if_available().parent() {
+                Some(p) => p.to_path_buf(),
+                None => PathBuf::new(),
+            },
+            _ => PathBuf::new(),
+        }
+    }
+
+    /// Attempts to find where an external crate is located, given that we're
+    /// rendering in to the specified source destination.
+    pub(crate) fn location(
+        &self,
+        extern_url: Option<&str>,
+        extern_url_takes_precedence: bool,
+        dst: &std::path::Path,
+        tcx: TyCtxt<'_>,
+    ) -> ExternalLocation {
+        use ExternalLocation::*;
+
+        fn to_remote(url: impl ToString) -> ExternalLocation {
+            let mut url = url.to_string();
+            if !url.ends_with('/') {
+                url.push('/');
+            }
+            Remote(url)
+        }
+
+        // See if there's documentation generated into the local directory
+        // WARNING: since rustdoc creates these directories as it generates documentation, this check is only accurate before rendering starts.
+        // Make sure to call `location()` by that time.
+        let local_location = dst.join(self.name(tcx).as_str());
+        if local_location.is_dir() {
+            return Local;
+        }
+
+        if extern_url_takes_precedence {
+            if let Some(url) = extern_url {
+                return to_remote(url);
+            }
+        }
+
+        // Failing that, see if there's an attribute specifying where to find this
+        // external crate
+        let did = self.crate_num.as_def_id();
+        tcx.get_attrs(did, sym::doc)
+            .flat_map(|attr| attr.meta_item_list().unwrap_or_default())
+            .filter(|a| a.has_name(sym::html_root_url))
+            .filter_map(|a| a.value_str())
+            .map(to_remote)
+            .next()
+            .or_else(|| extern_url.map(to_remote)) // NOTE: only matters if `extern_url_takes_precedence` is false
+            .unwrap_or(Unknown) // Well, at least we tried.
+    }
+
+    pub(crate) fn keywords(&self, tcx: TyCtxt<'_>) -> ThinVec<(DefId, Symbol)> {
+        let root = self.def_id();
+
+        let as_keyword = |res: Res<!>| {
+            if let Res::Def(DefKind::Mod, def_id) = res {
+                let mut keyword = None;
+                let meta_items = tcx
+                    .get_attrs(def_id, sym::doc)
+                    .flat_map(|attr| attr.meta_item_list().unwrap_or_default());
+                for meta in meta_items {
+                    if meta.has_name(sym::keyword) {
+                        if let Some(v) = meta.value_str() {
+                            keyword = Some(v);
+                            break;
+                        }
+                    }
+                }
+                return keyword.map(|p| (def_id, p));
+            }
+            None
+        };
+        if root.is_local() {
+            tcx.hir()
+                .root_module()
+                .item_ids
+                .iter()
+                .filter_map(|&id| {
+                    let item = tcx.hir().item(id);
+                    match item.kind {
+                        hir::ItemKind::Mod(_) => {
+                            as_keyword(Res::Def(DefKind::Mod, id.def_id.to_def_id()))
+                        }
+                        hir::ItemKind::Use(path, hir::UseKind::Single)
+                            if tcx.visibility(id.def_id).is_public() =>
+                        {
+                            as_keyword(path.res.expect_non_local())
+                                .map(|(_, prim)| (id.def_id.to_def_id(), prim))
+                        }
+                        _ => None,
+                    }
+                })
+                .collect()
+        } else {
+            tcx.module_children(root).iter().map(|item| item.res).filter_map(as_keyword).collect()
+        }
+    }
+
+    pub(crate) fn primitives(&self, tcx: TyCtxt<'_>) -> ThinVec<(DefId, PrimitiveType)> {
+        let root = self.def_id();
+
+        // Collect all inner modules which are tagged as implementations of
+        // primitives.
+        //
+        // Note that this loop only searches the top-level items of the crate,
+        // and this is intentional. If we were to search the entire crate for an
+        // item tagged with `#[doc(primitive)]` then we would also have to
+        // search the entirety of external modules for items tagged
+        // `#[doc(primitive)]`, which is a pretty inefficient process (decoding
+        // all that metadata unconditionally).
+        //
+        // In order to keep the metadata load under control, the
+        // `#[doc(primitive)]` feature is explicitly designed to only allow the
+        // primitive tags to show up as the top level items in a crate.
+        //
+        // Also note that this does not attempt to deal with modules tagged
+        // duplicately for the same primitive. This is handled later on when
+        // rendering by delegating everything to a hash map.
+        let as_primitive = |res: Res<!>| {
+            if let Res::Def(DefKind::Mod, def_id) = res {
+                let mut prim = None;
+                let meta_items = tcx
+                    .get_attrs(def_id, sym::doc)
+                    .flat_map(|attr| attr.meta_item_list().unwrap_or_default());
+                for meta in meta_items {
+                    if let Some(v) = meta.value_str() {
+                        if meta.has_name(sym::primitive) {
+                            prim = PrimitiveType::from_symbol(v);
+                            if prim.is_some() {
+                                break;
+                            }
+                            // FIXME: should warn on unknown primitives?
+                        }
+                    }
+                }
+                return prim.map(|p| (def_id, p));
+            }
+            None
+        };
+
+        if root.is_local() {
+            tcx.hir()
+                .root_module()
+                .item_ids
+                .iter()
+                .filter_map(|&id| {
+                    let item = tcx.hir().item(id);
+                    match item.kind {
+                        hir::ItemKind::Mod(_) => {
+                            as_primitive(Res::Def(DefKind::Mod, id.def_id.to_def_id()))
+                        }
+                        hir::ItemKind::Use(path, hir::UseKind::Single)
+                            if tcx.visibility(id.def_id).is_public() =>
+                        {
+                            as_primitive(path.res.expect_non_local()).map(|(_, prim)| {
+                                // Pretend the primitive is local.
+                                (id.def_id.to_def_id(), prim)
+                            })
+                        }
+                        _ => None,
+                    }
+                })
+                .collect()
+        } else {
+            tcx.module_children(root).iter().map(|item| item.res).filter_map(as_primitive).collect()
+        }
+    }
+}
+
+/// Indicates where an external crate can be found.
+#[derive(Debug)]
+pub(crate) enum ExternalLocation {
+    /// Remote URL root of the external crate
+    Remote(String),
+    /// This external crate can be found in the local doc/ folder
+    Local,
+    /// The external crate could not be found.
+    Unknown,
+}
+
+/// Anything with a source location and set of attributes and, optionally, a
+/// name. That is, anything that can be documented. This doesn't correspond
+/// directly to the AST's concept of an item; it's a strict superset.
+#[derive(Clone)]
+pub(crate) struct Item {
+    /// The name of this item.
+    /// Optional because not every item has a name, e.g. impls.
+    pub(crate) name: Option<Symbol>,
+    pub(crate) attrs: Box<Attributes>,
+    pub(crate) visibility: Visibility,
+    /// Information about this item that is specific to what kind of item it is.
+    /// E.g., struct vs enum vs function.
+    pub(crate) kind: Box<ItemKind>,
+    pub(crate) item_id: ItemId,
+
+    pub(crate) cfg: Option<Arc<Cfg>>,
+}
+
+/// NOTE: this does NOT unconditionally print every item, to avoid thousands of lines of logs.
+/// If you want to see the debug output for attributes and the `kind` as well, use `{:#?}` instead of `{:?}`.
+impl fmt::Debug for Item {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let alternate = f.alternate();
+        // hand-picked fields that don't bloat the logs too much
+        let mut fmt = f.debug_struct("Item");
+        fmt.field("name", &self.name)
+            .field("visibility", &self.visibility)
+            .field("item_id", &self.item_id);
+        // allow printing the full item if someone really wants to
+        if alternate {
+            fmt.field("attrs", &self.attrs).field("kind", &self.kind).field("cfg", &self.cfg);
+        } else {
+            fmt.field("kind", &self.type_());
+            fmt.field("docs", &self.doc_value());
+        }
+        fmt.finish()
+    }
+}
+
+pub(crate) fn rustc_span(def_id: DefId, tcx: TyCtxt<'_>) -> Span {
+    Span::new(def_id.as_local().map_or_else(
+        || tcx.def_span(def_id),
+        |local| {
+            let hir = tcx.hir();
+            hir.span_with_body(hir.local_def_id_to_hir_id(local))
+        },
+    ))
+}
+
+impl Item {
+    pub(crate) fn stability<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<Stability> {
+        self.item_id.as_def_id().and_then(|did| tcx.lookup_stability(did))
+    }
+
+    pub(crate) fn const_stability<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<ConstStability> {
+        self.item_id.as_def_id().and_then(|did| tcx.lookup_const_stability(did))
+    }
+
+    pub(crate) fn deprecation(&self, tcx: TyCtxt<'_>) -> Option<Deprecation> {
+        self.item_id.as_def_id().and_then(|did| tcx.lookup_deprecation(did))
+    }
+
+    pub(crate) fn inner_docs(&self, tcx: TyCtxt<'_>) -> bool {
+        self.item_id
+            .as_def_id()
+            .map(|did| tcx.get_attrs_unchecked(did).inner_docs())
+            .unwrap_or(false)
+    }
+
+    pub(crate) fn span(&self, tcx: TyCtxt<'_>) -> Span {
+        let kind = match &*self.kind {
+            ItemKind::StrippedItem(k) => k,
+            _ => &*self.kind,
+        };
+        match kind {
+            ItemKind::ModuleItem(Module { span, .. }) => *span,
+            ItemKind::ImplItem(box Impl { kind: ImplKind::Auto, .. }) => Span::dummy(),
+            ItemKind::ImplItem(box Impl { kind: ImplKind::Blanket(_), .. }) => {
+                if let ItemId::Blanket { impl_id, .. } = self.item_id {
+                    rustc_span(impl_id, tcx)
+                } else {
+                    panic!("blanket impl item has non-blanket ID")
+                }
+            }
+            _ => {
+                self.item_id.as_def_id().map(|did| rustc_span(did, tcx)).unwrap_or_else(Span::dummy)
+            }
+        }
+    }
+
+    pub(crate) fn attr_span(&self, tcx: TyCtxt<'_>) -> rustc_span::Span {
+        crate::passes::span_of_attrs(&self.attrs).unwrap_or_else(|| self.span(tcx).inner())
+    }
+
+    /// Finds the `doc` attribute as a NameValue and returns the corresponding
+    /// value found.
+    pub(crate) fn doc_value(&self) -> Option<String> {
+        self.attrs.doc_value()
+    }
+
+    /// Convenience wrapper around [`Self::from_def_id_and_parts`] which converts
+    /// `hir_id` to a [`DefId`]
+    pub(crate) fn from_hir_id_and_parts(
+        hir_id: hir::HirId,
+        name: Option<Symbol>,
+        kind: ItemKind,
+        cx: &mut DocContext<'_>,
+    ) -> Item {
+        Item::from_def_id_and_parts(cx.tcx.hir().local_def_id(hir_id).to_def_id(), name, kind, cx)
+    }
+
+    pub(crate) fn from_def_id_and_parts(
+        def_id: DefId,
+        name: Option<Symbol>,
+        kind: ItemKind,
+        cx: &mut DocContext<'_>,
+    ) -> Item {
+        let ast_attrs = cx.tcx.get_attrs_unchecked(def_id);
+
+        Self::from_def_id_and_attrs_and_parts(
+            def_id,
+            name,
+            kind,
+            Box::new(Attributes::from_ast(ast_attrs)),
+            cx,
+            ast_attrs.cfg(cx.tcx, &cx.cache.hidden_cfg),
+        )
+    }
+
+    pub(crate) fn from_def_id_and_attrs_and_parts(
+        def_id: DefId,
+        name: Option<Symbol>,
+        kind: ItemKind,
+        attrs: Box<Attributes>,
+        cx: &mut DocContext<'_>,
+        cfg: Option<Arc<Cfg>>,
+    ) -> Item {
+        trace!("name={:?}, def_id={:?}", name, def_id);
+
+        // Primitives and Keywords are written in the source code as private modules.
+        // The modules need to be private so that nobody actually uses them, but the
+        // keywords and primitives that they are documenting are public.
+        let visibility = if matches!(&kind, ItemKind::KeywordItem | ItemKind::PrimitiveItem(..)) {
+            Visibility::Public
+        } else {
+            clean_visibility(cx.tcx.visibility(def_id))
+        };
+
+        Item { item_id: def_id.into(), kind: Box::new(kind), name, attrs, visibility, cfg }
+    }
+
+    /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
+    /// with newlines.
+    pub(crate) fn collapsed_doc_value(&self) -> Option<String> {
+        self.attrs.collapsed_doc_value()
+    }
+
+    pub(crate) fn links(&self, cx: &Context<'_>) -> Vec<RenderedLink> {
+        use crate::html::format::href;
+
+        cx.cache()
+            .intra_doc_links
+            .get(&self.item_id)
+            .map_or(&[][..], |v| v.as_slice())
+            .iter()
+            .filter_map(|ItemLink { link: s, link_text, did, ref fragment }| {
+                debug!(?did);
+                if let Ok((mut href, ..)) = href(*did, cx) {
+                    debug!(?href);
+                    if let Some(ref fragment) = *fragment {
+                        fragment.render(&mut href, cx.tcx())
+                    }
+                    Some(RenderedLink {
+                        original_text: s.clone(),
+                        new_text: link_text.clone(),
+                        href,
+                    })
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+
+    /// Find a list of all link names, without finding their href.
+    ///
+    /// This is used for generating summary text, which does not include
+    /// the link text, but does need to know which `[]`-bracketed names
+    /// are actually links.
+    pub(crate) fn link_names(&self, cache: &Cache) -> Vec<RenderedLink> {
+        cache
+            .intra_doc_links
+            .get(&self.item_id)
+            .map_or(&[][..], |v| v.as_slice())
+            .iter()
+            .map(|ItemLink { link: s, link_text, .. }| RenderedLink {
+                original_text: s.clone(),
+                new_text: link_text.clone(),
+                href: String::new(),
+            })
+            .collect()
+    }
+
+    pub(crate) fn is_crate(&self) -> bool {
+        self.is_mod() && self.item_id.as_def_id().map_or(false, |did| did.is_crate_root())
+    }
+    pub(crate) fn is_mod(&self) -> bool {
+        self.type_() == ItemType::Module
+    }
+    pub(crate) fn is_trait(&self) -> bool {
+        self.type_() == ItemType::Trait
+    }
+    pub(crate) fn is_struct(&self) -> bool {
+        self.type_() == ItemType::Struct
+    }
+    pub(crate) fn is_enum(&self) -> bool {
+        self.type_() == ItemType::Enum
+    }
+    pub(crate) fn is_variant(&self) -> bool {
+        self.type_() == ItemType::Variant
+    }
+    pub(crate) fn is_associated_type(&self) -> bool {
+        matches!(&*self.kind, AssocTypeItem(..) | StrippedItem(box AssocTypeItem(..)))
+    }
+    pub(crate) fn is_ty_associated_type(&self) -> bool {
+        matches!(&*self.kind, TyAssocTypeItem(..) | StrippedItem(box TyAssocTypeItem(..)))
+    }
+    pub(crate) fn is_associated_const(&self) -> bool {
+        matches!(&*self.kind, AssocConstItem(..) | StrippedItem(box AssocConstItem(..)))
+    }
+    pub(crate) fn is_ty_associated_const(&self) -> bool {
+        matches!(&*self.kind, TyAssocConstItem(..) | StrippedItem(box TyAssocConstItem(..)))
+    }
+    pub(crate) fn is_method(&self) -> bool {
+        self.type_() == ItemType::Method
+    }
+    pub(crate) fn is_ty_method(&self) -> bool {
+        self.type_() == ItemType::TyMethod
+    }
+    pub(crate) fn is_typedef(&self) -> bool {
+        self.type_() == ItemType::Typedef
+    }
+    pub(crate) fn is_primitive(&self) -> bool {
+        self.type_() == ItemType::Primitive
+    }
+    pub(crate) fn is_union(&self) -> bool {
+        self.type_() == ItemType::Union
+    }
+    pub(crate) fn is_import(&self) -> bool {
+        self.type_() == ItemType::Import
+    }
+    pub(crate) fn is_extern_crate(&self) -> bool {
+        self.type_() == ItemType::ExternCrate
+    }
+    pub(crate) fn is_keyword(&self) -> bool {
+        self.type_() == ItemType::Keyword
+    }
+    pub(crate) fn is_stripped(&self) -> bool {
+        match *self.kind {
+            StrippedItem(..) => true,
+            ImportItem(ref i) => !i.should_be_displayed,
+            _ => false,
+        }
+    }
+    pub(crate) fn has_stripped_entries(&self) -> Option<bool> {
+        match *self.kind {
+            StructItem(ref struct_) => Some(struct_.has_stripped_entries()),
+            UnionItem(ref union_) => Some(union_.has_stripped_entries()),
+            EnumItem(ref enum_) => Some(enum_.has_stripped_entries()),
+            VariantItem(ref v) => v.has_stripped_entries(),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn stability_class(&self, tcx: TyCtxt<'_>) -> Option<String> {
+        self.stability(tcx).as_ref().and_then(|s| {
+            let mut classes = Vec::with_capacity(2);
+
+            if s.is_unstable() {
+                classes.push("unstable");
+            }
+
+            // FIXME: what about non-staged API items that are deprecated?
+            if self.deprecation(tcx).is_some() {
+                classes.push("deprecated");
+            }
+
+            if !classes.is_empty() { Some(classes.join(" ")) } else { None }
+        })
+    }
+
+    pub(crate) fn stable_since(&self, tcx: TyCtxt<'_>) -> Option<Symbol> {
+        match self.stability(tcx)?.level {
+            StabilityLevel::Stable { since, .. } => Some(since),
+            StabilityLevel::Unstable { .. } => None,
+        }
+    }
+
+    pub(crate) fn const_stable_since(&self, tcx: TyCtxt<'_>) -> Option<Symbol> {
+        match self.const_stability(tcx)?.level {
+            StabilityLevel::Stable { since, .. } => Some(since),
+            StabilityLevel::Unstable { .. } => None,
+        }
+    }
+
+    pub(crate) fn is_non_exhaustive(&self) -> bool {
+        self.attrs.other_attrs.iter().any(|a| a.has_name(sym::non_exhaustive))
+    }
+
+    /// Returns a documentation-level item type from the item.
+    pub(crate) fn type_(&self) -> ItemType {
+        ItemType::from(self)
+    }
+
+    pub(crate) fn is_default(&self) -> bool {
+        match *self.kind {
+            ItemKind::MethodItem(_, Some(defaultness)) => {
+                defaultness.has_value() && !defaultness.is_final()
+            }
+            _ => false,
+        }
+    }
+
+    /// Returns a `FnHeader` if `self` is a function item, otherwise returns `None`.
+    pub(crate) fn fn_header(&self, tcx: TyCtxt<'_>) -> Option<hir::FnHeader> {
+        fn build_fn_header(
+            def_id: DefId,
+            tcx: TyCtxt<'_>,
+            asyncness: hir::IsAsync,
+        ) -> hir::FnHeader {
+            let sig = tcx.fn_sig(def_id);
+            let constness =
+                if tcx.is_const_fn(def_id) && is_unstable_const_fn(tcx, def_id).is_none() {
+                    hir::Constness::Const
+                } else {
+                    hir::Constness::NotConst
+                };
+            hir::FnHeader { unsafety: sig.unsafety(), abi: sig.abi(), constness, asyncness }
+        }
+        let header = match *self.kind {
+            ItemKind::ForeignFunctionItem(_) => {
+                let abi = tcx.fn_sig(self.item_id.as_def_id().unwrap()).abi();
+                hir::FnHeader {
+                    unsafety: if abi == Abi::RustIntrinsic {
+                        intrinsic_operation_unsafety(self.name.unwrap())
+                    } else {
+                        hir::Unsafety::Unsafe
+                    },
+                    abi,
+                    constness: hir::Constness::NotConst,
+                    asyncness: hir::IsAsync::NotAsync,
+                }
+            }
+            ItemKind::FunctionItem(_) | ItemKind::MethodItem(_, _) => {
+                let def_id = self.item_id.as_def_id().unwrap();
+                build_fn_header(def_id, tcx, tcx.asyncness(def_id))
+            }
+            ItemKind::TyMethodItem(_) => {
+                build_fn_header(self.item_id.as_def_id().unwrap(), tcx, hir::IsAsync::NotAsync)
+            }
+            _ => return None,
+        };
+        Some(header)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum ItemKind {
+    ExternCrateItem {
+        /// The crate's name, *not* the name it's imported as.
+        src: Option<Symbol>,
+    },
+    ImportItem(Import),
+    StructItem(Struct),
+    UnionItem(Union),
+    EnumItem(Enum),
+    FunctionItem(Box<Function>),
+    ModuleItem(Module),
+    TypedefItem(Box<Typedef>),
+    OpaqueTyItem(OpaqueTy),
+    StaticItem(Static),
+    ConstantItem(Constant),
+    TraitItem(Trait),
+    TraitAliasItem(TraitAlias),
+    ImplItem(Box<Impl>),
+    /// A required method in a trait declaration meaning it's only a function signature.
+    TyMethodItem(Box<Function>),
+    /// A method in a trait impl or a provided method in a trait declaration.
+    ///
+    /// Compared to [TyMethodItem], it also contains a method body.
+    MethodItem(Box<Function>, Option<hir::Defaultness>),
+    StructFieldItem(Type),
+    VariantItem(Variant),
+    /// `fn`s from an extern block
+    ForeignFunctionItem(Box<Function>),
+    /// `static`s from an extern block
+    ForeignStaticItem(Static),
+    /// `type`s from an extern block
+    ForeignTypeItem,
+    MacroItem(Macro),
+    ProcMacroItem(ProcMacro),
+    PrimitiveItem(PrimitiveType),
+    /// A required associated constant in a trait declaration.
+    TyAssocConstItem(Type),
+    /// An associated associated constant in a trait impl or a provided one in a trait declaration.
+    AssocConstItem(Type, ConstantKind),
+    /// A required associated type in a trait declaration.
+    ///
+    /// The bounds may be non-empty if there is a `where` clause.
+    TyAssocTypeItem(Box<Generics>, Vec<GenericBound>),
+    /// An associated type in a trait impl or a provided one in a trait declaration.
+    AssocTypeItem(Box<Typedef>, Vec<GenericBound>),
+    /// An item that has been stripped by a rustdoc pass
+    StrippedItem(Box<ItemKind>),
+    KeywordItem,
+}
+
+impl ItemKind {
+    /// Some items contain others such as structs (for their fields) and Enums
+    /// (for their variants). This method returns those contained items.
+    pub(crate) fn inner_items(&self) -> impl Iterator<Item = &Item> {
+        match self {
+            StructItem(s) => s.fields.iter(),
+            UnionItem(u) => u.fields.iter(),
+            VariantItem(Variant::Struct(v)) => v.fields.iter(),
+            VariantItem(Variant::Tuple(v)) => v.iter(),
+            EnumItem(e) => e.variants.iter(),
+            TraitItem(t) => t.items.iter(),
+            ImplItem(i) => i.items.iter(),
+            ModuleItem(m) => m.items.iter(),
+            ExternCrateItem { .. }
+            | ImportItem(_)
+            | FunctionItem(_)
+            | TypedefItem(_)
+            | OpaqueTyItem(_)
+            | StaticItem(_)
+            | ConstantItem(_)
+            | TraitAliasItem(_)
+            | TyMethodItem(_)
+            | MethodItem(_, _)
+            | StructFieldItem(_)
+            | VariantItem(_)
+            | ForeignFunctionItem(_)
+            | ForeignStaticItem(_)
+            | ForeignTypeItem
+            | MacroItem(_)
+            | ProcMacroItem(_)
+            | PrimitiveItem(_)
+            | TyAssocConstItem(_)
+            | AssocConstItem(_, _)
+            | TyAssocTypeItem(..)
+            | AssocTypeItem(..)
+            | StrippedItem(_)
+            | KeywordItem => [].iter(),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Module {
+    pub(crate) items: Vec<Item>,
+    pub(crate) span: Span,
+}
+
+pub(crate) trait AttributesExt {
+    type AttributeIterator<'a>: Iterator<Item = ast::NestedMetaItem>
+    where
+        Self: 'a;
+
+    fn lists<'a>(&'a self, name: Symbol) -> Self::AttributeIterator<'a>;
+
+    fn span(&self) -> Option<rustc_span::Span>;
+
+    fn inner_docs(&self) -> bool;
+
+    fn other_attrs(&self) -> Vec<ast::Attribute>;
+
+    fn cfg(&self, tcx: TyCtxt<'_>, hidden_cfg: &FxHashSet<Cfg>) -> Option<Arc<Cfg>>;
+}
+
+impl AttributesExt for [ast::Attribute] {
+    type AttributeIterator<'a> = impl Iterator<Item = ast::NestedMetaItem> + 'a;
+
+    fn lists<'a>(&'a self, name: Symbol) -> Self::AttributeIterator<'a> {
+        self.iter()
+            .filter(move |attr| attr.has_name(name))
+            .filter_map(ast::Attribute::meta_item_list)
+            .flatten()
+    }
+
+    /// Return the span of the first doc-comment, if it exists.
+    fn span(&self) -> Option<rustc_span::Span> {
+        self.iter().find(|attr| attr.doc_str().is_some()).map(|attr| attr.span)
+    }
+
+    /// Returns whether the first doc-comment is an inner attribute.
+    ///
+    //// If there are no doc-comments, return true.
+    /// FIXME(#78591): Support both inner and outer attributes on the same item.
+    fn inner_docs(&self) -> bool {
+        self.iter().find(|a| a.doc_str().is_some()).map_or(true, |a| a.style == AttrStyle::Inner)
+    }
+
+    fn other_attrs(&self) -> Vec<ast::Attribute> {
+        self.iter().filter(|attr| attr.doc_str().is_none()).cloned().collect()
+    }
+
+    fn cfg(&self, tcx: TyCtxt<'_>, hidden_cfg: &FxHashSet<Cfg>) -> Option<Arc<Cfg>> {
+        let sess = tcx.sess;
+        let doc_cfg_active = tcx.features().doc_cfg;
+        let doc_auto_cfg_active = tcx.features().doc_auto_cfg;
+
+        fn single<T: IntoIterator>(it: T) -> Option<T::Item> {
+            let mut iter = it.into_iter();
+            let item = iter.next()?;
+            if iter.next().is_some() {
+                return None;
+            }
+            Some(item)
+        }
+
+        let mut cfg = if doc_cfg_active || doc_auto_cfg_active {
+            let mut doc_cfg = self
+                .iter()
+                .filter(|attr| attr.has_name(sym::doc))
+                .flat_map(|attr| attr.meta_item_list().unwrap_or_default())
+                .filter(|attr| attr.has_name(sym::cfg))
+                .peekable();
+            if doc_cfg.peek().is_some() && doc_cfg_active {
+                doc_cfg
+                    .filter_map(|attr| Cfg::parse(attr.meta_item()?).ok())
+                    .fold(Cfg::True, |cfg, new_cfg| cfg & new_cfg)
+            } else if doc_auto_cfg_active {
+                self.iter()
+                    .filter(|attr| attr.has_name(sym::cfg))
+                    .filter_map(|attr| single(attr.meta_item_list()?))
+                    .filter_map(|attr| {
+                        Cfg::parse_without(attr.meta_item()?, hidden_cfg).ok().flatten()
+                    })
+                    .fold(Cfg::True, |cfg, new_cfg| cfg & new_cfg)
+            } else {
+                Cfg::True
+            }
+        } else {
+            Cfg::True
+        };
+
+        for attr in self.iter() {
+            // #[doc]
+            if attr.doc_str().is_none() && attr.has_name(sym::doc) {
+                // #[doc(...)]
+                if let Some(list) = attr.meta().as_ref().and_then(|mi| mi.meta_item_list()) {
+                    for item in list {
+                        // #[doc(hidden)]
+                        if !item.has_name(sym::cfg) {
+                            continue;
+                        }
+                        // #[doc(cfg(...))]
+                        if let Some(cfg_mi) = item
+                            .meta_item()
+                            .and_then(|item| rustc_expand::config::parse_cfg(item, sess))
+                        {
+                            match Cfg::parse(cfg_mi) {
+                                Ok(new_cfg) => cfg &= new_cfg,
+                                Err(e) => {
+                                    sess.span_err(e.span, e.msg);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        // treat #[target_feature(enable = "feat")] attributes as if they were
+        // #[doc(cfg(target_feature = "feat"))] attributes as well
+        for attr in self.lists(sym::target_feature) {
+            if attr.has_name(sym::enable) {
+                if let Some(feat) = attr.value_str() {
+                    let meta = attr::mk_name_value_item_str(
+                        Ident::with_dummy_span(sym::target_feature),
+                        feat,
+                        DUMMY_SP,
+                    );
+                    if let Ok(feat_cfg) = Cfg::parse(&meta) {
+                        cfg &= feat_cfg;
+                    }
+                }
+            }
+        }
+
+        if cfg == Cfg::True { None } else { Some(Arc::new(cfg)) }
+    }
+}
+
+pub(crate) trait NestedAttributesExt {
+    /// Returns `true` if the attribute list contains a specific `word`
+    fn has_word(self, word: Symbol) -> bool
+    where
+        Self: std::marker::Sized,
+    {
+        <Self as NestedAttributesExt>::get_word_attr(self, word).is_some()
+    }
+
+    /// Returns `Some(attr)` if the attribute list contains 'attr'
+    /// corresponding to a specific `word`
+    fn get_word_attr(self, word: Symbol) -> Option<ast::NestedMetaItem>;
+}
+
+impl<I: Iterator<Item = ast::NestedMetaItem>> NestedAttributesExt for I {
+    fn get_word_attr(mut self, word: Symbol) -> Option<ast::NestedMetaItem> {
+        self.find(|attr| attr.is_word() && attr.has_name(word))
+    }
+}
+
+/// A portion of documentation, extracted from a `#[doc]` attribute.
+///
+/// Each variant contains the line number within the complete doc-comment where the fragment
+/// starts, as well as the Span where the corresponding doc comment or attribute is located.
+///
+/// Included files are kept separate from inline doc comments so that proper line-number
+/// information can be given when a doctest fails. Sugared doc comments and "raw" doc comments are
+/// kept separate because of issue #42760.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub(crate) struct DocFragment {
+    pub(crate) span: rustc_span::Span,
+    /// The module this doc-comment came from.
+    ///
+    /// This allows distinguishing between the original documentation and a pub re-export.
+    /// If it is `None`, the item was not re-exported.
+    pub(crate) parent_module: Option<DefId>,
+    pub(crate) doc: Symbol,
+    pub(crate) kind: DocFragmentKind,
+    pub(crate) indent: usize,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub(crate) enum DocFragmentKind {
+    /// A doc fragment created from a `///` or `//!` doc comment.
+    SugaredDoc,
+    /// A doc fragment created from a "raw" `#[doc=""]` attribute.
+    RawDoc,
+}
+
+/// The goal of this function is to apply the `DocFragment` transformation that is required when
+/// transforming into the final Markdown, which is applying the computed indent to each line in
+/// each doc fragment (a `DocFragment` can contain multiple lines in case of `#[doc = ""]`).
+///
+/// Note: remove the trailing newline where appropriate
+fn add_doc_fragment(out: &mut String, frag: &DocFragment) {
+    let s = frag.doc.as_str();
+    let mut iter = s.lines();
+    if s.is_empty() {
+        out.push('\n');
+        return;
+    }
+    while let Some(line) = iter.next() {
+        if line.chars().any(|c| !c.is_whitespace()) {
+            assert!(line.len() >= frag.indent);
+            out.push_str(&line[frag.indent..]);
+        } else {
+            out.push_str(line);
+        }
+        out.push('\n');
+    }
+}
+
+/// Collapse a collection of [`DocFragment`]s into one string,
+/// handling indentation and newlines as needed.
+pub(crate) fn collapse_doc_fragments(doc_strings: &[DocFragment]) -> String {
+    let mut acc = String::new();
+    for frag in doc_strings {
+        add_doc_fragment(&mut acc, frag);
+    }
+    acc.pop();
+    acc
+}
+
+/// Removes excess indentation on comments in order for the Markdown
+/// to be parsed correctly. This is necessary because the convention for
+/// writing documentation is to provide a space between the /// or //! marker
+/// and the doc text, but Markdown is whitespace-sensitive. For example,
+/// a block of text with four-space indentation is parsed as a code block,
+/// so if we didn't unindent comments, these list items
+///
+/// /// A list:
+/// ///
+/// ///    - Foo
+/// ///    - Bar
+///
+/// would be parsed as if they were in a code block, which is likely not what the user intended.
+fn unindent_doc_fragments(docs: &mut Vec<DocFragment>) {
+    // `add` is used in case the most common sugared doc syntax is used ("/// "). The other
+    // fragments kind's lines are never starting with a whitespace unless they are using some
+    // markdown formatting requiring it. Therefore, if the doc block have a mix between the two,
+    // we need to take into account the fact that the minimum indent minus one (to take this
+    // whitespace into account).
+    //
+    // For example:
+    //
+    // /// hello!
+    // #[doc = "another"]
+    //
+    // In this case, you want "hello! another" and not "hello!  another".
+    let add = if docs.windows(2).any(|arr| arr[0].kind != arr[1].kind)
+        && docs.iter().any(|d| d.kind == DocFragmentKind::SugaredDoc)
+    {
+        // In case we have a mix of sugared doc comments and "raw" ones, we want the sugared one to
+        // "decide" how much the minimum indent will be.
+        1
+    } else {
+        0
+    };
+
+    // `min_indent` is used to know how much whitespaces from the start of each lines must be
+    // removed. Example:
+    //
+    // ///     hello!
+    // #[doc = "another"]
+    //
+    // In here, the `min_indent` is 1 (because non-sugared fragment are always counted with minimum
+    // 1 whitespace), meaning that "hello!" will be considered a codeblock because it starts with 4
+    // (5 - 1) whitespaces.
+    let Some(min_indent) = docs
+        .iter()
+        .map(|fragment| {
+            fragment.doc.as_str().lines().fold(usize::MAX, |min_indent, line| {
+                if line.chars().all(|c| c.is_whitespace()) {
+                    min_indent
+                } else {
+                    // Compare against either space or tab, ignoring whether they are
+                    // mixed or not.
+                    let whitespace = line.chars().take_while(|c| *c == ' ' || *c == '\t').count();
+                    cmp::min(min_indent, whitespace)
+                        + if fragment.kind == DocFragmentKind::SugaredDoc { 0 } else { add }
+                }
+            })
+        })
+        .min()
+    else {
+        return;
+    };
+
+    for fragment in docs {
+        if fragment.doc == kw::Empty {
+            continue;
+        }
+
+        let min_indent = if fragment.kind != DocFragmentKind::SugaredDoc && min_indent > 0 {
+            min_indent - add
+        } else {
+            min_indent
+        };
+
+        fragment.indent = min_indent;
+    }
+}
+
+/// A link that has not yet been rendered.
+///
+/// This link will be turned into a rendered link by [`Item::links`].
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) struct ItemLink {
+    /// The original link written in the markdown
+    pub(crate) link: String,
+    /// The link text displayed in the HTML.
+    ///
+    /// This may not be the same as `link` if there was a disambiguator
+    /// in an intra-doc link (e.g. \[`fn@f`\])
+    pub(crate) link_text: String,
+    pub(crate) did: DefId,
+    /// The url fragment to append to the link
+    pub(crate) fragment: Option<UrlFragment>,
+}
+
+pub struct RenderedLink {
+    /// The text the link was original written as.
+    ///
+    /// This could potentially include disambiguators and backticks.
+    pub(crate) original_text: String,
+    /// The text to display in the HTML
+    pub(crate) new_text: String,
+    /// The URL to put in the `href`
+    pub(crate) href: String,
+}
+
+/// The attributes on an [`Item`], including attributes like `#[derive(...)]` and `#[inline]`,
+/// as well as doc comments.
+#[derive(Clone, Debug, Default)]
+pub(crate) struct Attributes {
+    pub(crate) doc_strings: Vec<DocFragment>,
+    pub(crate) other_attrs: Vec<ast::Attribute>,
+}
+
+impl Attributes {
+    pub(crate) fn lists(&self, name: Symbol) -> impl Iterator<Item = ast::NestedMetaItem> + '_ {
+        self.other_attrs.lists(name)
+    }
+
+    pub(crate) fn has_doc_flag(&self, flag: Symbol) -> bool {
+        for attr in &self.other_attrs {
+            if !attr.has_name(sym::doc) {
+                continue;
+            }
+
+            if let Some(items) = attr.meta_item_list() {
+                if items.iter().filter_map(|i| i.meta_item()).any(|it| it.has_name(flag)) {
+                    return true;
+                }
+            }
+        }
+
+        false
+    }
+
+    pub(crate) fn from_ast(attrs: &[ast::Attribute]) -> Attributes {
+        Attributes::from_ast_iter(attrs.iter().map(|attr| (attr, None)), false)
+    }
+
+    pub(crate) fn from_ast_with_additional(
+        attrs: &[ast::Attribute],
+        (additional_attrs, def_id): (&[ast::Attribute], DefId),
+    ) -> Attributes {
+        // Additional documentation should be shown before the original documentation.
+        let attrs1 = additional_attrs.iter().map(|attr| (attr, Some(def_id)));
+        let attrs2 = attrs.iter().map(|attr| (attr, None));
+        Attributes::from_ast_iter(attrs1.chain(attrs2), false)
+    }
+
+    pub(crate) fn from_ast_iter<'a>(
+        attrs: impl Iterator<Item = (&'a ast::Attribute, Option<DefId>)>,
+        doc_only: bool,
+    ) -> Attributes {
+        let mut doc_strings = Vec::new();
+        let mut other_attrs = Vec::new();
+        for (attr, parent_module) in attrs {
+            if let Some((doc_str, comment_kind)) = attr.doc_str_and_comment_kind() {
+                trace!("got doc_str={doc_str:?}");
+                let doc = beautify_doc_string(doc_str, comment_kind);
+                let kind = if attr.is_doc_comment() {
+                    DocFragmentKind::SugaredDoc
+                } else {
+                    DocFragmentKind::RawDoc
+                };
+                let fragment = DocFragment { span: attr.span, doc, kind, parent_module, indent: 0 };
+                doc_strings.push(fragment);
+            } else if !doc_only {
+                other_attrs.push(attr.clone());
+            }
+        }
+
+        unindent_doc_fragments(&mut doc_strings);
+
+        Attributes { doc_strings, other_attrs }
+    }
+
+    /// Finds the `doc` attribute as a NameValue and returns the corresponding
+    /// value found.
+    pub(crate) fn doc_value(&self) -> Option<String> {
+        let mut iter = self.doc_strings.iter();
+
+        let ori = iter.next()?;
+        let mut out = String::new();
+        add_doc_fragment(&mut out, ori);
+        for new_frag in iter {
+            add_doc_fragment(&mut out, new_frag);
+        }
+        out.pop();
+        if out.is_empty() { None } else { Some(out) }
+    }
+
+    /// Return the doc-comments on this item, grouped by the module they came from.
+    /// The module can be different if this is a re-export with added documentation.
+    ///
+    /// The last newline is not trimmed so the produced strings are reusable between
+    /// early and late doc link resolution regardless of their position.
+    pub(crate) fn prepare_to_doc_link_resolution(&self) -> FxHashMap<Option<DefId>, String> {
+        let mut res = FxHashMap::default();
+        for fragment in &self.doc_strings {
+            let out_str = res.entry(fragment.parent_module).or_default();
+            add_doc_fragment(out_str, fragment);
+        }
+        res
+    }
+
+    /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
+    /// with newlines.
+    pub(crate) fn collapsed_doc_value(&self) -> Option<String> {
+        if self.doc_strings.is_empty() {
+            None
+        } else {
+            Some(collapse_doc_fragments(&self.doc_strings))
+        }
+    }
+
+    pub(crate) fn get_doc_aliases(&self) -> Box<[Symbol]> {
+        let mut aliases = FxHashSet::default();
+
+        for attr in self.other_attrs.lists(sym::doc).filter(|a| a.has_name(sym::alias)) {
+            if let Some(values) = attr.meta_item_list() {
+                for l in values {
+                    match l.literal().unwrap().kind {
+                        ast::LitKind::Str(s, _) => {
+                            aliases.insert(s);
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+            } else {
+                aliases.insert(attr.value_str().unwrap());
+            }
+        }
+        aliases.into_iter().collect::<Vec<_>>().into()
+    }
+}
+
+impl PartialEq for Attributes {
+    fn eq(&self, rhs: &Self) -> bool {
+        self.doc_strings == rhs.doc_strings
+            && self
+                .other_attrs
+                .iter()
+                .map(|attr| attr.id)
+                .eq(rhs.other_attrs.iter().map(|attr| attr.id))
+    }
+}
+
+impl Eq for Attributes {}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum GenericBound {
+    TraitBound(PolyTrait, hir::TraitBoundModifier),
+    Outlives(Lifetime),
+}
+
+impl GenericBound {
+    pub(crate) fn maybe_sized(cx: &mut DocContext<'_>) -> GenericBound {
+        let did = cx.tcx.require_lang_item(LangItem::Sized, None);
+        let empty = cx.tcx.intern_substs(&[]);
+        let path = external_path(cx, did, false, vec![], empty);
+        inline::record_extern_fqn(cx, did, ItemType::Trait);
+        GenericBound::TraitBound(
+            PolyTrait { trait_: path, generic_params: Vec::new() },
+            hir::TraitBoundModifier::Maybe,
+        )
+    }
+
+    pub(crate) fn is_sized_bound(&self, cx: &DocContext<'_>) -> bool {
+        use rustc_hir::TraitBoundModifier as TBM;
+        if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, TBM::None) = *self {
+            if Some(trait_.def_id()) == cx.tcx.lang_items().sized_trait() {
+                return true;
+            }
+        }
+        false
+    }
+
+    pub(crate) fn get_poly_trait(&self) -> Option<PolyTrait> {
+        if let GenericBound::TraitBound(ref p, _) = *self {
+            return Some(p.clone());
+        }
+        None
+    }
+
+    pub(crate) fn get_trait_path(&self) -> Option<Path> {
+        if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, _) = *self {
+            Some(trait_.clone())
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct Lifetime(pub Symbol);
+
+impl Lifetime {
+    pub(crate) fn statik() -> Lifetime {
+        Lifetime(kw::StaticLifetime)
+    }
+
+    pub(crate) fn elided() -> Lifetime {
+        Lifetime(kw::UnderscoreLifetime)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum WherePredicate {
+    BoundPredicate { ty: Type, bounds: Vec<GenericBound>, bound_params: Vec<Lifetime> },
+    RegionPredicate { lifetime: Lifetime, bounds: Vec<GenericBound> },
+    EqPredicate { lhs: Type, rhs: Term },
+}
+
+impl WherePredicate {
+    pub(crate) fn get_bounds(&self) -> Option<&[GenericBound]> {
+        match *self {
+            WherePredicate::BoundPredicate { ref bounds, .. } => Some(bounds),
+            WherePredicate::RegionPredicate { ref bounds, .. } => Some(bounds),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum GenericParamDefKind {
+    Lifetime { outlives: Vec<Lifetime> },
+    Type { did: DefId, bounds: Vec<GenericBound>, default: Option<Box<Type>>, synthetic: bool },
+    Const { did: DefId, ty: Box<Type>, default: Option<Box<String>> },
+}
+
+impl GenericParamDefKind {
+    pub(crate) fn is_type(&self) -> bool {
+        matches!(self, GenericParamDefKind::Type { .. })
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct GenericParamDef {
+    pub(crate) name: Symbol,
+    pub(crate) kind: GenericParamDefKind,
+}
+
+impl GenericParamDef {
+    pub(crate) fn is_synthetic_type_param(&self) -> bool {
+        match self.kind {
+            GenericParamDefKind::Lifetime { .. } | GenericParamDefKind::Const { .. } => false,
+            GenericParamDefKind::Type { synthetic, .. } => synthetic,
+        }
+    }
+
+    pub(crate) fn is_type(&self) -> bool {
+        self.kind.is_type()
+    }
+
+    pub(crate) fn get_bounds(&self) -> Option<&[GenericBound]> {
+        match self.kind {
+            GenericParamDefKind::Type { ref bounds, .. } => Some(bounds),
+            _ => None,
+        }
+    }
+}
+
+// maybe use a Generic enum and use Vec<Generic>?
+#[derive(Clone, Debug, Default)]
+pub(crate) struct Generics {
+    pub(crate) params: Vec<GenericParamDef>,
+    pub(crate) where_predicates: Vec<WherePredicate>,
+}
+
+impl Generics {
+    pub(crate) fn is_empty(&self) -> bool {
+        self.params.is_empty() && self.where_predicates.is_empty()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Function {
+    pub(crate) decl: FnDecl,
+    pub(crate) generics: Generics,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct FnDecl {
+    pub(crate) inputs: Arguments,
+    pub(crate) output: FnRetTy,
+    pub(crate) c_variadic: bool,
+}
+
+impl FnDecl {
+    pub(crate) fn self_type(&self) -> Option<SelfTy> {
+        self.inputs.values.get(0).and_then(|v| v.to_self())
+    }
+
+    /// Returns the sugared return type for an async function.
+    ///
+    /// For example, if the return type is `impl std::future::Future<Output = i32>`, this function
+    /// will return `i32`.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if the return type does not match the expected sugaring for async
+    /// functions.
+    pub(crate) fn sugared_async_return_type(&self) -> FnRetTy {
+        match &self.output {
+            FnRetTy::Return(Type::ImplTrait(bounds)) => match &bounds[0] {
+                GenericBound::TraitBound(PolyTrait { trait_, .. }, ..) => {
+                    let bindings = trait_.bindings().unwrap();
+                    let ret_ty = bindings[0].term();
+                    let ty = ret_ty.ty().expect("Unexpected constant return term");
+                    FnRetTy::Return(ty.clone())
+                }
+                _ => panic!("unexpected desugaring of async function"),
+            },
+            _ => panic!("unexpected desugaring of async function"),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct Arguments {
+    pub(crate) values: Vec<Argument>,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct Argument {
+    pub(crate) type_: Type,
+    pub(crate) name: Symbol,
+    /// This field is used to represent "const" arguments from the `rustc_legacy_const_generics`
+    /// feature. More information in <https://github.com/rust-lang/rust/issues/83167>.
+    pub(crate) is_const: bool,
+}
+
+#[derive(Clone, PartialEq, Debug)]
+pub(crate) enum SelfTy {
+    SelfValue,
+    SelfBorrowed(Option<Lifetime>, Mutability),
+    SelfExplicit(Type),
+}
+
+impl Argument {
+    pub(crate) fn to_self(&self) -> Option<SelfTy> {
+        if self.name != kw::SelfLower {
+            return None;
+        }
+        if self.type_.is_self_type() {
+            return Some(SelfValue);
+        }
+        match self.type_ {
+            BorrowedRef { ref lifetime, mutability, ref type_ } if type_.is_self_type() => {
+                Some(SelfBorrowed(lifetime.clone(), mutability))
+            }
+            _ => Some(SelfExplicit(self.type_.clone())),
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum FnRetTy {
+    Return(Type),
+    DefaultReturn,
+}
+
+impl FnRetTy {
+    pub(crate) fn as_return(&self) -> Option<&Type> {
+        match self {
+            Return(ret) => Some(ret),
+            DefaultReturn => None,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Trait {
+    pub(crate) def_id: DefId,
+    pub(crate) items: Vec<Item>,
+    pub(crate) generics: Generics,
+    pub(crate) bounds: Vec<GenericBound>,
+}
+
+impl Trait {
+    pub(crate) fn is_auto(&self, tcx: TyCtxt<'_>) -> bool {
+        tcx.trait_is_auto(self.def_id)
+    }
+    pub(crate) fn unsafety(&self, tcx: TyCtxt<'_>) -> hir::Unsafety {
+        tcx.trait_def(self.def_id).unsafety
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct TraitAlias {
+    pub(crate) generics: Generics,
+    pub(crate) bounds: Vec<GenericBound>,
+}
+
+/// A trait reference, which may have higher ranked lifetimes.
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct PolyTrait {
+    pub(crate) trait_: Path,
+    pub(crate) generic_params: Vec<GenericParamDef>,
+}
+
+/// Rustdoc's representation of types, mostly based on the [`hir::Ty`].
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum Type {
+    /// A named type, which could be a trait.
+    ///
+    /// This is mostly Rustdoc's version of [`hir::Path`].
+    /// It has to be different because Rustdoc's [`PathSegment`] can contain cleaned generics.
+    Path { path: Path },
+    /// A `dyn Trait` object: `dyn for<'a> Trait<'a> + Send + 'static`
+    DynTrait(Vec<PolyTrait>, Option<Lifetime>),
+    /// A type parameter.
+    Generic(Symbol),
+    /// A primitive (aka, builtin) type.
+    Primitive(PrimitiveType),
+    /// A function pointer: `extern "ABI" fn(...) -> ...`
+    BareFunction(Box<BareFunctionDecl>),
+    /// A tuple type: `(i32, &str)`.
+    Tuple(Vec<Type>),
+    /// A slice type (does *not* include the `&`): `[i32]`
+    Slice(Box<Type>),
+    /// An array type.
+    ///
+    /// The `String` field is a stringified version of the array's length parameter.
+    Array(Box<Type>, String),
+    /// A raw pointer type: `*const i32`, `*mut i32`
+    RawPointer(Mutability, Box<Type>),
+    /// A reference type: `&i32`, `&'a mut Foo`
+    BorrowedRef { lifetime: Option<Lifetime>, mutability: Mutability, type_: Box<Type> },
+
+    /// A qualified path to an associated item: `<Type as Trait>::Name`
+    QPath {
+        assoc: Box<PathSegment>,
+        self_type: Box<Type>,
+        /// FIXME: compute this field on demand.
+        should_show_cast: bool,
+        trait_: Path,
+    },
+
+    /// A type that is inferred: `_`
+    Infer,
+
+    /// An `impl Trait`: `impl TraitA + TraitB + ...`
+    ImplTrait(Vec<GenericBound>),
+}
+
+impl Type {
+    /// When comparing types for equality, it can help to ignore `&` wrapping.
+    pub(crate) fn without_borrowed_ref(&self) -> &Type {
+        let mut result = self;
+        while let Type::BorrowedRef { type_, .. } = result {
+            result = &*type_;
+        }
+        result
+    }
+
+    /// Check if two types are "potentially the same".
+    /// This is different from `Eq`, because it knows that things like
+    /// `Placeholder` are possible matches for everything.
+    pub(crate) fn is_same(&self, other: &Self, cache: &Cache) -> bool {
+        match (self, other) {
+            // Recursive cases.
+            (Type::Tuple(a), Type::Tuple(b)) => {
+                a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_same(b, cache))
+            }
+            (Type::Slice(a), Type::Slice(b)) => a.is_same(b, cache),
+            (Type::Array(a, al), Type::Array(b, bl)) => al == bl && a.is_same(b, cache),
+            (Type::RawPointer(mutability, type_), Type::RawPointer(b_mutability, b_type_)) => {
+                mutability == b_mutability && type_.is_same(b_type_, cache)
+            }
+            (
+                Type::BorrowedRef { mutability, type_, .. },
+                Type::BorrowedRef { mutability: b_mutability, type_: b_type_, .. },
+            ) => mutability == b_mutability && type_.is_same(b_type_, cache),
+            // Placeholders and generics are equal to all other types.
+            (Type::Infer, _) | (_, Type::Infer) => true,
+            (Type::Generic(_), _) | (_, Type::Generic(_)) => true,
+            // Other cases, such as primitives, just use recursion.
+            (a, b) => a
+                .def_id(cache)
+                .and_then(|a| Some((a, b.def_id(cache)?)))
+                .map(|(a, b)| a == b)
+                .unwrap_or(false),
+        }
+    }
+
+    pub(crate) fn primitive_type(&self) -> Option<PrimitiveType> {
+        match *self {
+            Primitive(p) | BorrowedRef { type_: box Primitive(p), .. } => Some(p),
+            Slice(..) | BorrowedRef { type_: box Slice(..), .. } => Some(PrimitiveType::Slice),
+            Array(..) | BorrowedRef { type_: box Array(..), .. } => Some(PrimitiveType::Array),
+            Tuple(ref tys) => {
+                if tys.is_empty() {
+                    Some(PrimitiveType::Unit)
+                } else {
+                    Some(PrimitiveType::Tuple)
+                }
+            }
+            RawPointer(..) => Some(PrimitiveType::RawPointer),
+            BareFunction(..) => Some(PrimitiveType::Fn),
+            _ => None,
+        }
+    }
+
+    /// Checks if this is a `T::Name` path for an associated type.
+    pub(crate) fn is_assoc_ty(&self) -> bool {
+        match self {
+            Type::Path { path, .. } => path.is_assoc_ty(),
+            _ => false,
+        }
+    }
+
+    pub(crate) fn is_self_type(&self) -> bool {
+        match *self {
+            Generic(name) => name == kw::SelfUpper,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn generics(&self) -> Option<Vec<&Type>> {
+        match self {
+            Type::Path { path, .. } => path.generics(),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn is_full_generic(&self) -> bool {
+        matches!(self, Type::Generic(_))
+    }
+
+    pub(crate) fn is_impl_trait(&self) -> bool {
+        matches!(self, Type::ImplTrait(_))
+    }
+
+    pub(crate) fn projection(&self) -> Option<(&Type, DefId, PathSegment)> {
+        if let QPath { self_type, trait_, assoc, .. } = self {
+            Some((self_type, trait_.def_id(), *assoc.clone()))
+        } else {
+            None
+        }
+    }
+
+    fn inner_def_id(&self, cache: Option<&Cache>) -> Option<DefId> {
+        let t: PrimitiveType = match *self {
+            Type::Path { ref path } => return Some(path.def_id()),
+            DynTrait(ref bounds, _) => return Some(bounds[0].trait_.def_id()),
+            Primitive(p) => return cache.and_then(|c| c.primitive_locations.get(&p).cloned()),
+            BorrowedRef { type_: box Generic(..), .. } => PrimitiveType::Reference,
+            BorrowedRef { ref type_, .. } => return type_.inner_def_id(cache),
+            Tuple(ref tys) => {
+                if tys.is_empty() {
+                    PrimitiveType::Unit
+                } else {
+                    PrimitiveType::Tuple
+                }
+            }
+            BareFunction(..) => PrimitiveType::Fn,
+            Slice(..) => PrimitiveType::Slice,
+            Array(..) => PrimitiveType::Array,
+            RawPointer(..) => PrimitiveType::RawPointer,
+            QPath { ref self_type, .. } => return self_type.inner_def_id(cache),
+            Generic(_) | Infer | ImplTrait(_) => return None,
+        };
+        cache.and_then(|c| Primitive(t).def_id(c))
+    }
+
+    /// Use this method to get the [DefId] of a [clean] AST node, including [PrimitiveType]s.
+    ///
+    /// [clean]: crate::clean
+    pub(crate) fn def_id(&self, cache: &Cache) -> Option<DefId> {
+        self.inner_def_id(Some(cache))
+    }
+}
+
+/// A primitive (aka, builtin) type.
+///
+/// This represents things like `i32`, `str`, etc.
+///
+/// N.B. This has to be different from [`hir::PrimTy`] because it also includes types that aren't
+/// paths, like [`Self::Unit`].
+#[derive(Clone, PartialEq, Eq, Hash, Copy, Debug)]
+pub(crate) enum PrimitiveType {
+    Isize,
+    I8,
+    I16,
+    I32,
+    I64,
+    I128,
+    Usize,
+    U8,
+    U16,
+    U32,
+    U64,
+    U128,
+    F32,
+    F64,
+    Char,
+    Bool,
+    Str,
+    Slice,
+    Array,
+    Tuple,
+    Unit,
+    RawPointer,
+    Reference,
+    Fn,
+    Never,
+}
+
+type SimplifiedTypes = FxHashMap<PrimitiveType, ArrayVec<SimplifiedType, 3>>;
+impl PrimitiveType {
+    pub(crate) fn from_hir(prim: hir::PrimTy) -> PrimitiveType {
+        use ast::{FloatTy, IntTy, UintTy};
+        match prim {
+            hir::PrimTy::Int(IntTy::Isize) => PrimitiveType::Isize,
+            hir::PrimTy::Int(IntTy::I8) => PrimitiveType::I8,
+            hir::PrimTy::Int(IntTy::I16) => PrimitiveType::I16,
+            hir::PrimTy::Int(IntTy::I32) => PrimitiveType::I32,
+            hir::PrimTy::Int(IntTy::I64) => PrimitiveType::I64,
+            hir::PrimTy::Int(IntTy::I128) => PrimitiveType::I128,
+            hir::PrimTy::Uint(UintTy::Usize) => PrimitiveType::Usize,
+            hir::PrimTy::Uint(UintTy::U8) => PrimitiveType::U8,
+            hir::PrimTy::Uint(UintTy::U16) => PrimitiveType::U16,
+            hir::PrimTy::Uint(UintTy::U32) => PrimitiveType::U32,
+            hir::PrimTy::Uint(UintTy::U64) => PrimitiveType::U64,
+            hir::PrimTy::Uint(UintTy::U128) => PrimitiveType::U128,
+            hir::PrimTy::Float(FloatTy::F32) => PrimitiveType::F32,
+            hir::PrimTy::Float(FloatTy::F64) => PrimitiveType::F64,
+            hir::PrimTy::Str => PrimitiveType::Str,
+            hir::PrimTy::Bool => PrimitiveType::Bool,
+            hir::PrimTy::Char => PrimitiveType::Char,
+        }
+    }
+
+    pub(crate) fn from_symbol(s: Symbol) -> Option<PrimitiveType> {
+        match s {
+            sym::isize => Some(PrimitiveType::Isize),
+            sym::i8 => Some(PrimitiveType::I8),
+            sym::i16 => Some(PrimitiveType::I16),
+            sym::i32 => Some(PrimitiveType::I32),
+            sym::i64 => Some(PrimitiveType::I64),
+            sym::i128 => Some(PrimitiveType::I128),
+            sym::usize => Some(PrimitiveType::Usize),
+            sym::u8 => Some(PrimitiveType::U8),
+            sym::u16 => Some(PrimitiveType::U16),
+            sym::u32 => Some(PrimitiveType::U32),
+            sym::u64 => Some(PrimitiveType::U64),
+            sym::u128 => Some(PrimitiveType::U128),
+            sym::bool => Some(PrimitiveType::Bool),
+            sym::char => Some(PrimitiveType::Char),
+            sym::str => Some(PrimitiveType::Str),
+            sym::f32 => Some(PrimitiveType::F32),
+            sym::f64 => Some(PrimitiveType::F64),
+            sym::array => Some(PrimitiveType::Array),
+            sym::slice => Some(PrimitiveType::Slice),
+            sym::tuple => Some(PrimitiveType::Tuple),
+            sym::unit => Some(PrimitiveType::Unit),
+            sym::pointer => Some(PrimitiveType::RawPointer),
+            sym::reference => Some(PrimitiveType::Reference),
+            kw::Fn => Some(PrimitiveType::Fn),
+            sym::never => Some(PrimitiveType::Never),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn simplified_types() -> &'static SimplifiedTypes {
+        use ty::fast_reject::SimplifiedTypeGen::*;
+        use ty::{FloatTy, IntTy, UintTy};
+        use PrimitiveType::*;
+        static CELL: OnceCell<SimplifiedTypes> = OnceCell::new();
+
+        let single = |x| iter::once(x).collect();
+        CELL.get_or_init(move || {
+            map! {
+                Isize => single(IntSimplifiedType(IntTy::Isize)),
+                I8 => single(IntSimplifiedType(IntTy::I8)),
+                I16 => single(IntSimplifiedType(IntTy::I16)),
+                I32 => single(IntSimplifiedType(IntTy::I32)),
+                I64 => single(IntSimplifiedType(IntTy::I64)),
+                I128 => single(IntSimplifiedType(IntTy::I128)),
+                Usize => single(UintSimplifiedType(UintTy::Usize)),
+                U8 => single(UintSimplifiedType(UintTy::U8)),
+                U16 => single(UintSimplifiedType(UintTy::U16)),
+                U32 => single(UintSimplifiedType(UintTy::U32)),
+                U64 => single(UintSimplifiedType(UintTy::U64)),
+                U128 => single(UintSimplifiedType(UintTy::U128)),
+                F32 => single(FloatSimplifiedType(FloatTy::F32)),
+                F64 => single(FloatSimplifiedType(FloatTy::F64)),
+                Str => single(StrSimplifiedType),
+                Bool => single(BoolSimplifiedType),
+                Char => single(CharSimplifiedType),
+                Array => single(ArraySimplifiedType),
+                Slice => single(SliceSimplifiedType),
+                // FIXME: If we ever add an inherent impl for tuples
+                // with different lengths, they won't show in rustdoc.
+                //
+                // Either manually update this arrayvec at this point
+                // or start with a more complex refactoring.
+                Tuple => [TupleSimplifiedType(1), TupleSimplifiedType(2), TupleSimplifiedType(3)].into(),
+                Unit => single(TupleSimplifiedType(0)),
+                RawPointer => [PtrSimplifiedType(Mutability::Not), PtrSimplifiedType(Mutability::Mut)].into_iter().collect(),
+                Reference => [RefSimplifiedType(Mutability::Not), RefSimplifiedType(Mutability::Mut)].into_iter().collect(),
+                // FIXME: This will be wrong if we ever add inherent impls
+                // for function pointers.
+                Fn => single(FunctionSimplifiedType(1)),
+                Never => single(NeverSimplifiedType),
+            }
+        })
+    }
+
+    pub(crate) fn impls<'tcx>(&self, tcx: TyCtxt<'tcx>) -> impl Iterator<Item = DefId> + 'tcx {
+        Self::simplified_types()
+            .get(self)
+            .into_iter()
+            .flatten()
+            .flat_map(move |&simp| tcx.incoherent_impls(simp))
+            .copied()
+    }
+
+    pub(crate) fn all_impls(tcx: TyCtxt<'_>) -> impl Iterator<Item = DefId> + '_ {
+        Self::simplified_types()
+            .values()
+            .flatten()
+            .flat_map(move |&simp| tcx.incoherent_impls(simp))
+            .copied()
+    }
+
+    pub(crate) fn as_sym(&self) -> Symbol {
+        use PrimitiveType::*;
+        match self {
+            Isize => sym::isize,
+            I8 => sym::i8,
+            I16 => sym::i16,
+            I32 => sym::i32,
+            I64 => sym::i64,
+            I128 => sym::i128,
+            Usize => sym::usize,
+            U8 => sym::u8,
+            U16 => sym::u16,
+            U32 => sym::u32,
+            U64 => sym::u64,
+            U128 => sym::u128,
+            F32 => sym::f32,
+            F64 => sym::f64,
+            Str => sym::str,
+            Bool => sym::bool,
+            Char => sym::char,
+            Array => sym::array,
+            Slice => sym::slice,
+            Tuple => sym::tuple,
+            Unit => sym::unit,
+            RawPointer => sym::pointer,
+            Reference => sym::reference,
+            Fn => kw::Fn,
+            Never => sym::never,
+        }
+    }
+
+    /// Returns the DefId of the module with `doc(primitive)` for this primitive type.
+    /// Panics if there is no such module.
+    ///
+    /// This gives precedence to primitives defined in the current crate, and deprioritizes primitives defined in `core`,
+    /// but otherwise, if multiple crates define the same primitive, there is no guarantee of which will be picked.
+    /// In particular, if a crate depends on both `std` and another crate that also defines `doc(primitive)`, then
+    /// it's entirely random whether `std` or the other crate is picked. (no_std crates are usually fine unless multiple dependencies define a primitive.)
+    pub(crate) fn primitive_locations(tcx: TyCtxt<'_>) -> &FxHashMap<PrimitiveType, DefId> {
+        static PRIMITIVE_LOCATIONS: OnceCell<FxHashMap<PrimitiveType, DefId>> = OnceCell::new();
+        PRIMITIVE_LOCATIONS.get_or_init(|| {
+            let mut primitive_locations = FxHashMap::default();
+            // NOTE: technically this misses crates that are only passed with `--extern` and not loaded when checking the crate.
+            // This is a degenerate case that I don't plan to support.
+            for &crate_num in tcx.crates(()) {
+                let e = ExternalCrate { crate_num };
+                let crate_name = e.name(tcx);
+                debug!(?crate_num, ?crate_name);
+                for &(def_id, prim) in &e.primitives(tcx) {
+                    // HACK: try to link to std instead where possible
+                    if crate_name == sym::core && primitive_locations.contains_key(&prim) {
+                        continue;
+                    }
+                    primitive_locations.insert(prim, def_id);
+                }
+            }
+            let local_primitives = ExternalCrate { crate_num: LOCAL_CRATE }.primitives(tcx);
+            for (def_id, prim) in local_primitives {
+                primitive_locations.insert(prim, def_id);
+            }
+            primitive_locations
+        })
+    }
+}
+
+impl From<ast::IntTy> for PrimitiveType {
+    fn from(int_ty: ast::IntTy) -> PrimitiveType {
+        match int_ty {
+            ast::IntTy::Isize => PrimitiveType::Isize,
+            ast::IntTy::I8 => PrimitiveType::I8,
+            ast::IntTy::I16 => PrimitiveType::I16,
+            ast::IntTy::I32 => PrimitiveType::I32,
+            ast::IntTy::I64 => PrimitiveType::I64,
+            ast::IntTy::I128 => PrimitiveType::I128,
+        }
+    }
+}
+
+impl From<ast::UintTy> for PrimitiveType {
+    fn from(uint_ty: ast::UintTy) -> PrimitiveType {
+        match uint_ty {
+            ast::UintTy::Usize => PrimitiveType::Usize,
+            ast::UintTy::U8 => PrimitiveType::U8,
+            ast::UintTy::U16 => PrimitiveType::U16,
+            ast::UintTy::U32 => PrimitiveType::U32,
+            ast::UintTy::U64 => PrimitiveType::U64,
+            ast::UintTy::U128 => PrimitiveType::U128,
+        }
+    }
+}
+
+impl From<ast::FloatTy> for PrimitiveType {
+    fn from(float_ty: ast::FloatTy) -> PrimitiveType {
+        match float_ty {
+            ast::FloatTy::F32 => PrimitiveType::F32,
+            ast::FloatTy::F64 => PrimitiveType::F64,
+        }
+    }
+}
+
+impl From<ty::IntTy> for PrimitiveType {
+    fn from(int_ty: ty::IntTy) -> PrimitiveType {
+        match int_ty {
+            ty::IntTy::Isize => PrimitiveType::Isize,
+            ty::IntTy::I8 => PrimitiveType::I8,
+            ty::IntTy::I16 => PrimitiveType::I16,
+            ty::IntTy::I32 => PrimitiveType::I32,
+            ty::IntTy::I64 => PrimitiveType::I64,
+            ty::IntTy::I128 => PrimitiveType::I128,
+        }
+    }
+}
+
+impl From<ty::UintTy> for PrimitiveType {
+    fn from(uint_ty: ty::UintTy) -> PrimitiveType {
+        match uint_ty {
+            ty::UintTy::Usize => PrimitiveType::Usize,
+            ty::UintTy::U8 => PrimitiveType::U8,
+            ty::UintTy::U16 => PrimitiveType::U16,
+            ty::UintTy::U32 => PrimitiveType::U32,
+            ty::UintTy::U64 => PrimitiveType::U64,
+            ty::UintTy::U128 => PrimitiveType::U128,
+        }
+    }
+}
+
+impl From<ty::FloatTy> for PrimitiveType {
+    fn from(float_ty: ty::FloatTy) -> PrimitiveType {
+        match float_ty {
+            ty::FloatTy::F32 => PrimitiveType::F32,
+            ty::FloatTy::F64 => PrimitiveType::F64,
+        }
+    }
+}
+
+impl From<hir::PrimTy> for PrimitiveType {
+    fn from(prim_ty: hir::PrimTy) -> PrimitiveType {
+        match prim_ty {
+            hir::PrimTy::Int(int_ty) => int_ty.into(),
+            hir::PrimTy::Uint(uint_ty) => uint_ty.into(),
+            hir::PrimTy::Float(float_ty) => float_ty.into(),
+            hir::PrimTy::Str => PrimitiveType::Str,
+            hir::PrimTy::Bool => PrimitiveType::Bool,
+            hir::PrimTy::Char => PrimitiveType::Char,
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) enum Visibility {
+    /// `pub`
+    Public,
+    /// Visibility inherited from parent.
+    ///
+    /// For example, this is the visibility of private items and of enum variants.
+    Inherited,
+    /// `pub(crate)`, `pub(super)`, or `pub(in path::to::somewhere)`
+    Restricted(DefId),
+}
+
+impl Visibility {
+    pub(crate) fn is_public(&self) -> bool {
+        matches!(self, Visibility::Public)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Struct {
+    pub(crate) struct_type: CtorKind,
+    pub(crate) generics: Generics,
+    pub(crate) fields: Vec<Item>,
+}
+
+impl Struct {
+    pub(crate) fn has_stripped_entries(&self) -> bool {
+        self.fields.iter().any(|f| f.is_stripped())
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Union {
+    pub(crate) generics: Generics,
+    pub(crate) fields: Vec<Item>,
+}
+
+impl Union {
+    pub(crate) fn has_stripped_entries(&self) -> bool {
+        self.fields.iter().any(|f| f.is_stripped())
+    }
+}
+
+/// This is a more limited form of the standard Struct, different in that
+/// it lacks the things most items have (name, id, parameterization). Found
+/// only as a variant in an enum.
+#[derive(Clone, Debug)]
+pub(crate) struct VariantStruct {
+    pub(crate) struct_type: CtorKind,
+    pub(crate) fields: Vec<Item>,
+}
+
+impl VariantStruct {
+    pub(crate) fn has_stripped_entries(&self) -> bool {
+        self.fields.iter().any(|f| f.is_stripped())
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Enum {
+    pub(crate) variants: IndexVec<VariantIdx, Item>,
+    pub(crate) generics: Generics,
+}
+
+impl Enum {
+    pub(crate) fn has_stripped_entries(&self) -> bool {
+        self.variants.iter().any(|f| f.is_stripped())
+    }
+
+    pub(crate) fn variants(&self) -> impl Iterator<Item = &Item> {
+        self.variants.iter().filter(|v| !v.is_stripped())
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum Variant {
+    CLike,
+    Tuple(Vec<Item>),
+    Struct(VariantStruct),
+}
+
+impl Variant {
+    pub(crate) fn has_stripped_entries(&self) -> Option<bool> {
+        match *self {
+            Self::Struct(ref struct_) => Some(struct_.has_stripped_entries()),
+            Self::CLike | Self::Tuple(_) => None,
+        }
+    }
+}
+
+/// Small wrapper around [`rustc_span::Span`] that adds helper methods
+/// and enforces calling [`rustc_span::Span::source_callsite()`].
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct Span(rustc_span::Span);
+
+impl Span {
+    /// Wraps a [`rustc_span::Span`]. In case this span is the result of a macro expansion, the
+    /// span will be updated to point to the macro invocation instead of the macro definition.
+    ///
+    /// (See rust-lang/rust#39726)
+    pub(crate) fn new(sp: rustc_span::Span) -> Self {
+        Self(sp.source_callsite())
+    }
+
+    pub(crate) fn inner(&self) -> rustc_span::Span {
+        self.0
+    }
+
+    pub(crate) fn dummy() -> Self {
+        Self(rustc_span::DUMMY_SP)
+    }
+
+    pub(crate) fn is_dummy(&self) -> bool {
+        self.0.is_dummy()
+    }
+
+    pub(crate) fn filename(&self, sess: &Session) -> FileName {
+        sess.source_map().span_to_filename(self.0)
+    }
+
+    pub(crate) fn lo(&self, sess: &Session) -> Loc {
+        sess.source_map().lookup_char_pos(self.0.lo())
+    }
+
+    pub(crate) fn hi(&self, sess: &Session) -> Loc {
+        sess.source_map().lookup_char_pos(self.0.hi())
+    }
+
+    pub(crate) fn cnum(&self, sess: &Session) -> CrateNum {
+        // FIXME: is there a time when the lo and hi crate would be different?
+        self.lo(sess).file.cnum
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct Path {
+    pub(crate) res: Res,
+    pub(crate) segments: Vec<PathSegment>,
+}
+
+impl Path {
+    pub(crate) fn def_id(&self) -> DefId {
+        self.res.def_id()
+    }
+
+    pub(crate) fn last_opt(&self) -> Option<Symbol> {
+        self.segments.last().map(|s| s.name)
+    }
+
+    pub(crate) fn last(&self) -> Symbol {
+        self.last_opt().expect("segments were empty")
+    }
+
+    pub(crate) fn whole_name(&self) -> String {
+        self.segments
+            .iter()
+            .map(|s| if s.name == kw::PathRoot { "" } else { s.name.as_str() })
+            .intersperse("::")
+            .collect()
+    }
+
+    /// Checks if this is a `T::Name` path for an associated type.
+    pub(crate) fn is_assoc_ty(&self) -> bool {
+        match self.res {
+            Res::SelfTy { .. } if self.segments.len() != 1 => true,
+            Res::Def(DefKind::TyParam, _) if self.segments.len() != 1 => true,
+            Res::Def(DefKind::AssocTy, _) => true,
+            _ => false,
+        }
+    }
+
+    pub(crate) fn generics(&self) -> Option<Vec<&Type>> {
+        self.segments.last().and_then(|seg| {
+            if let GenericArgs::AngleBracketed { ref args, .. } = seg.args {
+                Some(
+                    args.iter()
+                        .filter_map(|arg| match arg {
+                            GenericArg::Type(ty) => Some(ty),
+                            _ => None,
+                        })
+                        .collect(),
+                )
+            } else {
+                None
+            }
+        })
+    }
+
+    pub(crate) fn bindings(&self) -> Option<&[TypeBinding]> {
+        self.segments.last().and_then(|seg| {
+            if let GenericArgs::AngleBracketed { ref bindings, .. } = seg.args {
+                Some(&**bindings)
+            } else {
+                None
+            }
+        })
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum GenericArg {
+    Lifetime(Lifetime),
+    Type(Type),
+    Const(Box<Constant>),
+    Infer,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum GenericArgs {
+    AngleBracketed { args: Box<[GenericArg]>, bindings: ThinVec<TypeBinding> },
+    Parenthesized { inputs: Box<[Type]>, output: Option<Box<Type>> },
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct PathSegment {
+    pub(crate) name: Symbol,
+    pub(crate) args: GenericArgs,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Typedef {
+    pub(crate) type_: Type,
+    pub(crate) generics: Generics,
+    /// `type_` can come from either the HIR or from metadata. If it comes from HIR, it may be a type
+    /// alias instead of the final type. This will always have the final type, regardless of whether
+    /// `type_` came from HIR or from metadata.
+    ///
+    /// If `item_type.is_none()`, `type_` is guaranteed to come from metadata (and therefore hold the
+    /// final type).
+    pub(crate) item_type: Option<Type>,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct OpaqueTy {
+    pub(crate) bounds: Vec<GenericBound>,
+    pub(crate) generics: Generics,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct BareFunctionDecl {
+    pub(crate) unsafety: hir::Unsafety,
+    pub(crate) generic_params: Vec<GenericParamDef>,
+    pub(crate) decl: FnDecl,
+    pub(crate) abi: Abi,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Static {
+    pub(crate) type_: Type,
+    pub(crate) mutability: Mutability,
+    pub(crate) expr: Option<BodyId>,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) struct Constant {
+    pub(crate) type_: Type,
+    pub(crate) kind: ConstantKind,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) enum Term {
+    Type(Type),
+    Constant(Constant),
+}
+
+impl Term {
+    pub(crate) fn ty(&self) -> Option<&Type> {
+        if let Term::Type(ty) = self { Some(ty) } else { None }
+    }
+}
+
+impl From<Type> for Term {
+    fn from(ty: Type) -> Self {
+        Term::Type(ty)
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub(crate) enum ConstantKind {
+    /// This is the wrapper around `ty::Const` for a non-local constant. Because it doesn't have a
+    /// `BodyId`, we need to handle it on its own.
+    ///
+    /// Note that `ty::Const` includes generic parameters, and may not always be uniquely identified
+    /// by a DefId. So this field must be different from `Extern`.
+    TyConst { expr: String },
+    /// A constant (expression) that's not an item or associated item. These are usually found
+    /// nested inside types (e.g., array lengths) or expressions (e.g., repeat counts), and also
+    /// used to define explicit discriminant values for enum variants.
+    Anonymous { body: BodyId },
+    /// A constant from a different crate.
+    Extern { def_id: DefId },
+    /// `const FOO: u32 = ...;`
+    Local { def_id: DefId, body: BodyId },
+}
+
+impl Constant {
+    pub(crate) fn expr(&self, tcx: TyCtxt<'_>) -> String {
+        self.kind.expr(tcx)
+    }
+
+    pub(crate) fn value(&self, tcx: TyCtxt<'_>) -> Option<String> {
+        self.kind.value(tcx)
+    }
+
+    pub(crate) fn is_literal(&self, tcx: TyCtxt<'_>) -> bool {
+        self.kind.is_literal(tcx)
+    }
+}
+
+impl ConstantKind {
+    pub(crate) fn expr(&self, tcx: TyCtxt<'_>) -> String {
+        match *self {
+            ConstantKind::TyConst { ref expr } => expr.clone(),
+            ConstantKind::Extern { def_id } => print_inlined_const(tcx, def_id),
+            ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
+                print_const_expr(tcx, body)
+            }
+        }
+    }
+
+    pub(crate) fn value(&self, tcx: TyCtxt<'_>) -> Option<String> {
+        match *self {
+            ConstantKind::TyConst { .. } | ConstantKind::Anonymous { .. } => None,
+            ConstantKind::Extern { def_id } | ConstantKind::Local { def_id, .. } => {
+                print_evaluated_const(tcx, def_id)
+            }
+        }
+    }
+
+    pub(crate) fn is_literal(&self, tcx: TyCtxt<'_>) -> bool {
+        match *self {
+            ConstantKind::TyConst { .. } => false,
+            ConstantKind::Extern { def_id } => def_id.as_local().map_or(false, |def_id| {
+                is_literal_expr(tcx, tcx.hir().local_def_id_to_hir_id(def_id))
+            }),
+            ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
+                is_literal_expr(tcx, body.hir_id)
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Impl {
+    pub(crate) unsafety: hir::Unsafety,
+    pub(crate) generics: Generics,
+    pub(crate) trait_: Option<Path>,
+    pub(crate) for_: Type,
+    pub(crate) items: Vec<Item>,
+    pub(crate) polarity: ty::ImplPolarity,
+    pub(crate) kind: ImplKind,
+}
+
+impl Impl {
+    pub(crate) fn provided_trait_methods(&self, tcx: TyCtxt<'_>) -> FxHashSet<Symbol> {
+        self.trait_
+            .as_ref()
+            .map(|t| t.def_id())
+            .map(|did| tcx.provided_trait_methods(did).map(|meth| meth.name).collect())
+            .unwrap_or_default()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum ImplKind {
+    Normal,
+    Auto,
+    FakeVaradic,
+    Blanket(Box<Type>),
+}
+
+impl ImplKind {
+    pub(crate) fn is_auto(&self) -> bool {
+        matches!(self, ImplKind::Auto)
+    }
+
+    pub(crate) fn is_blanket(&self) -> bool {
+        matches!(self, ImplKind::Blanket(_))
+    }
+
+    pub(crate) fn is_fake_variadic(&self) -> bool {
+        matches!(self, ImplKind::FakeVaradic)
+    }
+
+    pub(crate) fn as_blanket_ty(&self) -> Option<&Type> {
+        match self {
+            ImplKind::Blanket(ty) => Some(ty),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Import {
+    pub(crate) kind: ImportKind,
+    pub(crate) source: ImportSource,
+    pub(crate) should_be_displayed: bool,
+}
+
+impl Import {
+    pub(crate) fn new_simple(
+        name: Symbol,
+        source: ImportSource,
+        should_be_displayed: bool,
+    ) -> Self {
+        Self { kind: ImportKind::Simple(name), source, should_be_displayed }
+    }
+
+    pub(crate) fn new_glob(source: ImportSource, should_be_displayed: bool) -> Self {
+        Self { kind: ImportKind::Glob, source, should_be_displayed }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum ImportKind {
+    // use source as str;
+    Simple(Symbol),
+    // use source::*;
+    Glob,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct ImportSource {
+    pub(crate) path: Path,
+    pub(crate) did: Option<DefId>,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct Macro {
+    pub(crate) source: String,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct ProcMacro {
+    pub(crate) kind: MacroKind,
+    pub(crate) helpers: Vec<Symbol>,
+}
+
+/// An type binding on an associated type (e.g., `A = Bar` in `Foo<A = Bar>` or
+/// `A: Send + Sync` in `Foo<A: Send + Sync>`).
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct TypeBinding {
+    pub(crate) assoc: PathSegment,
+    pub(crate) kind: TypeBindingKind,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) enum TypeBindingKind {
+    Equality { term: Term },
+    Constraint { bounds: Vec<GenericBound> },
+}
+
+impl TypeBinding {
+    pub(crate) fn term(&self) -> &Term {
+        match self.kind {
+            TypeBindingKind::Equality { ref term } => term,
+            _ => panic!("expected equality type binding for parenthesized generic args"),
+        }
+    }
+}
+
+/// The type, lifetime, or constant that a private type alias's parameter should be
+/// replaced with when expanding a use of that type alias.
+///
+/// For example:
+///
+/// ```
+/// type PrivAlias<T> = Vec<T>;
+///
+/// pub fn public_fn() -> PrivAlias<i32> { vec![] }
+/// ```
+///
+/// `public_fn`'s docs will show it as returning `Vec<i32>`, since `PrivAlias` is private.
+/// [`SubstParam`] is used to record that `T` should be mapped to `i32`.
+pub(crate) enum SubstParam {
+    Type(Type),
+    Lifetime(Lifetime),
+    Constant(Constant),
+}
+
+impl SubstParam {
+    pub(crate) fn as_ty(&self) -> Option<&Type> {
+        if let Self::Type(ty) = self { Some(ty) } else { None }
+    }
+
+    pub(crate) fn as_lt(&self) -> Option<&Lifetime> {
+        if let Self::Lifetime(lt) = self { Some(lt) } else { None }
+    }
+}
+
+// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+mod size_asserts {
+    use super::*;
+    // These are in alphabetical order, which is easy to maintain.
+    rustc_data_structures::static_assert_size!(Crate, 72); // frequently moved by-value
+    rustc_data_structures::static_assert_size!(DocFragment, 32);
+    rustc_data_structures::static_assert_size!(GenericArg, 80);
+    rustc_data_structures::static_assert_size!(GenericArgs, 32);
+    rustc_data_structures::static_assert_size!(GenericParamDef, 56);
+    rustc_data_structures::static_assert_size!(Item, 56);
+    rustc_data_structures::static_assert_size!(ItemKind, 112);
+    rustc_data_structures::static_assert_size!(PathSegment, 40);
+    rustc_data_structures::static_assert_size!(Type, 72);
+}
diff --git a/src/librustdoc/clean/types/tests.rs b/src/librustdoc/clean/types/tests.rs
new file mode 100644
index 000000000..71eddf434
--- /dev/null
+++ b/src/librustdoc/clean/types/tests.rs
@@ -0,0 +1,70 @@
+use super::*;
+
+use crate::clean::collapse_doc_fragments;
+
+use rustc_span::create_default_session_globals_then;
+use rustc_span::source_map::DUMMY_SP;
+use rustc_span::symbol::Symbol;
+
+fn create_doc_fragment(s: &str) -> Vec<DocFragment> {
+    vec![DocFragment {
+        span: DUMMY_SP,
+        parent_module: None,
+        doc: Symbol::intern(s),
+        kind: DocFragmentKind::SugaredDoc,
+        indent: 0,
+    }]
+}
+
+#[track_caller]
+fn run_test(input: &str, expected: &str) {
+    create_default_session_globals_then(|| {
+        let mut s = create_doc_fragment(input);
+        unindent_doc_fragments(&mut s);
+        assert_eq!(collapse_doc_fragments(&s), expected);
+    });
+}
+
+#[test]
+fn should_unindent() {
+    run_test("    line1\n    line2", "line1\nline2");
+}
+
+#[test]
+fn should_unindent_multiple_paragraphs() {
+    run_test("    line1\n\n    line2", "line1\n\nline2");
+}
+
+#[test]
+fn should_leave_multiple_indent_levels() {
+    // Line 2 is indented another level beyond the
+    // base indentation and should be preserved
+    run_test("    line1\n\n        line2", "line1\n\n    line2");
+}
+
+#[test]
+fn should_ignore_first_line_indent() {
+    run_test("line1\n    line2", "line1\n    line2");
+}
+
+#[test]
+fn should_not_ignore_first_line_indent_in_a_single_line_para() {
+    run_test("line1\n\n    line2", "line1\n\n    line2");
+}
+
+#[test]
+fn should_unindent_tabs() {
+    run_test("\tline1\n\tline2", "line1\nline2");
+}
+
+#[test]
+fn should_trim_mixed_indentation() {
+    run_test("\t    line1\n\t    line2", "line1\nline2");
+    run_test("    \tline1\n    \tline2", "line1\nline2");
+}
+
+#[test]
+fn should_not_trim() {
+    run_test("\t    line1  \n\t    line2", "line1  \nline2");
+    run_test("    \tline1  \n    \tline2", "line1  \nline2");
+}
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
new file mode 100644
index 000000000..43e71e90a
--- /dev/null
+++ b/src/librustdoc/clean/utils.rs
@@ -0,0 +1,616 @@
+use crate::clean::auto_trait::AutoTraitFinder;
+use crate::clean::blanket_impl::BlanketImplFinder;
+use crate::clean::render_macro_matchers::render_macro_matcher;
+use crate::clean::{
+    clean_middle_const, clean_middle_region, clean_middle_ty, inline, Clean, Crate, ExternalCrate,
+    Generic, GenericArg, GenericArgs, ImportSource, Item, ItemKind, Lifetime, Path, PathSegment,
+    Primitive, PrimitiveType, Type, TypeBinding, Visibility,
+};
+use crate::core::DocContext;
+use crate::formats::item_type::ItemType;
+use crate::visit_lib::LibEmbargoVisitor;
+
+use rustc_ast as ast;
+use rustc_ast::tokenstream::TokenTree;
+use rustc_data_structures::thin_vec::ThinVec;
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_middle::mir;
+use rustc_middle::mir::interpret::ConstValue;
+use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
+use rustc_middle::ty::{self, DefIdTree, TyCtxt};
+use rustc_span::symbol::{kw, sym, Symbol};
+use std::fmt::Write as _;
+use std::mem;
+
+#[cfg(test)]
+mod tests;
+
+pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
+    let module = crate::visit_ast::RustdocVisitor::new(cx).visit();
+
+    for &cnum in cx.tcx.crates(()) {
+        // Analyze doc-reachability for extern items
+        LibEmbargoVisitor::new(cx).visit_lib(cnum);
+    }
+
+    // Clean the crate, translating the entire librustc_ast AST to one that is
+    // understood by rustdoc.
+    let mut module = module.clean(cx);
+
+    match *module.kind {
+        ItemKind::ModuleItem(ref module) => {
+            for it in &module.items {
+                // `compiler_builtins` should be masked too, but we can't apply
+                // `#[doc(masked)]` to the injected `extern crate` because it's unstable.
+                if it.is_extern_crate()
+                    && (it.attrs.has_doc_flag(sym::masked)
+                        || cx.tcx.is_compiler_builtins(it.item_id.krate()))
+                {
+                    cx.cache.masked_crates.insert(it.item_id.krate());
+                }
+            }
+        }
+        _ => unreachable!(),
+    }
+
+    let local_crate = ExternalCrate { crate_num: LOCAL_CRATE };
+    let primitives = local_crate.primitives(cx.tcx);
+    let keywords = local_crate.keywords(cx.tcx);
+    {
+        let ItemKind::ModuleItem(ref mut m) = *module.kind
+        else { unreachable!() };
+        m.items.extend(primitives.iter().map(|&(def_id, prim)| {
+            Item::from_def_id_and_parts(
+                def_id,
+                Some(prim.as_sym()),
+                ItemKind::PrimitiveItem(prim),
+                cx,
+            )
+        }));
+        m.items.extend(keywords.into_iter().map(|(def_id, kw)| {
+            Item::from_def_id_and_parts(def_id, Some(kw), ItemKind::KeywordItem, cx)
+        }));
+    }
+
+    Crate { module, primitives, external_traits: cx.external_traits.clone() }
+}
+
+pub(crate) fn substs_to_args<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    substs: &[ty::subst::GenericArg<'tcx>],
+    mut skip_first: bool,
+) -> Vec<GenericArg> {
+    let mut ret_val =
+        Vec::with_capacity(substs.len().saturating_sub(if skip_first { 1 } else { 0 }));
+    ret_val.extend(substs.iter().filter_map(|kind| match kind.unpack() {
+        GenericArgKind::Lifetime(lt) => {
+            Some(GenericArg::Lifetime(clean_middle_region(lt).unwrap_or(Lifetime::elided())))
+        }
+        GenericArgKind::Type(_) if skip_first => {
+            skip_first = false;
+            None
+        }
+        GenericArgKind::Type(ty) => Some(GenericArg::Type(clean_middle_ty(ty, cx, None))),
+        GenericArgKind::Const(ct) => Some(GenericArg::Const(Box::new(clean_middle_const(ct, cx)))),
+    }));
+    ret_val
+}
+
+fn external_generic_args<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    did: DefId,
+    has_self: bool,
+    bindings: Vec<TypeBinding>,
+    substs: SubstsRef<'tcx>,
+) -> GenericArgs {
+    let args = substs_to_args(cx, substs, has_self);
+
+    if cx.tcx.fn_trait_kind_from_lang_item(did).is_some() {
+        let inputs =
+            // The trait's first substitution is the one after self, if there is one.
+            match substs.iter().nth(if has_self { 1 } else { 0 }).unwrap().expect_ty().kind() {
+                ty::Tuple(tys) => tys.iter().map(|t| clean_middle_ty(t, cx, None)).collect::<Vec<_>>().into(),
+                _ => return GenericArgs::AngleBracketed { args: args.into(), bindings: bindings.into() },
+            };
+        let output = None;
+        // FIXME(#20299) return type comes from a projection now
+        // match types[1].kind {
+        //     ty::Tuple(ref v) if v.is_empty() => None, // -> ()
+        //     _ => Some(types[1].clean(cx))
+        // };
+        GenericArgs::Parenthesized { inputs, output }
+    } else {
+        GenericArgs::AngleBracketed { args: args.into(), bindings: bindings.into() }
+    }
+}
+
+pub(super) fn external_path<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    did: DefId,
+    has_self: bool,
+    bindings: Vec<TypeBinding>,
+    substs: SubstsRef<'tcx>,
+) -> Path {
+    let def_kind = cx.tcx.def_kind(did);
+    let name = cx.tcx.item_name(did);
+    Path {
+        res: Res::Def(def_kind, did),
+        segments: vec![PathSegment {
+            name,
+            args: external_generic_args(cx, did, has_self, bindings, substs),
+        }],
+    }
+}
+
+/// Remove the generic arguments from a path.
+pub(crate) fn strip_path_generics(mut path: Path) -> Path {
+    for ps in path.segments.iter_mut() {
+        ps.args = GenericArgs::AngleBracketed { args: Default::default(), bindings: ThinVec::new() }
+    }
+
+    path
+}
+
+pub(crate) fn qpath_to_string(p: &hir::QPath<'_>) -> String {
+    let segments = match *p {
+        hir::QPath::Resolved(_, path) => &path.segments,
+        hir::QPath::TypeRelative(_, segment) => return segment.ident.to_string(),
+        hir::QPath::LangItem(lang_item, ..) => return lang_item.name().to_string(),
+    };
+
+    let mut s = String::new();
+    for (i, seg) in segments.iter().enumerate() {
+        if i > 0 {
+            s.push_str("::");
+        }
+        if seg.ident.name != kw::PathRoot {
+            s.push_str(seg.ident.as_str());
+        }
+    }
+    s
+}
+
+pub(crate) fn build_deref_target_impls(
+    cx: &mut DocContext<'_>,
+    items: &[Item],
+    ret: &mut Vec<Item>,
+) {
+    let tcx = cx.tcx;
+
+    for item in items {
+        let target = match *item.kind {
+            ItemKind::AssocTypeItem(ref t, _) => &t.type_,
+            _ => continue,
+        };
+
+        if let Some(prim) = target.primitive_type() {
+            let _prof_timer = cx.tcx.sess.prof.generic_activity("build_primitive_inherent_impls");
+            for did in prim.impls(tcx).filter(|did| !did.is_local()) {
+                inline::build_impl(cx, None, did, None, ret);
+            }
+        } else if let Type::Path { path } = target {
+            let did = path.def_id();
+            if !did.is_local() {
+                inline::build_impls(cx, None, did, None, ret);
+            }
+        }
+    }
+}
+
+pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
+    use rustc_hir::*;
+    debug!("trying to get a name from pattern: {:?}", p);
+
+    Symbol::intern(&match p.kind {
+        PatKind::Wild | PatKind::Struct(..) => return kw::Underscore,
+        PatKind::Binding(_, _, ident, _) => return ident.name,
+        PatKind::TupleStruct(ref p, ..) | PatKind::Path(ref p) => qpath_to_string(p),
+        PatKind::Or(pats) => {
+            pats.iter().map(|p| name_from_pat(p).to_string()).collect::<Vec<String>>().join(" | ")
+        }
+        PatKind::Tuple(elts, _) => format!(
+            "({})",
+            elts.iter().map(|p| name_from_pat(p).to_string()).collect::<Vec<String>>().join(", ")
+        ),
+        PatKind::Box(p) => return name_from_pat(&*p),
+        PatKind::Ref(p, _) => return name_from_pat(&*p),
+        PatKind::Lit(..) => {
+            warn!(
+                "tried to get argument name from PatKind::Lit, which is silly in function arguments"
+            );
+            return Symbol::intern("()");
+        }
+        PatKind::Range(..) => return kw::Underscore,
+        PatKind::Slice(begin, ref mid, end) => {
+            let begin = begin.iter().map(|p| name_from_pat(p).to_string());
+            let mid = mid.as_ref().map(|p| format!("..{}", name_from_pat(&**p))).into_iter();
+            let end = end.iter().map(|p| name_from_pat(p).to_string());
+            format!("[{}]", begin.chain(mid).chain(end).collect::<Vec<_>>().join(", "))
+        }
+    })
+}
+
+pub(crate) fn print_const(cx: &DocContext<'_>, n: ty::Const<'_>) -> String {
+    match n.kind() {
+        ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs: _, promoted }) => {
+            let mut s = if let Some(def) = def.as_local() {
+                print_const_expr(cx.tcx, cx.tcx.hir().body_owned_by(def.did))
+            } else {
+                inline::print_inlined_const(cx.tcx, def.did)
+            };
+            if let Some(promoted) = promoted {
+                s.push_str(&format!("::{:?}", promoted))
+            }
+            s
+        }
+        _ => {
+            let mut s = n.to_string();
+            // array lengths are obviously usize
+            if s.ends_with("_usize") {
+                let n = s.len() - "_usize".len();
+                s.truncate(n);
+                if s.ends_with(": ") {
+                    let n = s.len() - ": ".len();
+                    s.truncate(n);
+                }
+            }
+            s
+        }
+    }
+}
+
+pub(crate) fn print_evaluated_const(tcx: TyCtxt<'_>, def_id: DefId) -> Option<String> {
+    tcx.const_eval_poly(def_id).ok().and_then(|val| {
+        let ty = tcx.type_of(def_id);
+        match (val, ty.kind()) {
+            (_, &ty::Ref(..)) => None,
+            (ConstValue::Scalar(_), &ty::Adt(_, _)) => None,
+            (ConstValue::Scalar(_), _) => {
+                let const_ = mir::ConstantKind::from_value(val, ty);
+                Some(print_const_with_custom_print_scalar(tcx, const_))
+            }
+            _ => None,
+        }
+    })
+}
+
+fn format_integer_with_underscore_sep(num: &str) -> String {
+    let num_chars: Vec<_> = num.chars().collect();
+    let mut num_start_index = if num_chars.get(0) == Some(&'-') { 1 } else { 0 };
+    let chunk_size = match num[num_start_index..].as_bytes() {
+        [b'0', b'b' | b'x', ..] => {
+            num_start_index += 2;
+            4
+        }
+        [b'0', b'o', ..] => {
+            num_start_index += 2;
+            let remaining_chars = num_chars.len() - num_start_index;
+            if remaining_chars <= 6 {
+                // don't add underscores to Unix permissions like 0755 or 100755
+                return num.to_string();
+            }
+            3
+        }
+        _ => 3,
+    };
+
+    num_chars[..num_start_index]
+        .iter()
+        .chain(num_chars[num_start_index..].rchunks(chunk_size).rev().intersperse(&['_']).flatten())
+        .collect()
+}
+
+fn print_const_with_custom_print_scalar(tcx: TyCtxt<'_>, ct: mir::ConstantKind<'_>) -> String {
+    // Use a slightly different format for integer types which always shows the actual value.
+    // For all other types, fallback to the original `pretty_print_const`.
+    match (ct, ct.ty().kind()) {
+        (mir::ConstantKind::Val(ConstValue::Scalar(int), _), ty::Uint(ui)) => {
+            format!("{}{}", format_integer_with_underscore_sep(&int.to_string()), ui.name_str())
+        }
+        (mir::ConstantKind::Val(ConstValue::Scalar(int), _), ty::Int(i)) => {
+            let ty = tcx.lift(ct.ty()).unwrap();
+            let size = tcx.layout_of(ty::ParamEnv::empty().and(ty)).unwrap().size;
+            let data = int.assert_bits(size);
+            let sign_extended_data = size.sign_extend(data) as i128;
+            format!(
+                "{}{}",
+                format_integer_with_underscore_sep(&sign_extended_data.to_string()),
+                i.name_str()
+            )
+        }
+        _ => ct.to_string(),
+    }
+}
+
+pub(crate) fn is_literal_expr(tcx: TyCtxt<'_>, hir_id: hir::HirId) -> bool {
+    if let hir::Node::Expr(expr) = tcx.hir().get(hir_id) {
+        if let hir::ExprKind::Lit(_) = &expr.kind {
+            return true;
+        }
+
+        if let hir::ExprKind::Unary(hir::UnOp::Neg, expr) = &expr.kind {
+            if let hir::ExprKind::Lit(_) = &expr.kind {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+/// Build a textual representation of an unevaluated constant expression.
+///
+/// If the const expression is too complex, an underscore `_` is returned.
+/// For const arguments, it's `{ _ }` to be precise.
+/// This means that the output is not necessarily valid Rust code.
+///
+/// Currently, only
+///
+/// * literals (optionally with a leading `-`)
+/// * unit `()`
+/// * blocks (`{ … }`) around simple expressions and
+/// * paths without arguments
+///
+/// are considered simple enough. Simple blocks are included since they are
+/// necessary to disambiguate unit from the unit type.
+/// This list might get extended in the future.
+///
+/// Without this censoring, in a lot of cases the output would get too large
+/// and verbose. Consider `match` expressions, blocks and deeply nested ADTs.
+/// Further, private and `doc(hidden)` fields of structs would get leaked
+/// since HIR datatypes like the `body` parameter do not contain enough
+/// semantic information for this function to be able to hide them –
+/// at least not without significant performance overhead.
+///
+/// Whenever possible, prefer to evaluate the constant first and try to
+/// use a different method for pretty-printing. Ideally this function
+/// should only ever be used as a fallback.
+pub(crate) fn print_const_expr(tcx: TyCtxt<'_>, body: hir::BodyId) -> String {
+    let hir = tcx.hir();
+    let value = &hir.body(body).value;
+
+    #[derive(PartialEq, Eq)]
+    enum Classification {
+        Literal,
+        Simple,
+        Complex,
+    }
+
+    use Classification::*;
+
+    fn classify(expr: &hir::Expr<'_>) -> Classification {
+        match &expr.kind {
+            hir::ExprKind::Unary(hir::UnOp::Neg, expr) => {
+                if matches!(expr.kind, hir::ExprKind::Lit(_)) { Literal } else { Complex }
+            }
+            hir::ExprKind::Lit(_) => Literal,
+            hir::ExprKind::Tup([]) => Simple,
+            hir::ExprKind::Block(hir::Block { stmts: [], expr: Some(expr), .. }, _) => {
+                if classify(expr) == Complex { Complex } else { Simple }
+            }
+            // Paths with a self-type or arguments are too “complex” following our measure since
+            // they may leak private fields of structs (with feature `adt_const_params`).
+            // Consider: `<Self as Trait<{ Struct { private: () } }>>::CONSTANT`.
+            // Paths without arguments are definitely harmless though.
+            hir::ExprKind::Path(hir::QPath::Resolved(_, hir::Path { segments, .. })) => {
+                if segments.iter().all(|segment| segment.args.is_none()) { Simple } else { Complex }
+            }
+            // FIXME: Claiming that those kinds of QPaths are simple is probably not true if the Ty
+            //        contains const arguments. Is there a *concise* way to check for this?
+            hir::ExprKind::Path(hir::QPath::TypeRelative(..)) => Simple,
+            // FIXME: Can they contain const arguments and thus leak private struct fields?
+            hir::ExprKind::Path(hir::QPath::LangItem(..)) => Simple,
+            _ => Complex,
+        }
+    }
+
+    let classification = classify(value);
+
+    if classification == Literal
+    && !value.span.from_expansion()
+    && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(value.span) {
+        // For literals, we avoid invoking the pretty-printer and use the source snippet instead to
+        // preserve certain stylistic choices the user likely made for the sake legibility like
+        //
+        // * hexadecimal notation
+        // * underscores
+        // * character escapes
+        //
+        // FIXME: This passes through `-/*spacer*/0` verbatim.
+        snippet
+    } else if classification == Simple {
+        // Otherwise we prefer pretty-printing to get rid of extraneous whitespace, comments and
+        // other formatting artifacts.
+        rustc_hir_pretty::id_to_string(&hir, body.hir_id)
+    } else if tcx.def_kind(hir.body_owner_def_id(body).to_def_id()) == DefKind::AnonConst {
+        // FIXME: Omit the curly braces if the enclosing expression is an array literal
+        //        with a repeated element (an `ExprKind::Repeat`) as in such case it
+        //        would not actually need any disambiguation.
+        "{ _ }".to_owned()
+    } else {
+        "_".to_owned()
+    }
+}
+
+/// Given a type Path, resolve it to a Type using the TyCtxt
+pub(crate) fn resolve_type(cx: &mut DocContext<'_>, path: Path) -> Type {
+    debug!("resolve_type({:?})", path);
+
+    match path.res {
+        Res::PrimTy(p) => Primitive(PrimitiveType::from(p)),
+        Res::SelfTy { .. } if path.segments.len() == 1 => Generic(kw::SelfUpper),
+        Res::Def(DefKind::TyParam, _) if path.segments.len() == 1 => Generic(path.segments[0].name),
+        _ => {
+            let _ = register_res(cx, path.res);
+            Type::Path { path }
+        }
+    }
+}
+
+pub(crate) fn get_auto_trait_and_blanket_impls(
+    cx: &mut DocContext<'_>,
+    item_def_id: DefId,
+) -> impl Iterator<Item = Item> {
+    let auto_impls = cx
+        .sess()
+        .prof
+        .generic_activity("get_auto_trait_impls")
+        .run(|| AutoTraitFinder::new(cx).get_auto_trait_impls(item_def_id));
+    let blanket_impls = cx
+        .sess()
+        .prof
+        .generic_activity("get_blanket_impls")
+        .run(|| BlanketImplFinder { cx }.get_blanket_impls(item_def_id));
+    auto_impls.into_iter().chain(blanket_impls)
+}
+
+/// If `res` has a documentation page associated, store it in the cache.
+///
+/// This is later used by [`href()`] to determine the HTML link for the item.
+///
+/// [`href()`]: crate::html::format::href
+pub(crate) fn register_res(cx: &mut DocContext<'_>, res: Res) -> DefId {
+    use DefKind::*;
+    debug!("register_res({:?})", res);
+
+    let (did, kind) = match res {
+        // These should be added to the cache using `record_extern_fqn`.
+        Res::Def(
+            kind @ (AssocTy | AssocFn | AssocConst | Variant | Fn | TyAlias | Enum | Trait | Struct
+            | Union | Mod | ForeignTy | Const | Static(_) | Macro(..) | TraitAlias),
+            i,
+        ) => (i, kind.into()),
+        // This is part of a trait definition or trait impl; document the trait.
+        Res::SelfTy { trait_: Some(trait_def_id), alias_to: _ } => (trait_def_id, ItemType::Trait),
+        // This is an inherent impl or a type definition; it doesn't have its own page.
+        Res::SelfTy { trait_: None, alias_to: Some((item_def_id, _)) } => return item_def_id,
+        Res::SelfTy { trait_: None, alias_to: None }
+        | Res::PrimTy(_)
+        | Res::ToolMod
+        | Res::SelfCtor(_)
+        | Res::Local(_)
+        | Res::NonMacroAttr(_)
+        | Res::Err => return res.def_id(),
+        Res::Def(
+            TyParam | ConstParam | Ctor(..) | ExternCrate | Use | ForeignMod | AnonConst
+            | InlineConst | OpaqueTy | Field | LifetimeParam | GlobalAsm | Impl | Closure
+            | Generator,
+            id,
+        ) => return id,
+    };
+    if did.is_local() {
+        return did;
+    }
+    inline::record_extern_fqn(cx, did, kind);
+    if let ItemType::Trait = kind {
+        inline::record_extern_trait(cx, did);
+    }
+    did
+}
+
+pub(crate) fn resolve_use_source(cx: &mut DocContext<'_>, path: Path) -> ImportSource {
+    ImportSource {
+        did: if path.res.opt_def_id().is_none() { None } else { Some(register_res(cx, path.res)) },
+        path,
+    }
+}
+
+pub(crate) fn enter_impl_trait<'tcx, F, R>(cx: &mut DocContext<'tcx>, f: F) -> R
+where
+    F: FnOnce(&mut DocContext<'tcx>) -> R,
+{
+    let old_bounds = mem::take(&mut cx.impl_trait_bounds);
+    let r = f(cx);
+    assert!(cx.impl_trait_bounds.is_empty());
+    cx.impl_trait_bounds = old_bounds;
+    r
+}
+
+/// Find the nearest parent module of a [`DefId`].
+pub(crate) fn find_nearest_parent_module(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
+    if def_id.is_top_level_module() {
+        // The crate root has no parent. Use it as the root instead.
+        Some(def_id)
+    } else {
+        let mut current = def_id;
+        // The immediate parent might not always be a module.
+        // Find the first parent which is.
+        while let Some(parent) = tcx.opt_parent(current) {
+            if tcx.def_kind(parent) == DefKind::Mod {
+                return Some(parent);
+            }
+            current = parent;
+        }
+        None
+    }
+}
+
+/// Checks for the existence of `hidden` in the attribute below if `flag` is `sym::hidden`:
+///
+/// ```
+/// #[doc(hidden)]
+/// pub fn foo() {}
+/// ```
+///
+/// This function exists because it runs on `hir::Attributes` whereas the other is a
+/// `clean::Attributes` method.
+pub(crate) fn has_doc_flag(tcx: TyCtxt<'_>, did: DefId, flag: Symbol) -> bool {
+    tcx.get_attrs(did, sym::doc).any(|attr| {
+        attr.meta_item_list().map_or(false, |l| rustc_attr::list_contains_name(&l, flag))
+    })
+}
+
+/// A link to `doc.rust-lang.org` that includes the channel name. Use this instead of manual links
+/// so that the channel is consistent.
+///
+/// Set by `bootstrap::Builder::doc_rust_lang_org_channel` in order to keep tests passing on beta/stable.
+pub(crate) const DOC_RUST_LANG_ORG_CHANNEL: &str = env!("DOC_RUST_LANG_ORG_CHANNEL");
+
+/// Render a sequence of macro arms in a format suitable for displaying to the user
+/// as part of an item declaration.
+pub(super) fn render_macro_arms<'a>(
+    tcx: TyCtxt<'_>,
+    matchers: impl Iterator<Item = &'a TokenTree>,
+    arm_delim: &str,
+) -> String {
+    let mut out = String::new();
+    for matcher in matchers {
+        writeln!(out, "    {} => {{ ... }}{}", render_macro_matcher(tcx, matcher), arm_delim)
+            .unwrap();
+    }
+    out
+}
+
+pub(super) fn display_macro_source(
+    cx: &mut DocContext<'_>,
+    name: Symbol,
+    def: &ast::MacroDef,
+    def_id: DefId,
+    vis: Visibility,
+) -> String {
+    let tts: Vec<_> = def.body.inner_tokens().into_trees().collect();
+    // Extract the spans of all matchers. They represent the "interface" of the macro.
+    let matchers = tts.chunks(4).map(|arm| &arm[0]);
+
+    if def.macro_rules {
+        format!("macro_rules! {} {{\n{}}}", name, render_macro_arms(cx.tcx, matchers, ";"))
+    } else {
+        if matchers.len() <= 1 {
+            format!(
+                "{}macro {}{} {{\n    ...\n}}",
+                vis.to_src_with_space(cx.tcx, def_id),
+                name,
+                matchers.map(|matcher| render_macro_matcher(cx.tcx, matcher)).collect::<String>(),
+            )
+        } else {
+            format!(
+                "{}macro {} {{\n{}}}",
+                vis.to_src_with_space(cx.tcx, def_id),
+                name,
+                render_macro_arms(cx.tcx, matchers, ","),
+            )
+        }
+    }
+}
diff --git a/src/librustdoc/clean/utils/tests.rs b/src/librustdoc/clean/utils/tests.rs
new file mode 100644
index 000000000..ebf4b4954
--- /dev/null
+++ b/src/librustdoc/clean/utils/tests.rs
@@ -0,0 +1,41 @@
+use super::*;
+
+#[test]
+fn int_format_decimal() {
+    assert_eq!(format_integer_with_underscore_sep("12345678"), "12_345_678");
+    assert_eq!(format_integer_with_underscore_sep("123"), "123");
+    assert_eq!(format_integer_with_underscore_sep("123459"), "123_459");
+    assert_eq!(format_integer_with_underscore_sep("-12345678"), "-12_345_678");
+    assert_eq!(format_integer_with_underscore_sep("-123"), "-123");
+    assert_eq!(format_integer_with_underscore_sep("-123459"), "-123_459");
+}
+
+#[test]
+fn int_format_hex() {
+    assert_eq!(format_integer_with_underscore_sep("0xab3"), "0xab3");
+    assert_eq!(format_integer_with_underscore_sep("0xa2345b"), "0xa2_345b");
+    assert_eq!(format_integer_with_underscore_sep("0xa2e6345b"), "0xa2e6_345b");
+    assert_eq!(format_integer_with_underscore_sep("-0xab3"), "-0xab3");
+    assert_eq!(format_integer_with_underscore_sep("-0xa2345b"), "-0xa2_345b");
+    assert_eq!(format_integer_with_underscore_sep("-0xa2e6345b"), "-0xa2e6_345b");
+}
+
+#[test]
+fn int_format_binary() {
+    assert_eq!(format_integer_with_underscore_sep("0o12345671"), "0o12_345_671");
+    assert_eq!(format_integer_with_underscore_sep("0o123"), "0o123");
+    assert_eq!(format_integer_with_underscore_sep("0o123451"), "0o123451");
+    assert_eq!(format_integer_with_underscore_sep("-0o12345671"), "-0o12_345_671");
+    assert_eq!(format_integer_with_underscore_sep("-0o123"), "-0o123");
+    assert_eq!(format_integer_with_underscore_sep("-0o123451"), "-0o123451");
+}
+
+#[test]
+fn int_format_octal() {
+    assert_eq!(format_integer_with_underscore_sep("0b101"), "0b101");
+    assert_eq!(format_integer_with_underscore_sep("0b101101011"), "0b1_0110_1011");
+    assert_eq!(format_integer_with_underscore_sep("0b01101011"), "0b0110_1011");
+    assert_eq!(format_integer_with_underscore_sep("-0b101"), "-0b101");
+    assert_eq!(format_integer_with_underscore_sep("-0b101101011"), "-0b1_0110_1011");
+    assert_eq!(format_integer_with_underscore_sep("-0b01101011"), "-0b0110_1011");
+}
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
new file mode 100644
index 000000000..8a8cc272e
--- /dev/null
+++ b/src/librustdoc/config.rs
@@ -0,0 +1,828 @@
+use std::collections::BTreeMap;
+use std::convert::TryFrom;
+use std::ffi::OsStr;
+use std::fmt;
+use std::path::PathBuf;
+use std::str::FromStr;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_driver::print_flag_list;
+use rustc_session::config::{
+    self, parse_crate_types_from_list, parse_externs, parse_target_triple, CrateType,
+};
+use rustc_session::config::{get_cmd_lint_options, nightly_options};
+use rustc_session::config::{
+    CodegenOptions, ErrorOutputType, Externs, JsonUnusedExterns, UnstableOptions,
+};
+use rustc_session::getopts;
+use rustc_session::lint::Level;
+use rustc_session::search_paths::SearchPath;
+use rustc_span::edition::Edition;
+use rustc_target::spec::TargetTriple;
+
+use crate::core::new_handler;
+use crate::externalfiles::ExternalHtml;
+use crate::html;
+use crate::html::markdown::IdMap;
+use crate::html::render::StylePath;
+use crate::html::static_files;
+use crate::opts;
+use crate::passes::{self, Condition};
+use crate::scrape_examples::{AllCallLocations, ScrapeExamplesOptions};
+use crate::theme;
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub(crate) enum OutputFormat {
+    Json,
+    Html,
+}
+
+impl Default for OutputFormat {
+    fn default() -> OutputFormat {
+        OutputFormat::Html
+    }
+}
+
+impl OutputFormat {
+    pub(crate) fn is_json(&self) -> bool {
+        matches!(self, OutputFormat::Json)
+    }
+}
+
+impl TryFrom<&str> for OutputFormat {
+    type Error = String;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        match value {
+            "json" => Ok(OutputFormat::Json),
+            "html" => Ok(OutputFormat::Html),
+            _ => Err(format!("unknown output format `{}`", value)),
+        }
+    }
+}
+
+/// Configuration options for rustdoc.
+#[derive(Clone)]
+pub(crate) struct Options {
+    // Basic options / Options passed directly to rustc
+    /// The crate root or Markdown file to load.
+    pub(crate) input: PathBuf,
+    /// The name of the crate being documented.
+    pub(crate) crate_name: Option<String>,
+    /// Whether or not this is a proc-macro crate
+    pub(crate) proc_macro_crate: bool,
+    /// How to format errors and warnings.
+    pub(crate) error_format: ErrorOutputType,
+    /// Width of output buffer to truncate errors appropriately.
+    pub(crate) diagnostic_width: Option<usize>,
+    /// Library search paths to hand to the compiler.
+    pub(crate) libs: Vec<SearchPath>,
+    /// Library search paths strings to hand to the compiler.
+    pub(crate) lib_strs: Vec<String>,
+    /// The list of external crates to link against.
+    pub(crate) externs: Externs,
+    /// The list of external crates strings to link against.
+    pub(crate) extern_strs: Vec<String>,
+    /// List of `cfg` flags to hand to the compiler. Always includes `rustdoc`.
+    pub(crate) cfgs: Vec<String>,
+    /// List of check cfg flags to hand to the compiler.
+    pub(crate) check_cfgs: Vec<String>,
+    /// Codegen options to hand to the compiler.
+    pub(crate) codegen_options: CodegenOptions,
+    /// Codegen options strings to hand to the compiler.
+    pub(crate) codegen_options_strs: Vec<String>,
+    /// Unstable (`-Z`) options to pass to the compiler.
+    pub(crate) unstable_opts: UnstableOptions,
+    /// Unstable (`-Z`) options strings to pass to the compiler.
+    pub(crate) unstable_opts_strs: Vec<String>,
+    /// The target used to compile the crate against.
+    pub(crate) target: TargetTriple,
+    /// Edition used when reading the crate. Defaults to "2015". Also used by default when
+    /// compiling doctests from the crate.
+    pub(crate) edition: Edition,
+    /// The path to the sysroot. Used during the compilation process.
+    pub(crate) maybe_sysroot: Option<PathBuf>,
+    /// Lint information passed over the command-line.
+    pub(crate) lint_opts: Vec<(String, Level)>,
+    /// Whether to ask rustc to describe the lints it knows.
+    pub(crate) describe_lints: bool,
+    /// What level to cap lints at.
+    pub(crate) lint_cap: Option<Level>,
+
+    // Options specific to running doctests
+    /// Whether we should run doctests instead of generating docs.
+    pub(crate) should_test: bool,
+    /// List of arguments to pass to the test harness, if running tests.
+    pub(crate) test_args: Vec<String>,
+    /// The working directory in which to run tests.
+    pub(crate) test_run_directory: Option<PathBuf>,
+    /// Optional path to persist the doctest executables to, defaults to a
+    /// temporary directory if not set.
+    pub(crate) persist_doctests: Option<PathBuf>,
+    /// Runtool to run doctests with
+    pub(crate) runtool: Option<String>,
+    /// Arguments to pass to the runtool
+    pub(crate) runtool_args: Vec<String>,
+    /// Whether to allow ignoring doctests on a per-target basis
+    /// For example, using ignore-foo to ignore running the doctest on any target that
+    /// contains "foo" as a substring
+    pub(crate) enable_per_target_ignores: bool,
+    /// Do not run doctests, compile them if should_test is active.
+    pub(crate) no_run: bool,
+
+    /// The path to a rustc-like binary to build tests with. If not set, we
+    /// default to loading from `$sysroot/bin/rustc`.
+    pub(crate) test_builder: Option<PathBuf>,
+
+    // Options that affect the documentation process
+    /// Whether to run the `calculate-doc-coverage` pass, which counts the number of public items
+    /// with and without documentation.
+    pub(crate) show_coverage: bool,
+
+    // Options that alter generated documentation pages
+    /// Crate version to note on the sidebar of generated docs.
+    pub(crate) crate_version: Option<String>,
+    /// Collected options specific to outputting final pages.
+    pub(crate) render_options: RenderOptions,
+    /// The format that we output when rendering.
+    ///
+    /// Currently used only for the `--show-coverage` option.
+    pub(crate) output_format: OutputFormat,
+    /// If this option is set to `true`, rustdoc will only run checks and not generate
+    /// documentation.
+    pub(crate) run_check: bool,
+    /// Whether doctests should emit unused externs
+    pub(crate) json_unused_externs: JsonUnusedExterns,
+    /// Whether to skip capturing stdout and stderr of tests.
+    pub(crate) nocapture: bool,
+
+    /// Configuration for scraping examples from the current crate. If this option is Some(..) then
+    /// the compiler will scrape examples and not generate documentation.
+    pub(crate) scrape_examples_options: Option<ScrapeExamplesOptions>,
+}
+
+impl fmt::Debug for Options {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        struct FmtExterns<'a>(&'a Externs);
+
+        impl<'a> fmt::Debug for FmtExterns<'a> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.debug_map().entries(self.0.iter()).finish()
+            }
+        }
+
+        f.debug_struct("Options")
+            .field("input", &self.input)
+            .field("crate_name", &self.crate_name)
+            .field("proc_macro_crate", &self.proc_macro_crate)
+            .field("error_format", &self.error_format)
+            .field("libs", &self.libs)
+            .field("externs", &FmtExterns(&self.externs))
+            .field("cfgs", &self.cfgs)
+            .field("check-cfgs", &self.check_cfgs)
+            .field("codegen_options", &"...")
+            .field("unstable_options", &"...")
+            .field("target", &self.target)
+            .field("edition", &self.edition)
+            .field("maybe_sysroot", &self.maybe_sysroot)
+            .field("lint_opts", &self.lint_opts)
+            .field("describe_lints", &self.describe_lints)
+            .field("lint_cap", &self.lint_cap)
+            .field("should_test", &self.should_test)
+            .field("test_args", &self.test_args)
+            .field("test_run_directory", &self.test_run_directory)
+            .field("persist_doctests", &self.persist_doctests)
+            .field("show_coverage", &self.show_coverage)
+            .field("crate_version", &self.crate_version)
+            .field("render_options", &self.render_options)
+            .field("runtool", &self.runtool)
+            .field("runtool_args", &self.runtool_args)
+            .field("enable-per-target-ignores", &self.enable_per_target_ignores)
+            .field("run_check", &self.run_check)
+            .field("no_run", &self.no_run)
+            .field("nocapture", &self.nocapture)
+            .field("scrape_examples_options", &self.scrape_examples_options)
+            .finish()
+    }
+}
+
+/// Configuration options for the HTML page-creation process.
+#[derive(Clone, Debug)]
+pub(crate) struct RenderOptions {
+    /// Output directory to generate docs into. Defaults to `doc`.
+    pub(crate) output: PathBuf,
+    /// External files to insert into generated pages.
+    pub(crate) external_html: ExternalHtml,
+    /// A pre-populated `IdMap` with the default headings and any headings added by Markdown files
+    /// processed by `external_html`.
+    pub(crate) id_map: IdMap,
+    /// If present, playground URL to use in the "Run" button added to code samples.
+    ///
+    /// Be aware: This option can come both from the CLI and from crate attributes!
+    pub(crate) playground_url: Option<String>,
+    /// What sorting mode to use for module pages.
+    /// `ModuleSorting::Alphabetical` by default.
+    pub(crate) module_sorting: ModuleSorting,
+    /// List of themes to extend the docs with. Original argument name is included to assist in
+    /// displaying errors if it fails a theme check.
+    pub(crate) themes: Vec<StylePath>,
+    /// If present, CSS file that contains rules to add to the default CSS.
+    pub(crate) extension_css: Option<PathBuf>,
+    /// A map of crate names to the URL to use instead of querying the crate's `html_root_url`.
+    pub(crate) extern_html_root_urls: BTreeMap<String, String>,
+    /// Whether to give precedence to `html_root_url` or `--exten-html-root-url`.
+    pub(crate) extern_html_root_takes_precedence: bool,
+    /// A map of the default settings (values are as for DOM storage API). Keys should lack the
+    /// `rustdoc-` prefix.
+    pub(crate) default_settings: FxHashMap<String, String>,
+    /// If present, suffix added to CSS/JavaScript files when referencing them in generated pages.
+    pub(crate) resource_suffix: String,
+    /// Whether to run the static CSS/JavaScript through a minifier when outputting them. `true` by
+    /// default.
+    pub(crate) enable_minification: bool,
+    /// Whether to create an index page in the root of the output directory. If this is true but
+    /// `enable_index_page` is None, generate a static listing of crates instead.
+    pub(crate) enable_index_page: bool,
+    /// A file to use as the index page at the root of the output directory. Overrides
+    /// `enable_index_page` to be true if set.
+    pub(crate) index_page: Option<PathBuf>,
+    /// An optional path to use as the location of static files. If not set, uses combinations of
+    /// `../` to reach the documentation root.
+    pub(crate) static_root_path: Option<String>,
+
+    // Options specific to reading standalone Markdown files
+    /// Whether to generate a table of contents on the output file when reading a standalone
+    /// Markdown file.
+    pub(crate) markdown_no_toc: bool,
+    /// Additional CSS files to link in pages generated from standalone Markdown files.
+    pub(crate) markdown_css: Vec<String>,
+    /// If present, playground URL to use in the "Run" button added to code samples generated from
+    /// standalone Markdown files. If not present, `playground_url` is used.
+    pub(crate) markdown_playground_url: Option<String>,
+    /// Document items that have lower than `pub` visibility.
+    pub(crate) document_private: bool,
+    /// Document items that have `doc(hidden)`.
+    pub(crate) document_hidden: bool,
+    /// If `true`, generate a JSON file in the crate folder instead of HTML redirection files.
+    pub(crate) generate_redirect_map: bool,
+    /// Show the memory layout of types in the docs.
+    pub(crate) show_type_layout: bool,
+    pub(crate) unstable_features: rustc_feature::UnstableFeatures,
+    pub(crate) emit: Vec<EmitType>,
+    /// If `true`, HTML source pages will generate links for items to their definition.
+    pub(crate) generate_link_to_definition: bool,
+    /// Set of function-call locations to include as examples
+    pub(crate) call_locations: AllCallLocations,
+    /// If `true`, Context::init will not emit shared files.
+    pub(crate) no_emit_shared: bool,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub(crate) enum ModuleSorting {
+    DeclarationOrder,
+    Alphabetical,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub(crate) enum EmitType {
+    Unversioned,
+    Toolchain,
+    InvocationSpecific,
+}
+
+impl FromStr for EmitType {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        use EmitType::*;
+        match s {
+            "unversioned-shared-resources" => Ok(Unversioned),
+            "toolchain-shared-resources" => Ok(Toolchain),
+            "invocation-specific" => Ok(InvocationSpecific),
+            _ => Err(()),
+        }
+    }
+}
+
+impl RenderOptions {
+    pub(crate) fn should_emit_crate(&self) -> bool {
+        self.emit.is_empty() || self.emit.contains(&EmitType::InvocationSpecific)
+    }
+}
+
+impl Options {
+    /// Parses the given command-line for options. If an error message or other early-return has
+    /// been printed, returns `Err` with the exit code.
+    pub(crate) fn from_matches(
+        matches: &getopts::Matches,
+        args: Vec<String>,
+    ) -> Result<Options, i32> {
+        let args = &args[1..];
+        // Check for unstable options.
+        nightly_options::check_nightly_options(matches, &opts());
+
+        if args.is_empty() || matches.opt_present("h") || matches.opt_present("help") {
+            crate::usage("rustdoc");
+            return Err(0);
+        } else if matches.opt_present("version") {
+            rustc_driver::version("rustdoc", matches);
+            return Err(0);
+        }
+
+        let z_flags = matches.opt_strs("Z");
+        if z_flags.iter().any(|x| *x == "help") {
+            print_flag_list("-Z", config::Z_OPTIONS);
+            return Err(0);
+        }
+        let c_flags = matches.opt_strs("C");
+        if c_flags.iter().any(|x| *x == "help") {
+            print_flag_list("-C", config::CG_OPTIONS);
+            return Err(0);
+        }
+
+        let color = config::parse_color(matches);
+        let config::JsonConfig { json_rendered, json_unused_externs, .. } =
+            config::parse_json(matches);
+        let error_format = config::parse_error_format(matches, color, json_rendered);
+        let diagnostic_width = matches.opt_get("diagnostic-width").unwrap_or_default();
+
+        let codegen_options = CodegenOptions::build(matches, error_format);
+        let unstable_opts = UnstableOptions::build(matches, error_format);
+
+        let diag = new_handler(error_format, None, diagnostic_width, &unstable_opts);
+
+        // check for deprecated options
+        check_deprecated_options(matches, &diag);
+
+        if matches.opt_strs("passes") == ["list"] {
+            println!("Available passes for running rustdoc:");
+            for pass in passes::PASSES {
+                println!("{:>20} - {}", pass.name, pass.description);
+            }
+            println!("\nDefault passes for rustdoc:");
+            for p in passes::DEFAULT_PASSES {
+                print!("{:>20}", p.pass.name);
+                println_condition(p.condition);
+            }
+
+            if nightly_options::match_is_nightly_build(matches) {
+                println!("\nPasses run with `--show-coverage`:");
+                for p in passes::COVERAGE_PASSES {
+                    print!("{:>20}", p.pass.name);
+                    println_condition(p.condition);
+                }
+            }
+
+            fn println_condition(condition: Condition) {
+                use Condition::*;
+                match condition {
+                    Always => println!(),
+                    WhenDocumentPrivate => println!("  (when --document-private-items)"),
+                    WhenNotDocumentPrivate => println!("  (when not --document-private-items)"),
+                    WhenNotDocumentHidden => println!("  (when not --document-hidden-items)"),
+                }
+            }
+
+            return Err(0);
+        }
+
+        let mut emit = Vec::new();
+        for list in matches.opt_strs("emit") {
+            for kind in list.split(',') {
+                match kind.parse() {
+                    Ok(kind) => emit.push(kind),
+                    Err(()) => {
+                        diag.err(&format!("unrecognized emission type: {}", kind));
+                        return Err(1);
+                    }
+                }
+            }
+        }
+
+        // check for `--output-format=json`
+        if !matches!(matches.opt_str("output-format").as_deref(), None | Some("html"))
+            && !matches.opt_present("show-coverage")
+            && !nightly_options::is_unstable_enabled(matches)
+        {
+            rustc_session::early_error(
+                error_format,
+                "the -Z unstable-options flag must be passed to enable --output-format for documentation generation (see https://github.com/rust-lang/rust/issues/76578)",
+            );
+        }
+
+        let to_check = matches.opt_strs("check-theme");
+        if !to_check.is_empty() {
+            let paths = theme::load_css_paths(static_files::themes::LIGHT.as_bytes());
+            let mut errors = 0;
+
+            println!("rustdoc: [check-theme] Starting tests! (Ignoring all other arguments)");
+            for theme_file in to_check.iter() {
+                print!(" - Checking \"{}\"...", theme_file);
+                let (success, differences) = theme::test_theme_against(theme_file, &paths, &diag);
+                if !differences.is_empty() || !success {
+                    println!(" FAILED");
+                    errors += 1;
+                    if !differences.is_empty() {
+                        println!("{}", differences.join("\n"));
+                    }
+                } else {
+                    println!(" OK");
+                }
+            }
+            if errors != 0 {
+                return Err(1);
+            }
+            return Err(0);
+        }
+
+        let (lint_opts, describe_lints, lint_cap) = get_cmd_lint_options(matches, error_format);
+
+        let input = PathBuf::from(if describe_lints {
+            "" // dummy, this won't be used
+        } else if matches.free.is_empty() {
+            diag.struct_err("missing file operand").emit();
+            return Err(1);
+        } else if matches.free.len() > 1 {
+            diag.struct_err("too many file operands").emit();
+            return Err(1);
+        } else {
+            &matches.free[0]
+        });
+
+        let libs = matches
+            .opt_strs("L")
+            .iter()
+            .map(|s| SearchPath::from_cli_opt(s, error_format))
+            .collect();
+        let externs = parse_externs(matches, &unstable_opts, error_format);
+        let extern_html_root_urls = match parse_extern_html_roots(matches) {
+            Ok(ex) => ex,
+            Err(err) => {
+                diag.struct_err(err).emit();
+                return Err(1);
+            }
+        };
+
+        let default_settings: Vec<Vec<(String, String)>> = vec![
+            matches
+                .opt_str("default-theme")
+                .iter()
+                .flat_map(|theme| {
+                    vec![
+                        ("use-system-theme".to_string(), "false".to_string()),
+                        ("theme".to_string(), theme.to_string()),
+                    ]
+                })
+                .collect(),
+            matches
+                .opt_strs("default-setting")
+                .iter()
+                .map(|s| match s.split_once('=') {
+                    None => (s.clone(), "true".to_string()),
+                    Some((k, v)) => (k.to_string(), v.to_string()),
+                })
+                .collect(),
+        ];
+        let default_settings = default_settings
+            .into_iter()
+            .flatten()
+            .map(
+                // The keys here become part of `data-` attribute names in the generated HTML.  The
+                // browser does a strange mapping when converting them into attributes on the
+                // `dataset` property on the DOM HTML Node:
+                //   https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/dataset
+                //
+                // The original key values we have are the same as the DOM storage API keys and the
+                // command line options, so contain `-`.  Our Javascript needs to be able to look
+                // these values up both in `dataset` and in the storage API, so it needs to be able
+                // to convert the names back and forth.  Despite doing this kebab-case to
+                // StudlyCaps transformation automatically, the JS DOM API does not provide a
+                // mechanism for doing the just transformation on a string.  So we want to avoid
+                // the StudlyCaps representation in the `dataset` property.
+                //
+                // We solve this by replacing all the `-`s with `_`s.  We do that here, when we
+                // generate the `data-` attributes, and in the JS, when we look them up.  (See
+                // `getSettingValue` in `storage.js.`) Converting `-` to `_` is simple in JS.
+                //
+                // The values will be HTML-escaped by the default Tera escaping.
+                |(k, v)| (k.replace('-', "_"), v),
+            )
+            .collect();
+
+        let test_args = matches.opt_strs("test-args");
+        let test_args: Vec<String> =
+            test_args.iter().flat_map(|s| s.split_whitespace()).map(|s| s.to_string()).collect();
+
+        let should_test = matches.opt_present("test");
+        let no_run = matches.opt_present("no-run");
+
+        if !should_test && no_run {
+            diag.err("the `--test` flag must be passed to enable `--no-run`");
+            return Err(1);
+        }
+
+        let out_dir = matches.opt_str("out-dir").map(|s| PathBuf::from(&s));
+        let output = matches.opt_str("output").map(|s| PathBuf::from(&s));
+        let output = match (out_dir, output) {
+            (Some(_), Some(_)) => {
+                diag.struct_err("cannot use both 'out-dir' and 'output' at once").emit();
+                return Err(1);
+            }
+            (Some(out_dir), None) => out_dir,
+            (None, Some(output)) => output,
+            (None, None) => PathBuf::from("doc"),
+        };
+
+        let cfgs = matches.opt_strs("cfg");
+        let check_cfgs = matches.opt_strs("check-cfg");
+
+        let extension_css = matches.opt_str("e").map(|s| PathBuf::from(&s));
+
+        if let Some(ref p) = extension_css {
+            if !p.is_file() {
+                diag.struct_err("option --extend-css argument must be a file").emit();
+                return Err(1);
+            }
+        }
+
+        let mut themes = Vec::new();
+        if matches.opt_present("theme") {
+            let paths = theme::load_css_paths(static_files::themes::LIGHT.as_bytes());
+
+            for (theme_file, theme_s) in
+                matches.opt_strs("theme").iter().map(|s| (PathBuf::from(&s), s.to_owned()))
+            {
+                if !theme_file.is_file() {
+                    diag.struct_err(&format!("invalid argument: \"{}\"", theme_s))
+                        .help("arguments to --theme must be files")
+                        .emit();
+                    return Err(1);
+                }
+                if theme_file.extension() != Some(OsStr::new("css")) {
+                    diag.struct_err(&format!("invalid argument: \"{}\"", theme_s))
+                        .help("arguments to --theme must have a .css extension")
+                        .emit();
+                    return Err(1);
+                }
+                let (success, ret) = theme::test_theme_against(&theme_file, &paths, &diag);
+                if !success {
+                    diag.struct_err(&format!("error loading theme file: \"{}\"", theme_s)).emit();
+                    return Err(1);
+                } else if !ret.is_empty() {
+                    diag.struct_warn(&format!(
+                        "theme file \"{}\" is missing CSS rules from the default theme",
+                        theme_s
+                    ))
+                    .warn("the theme may appear incorrect when loaded")
+                    .help(&format!(
+                        "to see what rules are missing, call `rustdoc --check-theme \"{}\"`",
+                        theme_s
+                    ))
+                    .emit();
+                }
+                themes.push(StylePath { path: theme_file });
+            }
+        }
+
+        let edition = config::parse_crate_edition(matches);
+
+        let mut id_map = html::markdown::IdMap::new();
+        let Some(external_html) = ExternalHtml::load(
+            &matches.opt_strs("html-in-header"),
+            &matches.opt_strs("html-before-content"),
+            &matches.opt_strs("html-after-content"),
+            &matches.opt_strs("markdown-before-content"),
+            &matches.opt_strs("markdown-after-content"),
+            nightly_options::match_is_nightly_build(matches),
+            &diag,
+            &mut id_map,
+            edition,
+            &None,
+        ) else {
+            return Err(3);
+        };
+
+        match matches.opt_str("r").as_deref() {
+            Some("rust") | None => {}
+            Some(s) => {
+                diag.struct_err(&format!("unknown input format: {}", s)).emit();
+                return Err(1);
+            }
+        }
+
+        let index_page = matches.opt_str("index-page").map(|s| PathBuf::from(&s));
+        if let Some(ref index_page) = index_page {
+            if !index_page.is_file() {
+                diag.struct_err("option `--index-page` argument must be a file").emit();
+                return Err(1);
+            }
+        }
+
+        let target = parse_target_triple(matches, error_format);
+
+        let show_coverage = matches.opt_present("show-coverage");
+
+        let crate_types = match parse_crate_types_from_list(matches.opt_strs("crate-type")) {
+            Ok(types) => types,
+            Err(e) => {
+                diag.struct_err(&format!("unknown crate type: {}", e)).emit();
+                return Err(1);
+            }
+        };
+
+        let output_format = match matches.opt_str("output-format") {
+            Some(s) => match OutputFormat::try_from(s.as_str()) {
+                Ok(out_fmt) => {
+                    if !out_fmt.is_json() && show_coverage {
+                        diag.struct_err(
+                            "html output format isn't supported for the --show-coverage option",
+                        )
+                        .emit();
+                        return Err(1);
+                    }
+                    out_fmt
+                }
+                Err(e) => {
+                    diag.struct_err(&e).emit();
+                    return Err(1);
+                }
+            },
+            None => OutputFormat::default(),
+        };
+        let crate_name = matches.opt_str("crate-name");
+        let proc_macro_crate = crate_types.contains(&CrateType::ProcMacro);
+        let playground_url = matches.opt_str("playground-url");
+        let maybe_sysroot = matches.opt_str("sysroot").map(PathBuf::from);
+        let module_sorting = if matches.opt_present("sort-modules-by-appearance") {
+            ModuleSorting::DeclarationOrder
+        } else {
+            ModuleSorting::Alphabetical
+        };
+        let resource_suffix = matches.opt_str("resource-suffix").unwrap_or_default();
+        let enable_minification = !matches.opt_present("disable-minification");
+        let markdown_no_toc = matches.opt_present("markdown-no-toc");
+        let markdown_css = matches.opt_strs("markdown-css");
+        let markdown_playground_url = matches.opt_str("markdown-playground-url");
+        let crate_version = matches.opt_str("crate-version");
+        let enable_index_page = matches.opt_present("enable-index-page") || index_page.is_some();
+        let static_root_path = matches.opt_str("static-root-path");
+        let test_run_directory = matches.opt_str("test-run-directory").map(PathBuf::from);
+        let persist_doctests = matches.opt_str("persist-doctests").map(PathBuf::from);
+        let test_builder = matches.opt_str("test-builder").map(PathBuf::from);
+        let codegen_options_strs = matches.opt_strs("C");
+        let unstable_opts_strs = matches.opt_strs("Z");
+        let lib_strs = matches.opt_strs("L");
+        let extern_strs = matches.opt_strs("extern");
+        let runtool = matches.opt_str("runtool");
+        let runtool_args = matches.opt_strs("runtool-arg");
+        let enable_per_target_ignores = matches.opt_present("enable-per-target-ignores");
+        let document_private = matches.opt_present("document-private-items");
+        let document_hidden = matches.opt_present("document-hidden-items");
+        let run_check = matches.opt_present("check");
+        let generate_redirect_map = matches.opt_present("generate-redirect-map");
+        let show_type_layout = matches.opt_present("show-type-layout");
+        let nocapture = matches.opt_present("nocapture");
+        let generate_link_to_definition = matches.opt_present("generate-link-to-definition");
+        let extern_html_root_takes_precedence =
+            matches.opt_present("extern-html-root-takes-precedence");
+
+        if generate_link_to_definition && (show_coverage || output_format != OutputFormat::Html) {
+            diag.struct_err(
+                "--generate-link-to-definition option can only be used with HTML output format",
+            )
+            .emit();
+            return Err(1);
+        }
+
+        let scrape_examples_options = ScrapeExamplesOptions::new(matches, &diag)?;
+        let with_examples = matches.opt_strs("with-examples");
+        let call_locations = crate::scrape_examples::load_call_locations(with_examples, &diag)?;
+
+        Ok(Options {
+            input,
+            proc_macro_crate,
+            error_format,
+            diagnostic_width,
+            libs,
+            lib_strs,
+            externs,
+            extern_strs,
+            cfgs,
+            check_cfgs,
+            codegen_options,
+            codegen_options_strs,
+            unstable_opts,
+            unstable_opts_strs,
+            target,
+            edition,
+            maybe_sysroot,
+            lint_opts,
+            describe_lints,
+            lint_cap,
+            should_test,
+            test_args,
+            show_coverage,
+            crate_version,
+            test_run_directory,
+            persist_doctests,
+            runtool,
+            runtool_args,
+            enable_per_target_ignores,
+            test_builder,
+            run_check,
+            no_run,
+            nocapture,
+            render_options: RenderOptions {
+                output,
+                external_html,
+                id_map,
+                playground_url,
+                module_sorting,
+                themes,
+                extension_css,
+                extern_html_root_urls,
+                extern_html_root_takes_precedence,
+                default_settings,
+                resource_suffix,
+                enable_minification,
+                enable_index_page,
+                index_page,
+                static_root_path,
+                markdown_no_toc,
+                markdown_css,
+                markdown_playground_url,
+                document_private,
+                document_hidden,
+                generate_redirect_map,
+                show_type_layout,
+                unstable_features: rustc_feature::UnstableFeatures::from_environment(
+                    crate_name.as_deref(),
+                ),
+                emit,
+                generate_link_to_definition,
+                call_locations,
+                no_emit_shared: false,
+            },
+            crate_name,
+            output_format,
+            json_unused_externs,
+            scrape_examples_options,
+        })
+    }
+
+    /// Returns `true` if the file given as `self.input` is a Markdown file.
+    pub(crate) fn markdown_input(&self) -> bool {
+        self.input.extension().map_or(false, |e| e == "md" || e == "markdown")
+    }
+}
+
+/// Prints deprecation warnings for deprecated options
+fn check_deprecated_options(matches: &getopts::Matches, diag: &rustc_errors::Handler) {
+    let deprecated_flags = [];
+
+    for &flag in deprecated_flags.iter() {
+        if matches.opt_present(flag) {
+            diag.struct_warn(&format!("the `{}` flag is deprecated", flag))
+                .note(
+                    "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                    for more information",
+                )
+                .emit();
+        }
+    }
+
+    let removed_flags = ["plugins", "plugin-path", "no-defaults", "passes", "input-format"];
+
+    for &flag in removed_flags.iter() {
+        if matches.opt_present(flag) {
+            let mut err = diag.struct_warn(&format!("the `{}` flag no longer functions", flag));
+            err.note(
+                "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+            );
+
+            if flag == "no-defaults" || flag == "passes" {
+                err.help("you may want to use --document-private-items");
+            } else if flag == "plugins" || flag == "plugin-path" {
+                err.warn("see CVE-2018-1000622");
+            }
+
+            err.emit();
+        }
+    }
+}
+
+/// Extracts `--extern-html-root-url` arguments from `matches` and returns a map of crate names to
+/// the given URLs. If an `--extern-html-root-url` argument was ill-formed, returns an error
+/// describing the issue.
+fn parse_extern_html_roots(
+    matches: &getopts::Matches,
+) -> Result<BTreeMap<String, String>, &'static str> {
+    let mut externs = BTreeMap::new();
+    for arg in &matches.opt_strs("extern-html-root-url") {
+        let (name, url) =
+            arg.split_once('=').ok_or("--extern-html-root-url must be of the form name=url")?;
+        externs.insert(name.to_string(), url.to_string());
+    }
+    Ok(externs)
+}
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
new file mode 100644
index 000000000..c48b25aea
--- /dev/null
+++ b/src/librustdoc/core.rs
@@ -0,0 +1,566 @@
+use rustc_ast::NodeId;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::sync::{self, Lrc};
+use rustc_errors::emitter::{Emitter, EmitterWriter};
+use rustc_errors::json::JsonEmitter;
+use rustc_feature::UnstableFeatures;
+use rustc_hir::def::{Namespace, Res};
+use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
+use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::{HirId, Path, TraitCandidate};
+use rustc_interface::interface;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::middle::privacy::AccessLevels;
+use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
+use rustc_resolve as resolve;
+use rustc_session::config::{self, CrateType, ErrorOutputType};
+use rustc_session::lint;
+use rustc_session::DiagnosticOutput;
+use rustc_session::Session;
+use rustc_span::symbol::sym;
+use rustc_span::{source_map, Span, Symbol};
+
+use std::cell::RefCell;
+use std::mem;
+use std::rc::Rc;
+use std::sync::LazyLock;
+
+use crate::clean::inline::build_external_trait;
+use crate::clean::{self, ItemId, TraitWithExtraInfo};
+use crate::config::{Options as RustdocOptions, OutputFormat, RenderOptions};
+use crate::formats::cache::Cache;
+use crate::passes::collect_intra_doc_links::PreprocessedMarkdownLink;
+use crate::passes::{self, Condition::*};
+
+pub(crate) use rustc_session::config::{Input, Options, UnstableOptions};
+
+pub(crate) struct ResolverCaches {
+    pub(crate) markdown_links: Option<FxHashMap<String, Vec<PreprocessedMarkdownLink>>>,
+    pub(crate) doc_link_resolutions: FxHashMap<(Symbol, Namespace, DefId), Option<Res<NodeId>>>,
+    /// Traits in scope for a given module.
+    /// See `collect_intra_doc_links::traits_implemented_by` for more details.
+    pub(crate) traits_in_scope: DefIdMap<Vec<TraitCandidate>>,
+    pub(crate) all_traits: Option<Vec<DefId>>,
+    pub(crate) all_trait_impls: Option<Vec<DefId>>,
+    pub(crate) all_macro_rules: FxHashMap<Symbol, Res<NodeId>>,
+}
+
+pub(crate) struct DocContext<'tcx> {
+    pub(crate) tcx: TyCtxt<'tcx>,
+    /// Name resolver. Used for intra-doc links.
+    ///
+    /// The `Rc<RefCell<...>>` wrapping is needed because that is what's returned by
+    /// [`rustc_interface::Queries::expansion()`].
+    // FIXME: see if we can get rid of this RefCell somehow
+    pub(crate) resolver: Rc<RefCell<interface::BoxedResolver>>,
+    pub(crate) resolver_caches: ResolverCaches,
+    /// Used for normalization.
+    ///
+    /// Most of this logic is copied from rustc_lint::late.
+    pub(crate) param_env: ParamEnv<'tcx>,
+    /// Later on moved through `clean::Crate` into `cache`
+    pub(crate) external_traits: Rc<RefCell<FxHashMap<DefId, clean::TraitWithExtraInfo>>>,
+    /// Used while populating `external_traits` to ensure we don't process the same trait twice at
+    /// the same time.
+    pub(crate) active_extern_traits: FxHashSet<DefId>,
+    // The current set of parameter substitutions,
+    // for expanding type aliases at the HIR level:
+    /// Table `DefId` of type, lifetime, or const parameter -> substituted type, lifetime, or const
+    pub(crate) substs: FxHashMap<DefId, clean::SubstParam>,
+    /// Table synthetic type parameter for `impl Trait` in argument position -> bounds
+    pub(crate) impl_trait_bounds: FxHashMap<ImplTraitParam, Vec<clean::GenericBound>>,
+    /// Auto-trait or blanket impls processed so far, as `(self_ty, trait_def_id)`.
+    // FIXME(eddyb) make this a `ty::TraitRef<'tcx>` set.
+    pub(crate) generated_synthetics: FxHashSet<(Ty<'tcx>, DefId)>,
+    pub(crate) auto_traits: Vec<DefId>,
+    /// The options given to rustdoc that could be relevant to a pass.
+    pub(crate) render_options: RenderOptions,
+    /// This same cache is used throughout rustdoc, including in [`crate::html::render`].
+    pub(crate) cache: Cache,
+    /// Used by [`clean::inline`] to tell if an item has already been inlined.
+    pub(crate) inlined: FxHashSet<ItemId>,
+    /// Used by `calculate_doc_coverage`.
+    pub(crate) output_format: OutputFormat,
+    /// Used by `strip_private`.
+    pub(crate) show_coverage: bool,
+}
+
+impl<'tcx> DocContext<'tcx> {
+    pub(crate) fn sess(&self) -> &'tcx Session {
+        self.tcx.sess
+    }
+
+    pub(crate) fn with_param_env<T, F: FnOnce(&mut Self) -> T>(
+        &mut self,
+        def_id: DefId,
+        f: F,
+    ) -> T {
+        let old_param_env = mem::replace(&mut self.param_env, self.tcx.param_env(def_id));
+        let ret = f(self);
+        self.param_env = old_param_env;
+        ret
+    }
+
+    pub(crate) fn enter_resolver<F, R>(&self, f: F) -> R
+    where
+        F: FnOnce(&mut resolve::Resolver<'_>) -> R,
+    {
+        self.resolver.borrow_mut().access(f)
+    }
+
+    /// Call the closure with the given parameters set as
+    /// the substitutions for a type alias' RHS.
+    pub(crate) fn enter_alias<F, R>(
+        &mut self,
+        substs: FxHashMap<DefId, clean::SubstParam>,
+        f: F,
+    ) -> R
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        let old_substs = mem::replace(&mut self.substs, substs);
+        let r = f(self);
+        self.substs = old_substs;
+        r
+    }
+
+    /// Like `hir().local_def_id_to_hir_id()`, but skips calling it on fake DefIds.
+    /// (This avoids a slice-index-out-of-bounds panic.)
+    pub(crate) fn as_local_hir_id(tcx: TyCtxt<'_>, item_id: ItemId) -> Option<HirId> {
+        match item_id {
+            ItemId::DefId(real_id) => {
+                real_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
+            }
+            // FIXME: Can this be `Some` for `Auto` or `Blanket`?
+            _ => None,
+        }
+    }
+
+    pub(crate) fn with_all_traits(&mut self, f: impl FnOnce(&mut Self, &[DefId])) {
+        let all_traits = self.resolver_caches.all_traits.take();
+        f(self, all_traits.as_ref().expect("`all_traits` are already borrowed"));
+        self.resolver_caches.all_traits = all_traits;
+    }
+
+    pub(crate) fn with_all_trait_impls(&mut self, f: impl FnOnce(&mut Self, &[DefId])) {
+        let all_trait_impls = self.resolver_caches.all_trait_impls.take();
+        f(self, all_trait_impls.as_ref().expect("`all_trait_impls` are already borrowed"));
+        self.resolver_caches.all_trait_impls = all_trait_impls;
+    }
+}
+
+/// Creates a new diagnostic `Handler` that can be used to emit warnings and errors.
+///
+/// If the given `error_format` is `ErrorOutputType::Json` and no `SourceMap` is given, a new one
+/// will be created for the handler.
+pub(crate) fn new_handler(
+    error_format: ErrorOutputType,
+    source_map: Option<Lrc<source_map::SourceMap>>,
+    diagnostic_width: Option<usize>,
+    unstable_opts: &UnstableOptions,
+) -> rustc_errors::Handler {
+    let fallback_bundle =
+        rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+    let emitter: Box<dyn Emitter + sync::Send> = match error_format {
+        ErrorOutputType::HumanReadable(kind) => {
+            let (short, color_config) = kind.unzip();
+            Box::new(
+                EmitterWriter::stderr(
+                    color_config,
+                    source_map.map(|sm| sm as _),
+                    None,
+                    fallback_bundle,
+                    short,
+                    unstable_opts.teach,
+                    diagnostic_width,
+                    false,
+                )
+                .ui_testing(unstable_opts.ui_testing),
+            )
+        }
+        ErrorOutputType::Json { pretty, json_rendered } => {
+            let source_map = source_map.unwrap_or_else(|| {
+                Lrc::new(source_map::SourceMap::new(source_map::FilePathMapping::empty()))
+            });
+            Box::new(
+                JsonEmitter::stderr(
+                    None,
+                    source_map,
+                    None,
+                    fallback_bundle,
+                    pretty,
+                    json_rendered,
+                    diagnostic_width,
+                    false,
+                )
+                .ui_testing(unstable_opts.ui_testing),
+            )
+        }
+    };
+
+    rustc_errors::Handler::with_emitter_and_flags(
+        emitter,
+        unstable_opts.diagnostic_handler_flags(true),
+    )
+}
+
+/// Parse, resolve, and typecheck the given crate.
+pub(crate) fn create_config(
+    RustdocOptions {
+        input,
+        crate_name,
+        proc_macro_crate,
+        error_format,
+        diagnostic_width,
+        libs,
+        externs,
+        mut cfgs,
+        check_cfgs,
+        codegen_options,
+        unstable_opts,
+        target,
+        edition,
+        maybe_sysroot,
+        lint_opts,
+        describe_lints,
+        lint_cap,
+        scrape_examples_options,
+        ..
+    }: RustdocOptions,
+) -> rustc_interface::Config {
+    // Add the doc cfg into the doc build.
+    cfgs.push("doc".to_string());
+
+    let cpath = Some(input.clone());
+    let input = Input::File(input);
+
+    // By default, rustdoc ignores all lints.
+    // Specifically unblock lints relevant to documentation or the lint machinery itself.
+    let mut lints_to_show = vec![
+        // it's unclear whether these should be part of rustdoc directly (#77364)
+        rustc_lint::builtin::MISSING_DOCS.name.to_string(),
+        rustc_lint::builtin::INVALID_DOC_ATTRIBUTES.name.to_string(),
+        // these are definitely not part of rustdoc, but we want to warn on them anyway.
+        rustc_lint::builtin::RENAMED_AND_REMOVED_LINTS.name.to_string(),
+        rustc_lint::builtin::UNKNOWN_LINTS.name.to_string(),
+        rustc_lint::builtin::UNEXPECTED_CFGS.name.to_string(),
+        // this lint is needed to support `#[expect]` attributes
+        rustc_lint::builtin::UNFULFILLED_LINT_EXPECTATIONS.name.to_string(),
+    ];
+    lints_to_show.extend(crate::lint::RUSTDOC_LINTS.iter().map(|lint| lint.name.to_string()));
+
+    let (lint_opts, lint_caps) = crate::lint::init_lints(lints_to_show, lint_opts, |lint| {
+        Some((lint.name_lower(), lint::Allow))
+    });
+
+    let crate_types =
+        if proc_macro_crate { vec![CrateType::ProcMacro] } else { vec![CrateType::Rlib] };
+    let test = scrape_examples_options.map(|opts| opts.scrape_tests).unwrap_or(false);
+    // plays with error output here!
+    let sessopts = config::Options {
+        maybe_sysroot,
+        search_paths: libs,
+        crate_types,
+        lint_opts,
+        lint_cap,
+        cg: codegen_options,
+        externs,
+        target_triple: target,
+        unstable_features: UnstableFeatures::from_environment(crate_name.as_deref()),
+        actually_rustdoc: true,
+        unstable_opts,
+        error_format,
+        diagnostic_width,
+        edition,
+        describe_lints,
+        crate_name,
+        test,
+        ..Options::default()
+    };
+
+    interface::Config {
+        opts: sessopts,
+        crate_cfg: interface::parse_cfgspecs(cfgs),
+        crate_check_cfg: interface::parse_check_cfg(check_cfgs),
+        input,
+        input_path: cpath,
+        output_file: None,
+        output_dir: None,
+        file_loader: None,
+        diagnostic_output: DiagnosticOutput::Default,
+        lint_caps,
+        parse_sess_created: None,
+        register_lints: Some(Box::new(crate::lint::register_lints)),
+        override_queries: Some(|_sess, providers, _external_providers| {
+            // Most lints will require typechecking, so just don't run them.
+            providers.lint_mod = |_, _| {};
+            // Prevent `rustc_typeck::check_crate` from calling `typeck` on all bodies.
+            providers.typeck_item_bodies = |_, _| {};
+            // hack so that `used_trait_imports` won't try to call typeck
+            providers.used_trait_imports = |_, _| {
+                static EMPTY_SET: LazyLock<FxHashSet<LocalDefId>> =
+                    LazyLock::new(FxHashSet::default);
+                &EMPTY_SET
+            };
+            // In case typeck does end up being called, don't ICE in case there were name resolution errors
+            providers.typeck = move |tcx, def_id| {
+                // Closures' tables come from their outermost function,
+                // as they are part of the same "inference environment".
+                // This avoids emitting errors for the parent twice (see similar code in `typeck_with_fallback`)
+                let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
+                if typeck_root_def_id != def_id {
+                    return tcx.typeck(typeck_root_def_id);
+                }
+
+                let hir = tcx.hir();
+                let body = hir.body(hir.body_owned_by(def_id));
+                debug!("visiting body for {:?}", def_id);
+                EmitIgnoredResolutionErrors::new(tcx).visit_body(body);
+                (rustc_interface::DEFAULT_QUERY_PROVIDERS.typeck)(tcx, def_id)
+            };
+        }),
+        make_codegen_backend: None,
+        registry: rustc_driver::diagnostics_registry(),
+    }
+}
+
+pub(crate) fn run_global_ctxt(
+    tcx: TyCtxt<'_>,
+    resolver: Rc<RefCell<interface::BoxedResolver>>,
+    resolver_caches: ResolverCaches,
+    show_coverage: bool,
+    render_options: RenderOptions,
+    output_format: OutputFormat,
+) -> (clean::Crate, RenderOptions, Cache) {
+    // Certain queries assume that some checks were run elsewhere
+    // (see https://github.com/rust-lang/rust/pull/73566#issuecomment-656954425),
+    // so type-check everything other than function bodies in this crate before running lints.
+
+    // NOTE: this does not call `tcx.analysis()` so that we won't
+    // typeck function bodies or run the default rustc lints.
+    // (see `override_queries` in the `config`)
+
+    // HACK(jynelson) this calls an _extremely_ limited subset of `typeck`
+    // and might break if queries change their assumptions in the future.
+
+    // NOTE: This is copy/pasted from typeck/lib.rs and should be kept in sync with those changes.
+    tcx.sess.time("item_types_checking", || {
+        tcx.hir().for_each_module(|module| tcx.ensure().check_mod_item_types(module))
+    });
+    tcx.sess.abort_if_errors();
+    tcx.sess.time("missing_docs", || {
+        rustc_lint::check_crate(tcx, rustc_lint::builtin::MissingDoc::new);
+    });
+    tcx.sess.time("check_mod_attrs", || {
+        tcx.hir().for_each_module(|module| tcx.ensure().check_mod_attrs(module))
+    });
+    rustc_passes::stability::check_unused_or_stable_features(tcx);
+
+    let auto_traits = resolver_caches
+        .all_traits
+        .as_ref()
+        .expect("`all_traits` are already borrowed")
+        .iter()
+        .copied()
+        .filter(|&trait_def_id| tcx.trait_is_auto(trait_def_id))
+        .collect();
+    let access_levels = AccessLevels {
+        map: tcx.privacy_access_levels(()).map.iter().map(|(k, v)| (k.to_def_id(), *v)).collect(),
+    };
+
+    let mut ctxt = DocContext {
+        tcx,
+        resolver,
+        resolver_caches,
+        param_env: ParamEnv::empty(),
+        external_traits: Default::default(),
+        active_extern_traits: Default::default(),
+        substs: Default::default(),
+        impl_trait_bounds: Default::default(),
+        generated_synthetics: Default::default(),
+        auto_traits,
+        cache: Cache::new(access_levels, render_options.document_private),
+        inlined: FxHashSet::default(),
+        output_format,
+        render_options,
+        show_coverage,
+    };
+
+    // Small hack to force the Sized trait to be present.
+    //
+    // Note that in case of `#![no_core]`, the trait is not available.
+    if let Some(sized_trait_did) = ctxt.tcx.lang_items().sized_trait() {
+        let sized_trait = build_external_trait(&mut ctxt, sized_trait_did);
+        ctxt.external_traits
+            .borrow_mut()
+            .insert(sized_trait_did, TraitWithExtraInfo { trait_: sized_trait, is_notable: false });
+    }
+
+    debug!("crate: {:?}", tcx.hir().krate());
+
+    let mut krate = tcx.sess.time("clean_crate", || clean::krate(&mut ctxt));
+
+    if krate.module.doc_value().map(|d| d.is_empty()).unwrap_or(true) {
+        let help = format!(
+            "The following guide may be of use:\n\
+            {}/rustdoc/how-to-write-documentation.html",
+            crate::DOC_RUST_LANG_ORG_CHANNEL
+        );
+        tcx.struct_lint_node(
+            crate::lint::MISSING_CRATE_LEVEL_DOCS,
+            DocContext::as_local_hir_id(tcx, krate.module.item_id).unwrap(),
+            |lint| {
+                let mut diag =
+                    lint.build("no documentation found for this crate's top-level module");
+                diag.help(&help);
+                diag.emit();
+            },
+        );
+    }
+
+    fn report_deprecated_attr(name: &str, diag: &rustc_errors::Handler, sp: Span) {
+        let mut msg =
+            diag.struct_span_warn(sp, &format!("the `#![doc({})]` attribute is deprecated", name));
+        msg.note(
+            "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+            for more information",
+        );
+
+        if name == "no_default_passes" {
+            msg.help("`#![doc(no_default_passes)]` no longer functions; you may want to use `#![doc(document_private_items)]`");
+        } else if name.starts_with("passes") {
+            msg.help("`#![doc(passes = \"...\")]` no longer functions; you may want to use `#![doc(document_private_items)]`");
+        } else if name.starts_with("plugins") {
+            msg.warn("`#![doc(plugins = \"...\")]` no longer functions; see CVE-2018-1000622 <https://nvd.nist.gov/vuln/detail/CVE-2018-1000622>");
+        }
+
+        msg.emit();
+    }
+
+    // Process all of the crate attributes, extracting plugin metadata along
+    // with the passes which we are supposed to run.
+    for attr in krate.module.attrs.lists(sym::doc) {
+        let diag = ctxt.sess().diagnostic();
+
+        let name = attr.name_or_empty();
+        // `plugins = "..."`, `no_default_passes`, and `passes = "..."` have no effect
+        if attr.is_word() && name == sym::no_default_passes {
+            report_deprecated_attr("no_default_passes", diag, attr.span());
+        } else if attr.value_str().is_some() {
+            match name {
+                sym::passes => {
+                    report_deprecated_attr("passes = \"...\"", diag, attr.span());
+                }
+                sym::plugins => {
+                    report_deprecated_attr("plugins = \"...\"", diag, attr.span());
+                }
+                _ => (),
+            }
+        }
+
+        if attr.is_word() && name == sym::document_private_items {
+            ctxt.render_options.document_private = true;
+        }
+    }
+
+    info!("Executing passes");
+
+    for p in passes::defaults(show_coverage) {
+        let run = match p.condition {
+            Always => true,
+            WhenDocumentPrivate => ctxt.render_options.document_private,
+            WhenNotDocumentPrivate => !ctxt.render_options.document_private,
+            WhenNotDocumentHidden => !ctxt.render_options.document_hidden,
+        };
+        if run {
+            debug!("running pass {}", p.pass.name);
+            krate = tcx.sess.time(p.pass.name, || (p.pass.run)(krate, &mut ctxt));
+        }
+    }
+
+    tcx.sess.time("check_lint_expectations", || tcx.check_expectations(Some(sym::rustdoc)));
+
+    if tcx.sess.diagnostic().has_errors_or_lint_errors().is_some() {
+        rustc_errors::FatalError.raise();
+    }
+
+    krate = tcx.sess.time("create_format_cache", || Cache::populate(&mut ctxt, krate));
+
+    (krate, ctxt.render_options, ctxt.cache)
+}
+
+/// Due to <https://github.com/rust-lang/rust/pull/73566>,
+/// the name resolution pass may find errors that are never emitted.
+/// If typeck is called after this happens, then we'll get an ICE:
+/// 'Res::Error found but not reported'. To avoid this, emit the errors now.
+struct EmitIgnoredResolutionErrors<'tcx> {
+    tcx: TyCtxt<'tcx>,
+}
+
+impl<'tcx> EmitIgnoredResolutionErrors<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>) -> Self {
+        Self { tcx }
+    }
+}
+
+impl<'tcx> Visitor<'tcx> for EmitIgnoredResolutionErrors<'tcx> {
+    type NestedFilter = nested_filter::OnlyBodies;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        // We need to recurse into nested closures,
+        // since those will fallback to the parent for type checking.
+        self.tcx.hir()
+    }
+
+    fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
+        debug!("visiting path {:?}", path);
+        if path.res == Res::Err {
+            // We have less context here than in rustc_resolve,
+            // so we can only emit the name and span.
+            // However we can give a hint that rustc_resolve will have more info.
+            let label = format!(
+                "could not resolve path `{}`",
+                path.segments
+                    .iter()
+                    .map(|segment| segment.ident.as_str())
+                    .intersperse("::")
+                    .collect::<String>()
+            );
+            let mut err = rustc_errors::struct_span_err!(
+                self.tcx.sess,
+                path.span,
+                E0433,
+                "failed to resolve: {}",
+                label
+            );
+            err.span_label(path.span, label);
+            err.note("this error was originally ignored because you are running `rustdoc`");
+            err.note("try running again with `rustc` or `cargo check` and you may get a more detailed error");
+            err.emit();
+        }
+        // We could have an outer resolution that succeeded,
+        // but with generic parameters that failed.
+        // Recurse into the segments so we catch those too.
+        intravisit::walk_path(self, path);
+    }
+}
+
+/// `DefId` or parameter index (`ty::ParamTy.index`) of a synthetic type parameter
+/// for `impl Trait` in argument position.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub(crate) enum ImplTraitParam {
+    DefId(DefId),
+    ParamIndex(u32),
+}
+
+impl From<DefId> for ImplTraitParam {
+    fn from(did: DefId) -> Self {
+        ImplTraitParam::DefId(did)
+    }
+}
+
+impl From<u32> for ImplTraitParam {
+    fn from(idx: u32) -> Self {
+        ImplTraitParam::ParamIndex(idx)
+    }
+}
diff --git a/src/librustdoc/docfs.rs b/src/librustdoc/docfs.rs
new file mode 100644
index 000000000..be066bdaf
--- /dev/null
+++ b/src/librustdoc/docfs.rs
@@ -0,0 +1,78 @@
+//! Rustdoc's FileSystem abstraction module.
+//!
+//! On Windows this indirects IO into threads to work around performance issues
+//! with Defender (and other similar virus scanners that do blocking operations).
+//! On other platforms this is a thin shim to fs.
+//!
+//! Only calls needed to permit this workaround have been abstracted: thus
+//! fs::read is still done directly via the fs module; if in future rustdoc
+//! needs to read-after-write from a file, then it would be added to this
+//! abstraction.
+
+use std::fs;
+use std::io;
+use std::path::{Path, PathBuf};
+use std::string::ToString;
+use std::sync::mpsc::Sender;
+
+pub(crate) trait PathError {
+    fn new<S, P: AsRef<Path>>(e: S, path: P) -> Self
+    where
+        S: ToString + Sized;
+}
+
+pub(crate) struct DocFS {
+    sync_only: bool,
+    errors: Option<Sender<String>>,
+}
+
+impl DocFS {
+    pub(crate) fn new(errors: Sender<String>) -> DocFS {
+        DocFS { sync_only: false, errors: Some(errors) }
+    }
+
+    pub(crate) fn set_sync_only(&mut self, sync_only: bool) {
+        self.sync_only = sync_only;
+    }
+
+    pub(crate) fn close(&mut self) {
+        self.errors = None;
+    }
+
+    pub(crate) fn create_dir_all<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
+        // For now, dir creation isn't a huge time consideration, do it
+        // synchronously, which avoids needing ordering between write() actions
+        // and directory creation.
+        fs::create_dir_all(path)
+    }
+
+    pub(crate) fn write<E>(
+        &self,
+        path: PathBuf,
+        contents: impl 'static + Send + AsRef<[u8]>,
+    ) -> Result<(), E>
+    where
+        E: PathError,
+    {
+        #[cfg(windows)]
+        if !self.sync_only {
+            // A possible future enhancement after more detailed profiling would
+            // be to create the file sync so errors are reported eagerly.
+            let sender = self.errors.clone().expect("can't write after closing");
+            rayon::spawn(move || {
+                fs::write(&path, contents).unwrap_or_else(|e| {
+                    sender.send(format!("\"{}\": {}", path.display(), e)).unwrap_or_else(|_| {
+                        panic!("failed to send error on \"{}\"", path.display())
+                    })
+                });
+            });
+        } else {
+            fs::write(&path, contents).map_err(|e| E::new(e, path))?;
+        }
+
+        #[cfg(not(windows))]
+        fs::write(&path, contents).map_err(|e| E::new(e, path))?;
+
+        Ok(())
+    }
+}
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
new file mode 100644
index 000000000..35964e3ba
--- /dev/null
+++ b/src/librustdoc/doctest.rs
@@ -0,0 +1,1311 @@
+use rustc_ast as ast;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::sync::Lrc;
+use rustc_errors::{ColorConfig, ErrorGuaranteed, FatalError};
+use rustc_hir as hir;
+use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_hir::intravisit;
+use rustc_hir::{HirId, CRATE_HIR_ID};
+use rustc_interface::interface;
+use rustc_middle::hir::map::Map;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::TyCtxt;
+use rustc_parse::maybe_new_parser_from_source_str;
+use rustc_parse::parser::attr::InnerAttrPolicy;
+use rustc_session::config::{self, CrateType, ErrorOutputType};
+use rustc_session::parse::ParseSess;
+use rustc_session::{lint, DiagnosticOutput, Session};
+use rustc_span::edition::Edition;
+use rustc_span::source_map::SourceMap;
+use rustc_span::symbol::sym;
+use rustc_span::Symbol;
+use rustc_span::{BytePos, FileName, Pos, Span, DUMMY_SP};
+use rustc_target::spec::TargetTriple;
+use tempfile::Builder as TempFileBuilder;
+
+use std::env;
+use std::io::{self, Write};
+use std::panic;
+use std::path::PathBuf;
+use std::process::{self, Command, Stdio};
+use std::str;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex};
+
+use crate::clean::{types::AttributesExt, Attributes};
+use crate::config::Options as RustdocOptions;
+use crate::html::markdown::{self, ErrorCodes, Ignore, LangString};
+use crate::lint::init_lints;
+use crate::passes::span_of_attrs;
+
+/// Options that apply to all doctests in a crate or Markdown file (for `rustdoc foo.md`).
+#[derive(Clone, Default)]
+pub(crate) struct GlobalTestOptions {
+    /// Whether to disable the default `extern crate my_crate;` when creating doctests.
+    pub(crate) no_crate_inject: bool,
+    /// Additional crate-level attributes to add to doctests.
+    pub(crate) attrs: Vec<String>,
+}
+
+pub(crate) fn run(options: RustdocOptions) -> Result<(), ErrorGuaranteed> {
+    let input = config::Input::File(options.input.clone());
+
+    let invalid_codeblock_attributes_name = crate::lint::INVALID_CODEBLOCK_ATTRIBUTES.name;
+
+    // See core::create_config for what's going on here.
+    let allowed_lints = vec![
+        invalid_codeblock_attributes_name.to_owned(),
+        lint::builtin::UNKNOWN_LINTS.name.to_owned(),
+        lint::builtin::RENAMED_AND_REMOVED_LINTS.name.to_owned(),
+    ];
+
+    let (lint_opts, lint_caps) = init_lints(allowed_lints, options.lint_opts.clone(), |lint| {
+        if lint.name == invalid_codeblock_attributes_name {
+            None
+        } else {
+            Some((lint.name_lower(), lint::Allow))
+        }
+    });
+
+    debug!(?lint_opts);
+
+    let crate_types =
+        if options.proc_macro_crate { vec![CrateType::ProcMacro] } else { vec![CrateType::Rlib] };
+
+    let sessopts = config::Options {
+        maybe_sysroot: options.maybe_sysroot.clone(),
+        search_paths: options.libs.clone(),
+        crate_types,
+        lint_opts,
+        lint_cap: Some(options.lint_cap.unwrap_or(lint::Forbid)),
+        cg: options.codegen_options.clone(),
+        externs: options.externs.clone(),
+        unstable_features: options.render_options.unstable_features,
+        actually_rustdoc: true,
+        edition: options.edition,
+        target_triple: options.target.clone(),
+        crate_name: options.crate_name.clone(),
+        ..config::Options::default()
+    };
+
+    let mut cfgs = options.cfgs.clone();
+    cfgs.push("doc".to_owned());
+    cfgs.push("doctest".to_owned());
+    let config = interface::Config {
+        opts: sessopts,
+        crate_cfg: interface::parse_cfgspecs(cfgs),
+        crate_check_cfg: interface::parse_check_cfg(options.check_cfgs.clone()),
+        input,
+        input_path: None,
+        output_file: None,
+        output_dir: None,
+        file_loader: None,
+        diagnostic_output: DiagnosticOutput::Default,
+        lint_caps,
+        parse_sess_created: None,
+        register_lints: Some(Box::new(crate::lint::register_lints)),
+        override_queries: None,
+        make_codegen_backend: None,
+        registry: rustc_driver::diagnostics_registry(),
+    };
+
+    let test_args = options.test_args.clone();
+    let nocapture = options.nocapture;
+    let externs = options.externs.clone();
+    let json_unused_externs = options.json_unused_externs;
+
+    let (tests, unused_extern_reports, compiling_test_count) =
+        interface::run_compiler(config, |compiler| {
+            compiler.enter(|queries| {
+                let mut global_ctxt = queries.global_ctxt()?.take();
+
+                let collector = global_ctxt.enter(|tcx| {
+                    let crate_attrs = tcx.hir().attrs(CRATE_HIR_ID);
+
+                    let opts = scrape_test_config(crate_attrs);
+                    let enable_per_target_ignores = options.enable_per_target_ignores;
+                    let mut collector = Collector::new(
+                        tcx.crate_name(LOCAL_CRATE),
+                        options,
+                        false,
+                        opts,
+                        Some(compiler.session().parse_sess.clone_source_map()),
+                        None,
+                        enable_per_target_ignores,
+                    );
+
+                    let mut hir_collector = HirCollector {
+                        sess: compiler.session(),
+                        collector: &mut collector,
+                        map: tcx.hir(),
+                        codes: ErrorCodes::from(
+                            compiler.session().opts.unstable_features.is_nightly_build(),
+                        ),
+                        tcx,
+                    };
+                    hir_collector.visit_testable(
+                        "".to_string(),
+                        CRATE_HIR_ID,
+                        tcx.hir().span(CRATE_HIR_ID),
+                        |this| tcx.hir().walk_toplevel_module(this),
+                    );
+
+                    collector
+                });
+                if compiler.session().diagnostic().has_errors_or_lint_errors().is_some() {
+                    FatalError.raise();
+                }
+
+                let unused_extern_reports = collector.unused_extern_reports.clone();
+                let compiling_test_count = collector.compiling_test_count.load(Ordering::SeqCst);
+                let ret: Result<_, ErrorGuaranteed> =
+                    Ok((collector.tests, unused_extern_reports, compiling_test_count));
+                ret
+            })
+        })?;
+
+    run_tests(test_args, nocapture, tests);
+
+    // Collect and warn about unused externs, but only if we've gotten
+    // reports for each doctest
+    if json_unused_externs.is_enabled() {
+        let unused_extern_reports: Vec<_> =
+            std::mem::take(&mut unused_extern_reports.lock().unwrap());
+        if unused_extern_reports.len() == compiling_test_count {
+            let extern_names = externs.iter().map(|(name, _)| name).collect::<FxHashSet<&String>>();
+            let mut unused_extern_names = unused_extern_reports
+                .iter()
+                .map(|uexts| uexts.unused_extern_names.iter().collect::<FxHashSet<&String>>())
+                .fold(extern_names, |uextsa, uextsb| {
+                    uextsa.intersection(&uextsb).copied().collect::<FxHashSet<&String>>()
+                })
+                .iter()
+                .map(|v| (*v).clone())
+                .collect::<Vec<String>>();
+            unused_extern_names.sort();
+            // Take the most severe lint level
+            let lint_level = unused_extern_reports
+                .iter()
+                .map(|uexts| uexts.lint_level.as_str())
+                .max_by_key(|v| match *v {
+                    "warn" => 1,
+                    "deny" => 2,
+                    "forbid" => 3,
+                    // The allow lint level is not expected,
+                    // as if allow is specified, no message
+                    // is to be emitted.
+                    v => unreachable!("Invalid lint level '{}'", v),
+                })
+                .unwrap_or("warn")
+                .to_string();
+            let uext = UnusedExterns { lint_level, unused_extern_names };
+            let unused_extern_json = serde_json::to_string(&uext).unwrap();
+            eprintln!("{unused_extern_json}");
+        }
+    }
+
+    Ok(())
+}
+
+pub(crate) fn run_tests(
+    mut test_args: Vec<String>,
+    nocapture: bool,
+    tests: Vec<test::TestDescAndFn>,
+) {
+    test_args.insert(0, "rustdoctest".to_string());
+    if nocapture {
+        test_args.push("--nocapture".to_string());
+    }
+    test::test_main(&test_args, tests, None);
+}
+
+// Look for `#![doc(test(no_crate_inject))]`, used by crates in the std facade.
+fn scrape_test_config(attrs: &[ast::Attribute]) -> GlobalTestOptions {
+    use rustc_ast_pretty::pprust;
+
+    let mut opts = GlobalTestOptions { no_crate_inject: false, attrs: Vec::new() };
+
+    let test_attrs: Vec<_> = attrs
+        .iter()
+        .filter(|a| a.has_name(sym::doc))
+        .flat_map(|a| a.meta_item_list().unwrap_or_default())
+        .filter(|a| a.has_name(sym::test))
+        .collect();
+    let attrs = test_attrs.iter().flat_map(|a| a.meta_item_list().unwrap_or(&[]));
+
+    for attr in attrs {
+        if attr.has_name(sym::no_crate_inject) {
+            opts.no_crate_inject = true;
+        }
+        if attr.has_name(sym::attr) {
+            if let Some(l) = attr.meta_item_list() {
+                for item in l {
+                    opts.attrs.push(pprust::meta_list_item_to_string(item));
+                }
+            }
+        }
+    }
+
+    opts
+}
+
+/// Documentation test failure modes.
+enum TestFailure {
+    /// The test failed to compile.
+    CompileError,
+    /// The test is marked `compile_fail` but compiled successfully.
+    UnexpectedCompilePass,
+    /// The test failed to compile (as expected) but the compiler output did not contain all
+    /// expected error codes.
+    MissingErrorCodes(Vec<String>),
+    /// The test binary was unable to be executed.
+    ExecutionError(io::Error),
+    /// The test binary exited with a non-zero exit code.
+    ///
+    /// This typically means an assertion in the test failed or another form of panic occurred.
+    ExecutionFailure(process::Output),
+    /// The test is marked `should_panic` but the test binary executed successfully.
+    UnexpectedRunPass,
+}
+
+enum DirState {
+    Temp(tempfile::TempDir),
+    Perm(PathBuf),
+}
+
+impl DirState {
+    fn path(&self) -> &std::path::Path {
+        match self {
+            DirState::Temp(t) => t.path(),
+            DirState::Perm(p) => p.as_path(),
+        }
+    }
+}
+
+// NOTE: Keep this in sync with the equivalent structs in rustc
+// and cargo.
+// We could unify this struct the one in rustc but they have different
+// ownership semantics, so doing so would create wasteful allocations.
+#[derive(serde::Serialize, serde::Deserialize)]
+struct UnusedExterns {
+    /// Lint level of the unused_crate_dependencies lint
+    lint_level: String,
+    /// List of unused externs by their names.
+    unused_extern_names: Vec<String>,
+}
+
+fn run_test(
+    test: &str,
+    crate_name: &str,
+    line: usize,
+    rustdoc_options: RustdocOptions,
+    mut lang_string: LangString,
+    no_run: bool,
+    runtool: Option<String>,
+    runtool_args: Vec<String>,
+    target: TargetTriple,
+    opts: &GlobalTestOptions,
+    edition: Edition,
+    outdir: DirState,
+    path: PathBuf,
+    test_id: &str,
+    report_unused_externs: impl Fn(UnusedExterns),
+) -> Result<(), TestFailure> {
+    let (test, line_offset, supports_color) =
+        make_test(test, Some(crate_name), lang_string.test_harness, opts, edition, Some(test_id));
+
+    let output_file = outdir.path().join("rust_out");
+
+    let rustc_binary = rustdoc_options
+        .test_builder
+        .as_deref()
+        .unwrap_or_else(|| rustc_interface::util::rustc_path().expect("found rustc"));
+    let mut compiler = Command::new(&rustc_binary);
+    compiler.arg("--crate-type").arg("bin");
+    for cfg in &rustdoc_options.cfgs {
+        compiler.arg("--cfg").arg(&cfg);
+    }
+    if !rustdoc_options.check_cfgs.is_empty() {
+        compiler.arg("-Z").arg("unstable-options");
+        for check_cfg in &rustdoc_options.check_cfgs {
+            compiler.arg("--check-cfg").arg(&check_cfg);
+        }
+    }
+    if let Some(sysroot) = rustdoc_options.maybe_sysroot {
+        compiler.arg("--sysroot").arg(sysroot);
+    }
+    compiler.arg("--edition").arg(&edition.to_string());
+    compiler.env("UNSTABLE_RUSTDOC_TEST_PATH", path);
+    compiler.env("UNSTABLE_RUSTDOC_TEST_LINE", format!("{}", line as isize - line_offset as isize));
+    compiler.arg("-o").arg(&output_file);
+    if lang_string.test_harness {
+        compiler.arg("--test");
+    }
+    if rustdoc_options.json_unused_externs.is_enabled() && !lang_string.compile_fail {
+        compiler.arg("--error-format=json");
+        compiler.arg("--json").arg("unused-externs");
+        compiler.arg("-Z").arg("unstable-options");
+        compiler.arg("-W").arg("unused_crate_dependencies");
+    }
+    for lib_str in &rustdoc_options.lib_strs {
+        compiler.arg("-L").arg(&lib_str);
+    }
+    for extern_str in &rustdoc_options.extern_strs {
+        compiler.arg("--extern").arg(&extern_str);
+    }
+    compiler.arg("-Ccodegen-units=1");
+    for codegen_options_str in &rustdoc_options.codegen_options_strs {
+        compiler.arg("-C").arg(&codegen_options_str);
+    }
+    for unstable_option_str in &rustdoc_options.unstable_opts_strs {
+        compiler.arg("-Z").arg(&unstable_option_str);
+    }
+    if no_run && !lang_string.compile_fail && rustdoc_options.persist_doctests.is_none() {
+        compiler.arg("--emit=metadata");
+    }
+    compiler.arg("--target").arg(match target {
+        TargetTriple::TargetTriple(s) => s,
+        TargetTriple::TargetJson { path_for_rustdoc, .. } => {
+            path_for_rustdoc.to_str().expect("target path must be valid unicode").to_string()
+        }
+    });
+    if let ErrorOutputType::HumanReadable(kind) = rustdoc_options.error_format {
+        let (short, color_config) = kind.unzip();
+
+        if short {
+            compiler.arg("--error-format").arg("short");
+        }
+
+        match color_config {
+            ColorConfig::Never => {
+                compiler.arg("--color").arg("never");
+            }
+            ColorConfig::Always => {
+                compiler.arg("--color").arg("always");
+            }
+            ColorConfig::Auto => {
+                compiler.arg("--color").arg(if supports_color { "always" } else { "never" });
+            }
+        }
+    }
+
+    compiler.arg("-");
+    compiler.stdin(Stdio::piped());
+    compiler.stderr(Stdio::piped());
+
+    let mut child = compiler.spawn().expect("Failed to spawn rustc process");
+    {
+        let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+        stdin.write_all(test.as_bytes()).expect("could write out test sources");
+    }
+    let output = child.wait_with_output().expect("Failed to read stdout");
+
+    struct Bomb<'a>(&'a str);
+    impl Drop for Bomb<'_> {
+        fn drop(&mut self) {
+            eprint!("{}", self.0);
+        }
+    }
+    let mut out = str::from_utf8(&output.stderr)
+        .unwrap()
+        .lines()
+        .filter(|l| {
+            if let Ok(uext) = serde_json::from_str::<UnusedExterns>(l) {
+                report_unused_externs(uext);
+                false
+            } else {
+                true
+            }
+        })
+        .intersperse_with(|| "\n")
+        .collect::<String>();
+
+    // Add a \n to the end to properly terminate the last line,
+    // but only if there was output to be printed
+    if !out.is_empty() {
+        out.push('\n');
+    }
+
+    let _bomb = Bomb(&out);
+    match (output.status.success(), lang_string.compile_fail) {
+        (true, true) => {
+            return Err(TestFailure::UnexpectedCompilePass);
+        }
+        (true, false) => {}
+        (false, true) => {
+            if !lang_string.error_codes.is_empty() {
+                // We used to check if the output contained "error[{}]: " but since we added the
+                // colored output, we can't anymore because of the color escape characters before
+                // the ":".
+                lang_string.error_codes.retain(|err| !out.contains(&format!("error[{err}]")));
+
+                if !lang_string.error_codes.is_empty() {
+                    return Err(TestFailure::MissingErrorCodes(lang_string.error_codes));
+                }
+            }
+        }
+        (false, false) => {
+            return Err(TestFailure::CompileError);
+        }
+    }
+
+    if no_run {
+        return Ok(());
+    }
+
+    // Run the code!
+    let mut cmd;
+
+    if let Some(tool) = runtool {
+        cmd = Command::new(tool);
+        cmd.args(runtool_args);
+        cmd.arg(output_file);
+    } else {
+        cmd = Command::new(output_file);
+    }
+    if let Some(run_directory) = rustdoc_options.test_run_directory {
+        cmd.current_dir(run_directory);
+    }
+
+    let result = if rustdoc_options.nocapture {
+        cmd.status().map(|status| process::Output {
+            status,
+            stdout: Vec::new(),
+            stderr: Vec::new(),
+        })
+    } else {
+        cmd.output()
+    };
+    match result {
+        Err(e) => return Err(TestFailure::ExecutionError(e)),
+        Ok(out) => {
+            if lang_string.should_panic && out.status.success() {
+                return Err(TestFailure::UnexpectedRunPass);
+            } else if !lang_string.should_panic && !out.status.success() {
+                return Err(TestFailure::ExecutionFailure(out));
+            }
+        }
+    }
+
+    Ok(())
+}
+
+/// Transforms a test into code that can be compiled into a Rust binary, and returns the number of
+/// lines before the test code begins as well as if the output stream supports colors or not.
+pub(crate) fn make_test(
+    s: &str,
+    crate_name: Option<&str>,
+    dont_insert_main: bool,
+    opts: &GlobalTestOptions,
+    edition: Edition,
+    test_id: Option<&str>,
+) -> (String, usize, bool) {
+    let (crate_attrs, everything_else, crates) = partition_source(s, edition);
+    let everything_else = everything_else.trim();
+    let mut line_offset = 0;
+    let mut prog = String::new();
+    let mut supports_color = false;
+
+    if opts.attrs.is_empty() {
+        // If there aren't any attributes supplied by #![doc(test(attr(...)))], then allow some
+        // lints that are commonly triggered in doctests. The crate-level test attributes are
+        // commonly used to make tests fail in case they trigger warnings, so having this there in
+        // that case may cause some tests to pass when they shouldn't have.
+        prog.push_str("#![allow(unused)]\n");
+        line_offset += 1;
+    }
+
+    // Next, any attributes that came from the crate root via #![doc(test(attr(...)))].
+    for attr in &opts.attrs {
+        prog.push_str(&format!("#![{attr}]\n"));
+        line_offset += 1;
+    }
+
+    // Now push any outer attributes from the example, assuming they
+    // are intended to be crate attributes.
+    prog.push_str(&crate_attrs);
+    prog.push_str(&crates);
+
+    // Uses librustc_ast to parse the doctest and find if there's a main fn and the extern
+    // crate already is included.
+    let result = rustc_driver::catch_fatal_errors(|| {
+        rustc_span::create_session_if_not_set_then(edition, |_| {
+            use rustc_errors::emitter::{Emitter, EmitterWriter};
+            use rustc_errors::Handler;
+            use rustc_parse::parser::ForceCollect;
+            use rustc_span::source_map::FilePathMapping;
+
+            let filename = FileName::anon_source_code(s);
+            let source = crates + everything_else;
+
+            // Any errors in parsing should also appear when the doctest is compiled for real, so just
+            // send all the errors that librustc_ast emits directly into a `Sink` instead of stderr.
+            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let fallback_bundle =
+                rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+            supports_color = EmitterWriter::stderr(
+                ColorConfig::Auto,
+                None,
+                None,
+                fallback_bundle.clone(),
+                false,
+                false,
+                Some(80),
+                false,
+            )
+            .supports_color();
+
+            let emitter = EmitterWriter::new(
+                Box::new(io::sink()),
+                None,
+                None,
+                fallback_bundle,
+                false,
+                false,
+                false,
+                None,
+                false,
+            );
+
+            // FIXME(misdreavus): pass `-Z treat-err-as-bug` to the doctest parser
+            let handler = Handler::with_emitter(false, None, Box::new(emitter));
+            let sess = ParseSess::with_span_handler(handler, sm);
+
+            let mut found_main = false;
+            let mut found_extern_crate = crate_name.is_none();
+            let mut found_macro = false;
+
+            let mut parser = match maybe_new_parser_from_source_str(&sess, filename, source) {
+                Ok(p) => p,
+                Err(errs) => {
+                    drop(errs);
+                    return (found_main, found_extern_crate, found_macro);
+                }
+            };
+
+            loop {
+                match parser.parse_item(ForceCollect::No) {
+                    Ok(Some(item)) => {
+                        if !found_main {
+                            if let ast::ItemKind::Fn(..) = item.kind {
+                                if item.ident.name == sym::main {
+                                    found_main = true;
+                                }
+                            }
+                        }
+
+                        if !found_extern_crate {
+                            if let ast::ItemKind::ExternCrate(original) = item.kind {
+                                // This code will never be reached if `crate_name` is none because
+                                // `found_extern_crate` is initialized to `true` if it is none.
+                                let crate_name = crate_name.unwrap();
+
+                                match original {
+                                    Some(name) => found_extern_crate = name.as_str() == crate_name,
+                                    None => found_extern_crate = item.ident.as_str() == crate_name,
+                                }
+                            }
+                        }
+
+                        if !found_macro {
+                            if let ast::ItemKind::MacCall(..) = item.kind {
+                                found_macro = true;
+                            }
+                        }
+
+                        if found_main && found_extern_crate {
+                            break;
+                        }
+                    }
+                    Ok(None) => break,
+                    Err(e) => {
+                        e.cancel();
+                        break;
+                    }
+                }
+
+                // The supplied slice is only used for diagnostics,
+                // which are swallowed here anyway.
+                parser.maybe_consume_incorrect_semicolon(&[]);
+            }
+
+            // Reset errors so that they won't be reported as compiler bugs when dropping the
+            // handler. Any errors in the tests will be reported when the test file is compiled,
+            // Note that we still need to cancel the errors above otherwise `DiagnosticBuilder`
+            // will panic on drop.
+            sess.span_diagnostic.reset_err_count();
+
+            (found_main, found_extern_crate, found_macro)
+        })
+    });
+    let Ok((already_has_main, already_has_extern_crate, found_macro)) = result
+    else {
+        // If the parser panicked due to a fatal error, pass the test code through unchanged.
+        // The error will be reported during compilation.
+        return (s.to_owned(), 0, false);
+    };
+
+    // If a doctest's `fn main` is being masked by a wrapper macro, the parsing loop above won't
+    // see it. In that case, run the old text-based scan to see if they at least have a main
+    // function written inside a macro invocation. See
+    // https://github.com/rust-lang/rust/issues/56898
+    let already_has_main = if found_macro && !already_has_main {
+        s.lines()
+            .map(|line| {
+                let comment = line.find("//");
+                if let Some(comment_begins) = comment { &line[0..comment_begins] } else { line }
+            })
+            .any(|code| code.contains("fn main"))
+    } else {
+        already_has_main
+    };
+
+    // Don't inject `extern crate std` because it's already injected by the
+    // compiler.
+    if !already_has_extern_crate && !opts.no_crate_inject && crate_name != Some("std") {
+        if let Some(crate_name) = crate_name {
+            // Don't inject `extern crate` if the crate is never used.
+            // NOTE: this is terribly inaccurate because it doesn't actually
+            // parse the source, but only has false positives, not false
+            // negatives.
+            if s.contains(crate_name) {
+                prog.push_str(&format!("extern crate r#{crate_name};\n"));
+                line_offset += 1;
+            }
+        }
+    }
+
+    // FIXME: This code cannot yet handle no_std test cases yet
+    if dont_insert_main || already_has_main || prog.contains("![no_std]") {
+        prog.push_str(everything_else);
+    } else {
+        let returns_result = everything_else.trim_end().ends_with("(())");
+        // Give each doctest main function a unique name.
+        // This is for example needed for the tooling around `-C instrument-coverage`.
+        let inner_fn_name = if let Some(test_id) = test_id {
+            format!("_doctest_main_{test_id}")
+        } else {
+            "_inner".into()
+        };
+        let inner_attr = if test_id.is_some() { "#[allow(non_snake_case)] " } else { "" };
+        let (main_pre, main_post) = if returns_result {
+            (
+                format!(
+                    "fn main() {{ {inner_attr}fn {inner_fn_name}() -> Result<(), impl core::fmt::Debug> {{\n",
+                ),
+                format!("\n}} {inner_fn_name}().unwrap() }}"),
+            )
+        } else if test_id.is_some() {
+            (
+                format!("fn main() {{ {inner_attr}fn {inner_fn_name}() {{\n",),
+                format!("\n}} {inner_fn_name}() }}"),
+            )
+        } else {
+            ("fn main() {\n".into(), "\n}".into())
+        };
+        // Note on newlines: We insert a line/newline *before*, and *after*
+        // the doctest and adjust the `line_offset` accordingly.
+        // In the case of `-C instrument-coverage`, this means that the generated
+        // inner `main` function spans from the doctest opening codeblock to the
+        // closing one. For example
+        // /// ``` <- start of the inner main
+        // /// <- code under doctest
+        // /// ``` <- end of the inner main
+        line_offset += 1;
+
+        prog.extend([&main_pre, everything_else, &main_post].iter().cloned());
+    }
+
+    debug!("final doctest:\n{prog}");
+
+    (prog, line_offset, supports_color)
+}
+
+fn check_if_attr_is_complete(source: &str, edition: Edition) -> bool {
+    if source.is_empty() {
+        // Empty content so nothing to check in here...
+        return true;
+    }
+    rustc_driver::catch_fatal_errors(|| {
+        rustc_span::create_session_if_not_set_then(edition, |_| {
+            use rustc_errors::emitter::EmitterWriter;
+            use rustc_errors::Handler;
+            use rustc_span::source_map::FilePathMapping;
+
+            let filename = FileName::anon_source_code(source);
+            // Any errors in parsing should also appear when the doctest is compiled for real, so just
+            // send all the errors that librustc_ast emits directly into a `Sink` instead of stderr.
+            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+            let fallback_bundle =
+                rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+
+            let emitter = EmitterWriter::new(
+                Box::new(io::sink()),
+                None,
+                None,
+                fallback_bundle,
+                false,
+                false,
+                false,
+                None,
+                false,
+            );
+
+            let handler = Handler::with_emitter(false, None, Box::new(emitter));
+            let sess = ParseSess::with_span_handler(handler, sm);
+            let mut parser =
+                match maybe_new_parser_from_source_str(&sess, filename, source.to_owned()) {
+                    Ok(p) => p,
+                    Err(_) => {
+                        debug!("Cannot build a parser to check mod attr so skipping...");
+                        return true;
+                    }
+                };
+            // If a parsing error happened, it's very likely that the attribute is incomplete.
+            if let Err(e) = parser.parse_attribute(InnerAttrPolicy::Permitted) {
+                e.cancel();
+                return false;
+            }
+            // We now check if there is an unclosed delimiter for the attribute. To do so, we look at
+            // the `unclosed_delims` and see if the opening square bracket was closed.
+            parser
+                .unclosed_delims()
+                .get(0)
+                .map(|unclosed| {
+                    unclosed.unclosed_span.map(|s| s.lo()).unwrap_or(BytePos(0)) != BytePos(2)
+                })
+                .unwrap_or(true)
+        })
+    })
+    .unwrap_or(false)
+}
+
+fn partition_source(s: &str, edition: Edition) -> (String, String, String) {
+    #[derive(Copy, Clone, PartialEq)]
+    enum PartitionState {
+        Attrs,
+        Crates,
+        Other,
+    }
+    let mut state = PartitionState::Attrs;
+    let mut before = String::new();
+    let mut crates = String::new();
+    let mut after = String::new();
+
+    let mut mod_attr_pending = String::new();
+
+    for line in s.lines() {
+        let trimline = line.trim();
+
+        // FIXME(misdreavus): if a doc comment is placed on an extern crate statement, it will be
+        // shunted into "everything else"
+        match state {
+            PartitionState::Attrs => {
+                state = if trimline.starts_with("#![") {
+                    if !check_if_attr_is_complete(line, edition) {
+                        mod_attr_pending = line.to_owned();
+                    } else {
+                        mod_attr_pending.clear();
+                    }
+                    PartitionState::Attrs
+                } else if trimline.chars().all(|c| c.is_whitespace())
+                    || (trimline.starts_with("//") && !trimline.starts_with("///"))
+                {
+                    PartitionState::Attrs
+                } else if trimline.starts_with("extern crate")
+                    || trimline.starts_with("#[macro_use] extern crate")
+                {
+                    PartitionState::Crates
+                } else {
+                    // First we check if the previous attribute was "complete"...
+                    if !mod_attr_pending.is_empty() {
+                        // If not, then we append the new line into the pending attribute to check
+                        // if this time it's complete...
+                        mod_attr_pending.push_str(line);
+                        if !trimline.is_empty()
+                            && check_if_attr_is_complete(&mod_attr_pending, edition)
+                        {
+                            // If it's complete, then we can clear the pending content.
+                            mod_attr_pending.clear();
+                        }
+                        // In any case, this is considered as `PartitionState::Attrs` so it's
+                        // prepended before rustdoc's inserts.
+                        PartitionState::Attrs
+                    } else {
+                        PartitionState::Other
+                    }
+                };
+            }
+            PartitionState::Crates => {
+                state = if trimline.starts_with("extern crate")
+                    || trimline.starts_with("#[macro_use] extern crate")
+                    || trimline.chars().all(|c| c.is_whitespace())
+                    || (trimline.starts_with("//") && !trimline.starts_with("///"))
+                {
+                    PartitionState::Crates
+                } else {
+                    PartitionState::Other
+                };
+            }
+            PartitionState::Other => {}
+        }
+
+        match state {
+            PartitionState::Attrs => {
+                before.push_str(line);
+                before.push('\n');
+            }
+            PartitionState::Crates => {
+                crates.push_str(line);
+                crates.push('\n');
+            }
+            PartitionState::Other => {
+                after.push_str(line);
+                after.push('\n');
+            }
+        }
+    }
+
+    debug!("before:\n{before}");
+    debug!("crates:\n{crates}");
+    debug!("after:\n{after}");
+
+    (before, after, crates)
+}
+
+pub(crate) trait Tester {
+    fn add_test(&mut self, test: String, config: LangString, line: usize);
+    fn get_line(&self) -> usize {
+        0
+    }
+    fn register_header(&mut self, _name: &str, _level: u32) {}
+}
+
+pub(crate) struct Collector {
+    pub(crate) tests: Vec<test::TestDescAndFn>,
+
+    // The name of the test displayed to the user, separated by `::`.
+    //
+    // In tests from Rust source, this is the path to the item
+    // e.g., `["std", "vec", "Vec", "push"]`.
+    //
+    // In tests from a markdown file, this is the titles of all headers (h1~h6)
+    // of the sections that contain the code block, e.g., if the markdown file is
+    // written as:
+    //
+    // ``````markdown
+    // # Title
+    //
+    // ## Subtitle
+    //
+    // ```rust
+    // assert!(true);
+    // ```
+    // ``````
+    //
+    // the `names` vector of that test will be `["Title", "Subtitle"]`.
+    names: Vec<String>,
+
+    rustdoc_options: RustdocOptions,
+    use_headers: bool,
+    enable_per_target_ignores: bool,
+    crate_name: Symbol,
+    opts: GlobalTestOptions,
+    position: Span,
+    source_map: Option<Lrc<SourceMap>>,
+    filename: Option<PathBuf>,
+    visited_tests: FxHashMap<(String, usize), usize>,
+    unused_extern_reports: Arc<Mutex<Vec<UnusedExterns>>>,
+    compiling_test_count: AtomicUsize,
+}
+
+impl Collector {
+    pub(crate) fn new(
+        crate_name: Symbol,
+        rustdoc_options: RustdocOptions,
+        use_headers: bool,
+        opts: GlobalTestOptions,
+        source_map: Option<Lrc<SourceMap>>,
+        filename: Option<PathBuf>,
+        enable_per_target_ignores: bool,
+    ) -> Collector {
+        Collector {
+            tests: Vec::new(),
+            names: Vec::new(),
+            rustdoc_options,
+            use_headers,
+            enable_per_target_ignores,
+            crate_name,
+            opts,
+            position: DUMMY_SP,
+            source_map,
+            filename,
+            visited_tests: FxHashMap::default(),
+            unused_extern_reports: Default::default(),
+            compiling_test_count: AtomicUsize::new(0),
+        }
+    }
+
+    fn generate_name(&self, line: usize, filename: &FileName) -> String {
+        let mut item_path = self.names.join("::");
+        item_path.retain(|c| c != ' ');
+        if !item_path.is_empty() {
+            item_path.push(' ');
+        }
+        format!("{} - {}(line {})", filename.prefer_local(), item_path, line)
+    }
+
+    pub(crate) fn set_position(&mut self, position: Span) {
+        self.position = position;
+    }
+
+    fn get_filename(&self) -> FileName {
+        if let Some(ref source_map) = self.source_map {
+            let filename = source_map.span_to_filename(self.position);
+            if let FileName::Real(ref filename) = filename {
+                if let Ok(cur_dir) = env::current_dir() {
+                    if let Some(local_path) = filename.local_path() {
+                        if let Ok(path) = local_path.strip_prefix(&cur_dir) {
+                            return path.to_owned().into();
+                        }
+                    }
+                }
+            }
+            filename
+        } else if let Some(ref filename) = self.filename {
+            filename.clone().into()
+        } else {
+            FileName::Custom("input".to_owned())
+        }
+    }
+}
+
+impl Tester for Collector {
+    fn add_test(&mut self, test: String, config: LangString, line: usize) {
+        let filename = self.get_filename();
+        let name = self.generate_name(line, &filename);
+        let crate_name = self.crate_name.to_string();
+        let opts = self.opts.clone();
+        let edition = config.edition.unwrap_or(self.rustdoc_options.edition);
+        let rustdoc_options = self.rustdoc_options.clone();
+        let runtool = self.rustdoc_options.runtool.clone();
+        let runtool_args = self.rustdoc_options.runtool_args.clone();
+        let target = self.rustdoc_options.target.clone();
+        let target_str = target.to_string();
+        let unused_externs = self.unused_extern_reports.clone();
+        let no_run = config.no_run || rustdoc_options.no_run;
+        if !config.compile_fail {
+            self.compiling_test_count.fetch_add(1, Ordering::SeqCst);
+        }
+
+        let path = match &filename {
+            FileName::Real(path) => {
+                if let Some(local_path) = path.local_path() {
+                    local_path.to_path_buf()
+                } else {
+                    // Somehow we got the filename from the metadata of another crate, should never happen
+                    unreachable!("doctest from a different crate");
+                }
+            }
+            _ => PathBuf::from(r"doctest.rs"),
+        };
+
+        // For example `module/file.rs` would become `module_file_rs`
+        let file = filename
+            .prefer_local()
+            .to_string_lossy()
+            .chars()
+            .map(|c| if c.is_ascii_alphanumeric() { c } else { '_' })
+            .collect::<String>();
+        let test_id = format!(
+            "{file}_{line}_{number}",
+            file = file,
+            line = line,
+            number = {
+                // Increases the current test number, if this file already
+                // exists or it creates a new entry with a test number of 0.
+                self.visited_tests.entry((file.clone(), line)).and_modify(|v| *v += 1).or_insert(0)
+            },
+        );
+        let outdir = if let Some(mut path) = rustdoc_options.persist_doctests.clone() {
+            path.push(&test_id);
+
+            if let Err(err) = std::fs::create_dir_all(&path) {
+                eprintln!("Couldn't create directory for doctest executables: {}", err);
+                panic::resume_unwind(Box::new(()));
+            }
+
+            DirState::Perm(path)
+        } else {
+            DirState::Temp(
+                TempFileBuilder::new()
+                    .prefix("rustdoctest")
+                    .tempdir()
+                    .expect("rustdoc needs a tempdir"),
+            )
+        };
+
+        debug!("creating test {name}: {test}");
+        self.tests.push(test::TestDescAndFn {
+            desc: test::TestDesc {
+                name: test::DynTestName(name),
+                ignore: match config.ignore {
+                    Ignore::All => true,
+                    Ignore::None => false,
+                    Ignore::Some(ref ignores) => ignores.iter().any(|s| target_str.contains(s)),
+                },
+                ignore_message: None,
+                // compiler failures are test failures
+                should_panic: test::ShouldPanic::No,
+                compile_fail: config.compile_fail,
+                no_run,
+                test_type: test::TestType::DocTest,
+            },
+            testfn: test::DynTestFn(Box::new(move || {
+                let report_unused_externs = |uext| {
+                    unused_externs.lock().unwrap().push(uext);
+                };
+                let res = run_test(
+                    &test,
+                    &crate_name,
+                    line,
+                    rustdoc_options,
+                    config,
+                    no_run,
+                    runtool,
+                    runtool_args,
+                    target,
+                    &opts,
+                    edition,
+                    outdir,
+                    path,
+                    &test_id,
+                    report_unused_externs,
+                );
+
+                if let Err(err) = res {
+                    match err {
+                        TestFailure::CompileError => {
+                            eprint!("Couldn't compile the test.");
+                        }
+                        TestFailure::UnexpectedCompilePass => {
+                            eprint!("Test compiled successfully, but it's marked `compile_fail`.");
+                        }
+                        TestFailure::UnexpectedRunPass => {
+                            eprint!("Test executable succeeded, but it's marked `should_panic`.");
+                        }
+                        TestFailure::MissingErrorCodes(codes) => {
+                            eprint!("Some expected error codes were not found: {:?}", codes);
+                        }
+                        TestFailure::ExecutionError(err) => {
+                            eprint!("Couldn't run the test: {err}");
+                            if err.kind() == io::ErrorKind::PermissionDenied {
+                                eprint!(" - maybe your tempdir is mounted with noexec?");
+                            }
+                        }
+                        TestFailure::ExecutionFailure(out) => {
+                            eprintln!("Test executable failed ({reason}).", reason = out.status);
+
+                            // FIXME(#12309): An unfortunate side-effect of capturing the test
+                            // executable's output is that the relative ordering between the test's
+                            // stdout and stderr is lost. However, this is better than the
+                            // alternative: if the test executable inherited the parent's I/O
+                            // handles the output wouldn't be captured at all, even on success.
+                            //
+                            // The ordering could be preserved if the test process' stderr was
+                            // redirected to stdout, but that functionality does not exist in the
+                            // standard library, so it may not be portable enough.
+                            let stdout = str::from_utf8(&out.stdout).unwrap_or_default();
+                            let stderr = str::from_utf8(&out.stderr).unwrap_or_default();
+
+                            if !stdout.is_empty() || !stderr.is_empty() {
+                                eprintln!();
+
+                                if !stdout.is_empty() {
+                                    eprintln!("stdout:\n{stdout}");
+                                }
+
+                                if !stderr.is_empty() {
+                                    eprintln!("stderr:\n{stderr}");
+                                }
+                            }
+                        }
+                    }
+
+                    panic::resume_unwind(Box::new(()));
+                }
+            })),
+        });
+    }
+
+    fn get_line(&self) -> usize {
+        if let Some(ref source_map) = self.source_map {
+            let line = self.position.lo().to_usize();
+            let line = source_map.lookup_char_pos(BytePos(line as u32)).line;
+            if line > 0 { line - 1 } else { line }
+        } else {
+            0
+        }
+    }
+
+    fn register_header(&mut self, name: &str, level: u32) {
+        if self.use_headers {
+            // We use these headings as test names, so it's good if
+            // they're valid identifiers.
+            let name = name
+                .chars()
+                .enumerate()
+                .map(|(i, c)| {
+                    if (i == 0 && rustc_lexer::is_id_start(c))
+                        || (i != 0 && rustc_lexer::is_id_continue(c))
+                    {
+                        c
+                    } else {
+                        '_'
+                    }
+                })
+                .collect::<String>();
+
+            // Here we try to efficiently assemble the header titles into the
+            // test name in the form of `h1::h2::h3::h4::h5::h6`.
+            //
+            // Suppose that originally `self.names` contains `[h1, h2, h3]`...
+            let level = level as usize;
+            if level <= self.names.len() {
+                // ... Consider `level == 2`. All headers in the lower levels
+                // are irrelevant in this new level. So we should reset
+                // `self.names` to contain headers until <h2>, and replace that
+                // slot with the new name: `[h1, name]`.
+                self.names.truncate(level);
+                self.names[level - 1] = name;
+            } else {
+                // ... On the other hand, consider `level == 5`. This means we
+                // need to extend `self.names` to contain five headers. We fill
+                // in the missing level (<h4>) with `_`. Thus `self.names` will
+                // become `[h1, h2, h3, "_", name]`.
+                if level - 1 > self.names.len() {
+                    self.names.resize(level - 1, "_".to_owned());
+                }
+                self.names.push(name);
+            }
+        }
+    }
+}
+
+struct HirCollector<'a, 'hir, 'tcx> {
+    sess: &'a Session,
+    collector: &'a mut Collector,
+    map: Map<'hir>,
+    codes: ErrorCodes,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl<'a, 'hir, 'tcx> HirCollector<'a, 'hir, 'tcx> {
+    fn visit_testable<F: FnOnce(&mut Self)>(
+        &mut self,
+        name: String,
+        hir_id: HirId,
+        sp: Span,
+        nested: F,
+    ) {
+        let ast_attrs = self.tcx.hir().attrs(hir_id);
+        if let Some(ref cfg) = ast_attrs.cfg(self.tcx, &FxHashSet::default()) {
+            if !cfg.matches(&self.sess.parse_sess, Some(self.sess.features_untracked())) {
+                return;
+            }
+        }
+
+        let has_name = !name.is_empty();
+        if has_name {
+            self.collector.names.push(name);
+        }
+
+        // The collapse-docs pass won't combine sugared/raw doc attributes, or included files with
+        // anything else, this will combine them for us.
+        let attrs = Attributes::from_ast(ast_attrs);
+        if let Some(doc) = attrs.collapsed_doc_value() {
+            // Use the outermost invocation, so that doctest names come from where the docs were written.
+            let span = ast_attrs
+                .span()
+                .map(|span| span.ctxt().outer_expn().expansion_cause().unwrap_or(span))
+                .unwrap_or(DUMMY_SP);
+            self.collector.set_position(span);
+            markdown::find_testable_code(
+                &doc,
+                self.collector,
+                self.codes,
+                self.collector.enable_per_target_ignores,
+                Some(&crate::html::markdown::ExtraInfo::new(
+                    self.tcx,
+                    hir_id,
+                    span_of_attrs(&attrs).unwrap_or(sp),
+                )),
+            );
+        }
+
+        nested(self);
+
+        if has_name {
+            self.collector.names.pop();
+        }
+    }
+}
+
+impl<'a, 'hir, 'tcx> intravisit::Visitor<'hir> for HirCollector<'a, 'hir, 'tcx> {
+    type NestedFilter = nested_filter::All;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.map
+    }
+
+    fn visit_item(&mut self, item: &'hir hir::Item<'_>) {
+        let name = match &item.kind {
+            hir::ItemKind::Impl(impl_) => {
+                rustc_hir_pretty::id_to_string(&self.map, impl_.self_ty.hir_id)
+            }
+            _ => item.ident.to_string(),
+        };
+
+        self.visit_testable(name, item.hir_id(), item.span, |this| {
+            intravisit::walk_item(this, item);
+        });
+    }
+
+    fn visit_trait_item(&mut self, item: &'hir hir::TraitItem<'_>) {
+        self.visit_testable(item.ident.to_string(), item.hir_id(), item.span, |this| {
+            intravisit::walk_trait_item(this, item);
+        });
+    }
+
+    fn visit_impl_item(&mut self, item: &'hir hir::ImplItem<'_>) {
+        self.visit_testable(item.ident.to_string(), item.hir_id(), item.span, |this| {
+            intravisit::walk_impl_item(this, item);
+        });
+    }
+
+    fn visit_foreign_item(&mut self, item: &'hir hir::ForeignItem<'_>) {
+        self.visit_testable(item.ident.to_string(), item.hir_id(), item.span, |this| {
+            intravisit::walk_foreign_item(this, item);
+        });
+    }
+
+    fn visit_variant(
+        &mut self,
+        v: &'hir hir::Variant<'_>,
+        g: &'hir hir::Generics<'_>,
+        item_id: hir::HirId,
+    ) {
+        self.visit_testable(v.ident.to_string(), v.id, v.span, |this| {
+            intravisit::walk_variant(this, v, g, item_id);
+        });
+    }
+
+    fn visit_field_def(&mut self, f: &'hir hir::FieldDef<'_>) {
+        self.visit_testable(f.ident.to_string(), f.hir_id, f.span, |this| {
+            intravisit::walk_field_def(this, f);
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/doctest/tests.rs b/src/librustdoc/doctest/tests.rs
new file mode 100644
index 000000000..360d2259e
--- /dev/null
+++ b/src/librustdoc/doctest/tests.rs
@@ -0,0 +1,300 @@
+use super::{make_test, GlobalTestOptions};
+use rustc_span::edition::DEFAULT_EDITION;
+
+#[test]
+fn make_test_basic() {
+    //basic use: wraps with `fn main`, adds `#![allow(unused)]`
+    let opts = GlobalTestOptions::default();
+    let input = "assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+fn main() {
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_crate_name_no_use() {
+    // If you give a crate name but *don't* use it within the test, it won't bother inserting
+    // the `extern crate` statement.
+    let opts = GlobalTestOptions::default();
+    let input = "assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+fn main() {
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_crate_name() {
+    // If you give a crate name and use it within the test, it will insert an `extern crate`
+    // statement before `fn main`.
+    let opts = GlobalTestOptions::default();
+    let input = "use asdf::qwop;
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+extern crate r#asdf;
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 3));
+}
+
+#[test]
+fn make_test_no_crate_inject() {
+    // Even if you do use the crate within the test, setting `opts.no_crate_inject` will skip
+    // adding it anyway.
+    let opts = GlobalTestOptions { no_crate_inject: true, attrs: vec![] };
+    let input = "use asdf::qwop;
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_ignore_std() {
+    // Even if you include a crate name, and use it in the doctest, we still won't include an
+    // `extern crate` statement if the crate is "std" -- that's included already by the
+    // compiler!
+    let opts = GlobalTestOptions::default();
+    let input = "use std::*;
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+fn main() {
+use std::*;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("std"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_manual_extern_crate() {
+    // When you manually include an `extern crate` statement in your doctest, `make_test`
+    // assumes you've included one for your own crate too.
+    let opts = GlobalTestOptions::default();
+    let input = "extern crate asdf;
+use asdf::qwop;
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+extern crate asdf;
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_manual_extern_crate_with_macro_use() {
+    let opts = GlobalTestOptions::default();
+    let input = "#[macro_use] extern crate asdf;
+use asdf::qwop;
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+#[macro_use] extern crate asdf;
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_opts_attrs() {
+    // If you supplied some doctest attributes with `#![doc(test(attr(...)))]`, it will use
+    // those instead of the stock `#![allow(unused)]`.
+    let mut opts = GlobalTestOptions::default();
+    opts.attrs.push("feature(sick_rad)".to_string());
+    let input = "use asdf::qwop;
+assert_eq!(2+2, 4);";
+    let expected = "#![feature(sick_rad)]
+extern crate r#asdf;
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 3));
+
+    // Adding more will also bump the returned line offset.
+    opts.attrs.push("feature(hella_dope)".to_string());
+    let expected = "#![feature(sick_rad)]
+#![feature(hella_dope)]
+extern crate r#asdf;
+fn main() {
+use asdf::qwop;
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 4));
+}
+
+#[test]
+fn make_test_crate_attrs() {
+    // Including inner attributes in your doctest will apply them to the whole "crate", pasting
+    // them outside the generated main function.
+    let opts = GlobalTestOptions::default();
+    let input = "#![feature(sick_rad)]
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+#![feature(sick_rad)]
+fn main() {
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_with_main() {
+    // Including your own `fn main` wrapper lets the test use it verbatim.
+    let opts = GlobalTestOptions::default();
+    let input = "fn main() {
+    assert_eq!(2+2, 4);
+}";
+    let expected = "#![allow(unused)]
+fn main() {
+    assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 1));
+}
+
+#[test]
+fn make_test_fake_main() {
+    // ... but putting it in a comment will still provide a wrapper.
+    let opts = GlobalTestOptions::default();
+    let input = "//Ceci n'est pas une `fn main`
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+//Ceci n'est pas une `fn main`
+fn main() {
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_dont_insert_main() {
+    // Even with that, if you set `dont_insert_main`, it won't create the `fn main` wrapper.
+    let opts = GlobalTestOptions::default();
+    let input = "//Ceci n'est pas une `fn main`
+assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+//Ceci n'est pas une `fn main`
+assert_eq!(2+2, 4);"
+        .to_string();
+    let (output, len, _) = make_test(input, None, true, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 1));
+}
+
+#[test]
+fn make_test_issues_21299_33731() {
+    let opts = GlobalTestOptions::default();
+
+    let input = "// fn main
+assert_eq!(2+2, 4);";
+
+    let expected = "#![allow(unused)]
+// fn main
+fn main() {
+assert_eq!(2+2, 4);
+}"
+    .to_string();
+
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+
+    let input = "extern crate hella_qwop;
+assert_eq!(asdf::foo, 4);";
+
+    let expected = "#![allow(unused)]
+extern crate hella_qwop;
+extern crate r#asdf;
+fn main() {
+assert_eq!(asdf::foo, 4);
+}"
+    .to_string();
+
+    let (output, len, _) = make_test(input, Some("asdf"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 3));
+}
+
+#[test]
+fn make_test_main_in_macro() {
+    let opts = GlobalTestOptions::default();
+    let input = "#[macro_use] extern crate my_crate;
+test_wrapper! {
+    fn main() {}
+}";
+    let expected = "#![allow(unused)]
+#[macro_use] extern crate my_crate;
+test_wrapper! {
+    fn main() {}
+}"
+    .to_string();
+
+    let (output, len, _) = make_test(input, Some("my_crate"), false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 1));
+}
+
+#[test]
+fn make_test_returns_result() {
+    // creates an inner function and unwraps it
+    let opts = GlobalTestOptions::default();
+    let input = "use std::io;
+let mut input = String::new();
+io::stdin().read_line(&mut input)?;
+Ok::<(), io:Error>(())";
+    let expected = "#![allow(unused)]
+fn main() { fn _inner() -> Result<(), impl core::fmt::Debug> {
+use std::io;
+let mut input = String::new();
+io::stdin().read_line(&mut input)?;
+Ok::<(), io:Error>(())
+} _inner().unwrap() }"
+        .to_string();
+    let (output, len, _) = make_test(input, None, false, &opts, DEFAULT_EDITION, None);
+    assert_eq!((output, len), (expected, 2));
+}
+
+#[test]
+fn make_test_named_wrapper() {
+    // creates an inner function with a specific name
+    let opts = GlobalTestOptions::default();
+    let input = "assert_eq!(2+2, 4);";
+    let expected = "#![allow(unused)]
+fn main() { #[allow(non_snake_case)] fn _doctest_main__some_unique_name() {
+assert_eq!(2+2, 4);
+} _doctest_main__some_unique_name() }"
+        .to_string();
+    let (output, len, _) =
+        make_test(input, None, false, &opts, DEFAULT_EDITION, Some("_some_unique_name"));
+    assert_eq!((output, len), (expected, 2));
+}
diff --git a/src/librustdoc/error.rs b/src/librustdoc/error.rs
new file mode 100644
index 000000000..6ed7eab1a
--- /dev/null
+++ b/src/librustdoc/error.rs
@@ -0,0 +1,59 @@
+use std::error;
+use std::fmt::{self, Formatter};
+use std::path::{Path, PathBuf};
+
+use crate::docfs::PathError;
+
+#[derive(Debug)]
+pub(crate) struct Error {
+    pub(crate) file: PathBuf,
+    pub(crate) error: String,
+}
+
+impl error::Error for Error {}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let file = self.file.display().to_string();
+        if file.is_empty() {
+            write!(f, "{}", self.error)
+        } else {
+            write!(f, "\"{}\": {}", self.file.display(), self.error)
+        }
+    }
+}
+
+impl PathError for Error {
+    fn new<S, P: AsRef<Path>>(e: S, path: P) -> Error
+    where
+        S: ToString + Sized,
+    {
+        Error { file: path.as_ref().to_path_buf(), error: e.to_string() }
+    }
+}
+
+#[macro_export]
+macro_rules! try_none {
+    ($e:expr, $file:expr) => {{
+        use std::io;
+        match $e {
+            Some(e) => e,
+            None => {
+                return Err(<crate::error::Error as crate::docfs::PathError>::new(
+                    io::Error::new(io::ErrorKind::Other, "not found"),
+                    $file,
+                ));
+            }
+        }
+    }};
+}
+
+#[macro_export]
+macro_rules! try_err {
+    ($e:expr, $file:expr) => {{
+        match $e {
+            Ok(e) => e,
+            Err(e) => return Err(Error::new(e, $file)),
+        }
+    }};
+}
diff --git a/src/librustdoc/externalfiles.rs b/src/librustdoc/externalfiles.rs
new file mode 100644
index 000000000..37fd909c9
--- /dev/null
+++ b/src/librustdoc/externalfiles.rs
@@ -0,0 +1,107 @@
+use crate::html::markdown::{ErrorCodes, HeadingOffset, IdMap, Markdown, Playground};
+use crate::rustc_span::edition::Edition;
+use std::fs;
+use std::path::Path;
+use std::str;
+
+use serde::Serialize;
+
+#[derive(Clone, Debug, Serialize)]
+pub(crate) struct ExternalHtml {
+    /// Content that will be included inline in the `<head>` section of a
+    /// rendered Markdown file or generated documentation
+    pub(crate) in_header: String,
+    /// Content that will be included inline between `<body>` and the content of
+    /// a rendered Markdown file or generated documentation
+    pub(crate) before_content: String,
+    /// Content that will be included inline between the content and `</body>` of
+    /// a rendered Markdown file or generated documentation
+    pub(crate) after_content: String,
+}
+
+impl ExternalHtml {
+    pub(crate) fn load(
+        in_header: &[String],
+        before_content: &[String],
+        after_content: &[String],
+        md_before_content: &[String],
+        md_after_content: &[String],
+        nightly_build: bool,
+        diag: &rustc_errors::Handler,
+        id_map: &mut IdMap,
+        edition: Edition,
+        playground: &Option<Playground>,
+    ) -> Option<ExternalHtml> {
+        let codes = ErrorCodes::from(nightly_build);
+        let ih = load_external_files(in_header, diag)?;
+        let bc = load_external_files(before_content, diag)?;
+        let m_bc = load_external_files(md_before_content, diag)?;
+        let bc = format!(
+            "{}{}",
+            bc,
+            Markdown {
+                content: &m_bc,
+                links: &[],
+                ids: id_map,
+                error_codes: codes,
+                edition,
+                playground,
+                heading_offset: HeadingOffset::H2,
+            }
+            .into_string()
+        );
+        let ac = load_external_files(after_content, diag)?;
+        let m_ac = load_external_files(md_after_content, diag)?;
+        let ac = format!(
+            "{}{}",
+            ac,
+            Markdown {
+                content: &m_ac,
+                links: &[],
+                ids: id_map,
+                error_codes: codes,
+                edition,
+                playground,
+                heading_offset: HeadingOffset::H2,
+            }
+            .into_string()
+        );
+        Some(ExternalHtml { in_header: ih, before_content: bc, after_content: ac })
+    }
+}
+
+pub(crate) enum LoadStringError {
+    ReadFail,
+    BadUtf8,
+}
+
+pub(crate) fn load_string<P: AsRef<Path>>(
+    file_path: P,
+    diag: &rustc_errors::Handler,
+) -> Result<String, LoadStringError> {
+    let file_path = file_path.as_ref();
+    let contents = match fs::read(file_path) {
+        Ok(bytes) => bytes,
+        Err(e) => {
+            diag.struct_err(&format!("error reading `{}`: {}", file_path.display(), e)).emit();
+            return Err(LoadStringError::ReadFail);
+        }
+    };
+    match str::from_utf8(&contents) {
+        Ok(s) => Ok(s.to_string()),
+        Err(_) => {
+            diag.struct_err(&format!("error reading `{}`: not UTF-8", file_path.display())).emit();
+            Err(LoadStringError::BadUtf8)
+        }
+    }
+}
+
+fn load_external_files(names: &[String], diag: &rustc_errors::Handler) -> Option<String> {
+    let mut out = String::new();
+    for name in names {
+        let Ok(s) = load_string(name, diag) else { return None };
+        out.push_str(&s);
+        out.push('\n');
+    }
+    Some(out)
+}
diff --git a/src/librustdoc/fold.rs b/src/librustdoc/fold.rs
new file mode 100644
index 000000000..6b7e67e2c
--- /dev/null
+++ b/src/librustdoc/fold.rs
@@ -0,0 +1,103 @@
+use crate::clean::*;
+
+pub(crate) fn strip_item(mut item: Item) -> Item {
+    if !matches!(*item.kind, StrippedItem(..)) {
+        item.kind = Box::new(StrippedItem(item.kind));
+    }
+    item
+}
+
+pub(crate) trait DocFolder: Sized {
+    fn fold_item(&mut self, item: Item) -> Option<Item> {
+        Some(self.fold_item_recur(item))
+    }
+
+    /// don't override!
+    fn fold_inner_recur(&mut self, kind: ItemKind) -> ItemKind {
+        match kind {
+            StrippedItem(..) => unreachable!(),
+            ModuleItem(i) => ModuleItem(self.fold_mod(i)),
+            StructItem(mut i) => {
+                i.fields = i.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                StructItem(i)
+            }
+            UnionItem(mut i) => {
+                i.fields = i.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                UnionItem(i)
+            }
+            EnumItem(mut i) => {
+                i.variants = i.variants.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                EnumItem(i)
+            }
+            TraitItem(mut i) => {
+                i.items = i.items.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                TraitItem(i)
+            }
+            ImplItem(mut i) => {
+                i.items = i.items.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                ImplItem(i)
+            }
+            VariantItem(i) => match i {
+                Variant::Struct(mut j) => {
+                    j.fields = j.fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                    VariantItem(Variant::Struct(j))
+                }
+                Variant::Tuple(fields) => {
+                    let fields = fields.into_iter().filter_map(|x| self.fold_item(x)).collect();
+                    VariantItem(Variant::Tuple(fields))
+                }
+                Variant::CLike => VariantItem(Variant::CLike),
+            },
+            ExternCrateItem { src: _ }
+            | ImportItem(_)
+            | FunctionItem(_)
+            | TypedefItem(_)
+            | OpaqueTyItem(_)
+            | StaticItem(_)
+            | ConstantItem(_)
+            | TraitAliasItem(_)
+            | TyMethodItem(_)
+            | MethodItem(_, _)
+            | StructFieldItem(_)
+            | ForeignFunctionItem(_)
+            | ForeignStaticItem(_)
+            | ForeignTypeItem
+            | MacroItem(_)
+            | ProcMacroItem(_)
+            | PrimitiveItem(_)
+            | TyAssocConstItem(..)
+            | AssocConstItem(..)
+            | TyAssocTypeItem(..)
+            | AssocTypeItem(..)
+            | KeywordItem => kind,
+        }
+    }
+
+    /// don't override!
+    fn fold_item_recur(&mut self, mut item: Item) -> Item {
+        item.kind = Box::new(match *item.kind {
+            StrippedItem(box i) => StrippedItem(Box::new(self.fold_inner_recur(i))),
+            _ => self.fold_inner_recur(*item.kind),
+        });
+        item
+    }
+
+    fn fold_mod(&mut self, m: Module) -> Module {
+        Module {
+            span: m.span,
+            items: m.items.into_iter().filter_map(|i| self.fold_item(i)).collect(),
+        }
+    }
+
+    fn fold_crate(&mut self, mut c: Crate) -> Crate {
+        c.module = self.fold_item(c.module).unwrap();
+
+        let external_traits = { std::mem::take(&mut *c.external_traits.borrow_mut()) };
+        for (k, mut v) in external_traits {
+            v.trait_.items = v.trait_.items.into_iter().filter_map(|i| self.fold_item(i)).collect();
+            c.external_traits.borrow_mut().insert(k, v);
+        }
+
+        c
+    }
+}
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
new file mode 100644
index 000000000..2b2691e53
--- /dev/null
+++ b/src/librustdoc/formats/cache.rs
@@ -0,0 +1,569 @@
+use std::mem;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::{CrateNum, DefId};
+use rustc_middle::middle::privacy::AccessLevels;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_span::{sym, Symbol};
+
+use crate::clean::{self, types::ExternalLocation, ExternalCrate, ItemId, PrimitiveType};
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::formats::item_type::ItemType;
+use crate::formats::Impl;
+use crate::html::format::join_with_double_colon;
+use crate::html::markdown::short_markdown_summary;
+use crate::html::render::search_index::get_function_type_for_search;
+use crate::html::render::IndexItem;
+
+/// This cache is used to store information about the [`clean::Crate`] being
+/// rendered in order to provide more useful documentation. This contains
+/// information like all implementors of a trait, all traits a type implements,
+/// documentation for all known traits, etc.
+///
+/// This structure purposefully does not implement `Clone` because it's intended
+/// to be a fairly large and expensive structure to clone. Instead this adheres
+/// to `Send` so it may be stored in an `Arc` instance and shared among the various
+/// rendering threads.
+#[derive(Default)]
+pub(crate) struct Cache {
+    /// Maps a type ID to all known implementations for that type. This is only
+    /// recognized for intra-crate [`clean::Type::Path`]s, and is used to print
+    /// out extra documentation on the page of an enum/struct.
+    ///
+    /// The values of the map are a list of implementations and documentation
+    /// found on that implementation.
+    pub(crate) impls: FxHashMap<DefId, Vec<Impl>>,
+
+    /// Maintains a mapping of local crate `DefId`s to the fully qualified name
+    /// and "short type description" of that node. This is used when generating
+    /// URLs when a type is being linked to. External paths are not located in
+    /// this map because the `External` type itself has all the information
+    /// necessary.
+    pub(crate) paths: FxHashMap<DefId, (Vec<Symbol>, ItemType)>,
+
+    /// Similar to `paths`, but only holds external paths. This is only used for
+    /// generating explicit hyperlinks to other crates.
+    pub(crate) external_paths: FxHashMap<DefId, (Vec<Symbol>, ItemType)>,
+
+    /// Maps local `DefId`s of exported types to fully qualified paths.
+    /// Unlike 'paths', this mapping ignores any renames that occur
+    /// due to 'use' statements.
+    ///
+    /// This map is used when writing out the special 'implementors'
+    /// javascript file. By using the exact path that the type
+    /// is declared with, we ensure that each path will be identical
+    /// to the path used if the corresponding type is inlined. By
+    /// doing this, we can detect duplicate impls on a trait page, and only display
+    /// the impl for the inlined type.
+    pub(crate) exact_paths: FxHashMap<DefId, Vec<Symbol>>,
+
+    /// This map contains information about all known traits of this crate.
+    /// Implementations of a crate should inherit the documentation of the
+    /// parent trait if no extra documentation is specified, and default methods
+    /// should show up in documentation about trait implementations.
+    pub(crate) traits: FxHashMap<DefId, clean::TraitWithExtraInfo>,
+
+    /// When rendering traits, it's often useful to be able to list all
+    /// implementors of the trait, and this mapping is exactly, that: a mapping
+    /// of trait ids to the list of known implementors of the trait
+    pub(crate) implementors: FxHashMap<DefId, Vec<Impl>>,
+
+    /// Cache of where external crate documentation can be found.
+    pub(crate) extern_locations: FxHashMap<CrateNum, ExternalLocation>,
+
+    /// Cache of where documentation for primitives can be found.
+    pub(crate) primitive_locations: FxHashMap<clean::PrimitiveType, DefId>,
+
+    // Note that external items for which `doc(hidden)` applies to are shown as
+    // non-reachable while local items aren't. This is because we're reusing
+    // the access levels from the privacy check pass.
+    pub(crate) access_levels: AccessLevels<DefId>,
+
+    /// The version of the crate being documented, if given from the `--crate-version` flag.
+    pub(crate) crate_version: Option<String>,
+
+    /// Whether to document private items.
+    /// This is stored in `Cache` so it doesn't need to be passed through all rustdoc functions.
+    pub(crate) document_private: bool,
+
+    /// Crates marked with [`#[doc(masked)]`][doc_masked].
+    ///
+    /// [doc_masked]: https://doc.rust-lang.org/nightly/unstable-book/language-features/doc-masked.html
+    pub(crate) masked_crates: FxHashSet<CrateNum>,
+
+    // Private fields only used when initially crawling a crate to build a cache
+    stack: Vec<Symbol>,
+    parent_stack: Vec<ParentStackItem>,
+    stripped_mod: bool,
+
+    pub(crate) search_index: Vec<IndexItem>,
+
+    // In rare case where a structure is defined in one module but implemented
+    // in another, if the implementing module is parsed before defining module,
+    // then the fully qualified name of the structure isn't presented in `paths`
+    // yet when its implementation methods are being indexed. Caches such methods
+    // and their parent id here and indexes them at the end of crate parsing.
+    pub(crate) orphan_impl_items: Vec<OrphanImplItem>,
+
+    // Similarly to `orphan_impl_items`, sometimes trait impls are picked up
+    // even though the trait itself is not exported. This can happen if a trait
+    // was defined in function/expression scope, since the impl will be picked
+    // up by `collect-trait-impls` but the trait won't be scraped out in the HIR
+    // crawl. In order to prevent crashes when looking for notable traits or
+    // when gathering trait documentation on a type, hold impls here while
+    // folding and add them to the cache later on if we find the trait.
+    orphan_trait_impls: Vec<(DefId, FxHashSet<DefId>, Impl)>,
+
+    /// All intra-doc links resolved so far.
+    ///
+    /// Links are indexed by the DefId of the item they document.
+    pub(crate) intra_doc_links: FxHashMap<ItemId, Vec<clean::ItemLink>>,
+    /// Cfg that have been hidden via #![doc(cfg_hide(...))]
+    pub(crate) hidden_cfg: FxHashSet<clean::cfg::Cfg>,
+}
+
+/// This struct is used to wrap the `cache` and `tcx` in order to run `DocFolder`.
+struct CacheBuilder<'a, 'tcx> {
+    cache: &'a mut Cache,
+    /// This field is used to prevent duplicated impl blocks.
+    impl_ids: FxHashMap<DefId, FxHashSet<DefId>>,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl Cache {
+    pub(crate) fn new(access_levels: AccessLevels<DefId>, document_private: bool) -> Self {
+        Cache { access_levels, document_private, ..Cache::default() }
+    }
+
+    /// Populates the `Cache` with more data. The returned `Crate` will be missing some data that was
+    /// in `krate` due to the data being moved into the `Cache`.
+    pub(crate) fn populate(cx: &mut DocContext<'_>, mut krate: clean::Crate) -> clean::Crate {
+        let tcx = cx.tcx;
+
+        // Crawl the crate to build various caches used for the output
+        debug!(?cx.cache.crate_version);
+        cx.cache.traits = krate.external_traits.take();
+
+        // Cache where all our extern crates are located
+        // FIXME: this part is specific to HTML so it'd be nice to remove it from the common code
+        for &crate_num in cx.tcx.crates(()) {
+            let e = ExternalCrate { crate_num };
+
+            let name = e.name(tcx);
+            let render_options = &cx.render_options;
+            let extern_url = render_options.extern_html_root_urls.get(name.as_str()).map(|u| &**u);
+            let extern_url_takes_precedence = render_options.extern_html_root_takes_precedence;
+            let dst = &render_options.output;
+            let location = e.location(extern_url, extern_url_takes_precedence, dst, tcx);
+            cx.cache.extern_locations.insert(e.crate_num, location);
+            cx.cache.external_paths.insert(e.def_id(), (vec![name], ItemType::Module));
+        }
+
+        // FIXME: avoid this clone (requires implementing Default manually)
+        cx.cache.primitive_locations = PrimitiveType::primitive_locations(tcx).clone();
+        for (prim, &def_id) in &cx.cache.primitive_locations {
+            let crate_name = tcx.crate_name(def_id.krate);
+            // Recall that we only allow primitive modules to be at the root-level of the crate.
+            // If that restriction is ever lifted, this will have to include the relative paths instead.
+            cx.cache
+                .external_paths
+                .insert(def_id, (vec![crate_name, prim.as_sym()], ItemType::Primitive));
+        }
+
+        let (krate, mut impl_ids) = {
+            let mut cache_builder =
+                CacheBuilder { tcx, cache: &mut cx.cache, impl_ids: FxHashMap::default() };
+            krate = cache_builder.fold_crate(krate);
+            (krate, cache_builder.impl_ids)
+        };
+
+        for (trait_did, dids, impl_) in cx.cache.orphan_trait_impls.drain(..) {
+            if cx.cache.traits.contains_key(&trait_did) {
+                for did in dids {
+                    if impl_ids.entry(did).or_default().insert(impl_.def_id()) {
+                        cx.cache.impls.entry(did).or_default().push(impl_.clone());
+                    }
+                }
+            }
+        }
+
+        krate
+    }
+}
+
+impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
+    fn fold_item(&mut self, item: clean::Item) -> Option<clean::Item> {
+        if item.item_id.is_local() {
+            debug!("folding {} \"{:?}\", id {:?}", item.type_(), item.name, item.item_id);
+        }
+
+        // If this is a stripped module,
+        // we don't want it or its children in the search index.
+        let orig_stripped_mod = match *item.kind {
+            clean::StrippedItem(box clean::ModuleItem(..)) => {
+                mem::replace(&mut self.cache.stripped_mod, true)
+            }
+            _ => self.cache.stripped_mod,
+        };
+
+        // If the impl is from a masked crate or references something from a
+        // masked crate then remove it completely.
+        if let clean::ImplItem(ref i) = *item.kind {
+            if self.cache.masked_crates.contains(&item.item_id.krate())
+                || i.trait_
+                    .as_ref()
+                    .map_or(false, |t| self.cache.masked_crates.contains(&t.def_id().krate))
+                || i.for_
+                    .def_id(self.cache)
+                    .map_or(false, |d| self.cache.masked_crates.contains(&d.krate))
+            {
+                return None;
+            }
+        }
+
+        // Propagate a trait method's documentation to all implementors of the
+        // trait.
+        if let clean::TraitItem(ref t) = *item.kind {
+            self.cache.traits.entry(item.item_id.expect_def_id()).or_insert_with(|| {
+                clean::TraitWithExtraInfo {
+                    trait_: t.clone(),
+                    is_notable: item.attrs.has_doc_flag(sym::notable_trait),
+                }
+            });
+        }
+
+        // Collect all the implementors of traits.
+        if let clean::ImplItem(ref i) = *item.kind {
+            if let Some(trait_) = &i.trait_ {
+                if !i.kind.is_blanket() {
+                    self.cache
+                        .implementors
+                        .entry(trait_.def_id())
+                        .or_default()
+                        .push(Impl { impl_item: item.clone() });
+                }
+            }
+        }
+
+        // Index this method for searching later on.
+        if let Some(ref s) = item.name.or_else(|| {
+            if item.is_stripped() {
+                None
+            } else if let clean::ImportItem(ref i) = *item.kind &&
+                let clean::ImportKind::Simple(s) = i.kind {
+                Some(s)
+            } else {
+                None
+            }
+        }) {
+            let (parent, is_inherent_impl_item) = match *item.kind {
+                clean::StrippedItem(..) => ((None, None), false),
+                clean::AssocConstItem(..) | clean::AssocTypeItem(..)
+                    if self
+                        .cache
+                        .parent_stack
+                        .last()
+                        .map_or(false, |parent| parent.is_trait_impl()) =>
+                {
+                    // skip associated items in trait impls
+                    ((None, None), false)
+                }
+                clean::TyMethodItem(..)
+                | clean::TyAssocConstItem(..)
+                | clean::TyAssocTypeItem(..)
+                | clean::StructFieldItem(..)
+                | clean::VariantItem(..) => (
+                    (
+                        Some(
+                            self.cache
+                                .parent_stack
+                                .last()
+                                .expect("parent_stack is empty")
+                                .item_id()
+                                .expect_def_id(),
+                        ),
+                        Some(&self.cache.stack[..self.cache.stack.len() - 1]),
+                    ),
+                    false,
+                ),
+                clean::MethodItem(..) | clean::AssocConstItem(..) | clean::AssocTypeItem(..) => {
+                    if self.cache.parent_stack.is_empty() {
+                        ((None, None), false)
+                    } else {
+                        let last = self.cache.parent_stack.last().expect("parent_stack is empty 2");
+                        let did = match &*last {
+                            ParentStackItem::Impl { for_, .. } => for_.def_id(&self.cache),
+                            ParentStackItem::Type(item_id) => item_id.as_def_id(),
+                        };
+                        let path = match did.and_then(|did| self.cache.paths.get(&did)) {
+                            // The current stack not necessarily has correlation
+                            // for where the type was defined. On the other
+                            // hand, `paths` always has the right
+                            // information if present.
+                            Some(&(ref fqp, _)) => Some(&fqp[..fqp.len() - 1]),
+                            None => None,
+                        };
+                        ((did, path), true)
+                    }
+                }
+                _ => ((None, Some(&*self.cache.stack)), false),
+            };
+
+            match parent {
+                (parent, Some(path)) if is_inherent_impl_item || !self.cache.stripped_mod => {
+                    debug_assert!(!item.is_stripped());
+
+                    // A crate has a module at its root, containing all items,
+                    // which should not be indexed. The crate-item itself is
+                    // inserted later on when serializing the search-index.
+                    if item.item_id.as_def_id().map_or(false, |idx| !idx.is_crate_root()) {
+                        let desc = item.doc_value().map_or_else(String::new, |x| {
+                            short_markdown_summary(x.as_str(), &item.link_names(self.cache))
+                        });
+                        self.cache.search_index.push(IndexItem {
+                            ty: item.type_(),
+                            name: s.to_string(),
+                            path: join_with_double_colon(path),
+                            desc,
+                            parent,
+                            parent_idx: None,
+                            search_type: get_function_type_for_search(
+                                &item,
+                                self.tcx,
+                                clean_impl_generics(self.cache.parent_stack.last()).as_ref(),
+                                self.cache,
+                            ),
+                            aliases: item.attrs.get_doc_aliases(),
+                        });
+                    }
+                }
+                (Some(parent), None) if is_inherent_impl_item => {
+                    // We have a parent, but we don't know where they're
+                    // defined yet. Wait for later to index this item.
+                    let impl_generics = clean_impl_generics(self.cache.parent_stack.last());
+                    self.cache.orphan_impl_items.push(OrphanImplItem {
+                        parent,
+                        item: item.clone(),
+                        impl_generics,
+                    });
+                }
+                _ => {}
+            }
+        }
+
+        // Keep track of the fully qualified path for this item.
+        let pushed = match item.name {
+            Some(n) if !n.is_empty() => {
+                self.cache.stack.push(n);
+                true
+            }
+            _ => false,
+        };
+
+        match *item.kind {
+            clean::StructItem(..)
+            | clean::EnumItem(..)
+            | clean::TypedefItem(..)
+            | clean::TraitItem(..)
+            | clean::TraitAliasItem(..)
+            | clean::FunctionItem(..)
+            | clean::ModuleItem(..)
+            | clean::ForeignFunctionItem(..)
+            | clean::ForeignStaticItem(..)
+            | clean::ConstantItem(..)
+            | clean::StaticItem(..)
+            | clean::UnionItem(..)
+            | clean::ForeignTypeItem
+            | clean::MacroItem(..)
+            | clean::ProcMacroItem(..)
+            | clean::VariantItem(..) => {
+                if !self.cache.stripped_mod {
+                    // Re-exported items mean that the same id can show up twice
+                    // in the rustdoc ast that we're looking at. We know,
+                    // however, that a re-exported item doesn't show up in the
+                    // `public_items` map, so we can skip inserting into the
+                    // paths map if there was already an entry present and we're
+                    // not a public item.
+                    if !self.cache.paths.contains_key(&item.item_id.expect_def_id())
+                        || self.cache.access_levels.is_public(item.item_id.expect_def_id())
+                    {
+                        self.cache.paths.insert(
+                            item.item_id.expect_def_id(),
+                            (self.cache.stack.clone(), item.type_()),
+                        );
+                    }
+                }
+            }
+            clean::PrimitiveItem(..) => {
+                self.cache
+                    .paths
+                    .insert(item.item_id.expect_def_id(), (self.cache.stack.clone(), item.type_()));
+            }
+
+            clean::ExternCrateItem { .. }
+            | clean::ImportItem(..)
+            | clean::OpaqueTyItem(..)
+            | clean::ImplItem(..)
+            | clean::TyMethodItem(..)
+            | clean::MethodItem(..)
+            | clean::StructFieldItem(..)
+            | clean::TyAssocConstItem(..)
+            | clean::AssocConstItem(..)
+            | clean::TyAssocTypeItem(..)
+            | clean::AssocTypeItem(..)
+            | clean::StrippedItem(..)
+            | clean::KeywordItem => {
+                // FIXME: Do these need handling?
+                // The person writing this comment doesn't know.
+                // So would rather leave them to an expert,
+                // as at least the list is better than `_ => {}`.
+            }
+        }
+
+        // Maintain the parent stack.
+        let (item, parent_pushed) = match *item.kind {
+            clean::TraitItem(..)
+            | clean::EnumItem(..)
+            | clean::ForeignTypeItem
+            | clean::StructItem(..)
+            | clean::UnionItem(..)
+            | clean::VariantItem(..)
+            | clean::ImplItem(..) => {
+                self.cache.parent_stack.push(ParentStackItem::new(&item));
+                (self.fold_item_recur(item), true)
+            }
+            _ => (self.fold_item_recur(item), false),
+        };
+
+        // Once we've recursively found all the generics, hoard off all the
+        // implementations elsewhere.
+        let ret = if let clean::Item { kind: box clean::ImplItem(ref i), .. } = item {
+            // Figure out the id of this impl. This may map to a
+            // primitive rather than always to a struct/enum.
+            // Note: matching twice to restrict the lifetime of the `i` borrow.
+            let mut dids = FxHashSet::default();
+            match i.for_ {
+                clean::Type::Path { ref path }
+                | clean::BorrowedRef { type_: box clean::Type::Path { ref path }, .. } => {
+                    dids.insert(path.def_id());
+                    if let Some(generics) = path.generics() &&
+                        let ty::Adt(adt, _) = self.tcx.type_of(path.def_id()).kind() &&
+                        adt.is_fundamental() {
+                        for ty in generics {
+                            if let Some(did) = ty.def_id(self.cache) {
+                                dids.insert(did);
+                            }
+                        }
+                    }
+                }
+                clean::DynTrait(ref bounds, _)
+                | clean::BorrowedRef { type_: box clean::DynTrait(ref bounds, _), .. } => {
+                    dids.insert(bounds[0].trait_.def_id());
+                }
+                ref t => {
+                    let did = t
+                        .primitive_type()
+                        .and_then(|t| self.cache.primitive_locations.get(&t).cloned());
+
+                    if let Some(did) = did {
+                        dids.insert(did);
+                    }
+                }
+            }
+
+            if let Some(generics) = i.trait_.as_ref().and_then(|t| t.generics()) {
+                for bound in generics {
+                    if let Some(did) = bound.def_id(self.cache) {
+                        dids.insert(did);
+                    }
+                }
+            }
+            let impl_item = Impl { impl_item: item };
+            if impl_item.trait_did().map_or(true, |d| self.cache.traits.contains_key(&d)) {
+                for did in dids {
+                    if self.impl_ids.entry(did).or_default().insert(impl_item.def_id()) {
+                        self.cache
+                            .impls
+                            .entry(did)
+                            .or_insert_with(Vec::new)
+                            .push(impl_item.clone());
+                    }
+                }
+            } else {
+                let trait_did = impl_item.trait_did().expect("no trait did");
+                self.cache.orphan_trait_impls.push((trait_did, dids, impl_item));
+            }
+            None
+        } else {
+            Some(item)
+        };
+
+        if pushed {
+            self.cache.stack.pop().expect("stack already empty");
+        }
+        if parent_pushed {
+            self.cache.parent_stack.pop().expect("parent stack already empty");
+        }
+        self.cache.stripped_mod = orig_stripped_mod;
+        ret
+    }
+}
+
+pub(crate) struct OrphanImplItem {
+    pub(crate) parent: DefId,
+    pub(crate) item: clean::Item,
+    pub(crate) impl_generics: Option<(clean::Type, clean::Generics)>,
+}
+
+/// Information about trait and type parents is tracked while traversing the item tree to build
+/// the cache.
+///
+/// We don't just store `Item` in there, because `Item` contains the list of children being
+/// traversed and it would be wasteful to clone all that. We also need the item id, so just
+/// storing `ItemKind` won't work, either.
+enum ParentStackItem {
+    Impl {
+        for_: clean::Type,
+        trait_: Option<clean::Path>,
+        generics: clean::Generics,
+        kind: clean::ImplKind,
+        item_id: ItemId,
+    },
+    Type(ItemId),
+}
+
+impl ParentStackItem {
+    fn new(item: &clean::Item) -> Self {
+        match &*item.kind {
+            clean::ItemKind::ImplItem(box clean::Impl { for_, trait_, generics, kind, .. }) => {
+                ParentStackItem::Impl {
+                    for_: for_.clone(),
+                    trait_: trait_.clone(),
+                    generics: generics.clone(),
+                    kind: kind.clone(),
+                    item_id: item.item_id,
+                }
+            }
+            _ => ParentStackItem::Type(item.item_id),
+        }
+    }
+    fn is_trait_impl(&self) -> bool {
+        matches!(self, ParentStackItem::Impl { trait_: Some(..), .. })
+    }
+    fn item_id(&self) -> ItemId {
+        match self {
+            ParentStackItem::Impl { item_id, .. } => *item_id,
+            ParentStackItem::Type(item_id) => *item_id,
+        }
+    }
+}
+
+fn clean_impl_generics(item: Option<&ParentStackItem>) -> Option<(clean::Type, clean::Generics)> {
+    if let Some(ParentStackItem::Impl { for_, generics, kind: clean::ImplKind::Normal, .. }) = item
+    {
+        Some((for_.clone(), generics.clone()))
+    } else {
+        None
+    }
+}
diff --git a/src/librustdoc/formats/item_type.rs b/src/librustdoc/formats/item_type.rs
new file mode 100644
index 000000000..0a7ee2005
--- /dev/null
+++ b/src/librustdoc/formats/item_type.rs
@@ -0,0 +1,185 @@
+//! Item types.
+
+use std::fmt;
+
+use serde::{Serialize, Serializer};
+
+use rustc_hir::def::DefKind;
+use rustc_span::hygiene::MacroKind;
+
+use crate::clean;
+
+/// Item type. Corresponds to `clean::ItemEnum` variants.
+///
+/// The search index uses item types encoded as smaller numbers which equal to
+/// discriminants. JavaScript then is used to decode them into the original value.
+/// Consequently, every change to this type should be synchronized to
+/// the `itemTypes` mapping table in `html/static/js/search.js`.
+///
+/// In addition, code in `html::render` uses this enum to generate CSS classes, page prefixes, and
+/// module headings. If you are adding to this enum and want to ensure that the sidebar also prints
+/// a heading, edit the listing in `html/render.rs`, function `sidebar_module`. This uses an
+/// ordering based on a helper function inside `item_module`, in the same file.
+#[derive(Copy, PartialEq, Eq, Hash, Clone, Debug, PartialOrd, Ord)]
+pub(crate) enum ItemType {
+    Module = 0,
+    ExternCrate = 1,
+    Import = 2,
+    Struct = 3,
+    Enum = 4,
+    Function = 5,
+    Typedef = 6,
+    Static = 7,
+    Trait = 8,
+    Impl = 9,
+    TyMethod = 10,
+    Method = 11,
+    StructField = 12,
+    Variant = 13,
+    Macro = 14,
+    Primitive = 15,
+    AssocType = 16,
+    Constant = 17,
+    AssocConst = 18,
+    Union = 19,
+    ForeignType = 20,
+    Keyword = 21,
+    OpaqueTy = 22,
+    ProcAttribute = 23,
+    ProcDerive = 24,
+    TraitAlias = 25,
+}
+
+impl Serialize for ItemType {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        (*self as u8).serialize(serializer)
+    }
+}
+
+impl<'a> From<&'a clean::Item> for ItemType {
+    fn from(item: &'a clean::Item) -> ItemType {
+        let kind = match *item.kind {
+            clean::StrippedItem(box ref item) => item,
+            ref kind => kind,
+        };
+
+        match *kind {
+            clean::ModuleItem(..) => ItemType::Module,
+            clean::ExternCrateItem { .. } => ItemType::ExternCrate,
+            clean::ImportItem(..) => ItemType::Import,
+            clean::StructItem(..) => ItemType::Struct,
+            clean::UnionItem(..) => ItemType::Union,
+            clean::EnumItem(..) => ItemType::Enum,
+            clean::FunctionItem(..) => ItemType::Function,
+            clean::TypedefItem(..) => ItemType::Typedef,
+            clean::OpaqueTyItem(..) => ItemType::OpaqueTy,
+            clean::StaticItem(..) => ItemType::Static,
+            clean::ConstantItem(..) => ItemType::Constant,
+            clean::TraitItem(..) => ItemType::Trait,
+            clean::ImplItem(..) => ItemType::Impl,
+            clean::TyMethodItem(..) => ItemType::TyMethod,
+            clean::MethodItem(..) => ItemType::Method,
+            clean::StructFieldItem(..) => ItemType::StructField,
+            clean::VariantItem(..) => ItemType::Variant,
+            clean::ForeignFunctionItem(..) => ItemType::Function, // no ForeignFunction
+            clean::ForeignStaticItem(..) => ItemType::Static,     // no ForeignStatic
+            clean::MacroItem(..) => ItemType::Macro,
+            clean::PrimitiveItem(..) => ItemType::Primitive,
+            clean::TyAssocConstItem(..) | clean::AssocConstItem(..) => ItemType::AssocConst,
+            clean::TyAssocTypeItem(..) | clean::AssocTypeItem(..) => ItemType::AssocType,
+            clean::ForeignTypeItem => ItemType::ForeignType,
+            clean::KeywordItem => ItemType::Keyword,
+            clean::TraitAliasItem(..) => ItemType::TraitAlias,
+            clean::ProcMacroItem(ref mac) => match mac.kind {
+                MacroKind::Bang => ItemType::Macro,
+                MacroKind::Attr => ItemType::ProcAttribute,
+                MacroKind::Derive => ItemType::ProcDerive,
+            },
+            clean::StrippedItem(..) => unreachable!(),
+        }
+    }
+}
+
+impl From<DefKind> for ItemType {
+    fn from(other: DefKind) -> Self {
+        match other {
+            DefKind::Enum => Self::Enum,
+            DefKind::Fn => Self::Function,
+            DefKind::Mod => Self::Module,
+            DefKind::Const => Self::Constant,
+            DefKind::Static(_) => Self::Static,
+            DefKind::Struct => Self::Struct,
+            DefKind::Union => Self::Union,
+            DefKind::Trait => Self::Trait,
+            DefKind::TyAlias => Self::Typedef,
+            DefKind::TraitAlias => Self::TraitAlias,
+            DefKind::Macro(kind) => match kind {
+                MacroKind::Bang => ItemType::Macro,
+                MacroKind::Attr => ItemType::ProcAttribute,
+                MacroKind::Derive => ItemType::ProcDerive,
+            },
+            DefKind::ForeignTy
+            | DefKind::Variant
+            | DefKind::AssocTy
+            | DefKind::TyParam
+            | DefKind::ConstParam
+            | DefKind::Ctor(..)
+            | DefKind::AssocFn
+            | DefKind::AssocConst
+            | DefKind::ExternCrate
+            | DefKind::Use
+            | DefKind::ForeignMod
+            | DefKind::AnonConst
+            | DefKind::InlineConst
+            | DefKind::OpaqueTy
+            | DefKind::Field
+            | DefKind::LifetimeParam
+            | DefKind::GlobalAsm
+            | DefKind::Impl
+            | DefKind::Closure
+            | DefKind::Generator => Self::ForeignType,
+        }
+    }
+}
+
+impl ItemType {
+    pub(crate) fn as_str(&self) -> &'static str {
+        match *self {
+            ItemType::Module => "mod",
+            ItemType::ExternCrate => "externcrate",
+            ItemType::Import => "import",
+            ItemType::Struct => "struct",
+            ItemType::Union => "union",
+            ItemType::Enum => "enum",
+            ItemType::Function => "fn",
+            ItemType::Typedef => "type",
+            ItemType::Static => "static",
+            ItemType::Trait => "trait",
+            ItemType::Impl => "impl",
+            ItemType::TyMethod => "tymethod",
+            ItemType::Method => "method",
+            ItemType::StructField => "structfield",
+            ItemType::Variant => "variant",
+            ItemType::Macro => "macro",
+            ItemType::Primitive => "primitive",
+            ItemType::AssocType => "associatedtype",
+            ItemType::Constant => "constant",
+            ItemType::AssocConst => "associatedconstant",
+            ItemType::ForeignType => "foreigntype",
+            ItemType::Keyword => "keyword",
+            ItemType::OpaqueTy => "opaque",
+            ItemType::ProcAttribute => "attr",
+            ItemType::ProcDerive => "derive",
+            ItemType::TraitAlias => "traitalias",
+        }
+    }
+}
+
+impl fmt::Display for ItemType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
diff --git a/src/librustdoc/formats/mod.rs b/src/librustdoc/formats/mod.rs
new file mode 100644
index 000000000..b236bd7be
--- /dev/null
+++ b/src/librustdoc/formats/mod.rs
@@ -0,0 +1,101 @@
+pub(crate) mod cache;
+pub(crate) mod item_type;
+pub(crate) mod renderer;
+
+use rustc_hir::def_id::DefId;
+
+pub(crate) use renderer::{run_format, FormatRenderer};
+
+use crate::clean::{self, ItemId};
+use crate::html::render::Context;
+
+/// Specifies whether rendering directly implemented trait items or ones from a certain Deref
+/// impl.
+pub(crate) enum AssocItemRender<'a> {
+    All,
+    DerefFor { trait_: &'a clean::Path, type_: &'a clean::Type, deref_mut_: bool },
+}
+
+/// For different handling of associated items from the Deref target of a type rather than the type
+/// itself.
+#[derive(Copy, Clone, PartialEq)]
+pub(crate) enum RenderMode {
+    Normal,
+    ForDeref { mut_: bool },
+}
+
+/// Metadata about implementations for a type or trait.
+#[derive(Clone, Debug)]
+pub(crate) struct Impl {
+    pub(crate) impl_item: clean::Item,
+}
+
+impl Impl {
+    pub(crate) fn inner_impl(&self) -> &clean::Impl {
+        match *self.impl_item.kind {
+            clean::ImplItem(ref impl_) => impl_,
+            _ => panic!("non-impl item found in impl"),
+        }
+    }
+
+    pub(crate) fn trait_did(&self) -> Option<DefId> {
+        self.inner_impl().trait_.as_ref().map(|t| t.def_id())
+    }
+
+    /// This function is used to extract a `DefId` to be used as a key for the `Cache::impls` field.
+    ///
+    /// It allows to prevent having duplicated implementations showing up (the biggest issue was
+    /// with blanket impls).
+    ///
+    /// It panics if `self` is a `ItemId::Primitive`.
+    pub(crate) fn def_id(&self) -> DefId {
+        match self.impl_item.item_id {
+            ItemId::Blanket { impl_id, .. } => impl_id,
+            ItemId::Auto { trait_, .. } => trait_,
+            ItemId::DefId(def_id) => def_id,
+            ItemId::Primitive(_, _) => {
+                panic!(
+                    "Unexpected ItemId::Primitive in expect_def_id: {:?}",
+                    self.impl_item.item_id
+                )
+            }
+        }
+    }
+
+    // Returns true if this is an implementation on a "local" type, meaning:
+    // the type is in the current crate, or the type and the trait are both
+    // re-exported by the current crate.
+    pub(crate) fn is_on_local_type(&self, cx: &Context<'_>) -> bool {
+        let cache = cx.cache();
+        let for_type = &self.inner_impl().for_;
+        if let Some(for_type_did) = for_type.def_id(cache) {
+            // The "for" type is local if it's in the paths for the current crate.
+            if cache.paths.contains_key(&for_type_did) {
+                return true;
+            }
+            if let Some(trait_did) = self.trait_did() {
+                // The "for" type and the trait are from the same crate. That could
+                // be different from the current crate, for instance when both were
+                // re-exported from some other crate. But they are local with respect to
+                // each other.
+                if for_type_did.krate == trait_did.krate {
+                    return true;
+                }
+                // Hack: many traits and types in std are re-exported from
+                // core or alloc. In general, rustdoc is capable of recognizing
+                // these implementations as being on local types. However, in at
+                // least one case (https://github.com/rust-lang/rust/issues/97610),
+                // rustdoc gets confused and labels an implementation as being on
+                // a foreign type. To make sure that confusion doesn't pass on to
+                // the reader, consider all implementations in std, core, and alloc
+                // to be on local types.
+                let crate_name = cx.tcx().crate_name(trait_did.krate);
+                if matches!(crate_name.as_str(), "std" | "core" | "alloc") {
+                    return true;
+                }
+            }
+            return false;
+        };
+        true
+    }
+}
diff --git a/src/librustdoc/formats/renderer.rs b/src/librustdoc/formats/renderer.rs
new file mode 100644
index 000000000..62ba984ac
--- /dev/null
+++ b/src/librustdoc/formats/renderer.rs
@@ -0,0 +1,97 @@
+use rustc_middle::ty::TyCtxt;
+use rustc_span::Symbol;
+
+use crate::clean;
+use crate::config::RenderOptions;
+use crate::error::Error;
+use crate::formats::cache::Cache;
+
+/// Allows for different backends to rustdoc to be used with the `run_format()` function. Each
+/// backend renderer has hooks for initialization, documenting an item, entering and exiting a
+/// module, and cleanup/finalizing output.
+pub(crate) trait FormatRenderer<'tcx>: Sized {
+    /// Gives a description of the renderer. Used for performance profiling.
+    fn descr() -> &'static str;
+
+    /// Whether to call `item` recursively for modules
+    ///
+    /// This is true for html, and false for json. See #80664
+    const RUN_ON_MODULE: bool;
+
+    /// Sets up any state required for the renderer. When this is called the cache has already been
+    /// populated.
+    fn init(
+        krate: clean::Crate,
+        options: RenderOptions,
+        cache: Cache,
+        tcx: TyCtxt<'tcx>,
+    ) -> Result<(Self, clean::Crate), Error>;
+
+    /// Make a new renderer to render a child of the item currently being rendered.
+    fn make_child_renderer(&self) -> Self;
+
+    /// Renders a single non-module item. This means no recursive sub-item rendering is required.
+    fn item(&mut self, item: clean::Item) -> Result<(), Error>;
+
+    /// Renders a module (should not handle recursing into children).
+    fn mod_item_in(&mut self, item: &clean::Item) -> Result<(), Error>;
+
+    /// Runs after recursively rendering all sub-items of a module.
+    fn mod_item_out(&mut self) -> Result<(), Error> {
+        Ok(())
+    }
+
+    /// Post processing hook for cleanup and dumping output to files.
+    fn after_krate(&mut self) -> Result<(), Error>;
+
+    fn cache(&self) -> &Cache;
+}
+
+/// Main method for rendering a crate.
+pub(crate) fn run_format<'tcx, T: FormatRenderer<'tcx>>(
+    krate: clean::Crate,
+    options: RenderOptions,
+    cache: Cache,
+    tcx: TyCtxt<'tcx>,
+) -> Result<(), Error> {
+    let prof = &tcx.sess.prof;
+
+    let emit_crate = options.should_emit_crate();
+    let (mut format_renderer, krate) = prof
+        .extra_verbose_generic_activity("create_renderer", T::descr())
+        .run(|| T::init(krate, options, cache, tcx))?;
+
+    if !emit_crate {
+        return Ok(());
+    }
+
+    // Render the crate documentation
+    let mut work = vec![(format_renderer.make_child_renderer(), krate.module)];
+
+    let unknown = Symbol::intern("<unknown item>");
+    while let Some((mut cx, item)) = work.pop() {
+        if item.is_mod() && T::RUN_ON_MODULE {
+            // modules are special because they add a namespace. We also need to
+            // recurse into the items of the module as well.
+            let _timer =
+                prof.generic_activity_with_arg("render_mod_item", item.name.unwrap().to_string());
+
+            cx.mod_item_in(&item)?;
+            let (clean::StrippedItem(box clean::ModuleItem(module)) | clean::ModuleItem(module)) = *item.kind
+            else { unreachable!() };
+            for it in module.items {
+                debug!("Adding {:?} to worklist", it.name);
+                work.push((cx.make_child_renderer(), it));
+            }
+
+            cx.mod_item_out()?;
+        // FIXME: checking `item.name.is_some()` is very implicit and leads to lots of special
+        // cases. Use an explicit match instead.
+        } else if item.name.is_some() && !item.is_extern_crate() {
+            prof.generic_activity_with_arg("render_item", item.name.unwrap_or(unknown).as_str())
+                .run(|| cx.item(item))?;
+        }
+    }
+    prof.extra_verbose_generic_activity("renderer_after_krate", T::descr())
+        .run(|| format_renderer.after_krate())
+}
diff --git a/src/librustdoc/html/escape.rs b/src/librustdoc/html/escape.rs
new file mode 100644
index 000000000..4a19d0a44
--- /dev/null
+++ b/src/librustdoc/html/escape.rs
@@ -0,0 +1,40 @@
+//! HTML escaping.
+//!
+//! This module contains one unit struct, which can be used to HTML-escape a
+//! string of text (for use in a format string).
+
+use std::fmt;
+
+/// Wrapper struct which will emit the HTML-escaped version of the contained
+/// string when passed to a format string.
+pub(crate) struct Escape<'a>(pub &'a str);
+
+impl<'a> fmt::Display for Escape<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Because the internet is always right, turns out there's not that many
+        // characters to escape: http://stackoverflow.com/questions/7381974
+        let Escape(s) = *self;
+        let pile_o_bits = s;
+        let mut last = 0;
+        for (i, ch) in s.char_indices() {
+            let s = match ch {
+                '>' => "&gt;",
+                '<' => "&lt;",
+                '&' => "&amp;",
+                '\'' => "&#39;",
+                '"' => "&quot;",
+                _ => continue,
+            };
+            fmt.write_str(&pile_o_bits[last..i])?;
+            fmt.write_str(s)?;
+            // NOTE: we only expect single byte characters here - which is fine as long as we
+            // only match single byte characters
+            last = i + 1;
+        }
+
+        if last < s.len() {
+            fmt.write_str(&pile_o_bits[last..])?;
+        }
+        Ok(())
+    }
+}
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
new file mode 100644
index 000000000..36a47b05c
--- /dev/null
+++ b/src/librustdoc/html/format.rs
@@ -0,0 +1,1688 @@
+//! HTML formatting module
+//!
+//! This module contains a large number of `fmt::Display` implementations for
+//! various types in `rustdoc::clean`. These implementations all currently
+//! assume that HTML output is desired, although it may be possible to redesign
+//! them in the future to instead emit any format desired.
+
+use std::borrow::Cow;
+use std::cell::Cell;
+use std::fmt;
+use std::iter::{self, once};
+
+use rustc_ast as ast;
+use rustc_attr::{ConstStability, StabilityLevel};
+use rustc_data_structures::captures::Captures;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_hir as hir;
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::DefId;
+use rustc_metadata::creader::{CStore, LoadedMacro};
+use rustc_middle::ty;
+use rustc_middle::ty::DefIdTree;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::symbol::kw;
+use rustc_span::{sym, Symbol};
+use rustc_target::spec::abi::Abi;
+
+use itertools::Itertools;
+
+use crate::clean::{
+    self, types::ExternalLocation, utils::find_nearest_parent_module, ExternalCrate, ItemId,
+    PrimitiveType,
+};
+use crate::formats::item_type::ItemType;
+use crate::html::escape::Escape;
+use crate::html::render::Context;
+
+use super::url_parts_builder::estimate_item_path_byte_length;
+use super::url_parts_builder::UrlPartsBuilder;
+
+pub(crate) trait Print {
+    fn print(self, buffer: &mut Buffer);
+}
+
+impl<F> Print for F
+where
+    F: FnOnce(&mut Buffer),
+{
+    fn print(self, buffer: &mut Buffer) {
+        (self)(buffer)
+    }
+}
+
+impl Print for String {
+    fn print(self, buffer: &mut Buffer) {
+        buffer.write_str(&self);
+    }
+}
+
+impl Print for &'_ str {
+    fn print(self, buffer: &mut Buffer) {
+        buffer.write_str(self);
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct Buffer {
+    for_html: bool,
+    buffer: String,
+}
+
+impl core::fmt::Write for Buffer {
+    #[inline]
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.buffer.write_str(s)
+    }
+
+    #[inline]
+    fn write_char(&mut self, c: char) -> fmt::Result {
+        self.buffer.write_char(c)
+    }
+
+    #[inline]
+    fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> fmt::Result {
+        self.buffer.write_fmt(args)
+    }
+}
+
+impl Buffer {
+    pub(crate) fn empty_from(v: &Buffer) -> Buffer {
+        Buffer { for_html: v.for_html, buffer: String::new() }
+    }
+
+    pub(crate) fn html() -> Buffer {
+        Buffer { for_html: true, buffer: String::new() }
+    }
+
+    pub(crate) fn new() -> Buffer {
+        Buffer { for_html: false, buffer: String::new() }
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        self.buffer.is_empty()
+    }
+
+    pub(crate) fn into_inner(self) -> String {
+        self.buffer
+    }
+
+    pub(crate) fn insert_str(&mut self, idx: usize, s: &str) {
+        self.buffer.insert_str(idx, s);
+    }
+
+    pub(crate) fn push_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    pub(crate) fn push_buffer(&mut self, other: Buffer) {
+        self.buffer.push_str(&other.buffer);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    pub(crate) fn write_str(&mut self, s: &str) {
+        self.buffer.push_str(s);
+    }
+
+    // Intended for consumption by write! and writeln! (std::fmt) but without
+    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
+    // import).
+    pub(crate) fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
+        use fmt::Write;
+        self.buffer.write_fmt(v).unwrap();
+    }
+
+    pub(crate) fn to_display<T: Print>(mut self, t: T) -> String {
+        t.print(&mut self);
+        self.into_inner()
+    }
+
+    pub(crate) fn is_for_html(&self) -> bool {
+        self.for_html
+    }
+
+    pub(crate) fn reserve(&mut self, additional: usize) {
+        self.buffer.reserve(additional)
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.buffer.len()
+    }
+}
+
+fn comma_sep<T: fmt::Display>(
+    items: impl Iterator<Item = T>,
+    space_after_comma: bool,
+) -> impl fmt::Display {
+    display_fn(move |f| {
+        for (i, item) in items.enumerate() {
+            if i != 0 {
+                write!(f, ",{}", if space_after_comma { " " } else { "" })?;
+            }
+            fmt::Display::fmt(&item, f)?;
+        }
+        Ok(())
+    })
+}
+
+pub(crate) fn print_generic_bounds<'a, 'tcx: 'a>(
+    bounds: &'a [clean::GenericBound],
+    cx: &'a Context<'tcx>,
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    display_fn(move |f| {
+        let mut bounds_dup = FxHashSet::default();
+
+        for (i, bound) in bounds.iter().filter(|b| bounds_dup.insert(b.clone())).enumerate() {
+            if i > 0 {
+                f.write_str(" + ")?;
+            }
+            fmt::Display::fmt(&bound.print(cx), f)?;
+        }
+        Ok(())
+    })
+}
+
+impl clean::GenericParamDef {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match &self.kind {
+            clean::GenericParamDefKind::Lifetime { outlives } => {
+                write!(f, "{}", self.name)?;
+
+                if !outlives.is_empty() {
+                    f.write_str(": ")?;
+                    for (i, lt) in outlives.iter().enumerate() {
+                        if i != 0 {
+                            f.write_str(" + ")?;
+                        }
+                        write!(f, "{}", lt.print())?;
+                    }
+                }
+
+                Ok(())
+            }
+            clean::GenericParamDefKind::Type { bounds, default, .. } => {
+                f.write_str(self.name.as_str())?;
+
+                if !bounds.is_empty() {
+                    if f.alternate() {
+                        write!(f, ": {:#}", print_generic_bounds(bounds, cx))?;
+                    } else {
+                        write!(f, ":&nbsp;{}", print_generic_bounds(bounds, cx))?;
+                    }
+                }
+
+                if let Some(ref ty) = default {
+                    if f.alternate() {
+                        write!(f, " = {:#}", ty.print(cx))?;
+                    } else {
+                        write!(f, "&nbsp;=&nbsp;{}", ty.print(cx))?;
+                    }
+                }
+
+                Ok(())
+            }
+            clean::GenericParamDefKind::Const { ty, default, .. } => {
+                if f.alternate() {
+                    write!(f, "const {}: {:#}", self.name, ty.print(cx))?;
+                } else {
+                    write!(f, "const {}:&nbsp;{}", self.name, ty.print(cx))?;
+                }
+
+                if let Some(default) = default {
+                    if f.alternate() {
+                        write!(f, " = {:#}", default)?;
+                    } else {
+                        write!(f, "&nbsp;=&nbsp;{}", default)?;
+                    }
+                }
+
+                Ok(())
+            }
+        })
+    }
+}
+
+impl clean::Generics {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            let mut real_params =
+                self.params.iter().filter(|p| !p.is_synthetic_type_param()).peekable();
+            if real_params.peek().is_none() {
+                return Ok(());
+            }
+
+            if f.alternate() {
+                write!(f, "<{:#}>", comma_sep(real_params.map(|g| g.print(cx)), true))
+            } else {
+                write!(f, "&lt;{}&gt;", comma_sep(real_params.map(|g| g.print(cx)), true))
+            }
+        })
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub(crate) enum Ending {
+    Newline,
+    NoNewline,
+}
+
+/// * The Generics from which to emit a where-clause.
+/// * The number of spaces to indent each line with.
+/// * Whether the where-clause needs to add a comma and newline after the last bound.
+pub(crate) fn print_where_clause<'a, 'tcx: 'a>(
+    gens: &'a clean::Generics,
+    cx: &'a Context<'tcx>,
+    indent: usize,
+    ending: Ending,
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    use fmt::Write;
+
+    display_fn(move |f| {
+        let mut where_predicates = gens.where_predicates.iter().filter(|pred| {
+            !matches!(pred, clean::WherePredicate::BoundPredicate { bounds, .. } if bounds.is_empty())
+        }).map(|pred| {
+            display_fn(move |f| {
+                if f.alternate() {
+                    f.write_str(" ")?;
+                } else {
+                    f.write_str("<br>")?;
+                }
+
+                match pred {
+                    clean::WherePredicate::BoundPredicate { ty, bounds, bound_params } => {
+                        let ty_cx = ty.print(cx);
+                        let generic_bounds = print_generic_bounds(bounds, cx);
+
+                        if bound_params.is_empty() {
+                            if f.alternate() {
+                                write!(f, "{ty_cx:#}: {generic_bounds:#}")
+                            } else {
+                                write!(f, "{ty_cx}: {generic_bounds}")
+                            }
+                        } else {
+                            if f.alternate() {
+                                write!(
+                                    f,
+                                    "for<{:#}> {ty_cx:#}: {generic_bounds:#}",
+                                    comma_sep(bound_params.iter().map(|lt| lt.print()), true)
+                                )
+                            } else {
+                                write!(
+                                    f,
+                                    "for&lt;{}&gt; {ty_cx}: {generic_bounds}",
+                                    comma_sep(bound_params.iter().map(|lt| lt.print()), true)
+                                )
+                            }
+                        }
+                    }
+                    clean::WherePredicate::RegionPredicate { lifetime, bounds } => {
+                        let mut bounds_display = String::new();
+                        for bound in bounds.iter().map(|b| b.print(cx)) {
+                            write!(bounds_display, "{bound} + ")?;
+                        }
+                        bounds_display.truncate(bounds_display.len() - " + ".len());
+                        write!(f, "{}: {bounds_display}", lifetime.print())
+                    }
+                    clean::WherePredicate::EqPredicate { lhs, rhs } => {
+                        if f.alternate() {
+                            write!(f, "{:#} == {:#}", lhs.print(cx), rhs.print(cx))
+                        } else {
+                            write!(f, "{} == {}", lhs.print(cx), rhs.print(cx))
+                        }
+                    }
+                }
+            })
+        }).peekable();
+
+        if where_predicates.peek().is_none() {
+            return Ok(());
+        }
+
+        let where_preds = comma_sep(where_predicates, false);
+        let clause = if f.alternate() {
+            if ending == Ending::Newline {
+                // add a space so stripping <br> tags and breaking spaces still renders properly
+                format!(" where{where_preds}, ")
+            } else {
+                format!(" where{where_preds}")
+            }
+        } else {
+            let mut br_with_padding = String::with_capacity(6 * indent + 28);
+            br_with_padding.push_str("<br>");
+            for _ in 0..indent + 4 {
+                br_with_padding.push_str("&nbsp;");
+            }
+            let where_preds = where_preds.to_string().replace("<br>", &br_with_padding);
+
+            if ending == Ending::Newline {
+                let mut clause = "&nbsp;".repeat(indent.saturating_sub(1));
+                // add a space so stripping <br> tags and breaking spaces still renders properly
+                write!(
+                    clause,
+                    " <span class=\"where fmt-newline\">where{where_preds},&nbsp;</span>"
+                )?;
+                clause
+            } else {
+                // insert a <br> tag after a single space but before multiple spaces at the start
+                if indent == 0 {
+                    format!(" <br><span class=\"where\">where{where_preds}</span>")
+                } else {
+                    let mut clause = br_with_padding;
+                    clause.truncate(clause.len() - 5 * "&nbsp;".len());
+                    write!(clause, " <span class=\"where\">where{where_preds}</span>")?;
+                    clause
+                }
+            }
+        };
+        write!(f, "{clause}")
+    })
+}
+
+impl clean::Lifetime {
+    pub(crate) fn print(&self) -> impl fmt::Display + '_ {
+        self.0.as_str()
+    }
+}
+
+impl clean::Constant {
+    pub(crate) fn print(&self, tcx: TyCtxt<'_>) -> impl fmt::Display + '_ {
+        let expr = self.expr(tcx);
+        display_fn(
+            move |f| {
+                if f.alternate() { f.write_str(&expr) } else { write!(f, "{}", Escape(&expr)) }
+            },
+        )
+    }
+}
+
+impl clean::PolyTrait {
+    fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            if !self.generic_params.is_empty() {
+                if f.alternate() {
+                    write!(
+                        f,
+                        "for<{:#}> ",
+                        comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
+                    )?;
+                } else {
+                    write!(
+                        f,
+                        "for&lt;{}&gt; ",
+                        comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
+                    )?;
+                }
+            }
+            if f.alternate() {
+                write!(f, "{:#}", self.trait_.print(cx))
+            } else {
+                write!(f, "{}", self.trait_.print(cx))
+            }
+        })
+    }
+}
+
+impl clean::GenericBound {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match self {
+            clean::GenericBound::Outlives(lt) => write!(f, "{}", lt.print()),
+            clean::GenericBound::TraitBound(ty, modifier) => {
+                let modifier_str = match modifier {
+                    hir::TraitBoundModifier::None => "",
+                    hir::TraitBoundModifier::Maybe => "?",
+                    // ~const is experimental; do not display those bounds in rustdoc
+                    hir::TraitBoundModifier::MaybeConst => "",
+                };
+                if f.alternate() {
+                    write!(f, "{}{:#}", modifier_str, ty.print(cx))
+                } else {
+                    write!(f, "{}{}", modifier_str, ty.print(cx))
+                }
+            }
+        })
+    }
+}
+
+impl clean::GenericArgs {
+    fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            match self {
+                clean::GenericArgs::AngleBracketed { args, bindings } => {
+                    if !args.is_empty() || !bindings.is_empty() {
+                        if f.alternate() {
+                            f.write_str("<")?;
+                        } else {
+                            f.write_str("&lt;")?;
+                        }
+                        let mut comma = false;
+                        for arg in args.iter() {
+                            if comma {
+                                f.write_str(", ")?;
+                            }
+                            comma = true;
+                            if f.alternate() {
+                                write!(f, "{:#}", arg.print(cx))?;
+                            } else {
+                                write!(f, "{}", arg.print(cx))?;
+                            }
+                        }
+                        for binding in bindings.iter() {
+                            if comma {
+                                f.write_str(", ")?;
+                            }
+                            comma = true;
+                            if f.alternate() {
+                                write!(f, "{:#}", binding.print(cx))?;
+                            } else {
+                                write!(f, "{}", binding.print(cx))?;
+                            }
+                        }
+                        if f.alternate() {
+                            f.write_str(">")?;
+                        } else {
+                            f.write_str("&gt;")?;
+                        }
+                    }
+                }
+                clean::GenericArgs::Parenthesized { inputs, output } => {
+                    f.write_str("(")?;
+                    let mut comma = false;
+                    for ty in inputs.iter() {
+                        if comma {
+                            f.write_str(", ")?;
+                        }
+                        comma = true;
+                        if f.alternate() {
+                            write!(f, "{:#}", ty.print(cx))?;
+                        } else {
+                            write!(f, "{}", ty.print(cx))?;
+                        }
+                    }
+                    f.write_str(")")?;
+                    if let Some(ref ty) = *output {
+                        if f.alternate() {
+                            write!(f, " -> {:#}", ty.print(cx))?;
+                        } else {
+                            write!(f, " -&gt; {}", ty.print(cx))?;
+                        }
+                    }
+                }
+            }
+            Ok(())
+        })
+    }
+}
+
+// Possible errors when computing href link source for a `DefId`
+#[derive(PartialEq, Eq)]
+pub(crate) enum HrefError {
+    /// This item is known to rustdoc, but from a crate that does not have documentation generated.
+    ///
+    /// This can only happen for non-local items.
+    ///
+    /// # Example
+    ///
+    /// Crate `a` defines a public trait and crate `b` – the target crate that depends on `a` –
+    /// implements it for a local type.
+    /// We document `b` but **not** `a` (we only _build_ the latter – with `rustc`):
+    ///
+    /// ```sh
+    /// rustc a.rs --crate-type=lib
+    /// rustdoc b.rs --crate-type=lib --extern=a=liba.rlib
+    /// ```
+    ///
+    /// Now, the associated items in the trait impl want to link to the corresponding item in the
+    /// trait declaration (see `html::render::assoc_href_attr`) but it's not available since their
+    /// *documentation (was) not built*.
+    DocumentationNotBuilt,
+    /// This can only happen for non-local items when `--document-private-items` is not passed.
+    Private,
+    // Not in external cache, href link should be in same page
+    NotInExternalCache,
+}
+
+// Panics if `syms` is empty.
+pub(crate) fn join_with_double_colon(syms: &[Symbol]) -> String {
+    let mut s = String::with_capacity(estimate_item_path_byte_length(syms.len()));
+    s.push_str(syms[0].as_str());
+    for sym in &syms[1..] {
+        s.push_str("::");
+        s.push_str(sym.as_str());
+    }
+    s
+}
+
+/// This function is to get the external macro path because they are not in the cache used in
+/// `href_with_root_path`.
+fn generate_macro_def_id_path(
+    def_id: DefId,
+    cx: &Context<'_>,
+    root_path: Option<&str>,
+) -> Result<(String, ItemType, Vec<Symbol>), HrefError> {
+    let tcx = cx.shared.tcx;
+    let crate_name = tcx.crate_name(def_id.krate).to_string();
+    let cache = cx.cache();
+
+    let fqp: Vec<Symbol> = tcx
+        .def_path(def_id)
+        .data
+        .into_iter()
+        .filter_map(|elem| {
+            // extern blocks (and a few others things) have an empty name.
+            match elem.data.get_opt_name() {
+                Some(s) if !s.is_empty() => Some(s),
+                _ => None,
+            }
+        })
+        .collect();
+    let relative = fqp.iter().map(|elem| elem.to_string());
+    let cstore = CStore::from_tcx(tcx);
+    // We need this to prevent a `panic` when this function is used from intra doc links...
+    if !cstore.has_crate_data(def_id.krate) {
+        debug!("No data for crate {}", crate_name);
+        return Err(HrefError::NotInExternalCache);
+    }
+    // Check to see if it is a macro 2.0 or built-in macro.
+    // More information in <https://rust-lang.github.io/rfcs/1584-macros.html>.
+    let is_macro_2 = match cstore.load_macro_untracked(def_id, tcx.sess) {
+        LoadedMacro::MacroDef(def, _) => {
+            // If `ast_def.macro_rules` is `true`, then it's not a macro 2.0.
+            matches!(&def.kind, ast::ItemKind::MacroDef(ast_def) if !ast_def.macro_rules)
+        }
+        _ => false,
+    };
+
+    let mut path = if is_macro_2 {
+        once(crate_name.clone()).chain(relative).collect()
+    } else {
+        vec![crate_name.clone(), relative.last().unwrap()]
+    };
+    if path.len() < 2 {
+        // The minimum we can have is the crate name followed by the macro name. If shorter, then
+        // it means that that `relative` was empty, which is an error.
+        debug!("macro path cannot be empty!");
+        return Err(HrefError::NotInExternalCache);
+    }
+
+    if let Some(last) = path.last_mut() {
+        *last = format!("macro.{}.html", last);
+    }
+
+    let url = match cache.extern_locations[&def_id.krate] {
+        ExternalLocation::Remote(ref s) => {
+            // `ExternalLocation::Remote` always end with a `/`.
+            format!("{}{}", s, path.join("/"))
+        }
+        ExternalLocation::Local => {
+            // `root_path` always end with a `/`.
+            format!("{}{}/{}", root_path.unwrap_or(""), crate_name, path.join("/"))
+        }
+        ExternalLocation::Unknown => {
+            debug!("crate {} not in cache when linkifying macros", crate_name);
+            return Err(HrefError::NotInExternalCache);
+        }
+    };
+    Ok((url, ItemType::Macro, fqp))
+}
+
+pub(crate) fn href_with_root_path(
+    did: DefId,
+    cx: &Context<'_>,
+    root_path: Option<&str>,
+) -> Result<(String, ItemType, Vec<Symbol>), HrefError> {
+    let tcx = cx.tcx();
+    let def_kind = tcx.def_kind(did);
+    let did = match def_kind {
+        DefKind::AssocTy | DefKind::AssocFn | DefKind::AssocConst | DefKind::Variant => {
+            // documented on their parent's page
+            tcx.parent(did)
+        }
+        _ => did,
+    };
+    let cache = cx.cache();
+    let relative_to = &cx.current;
+    fn to_module_fqp(shortty: ItemType, fqp: &[Symbol]) -> &[Symbol] {
+        if shortty == ItemType::Module { fqp } else { &fqp[..fqp.len() - 1] }
+    }
+
+    if !did.is_local()
+        && !cache.access_levels.is_public(did)
+        && !cache.document_private
+        && !cache.primitive_locations.values().any(|&id| id == did)
+    {
+        return Err(HrefError::Private);
+    }
+
+    let mut is_remote = false;
+    let (fqp, shortty, mut url_parts) = match cache.paths.get(&did) {
+        Some(&(ref fqp, shortty)) => (fqp, shortty, {
+            let module_fqp = to_module_fqp(shortty, fqp.as_slice());
+            debug!(?fqp, ?shortty, ?module_fqp);
+            href_relative_parts(module_fqp, relative_to).collect()
+        }),
+        None => {
+            if let Some(&(ref fqp, shortty)) = cache.external_paths.get(&did) {
+                let module_fqp = to_module_fqp(shortty, fqp);
+                (
+                    fqp,
+                    shortty,
+                    match cache.extern_locations[&did.krate] {
+                        ExternalLocation::Remote(ref s) => {
+                            is_remote = true;
+                            let s = s.trim_end_matches('/');
+                            let mut builder = UrlPartsBuilder::singleton(s);
+                            builder.extend(module_fqp.iter().copied());
+                            builder
+                        }
+                        ExternalLocation::Local => {
+                            href_relative_parts(module_fqp, relative_to).collect()
+                        }
+                        ExternalLocation::Unknown => return Err(HrefError::DocumentationNotBuilt),
+                    },
+                )
+            } else if matches!(def_kind, DefKind::Macro(_)) {
+                return generate_macro_def_id_path(did, cx, root_path);
+            } else {
+                return Err(HrefError::NotInExternalCache);
+            }
+        }
+    };
+    if !is_remote {
+        if let Some(root_path) = root_path {
+            let root = root_path.trim_end_matches('/');
+            url_parts.push_front(root);
+        }
+    }
+    debug!(?url_parts);
+    match shortty {
+        ItemType::Module => {
+            url_parts.push("index.html");
+        }
+        _ => {
+            let prefix = shortty.as_str();
+            let last = fqp.last().unwrap();
+            url_parts.push_fmt(format_args!("{}.{}.html", prefix, last));
+        }
+    }
+    Ok((url_parts.finish(), shortty, fqp.to_vec()))
+}
+
+pub(crate) fn href(
+    did: DefId,
+    cx: &Context<'_>,
+) -> Result<(String, ItemType, Vec<Symbol>), HrefError> {
+    href_with_root_path(did, cx, None)
+}
+
+/// Both paths should only be modules.
+/// This is because modules get their own directories; that is, `std::vec` and `std::vec::Vec` will
+/// both need `../iter/trait.Iterator.html` to get at the iterator trait.
+pub(crate) fn href_relative_parts<'fqp>(
+    fqp: &'fqp [Symbol],
+    relative_to_fqp: &[Symbol],
+) -> Box<dyn Iterator<Item = Symbol> + 'fqp> {
+    for (i, (f, r)) in fqp.iter().zip(relative_to_fqp.iter()).enumerate() {
+        // e.g. linking to std::iter from std::vec (`dissimilar_part_count` will be 1)
+        if f != r {
+            let dissimilar_part_count = relative_to_fqp.len() - i;
+            let fqp_module = &fqp[i..fqp.len()];
+            return Box::new(
+                iter::repeat(sym::dotdot)
+                    .take(dissimilar_part_count)
+                    .chain(fqp_module.iter().copied()),
+            );
+        }
+    }
+    // e.g. linking to std::sync::atomic from std::sync
+    if relative_to_fqp.len() < fqp.len() {
+        Box::new(fqp[relative_to_fqp.len()..fqp.len()].iter().copied())
+    // e.g. linking to std::sync from std::sync::atomic
+    } else if fqp.len() < relative_to_fqp.len() {
+        let dissimilar_part_count = relative_to_fqp.len() - fqp.len();
+        Box::new(iter::repeat(sym::dotdot).take(dissimilar_part_count))
+    // linking to the same module
+    } else {
+        Box::new(iter::empty())
+    }
+}
+
+/// Used to render a [`clean::Path`].
+fn resolved_path<'cx>(
+    w: &mut fmt::Formatter<'_>,
+    did: DefId,
+    path: &clean::Path,
+    print_all: bool,
+    use_absolute: bool,
+    cx: &'cx Context<'_>,
+) -> fmt::Result {
+    let last = path.segments.last().unwrap();
+
+    if print_all {
+        for seg in &path.segments[..path.segments.len() - 1] {
+            write!(w, "{}::", if seg.name == kw::PathRoot { "" } else { seg.name.as_str() })?;
+        }
+    }
+    if w.alternate() {
+        write!(w, "{}{:#}", &last.name, last.args.print(cx))?;
+    } else {
+        let path = if use_absolute {
+            if let Ok((_, _, fqp)) = href(did, cx) {
+                format!(
+                    "{}::{}",
+                    join_with_double_colon(&fqp[..fqp.len() - 1]),
+                    anchor(did, *fqp.last().unwrap(), cx)
+                )
+            } else {
+                last.name.to_string()
+            }
+        } else {
+            anchor(did, last.name, cx).to_string()
+        };
+        write!(w, "{}{}", path, last.args.print(cx))?;
+    }
+    Ok(())
+}
+
+fn primitive_link(
+    f: &mut fmt::Formatter<'_>,
+    prim: clean::PrimitiveType,
+    name: &str,
+    cx: &Context<'_>,
+) -> fmt::Result {
+    primitive_link_fragment(f, prim, name, "", cx)
+}
+
+fn primitive_link_fragment(
+    f: &mut fmt::Formatter<'_>,
+    prim: clean::PrimitiveType,
+    name: &str,
+    fragment: &str,
+    cx: &Context<'_>,
+) -> fmt::Result {
+    let m = &cx.cache();
+    let mut needs_termination = false;
+    if !f.alternate() {
+        match m.primitive_locations.get(&prim) {
+            Some(&def_id) if def_id.is_local() => {
+                let len = cx.current.len();
+                let len = if len == 0 { 0 } else { len - 1 };
+                write!(
+                    f,
+                    "<a class=\"primitive\" href=\"{}primitive.{}.html{fragment}\">",
+                    "../".repeat(len),
+                    prim.as_sym()
+                )?;
+                needs_termination = true;
+            }
+            Some(&def_id) => {
+                let loc = match m.extern_locations[&def_id.krate] {
+                    ExternalLocation::Remote(ref s) => {
+                        let cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
+                        let builder: UrlPartsBuilder =
+                            [s.as_str().trim_end_matches('/'), cname_sym.as_str()]
+                                .into_iter()
+                                .collect();
+                        Some(builder)
+                    }
+                    ExternalLocation::Local => {
+                        let cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
+                        Some(if cx.current.first() == Some(&cname_sym) {
+                            iter::repeat(sym::dotdot).take(cx.current.len() - 1).collect()
+                        } else {
+                            iter::repeat(sym::dotdot)
+                                .take(cx.current.len())
+                                .chain(iter::once(cname_sym))
+                                .collect()
+                        })
+                    }
+                    ExternalLocation::Unknown => None,
+                };
+                if let Some(mut loc) = loc {
+                    loc.push_fmt(format_args!("primitive.{}.html", prim.as_sym()));
+                    write!(f, "<a class=\"primitive\" href=\"{}{fragment}\">", loc.finish())?;
+                    needs_termination = true;
+                }
+            }
+            None => {}
+        }
+    }
+    write!(f, "{}", name)?;
+    if needs_termination {
+        write!(f, "</a>")?;
+    }
+    Ok(())
+}
+
+/// Helper to render type parameters
+fn tybounds<'a, 'tcx: 'a>(
+    bounds: &'a [clean::PolyTrait],
+    lt: &'a Option<clean::Lifetime>,
+    cx: &'a Context<'tcx>,
+) -> impl fmt::Display + 'a + Captures<'tcx> {
+    display_fn(move |f| {
+        for (i, bound) in bounds.iter().enumerate() {
+            if i > 0 {
+                write!(f, " + ")?;
+            }
+
+            fmt::Display::fmt(&bound.print(cx), f)?;
+        }
+
+        if let Some(lt) = lt {
+            write!(f, " + ")?;
+            fmt::Display::fmt(&lt.print(), f)?;
+        }
+        Ok(())
+    })
+}
+
+pub(crate) fn anchor<'a, 'cx: 'a>(
+    did: DefId,
+    text: Symbol,
+    cx: &'cx Context<'_>,
+) -> impl fmt::Display + 'a {
+    let parts = href(did, cx);
+    display_fn(move |f| {
+        if let Ok((url, short_ty, fqp)) = parts {
+            write!(
+                f,
+                r#"<a class="{}" href="{}" title="{} {}">{}</a>"#,
+                short_ty,
+                url,
+                short_ty,
+                join_with_double_colon(&fqp),
+                text.as_str()
+            )
+        } else {
+            write!(f, "{}", text)
+        }
+    })
+}
+
+fn fmt_type<'cx>(
+    t: &clean::Type,
+    f: &mut fmt::Formatter<'_>,
+    use_absolute: bool,
+    cx: &'cx Context<'_>,
+) -> fmt::Result {
+    trace!("fmt_type(t = {:?})", t);
+
+    match *t {
+        clean::Generic(name) => write!(f, "{}", name),
+        clean::Type::Path { ref path } => {
+            // Paths like `T::Output` and `Self::Output` should be rendered with all segments.
+            let did = path.def_id();
+            resolved_path(f, did, path, path.is_assoc_ty(), use_absolute, cx)
+        }
+        clean::DynTrait(ref bounds, ref lt) => {
+            f.write_str("dyn ")?;
+            fmt::Display::fmt(&tybounds(bounds, lt, cx), f)
+        }
+        clean::Infer => write!(f, "_"),
+        clean::Primitive(clean::PrimitiveType::Never) => {
+            primitive_link(f, PrimitiveType::Never, "!", cx)
+        }
+        clean::Primitive(prim) => primitive_link(f, prim, prim.as_sym().as_str(), cx),
+        clean::BareFunction(ref decl) => {
+            if f.alternate() {
+                write!(
+                    f,
+                    "{:#}{}{:#}fn{:#}",
+                    decl.print_hrtb_with_space(cx),
+                    decl.unsafety.print_with_space(),
+                    print_abi_with_space(decl.abi),
+                    decl.decl.print(cx),
+                )
+            } else {
+                write!(
+                    f,
+                    "{}{}{}",
+                    decl.print_hrtb_with_space(cx),
+                    decl.unsafety.print_with_space(),
+                    print_abi_with_space(decl.abi)
+                )?;
+                primitive_link(f, PrimitiveType::Fn, "fn", cx)?;
+                write!(f, "{}", decl.decl.print(cx))
+            }
+        }
+        clean::Tuple(ref typs) => {
+            match &typs[..] {
+                &[] => primitive_link(f, PrimitiveType::Unit, "()", cx),
+                &[ref one] => {
+                    if let clean::Generic(name) = one {
+                        primitive_link(f, PrimitiveType::Tuple, &format!("({name},)"), cx)
+                    } else {
+                        write!(f, "(")?;
+                        // Carry `f.alternate()` into this display w/o branching manually.
+                        fmt::Display::fmt(&one.print(cx), f)?;
+                        write!(f, ",)")
+                    }
+                }
+                many => {
+                    let generic_names: Vec<Symbol> = many
+                        .iter()
+                        .filter_map(|t| match t {
+                            clean::Generic(name) => Some(*name),
+                            _ => None,
+                        })
+                        .collect();
+                    let is_generic = generic_names.len() == many.len();
+                    if is_generic {
+                        primitive_link(
+                            f,
+                            PrimitiveType::Tuple,
+                            &format!("({})", generic_names.iter().map(|s| s.as_str()).join(", ")),
+                            cx,
+                        )
+                    } else {
+                        write!(f, "(")?;
+                        for (i, item) in many.iter().enumerate() {
+                            if i != 0 {
+                                write!(f, ", ")?;
+                            }
+                            // Carry `f.alternate()` into this display w/o branching manually.
+                            fmt::Display::fmt(&item.print(cx), f)?;
+                        }
+                        write!(f, ")")
+                    }
+                }
+            }
+        }
+        clean::Slice(ref t) => match **t {
+            clean::Generic(name) => {
+                primitive_link(f, PrimitiveType::Slice, &format!("[{name}]"), cx)
+            }
+            _ => {
+                write!(f, "[")?;
+                fmt::Display::fmt(&t.print(cx), f)?;
+                write!(f, "]")
+            }
+        },
+        clean::Array(ref t, ref n) => {
+            primitive_link(f, PrimitiveType::Array, "[", cx)?;
+            fmt::Display::fmt(&t.print(cx), f)?;
+            if f.alternate() {
+                primitive_link(f, PrimitiveType::Array, &format!("; {}]", n), cx)
+            } else {
+                primitive_link(f, PrimitiveType::Array, &format!("; {}]", Escape(n)), cx)
+            }
+        }
+        clean::RawPointer(m, ref t) => {
+            let m = match m {
+                hir::Mutability::Mut => "mut",
+                hir::Mutability::Not => "const",
+            };
+
+            if matches!(**t, clean::Generic(_)) || t.is_assoc_ty() {
+                let text = if f.alternate() {
+                    format!("*{} {:#}", m, t.print(cx))
+                } else {
+                    format!("*{} {}", m, t.print(cx))
+                };
+                primitive_link(f, clean::PrimitiveType::RawPointer, &text, cx)
+            } else {
+                primitive_link(f, clean::PrimitiveType::RawPointer, &format!("*{} ", m), cx)?;
+                fmt::Display::fmt(&t.print(cx), f)
+            }
+        }
+        clean::BorrowedRef { lifetime: ref l, mutability, type_: ref ty } => {
+            let lt = match l {
+                Some(l) => format!("{} ", l.print()),
+                _ => String::new(),
+            };
+            let m = mutability.print_with_space();
+            let amp = if f.alternate() { "&".to_string() } else { "&amp;".to_string() };
+            match **ty {
+                clean::DynTrait(ref bounds, ref trait_lt)
+                    if bounds.len() > 1 || trait_lt.is_some() =>
+                {
+                    write!(f, "{}{}{}(", amp, lt, m)?;
+                    fmt_type(ty, f, use_absolute, cx)?;
+                    write!(f, ")")
+                }
+                clean::Generic(..) => {
+                    primitive_link(
+                        f,
+                        PrimitiveType::Reference,
+                        &format!("{}{}{}", amp, lt, m),
+                        cx,
+                    )?;
+                    fmt_type(ty, f, use_absolute, cx)
+                }
+                _ => {
+                    write!(f, "{}{}{}", amp, lt, m)?;
+                    fmt_type(ty, f, use_absolute, cx)
+                }
+            }
+        }
+        clean::ImplTrait(ref bounds) => {
+            if f.alternate() {
+                write!(f, "impl {:#}", print_generic_bounds(bounds, cx))
+            } else {
+                write!(f, "impl {}", print_generic_bounds(bounds, cx))
+            }
+        }
+        clean::QPath { ref assoc, ref self_type, ref trait_, should_show_cast } => {
+            if f.alternate() {
+                if should_show_cast {
+                    write!(f, "<{:#} as {:#}>::", self_type.print(cx), trait_.print(cx))?
+                } else {
+                    write!(f, "{:#}::", self_type.print(cx))?
+                }
+            } else {
+                if should_show_cast {
+                    write!(f, "&lt;{} as {}&gt;::", self_type.print(cx), trait_.print(cx))?
+                } else {
+                    write!(f, "{}::", self_type.print(cx))?
+                }
+            };
+            // It's pretty unsightly to look at `<A as B>::C` in output, and
+            // we've got hyperlinking on our side, so try to avoid longer
+            // notation as much as possible by making `C` a hyperlink to trait
+            // `B` to disambiguate.
+            //
+            // FIXME: this is still a lossy conversion and there should probably
+            //        be a better way of representing this in general? Most of
+            //        the ugliness comes from inlining across crates where
+            //        everything comes in as a fully resolved QPath (hard to
+            //        look at).
+            match href(trait_.def_id(), cx) {
+                Ok((ref url, _, ref path)) if !f.alternate() => {
+                    write!(
+                        f,
+                        "<a class=\"associatedtype\" href=\"{url}#{shortty}.{name}\" \
+                                    title=\"type {path}::{name}\">{name}</a>{args}",
+                        url = url,
+                        shortty = ItemType::AssocType,
+                        name = assoc.name,
+                        path = join_with_double_colon(path),
+                        args = assoc.args.print(cx),
+                    )?;
+                }
+                _ => write!(f, "{}{:#}", assoc.name, assoc.args.print(cx))?,
+            }
+            Ok(())
+        }
+    }
+}
+
+impl clean::Type {
+    pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'b + Captures<'tcx> {
+        display_fn(move |f| fmt_type(self, f, false, cx))
+    }
+}
+
+impl clean::Path {
+    pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'b + Captures<'tcx> {
+        display_fn(move |f| resolved_path(f, self.def_id(), self, false, false, cx))
+    }
+}
+
+impl clean::Impl {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        use_absolute: bool,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            if f.alternate() {
+                write!(f, "impl{:#} ", self.generics.print(cx))?;
+            } else {
+                write!(f, "impl{} ", self.generics.print(cx))?;
+            }
+
+            if let Some(ref ty) = self.trait_ {
+                match self.polarity {
+                    ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => {}
+                    ty::ImplPolarity::Negative => write!(f, "!")?,
+                }
+                fmt::Display::fmt(&ty.print(cx), f)?;
+                write!(f, " for ")?;
+            }
+
+            if let clean::Type::Tuple(types) = &self.for_ &&
+                let [clean::Type::Generic(name)] = &types[..] &&
+                (self.kind.is_fake_variadic() || self.kind.is_auto())
+            {
+                // Hardcoded anchor library/core/src/primitive_docs.rs
+                // Link should match `# Trait implementations`
+                primitive_link_fragment(f, PrimitiveType::Tuple, &format!("({name}₁, {name}₂, …, {name}ₙ)"), "#trait-implementations-1", cx)?;
+            } else if let clean::BareFunction(bare_fn) = &self.for_ &&
+                let [clean::Argument { type_: clean::Type::Generic(name), .. }] = &bare_fn.decl.inputs.values[..] &&
+                (self.kind.is_fake_variadic() || self.kind.is_auto())
+            {
+                // Hardcoded anchor library/core/src/primitive_docs.rs
+                // Link should match `# Trait implementations`
+
+                let hrtb = bare_fn.print_hrtb_with_space(cx);
+                let unsafety = bare_fn.unsafety.print_with_space();
+                let abi = print_abi_with_space(bare_fn.abi);
+                if f.alternate() {
+                    write!(
+                        f,
+                        "{hrtb:#}{unsafety}{abi:#}",
+                    )?;
+                } else {
+                    write!(
+                        f,
+                        "{hrtb}{unsafety}{abi}",
+                    )?;
+                }
+                let ellipsis = if bare_fn.decl.c_variadic {
+                    ", ..."
+                } else {
+                    ""
+                };
+                primitive_link_fragment(f, PrimitiveType::Tuple, &format!("fn ({name}₁, {name}₂, …, {name}ₙ{ellipsis})"), "#trait-implementations-1", cx)?;
+                // Write output.
+                if let clean::FnRetTy::Return(ty) = &bare_fn.decl.output {
+                    write!(f, " -> ")?;
+                    fmt_type(ty, f, use_absolute, cx)?;
+                }
+            } else if let Some(ty) = self.kind.as_blanket_ty() {
+                fmt_type(ty, f, use_absolute, cx)?;
+            } else {
+                fmt_type(&self.for_, f, use_absolute, cx)?;
+            }
+
+            fmt::Display::fmt(&print_where_clause(&self.generics, cx, 0, Ending::Newline), f)?;
+            Ok(())
+        })
+    }
+}
+
+impl clean::Arguments {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            for (i, input) in self.values.iter().enumerate() {
+                if !input.name.is_empty() {
+                    write!(f, "{}: ", input.name)?;
+                }
+                if f.alternate() {
+                    write!(f, "{:#}", input.type_.print(cx))?;
+                } else {
+                    write!(f, "{}", input.type_.print(cx))?;
+                }
+                if i + 1 < self.values.len() {
+                    write!(f, ", ")?;
+                }
+            }
+            Ok(())
+        })
+    }
+}
+
+impl clean::FnRetTy {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match self {
+            clean::Return(clean::Tuple(tys)) if tys.is_empty() => Ok(()),
+            clean::Return(ty) if f.alternate() => {
+                write!(f, " -> {:#}", ty.print(cx))
+            }
+            clean::Return(ty) => write!(f, " -&gt; {}", ty.print(cx)),
+            clean::DefaultReturn => Ok(()),
+        })
+    }
+}
+
+impl clean::BareFunctionDecl {
+    fn print_hrtb_with_space<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            if !self.generic_params.is_empty() {
+                write!(
+                    f,
+                    "for&lt;{}&gt; ",
+                    comma_sep(self.generic_params.iter().map(|g| g.print(cx)), true)
+                )
+            } else {
+                Ok(())
+            }
+        })
+    }
+}
+
+impl clean::FnDecl {
+    pub(crate) fn print<'b, 'a: 'b, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'b + Captures<'tcx> {
+        display_fn(move |f| {
+            let ellipsis = if self.c_variadic { ", ..." } else { "" };
+            if f.alternate() {
+                write!(
+                    f,
+                    "({args:#}{ellipsis}){arrow:#}",
+                    args = self.inputs.print(cx),
+                    ellipsis = ellipsis,
+                    arrow = self.output.print(cx)
+                )
+            } else {
+                write!(
+                    f,
+                    "({args}{ellipsis}){arrow}",
+                    args = self.inputs.print(cx),
+                    ellipsis = ellipsis,
+                    arrow = self.output.print(cx)
+                )
+            }
+        })
+    }
+
+    /// * `header_len`: The length of the function header and name. In other words, the number of
+    ///   characters in the function declaration up to but not including the parentheses.
+    ///   <br>Used to determine line-wrapping.
+    /// * `indent`: The number of spaces to indent each successive line with, if line-wrapping is
+    ///   necessary.
+    /// * `asyncness`: Whether the function is async or not.
+    pub(crate) fn full_print<'a, 'tcx: 'a>(
+        &'a self,
+        header_len: usize,
+        indent: usize,
+        asyncness: hir::IsAsync,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| self.inner_full_print(header_len, indent, asyncness, f, cx))
+    }
+
+    fn inner_full_print(
+        &self,
+        header_len: usize,
+        indent: usize,
+        asyncness: hir::IsAsync,
+        f: &mut fmt::Formatter<'_>,
+        cx: &Context<'_>,
+    ) -> fmt::Result {
+        let amp = if f.alternate() { "&" } else { "&amp;" };
+        let mut args = Buffer::html();
+        let mut args_plain = Buffer::new();
+        for (i, input) in self.inputs.values.iter().enumerate() {
+            if let Some(selfty) = input.to_self() {
+                match selfty {
+                    clean::SelfValue => {
+                        args.push_str("self");
+                        args_plain.push_str("self");
+                    }
+                    clean::SelfBorrowed(Some(ref lt), mtbl) => {
+                        write!(args, "{}{} {}self", amp, lt.print(), mtbl.print_with_space());
+                        write!(args_plain, "&{} {}self", lt.print(), mtbl.print_with_space());
+                    }
+                    clean::SelfBorrowed(None, mtbl) => {
+                        write!(args, "{}{}self", amp, mtbl.print_with_space());
+                        write!(args_plain, "&{}self", mtbl.print_with_space());
+                    }
+                    clean::SelfExplicit(ref typ) => {
+                        if f.alternate() {
+                            write!(args, "self: {:#}", typ.print(cx));
+                        } else {
+                            write!(args, "self: {}", typ.print(cx));
+                        }
+                        write!(args_plain, "self: {:#}", typ.print(cx));
+                    }
+                }
+            } else {
+                if i > 0 {
+                    args.push_str("<br>");
+                }
+                if input.is_const {
+                    args.push_str("const ");
+                    args_plain.push_str("const ");
+                }
+                if !input.name.is_empty() {
+                    write!(args, "{}: ", input.name);
+                    write!(args_plain, "{}: ", input.name);
+                }
+
+                if f.alternate() {
+                    write!(args, "{:#}", input.type_.print(cx));
+                } else {
+                    write!(args, "{}", input.type_.print(cx));
+                }
+                write!(args_plain, "{:#}", input.type_.print(cx));
+            }
+            if i + 1 < self.inputs.values.len() {
+                args.push_str(",");
+                args_plain.push_str(",");
+            }
+        }
+
+        let mut args_plain = format!("({})", args_plain.into_inner());
+        let mut args = args.into_inner();
+
+        if self.c_variadic {
+            args.push_str(",<br> ...");
+            args_plain.push_str(", ...");
+        }
+
+        let arrow_plain;
+        let arrow = if let hir::IsAsync::Async = asyncness {
+            let output = self.sugared_async_return_type();
+            arrow_plain = format!("{:#}", output.print(cx));
+            if f.alternate() { arrow_plain.clone() } else { format!("{}", output.print(cx)) }
+        } else {
+            arrow_plain = format!("{:#}", self.output.print(cx));
+            if f.alternate() { arrow_plain.clone() } else { format!("{}", self.output.print(cx)) }
+        };
+
+        let declaration_len = header_len + args_plain.len() + arrow_plain.len();
+        let output = if declaration_len > 80 {
+            let full_pad = format!("<br>{}", "&nbsp;".repeat(indent + 4));
+            let close_pad = format!("<br>{}", "&nbsp;".repeat(indent));
+            format!(
+                "({pad}{args}{close}){arrow}",
+                pad = if self.inputs.values.is_empty() { "" } else { &full_pad },
+                args = args.replace("<br>", &full_pad),
+                close = close_pad,
+                arrow = arrow
+            )
+        } else {
+            format!("({args}){arrow}", args = args.replace("<br>", " "), arrow = arrow)
+        };
+
+        if f.alternate() {
+            write!(f, "{}", output.replace("<br>", "\n"))
+        } else {
+            write!(f, "{}", output)
+        }
+    }
+}
+
+impl clean::Visibility {
+    pub(crate) fn print_with_space<'a, 'tcx: 'a>(
+        self,
+        item_did: ItemId,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        use std::fmt::Write as _;
+
+        let to_print: Cow<'static, str> = match self {
+            clean::Public => "pub ".into(),
+            clean::Inherited => "".into(),
+            clean::Visibility::Restricted(vis_did) => {
+                // FIXME(camelid): This may not work correctly if `item_did` is a module.
+                //                 However, rustdoc currently never displays a module's
+                //                 visibility, so it shouldn't matter.
+                let parent_module = find_nearest_parent_module(cx.tcx(), item_did.expect_def_id());
+
+                if vis_did.is_crate_root() {
+                    "pub(crate) ".into()
+                } else if parent_module == Some(vis_did) {
+                    // `pub(in foo)` where `foo` is the parent module
+                    // is the same as no visibility modifier
+                    "".into()
+                } else if parent_module
+                    .and_then(|parent| find_nearest_parent_module(cx.tcx(), parent))
+                    == Some(vis_did)
+                {
+                    "pub(super) ".into()
+                } else {
+                    let path = cx.tcx().def_path(vis_did);
+                    debug!("path={:?}", path);
+                    // modified from `resolved_path()` to work with `DefPathData`
+                    let last_name = path.data.last().unwrap().data.get_opt_name().unwrap();
+                    let anchor = anchor(vis_did, last_name, cx).to_string();
+
+                    let mut s = "pub(in ".to_owned();
+                    for seg in &path.data[..path.data.len() - 1] {
+                        let _ = write!(s, "{}::", seg.data.get_opt_name().unwrap());
+                    }
+                    let _ = write!(s, "{}) ", anchor);
+                    s.into()
+                }
+            }
+        };
+        display_fn(move |f| write!(f, "{}", to_print))
+    }
+
+    /// This function is the same as print_with_space, except that it renders no links.
+    /// It's used for macros' rendered source view, which is syntax highlighted and cannot have
+    /// any HTML in it.
+    pub(crate) fn to_src_with_space<'a, 'tcx: 'a>(
+        self,
+        tcx: TyCtxt<'tcx>,
+        item_did: DefId,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        let to_print = match self {
+            clean::Public => "pub ".to_owned(),
+            clean::Inherited => String::new(),
+            clean::Visibility::Restricted(vis_did) => {
+                // FIXME(camelid): This may not work correctly if `item_did` is a module.
+                //                 However, rustdoc currently never displays a module's
+                //                 visibility, so it shouldn't matter.
+                let parent_module = find_nearest_parent_module(tcx, item_did);
+
+                if vis_did.is_crate_root() {
+                    "pub(crate) ".to_owned()
+                } else if parent_module == Some(vis_did) {
+                    // `pub(in foo)` where `foo` is the parent module
+                    // is the same as no visibility modifier
+                    String::new()
+                } else if parent_module.and_then(|parent| find_nearest_parent_module(tcx, parent))
+                    == Some(vis_did)
+                {
+                    "pub(super) ".to_owned()
+                } else {
+                    format!("pub(in {}) ", tcx.def_path_str(vis_did))
+                }
+            }
+        };
+        display_fn(move |f| f.write_str(&to_print))
+    }
+}
+
+pub(crate) trait PrintWithSpace {
+    fn print_with_space(&self) -> &str;
+}
+
+impl PrintWithSpace for hir::Unsafety {
+    fn print_with_space(&self) -> &str {
+        match self {
+            hir::Unsafety::Unsafe => "unsafe ",
+            hir::Unsafety::Normal => "",
+        }
+    }
+}
+
+impl PrintWithSpace for hir::IsAsync {
+    fn print_with_space(&self) -> &str {
+        match self {
+            hir::IsAsync::Async => "async ",
+            hir::IsAsync::NotAsync => "",
+        }
+    }
+}
+
+impl PrintWithSpace for hir::Mutability {
+    fn print_with_space(&self) -> &str {
+        match self {
+            hir::Mutability::Not => "",
+            hir::Mutability::Mut => "mut ",
+        }
+    }
+}
+
+pub(crate) fn print_constness_with_space(
+    c: &hir::Constness,
+    s: Option<ConstStability>,
+) -> &'static str {
+    match (c, s) {
+        // const stable or when feature(staged_api) is not set
+        (
+            hir::Constness::Const,
+            Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }),
+        )
+        | (hir::Constness::Const, None) => "const ",
+        // const unstable or not const
+        _ => "",
+    }
+}
+
+impl clean::Import {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match self.kind {
+            clean::ImportKind::Simple(name) => {
+                if name == self.source.path.last() {
+                    write!(f, "use {};", self.source.print(cx))
+                } else {
+                    write!(f, "use {} as {};", self.source.print(cx), name)
+                }
+            }
+            clean::ImportKind::Glob => {
+                if self.source.path.segments.is_empty() {
+                    write!(f, "use *;")
+                } else {
+                    write!(f, "use {}::*;", self.source.print(cx))
+                }
+            }
+        })
+    }
+}
+
+impl clean::ImportSource {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match self.did {
+            Some(did) => resolved_path(f, did, &self.path, true, false, cx),
+            _ => {
+                for seg in &self.path.segments[..self.path.segments.len() - 1] {
+                    write!(f, "{}::", seg.name)?;
+                }
+                let name = self.path.last();
+                if let hir::def::Res::PrimTy(p) = self.path.res {
+                    primitive_link(f, PrimitiveType::from(p), name.as_str(), cx)?;
+                } else {
+                    write!(f, "{}", name)?;
+                }
+                Ok(())
+            }
+        })
+    }
+}
+
+impl clean::TypeBinding {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| {
+            f.write_str(self.assoc.name.as_str())?;
+            if f.alternate() {
+                write!(f, "{:#}", self.assoc.args.print(cx))?;
+            } else {
+                write!(f, "{}", self.assoc.args.print(cx))?;
+            }
+            match self.kind {
+                clean::TypeBindingKind::Equality { ref term } => {
+                    if f.alternate() {
+                        write!(f, " = {:#}", term.print(cx))?;
+                    } else {
+                        write!(f, " = {}", term.print(cx))?;
+                    }
+                }
+                clean::TypeBindingKind::Constraint { ref bounds } => {
+                    if !bounds.is_empty() {
+                        if f.alternate() {
+                            write!(f, ": {:#}", print_generic_bounds(bounds, cx))?;
+                        } else {
+                            write!(f, ":&nbsp;{}", print_generic_bounds(bounds, cx))?;
+                        }
+                    }
+                }
+            }
+            Ok(())
+        })
+    }
+}
+
+pub(crate) fn print_abi_with_space(abi: Abi) -> impl fmt::Display {
+    display_fn(move |f| {
+        let quot = if f.alternate() { "\"" } else { "&quot;" };
+        match abi {
+            Abi::Rust => Ok(()),
+            abi => write!(f, "extern {0}{1}{0} ", quot, abi.name()),
+        }
+    })
+}
+
+pub(crate) fn print_default_space<'a>(v: bool) -> &'a str {
+    if v { "default " } else { "" }
+}
+
+impl clean::GenericArg {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        display_fn(move |f| match self {
+            clean::GenericArg::Lifetime(lt) => fmt::Display::fmt(&lt.print(), f),
+            clean::GenericArg::Type(ty) => fmt::Display::fmt(&ty.print(cx), f),
+            clean::GenericArg::Const(ct) => fmt::Display::fmt(&ct.print(cx.tcx()), f),
+            clean::GenericArg::Infer => fmt::Display::fmt("_", f),
+        })
+    }
+}
+
+impl clean::types::Term {
+    pub(crate) fn print<'a, 'tcx: 'a>(
+        &'a self,
+        cx: &'a Context<'tcx>,
+    ) -> impl fmt::Display + 'a + Captures<'tcx> {
+        match self {
+            clean::types::Term::Type(ty) => ty.print(cx),
+            _ => todo!(),
+        }
+    }
+}
+
+pub(crate) fn display_fn(
+    f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
+) -> impl fmt::Display {
+    struct WithFormatter<F>(Cell<Option<F>>);
+
+    impl<F> fmt::Display for WithFormatter<F>
+    where
+        F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
+    {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            (self.0.take()).unwrap()(f)
+        }
+    }
+
+    WithFormatter(Cell::new(Some(f)))
+}
diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
new file mode 100644
index 000000000..05547ea15
--- /dev/null
+++ b/src/librustdoc/html/highlight.rs
@@ -0,0 +1,805 @@
+//! Basic syntax highlighting functionality.
+//!
+//! This module uses librustc_ast's lexer to provide token-based highlighting for
+//! the HTML documentation generated by rustdoc.
+//!
+//! Use the `render_with_highlighting` to highlight some rust code.
+
+use crate::clean::PrimitiveType;
+use crate::html::escape::Escape;
+use crate::html::render::Context;
+
+use std::collections::VecDeque;
+use std::fmt::{Display, Write};
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_lexer::{LiteralKind, TokenKind};
+use rustc_span::edition::Edition;
+use rustc_span::symbol::Symbol;
+use rustc_span::{BytePos, Span, DUMMY_SP};
+
+use super::format::{self, Buffer};
+use super::render::LinkFromSrc;
+
+/// This type is needed in case we want to render links on items to allow to go to their definition.
+pub(crate) struct HrefContext<'a, 'b, 'c> {
+    pub(crate) context: &'a Context<'b>,
+    /// This span contains the current file we're going through.
+    pub(crate) file_span: Span,
+    /// This field is used to know "how far" from the top of the directory we are to link to either
+    /// documentation pages or other source pages.
+    pub(crate) root_path: &'c str,
+}
+
+/// Decorations are represented as a map from CSS class to vector of character ranges.
+/// Each range will be wrapped in a span with that class.
+pub(crate) struct DecorationInfo(pub(crate) FxHashMap<&'static str, Vec<(u32, u32)>>);
+
+/// Highlights `src`, returning the HTML output.
+pub(crate) fn render_with_highlighting(
+    src: &str,
+    out: &mut Buffer,
+    class: Option<&str>,
+    playground_button: Option<&str>,
+    tooltip: Option<(Option<Edition>, &str)>,
+    edition: Edition,
+    extra_content: Option<Buffer>,
+    href_context: Option<HrefContext<'_, '_, '_>>,
+    decoration_info: Option<DecorationInfo>,
+) {
+    debug!("highlighting: ================\n{}\n==============", src);
+    if let Some((edition_info, class)) = tooltip {
+        write!(
+            out,
+            "<div class='information'><div class='tooltip {}'{}>ⓘ</div></div>",
+            class,
+            if let Some(edition_info) = edition_info {
+                format!(" data-edition=\"{}\"", edition_info)
+            } else {
+                String::new()
+            },
+        );
+    }
+
+    write_header(out, class, extra_content);
+    write_code(out, src, edition, href_context, decoration_info);
+    write_footer(out, playground_button);
+}
+
+fn write_header(out: &mut Buffer, class: Option<&str>, extra_content: Option<Buffer>) {
+    write!(out, "<div class=\"example-wrap\">");
+    if let Some(extra) = extra_content {
+        out.push_buffer(extra);
+    }
+    if let Some(class) = class {
+        write!(out, "<pre class=\"rust {}\">", class);
+    } else {
+        write!(out, "<pre class=\"rust\">");
+    }
+    write!(out, "<code>");
+}
+
+/// Convert the given `src` source code into HTML by adding classes for highlighting.
+///
+/// This code is used to render code blocks (in the documentation) as well as the source code pages.
+///
+/// Some explanations on the last arguments:
+///
+/// In case we are rendering a code block and not a source code file, `href_context` will be `None`.
+/// To put it more simply: if `href_context` is `None`, the code won't try to generate links to an
+/// item definition.
+///
+/// More explanations about spans and how we use them here are provided in the
+fn write_code(
+    out: &mut Buffer,
+    src: &str,
+    edition: Edition,
+    href_context: Option<HrefContext<'_, '_, '_>>,
+    decoration_info: Option<DecorationInfo>,
+) {
+    // This replace allows to fix how the code source with DOS backline characters is displayed.
+    let src = src.replace("\r\n", "\n");
+    let mut closing_tags: Vec<&'static str> = Vec::new();
+    Classifier::new(
+        &src,
+        edition,
+        href_context.as_ref().map(|c| c.file_span).unwrap_or(DUMMY_SP),
+        decoration_info,
+    )
+    .highlight(&mut |highlight| {
+        match highlight {
+            Highlight::Token { text, class } => string(out, Escape(text), class, &href_context),
+            Highlight::EnterSpan { class } => {
+                closing_tags.push(enter_span(out, class, &href_context))
+            }
+            Highlight::ExitSpan => {
+                exit_span(out, closing_tags.pop().expect("ExitSpan without EnterSpan"))
+            }
+        };
+    });
+}
+
+fn write_footer(out: &mut Buffer, playground_button: Option<&str>) {
+    writeln!(out, "</code></pre>{}</div>", playground_button.unwrap_or_default());
+}
+
+/// How a span of text is classified. Mostly corresponds to token kinds.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+enum Class {
+    Comment,
+    DocComment,
+    Attribute,
+    KeyWord,
+    // Keywords that do pointer/reference stuff.
+    RefKeyWord,
+    Self_(Span),
+    Op,
+    Macro(Span),
+    MacroNonTerminal,
+    String,
+    Number,
+    Bool,
+    Ident(Span),
+    Lifetime,
+    PreludeTy,
+    PreludeVal,
+    QuestionMark,
+    Decoration(&'static str),
+}
+
+impl Class {
+    /// Returns the css class expected by rustdoc for each `Class`.
+    fn as_html(self) -> &'static str {
+        match self {
+            Class::Comment => "comment",
+            Class::DocComment => "doccomment",
+            Class::Attribute => "attribute",
+            Class::KeyWord => "kw",
+            Class::RefKeyWord => "kw-2",
+            Class::Self_(_) => "self",
+            Class::Op => "op",
+            Class::Macro(_) => "macro",
+            Class::MacroNonTerminal => "macro-nonterminal",
+            Class::String => "string",
+            Class::Number => "number",
+            Class::Bool => "bool-val",
+            Class::Ident(_) => "ident",
+            Class::Lifetime => "lifetime",
+            Class::PreludeTy => "prelude-ty",
+            Class::PreludeVal => "prelude-val",
+            Class::QuestionMark => "question-mark",
+            Class::Decoration(kind) => kind,
+        }
+    }
+
+    /// In case this is an item which can be converted into a link to a definition, it'll contain
+    /// a "span" (a tuple representing `(lo, hi)` equivalent of `Span`).
+    fn get_span(self) -> Option<Span> {
+        match self {
+            Self::Ident(sp) | Self::Self_(sp) | Self::Macro(sp) => Some(sp),
+            Self::Comment
+            | Self::DocComment
+            | Self::Attribute
+            | Self::KeyWord
+            | Self::RefKeyWord
+            | Self::Op
+            | Self::MacroNonTerminal
+            | Self::String
+            | Self::Number
+            | Self::Bool
+            | Self::Lifetime
+            | Self::PreludeTy
+            | Self::PreludeVal
+            | Self::QuestionMark
+            | Self::Decoration(_) => None,
+        }
+    }
+}
+
+enum Highlight<'a> {
+    Token { text: &'a str, class: Option<Class> },
+    EnterSpan { class: Class },
+    ExitSpan,
+}
+
+struct TokenIter<'a> {
+    src: &'a str,
+}
+
+impl<'a> Iterator for TokenIter<'a> {
+    type Item = (TokenKind, &'a str);
+    fn next(&mut self) -> Option<(TokenKind, &'a str)> {
+        if self.src.is_empty() {
+            return None;
+        }
+        let token = rustc_lexer::first_token(self.src);
+        let (text, rest) = self.src.split_at(token.len as usize);
+        self.src = rest;
+        Some((token.kind, text))
+    }
+}
+
+/// Classifies into identifier class; returns `None` if this is a non-keyword identifier.
+fn get_real_ident_class(text: &str, edition: Edition, allow_path_keywords: bool) -> Option<Class> {
+    let ignore: &[&str] =
+        if allow_path_keywords { &["self", "Self", "super", "crate"] } else { &["self", "Self"] };
+    if ignore.iter().any(|k| *k == text) {
+        return None;
+    }
+    Some(match text {
+        "ref" | "mut" => Class::RefKeyWord,
+        "false" | "true" => Class::Bool,
+        _ if Symbol::intern(text).is_reserved(|| edition) => Class::KeyWord,
+        _ => return None,
+    })
+}
+
+/// This iterator comes from the same idea than "Peekable" except that it allows to "peek" more than
+/// just the next item by using `peek_next`. The `peek` method always returns the next item after
+/// the current one whereas `peek_next` will return the next item after the last one peeked.
+///
+/// You can use both `peek` and `peek_next` at the same time without problem.
+struct PeekIter<'a> {
+    stored: VecDeque<(TokenKind, &'a str)>,
+    /// This position is reinitialized when using `next`. It is used in `peek_next`.
+    peek_pos: usize,
+    iter: TokenIter<'a>,
+}
+
+impl<'a> PeekIter<'a> {
+    fn new(iter: TokenIter<'a>) -> Self {
+        Self { stored: VecDeque::new(), peek_pos: 0, iter }
+    }
+    /// Returns the next item after the current one. It doesn't interfer with `peek_next` output.
+    fn peek(&mut self) -> Option<&(TokenKind, &'a str)> {
+        if self.stored.is_empty() {
+            if let Some(next) = self.iter.next() {
+                self.stored.push_back(next);
+            }
+        }
+        self.stored.front()
+    }
+    /// Returns the next item after the last one peeked. It doesn't interfer with `peek` output.
+    fn peek_next(&mut self) -> Option<&(TokenKind, &'a str)> {
+        self.peek_pos += 1;
+        if self.peek_pos - 1 < self.stored.len() {
+            self.stored.get(self.peek_pos - 1)
+        } else if let Some(next) = self.iter.next() {
+            self.stored.push_back(next);
+            self.stored.back()
+        } else {
+            None
+        }
+    }
+}
+
+impl<'a> Iterator for PeekIter<'a> {
+    type Item = (TokenKind, &'a str);
+    fn next(&mut self) -> Option<Self::Item> {
+        self.peek_pos = 0;
+        if let Some(first) = self.stored.pop_front() { Some(first) } else { self.iter.next() }
+    }
+}
+
+/// Custom spans inserted into the source. Eg --scrape-examples uses this to highlight function calls
+struct Decorations {
+    starts: Vec<(u32, &'static str)>,
+    ends: Vec<u32>,
+}
+
+impl Decorations {
+    fn new(info: DecorationInfo) -> Self {
+        // Extract tuples (start, end, kind) into separate sequences of (start, kind) and (end).
+        let (mut starts, mut ends): (Vec<_>, Vec<_>) = info
+            .0
+            .into_iter()
+            .flat_map(|(kind, ranges)| ranges.into_iter().map(move |(lo, hi)| ((lo, kind), hi)))
+            .unzip();
+
+        // Sort the sequences in document order.
+        starts.sort_by_key(|(lo, _)| *lo);
+        ends.sort();
+
+        Decorations { starts, ends }
+    }
+}
+
+/// Processes program tokens, classifying strings of text by highlighting
+/// category (`Class`).
+struct Classifier<'a> {
+    tokens: PeekIter<'a>,
+    in_attribute: bool,
+    in_macro: bool,
+    in_macro_nonterminal: bool,
+    edition: Edition,
+    byte_pos: u32,
+    file_span: Span,
+    src: &'a str,
+    decorations: Option<Decorations>,
+}
+
+impl<'a> Classifier<'a> {
+    /// Takes as argument the source code to HTML-ify, the rust edition to use and the source code
+    /// file span which will be used later on by the `span_correspondance_map`.
+    fn new(
+        src: &str,
+        edition: Edition,
+        file_span: Span,
+        decoration_info: Option<DecorationInfo>,
+    ) -> Classifier<'_> {
+        let tokens = PeekIter::new(TokenIter { src });
+        let decorations = decoration_info.map(Decorations::new);
+        Classifier {
+            tokens,
+            in_attribute: false,
+            in_macro: false,
+            in_macro_nonterminal: false,
+            edition,
+            byte_pos: 0,
+            file_span,
+            src,
+            decorations,
+        }
+    }
+
+    /// Convenient wrapper to create a [`Span`] from a position in the file.
+    fn new_span(&self, lo: u32, text: &str) -> Span {
+        let hi = lo + text.len() as u32;
+        let file_lo = self.file_span.lo();
+        self.file_span.with_lo(file_lo + BytePos(lo)).with_hi(file_lo + BytePos(hi))
+    }
+
+    /// Concatenate colons and idents as one when possible.
+    fn get_full_ident_path(&mut self) -> Vec<(TokenKind, usize, usize)> {
+        let start = self.byte_pos as usize;
+        let mut pos = start;
+        let mut has_ident = false;
+        let edition = self.edition;
+
+        loop {
+            let mut nb = 0;
+            while let Some((TokenKind::Colon, _)) = self.tokens.peek() {
+                self.tokens.next();
+                nb += 1;
+            }
+            // Ident path can start with "::" but if we already have content in the ident path,
+            // the "::" is mandatory.
+            if has_ident && nb == 0 {
+                return vec![(TokenKind::Ident, start, pos)];
+            } else if nb != 0 && nb != 2 {
+                if has_ident {
+                    return vec![(TokenKind::Ident, start, pos), (TokenKind::Colon, pos, pos + nb)];
+                } else {
+                    return vec![(TokenKind::Colon, start, pos + nb)];
+                }
+            }
+
+            if let Some((None, text)) = self.tokens.peek().map(|(token, text)| {
+                if *token == TokenKind::Ident {
+                    let class = get_real_ident_class(text, edition, true);
+                    (class, text)
+                } else {
+                    // Doesn't matter which Class we put in here...
+                    (Some(Class::Comment), text)
+                }
+            }) {
+                // We only "add" the colon if there is an ident behind.
+                pos += text.len() + nb;
+                has_ident = true;
+                self.tokens.next();
+            } else if nb > 0 && has_ident {
+                return vec![(TokenKind::Ident, start, pos), (TokenKind::Colon, pos, pos + nb)];
+            } else if nb > 0 {
+                return vec![(TokenKind::Colon, start, start + nb)];
+            } else if has_ident {
+                return vec![(TokenKind::Ident, start, pos)];
+            } else {
+                return Vec::new();
+            }
+        }
+    }
+
+    /// Wraps the tokens iteration to ensure that the `byte_pos` is always correct.
+    ///
+    /// It returns the token's kind, the token as a string and its byte position in the source
+    /// string.
+    fn next(&mut self) -> Option<(TokenKind, &'a str, u32)> {
+        if let Some((kind, text)) = self.tokens.next() {
+            let before = self.byte_pos;
+            self.byte_pos += text.len() as u32;
+            Some((kind, text, before))
+        } else {
+            None
+        }
+    }
+
+    /// Exhausts the `Classifier` writing the output into `sink`.
+    ///
+    /// The general structure for this method is to iterate over each token,
+    /// possibly giving it an HTML span with a class specifying what flavor of
+    /// token is used.
+    fn highlight(mut self, sink: &mut dyn FnMut(Highlight<'a>)) {
+        loop {
+            if let Some(decs) = self.decorations.as_mut() {
+                let byte_pos = self.byte_pos;
+                let n_starts = decs.starts.iter().filter(|(i, _)| byte_pos >= *i).count();
+                for (_, kind) in decs.starts.drain(0..n_starts) {
+                    sink(Highlight::EnterSpan { class: Class::Decoration(kind) });
+                }
+
+                let n_ends = decs.ends.iter().filter(|i| byte_pos >= **i).count();
+                for _ in decs.ends.drain(0..n_ends) {
+                    sink(Highlight::ExitSpan);
+                }
+            }
+
+            if self
+                .tokens
+                .peek()
+                .map(|t| matches!(t.0, TokenKind::Colon | TokenKind::Ident))
+                .unwrap_or(false)
+            {
+                let tokens = self.get_full_ident_path();
+                for (token, start, end) in &tokens {
+                    let text = &self.src[*start..*end];
+                    self.advance(*token, text, sink, *start as u32);
+                    self.byte_pos += text.len() as u32;
+                }
+                if !tokens.is_empty() {
+                    continue;
+                }
+            }
+            if let Some((token, text, before)) = self.next() {
+                self.advance(token, text, sink, before);
+            } else {
+                break;
+            }
+        }
+    }
+
+    /// Single step of highlighting. This will classify `token`, but maybe also a couple of
+    /// following ones as well.
+    ///
+    /// `before` is the position of the given token in the `source` string and is used as "lo" byte
+    /// in case we want to try to generate a link for this token using the
+    /// `span_correspondance_map`.
+    fn advance(
+        &mut self,
+        token: TokenKind,
+        text: &'a str,
+        sink: &mut dyn FnMut(Highlight<'a>),
+        before: u32,
+    ) {
+        let lookahead = self.peek();
+        let no_highlight = |sink: &mut dyn FnMut(_)| sink(Highlight::Token { text, class: None });
+        let class = match token {
+            TokenKind::Whitespace => return no_highlight(sink),
+            TokenKind::LineComment { doc_style } | TokenKind::BlockComment { doc_style, .. } => {
+                if doc_style.is_some() {
+                    Class::DocComment
+                } else {
+                    Class::Comment
+                }
+            }
+            // Consider this as part of a macro invocation if there was a
+            // leading identifier.
+            TokenKind::Bang if self.in_macro => {
+                self.in_macro = false;
+                sink(Highlight::Token { text, class: None });
+                sink(Highlight::ExitSpan);
+                return;
+            }
+
+            // Assume that '&' or '*' is the reference or dereference operator
+            // or a reference or pointer type. Unless, of course, it looks like
+            // a logical and or a multiplication operator: `&&` or `* `.
+            TokenKind::Star => match self.tokens.peek() {
+                Some((TokenKind::Whitespace, _)) => Class::Op,
+                Some((TokenKind::Ident, "mut")) => {
+                    self.next();
+                    sink(Highlight::Token { text: "*mut", class: Some(Class::RefKeyWord) });
+                    return;
+                }
+                Some((TokenKind::Ident, "const")) => {
+                    self.next();
+                    sink(Highlight::Token { text: "*const", class: Some(Class::RefKeyWord) });
+                    return;
+                }
+                _ => Class::RefKeyWord,
+            },
+            TokenKind::And => match self.tokens.peek() {
+                Some((TokenKind::And, _)) => {
+                    self.next();
+                    sink(Highlight::Token { text: "&&", class: Some(Class::Op) });
+                    return;
+                }
+                Some((TokenKind::Eq, _)) => {
+                    self.next();
+                    sink(Highlight::Token { text: "&=", class: Some(Class::Op) });
+                    return;
+                }
+                Some((TokenKind::Whitespace, _)) => Class::Op,
+                Some((TokenKind::Ident, "mut")) => {
+                    self.next();
+                    sink(Highlight::Token { text: "&mut", class: Some(Class::RefKeyWord) });
+                    return;
+                }
+                _ => Class::RefKeyWord,
+            },
+
+            // These can either be operators, or arrows.
+            TokenKind::Eq => match lookahead {
+                Some(TokenKind::Eq) => {
+                    self.next();
+                    sink(Highlight::Token { text: "==", class: Some(Class::Op) });
+                    return;
+                }
+                Some(TokenKind::Gt) => {
+                    self.next();
+                    sink(Highlight::Token { text: "=>", class: None });
+                    return;
+                }
+                _ => Class::Op,
+            },
+            TokenKind::Minus if lookahead == Some(TokenKind::Gt) => {
+                self.next();
+                sink(Highlight::Token { text: "->", class: None });
+                return;
+            }
+
+            // Other operators.
+            TokenKind::Minus
+            | TokenKind::Plus
+            | TokenKind::Or
+            | TokenKind::Slash
+            | TokenKind::Caret
+            | TokenKind::Percent
+            | TokenKind::Bang
+            | TokenKind::Lt
+            | TokenKind::Gt => Class::Op,
+
+            // Miscellaneous, no highlighting.
+            TokenKind::Dot
+            | TokenKind::Semi
+            | TokenKind::Comma
+            | TokenKind::OpenParen
+            | TokenKind::CloseParen
+            | TokenKind::OpenBrace
+            | TokenKind::CloseBrace
+            | TokenKind::OpenBracket
+            | TokenKind::At
+            | TokenKind::Tilde
+            | TokenKind::Colon
+            | TokenKind::Unknown => return no_highlight(sink),
+
+            TokenKind::Question => Class::QuestionMark,
+
+            TokenKind::Dollar => match lookahead {
+                Some(TokenKind::Ident) => {
+                    self.in_macro_nonterminal = true;
+                    Class::MacroNonTerminal
+                }
+                _ => return no_highlight(sink),
+            },
+
+            // This might be the start of an attribute. We're going to want to
+            // continue highlighting it as an attribute until the ending ']' is
+            // seen, so skip out early. Down below we terminate the attribute
+            // span when we see the ']'.
+            TokenKind::Pound => {
+                match lookahead {
+                    // Case 1: #![inner_attribute]
+                    Some(TokenKind::Bang) => {
+                        self.next();
+                        if let Some(TokenKind::OpenBracket) = self.peek() {
+                            self.in_attribute = true;
+                            sink(Highlight::EnterSpan { class: Class::Attribute });
+                        }
+                        sink(Highlight::Token { text: "#", class: None });
+                        sink(Highlight::Token { text: "!", class: None });
+                        return;
+                    }
+                    // Case 2: #[outer_attribute]
+                    Some(TokenKind::OpenBracket) => {
+                        self.in_attribute = true;
+                        sink(Highlight::EnterSpan { class: Class::Attribute });
+                    }
+                    _ => (),
+                }
+                return no_highlight(sink);
+            }
+            TokenKind::CloseBracket => {
+                if self.in_attribute {
+                    self.in_attribute = false;
+                    sink(Highlight::Token { text: "]", class: None });
+                    sink(Highlight::ExitSpan);
+                    return;
+                }
+                return no_highlight(sink);
+            }
+            TokenKind::Literal { kind, .. } => match kind {
+                // Text literals.
+                LiteralKind::Byte { .. }
+                | LiteralKind::Char { .. }
+                | LiteralKind::Str { .. }
+                | LiteralKind::ByteStr { .. }
+                | LiteralKind::RawStr { .. }
+                | LiteralKind::RawByteStr { .. } => Class::String,
+                // Number literals.
+                LiteralKind::Float { .. } | LiteralKind::Int { .. } => Class::Number,
+            },
+            TokenKind::Ident | TokenKind::RawIdent if lookahead == Some(TokenKind::Bang) => {
+                self.in_macro = true;
+                sink(Highlight::EnterSpan { class: Class::Macro(self.new_span(before, text)) });
+                sink(Highlight::Token { text, class: None });
+                return;
+            }
+            TokenKind::Ident => match get_real_ident_class(text, self.edition, false) {
+                None => match text {
+                    "Option" | "Result" => Class::PreludeTy,
+                    "Some" | "None" | "Ok" | "Err" => Class::PreludeVal,
+                    // "union" is a weak keyword and is only considered as a keyword when declaring
+                    // a union type.
+                    "union" if self.check_if_is_union_keyword() => Class::KeyWord,
+                    _ if self.in_macro_nonterminal => {
+                        self.in_macro_nonterminal = false;
+                        Class::MacroNonTerminal
+                    }
+                    "self" | "Self" => Class::Self_(self.new_span(before, text)),
+                    _ => Class::Ident(self.new_span(before, text)),
+                },
+                Some(c) => c,
+            },
+            TokenKind::RawIdent | TokenKind::UnknownPrefix | TokenKind::InvalidIdent => {
+                Class::Ident(self.new_span(before, text))
+            }
+            TokenKind::Lifetime { .. } => Class::Lifetime,
+        };
+        // Anything that didn't return above is the simple case where we the
+        // class just spans a single token, so we can use the `string` method.
+        sink(Highlight::Token { text, class: Some(class) });
+    }
+
+    fn peek(&mut self) -> Option<TokenKind> {
+        self.tokens.peek().map(|(token_kind, _text)| *token_kind)
+    }
+
+    fn check_if_is_union_keyword(&mut self) -> bool {
+        while let Some(kind) = self.tokens.peek_next().map(|(token_kind, _text)| token_kind) {
+            if *kind == TokenKind::Whitespace {
+                continue;
+            }
+            return *kind == TokenKind::Ident;
+        }
+        false
+    }
+}
+
+/// Called when we start processing a span of text that should be highlighted.
+/// The `Class` argument specifies how it should be highlighted.
+fn enter_span(
+    out: &mut Buffer,
+    klass: Class,
+    href_context: &Option<HrefContext<'_, '_, '_>>,
+) -> &'static str {
+    string_without_closing_tag(out, "", Some(klass), href_context).expect(
+        "internal error: enter_span was called with Some(klass) but did not return a \
+            closing HTML tag",
+    )
+}
+
+/// Called at the end of a span of highlighted text.
+fn exit_span(out: &mut Buffer, closing_tag: &str) {
+    out.write_str(closing_tag);
+}
+
+/// Called for a span of text. If the text should be highlighted differently
+/// from the surrounding text, then the `Class` argument will be a value other
+/// than `None`.
+///
+/// The following sequences of callbacks are equivalent:
+/// ```plain
+///     enter_span(Foo), string("text", None), exit_span()
+///     string("text", Foo)
+/// ```
+///
+/// The latter can be thought of as a shorthand for the former, which is more
+/// flexible.
+///
+/// Note that if `context` is not `None` and that the given `klass` contains a `Span`, the function
+/// will then try to find this `span` in the `span_correspondance_map`. If found, it'll then
+/// generate a link for this element (which corresponds to where its definition is located).
+fn string<T: Display>(
+    out: &mut Buffer,
+    text: T,
+    klass: Option<Class>,
+    href_context: &Option<HrefContext<'_, '_, '_>>,
+) {
+    if let Some(closing_tag) = string_without_closing_tag(out, text, klass, href_context) {
+        out.write_str(closing_tag);
+    }
+}
+
+/// This function writes `text` into `out` with some modifications depending on `klass`:
+///
+/// * If `klass` is `None`, `text` is written into `out` with no modification.
+/// * If `klass` is `Some` but `klass.get_span()` is `None`, it writes the text wrapped in a
+///   `<span>` with the provided `klass`.
+/// * If `klass` is `Some` and has a [`rustc_span::Span`], it then tries to generate a link (`<a>`
+///   element) by retrieving the link information from the `span_correspondance_map` that was filled
+///   in `span_map.rs::collect_spans_and_sources`. If it cannot retrieve the information, then it's
+///   the same as the second point (`klass` is `Some` but doesn't have a [`rustc_span::Span`]).
+fn string_without_closing_tag<T: Display>(
+    out: &mut Buffer,
+    text: T,
+    klass: Option<Class>,
+    href_context: &Option<HrefContext<'_, '_, '_>>,
+) -> Option<&'static str> {
+    let Some(klass) = klass
+    else {
+        write!(out, "{}", text);
+        return None;
+    };
+    let Some(def_span) = klass.get_span()
+    else {
+        write!(out, "<span class=\"{}\">{}", klass.as_html(), text);
+        return Some("</span>");
+    };
+
+    let mut text_s = text.to_string();
+    if text_s.contains("::") {
+        text_s = text_s.split("::").intersperse("::").fold(String::new(), |mut path, t| {
+            match t {
+                "self" | "Self" => write!(
+                    &mut path,
+                    "<span class=\"{}\">{}</span>",
+                    Class::Self_(DUMMY_SP).as_html(),
+                    t
+                ),
+                "crate" | "super" => {
+                    write!(&mut path, "<span class=\"{}\">{}</span>", Class::KeyWord.as_html(), t)
+                }
+                t => write!(&mut path, "{}", t),
+            }
+            .expect("Failed to build source HTML path");
+            path
+        });
+    }
+    if let Some(href_context) = href_context {
+        if let Some(href) =
+            href_context.context.shared.span_correspondance_map.get(&def_span).and_then(|href| {
+                let context = href_context.context;
+                // FIXME: later on, it'd be nice to provide two links (if possible) for all items:
+                // one to the documentation page and one to the source definition.
+                // FIXME: currently, external items only generate a link to their documentation,
+                // a link to their definition can be generated using this:
+                // https://github.com/rust-lang/rust/blob/60f1a2fc4b535ead9c85ce085fdce49b1b097531/src/librustdoc/html/render/context.rs#L315-L338
+                match href {
+                    LinkFromSrc::Local(span) => context
+                        .href_from_span(*span, true)
+                        .map(|s| format!("{}{}", href_context.root_path, s)),
+                    LinkFromSrc::External(def_id) => {
+                        format::href_with_root_path(*def_id, context, Some(href_context.root_path))
+                            .ok()
+                            .map(|(url, _, _)| url)
+                    }
+                    LinkFromSrc::Primitive(prim) => format::href_with_root_path(
+                        PrimitiveType::primitive_locations(context.tcx())[prim],
+                        context,
+                        Some(href_context.root_path),
+                    )
+                    .ok()
+                    .map(|(url, _, _)| url),
+                }
+            })
+        {
+            write!(out, "<a class=\"{}\" href=\"{}\">{}", klass.as_html(), href, text_s);
+            return Some("</a>");
+        }
+    }
+    write!(out, "<span class=\"{}\">{}", klass.as_html(), text_s);
+    Some("</span>")
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/html/highlight/fixtures/decorations.html b/src/librustdoc/html/highlight/fixtures/decorations.html
new file mode 100644
index 000000000..45f567880
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/decorations.html
@@ -0,0 +1,2 @@
+<span class="example"><span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">1</span>;</span>
+<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="number">2</span>;
\ No newline at end of file
diff --git a/src/librustdoc/html/highlight/fixtures/dos_line.html b/src/librustdoc/html/highlight/fixtures/dos_line.html
new file mode 100644
index 000000000..1c8dbffe7
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/dos_line.html
@@ -0,0 +1,3 @@
+<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">foo</span>() {
+<span class="macro">println!</span>(<span class="string">&quot;foo&quot;</span>);
+}
diff --git a/src/librustdoc/html/highlight/fixtures/highlight.html b/src/librustdoc/html/highlight/fixtures/highlight.html
new file mode 100644
index 000000000..abc2db179
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/highlight.html
@@ -0,0 +1,4 @@
+<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::a::foo</span>;
+<span class="kw">use</span> <span class="ident"><span class="self">self</span>::whatever</span>;
+<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident"><span class="kw">super</span>::b::foo</span>;
+<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::whatever</span>;
\ No newline at end of file
diff --git a/src/librustdoc/html/highlight/fixtures/sample.html b/src/librustdoc/html/highlight/fixtures/sample.html
new file mode 100644
index 000000000..b117a12e3
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/sample.html
@@ -0,0 +1,37 @@
+
+<style>
+.kw { color: #8959A8; }
+.kw-2, .prelude-ty { color: #4271AE; }
+.number, .string { color: #718C00; }
+.self, .bool-val, .prelude-val, .attribute, .attribute .ident { color: #C82829; }
+.macro, .macro-nonterminal { color: #3E999F; }
+.lifetime { color: #B76514; }
+.question-mark { color: #ff9011; }
+</style>
+<pre><code><span class="attribute">#![<span class="ident">crate_type</span> <span class="op">=</span> <span class="string">&quot;lib&quot;</span>]</span>
+
+<span class="kw">use</span> <span class="ident">std::path</span>::{<span class="ident">Path</span>, <span class="ident">PathBuf</span>};
+
+<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">&quot;linux&quot;</span>)]</span>
+<span class="kw">fn</span> <span class="ident">main</span>() -&gt; () {
+    <span class="kw">let</span> <span class="ident">foo</span> <span class="op">=</span> <span class="bool-val">true</span> <span class="op">&amp;&amp;</span> <span class="bool-val">false</span> <span class="op">|</span><span class="op">|</span> <span class="bool-val">true</span>;
+    <span class="kw">let</span> <span class="kw">_</span>: <span class="kw-2">*const</span> () <span class="op">=</span> <span class="number">0</span>;
+    <span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="ident">foo</span>;
+    <span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="op">&amp;&amp;</span><span class="ident">foo</span>;
+    <span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">foo</span>;
+    <span class="macro">mac!</span>(<span class="ident">foo</span>, <span class="kw-2">&amp;mut</span> <span class="ident">bar</span>);
+    <span class="macro">assert!</span>(<span class="self">self</span>.<span class="ident">length</span> <span class="op">&lt;</span> <span class="ident">N</span> <span class="op">&amp;&amp;</span> <span class="ident">index</span> <span class="op">&lt;</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">length</span>);
+    <span class="ident">::std::env::var</span>(<span class="string">&quot;gateau&quot;</span>).<span class="ident">is_ok</span>();
+    <span class="attribute">#[<span class="ident">rustfmt::skip</span>]</span>
+    <span class="kw">let</span> <span class="ident">s</span>:<span class="ident">std::path::PathBuf</span> <span class="op">=</span> <span class="ident">std::path::PathBuf::new</span>();
+    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">String::new</span>();
+
+    <span class="kw">match</span> <span class="kw-2">&amp;</span><span class="ident">s</span> {
+        <span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span> =&gt; {}
+    }
+}
+
+<span class="macro">macro_rules!</span> <span class="ident">bar</span> {
+    (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">foo</span>:<span class="ident">tt</span>) =&gt; {};
+}
+</code></pre>
diff --git a/src/librustdoc/html/highlight/fixtures/sample.rs b/src/librustdoc/html/highlight/fixtures/sample.rs
new file mode 100644
index 000000000..fbfdc6767
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/sample.rs
@@ -0,0 +1,26 @@
+#![crate_type = "lib"]
+
+use std::path::{Path, PathBuf};
+
+#[cfg(target_os = "linux")]
+fn main() -> () {
+    let foo = true && false || true;
+    let _: *const () = 0;
+    let _ = &foo;
+    let _ = &&foo;
+    let _ = *foo;
+    mac!(foo, &mut bar);
+    assert!(self.length < N && index <= self.length);
+    ::std::env::var("gateau").is_ok();
+    #[rustfmt::skip]
+    let s:std::path::PathBuf = std::path::PathBuf::new();
+    let mut s = String::new();
+
+    match &s {
+        ref mut x => {}
+    }
+}
+
+macro_rules! bar {
+    ($foo:tt) => {};
+}
diff --git a/src/librustdoc/html/highlight/fixtures/union.html b/src/librustdoc/html/highlight/fixtures/union.html
new file mode 100644
index 000000000..c0acf31a0
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/union.html
@@ -0,0 +1,8 @@
+<span class="kw">union</span> <span class="ident">Foo</span> {
+    <span class="ident">i</span>: <span class="ident">i8</span>,
+    <span class="ident">u</span>: <span class="ident">i8</span>,
+}
+
+<span class="kw">fn</span> <span class="ident">main</span>() {
+    <span class="kw">let</span> <span class="ident">union</span> <span class="op">=</span> <span class="number">0</span>;
+}
diff --git a/src/librustdoc/html/highlight/fixtures/union.rs b/src/librustdoc/html/highlight/fixtures/union.rs
new file mode 100644
index 000000000..269ee115d
--- /dev/null
+++ b/src/librustdoc/html/highlight/fixtures/union.rs
@@ -0,0 +1,8 @@
+union Foo {
+    i: i8,
+    u: i8,
+}
+
+fn main() {
+    let union = 0;
+}
diff --git a/src/librustdoc/html/highlight/tests.rs b/src/librustdoc/html/highlight/tests.rs
new file mode 100644
index 000000000..1fea7e983
--- /dev/null
+++ b/src/librustdoc/html/highlight/tests.rs
@@ -0,0 +1,81 @@
+use super::{write_code, DecorationInfo};
+use crate::html::format::Buffer;
+use expect_test::expect_file;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_span::create_default_session_globals_then;
+use rustc_span::edition::Edition;
+
+const STYLE: &str = r#"
+<style>
+.kw { color: #8959A8; }
+.kw-2, .prelude-ty { color: #4271AE; }
+.number, .string { color: #718C00; }
+.self, .bool-val, .prelude-val, .attribute, .attribute .ident { color: #C82829; }
+.macro, .macro-nonterminal { color: #3E999F; }
+.lifetime { color: #B76514; }
+.question-mark { color: #ff9011; }
+</style>
+"#;
+
+#[test]
+fn test_html_highlighting() {
+    create_default_session_globals_then(|| {
+        let src = include_str!("fixtures/sample.rs");
+        let html = {
+            let mut out = Buffer::new();
+            write_code(&mut out, src, Edition::Edition2018, None, None);
+            format!("{}<pre><code>{}</code></pre>\n", STYLE, out.into_inner())
+        };
+        expect_file!["fixtures/sample.html"].assert_eq(&html);
+    });
+}
+
+#[test]
+fn test_dos_backline() {
+    create_default_session_globals_then(|| {
+        let src = "pub fn foo() {\r\n\
+    println!(\"foo\");\r\n\
+}\r\n";
+        let mut html = Buffer::new();
+        write_code(&mut html, src, Edition::Edition2018, None, None);
+        expect_file!["fixtures/dos_line.html"].assert_eq(&html.into_inner());
+    });
+}
+
+#[test]
+fn test_keyword_highlight() {
+    create_default_session_globals_then(|| {
+        let src = "use crate::a::foo;
+use self::whatever;
+let x = super::b::foo;
+let y = Self::whatever;";
+
+        let mut html = Buffer::new();
+        write_code(&mut html, src, Edition::Edition2018, None, None);
+        expect_file!["fixtures/highlight.html"].assert_eq(&html.into_inner());
+    });
+}
+
+#[test]
+fn test_union_highlighting() {
+    create_default_session_globals_then(|| {
+        let src = include_str!("fixtures/union.rs");
+        let mut html = Buffer::new();
+        write_code(&mut html, src, Edition::Edition2018, None, None);
+        expect_file!["fixtures/union.html"].assert_eq(&html.into_inner());
+    });
+}
+
+#[test]
+fn test_decorations() {
+    create_default_session_globals_then(|| {
+        let src = "let x = 1;
+let y = 2;";
+        let mut decorations = FxHashMap::default();
+        decorations.insert("example", vec![(0, 10)]);
+
+        let mut html = Buffer::new();
+        write_code(&mut html, src, Edition::Edition2018, None, Some(DecorationInfo(decorations)));
+        expect_file!["fixtures/decorations.html"].assert_eq(&html.into_inner());
+    });
+}
diff --git a/src/librustdoc/html/layout.rs b/src/librustdoc/html/layout.rs
new file mode 100644
index 000000000..7d6d4b71e
--- /dev/null
+++ b/src/librustdoc/html/layout.rs
@@ -0,0 +1,103 @@
+use std::path::PathBuf;
+
+use rustc_data_structures::fx::FxHashMap;
+
+use crate::error::Error;
+use crate::externalfiles::ExternalHtml;
+use crate::html::format::{Buffer, Print};
+use crate::html::render::{ensure_trailing_slash, StylePath};
+
+use askama::Template;
+
+#[derive(Clone)]
+pub(crate) struct Layout {
+    pub(crate) logo: String,
+    pub(crate) favicon: String,
+    pub(crate) external_html: ExternalHtml,
+    pub(crate) default_settings: FxHashMap<String, String>,
+    pub(crate) krate: String,
+    /// The given user css file which allow to customize the generated
+    /// documentation theme.
+    pub(crate) css_file_extension: Option<PathBuf>,
+    /// If true, then scrape-examples.js will be included in the output HTML file
+    pub(crate) scrape_examples_extension: bool,
+}
+
+pub(crate) struct Page<'a> {
+    pub(crate) title: &'a str,
+    pub(crate) css_class: &'a str,
+    pub(crate) root_path: &'a str,
+    pub(crate) static_root_path: Option<&'a str>,
+    pub(crate) description: &'a str,
+    pub(crate) keywords: &'a str,
+    pub(crate) resource_suffix: &'a str,
+}
+
+impl<'a> Page<'a> {
+    pub(crate) fn get_static_root_path(&self) -> &str {
+        self.static_root_path.unwrap_or(self.root_path)
+    }
+}
+
+#[derive(Template)]
+#[template(path = "page.html")]
+struct PageLayout<'a> {
+    static_root_path: &'a str,
+    page: &'a Page<'a>,
+    layout: &'a Layout,
+    themes: Vec<String>,
+    sidebar: String,
+    content: String,
+    krate_with_trailing_slash: String,
+    pub(crate) rustdoc_version: &'a str,
+}
+
+pub(crate) fn render<T: Print, S: Print>(
+    layout: &Layout,
+    page: &Page<'_>,
+    sidebar: S,
+    t: T,
+    style_files: &[StylePath],
+) -> String {
+    let static_root_path = page.get_static_root_path();
+    let krate_with_trailing_slash = ensure_trailing_slash(&layout.krate).to_string();
+    let mut themes: Vec<String> = style_files
+        .iter()
+        .map(StylePath::basename)
+        .collect::<Result<_, Error>>()
+        .unwrap_or_default();
+    themes.sort();
+    let rustdoc_version = rustc_interface::util::version_str().unwrap_or("unknown version");
+    let content = Buffer::html().to_display(t); // Note: This must happen before making the sidebar.
+    let sidebar = Buffer::html().to_display(sidebar);
+    PageLayout {
+        static_root_path,
+        page,
+        layout,
+        themes,
+        sidebar,
+        content,
+        krate_with_trailing_slash,
+        rustdoc_version,
+    }
+    .render()
+    .unwrap()
+}
+
+pub(crate) fn redirect(url: &str) -> String {
+    // <script> triggers a redirect before refresh, so this is fine.
+    format!(
+        r##"<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta http-equiv="refresh" content="0;URL={url}">
+    <title>Redirection</title>
+</head>
+<body>
+    <p>Redirecting to <a href="{url}">{url}</a>...</p>
+    <script>location.replace("{url}" + location.search + location.hash);</script>
+</body>
+</html>"##,
+        url = url,
+    )
+}
diff --git a/src/librustdoc/html/length_limit.rs b/src/librustdoc/html/length_limit.rs
new file mode 100644
index 000000000..bbdc91c8d
--- /dev/null
+++ b/src/librustdoc/html/length_limit.rs
@@ -0,0 +1,119 @@
+//! See [`HtmlWithLimit`].
+
+use std::fmt::Write;
+use std::ops::ControlFlow;
+
+use crate::html::escape::Escape;
+
+/// A buffer that allows generating HTML with a length limit.
+///
+/// This buffer ensures that:
+///
+/// * all tags are closed,
+/// * tags are closed in the reverse order of when they were opened (i.e., the correct HTML order),
+/// * no tags are left empty (e.g., `<em></em>`) due to the length limit being reached,
+/// * all text is escaped.
+#[derive(Debug)]
+pub(super) struct HtmlWithLimit {
+    buf: String,
+    len: usize,
+    limit: usize,
+    /// A list of tags that have been requested to be opened via [`Self::open_tag()`]
+    /// but have not actually been pushed to `buf` yet. This ensures that tags are not
+    /// left empty (e.g., `<em></em>`) due to the length limit being reached.
+    queued_tags: Vec<&'static str>,
+    /// A list of all tags that have been opened but not yet closed.
+    unclosed_tags: Vec<&'static str>,
+}
+
+impl HtmlWithLimit {
+    /// Create a new buffer, with a limit of `length_limit`.
+    pub(super) fn new(length_limit: usize) -> Self {
+        let buf = if length_limit > 1000 {
+            // If the length limit is really large, don't preallocate tons of memory.
+            String::new()
+        } else {
+            // The length limit is actually a good heuristic for initial allocation size.
+            // Measurements showed that using it as the initial capacity ended up using less memory
+            // than `String::new`.
+            // See https://github.com/rust-lang/rust/pull/88173#discussion_r692531631 for more.
+            String::with_capacity(length_limit)
+        };
+        Self {
+            buf,
+            len: 0,
+            limit: length_limit,
+            unclosed_tags: Vec::new(),
+            queued_tags: Vec::new(),
+        }
+    }
+
+    /// Finish using the buffer and get the written output.
+    /// This function will close all unclosed tags for you.
+    pub(super) fn finish(mut self) -> String {
+        self.close_all_tags();
+        self.buf
+    }
+
+    /// Write some plain text to the buffer, escaping as needed.
+    ///
+    /// This function skips writing the text if the length limit was reached
+    /// and returns [`ControlFlow::Break`].
+    pub(super) fn push(&mut self, text: &str) -> ControlFlow<(), ()> {
+        if self.len + text.len() > self.limit {
+            return ControlFlow::BREAK;
+        }
+
+        self.flush_queue();
+        write!(self.buf, "{}", Escape(text)).unwrap();
+        self.len += text.len();
+
+        ControlFlow::CONTINUE
+    }
+
+    /// Open an HTML tag.
+    ///
+    /// **Note:** HTML attributes have not yet been implemented.
+    /// This function will panic if called with a non-alphabetic `tag_name`.
+    pub(super) fn open_tag(&mut self, tag_name: &'static str) {
+        assert!(
+            tag_name.chars().all(|c| ('a'..='z').contains(&c)),
+            "tag_name contained non-alphabetic chars: {:?}",
+            tag_name
+        );
+        self.queued_tags.push(tag_name);
+    }
+
+    /// Close the most recently opened HTML tag.
+    pub(super) fn close_tag(&mut self) {
+        match self.unclosed_tags.pop() {
+            // Close the most recently opened tag.
+            Some(tag_name) => write!(self.buf, "</{}>", tag_name).unwrap(),
+            // There are valid cases where `close_tag()` is called without
+            // there being any tags to close. For example, this occurs when
+            // a tag is opened after the length limit is exceeded;
+            // `flush_queue()` will never be called, and thus, the tag will
+            // not end up being added to `unclosed_tags`.
+            None => {}
+        }
+    }
+
+    /// Write all queued tags and add them to the `unclosed_tags` list.
+    fn flush_queue(&mut self) {
+        for tag_name in self.queued_tags.drain(..) {
+            write!(self.buf, "<{}>", tag_name).unwrap();
+
+            self.unclosed_tags.push(tag_name);
+        }
+    }
+
+    /// Close all unclosed tags.
+    fn close_all_tags(&mut self) {
+        while !self.unclosed_tags.is_empty() {
+            self.close_tag();
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/html/length_limit/tests.rs b/src/librustdoc/html/length_limit/tests.rs
new file mode 100644
index 000000000..2d02b8a16
--- /dev/null
+++ b/src/librustdoc/html/length_limit/tests.rs
@@ -0,0 +1,120 @@
+use super::*;
+
+#[test]
+fn empty() {
+    assert_eq!(HtmlWithLimit::new(0).finish(), "");
+    assert_eq!(HtmlWithLimit::new(60).finish(), "");
+}
+
+#[test]
+fn basic() {
+    let mut buf = HtmlWithLimit::new(60);
+    buf.push("Hello ");
+    buf.open_tag("em");
+    buf.push("world");
+    buf.close_tag();
+    buf.push("!");
+    assert_eq!(buf.finish(), "Hello <em>world</em>!");
+}
+
+#[test]
+fn no_tags() {
+    let mut buf = HtmlWithLimit::new(60);
+    buf.push("Hello");
+    buf.push(" world!");
+    assert_eq!(buf.finish(), "Hello world!");
+}
+
+#[test]
+fn limit_0() {
+    let mut buf = HtmlWithLimit::new(0);
+    buf.push("Hello ");
+    buf.open_tag("em");
+    buf.push("world");
+    buf.close_tag();
+    buf.push("!");
+    assert_eq!(buf.finish(), "");
+}
+
+#[test]
+fn exactly_limit() {
+    let mut buf = HtmlWithLimit::new(12);
+    buf.push("Hello ");
+    buf.open_tag("em");
+    buf.push("world");
+    buf.close_tag();
+    buf.push("!");
+    assert_eq!(buf.finish(), "Hello <em>world</em>!");
+}
+
+#[test]
+fn multiple_nested_tags() {
+    let mut buf = HtmlWithLimit::new(60);
+    buf.open_tag("p");
+    buf.push("This is a ");
+    buf.open_tag("em");
+    buf.push("paragraph");
+    buf.open_tag("strong");
+    buf.push("!");
+    buf.close_tag();
+    buf.close_tag();
+    buf.close_tag();
+    assert_eq!(buf.finish(), "<p>This is a <em>paragraph<strong>!</strong></em></p>");
+}
+
+#[test]
+fn forgot_to_close_tags() {
+    let mut buf = HtmlWithLimit::new(60);
+    buf.open_tag("p");
+    buf.push("This is a ");
+    buf.open_tag("em");
+    buf.push("paragraph");
+    buf.open_tag("strong");
+    buf.push("!");
+    assert_eq!(buf.finish(), "<p>This is a <em>paragraph<strong>!</strong></em></p>");
+}
+
+#[test]
+fn past_the_limit() {
+    let mut buf = HtmlWithLimit::new(20);
+    buf.open_tag("p");
+    (0..10).try_for_each(|n| {
+        buf.open_tag("strong");
+        buf.push("word#")?;
+        buf.push(&n.to_string())?;
+        buf.close_tag();
+        ControlFlow::CONTINUE
+    });
+    buf.close_tag();
+    assert_eq!(
+        buf.finish(),
+        "<p>\
+             <strong>word#0</strong>\
+             <strong>word#1</strong>\
+             <strong>word#2</strong>\
+             </p>"
+    );
+}
+
+#[test]
+fn quickly_past_the_limit() {
+    let mut buf = HtmlWithLimit::new(6);
+    buf.open_tag("p");
+    buf.push("Hello");
+    buf.push(" World");
+    // intentionally not closing <p> before finishing
+    assert_eq!(buf.finish(), "<p>Hello</p>");
+}
+
+#[test]
+fn close_too_many() {
+    let mut buf = HtmlWithLimit::new(60);
+    buf.open_tag("p");
+    buf.push("Hello");
+    buf.close_tag();
+    // This call does not panic because there are valid cases
+    // where `close_tag()` is called with no tags left to close.
+    // So `close_tag()` does nothing in this case.
+    buf.close_tag();
+    assert_eq!(buf.finish(), "<p>Hello</p>");
+}
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
new file mode 100644
index 000000000..52a2effca
--- /dev/null
+++ b/src/librustdoc/html/markdown.rs
@@ -0,0 +1,1510 @@
+//! Markdown formatting for rustdoc.
+//!
+//! This module implements markdown formatting through the pulldown-cmark library.
+//!
+//! ```
+//! #![feature(rustc_private)]
+//!
+//! extern crate rustc_span;
+//!
+//! use rustc_span::edition::Edition;
+//! use rustdoc::html::markdown::{HeadingOffset, IdMap, Markdown, ErrorCodes};
+//!
+//! let s = "My *markdown* _text_";
+//! let mut id_map = IdMap::new();
+//! let md = Markdown {
+//!     content: s,
+//!     links: &[],
+//!     ids: &mut id_map,
+//!     error_codes: ErrorCodes::Yes,
+//!     edition: Edition::Edition2015,
+//!     playground: &None,
+//!     heading_offset: HeadingOffset::H2,
+//! };
+//! let html = md.into_string();
+//! // ... something using html
+//! ```
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def_id::DefId;
+use rustc_hir::HirId;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::edition::Edition;
+use rustc_span::Span;
+
+use once_cell::sync::Lazy;
+use std::borrow::Cow;
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::default::Default;
+use std::fmt::Write;
+use std::ops::{ControlFlow, Range};
+use std::str;
+
+use crate::clean::RenderedLink;
+use crate::doctest;
+use crate::html::escape::Escape;
+use crate::html::format::Buffer;
+use crate::html::highlight;
+use crate::html::length_limit::HtmlWithLimit;
+use crate::html::toc::TocBuilder;
+
+use pulldown_cmark::{
+    html, BrokenLink, CodeBlockKind, CowStr, Event, LinkType, Options, Parser, Tag,
+};
+
+#[cfg(test)]
+mod tests;
+
+const MAX_HEADER_LEVEL: u32 = 6;
+
+/// Options for rendering Markdown in the main body of documentation.
+pub(crate) fn main_body_opts() -> Options {
+    Options::ENABLE_TABLES
+        | Options::ENABLE_FOOTNOTES
+        | Options::ENABLE_STRIKETHROUGH
+        | Options::ENABLE_TASKLISTS
+        | Options::ENABLE_SMART_PUNCTUATION
+}
+
+/// Options for rendering Markdown in summaries (e.g., in search results).
+pub(crate) fn summary_opts() -> Options {
+    Options::ENABLE_TABLES
+        | Options::ENABLE_FOOTNOTES
+        | Options::ENABLE_STRIKETHROUGH
+        | Options::ENABLE_TASKLISTS
+        | Options::ENABLE_SMART_PUNCTUATION
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum HeadingOffset {
+    H1 = 0,
+    H2,
+    H3,
+    H4,
+    H5,
+    H6,
+}
+
+/// When `to_string` is called, this struct will emit the HTML corresponding to
+/// the rendered version of the contained markdown string.
+pub struct Markdown<'a> {
+    pub content: &'a str,
+    /// A list of link replacements.
+    pub links: &'a [RenderedLink],
+    /// The current list of used header IDs.
+    pub ids: &'a mut IdMap,
+    /// Whether to allow the use of explicit error codes in doctest lang strings.
+    pub error_codes: ErrorCodes,
+    /// Default edition to use when parsing doctests (to add a `fn main`).
+    pub edition: Edition,
+    pub playground: &'a Option<Playground>,
+    /// Offset at which we render headings.
+    /// E.g. if `heading_offset: HeadingOffset::H2`, then `# something` renders an `<h2>`.
+    pub heading_offset: HeadingOffset,
+}
+/// A tuple struct like `Markdown` that renders the markdown with a table of contents.
+pub(crate) struct MarkdownWithToc<'a>(
+    pub(crate) &'a str,
+    pub(crate) &'a mut IdMap,
+    pub(crate) ErrorCodes,
+    pub(crate) Edition,
+    pub(crate) &'a Option<Playground>,
+);
+/// A tuple struct like `Markdown` that renders the markdown escaping HTML tags.
+pub(crate) struct MarkdownHtml<'a>(
+    pub(crate) &'a str,
+    pub(crate) &'a mut IdMap,
+    pub(crate) ErrorCodes,
+    pub(crate) Edition,
+    pub(crate) &'a Option<Playground>,
+);
+/// A tuple struct like `Markdown` that renders only the first paragraph.
+pub(crate) struct MarkdownSummaryLine<'a>(pub &'a str, pub &'a [RenderedLink]);
+
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum ErrorCodes {
+    Yes,
+    No,
+}
+
+impl ErrorCodes {
+    pub(crate) fn from(b: bool) -> Self {
+        match b {
+            true => ErrorCodes::Yes,
+            false => ErrorCodes::No,
+        }
+    }
+
+    pub(crate) fn as_bool(self) -> bool {
+        match self {
+            ErrorCodes::Yes => true,
+            ErrorCodes::No => false,
+        }
+    }
+}
+
+/// Controls whether a line will be hidden or shown in HTML output.
+///
+/// All lines are used in documentation tests.
+enum Line<'a> {
+    Hidden(&'a str),
+    Shown(Cow<'a, str>),
+}
+
+impl<'a> Line<'a> {
+    fn for_html(self) -> Option<Cow<'a, str>> {
+        match self {
+            Line::Shown(l) => Some(l),
+            Line::Hidden(_) => None,
+        }
+    }
+
+    fn for_code(self) -> Cow<'a, str> {
+        match self {
+            Line::Shown(l) => l,
+            Line::Hidden(l) => Cow::Borrowed(l),
+        }
+    }
+}
+
+// FIXME: There is a minor inconsistency here. For lines that start with ##, we
+// have no easy way of removing a potential single space after the hashes, which
+// is done in the single # case. This inconsistency seems okay, if non-ideal. In
+// order to fix it we'd have to iterate to find the first non-# character, and
+// then reallocate to remove it; which would make us return a String.
+fn map_line(s: &str) -> Line<'_> {
+    let trimmed = s.trim();
+    if trimmed.starts_with("##") {
+        Line::Shown(Cow::Owned(s.replacen("##", "#", 1)))
+    } else if let Some(stripped) = trimmed.strip_prefix("# ") {
+        // # text
+        Line::Hidden(stripped)
+    } else if trimmed == "#" {
+        // We cannot handle '#text' because it could be #[attr].
+        Line::Hidden("")
+    } else {
+        Line::Shown(Cow::Borrowed(s))
+    }
+}
+
+/// Convert chars from a title for an id.
+///
+/// "Hello, world!" -> "hello-world"
+fn slugify(c: char) -> Option<char> {
+    if c.is_alphanumeric() || c == '-' || c == '_' {
+        if c.is_ascii() { Some(c.to_ascii_lowercase()) } else { Some(c) }
+    } else if c.is_whitespace() && c.is_ascii() {
+        Some('-')
+    } else {
+        None
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct Playground {
+    pub crate_name: Option<String>,
+    pub url: String,
+}
+
+/// Adds syntax highlighting and playground Run buttons to Rust code blocks.
+struct CodeBlocks<'p, 'a, I: Iterator<Item = Event<'a>>> {
+    inner: I,
+    check_error_codes: ErrorCodes,
+    edition: Edition,
+    // Information about the playground if a URL has been specified, containing an
+    // optional crate name and the URL.
+    playground: &'p Option<Playground>,
+}
+
+impl<'p, 'a, I: Iterator<Item = Event<'a>>> CodeBlocks<'p, 'a, I> {
+    fn new(
+        iter: I,
+        error_codes: ErrorCodes,
+        edition: Edition,
+        playground: &'p Option<Playground>,
+    ) -> Self {
+        CodeBlocks { inner: iter, check_error_codes: error_codes, edition, playground }
+    }
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
+    type Item = Event<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let event = self.inner.next();
+        let compile_fail;
+        let should_panic;
+        let ignore;
+        let edition;
+        let Some(Event::Start(Tag::CodeBlock(kind))) = event else {
+            return event;
+        };
+
+        let mut origtext = String::new();
+        for event in &mut self.inner {
+            match event {
+                Event::End(Tag::CodeBlock(..)) => break,
+                Event::Text(ref s) => {
+                    origtext.push_str(s);
+                }
+                _ => {}
+            }
+        }
+        let lines = origtext.lines().filter_map(|l| map_line(l).for_html());
+        let text = lines.intersperse("\n".into()).collect::<String>();
+
+        let parse_result = match kind {
+            CodeBlockKind::Fenced(ref lang) => {
+                let parse_result =
+                    LangString::parse_without_check(lang, self.check_error_codes, false);
+                if !parse_result.rust {
+                    return Some(Event::Html(
+                        format!(
+                            "<div class=\"example-wrap\">\
+                                 <pre class=\"language-{}\"><code>{}</code></pre>\
+                             </div>",
+                            lang,
+                            Escape(&text),
+                        )
+                        .into(),
+                    ));
+                }
+                parse_result
+            }
+            CodeBlockKind::Indented => Default::default(),
+        };
+
+        compile_fail = parse_result.compile_fail;
+        should_panic = parse_result.should_panic;
+        ignore = parse_result.ignore;
+        edition = parse_result.edition;
+
+        let explicit_edition = edition.is_some();
+        let edition = edition.unwrap_or(self.edition);
+
+        let playground_button = self.playground.as_ref().and_then(|playground| {
+            let krate = &playground.crate_name;
+            let url = &playground.url;
+            if url.is_empty() {
+                return None;
+            }
+            let test = origtext
+                .lines()
+                .map(|l| map_line(l).for_code())
+                .intersperse("\n".into())
+                .collect::<String>();
+            let krate = krate.as_ref().map(|s| &**s);
+            let (test, _, _) =
+                doctest::make_test(&test, krate, false, &Default::default(), edition, None);
+            let channel = if test.contains("#![feature(") { "&amp;version=nightly" } else { "" };
+
+            // These characters don't need to be escaped in a URI.
+            // FIXME: use a library function for percent encoding.
+            fn dont_escape(c: u8) -> bool {
+                (b'a' <= c && c <= b'z')
+                    || (b'A' <= c && c <= b'Z')
+                    || (b'0' <= c && c <= b'9')
+                    || c == b'-'
+                    || c == b'_'
+                    || c == b'.'
+                    || c == b'~'
+                    || c == b'!'
+                    || c == b'\''
+                    || c == b'('
+                    || c == b')'
+                    || c == b'*'
+            }
+            let mut test_escaped = String::new();
+            for b in test.bytes() {
+                if dont_escape(b) {
+                    test_escaped.push(char::from(b));
+                } else {
+                    write!(test_escaped, "%{:02X}", b).unwrap();
+                }
+            }
+            Some(format!(
+                r#"<a class="test-arrow" target="_blank" href="{}?code={}{}&amp;edition={}">Run</a>"#,
+                url, test_escaped, channel, edition,
+            ))
+        });
+
+        let tooltip = if ignore != Ignore::None {
+            Some((None, "ignore"))
+        } else if compile_fail {
+            Some((None, "compile_fail"))
+        } else if should_panic {
+            Some((None, "should_panic"))
+        } else if explicit_edition {
+            Some((Some(edition), "edition"))
+        } else {
+            None
+        };
+
+        // insert newline to clearly separate it from the
+        // previous block so we can shorten the html output
+        let mut s = Buffer::new();
+        s.push_str("\n");
+        highlight::render_with_highlighting(
+            &text,
+            &mut s,
+            Some(&format!(
+                "rust-example-rendered{}",
+                if let Some((_, class)) = tooltip { format!(" {}", class) } else { String::new() }
+            )),
+            playground_button.as_deref(),
+            tooltip,
+            edition,
+            None,
+            None,
+            None,
+        );
+        Some(Event::Html(s.into_inner().into()))
+    }
+}
+
+/// Make headings links with anchor IDs and build up TOC.
+struct LinkReplacer<'a, I: Iterator<Item = Event<'a>>> {
+    inner: I,
+    links: &'a [RenderedLink],
+    shortcut_link: Option<&'a RenderedLink>,
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> LinkReplacer<'a, I> {
+    fn new(iter: I, links: &'a [RenderedLink]) -> Self {
+        LinkReplacer { inner: iter, links, shortcut_link: None }
+    }
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> Iterator for LinkReplacer<'a, I> {
+    type Item = Event<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut event = self.inner.next();
+
+        // Replace intra-doc links and remove disambiguators from shortcut links (`[fn@f]`).
+        match &mut event {
+            // This is a shortcut link that was resolved by the broken_link_callback: `[fn@f]`
+            // Remove any disambiguator.
+            Some(Event::Start(Tag::Link(
+                // [fn@f] or [fn@f][]
+                LinkType::ShortcutUnknown | LinkType::CollapsedUnknown,
+                dest,
+                title,
+            ))) => {
+                debug!("saw start of shortcut link to {} with title {}", dest, title);
+                // If this is a shortcut link, it was resolved by the broken_link_callback.
+                // So the URL will already be updated properly.
+                let link = self.links.iter().find(|&link| *link.href == **dest);
+                // Since this is an external iterator, we can't replace the inner text just yet.
+                // Store that we saw a link so we know to replace it later.
+                if let Some(link) = link {
+                    trace!("it matched");
+                    assert!(self.shortcut_link.is_none(), "shortcut links cannot be nested");
+                    self.shortcut_link = Some(link);
+                }
+            }
+            // Now that we're done with the shortcut link, don't replace any more text.
+            Some(Event::End(Tag::Link(
+                LinkType::ShortcutUnknown | LinkType::CollapsedUnknown,
+                dest,
+                _,
+            ))) => {
+                debug!("saw end of shortcut link to {}", dest);
+                if self.links.iter().any(|link| *link.href == **dest) {
+                    assert!(self.shortcut_link.is_some(), "saw closing link without opening tag");
+                    self.shortcut_link = None;
+                }
+            }
+            // Handle backticks in inline code blocks, but only if we're in the middle of a shortcut link.
+            // [`fn@f`]
+            Some(Event::Code(text)) => {
+                trace!("saw code {}", text);
+                if let Some(link) = self.shortcut_link {
+                    trace!("original text was {}", link.original_text);
+                    // NOTE: this only replaces if the code block is the *entire* text.
+                    // If only part of the link has code highlighting, the disambiguator will not be removed.
+                    // e.g. [fn@`f`]
+                    // This is a limitation from `collect_intra_doc_links`: it passes a full link,
+                    // and does not distinguish at all between code blocks.
+                    // So we could never be sure we weren't replacing too much:
+                    // [fn@my_`f`unc] is treated the same as [my_func()] in that pass.
+                    //
+                    // NOTE: &[1..len() - 1] is to strip the backticks
+                    if **text == link.original_text[1..link.original_text.len() - 1] {
+                        debug!("replacing {} with {}", text, link.new_text);
+                        *text = CowStr::Borrowed(&link.new_text);
+                    }
+                }
+            }
+            // Replace plain text in links, but only in the middle of a shortcut link.
+            // [fn@f]
+            Some(Event::Text(text)) => {
+                trace!("saw text {}", text);
+                if let Some(link) = self.shortcut_link {
+                    trace!("original text was {}", link.original_text);
+                    // NOTE: same limitations as `Event::Code`
+                    if **text == *link.original_text {
+                        debug!("replacing {} with {}", text, link.new_text);
+                        *text = CowStr::Borrowed(&link.new_text);
+                    }
+                }
+            }
+            // If this is a link, but not a shortcut link,
+            // replace the URL, since the broken_link_callback was not called.
+            Some(Event::Start(Tag::Link(_, dest, _))) => {
+                if let Some(link) = self.links.iter().find(|&link| *link.original_text == **dest) {
+                    *dest = CowStr::Borrowed(link.href.as_ref());
+                }
+            }
+            // Anything else couldn't have been a valid Rust path, so no need to replace the text.
+            _ => {}
+        }
+
+        // Yield the modified event
+        event
+    }
+}
+
+/// Wrap HTML tables into `<div>` to prevent having the doc blocks width being too big.
+struct TableWrapper<'a, I: Iterator<Item = Event<'a>>> {
+    inner: I,
+    stored_events: VecDeque<Event<'a>>,
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> TableWrapper<'a, I> {
+    fn new(iter: I) -> Self {
+        Self { inner: iter, stored_events: VecDeque::new() }
+    }
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> Iterator for TableWrapper<'a, I> {
+    type Item = Event<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(first) = self.stored_events.pop_front() {
+            return Some(first);
+        }
+
+        let event = self.inner.next()?;
+
+        Some(match event {
+            Event::Start(Tag::Table(t)) => {
+                self.stored_events.push_back(Event::Start(Tag::Table(t)));
+                Event::Html(CowStr::Borrowed("<div>"))
+            }
+            Event::End(Tag::Table(t)) => {
+                self.stored_events.push_back(Event::Html(CowStr::Borrowed("</div>")));
+                Event::End(Tag::Table(t))
+            }
+            e => e,
+        })
+    }
+}
+
+type SpannedEvent<'a> = (Event<'a>, Range<usize>);
+
+/// Make headings links with anchor IDs and build up TOC.
+struct HeadingLinks<'a, 'b, 'ids, I> {
+    inner: I,
+    toc: Option<&'b mut TocBuilder>,
+    buf: VecDeque<SpannedEvent<'a>>,
+    id_map: &'ids mut IdMap,
+    heading_offset: HeadingOffset,
+}
+
+impl<'a, 'b, 'ids, I> HeadingLinks<'a, 'b, 'ids, I> {
+    fn new(
+        iter: I,
+        toc: Option<&'b mut TocBuilder>,
+        ids: &'ids mut IdMap,
+        heading_offset: HeadingOffset,
+    ) -> Self {
+        HeadingLinks { inner: iter, toc, buf: VecDeque::new(), id_map: ids, heading_offset }
+    }
+}
+
+impl<'a, 'b, 'ids, I: Iterator<Item = SpannedEvent<'a>>> Iterator
+    for HeadingLinks<'a, 'b, 'ids, I>
+{
+    type Item = SpannedEvent<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(e) = self.buf.pop_front() {
+            return Some(e);
+        }
+
+        let event = self.inner.next();
+        if let Some((Event::Start(Tag::Heading(level, _, _)), _)) = event {
+            let mut id = String::new();
+            for event in &mut self.inner {
+                match &event.0 {
+                    Event::End(Tag::Heading(..)) => break,
+                    Event::Start(Tag::Link(_, _, _)) | Event::End(Tag::Link(..)) => {}
+                    Event::Text(text) | Event::Code(text) => {
+                        id.extend(text.chars().filter_map(slugify));
+                        self.buf.push_back(event);
+                    }
+                    _ => self.buf.push_back(event),
+                }
+            }
+            let id = self.id_map.derive(id);
+
+            if let Some(ref mut builder) = self.toc {
+                let mut html_header = String::new();
+                html::push_html(&mut html_header, self.buf.iter().map(|(ev, _)| ev.clone()));
+                let sec = builder.push(level as u32, html_header, id.clone());
+                self.buf.push_front((Event::Html(format!("{} ", sec).into()), 0..0));
+            }
+
+            let level =
+                std::cmp::min(level as u32 + (self.heading_offset as u32), MAX_HEADER_LEVEL);
+            self.buf.push_back((Event::Html(format!("</a></h{}>", level).into()), 0..0));
+
+            let start_tags = format!(
+                "<h{level} id=\"{id}\">\
+                    <a href=\"#{id}\">",
+                id = id,
+                level = level
+            );
+            return Some((Event::Html(start_tags.into()), 0..0));
+        }
+        event
+    }
+}
+
+/// Extracts just the first paragraph.
+struct SummaryLine<'a, I: Iterator<Item = Event<'a>>> {
+    inner: I,
+    started: bool,
+    depth: u32,
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> SummaryLine<'a, I> {
+    fn new(iter: I) -> Self {
+        SummaryLine { inner: iter, started: false, depth: 0 }
+    }
+}
+
+fn check_if_allowed_tag(t: &Tag<'_>) -> bool {
+    matches!(
+        t,
+        Tag::Paragraph | Tag::Item | Tag::Emphasis | Tag::Strong | Tag::Link(..) | Tag::BlockQuote
+    )
+}
+
+fn is_forbidden_tag(t: &Tag<'_>) -> bool {
+    matches!(t, Tag::CodeBlock(_) | Tag::Table(_) | Tag::TableHead | Tag::TableRow | Tag::TableCell)
+}
+
+impl<'a, I: Iterator<Item = Event<'a>>> Iterator for SummaryLine<'a, I> {
+    type Item = Event<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.started && self.depth == 0 {
+            return None;
+        }
+        if !self.started {
+            self.started = true;
+        }
+        if let Some(event) = self.inner.next() {
+            let mut is_start = true;
+            let is_allowed_tag = match event {
+                Event::Start(ref c) => {
+                    if is_forbidden_tag(c) {
+                        return None;
+                    }
+                    self.depth += 1;
+                    check_if_allowed_tag(c)
+                }
+                Event::End(ref c) => {
+                    if is_forbidden_tag(c) {
+                        return None;
+                    }
+                    self.depth -= 1;
+                    is_start = false;
+                    check_if_allowed_tag(c)
+                }
+                _ => true,
+            };
+            return if !is_allowed_tag {
+                if is_start {
+                    Some(Event::Start(Tag::Paragraph))
+                } else {
+                    Some(Event::End(Tag::Paragraph))
+                }
+            } else {
+                Some(event)
+            };
+        }
+        None
+    }
+}
+
+/// Moves all footnote definitions to the end and add back links to the
+/// references.
+struct Footnotes<'a, I> {
+    inner: I,
+    footnotes: FxHashMap<String, (Vec<Event<'a>>, u16)>,
+}
+
+impl<'a, I> Footnotes<'a, I> {
+    fn new(iter: I) -> Self {
+        Footnotes { inner: iter, footnotes: FxHashMap::default() }
+    }
+
+    fn get_entry(&mut self, key: &str) -> &mut (Vec<Event<'a>>, u16) {
+        let new_id = self.footnotes.len() + 1;
+        let key = key.to_owned();
+        self.footnotes.entry(key).or_insert((Vec::new(), new_id as u16))
+    }
+}
+
+impl<'a, I: Iterator<Item = SpannedEvent<'a>>> Iterator for Footnotes<'a, I> {
+    type Item = SpannedEvent<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            match self.inner.next() {
+                Some((Event::FootnoteReference(ref reference), range)) => {
+                    let entry = self.get_entry(reference);
+                    let reference = format!(
+                        "<sup id=\"fnref{0}\"><a href=\"#fn{0}\">{0}</a></sup>",
+                        (*entry).1
+                    );
+                    return Some((Event::Html(reference.into()), range));
+                }
+                Some((Event::Start(Tag::FootnoteDefinition(def)), _)) => {
+                    let mut content = Vec::new();
+                    for (event, _) in &mut self.inner {
+                        if let Event::End(Tag::FootnoteDefinition(..)) = event {
+                            break;
+                        }
+                        content.push(event);
+                    }
+                    let entry = self.get_entry(&def);
+                    (*entry).0 = content;
+                }
+                Some(e) => return Some(e),
+                None => {
+                    if !self.footnotes.is_empty() {
+                        let mut v: Vec<_> = self.footnotes.drain().map(|(_, x)| x).collect();
+                        v.sort_by(|a, b| a.1.cmp(&b.1));
+                        let mut ret = String::from("<div class=\"footnotes\"><hr><ol>");
+                        for (mut content, id) in v {
+                            write!(ret, "<li id=\"fn{}\">", id).unwrap();
+                            let mut is_paragraph = false;
+                            if let Some(&Event::End(Tag::Paragraph)) = content.last() {
+                                content.pop();
+                                is_paragraph = true;
+                            }
+                            html::push_html(&mut ret, content.into_iter());
+                            write!(ret, "&nbsp;<a href=\"#fnref{}\">↩</a>", id).unwrap();
+                            if is_paragraph {
+                                ret.push_str("</p>");
+                            }
+                            ret.push_str("</li>");
+                        }
+                        ret.push_str("</ol></div>");
+                        return Some((Event::Html(ret.into()), 0..0));
+                    } else {
+                        return None;
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub(crate) fn find_testable_code<T: doctest::Tester>(
+    doc: &str,
+    tests: &mut T,
+    error_codes: ErrorCodes,
+    enable_per_target_ignores: bool,
+    extra_info: Option<&ExtraInfo<'_>>,
+) {
+    let mut parser = Parser::new(doc).into_offset_iter();
+    let mut prev_offset = 0;
+    let mut nb_lines = 0;
+    let mut register_header = None;
+    while let Some((event, offset)) = parser.next() {
+        match event {
+            Event::Start(Tag::CodeBlock(kind)) => {
+                let block_info = match kind {
+                    CodeBlockKind::Fenced(ref lang) => {
+                        if lang.is_empty() {
+                            Default::default()
+                        } else {
+                            LangString::parse(
+                                lang,
+                                error_codes,
+                                enable_per_target_ignores,
+                                extra_info,
+                            )
+                        }
+                    }
+                    CodeBlockKind::Indented => Default::default(),
+                };
+                if !block_info.rust {
+                    continue;
+                }
+
+                let mut test_s = String::new();
+
+                while let Some((Event::Text(s), _)) = parser.next() {
+                    test_s.push_str(&s);
+                }
+                let text = test_s
+                    .lines()
+                    .map(|l| map_line(l).for_code())
+                    .collect::<Vec<Cow<'_, str>>>()
+                    .join("\n");
+
+                nb_lines += doc[prev_offset..offset.start].lines().count();
+                // If there are characters between the preceding line ending and
+                // this code block, `str::lines` will return an additional line,
+                // which we subtract here.
+                if nb_lines != 0 && !&doc[prev_offset..offset.start].ends_with('\n') {
+                    nb_lines -= 1;
+                }
+                let line = tests.get_line() + nb_lines + 1;
+                tests.add_test(text, block_info, line);
+                prev_offset = offset.start;
+            }
+            Event::Start(Tag::Heading(level, _, _)) => {
+                register_header = Some(level as u32);
+            }
+            Event::Text(ref s) if register_header.is_some() => {
+                let level = register_header.unwrap();
+                if s.is_empty() {
+                    tests.register_header("", level);
+                } else {
+                    tests.register_header(s, level);
+                }
+                register_header = None;
+            }
+            _ => {}
+        }
+    }
+}
+
+pub(crate) struct ExtraInfo<'tcx> {
+    id: ExtraInfoId,
+    sp: Span,
+    tcx: TyCtxt<'tcx>,
+}
+
+enum ExtraInfoId {
+    Hir(HirId),
+    Def(DefId),
+}
+
+impl<'tcx> ExtraInfo<'tcx> {
+    pub(crate) fn new(tcx: TyCtxt<'tcx>, hir_id: HirId, sp: Span) -> ExtraInfo<'tcx> {
+        ExtraInfo { id: ExtraInfoId::Hir(hir_id), sp, tcx }
+    }
+
+    pub(crate) fn new_did(tcx: TyCtxt<'tcx>, did: DefId, sp: Span) -> ExtraInfo<'tcx> {
+        ExtraInfo { id: ExtraInfoId::Def(did), sp, tcx }
+    }
+
+    fn error_invalid_codeblock_attr(&self, msg: &str, help: &str) {
+        let hir_id = match self.id {
+            ExtraInfoId::Hir(hir_id) => hir_id,
+            ExtraInfoId::Def(item_did) => {
+                match item_did.as_local() {
+                    Some(item_did) => self.tcx.hir().local_def_id_to_hir_id(item_did),
+                    None => {
+                        // If non-local, no need to check anything.
+                        return;
+                    }
+                }
+            }
+        };
+        self.tcx.struct_span_lint_hir(
+            crate::lint::INVALID_CODEBLOCK_ATTRIBUTES,
+            hir_id,
+            self.sp,
+            |lint| {
+                let mut diag = lint.build(msg);
+                diag.help(help);
+                diag.emit();
+            },
+        );
+    }
+}
+
+#[derive(Eq, PartialEq, Clone, Debug)]
+pub(crate) struct LangString {
+    original: String,
+    pub(crate) should_panic: bool,
+    pub(crate) no_run: bool,
+    pub(crate) ignore: Ignore,
+    pub(crate) rust: bool,
+    pub(crate) test_harness: bool,
+    pub(crate) compile_fail: bool,
+    pub(crate) error_codes: Vec<String>,
+    pub(crate) edition: Option<Edition>,
+}
+
+#[derive(Eq, PartialEq, Clone, Debug)]
+pub(crate) enum Ignore {
+    All,
+    None,
+    Some(Vec<String>),
+}
+
+impl Default for LangString {
+    fn default() -> Self {
+        Self {
+            original: String::new(),
+            should_panic: false,
+            no_run: false,
+            ignore: Ignore::None,
+            rust: true,
+            test_harness: false,
+            compile_fail: false,
+            error_codes: Vec::new(),
+            edition: None,
+        }
+    }
+}
+
+impl LangString {
+    fn parse_without_check(
+        string: &str,
+        allow_error_code_check: ErrorCodes,
+        enable_per_target_ignores: bool,
+    ) -> LangString {
+        Self::parse(string, allow_error_code_check, enable_per_target_ignores, None)
+    }
+
+    fn tokens(string: &str) -> impl Iterator<Item = &str> {
+        // Pandoc, which Rust once used for generating documentation,
+        // expects lang strings to be surrounded by `{}` and for each token
+        // to be proceeded by a `.`. Since some of these lang strings are still
+        // loose in the wild, we strip a pair of surrounding `{}` from the lang
+        // string and a leading `.` from each token.
+
+        let string = string.trim();
+
+        let first = string.chars().next();
+        let last = string.chars().last();
+
+        let string = if first == Some('{') && last == Some('}') {
+            &string[1..string.len() - 1]
+        } else {
+            string
+        };
+
+        string
+            .split(|c| c == ',' || c == ' ' || c == '\t')
+            .map(str::trim)
+            .map(|token| token.strip_prefix('.').unwrap_or(token))
+            .filter(|token| !token.is_empty())
+    }
+
+    fn parse(
+        string: &str,
+        allow_error_code_check: ErrorCodes,
+        enable_per_target_ignores: bool,
+        extra: Option<&ExtraInfo<'_>>,
+    ) -> LangString {
+        let allow_error_code_check = allow_error_code_check.as_bool();
+        let mut seen_rust_tags = false;
+        let mut seen_other_tags = false;
+        let mut data = LangString::default();
+        let mut ignores = vec![];
+
+        data.original = string.to_owned();
+
+        for token in Self::tokens(string) {
+            match token {
+                "should_panic" => {
+                    data.should_panic = true;
+                    seen_rust_tags = !seen_other_tags;
+                }
+                "no_run" => {
+                    data.no_run = true;
+                    seen_rust_tags = !seen_other_tags;
+                }
+                "ignore" => {
+                    data.ignore = Ignore::All;
+                    seen_rust_tags = !seen_other_tags;
+                }
+                x if x.starts_with("ignore-") => {
+                    if enable_per_target_ignores {
+                        ignores.push(x.trim_start_matches("ignore-").to_owned());
+                        seen_rust_tags = !seen_other_tags;
+                    }
+                }
+                "rust" => {
+                    data.rust = true;
+                    seen_rust_tags = true;
+                }
+                "test_harness" => {
+                    data.test_harness = true;
+                    seen_rust_tags = !seen_other_tags || seen_rust_tags;
+                }
+                "compile_fail" => {
+                    data.compile_fail = true;
+                    seen_rust_tags = !seen_other_tags || seen_rust_tags;
+                    data.no_run = true;
+                }
+                x if x.starts_with("edition") => {
+                    data.edition = x[7..].parse::<Edition>().ok();
+                }
+                x if allow_error_code_check && x.starts_with('E') && x.len() == 5 => {
+                    if x[1..].parse::<u32>().is_ok() {
+                        data.error_codes.push(x.to_owned());
+                        seen_rust_tags = !seen_other_tags || seen_rust_tags;
+                    } else {
+                        seen_other_tags = true;
+                    }
+                }
+                x if extra.is_some() => {
+                    let s = x.to_lowercase();
+                    if let Some((flag, help)) = if s == "compile-fail"
+                        || s == "compile_fail"
+                        || s == "compilefail"
+                    {
+                        Some((
+                            "compile_fail",
+                            "the code block will either not be tested if not marked as a rust one \
+                             or won't fail if it compiles successfully",
+                        ))
+                    } else if s == "should-panic" || s == "should_panic" || s == "shouldpanic" {
+                        Some((
+                            "should_panic",
+                            "the code block will either not be tested if not marked as a rust one \
+                             or won't fail if it doesn't panic when running",
+                        ))
+                    } else if s == "no-run" || s == "no_run" || s == "norun" {
+                        Some((
+                            "no_run",
+                            "the code block will either not be tested if not marked as a rust one \
+                             or will be run (which you might not want)",
+                        ))
+                    } else if s == "test-harness" || s == "test_harness" || s == "testharness" {
+                        Some((
+                            "test_harness",
+                            "the code block will either not be tested if not marked as a rust one \
+                             or the code will be wrapped inside a main function",
+                        ))
+                    } else {
+                        None
+                    } {
+                        if let Some(extra) = extra {
+                            extra.error_invalid_codeblock_attr(
+                                &format!("unknown attribute `{}`. Did you mean `{}`?", x, flag),
+                                help,
+                            );
+                        }
+                    }
+                    seen_other_tags = true;
+                }
+                _ => seen_other_tags = true,
+            }
+        }
+
+        // ignore-foo overrides ignore
+        if !ignores.is_empty() {
+            data.ignore = Ignore::Some(ignores);
+        }
+
+        data.rust &= !seen_other_tags || seen_rust_tags;
+
+        data
+    }
+}
+
+impl Markdown<'_> {
+    pub fn into_string(self) -> String {
+        let Markdown {
+            content: md,
+            links,
+            ids,
+            error_codes: codes,
+            edition,
+            playground,
+            heading_offset,
+        } = self;
+
+        // This is actually common enough to special-case
+        if md.is_empty() {
+            return String::new();
+        }
+        let mut replacer = |broken_link: BrokenLink<'_>| {
+            links
+                .iter()
+                .find(|link| link.original_text.as_str() == &*broken_link.reference)
+                .map(|link| (link.href.as_str().into(), link.new_text.as_str().into()))
+        };
+
+        let p = Parser::new_with_broken_link_callback(md, main_body_opts(), Some(&mut replacer));
+        let p = p.into_offset_iter();
+
+        let mut s = String::with_capacity(md.len() * 3 / 2);
+
+        let p = HeadingLinks::new(p, None, ids, heading_offset);
+        let p = Footnotes::new(p);
+        let p = LinkReplacer::new(p.map(|(ev, _)| ev), links);
+        let p = TableWrapper::new(p);
+        let p = CodeBlocks::new(p, codes, edition, playground);
+        html::push_html(&mut s, p);
+
+        s
+    }
+}
+
+impl MarkdownWithToc<'_> {
+    pub(crate) fn into_string(self) -> String {
+        let MarkdownWithToc(md, ids, codes, edition, playground) = self;
+
+        let p = Parser::new_ext(md, main_body_opts()).into_offset_iter();
+
+        let mut s = String::with_capacity(md.len() * 3 / 2);
+
+        let mut toc = TocBuilder::new();
+
+        {
+            let p = HeadingLinks::new(p, Some(&mut toc), ids, HeadingOffset::H1);
+            let p = Footnotes::new(p);
+            let p = TableWrapper::new(p.map(|(ev, _)| ev));
+            let p = CodeBlocks::new(p, codes, edition, playground);
+            html::push_html(&mut s, p);
+        }
+
+        format!("<nav id=\"TOC\">{}</nav>{}", toc.into_toc().print(), s)
+    }
+}
+
+impl MarkdownHtml<'_> {
+    pub(crate) fn into_string(self) -> String {
+        let MarkdownHtml(md, ids, codes, edition, playground) = self;
+
+        // This is actually common enough to special-case
+        if md.is_empty() {
+            return String::new();
+        }
+        let p = Parser::new_ext(md, main_body_opts()).into_offset_iter();
+
+        // Treat inline HTML as plain text.
+        let p = p.map(|event| match event.0 {
+            Event::Html(text) => (Event::Text(text), event.1),
+            _ => event,
+        });
+
+        let mut s = String::with_capacity(md.len() * 3 / 2);
+
+        let p = HeadingLinks::new(p, None, ids, HeadingOffset::H1);
+        let p = Footnotes::new(p);
+        let p = TableWrapper::new(p.map(|(ev, _)| ev));
+        let p = CodeBlocks::new(p, codes, edition, playground);
+        html::push_html(&mut s, p);
+
+        s
+    }
+}
+
+impl MarkdownSummaryLine<'_> {
+    pub(crate) fn into_string(self) -> String {
+        let MarkdownSummaryLine(md, links) = self;
+        // This is actually common enough to special-case
+        if md.is_empty() {
+            return String::new();
+        }
+
+        let mut replacer = |broken_link: BrokenLink<'_>| {
+            links
+                .iter()
+                .find(|link| link.original_text.as_str() == &*broken_link.reference)
+                .map(|link| (link.href.as_str().into(), link.new_text.as_str().into()))
+        };
+
+        let p = Parser::new_with_broken_link_callback(md, summary_opts(), Some(&mut replacer));
+
+        let mut s = String::new();
+
+        html::push_html(&mut s, LinkReplacer::new(SummaryLine::new(p), links));
+
+        s
+    }
+}
+
+/// Renders a subset of Markdown in the first paragraph of the provided Markdown.
+///
+/// - *Italics*, **bold**, and `inline code` styles **are** rendered.
+/// - Headings and links are stripped (though the text *is* rendered).
+/// - HTML, code blocks, and everything else are ignored.
+///
+/// Returns a tuple of the rendered HTML string and whether the output was shortened
+/// due to the provided `length_limit`.
+fn markdown_summary_with_limit(
+    md: &str,
+    link_names: &[RenderedLink],
+    length_limit: usize,
+) -> (String, bool) {
+    if md.is_empty() {
+        return (String::new(), false);
+    }
+
+    let mut replacer = |broken_link: BrokenLink<'_>| {
+        link_names
+            .iter()
+            .find(|link| link.original_text.as_str() == &*broken_link.reference)
+            .map(|link| (link.href.as_str().into(), link.new_text.as_str().into()))
+    };
+
+    let p = Parser::new_with_broken_link_callback(md, summary_opts(), Some(&mut replacer));
+    let mut p = LinkReplacer::new(p, link_names);
+
+    let mut buf = HtmlWithLimit::new(length_limit);
+    let mut stopped_early = false;
+    p.try_for_each(|event| {
+        match &event {
+            Event::Text(text) => {
+                let r =
+                    text.split_inclusive(char::is_whitespace).try_for_each(|word| buf.push(word));
+                if r.is_break() {
+                    stopped_early = true;
+                }
+                return r;
+            }
+            Event::Code(code) => {
+                buf.open_tag("code");
+                let r = buf.push(code);
+                if r.is_break() {
+                    stopped_early = true;
+                } else {
+                    buf.close_tag();
+                }
+                return r;
+            }
+            Event::Start(tag) => match tag {
+                Tag::Emphasis => buf.open_tag("em"),
+                Tag::Strong => buf.open_tag("strong"),
+                Tag::CodeBlock(..) => return ControlFlow::BREAK,
+                _ => {}
+            },
+            Event::End(tag) => match tag {
+                Tag::Emphasis | Tag::Strong => buf.close_tag(),
+                Tag::Paragraph | Tag::Heading(..) => return ControlFlow::BREAK,
+                _ => {}
+            },
+            Event::HardBreak | Event::SoftBreak => buf.push(" ")?,
+            _ => {}
+        };
+        ControlFlow::CONTINUE
+    });
+
+    (buf.finish(), stopped_early)
+}
+
+/// Renders a shortened first paragraph of the given Markdown as a subset of Markdown,
+/// making it suitable for contexts like the search index.
+///
+/// Will shorten to 59 or 60 characters, including an ellipsis (…) if it was shortened.
+///
+/// See [`markdown_summary_with_limit`] for details about what is rendered and what is not.
+pub(crate) fn short_markdown_summary(markdown: &str, link_names: &[RenderedLink]) -> String {
+    let (mut s, was_shortened) = markdown_summary_with_limit(markdown, link_names, 59);
+
+    if was_shortened {
+        s.push('…');
+    }
+
+    s
+}
+
+/// Renders the first paragraph of the provided markdown as plain text.
+/// Useful for alt-text.
+///
+/// - Headings, links, and formatting are stripped.
+/// - Inline code is rendered as-is, surrounded by backticks.
+/// - HTML and code blocks are ignored.
+pub(crate) fn plain_text_summary(md: &str) -> String {
+    if md.is_empty() {
+        return String::new();
+    }
+
+    let mut s = String::with_capacity(md.len() * 3 / 2);
+
+    for event in Parser::new_ext(md, summary_opts()) {
+        match &event {
+            Event::Text(text) => s.push_str(text),
+            Event::Code(code) => {
+                s.push('`');
+                s.push_str(code);
+                s.push('`');
+            }
+            Event::HardBreak | Event::SoftBreak => s.push(' '),
+            Event::Start(Tag::CodeBlock(..)) => break,
+            Event::End(Tag::Paragraph) => break,
+            Event::End(Tag::Heading(..)) => break,
+            _ => (),
+        }
+    }
+
+    s
+}
+
+#[derive(Debug)]
+pub(crate) struct MarkdownLink {
+    pub kind: LinkType,
+    pub link: String,
+    pub range: Range<usize>,
+}
+
+pub(crate) fn markdown_links<R>(
+    md: &str,
+    filter_map: impl Fn(MarkdownLink) -> Option<R>,
+) -> Vec<R> {
+    if md.is_empty() {
+        return vec![];
+    }
+
+    let links = RefCell::new(vec![]);
+
+    // FIXME: remove this function once pulldown_cmark can provide spans for link definitions.
+    let locate = |s: &str, fallback: Range<usize>| unsafe {
+        let s_start = s.as_ptr();
+        let s_end = s_start.add(s.len());
+        let md_start = md.as_ptr();
+        let md_end = md_start.add(md.len());
+        if md_start <= s_start && s_end <= md_end {
+            let start = s_start.offset_from(md_start) as usize;
+            let end = s_end.offset_from(md_start) as usize;
+            start..end
+        } else {
+            fallback
+        }
+    };
+
+    let span_for_link = |link: &CowStr<'_>, span: Range<usize>| {
+        // For diagnostics, we want to underline the link's definition but `span` will point at
+        // where the link is used. This is a problem for reference-style links, where the definition
+        // is separate from the usage.
+        match link {
+            // `Borrowed` variant means the string (the link's destination) may come directly from
+            // the markdown text and we can locate the original link destination.
+            // NOTE: LinkReplacer also provides `Borrowed` but possibly from other sources,
+            // so `locate()` can fall back to use `span`.
+            CowStr::Borrowed(s) => locate(s, span),
+
+            // For anything else, we can only use the provided range.
+            CowStr::Boxed(_) | CowStr::Inlined(_) => span,
+        }
+    };
+
+    let mut push = |link: BrokenLink<'_>| {
+        let span = span_for_link(&link.reference, link.span);
+        filter_map(MarkdownLink {
+            kind: LinkType::ShortcutUnknown,
+            link: link.reference.to_string(),
+            range: span,
+        })
+        .map(|link| links.borrow_mut().push(link));
+        None
+    };
+    let p = Parser::new_with_broken_link_callback(md, main_body_opts(), Some(&mut push))
+        .into_offset_iter();
+
+    // There's no need to thread an IdMap through to here because
+    // the IDs generated aren't going to be emitted anywhere.
+    let mut ids = IdMap::new();
+    let iter = Footnotes::new(HeadingLinks::new(p, None, &mut ids, HeadingOffset::H1));
+
+    for ev in iter {
+        if let Event::Start(Tag::Link(
+            // `<>` links cannot be intra-doc links so we skip them.
+            kind @ (LinkType::Inline
+            | LinkType::Reference
+            | LinkType::ReferenceUnknown
+            | LinkType::Collapsed
+            | LinkType::CollapsedUnknown
+            | LinkType::Shortcut
+            | LinkType::ShortcutUnknown),
+            dest,
+            _,
+        )) = ev.0
+        {
+            debug!("found link: {dest}");
+            let span = span_for_link(&dest, ev.1);
+            filter_map(MarkdownLink { kind, link: dest.into_string(), range: span })
+                .map(|link| links.borrow_mut().push(link));
+        }
+    }
+
+    links.into_inner()
+}
+
+#[derive(Debug)]
+pub(crate) struct RustCodeBlock {
+    /// The range in the markdown that the code block occupies. Note that this includes the fences
+    /// for fenced code blocks.
+    pub(crate) range: Range<usize>,
+    /// The range in the markdown that the code within the code block occupies.
+    pub(crate) code: Range<usize>,
+    pub(crate) is_fenced: bool,
+    pub(crate) lang_string: LangString,
+}
+
+/// Returns a range of bytes for each code block in the markdown that is tagged as `rust` or
+/// untagged (and assumed to be rust).
+pub(crate) fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeBlock> {
+    let mut code_blocks = vec![];
+
+    if md.is_empty() {
+        return code_blocks;
+    }
+
+    let mut p = Parser::new_ext(md, main_body_opts()).into_offset_iter();
+
+    while let Some((event, offset)) = p.next() {
+        if let Event::Start(Tag::CodeBlock(syntax)) = event {
+            let (lang_string, code_start, code_end, range, is_fenced) = match syntax {
+                CodeBlockKind::Fenced(syntax) => {
+                    let syntax = syntax.as_ref();
+                    let lang_string = if syntax.is_empty() {
+                        Default::default()
+                    } else {
+                        LangString::parse(&*syntax, ErrorCodes::Yes, false, Some(extra_info))
+                    };
+                    if !lang_string.rust {
+                        continue;
+                    }
+                    let (code_start, mut code_end) = match p.next() {
+                        Some((Event::Text(_), offset)) => (offset.start, offset.end),
+                        Some((_, sub_offset)) => {
+                            let code = Range { start: sub_offset.start, end: sub_offset.start };
+                            code_blocks.push(RustCodeBlock {
+                                is_fenced: true,
+                                range: offset,
+                                code,
+                                lang_string,
+                            });
+                            continue;
+                        }
+                        None => {
+                            let code = Range { start: offset.end, end: offset.end };
+                            code_blocks.push(RustCodeBlock {
+                                is_fenced: true,
+                                range: offset,
+                                code,
+                                lang_string,
+                            });
+                            continue;
+                        }
+                    };
+                    while let Some((Event::Text(_), offset)) = p.next() {
+                        code_end = offset.end;
+                    }
+                    (lang_string, code_start, code_end, offset, true)
+                }
+                CodeBlockKind::Indented => {
+                    // The ending of the offset goes too far sometime so we reduce it by one in
+                    // these cases.
+                    if offset.end > offset.start && md.get(offset.end..=offset.end) == Some("\n") {
+                        (
+                            LangString::default(),
+                            offset.start,
+                            offset.end,
+                            Range { start: offset.start, end: offset.end - 1 },
+                            false,
+                        )
+                    } else {
+                        (LangString::default(), offset.start, offset.end, offset, false)
+                    }
+                }
+            };
+
+            code_blocks.push(RustCodeBlock {
+                is_fenced,
+                range,
+                code: Range { start: code_start, end: code_end },
+                lang_string,
+            });
+        }
+    }
+
+    code_blocks
+}
+
+#[derive(Clone, Default, Debug)]
+pub struct IdMap {
+    map: FxHashMap<Cow<'static, str>, usize>,
+}
+
+// The map is pre-initialized and cloned each time to avoid reinitializing it repeatedly.
+static DEFAULT_ID_MAP: Lazy<FxHashMap<Cow<'static, str>, usize>> = Lazy::new(|| init_id_map());
+
+fn init_id_map() -> FxHashMap<Cow<'static, str>, usize> {
+    let mut map = FxHashMap::default();
+    // This is the list of IDs used in Javascript.
+    map.insert("settings".into(), 1);
+    map.insert("not-displayed".into(), 1);
+    map.insert("alternative-display".into(), 1);
+    map.insert("search".into(), 1);
+    // This is the list of IDs used in HTML generated in Rust (including the ones
+    // used in tera template files).
+    map.insert("mainThemeStyle".into(), 1);
+    map.insert("themeStyle".into(), 1);
+    map.insert("settings-menu".into(), 1);
+    map.insert("help-button".into(), 1);
+    map.insert("main-content".into(), 1);
+    map.insert("crate-search".into(), 1);
+    map.insert("toggle-all-docs".into(), 1);
+    map.insert("all-types".into(), 1);
+    map.insert("default-settings".into(), 1);
+    map.insert("rustdoc-vars".into(), 1);
+    map.insert("sidebar-vars".into(), 1);
+    map.insert("copy-path".into(), 1);
+    map.insert("TOC".into(), 1);
+    // This is the list of IDs used by rustdoc sections (but still generated by
+    // rustdoc).
+    map.insert("fields".into(), 1);
+    map.insert("variants".into(), 1);
+    map.insert("implementors-list".into(), 1);
+    map.insert("synthetic-implementors-list".into(), 1);
+    map.insert("foreign-impls".into(), 1);
+    map.insert("implementations".into(), 1);
+    map.insert("trait-implementations".into(), 1);
+    map.insert("synthetic-implementations".into(), 1);
+    map.insert("blanket-implementations".into(), 1);
+    map.insert("required-associated-types".into(), 1);
+    map.insert("provided-associated-types".into(), 1);
+    map.insert("provided-associated-consts".into(), 1);
+    map.insert("required-associated-consts".into(), 1);
+    map.insert("required-methods".into(), 1);
+    map.insert("provided-methods".into(), 1);
+    map.insert("implementors".into(), 1);
+    map.insert("synthetic-implementors".into(), 1);
+    map.insert("implementations-list".into(), 1);
+    map.insert("trait-implementations-list".into(), 1);
+    map.insert("synthetic-implementations-list".into(), 1);
+    map.insert("blanket-implementations-list".into(), 1);
+    map.insert("deref-methods".into(), 1);
+    map.insert("layout".into(), 1);
+    map
+}
+
+impl IdMap {
+    pub fn new() -> Self {
+        IdMap { map: DEFAULT_ID_MAP.clone() }
+    }
+
+    pub(crate) fn derive<S: AsRef<str> + ToString>(&mut self, candidate: S) -> String {
+        let id = match self.map.get_mut(candidate.as_ref()) {
+            None => candidate.to_string(),
+            Some(a) => {
+                let id = format!("{}-{}", candidate.as_ref(), *a);
+                *a += 1;
+                id
+            }
+        };
+
+        self.map.insert(id.clone().into(), 1);
+        id
+    }
+}
diff --git a/src/librustdoc/html/markdown/tests.rs b/src/librustdoc/html/markdown/tests.rs
new file mode 100644
index 000000000..5c0bf0ed9
--- /dev/null
+++ b/src/librustdoc/html/markdown/tests.rs
@@ -0,0 +1,312 @@
+use super::{find_testable_code, plain_text_summary, short_markdown_summary};
+use super::{ErrorCodes, HeadingOffset, IdMap, Ignore, LangString, Markdown, MarkdownHtml};
+use rustc_span::edition::{Edition, DEFAULT_EDITION};
+
+#[test]
+fn test_unique_id() {
+    let input = [
+        "foo",
+        "examples",
+        "examples",
+        "method.into_iter",
+        "examples",
+        "method.into_iter",
+        "foo",
+        "main-content",
+        "search",
+        "methods",
+        "examples",
+        "method.into_iter",
+        "assoc_type.Item",
+        "assoc_type.Item",
+    ];
+    let expected = [
+        "foo",
+        "examples",
+        "examples-1",
+        "method.into_iter",
+        "examples-2",
+        "method.into_iter-1",
+        "foo-1",
+        "main-content-1",
+        "search-1",
+        "methods",
+        "examples-3",
+        "method.into_iter-2",
+        "assoc_type.Item",
+        "assoc_type.Item-1",
+    ];
+
+    let mut map = IdMap::new();
+    let actual: Vec<String> = input.iter().map(|s| map.derive(s.to_string())).collect();
+    assert_eq!(&actual[..], expected);
+}
+
+#[test]
+fn test_lang_string_parse() {
+    fn t(lg: LangString) {
+        let s = &lg.original;
+        assert_eq!(LangString::parse(s, ErrorCodes::Yes, true, None), lg)
+    }
+
+    t(Default::default());
+    t(LangString { original: "rust".into(), ..Default::default() });
+    t(LangString { original: ".rust".into(), ..Default::default() });
+    t(LangString { original: "{rust}".into(), ..Default::default() });
+    t(LangString { original: "{.rust}".into(), ..Default::default() });
+    t(LangString { original: "sh".into(), rust: false, ..Default::default() });
+    t(LangString { original: "ignore".into(), ignore: Ignore::All, ..Default::default() });
+    t(LangString {
+        original: "ignore-foo".into(),
+        ignore: Ignore::Some(vec!["foo".to_string()]),
+        ..Default::default()
+    });
+    t(LangString { original: "should_panic".into(), should_panic: true, ..Default::default() });
+    t(LangString { original: "no_run".into(), no_run: true, ..Default::default() });
+    t(LangString { original: "test_harness".into(), test_harness: true, ..Default::default() });
+    t(LangString {
+        original: "compile_fail".into(),
+        no_run: true,
+        compile_fail: true,
+        ..Default::default()
+    });
+    t(LangString { original: "no_run,example".into(), no_run: true, ..Default::default() });
+    t(LangString {
+        original: "sh,should_panic".into(),
+        should_panic: true,
+        rust: false,
+        ..Default::default()
+    });
+    t(LangString { original: "example,rust".into(), ..Default::default() });
+    t(LangString {
+        original: "test_harness,.rust".into(),
+        test_harness: true,
+        ..Default::default()
+    });
+    t(LangString {
+        original: "text, no_run".into(),
+        no_run: true,
+        rust: false,
+        ..Default::default()
+    });
+    t(LangString {
+        original: "text,no_run".into(),
+        no_run: true,
+        rust: false,
+        ..Default::default()
+    });
+    t(LangString {
+        original: "text,no_run, ".into(),
+        no_run: true,
+        rust: false,
+        ..Default::default()
+    });
+    t(LangString {
+        original: "text,no_run,".into(),
+        no_run: true,
+        rust: false,
+        ..Default::default()
+    });
+    t(LangString {
+        original: "edition2015".into(),
+        edition: Some(Edition::Edition2015),
+        ..Default::default()
+    });
+    t(LangString {
+        original: "edition2018".into(),
+        edition: Some(Edition::Edition2018),
+        ..Default::default()
+    });
+}
+
+#[test]
+fn test_lang_string_tokenizer() {
+    fn case(lang_string: &str, want: &[&str]) {
+        let have = LangString::tokens(lang_string).collect::<Vec<&str>>();
+        assert_eq!(have, want, "Unexpected lang string split for `{}`", lang_string);
+    }
+
+    case("", &[]);
+    case("foo", &["foo"]);
+    case("foo,bar", &["foo", "bar"]);
+    case(".foo,.bar", &["foo", "bar"]);
+    case("{.foo,.bar}", &["foo", "bar"]);
+    case("  {.foo,.bar}  ", &["foo", "bar"]);
+    case("foo bar", &["foo", "bar"]);
+    case("foo\tbar", &["foo", "bar"]);
+    case("foo\t, bar", &["foo", "bar"]);
+    case(" foo , bar ", &["foo", "bar"]);
+    case(",,foo,,bar,,", &["foo", "bar"]);
+    case("foo=bar", &["foo=bar"]);
+    case("a-b-c", &["a-b-c"]);
+    case("a_b_c", &["a_b_c"]);
+}
+
+#[test]
+fn test_header() {
+    fn t(input: &str, expect: &str) {
+        let mut map = IdMap::new();
+        let output = Markdown {
+            content: input,
+            links: &[],
+            ids: &mut map,
+            error_codes: ErrorCodes::Yes,
+            edition: DEFAULT_EDITION,
+            playground: &None,
+            heading_offset: HeadingOffset::H2,
+        }
+        .into_string();
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t("# Foo bar", "<h2 id=\"foo-bar\"><a href=\"#foo-bar\">Foo bar</a></h2>");
+    t(
+        "## Foo-bar_baz qux",
+        "<h3 id=\"foo-bar_baz-qux\">\
+         <a href=\"#foo-bar_baz-qux\">Foo-bar_baz qux</a></h3>",
+    );
+    t(
+        "### **Foo** *bar* baz!?!& -_qux_-%",
+        "<h4 id=\"foo-bar-baz--qux-\">\
+            <a href=\"#foo-bar-baz--qux-\"><strong>Foo</strong> \
+            <em>bar</em> baz!?!&amp; -<em>qux</em>-%</a>\
+         </h4>",
+    );
+    t(
+        "#### **Foo?** & \\*bar?!*  _`baz`_ ❤ #qux",
+        "<h5 id=\"foo--bar--baz--qux\">\
+             <a href=\"#foo--bar--baz--qux\"><strong>Foo?</strong> &amp; *bar?!*  \
+             <em><code>baz</code></em> ❤ #qux</a>\
+         </h5>",
+    );
+}
+
+#[test]
+fn test_header_ids_multiple_blocks() {
+    let mut map = IdMap::new();
+    fn t(map: &mut IdMap, input: &str, expect: &str) {
+        let output = Markdown {
+            content: input,
+            links: &[],
+            ids: map,
+            error_codes: ErrorCodes::Yes,
+            edition: DEFAULT_EDITION,
+            playground: &None,
+            heading_offset: HeadingOffset::H2,
+        }
+        .into_string();
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t(&mut map, "# Example", "<h2 id=\"example\"><a href=\"#example\">Example</a></h2>");
+    t(&mut map, "# Panics", "<h2 id=\"panics\"><a href=\"#panics\">Panics</a></h2>");
+    t(&mut map, "# Example", "<h2 id=\"example-1\"><a href=\"#example-1\">Example</a></h2>");
+    t(&mut map, "# Search", "<h2 id=\"search-1\"><a href=\"#search-1\">Search</a></h2>");
+    t(&mut map, "# Example", "<h2 id=\"example-2\"><a href=\"#example-2\">Example</a></h2>");
+    t(&mut map, "# Panics", "<h2 id=\"panics-1\"><a href=\"#panics-1\">Panics</a></h2>");
+}
+
+#[test]
+fn test_short_markdown_summary() {
+    fn t(input: &str, expect: &str) {
+        let output = short_markdown_summary(input, &[][..]);
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t("", "");
+    t("hello [Rust](https://www.rust-lang.org) :)", "hello Rust :)");
+    t("*italic*", "<em>italic</em>");
+    t("**bold**", "<strong>bold</strong>");
+    t("Multi-line\nsummary", "Multi-line summary");
+    t("Hard-break  \nsummary", "Hard-break summary");
+    t("hello [Rust] :)\n\n[Rust]: https://www.rust-lang.org", "hello Rust :)");
+    t("hello [Rust](https://www.rust-lang.org \"Rust\") :)", "hello Rust :)");
+    t("dud [link]", "dud [link]");
+    t("code `let x = i32;` ...", "code <code>let x = i32;</code> …");
+    t("type `Type<'static>` ...", "type <code>Type&lt;&#39;static&gt;</code> …");
+    // Test to ensure escaping and length-limiting work well together.
+    // The output should be limited based on the input length,
+    // rather than the output, because escaped versions of characters
+    // are usually longer than how the character is actually displayed.
+    t(
+        "& & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & &",
+        "&amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; \
+         &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; &amp; \
+         &amp; &amp; &amp; &amp; &amp; …",
+    );
+    t("# top header", "top header");
+    t("# top header\n\nfollowed by a paragraph", "top header");
+    t("## header", "header");
+    t("first paragraph\n\nsecond paragraph", "first paragraph");
+    t("```\nfn main() {}\n```", "");
+    t("<div>hello</div>", "");
+    t(
+        "a *very*, **very** long first paragraph. it has lots of `inline code: Vec<T>`. and it has a [link](https://www.rust-lang.org).\nthat was a soft line break!  \nthat was a hard one\n\nsecond paragraph.",
+        "a <em>very</em>, <strong>very</strong> long first paragraph. it has lots of …",
+    );
+}
+
+#[test]
+fn test_plain_text_summary() {
+    fn t(input: &str, expect: &str) {
+        let output = plain_text_summary(input);
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t("", "");
+    t("hello [Rust](https://www.rust-lang.org) :)", "hello Rust :)");
+    t("**bold**", "bold");
+    t("Multi-line\nsummary", "Multi-line summary");
+    t("Hard-break  \nsummary", "Hard-break summary");
+    t("hello [Rust] :)\n\n[Rust]: https://www.rust-lang.org", "hello Rust :)");
+    t("hello [Rust](https://www.rust-lang.org \"Rust\") :)", "hello Rust :)");
+    t("dud [link]", "dud [link]");
+    t("code `let x = i32;` ...", "code `let x = i32;` …");
+    t("type `Type<'static>` ...", "type `Type<'static>` …");
+    t("# top header", "top header");
+    t("# top header\n\nfollowed by some text", "top header");
+    t("## header", "header");
+    t("first paragraph\n\nsecond paragraph", "first paragraph");
+    t("```\nfn main() {}\n```", "");
+    t("<div>hello</div>", "");
+    t(
+        "a *very*, **very** long first paragraph. it has lots of `inline code: Vec<T>`. and it has a [link](https://www.rust-lang.org).\nthat was a soft line break!  \nthat was a hard one\n\nsecond paragraph.",
+        "a very, very long first paragraph. it has lots of `inline code: Vec<T>`. and it has a link. that was a soft line break! that was a hard one",
+    );
+}
+
+#[test]
+fn test_markdown_html_escape() {
+    fn t(input: &str, expect: &str) {
+        let mut idmap = IdMap::new();
+        let output =
+            MarkdownHtml(input, &mut idmap, ErrorCodes::Yes, DEFAULT_EDITION, &None).into_string();
+        assert_eq!(output, expect, "original: {}", input);
+    }
+
+    t("`Struct<'a, T>`", "<p><code>Struct&lt;'a, T&gt;</code></p>\n");
+    t("Struct<'a, T>", "<p>Struct&lt;’a, T&gt;</p>\n");
+    t("Struct<br>", "<p>Struct&lt;br&gt;</p>\n");
+}
+
+#[test]
+fn test_find_testable_code_line() {
+    fn t(input: &str, expect: &[usize]) {
+        impl crate::doctest::Tester for Vec<usize> {
+            fn add_test(&mut self, _test: String, _config: LangString, line: usize) {
+                self.push(line);
+            }
+        }
+        let mut lines = Vec::<usize>::new();
+        find_testable_code(input, &mut lines, ErrorCodes::No, false, None);
+        assert_eq!(lines, expect);
+    }
+
+    t("", &[]);
+    t("```rust\n```", &[1]);
+    t(" ```rust\n```", &[1]);
+    t("\n```rust\n```", &[2]);
+    t("\n ```rust\n```", &[2]);
+    t("```rust\n```\n```rust\n```", &[1, 3]);
+    t("```rust\n```\n ```rust\n```", &[1, 3]);
+}
diff --git a/src/librustdoc/html/mod.rs b/src/librustdoc/html/mod.rs
new file mode 100644
index 000000000..481ed16c0
--- /dev/null
+++ b/src/librustdoc/html/mod.rs
@@ -0,0 +1,15 @@
+pub(crate) mod escape;
+pub(crate) mod format;
+pub(crate) mod highlight;
+pub(crate) mod layout;
+mod length_limit;
+// used by the error-index generator, so it needs to be public
+pub mod markdown;
+pub(crate) mod render;
+pub(crate) mod sources;
+pub(crate) mod static_files;
+pub(crate) mod toc;
+mod url_parts_builder;
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
new file mode 100644
index 000000000..2ed7a6f1b
--- /dev/null
+++ b/src/librustdoc/html/render/context.rs
@@ -0,0 +1,762 @@
+use std::cell::RefCell;
+use std::collections::BTreeMap;
+use std::io;
+use std::path::{Path, PathBuf};
+use std::rc::Rc;
+use std::sync::mpsc::{channel, Receiver};
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_middle::ty::TyCtxt;
+use rustc_session::Session;
+use rustc_span::edition::Edition;
+use rustc_span::source_map::FileName;
+use rustc_span::{sym, Symbol};
+
+use super::print_item::{full_path, item_path, print_item};
+use super::search_index::build_index;
+use super::write_shared::write_shared;
+use super::{
+    collect_spans_and_sources, print_sidebar, scrape_examples_help, AllTypes, LinkFromSrc, NameDoc,
+    StylePath, BASIC_KEYWORDS,
+};
+
+use crate::clean::{self, types::ExternalLocation, ExternalCrate};
+use crate::config::{ModuleSorting, RenderOptions};
+use crate::docfs::{DocFS, PathError};
+use crate::error::Error;
+use crate::formats::cache::Cache;
+use crate::formats::item_type::ItemType;
+use crate::formats::FormatRenderer;
+use crate::html::escape::Escape;
+use crate::html::format::{join_with_double_colon, Buffer};
+use crate::html::markdown::{self, plain_text_summary, ErrorCodes, IdMap};
+use crate::html::{layout, sources};
+use crate::scrape_examples::AllCallLocations;
+use crate::try_err;
+
+/// Major driving force in all rustdoc rendering. This contains information
+/// about where in the tree-like hierarchy rendering is occurring and controls
+/// how the current page is being rendered.
+///
+/// It is intended that this context is a lightweight object which can be fairly
+/// easily cloned because it is cloned per work-job (about once per item in the
+/// rustdoc tree).
+pub(crate) struct Context<'tcx> {
+    /// Current hierarchy of components leading down to what's currently being
+    /// rendered
+    pub(crate) current: Vec<Symbol>,
+    /// The current destination folder of where HTML artifacts should be placed.
+    /// This changes as the context descends into the module hierarchy.
+    pub(crate) dst: PathBuf,
+    /// A flag, which when `true`, will render pages which redirect to the
+    /// real location of an item. This is used to allow external links to
+    /// publicly reused items to redirect to the right location.
+    pub(super) render_redirect_pages: bool,
+    /// Tracks section IDs for `Deref` targets so they match in both the main
+    /// body and the sidebar.
+    pub(super) deref_id_map: FxHashMap<DefId, String>,
+    /// The map used to ensure all generated 'id=' attributes are unique.
+    pub(super) id_map: IdMap,
+    /// Shared mutable state.
+    ///
+    /// Issue for improving the situation: [#82381][]
+    ///
+    /// [#82381]: https://github.com/rust-lang/rust/issues/82381
+    pub(crate) shared: Rc<SharedContext<'tcx>>,
+    /// This flag indicates whether source links should be generated or not. If
+    /// the source files are present in the html rendering, then this will be
+    /// `true`.
+    pub(crate) include_sources: bool,
+}
+
+// `Context` is cloned a lot, so we don't want the size to grow unexpectedly.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(Context<'_>, 128);
+
+/// Shared mutable state used in [`Context`] and elsewhere.
+pub(crate) struct SharedContext<'tcx> {
+    pub(crate) tcx: TyCtxt<'tcx>,
+    /// The path to the crate root source minus the file name.
+    /// Used for simplifying paths to the highlighted source code files.
+    pub(crate) src_root: PathBuf,
+    /// This describes the layout of each page, and is not modified after
+    /// creation of the context (contains info like the favicon and added html).
+    pub(crate) layout: layout::Layout,
+    /// The local file sources we've emitted and their respective url-paths.
+    pub(crate) local_sources: FxHashMap<PathBuf, String>,
+    /// Show the memory layout of types in the docs.
+    pub(super) show_type_layout: bool,
+    /// The base-URL of the issue tracker for when an item has been tagged with
+    /// an issue number.
+    pub(super) issue_tracker_base_url: Option<String>,
+    /// The directories that have already been created in this doc run. Used to reduce the number
+    /// of spurious `create_dir_all` calls.
+    created_dirs: RefCell<FxHashSet<PathBuf>>,
+    /// This flag indicates whether listings of modules (in the side bar and documentation itself)
+    /// should be ordered alphabetically or in order of appearance (in the source code).
+    pub(super) module_sorting: ModuleSorting,
+    /// Additional CSS files to be added to the generated docs.
+    pub(crate) style_files: Vec<StylePath>,
+    /// Suffix to be added on resource files (if suffix is "-v2" then "light.css" becomes
+    /// "light-v2.css").
+    pub(crate) resource_suffix: String,
+    /// Optional path string to be used to load static files on output pages. If not set, uses
+    /// combinations of `../` to reach the documentation root.
+    pub(crate) static_root_path: Option<String>,
+    /// The fs handle we are working with.
+    pub(crate) fs: DocFS,
+    pub(super) codes: ErrorCodes,
+    pub(super) playground: Option<markdown::Playground>,
+    all: RefCell<AllTypes>,
+    /// Storage for the errors produced while generating documentation so they
+    /// can be printed together at the end.
+    errors: Receiver<String>,
+    /// `None` by default, depends on the `generate-redirect-map` option flag. If this field is set
+    /// to `Some(...)`, it'll store redirections and then generate a JSON file at the top level of
+    /// the crate.
+    redirections: Option<RefCell<FxHashMap<String, String>>>,
+
+    /// Correspondance map used to link types used in the source code pages to allow to click on
+    /// links to jump to the type's definition.
+    pub(crate) span_correspondance_map: FxHashMap<rustc_span::Span, LinkFromSrc>,
+    /// The [`Cache`] used during rendering.
+    pub(crate) cache: Cache,
+
+    pub(crate) call_locations: AllCallLocations,
+}
+
+impl SharedContext<'_> {
+    pub(crate) fn ensure_dir(&self, dst: &Path) -> Result<(), Error> {
+        let mut dirs = self.created_dirs.borrow_mut();
+        if !dirs.contains(dst) {
+            try_err!(self.fs.create_dir_all(dst), dst);
+            dirs.insert(dst.to_path_buf());
+        }
+
+        Ok(())
+    }
+
+    pub(crate) fn edition(&self) -> Edition {
+        self.tcx.sess.edition()
+    }
+}
+
+impl<'tcx> Context<'tcx> {
+    pub(crate) fn tcx(&self) -> TyCtxt<'tcx> {
+        self.shared.tcx
+    }
+
+    pub(crate) fn cache(&self) -> &Cache {
+        &self.shared.cache
+    }
+
+    pub(super) fn sess(&self) -> &'tcx Session {
+        self.shared.tcx.sess
+    }
+
+    pub(super) fn derive_id(&mut self, id: String) -> String {
+        self.id_map.derive(id)
+    }
+
+    /// String representation of how to get back to the root path of the 'doc/'
+    /// folder in terms of a relative URL.
+    pub(super) fn root_path(&self) -> String {
+        "../".repeat(self.current.len())
+    }
+
+    fn render_item(&mut self, it: &clean::Item, is_module: bool) -> String {
+        let mut title = String::new();
+        if !is_module {
+            title.push_str(it.name.unwrap().as_str());
+        }
+        if !it.is_primitive() && !it.is_keyword() {
+            if !is_module {
+                title.push_str(" in ");
+            }
+            // No need to include the namespace for primitive types and keywords
+            title.push_str(&join_with_double_colon(&self.current));
+        };
+        title.push_str(" - Rust");
+        let tyname = it.type_();
+        let desc = it.doc_value().as_ref().map(|doc| plain_text_summary(doc));
+        let desc = if let Some(desc) = desc {
+            desc
+        } else if it.is_crate() {
+            format!("API documentation for the Rust `{}` crate.", self.shared.layout.krate)
+        } else {
+            format!(
+                "API documentation for the Rust `{}` {} in crate `{}`.",
+                it.name.as_ref().unwrap(),
+                tyname,
+                self.shared.layout.krate
+            )
+        };
+        let keywords = make_item_keywords(it);
+        let name;
+        let tyname_s = if it.is_crate() {
+            name = format!("{} crate", tyname);
+            name.as_str()
+        } else {
+            tyname.as_str()
+        };
+
+        if !self.render_redirect_pages {
+            let clone_shared = Rc::clone(&self.shared);
+            let page = layout::Page {
+                css_class: tyname_s,
+                root_path: &self.root_path(),
+                static_root_path: clone_shared.static_root_path.as_deref(),
+                title: &title,
+                description: &desc,
+                keywords: &keywords,
+                resource_suffix: &clone_shared.resource_suffix,
+            };
+            let mut page_buffer = Buffer::html();
+            print_item(self, it, &mut page_buffer, &page);
+            layout::render(
+                &clone_shared.layout,
+                &page,
+                |buf: &mut _| print_sidebar(self, it, buf),
+                move |buf: &mut Buffer| buf.push_buffer(page_buffer),
+                &clone_shared.style_files,
+            )
+        } else {
+            if let Some(&(ref names, ty)) = self.cache().paths.get(&it.item_id.expect_def_id()) {
+                if self.current.len() + 1 != names.len()
+                    || self.current.iter().zip(names.iter()).any(|(a, b)| a != b)
+                {
+                    // We checked that the redirection isn't pointing to the current file,
+                    // preventing an infinite redirection loop in the generated
+                    // documentation.
+
+                    let mut path = String::new();
+                    for name in &names[..names.len() - 1] {
+                        path.push_str(name.as_str());
+                        path.push('/');
+                    }
+                    path.push_str(&item_path(ty, names.last().unwrap().as_str()));
+                    match self.shared.redirections {
+                        Some(ref redirections) => {
+                            let mut current_path = String::new();
+                            for name in &self.current {
+                                current_path.push_str(name.as_str());
+                                current_path.push('/');
+                            }
+                            current_path.push_str(&item_path(ty, names.last().unwrap().as_str()));
+                            redirections.borrow_mut().insert(current_path, path);
+                        }
+                        None => return layout::redirect(&format!("{}{}", self.root_path(), path)),
+                    }
+                }
+            }
+            String::new()
+        }
+    }
+
+    /// Construct a map of items shown in the sidebar to a plain-text summary of their docs.
+    fn build_sidebar_items(&self, m: &clean::Module) -> BTreeMap<String, Vec<NameDoc>> {
+        // BTreeMap instead of HashMap to get a sorted output
+        let mut map: BTreeMap<_, Vec<_>> = BTreeMap::new();
+        let mut inserted: FxHashMap<ItemType, FxHashSet<Symbol>> = FxHashMap::default();
+
+        for item in &m.items {
+            if item.is_stripped() {
+                continue;
+            }
+
+            let short = item.type_();
+            let myname = match item.name {
+                None => continue,
+                Some(s) => s,
+            };
+            if inserted.entry(short).or_default().insert(myname) {
+                let short = short.to_string();
+                let myname = myname.to_string();
+                map.entry(short).or_default().push((
+                    myname,
+                    Some(item.doc_value().map_or_else(String::new, |s| plain_text_summary(&s))),
+                ));
+            }
+        }
+
+        match self.shared.module_sorting {
+            ModuleSorting::Alphabetical => {
+                for items in map.values_mut() {
+                    items.sort();
+                }
+            }
+            ModuleSorting::DeclarationOrder => {}
+        }
+        map
+    }
+
+    /// Generates a url appropriate for an `href` attribute back to the source of
+    /// this item.
+    ///
+    /// The url generated, when clicked, will redirect the browser back to the
+    /// original source code.
+    ///
+    /// If `None` is returned, then a source link couldn't be generated. This
+    /// may happen, for example, with externally inlined items where the source
+    /// of their crate documentation isn't known.
+    pub(super) fn src_href(&self, item: &clean::Item) -> Option<String> {
+        self.href_from_span(item.span(self.tcx()), true)
+    }
+
+    pub(crate) fn href_from_span(&self, span: clean::Span, with_lines: bool) -> Option<String> {
+        if span.is_dummy() {
+            return None;
+        }
+        let mut root = self.root_path();
+        let mut path = String::new();
+        let cnum = span.cnum(self.sess());
+
+        // We can safely ignore synthetic `SourceFile`s.
+        let file = match span.filename(self.sess()) {
+            FileName::Real(ref path) => path.local_path_if_available().to_path_buf(),
+            _ => return None,
+        };
+        let file = &file;
+
+        let krate_sym;
+        let (krate, path) = if cnum == LOCAL_CRATE {
+            if let Some(path) = self.shared.local_sources.get(file) {
+                (self.shared.layout.krate.as_str(), path)
+            } else {
+                return None;
+            }
+        } else {
+            let (krate, src_root) = match *self.cache().extern_locations.get(&cnum)? {
+                ExternalLocation::Local => {
+                    let e = ExternalCrate { crate_num: cnum };
+                    (e.name(self.tcx()), e.src_root(self.tcx()))
+                }
+                ExternalLocation::Remote(ref s) => {
+                    root = s.to_string();
+                    let e = ExternalCrate { crate_num: cnum };
+                    (e.name(self.tcx()), e.src_root(self.tcx()))
+                }
+                ExternalLocation::Unknown => return None,
+            };
+
+            sources::clean_path(&src_root, file, false, |component| {
+                path.push_str(&component.to_string_lossy());
+                path.push('/');
+            });
+            let mut fname = file.file_name().expect("source has no filename").to_os_string();
+            fname.push(".html");
+            path.push_str(&fname.to_string_lossy());
+            krate_sym = krate;
+            (krate_sym.as_str(), &path)
+        };
+
+        let anchor = if with_lines {
+            let loline = span.lo(self.sess()).line;
+            let hiline = span.hi(self.sess()).line;
+            format!(
+                "#{}",
+                if loline == hiline {
+                    loline.to_string()
+                } else {
+                    format!("{}-{}", loline, hiline)
+                }
+            )
+        } else {
+            "".to_string()
+        };
+        Some(format!(
+            "{root}src/{krate}/{path}{anchor}",
+            root = Escape(&root),
+            krate = krate,
+            path = path,
+            anchor = anchor
+        ))
+    }
+}
+
+/// Generates the documentation for `crate` into the directory `dst`
+impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
+    fn descr() -> &'static str {
+        "html"
+    }
+
+    const RUN_ON_MODULE: bool = true;
+
+    fn init(
+        krate: clean::Crate,
+        options: RenderOptions,
+        cache: Cache,
+        tcx: TyCtxt<'tcx>,
+    ) -> Result<(Self, clean::Crate), Error> {
+        // need to save a copy of the options for rendering the index page
+        let md_opts = options.clone();
+        let emit_crate = options.should_emit_crate();
+        let RenderOptions {
+            output,
+            external_html,
+            id_map,
+            playground_url,
+            module_sorting,
+            themes: style_files,
+            default_settings,
+            extension_css,
+            resource_suffix,
+            static_root_path,
+            unstable_features,
+            generate_redirect_map,
+            show_type_layout,
+            generate_link_to_definition,
+            call_locations,
+            no_emit_shared,
+            ..
+        } = options;
+
+        let src_root = match krate.src(tcx) {
+            FileName::Real(ref p) => match p.local_path_if_available().parent() {
+                Some(p) => p.to_path_buf(),
+                None => PathBuf::new(),
+            },
+            _ => PathBuf::new(),
+        };
+        // If user passed in `--playground-url` arg, we fill in crate name here
+        let mut playground = None;
+        if let Some(url) = playground_url {
+            playground =
+                Some(markdown::Playground { crate_name: Some(krate.name(tcx).to_string()), url });
+        }
+        let mut layout = layout::Layout {
+            logo: String::new(),
+            favicon: String::new(),
+            external_html,
+            default_settings,
+            krate: krate.name(tcx).to_string(),
+            css_file_extension: extension_css,
+            scrape_examples_extension: !call_locations.is_empty(),
+        };
+        let mut issue_tracker_base_url = None;
+        let mut include_sources = true;
+
+        // Crawl the crate attributes looking for attributes which control how we're
+        // going to emit HTML
+        for attr in krate.module.attrs.lists(sym::doc) {
+            match (attr.name_or_empty(), attr.value_str()) {
+                (sym::html_favicon_url, Some(s)) => {
+                    layout.favicon = s.to_string();
+                }
+                (sym::html_logo_url, Some(s)) => {
+                    layout.logo = s.to_string();
+                }
+                (sym::html_playground_url, Some(s)) => {
+                    playground = Some(markdown::Playground {
+                        crate_name: Some(krate.name(tcx).to_string()),
+                        url: s.to_string(),
+                    });
+                }
+                (sym::issue_tracker_base_url, Some(s)) => {
+                    issue_tracker_base_url = Some(s.to_string());
+                }
+                (sym::html_no_source, None) if attr.is_word() => {
+                    include_sources = false;
+                }
+                _ => {}
+            }
+        }
+
+        let (local_sources, matches) = collect_spans_and_sources(
+            tcx,
+            &krate,
+            &src_root,
+            include_sources,
+            generate_link_to_definition,
+        );
+
+        let (sender, receiver) = channel();
+        let mut scx = SharedContext {
+            tcx,
+            src_root,
+            local_sources,
+            issue_tracker_base_url,
+            layout,
+            created_dirs: Default::default(),
+            module_sorting,
+            style_files,
+            resource_suffix,
+            static_root_path,
+            fs: DocFS::new(sender),
+            codes: ErrorCodes::from(unstable_features.is_nightly_build()),
+            playground,
+            all: RefCell::new(AllTypes::new()),
+            errors: receiver,
+            redirections: if generate_redirect_map { Some(Default::default()) } else { None },
+            show_type_layout,
+            span_correspondance_map: matches,
+            cache,
+            call_locations,
+        };
+
+        // Add the default themes to the `Vec` of stylepaths
+        //
+        // Note that these must be added before `sources::render` is called
+        // so that the resulting source pages are styled
+        //
+        // `light.css` is not disabled because it is the stylesheet that stays loaded
+        // by the browser as the theme stylesheet. The theme system (hackily) works by
+        // changing the href to this stylesheet. All other themes are disabled to
+        // prevent rule conflicts
+        scx.style_files.push(StylePath { path: PathBuf::from("light.css") });
+        scx.style_files.push(StylePath { path: PathBuf::from("dark.css") });
+        scx.style_files.push(StylePath { path: PathBuf::from("ayu.css") });
+
+        let dst = output;
+        scx.ensure_dir(&dst)?;
+
+        let mut cx = Context {
+            current: Vec::new(),
+            dst,
+            render_redirect_pages: false,
+            id_map,
+            deref_id_map: FxHashMap::default(),
+            shared: Rc::new(scx),
+            include_sources,
+        };
+
+        if emit_crate {
+            sources::render(&mut cx, &krate)?;
+        }
+
+        if !no_emit_shared {
+            // Build our search index
+            let index = build_index(&krate, &mut Rc::get_mut(&mut cx.shared).unwrap().cache, tcx);
+
+            // Write shared runs within a flock; disable thread dispatching of IO temporarily.
+            Rc::get_mut(&mut cx.shared).unwrap().fs.set_sync_only(true);
+            write_shared(&mut cx, &krate, index, &md_opts)?;
+            Rc::get_mut(&mut cx.shared).unwrap().fs.set_sync_only(false);
+        }
+
+        Ok((cx, krate))
+    }
+
+    fn make_child_renderer(&self) -> Self {
+        Self {
+            current: self.current.clone(),
+            dst: self.dst.clone(),
+            render_redirect_pages: self.render_redirect_pages,
+            deref_id_map: FxHashMap::default(),
+            id_map: IdMap::new(),
+            shared: Rc::clone(&self.shared),
+            include_sources: self.include_sources,
+        }
+    }
+
+    fn after_krate(&mut self) -> Result<(), Error> {
+        let crate_name = self.tcx().crate_name(LOCAL_CRATE);
+        let final_file = self.dst.join(crate_name.as_str()).join("all.html");
+        let settings_file = self.dst.join("settings.html");
+        let scrape_examples_help_file = self.dst.join("scrape-examples-help.html");
+
+        let mut root_path = self.dst.to_str().expect("invalid path").to_owned();
+        if !root_path.ends_with('/') {
+            root_path.push('/');
+        }
+        let shared = Rc::clone(&self.shared);
+        let mut page = layout::Page {
+            title: "List of all items in this crate",
+            css_class: "mod",
+            root_path: "../",
+            static_root_path: shared.static_root_path.as_deref(),
+            description: "List of all items in this crate",
+            keywords: BASIC_KEYWORDS,
+            resource_suffix: &shared.resource_suffix,
+        };
+        let sidebar = if shared.cache.crate_version.is_some() {
+            format!("<h2 class=\"location\">Crate {}</h2>", crate_name)
+        } else {
+            String::new()
+        };
+        let all = shared.all.replace(AllTypes::new());
+        let v = layout::render(
+            &shared.layout,
+            &page,
+            sidebar,
+            |buf: &mut Buffer| all.print(buf),
+            &shared.style_files,
+        );
+        shared.fs.write(final_file, v)?;
+
+        // Generating settings page.
+        page.title = "Rustdoc settings";
+        page.description = "Settings of Rustdoc";
+        page.root_path = "./";
+
+        let sidebar = "<h2 class=\"location\">Settings</h2><div class=\"sidebar-elems\"></div>";
+        let v = layout::render(
+            &shared.layout,
+            &page,
+            sidebar,
+            |buf: &mut Buffer| {
+                write!(
+                    buf,
+                    "<div class=\"main-heading\">\
+                     <h1 class=\"fqn\">\
+                         <span class=\"in-band\">Rustdoc settings</span>\
+                     </h1>\
+                     <span class=\"out-of-band\">\
+                         <a id=\"back\" href=\"javascript:void(0)\" onclick=\"history.back();\">\
+                            Back\
+                        </a>\
+                     </span>\
+                     </div>\
+                     <noscript>\
+                        <section>\
+                            You need to enable Javascript be able to update your settings.\
+                        </section>\
+                     </noscript>\
+                     <link rel=\"stylesheet\" type=\"text/css\" \
+                         href=\"{root_path}settings{suffix}.css\">\
+                     <script defer src=\"{root_path}settings{suffix}.js\"></script>",
+                    root_path = page.static_root_path.unwrap_or(""),
+                    suffix = page.resource_suffix,
+                )
+            },
+            &shared.style_files,
+        );
+        shared.fs.write(settings_file, v)?;
+
+        if shared.layout.scrape_examples_extension {
+            page.title = "About scraped examples";
+            page.description = "How the scraped examples feature works in Rustdoc";
+            let v = layout::render(
+                &shared.layout,
+                &page,
+                "",
+                scrape_examples_help(&*shared),
+                &shared.style_files,
+            );
+            shared.fs.write(scrape_examples_help_file, v)?;
+        }
+
+        if let Some(ref redirections) = shared.redirections {
+            if !redirections.borrow().is_empty() {
+                let redirect_map_path =
+                    self.dst.join(crate_name.as_str()).join("redirect-map.json");
+                let paths = serde_json::to_string(&*redirections.borrow()).unwrap();
+                shared.ensure_dir(&self.dst.join(crate_name.as_str()))?;
+                shared.fs.write(redirect_map_path, paths)?;
+            }
+        }
+
+        // No need for it anymore.
+        drop(shared);
+
+        // Flush pending errors.
+        Rc::get_mut(&mut self.shared).unwrap().fs.close();
+        let nb_errors =
+            self.shared.errors.iter().map(|err| self.tcx().sess.struct_err(&err).emit()).count();
+        if nb_errors > 0 {
+            Err(Error::new(io::Error::new(io::ErrorKind::Other, "I/O error"), ""))
+        } else {
+            Ok(())
+        }
+    }
+
+    fn mod_item_in(&mut self, item: &clean::Item) -> Result<(), Error> {
+        // Stripped modules survive the rustdoc passes (i.e., `strip-private`)
+        // if they contain impls for public types. These modules can also
+        // contain items such as publicly re-exported structures.
+        //
+        // External crates will provide links to these structures, so
+        // these modules are recursed into, but not rendered normally
+        // (a flag on the context).
+        if !self.render_redirect_pages {
+            self.render_redirect_pages = item.is_stripped();
+        }
+        let item_name = item.name.unwrap();
+        self.dst.push(&*item_name.as_str());
+        self.current.push(item_name);
+
+        info!("Recursing into {}", self.dst.display());
+
+        let buf = self.render_item(item, true);
+        // buf will be empty if the module is stripped and there is no redirect for it
+        if !buf.is_empty() {
+            self.shared.ensure_dir(&self.dst)?;
+            let joint_dst = self.dst.join("index.html");
+            self.shared.fs.write(joint_dst, buf)?;
+        }
+
+        // Render sidebar-items.js used throughout this module.
+        if !self.render_redirect_pages {
+            let (clean::StrippedItem(box clean::ModuleItem(ref module)) | clean::ModuleItem(ref module)) = *item.kind
+            else { unreachable!() };
+            let items = self.build_sidebar_items(module);
+            let js_dst = self.dst.join(&format!("sidebar-items{}.js", self.shared.resource_suffix));
+            let v = format!("window.SIDEBAR_ITEMS = {};", serde_json::to_string(&items).unwrap());
+            self.shared.fs.write(js_dst, v)?;
+        }
+        Ok(())
+    }
+
+    fn mod_item_out(&mut self) -> Result<(), Error> {
+        info!("Recursed; leaving {}", self.dst.display());
+
+        // Go back to where we were at
+        self.dst.pop();
+        self.current.pop();
+        Ok(())
+    }
+
+    fn item(&mut self, item: clean::Item) -> Result<(), Error> {
+        // Stripped modules survive the rustdoc passes (i.e., `strip-private`)
+        // if they contain impls for public types. These modules can also
+        // contain items such as publicly re-exported structures.
+        //
+        // External crates will provide links to these structures, so
+        // these modules are recursed into, but not rendered normally
+        // (a flag on the context).
+        if !self.render_redirect_pages {
+            self.render_redirect_pages = item.is_stripped();
+        }
+
+        let buf = self.render_item(&item, false);
+        // buf will be empty if the item is stripped and there is no redirect for it
+        if !buf.is_empty() {
+            let name = item.name.as_ref().unwrap();
+            let item_type = item.type_();
+            let file_name = &item_path(item_type, name.as_str());
+            self.shared.ensure_dir(&self.dst)?;
+            let joint_dst = self.dst.join(file_name);
+            self.shared.fs.write(joint_dst, buf)?;
+
+            if !self.render_redirect_pages {
+                self.shared.all.borrow_mut().append(full_path(self, &item), &item_type);
+            }
+            // If the item is a macro, redirect from the old macro URL (with !)
+            // to the new one (without).
+            if item_type == ItemType::Macro {
+                let redir_name = format!("{}.{}!.html", item_type, name);
+                if let Some(ref redirections) = self.shared.redirections {
+                    let crate_name = &self.shared.layout.krate;
+                    redirections.borrow_mut().insert(
+                        format!("{}/{}", crate_name, redir_name),
+                        format!("{}/{}", crate_name, file_name),
+                    );
+                } else {
+                    let v = layout::redirect(file_name);
+                    let redir_dst = self.dst.join(redir_name);
+                    self.shared.fs.write(redir_dst, v)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn cache(&self) -> &Cache {
+        &self.shared.cache
+    }
+}
+
+fn make_item_keywords(it: &clean::Item) -> String {
+    format!("{}, {}", BASIC_KEYWORDS, it.name.as_ref().unwrap())
+}
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
new file mode 100644
index 000000000..a262c8f7d
--- /dev/null
+++ b/src/librustdoc/html/render/mod.rs
@@ -0,0 +1,2849 @@
+//! Rustdoc's HTML rendering module.
+//!
+//! This modules contains the bulk of the logic necessary for rendering a
+//! rustdoc `clean::Crate` instance to a set of static HTML pages. This
+//! rendering process is largely driven by the `format!` syntax extension to
+//! perform all I/O into files and streams.
+//!
+//! The rendering process is largely driven by the `Context` and `Cache`
+//! structures. The cache is pre-populated by crawling the crate in question,
+//! and then it is shared among the various rendering threads. The cache is meant
+//! to be a fairly large structure not implementing `Clone` (because it's shared
+//! among threads). The context, however, should be a lightweight structure. This
+//! is cloned per-thread and contains information about what is currently being
+//! rendered.
+//!
+//! In order to speed up rendering (mostly because of markdown rendering), the
+//! rendering process has been parallelized. This parallelization is only
+//! exposed through the `crate` method on the context, and then also from the
+//! fact that the shared cache is stored in TLS (and must be accessed as such).
+//!
+//! In addition to rendering the crate itself, this module is also responsible
+//! for creating the corresponding search index and source file renderings.
+//! These threads are not parallelized (they haven't been a bottleneck yet), and
+//! both occur before the crate is rendered.
+
+pub(crate) mod search_index;
+
+#[cfg(test)]
+mod tests;
+
+mod context;
+mod print_item;
+mod span_map;
+mod write_shared;
+
+pub(crate) use self::context::*;
+pub(crate) use self::span_map::{collect_spans_and_sources, LinkFromSrc};
+
+use std::collections::VecDeque;
+use std::default::Default;
+use std::fmt;
+use std::fs;
+use std::iter::Peekable;
+use std::path::PathBuf;
+use std::rc::Rc;
+use std::str;
+use std::string::ToString;
+
+use rustc_ast_pretty::pprust;
+use rustc_attr::{ConstStability, Deprecation, StabilityLevel};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def::CtorKind;
+use rustc_hir::def_id::DefId;
+use rustc_hir::Mutability;
+use rustc_middle::middle::stability;
+use rustc_middle::ty;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::{
+    symbol::{sym, Symbol},
+    BytePos, FileName, RealFileName,
+};
+use serde::ser::SerializeSeq;
+use serde::{Serialize, Serializer};
+
+use crate::clean::{self, ItemId, RenderedLink, SelfTy};
+use crate::error::Error;
+use crate::formats::cache::Cache;
+use crate::formats::item_type::ItemType;
+use crate::formats::{AssocItemRender, Impl, RenderMode};
+use crate::html::escape::Escape;
+use crate::html::format::{
+    href, join_with_double_colon, print_abi_with_space, print_constness_with_space,
+    print_default_space, print_generic_bounds, print_where_clause, Buffer, Ending, HrefError,
+    PrintWithSpace,
+};
+use crate::html::highlight;
+use crate::html::markdown::{HeadingOffset, IdMap, Markdown, MarkdownHtml, MarkdownSummaryLine};
+use crate::html::sources;
+use crate::html::static_files::SCRAPE_EXAMPLES_HELP_MD;
+use crate::scrape_examples::{CallData, CallLocation};
+use crate::try_none;
+use crate::DOC_RUST_LANG_ORG_CHANNEL;
+
+/// A pair of name and its optional document.
+pub(crate) type NameDoc = (String, Option<String>);
+
+pub(crate) fn ensure_trailing_slash(v: &str) -> impl fmt::Display + '_ {
+    crate::html::format::display_fn(move |f| {
+        if !v.ends_with('/') && !v.is_empty() { write!(f, "{}/", v) } else { f.write_str(v) }
+    })
+}
+
+// Helper structs for rendering items/sidebars and carrying along contextual
+// information
+
+/// Struct representing one entry in the JS search index. These are all emitted
+/// by hand to a large JS file at the end of cache-creation.
+#[derive(Debug)]
+pub(crate) struct IndexItem {
+    pub(crate) ty: ItemType,
+    pub(crate) name: String,
+    pub(crate) path: String,
+    pub(crate) desc: String,
+    pub(crate) parent: Option<DefId>,
+    pub(crate) parent_idx: Option<usize>,
+    pub(crate) search_type: Option<IndexItemFunctionType>,
+    pub(crate) aliases: Box<[Symbol]>,
+}
+
+/// A type used for the search index.
+#[derive(Debug)]
+pub(crate) struct RenderType {
+    id: Option<RenderTypeId>,
+    generics: Option<Vec<RenderType>>,
+}
+
+impl Serialize for RenderType {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let id = match &self.id {
+            // 0 is a sentinel, everything else is one-indexed
+            None => 0,
+            Some(RenderTypeId::Index(idx)) => idx + 1,
+            _ => panic!("must convert render types to indexes before serializing"),
+        };
+        if let Some(generics) = &self.generics {
+            let mut seq = serializer.serialize_seq(None)?;
+            seq.serialize_element(&id)?;
+            seq.serialize_element(generics)?;
+            seq.end()
+        } else {
+            id.serialize(serializer)
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(crate) enum RenderTypeId {
+    DefId(DefId),
+    Primitive(clean::PrimitiveType),
+    Index(usize),
+}
+
+/// Full type of functions/methods in the search index.
+#[derive(Debug)]
+pub(crate) struct IndexItemFunctionType {
+    inputs: Vec<RenderType>,
+    output: Vec<RenderType>,
+}
+
+impl Serialize for IndexItemFunctionType {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        // If we couldn't figure out a type, just write `0`.
+        let has_missing = self
+            .inputs
+            .iter()
+            .chain(self.output.iter())
+            .any(|i| i.id.is_none() && i.generics.is_none());
+        if has_missing {
+            0.serialize(serializer)
+        } else {
+            let mut seq = serializer.serialize_seq(None)?;
+            match &self.inputs[..] {
+                [one] if one.generics.is_none() => seq.serialize_element(one)?,
+                _ => seq.serialize_element(&self.inputs)?,
+            }
+            match &self.output[..] {
+                [] => {}
+                [one] if one.generics.is_none() => seq.serialize_element(one)?,
+                _ => seq.serialize_element(&self.output)?,
+            }
+            seq.end()
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct StylePath {
+    /// The path to the theme
+    pub(crate) path: PathBuf,
+}
+
+impl StylePath {
+    pub(crate) fn basename(&self) -> Result<String, Error> {
+        Ok(try_none!(try_none!(self.path.file_stem(), &self.path).to_str(), &self.path).to_string())
+    }
+}
+
+fn write_srclink(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer) {
+    if let Some(l) = cx.src_href(item) {
+        write!(buf, "<a class=\"srclink\" href=\"{}\">source</a>", l)
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Hash)]
+struct ItemEntry {
+    url: String,
+    name: String,
+}
+
+impl ItemEntry {
+    fn new(mut url: String, name: String) -> ItemEntry {
+        while url.starts_with('/') {
+            url.remove(0);
+        }
+        ItemEntry { url, name }
+    }
+}
+
+impl ItemEntry {
+    pub(crate) fn print(&self) -> impl fmt::Display + '_ {
+        crate::html::format::display_fn(move |f| {
+            write!(f, "<a href=\"{}\">{}</a>", self.url, Escape(&self.name))
+        })
+    }
+}
+
+impl PartialOrd for ItemEntry {
+    fn partial_cmp(&self, other: &ItemEntry) -> Option<::std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for ItemEntry {
+    fn cmp(&self, other: &ItemEntry) -> ::std::cmp::Ordering {
+        self.name.cmp(&other.name)
+    }
+}
+
+#[derive(Debug)]
+struct AllTypes {
+    structs: FxHashSet<ItemEntry>,
+    enums: FxHashSet<ItemEntry>,
+    unions: FxHashSet<ItemEntry>,
+    primitives: FxHashSet<ItemEntry>,
+    traits: FxHashSet<ItemEntry>,
+    macros: FxHashSet<ItemEntry>,
+    functions: FxHashSet<ItemEntry>,
+    typedefs: FxHashSet<ItemEntry>,
+    opaque_tys: FxHashSet<ItemEntry>,
+    statics: FxHashSet<ItemEntry>,
+    constants: FxHashSet<ItemEntry>,
+    attributes: FxHashSet<ItemEntry>,
+    derives: FxHashSet<ItemEntry>,
+    trait_aliases: FxHashSet<ItemEntry>,
+}
+
+impl AllTypes {
+    fn new() -> AllTypes {
+        let new_set = |cap| FxHashSet::with_capacity_and_hasher(cap, Default::default());
+        AllTypes {
+            structs: new_set(100),
+            enums: new_set(100),
+            unions: new_set(100),
+            primitives: new_set(26),
+            traits: new_set(100),
+            macros: new_set(100),
+            functions: new_set(100),
+            typedefs: new_set(100),
+            opaque_tys: new_set(100),
+            statics: new_set(100),
+            constants: new_set(100),
+            attributes: new_set(100),
+            derives: new_set(100),
+            trait_aliases: new_set(100),
+        }
+    }
+
+    fn append(&mut self, item_name: String, item_type: &ItemType) {
+        let mut url: Vec<_> = item_name.split("::").skip(1).collect();
+        if let Some(name) = url.pop() {
+            let new_url = format!("{}/{}.{}.html", url.join("/"), item_type, name);
+            url.push(name);
+            let name = url.join("::");
+            match *item_type {
+                ItemType::Struct => self.structs.insert(ItemEntry::new(new_url, name)),
+                ItemType::Enum => self.enums.insert(ItemEntry::new(new_url, name)),
+                ItemType::Union => self.unions.insert(ItemEntry::new(new_url, name)),
+                ItemType::Primitive => self.primitives.insert(ItemEntry::new(new_url, name)),
+                ItemType::Trait => self.traits.insert(ItemEntry::new(new_url, name)),
+                ItemType::Macro => self.macros.insert(ItemEntry::new(new_url, name)),
+                ItemType::Function => self.functions.insert(ItemEntry::new(new_url, name)),
+                ItemType::Typedef => self.typedefs.insert(ItemEntry::new(new_url, name)),
+                ItemType::OpaqueTy => self.opaque_tys.insert(ItemEntry::new(new_url, name)),
+                ItemType::Static => self.statics.insert(ItemEntry::new(new_url, name)),
+                ItemType::Constant => self.constants.insert(ItemEntry::new(new_url, name)),
+                ItemType::ProcAttribute => self.attributes.insert(ItemEntry::new(new_url, name)),
+                ItemType::ProcDerive => self.derives.insert(ItemEntry::new(new_url, name)),
+                ItemType::TraitAlias => self.trait_aliases.insert(ItemEntry::new(new_url, name)),
+                _ => true,
+            };
+        }
+    }
+}
+
+impl AllTypes {
+    fn print(self, f: &mut Buffer) {
+        fn print_entries(f: &mut Buffer, e: &FxHashSet<ItemEntry>, title: &str, class: &str) {
+            if !e.is_empty() {
+                let mut e: Vec<&ItemEntry> = e.iter().collect();
+                e.sort();
+                write!(
+                    f,
+                    "<h3 id=\"{}\">{}</h3><ul class=\"{} docblock\">",
+                    title.replace(' ', "-"), // IDs cannot contain whitespaces.
+                    title,
+                    class
+                );
+
+                for s in e.iter() {
+                    write!(f, "<li>{}</li>", s.print());
+                }
+
+                f.write_str("</ul>");
+            }
+        }
+
+        f.write_str(
+            "<h1 class=\"fqn\">\
+                 <span class=\"in-band\">List of all items</span>\
+             </h1>",
+        );
+        // Note: print_entries does not escape the title, because we know the current set of titles
+        // doesn't require escaping.
+        print_entries(f, &self.structs, "Structs", "structs");
+        print_entries(f, &self.enums, "Enums", "enums");
+        print_entries(f, &self.unions, "Unions", "unions");
+        print_entries(f, &self.primitives, "Primitives", "primitives");
+        print_entries(f, &self.traits, "Traits", "traits");
+        print_entries(f, &self.macros, "Macros", "macros");
+        print_entries(f, &self.attributes, "Attribute Macros", "attributes");
+        print_entries(f, &self.derives, "Derive Macros", "derives");
+        print_entries(f, &self.functions, "Functions", "functions");
+        print_entries(f, &self.typedefs, "Typedefs", "typedefs");
+        print_entries(f, &self.trait_aliases, "Trait Aliases", "trait-aliases");
+        print_entries(f, &self.opaque_tys, "Opaque Types", "opaque-types");
+        print_entries(f, &self.statics, "Statics", "statics");
+        print_entries(f, &self.constants, "Constants", "constants")
+    }
+}
+
+fn scrape_examples_help(shared: &SharedContext<'_>) -> String {
+    let mut content = SCRAPE_EXAMPLES_HELP_MD.to_owned();
+    content.push_str(&format!(
+      "## More information\n\n\
+      If you want more information about this feature, please read the [corresponding chapter in the Rustdoc book]({}/rustdoc/scraped-examples.html).",
+      DOC_RUST_LANG_ORG_CHANNEL));
+
+    let mut ids = IdMap::default();
+    format!(
+        "<div class=\"main-heading\">\
+            <h1 class=\"fqn\">\
+                <span class=\"in-band\">About scraped examples</span>\
+            </h1>\
+        </div>\
+        <div>{}</div>",
+        Markdown {
+            content: &content,
+            links: &[],
+            ids: &mut ids,
+            error_codes: shared.codes,
+            edition: shared.edition(),
+            playground: &shared.playground,
+            heading_offset: HeadingOffset::H1
+        }
+        .into_string()
+    )
+}
+
+fn document(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    item: &clean::Item,
+    parent: Option<&clean::Item>,
+    heading_offset: HeadingOffset,
+) {
+    if let Some(ref name) = item.name {
+        info!("Documenting {}", name);
+    }
+    document_item_info(w, cx, item, parent);
+    if parent.is_none() {
+        document_full_collapsible(w, item, cx, heading_offset);
+    } else {
+        document_full(w, item, cx, heading_offset);
+    }
+}
+
+/// Render md_text as markdown.
+fn render_markdown(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    md_text: &str,
+    links: Vec<RenderedLink>,
+    heading_offset: HeadingOffset,
+) {
+    write!(
+        w,
+        "<div class=\"docblock\">{}</div>",
+        Markdown {
+            content: md_text,
+            links: &links,
+            ids: &mut cx.id_map,
+            error_codes: cx.shared.codes,
+            edition: cx.shared.edition(),
+            playground: &cx.shared.playground,
+            heading_offset,
+        }
+        .into_string()
+    )
+}
+
+/// Writes a documentation block containing only the first paragraph of the documentation. If the
+/// docs are longer, a "Read more" link is appended to the end.
+fn document_short(
+    w: &mut Buffer,
+    item: &clean::Item,
+    cx: &mut Context<'_>,
+    link: AssocItemLink<'_>,
+    parent: &clean::Item,
+    show_def_docs: bool,
+) {
+    document_item_info(w, cx, item, Some(parent));
+    if !show_def_docs {
+        return;
+    }
+    if let Some(s) = item.doc_value() {
+        let mut summary_html = MarkdownSummaryLine(&s, &item.links(cx)).into_string();
+
+        if s.contains('\n') {
+            let link = format!(r#" <a{}>Read more</a>"#, assoc_href_attr(item, link, cx));
+
+            if let Some(idx) = summary_html.rfind("</p>") {
+                summary_html.insert_str(idx, &link);
+            } else {
+                summary_html.push_str(&link);
+            }
+        }
+
+        write!(w, "<div class='docblock'>{}</div>", summary_html,);
+    }
+}
+
+fn document_full_collapsible(
+    w: &mut Buffer,
+    item: &clean::Item,
+    cx: &mut Context<'_>,
+    heading_offset: HeadingOffset,
+) {
+    document_full_inner(w, item, cx, true, heading_offset);
+}
+
+fn document_full(
+    w: &mut Buffer,
+    item: &clean::Item,
+    cx: &mut Context<'_>,
+    heading_offset: HeadingOffset,
+) {
+    document_full_inner(w, item, cx, false, heading_offset);
+}
+
+fn document_full_inner(
+    w: &mut Buffer,
+    item: &clean::Item,
+    cx: &mut Context<'_>,
+    is_collapsible: bool,
+    heading_offset: HeadingOffset,
+) {
+    if let Some(s) = item.collapsed_doc_value() {
+        debug!("Doc block: =====\n{}\n=====", s);
+        if is_collapsible {
+            w.write_str(
+                "<details class=\"rustdoc-toggle top-doc\" open>\
+                <summary class=\"hideme\">\
+                     <span>Expand description</span>\
+                </summary>",
+            );
+            render_markdown(w, cx, &s, item.links(cx), heading_offset);
+            w.write_str("</details>");
+        } else {
+            render_markdown(w, cx, &s, item.links(cx), heading_offset);
+        }
+    }
+
+    let kind = match &*item.kind {
+        clean::ItemKind::StrippedItem(box kind) | kind => kind,
+    };
+
+    if let clean::ItemKind::FunctionItem(..) | clean::ItemKind::MethodItem(..) = kind {
+        render_call_locations(w, cx, item);
+    }
+}
+
+/// Add extra information about an item such as:
+///
+/// * Stability
+/// * Deprecated
+/// * Required features (through the `doc_cfg` feature)
+fn document_item_info(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    item: &clean::Item,
+    parent: Option<&clean::Item>,
+) {
+    let item_infos = short_item_info(item, cx, parent);
+    if !item_infos.is_empty() {
+        w.write_str("<span class=\"item-info\">");
+        for info in item_infos {
+            w.write_str(&info);
+        }
+        w.write_str("</span>");
+    }
+}
+
+fn portability(item: &clean::Item, parent: Option<&clean::Item>) -> Option<String> {
+    let cfg = match (&item.cfg, parent.and_then(|p| p.cfg.as_ref())) {
+        (Some(cfg), Some(parent_cfg)) => cfg.simplify_with(parent_cfg),
+        (cfg, _) => cfg.as_deref().cloned(),
+    };
+
+    debug!("Portability {:?} - {:?} = {:?}", item.cfg, parent.and_then(|p| p.cfg.as_ref()), cfg);
+
+    Some(format!("<div class=\"stab portability\">{}</div>", cfg?.render_long_html()))
+}
+
+/// Render the stability, deprecation and portability information that is displayed at the top of
+/// the item's documentation.
+fn short_item_info(
+    item: &clean::Item,
+    cx: &mut Context<'_>,
+    parent: Option<&clean::Item>,
+) -> Vec<String> {
+    let mut extra_info = vec![];
+    let error_codes = cx.shared.codes;
+
+    if let Some(depr @ Deprecation { note, since, is_since_rustc_version: _, suggestion: _ }) =
+        item.deprecation(cx.tcx())
+    {
+        // We display deprecation messages for #[deprecated], but only display
+        // the future-deprecation messages for rustc versions.
+        let mut message = if let Some(since) = since {
+            let since = since.as_str();
+            if !stability::deprecation_in_effect(&depr) {
+                if since == "TBD" {
+                    String::from("Deprecating in a future Rust version")
+                } else {
+                    format!("Deprecating in {}", Escape(since))
+                }
+            } else {
+                format!("Deprecated since {}", Escape(since))
+            }
+        } else {
+            String::from("Deprecated")
+        };
+
+        if let Some(note) = note {
+            let note = note.as_str();
+            let html = MarkdownHtml(
+                note,
+                &mut cx.id_map,
+                error_codes,
+                cx.shared.edition(),
+                &cx.shared.playground,
+            );
+            message.push_str(&format!(": {}", html.into_string()));
+        }
+        extra_info.push(format!(
+            "<div class=\"stab deprecated\"><span class=\"emoji\">👎</span> {}</div>",
+            message,
+        ));
+    }
+
+    // Render unstable items. But don't render "rustc_private" crates (internal compiler crates).
+    // Those crates are permanently unstable so it makes no sense to render "unstable" everywhere.
+    if let Some((StabilityLevel::Unstable { reason: _, issue, .. }, feature)) = item
+        .stability(cx.tcx())
+        .as_ref()
+        .filter(|stab| stab.feature != sym::rustc_private)
+        .map(|stab| (stab.level, stab.feature))
+    {
+        let mut message =
+            "<span class=\"emoji\">🔬</span> This is a nightly-only experimental API.".to_owned();
+
+        let mut feature = format!("<code>{}</code>", Escape(feature.as_str()));
+        if let (Some(url), Some(issue)) = (&cx.shared.issue_tracker_base_url, issue) {
+            feature.push_str(&format!(
+                "&nbsp;<a href=\"{url}{issue}\">#{issue}</a>",
+                url = url,
+                issue = issue
+            ));
+        }
+
+        message.push_str(&format!(" ({})", feature));
+
+        extra_info.push(format!("<div class=\"stab unstable\">{}</div>", message));
+    }
+
+    if let Some(portability) = portability(item, parent) {
+        extra_info.push(portability);
+    }
+
+    extra_info
+}
+
+// Render the list of items inside one of the sections "Trait Implementations",
+// "Auto Trait Implementations," "Blanket Trait Implementations" (on struct/enum pages).
+fn render_impls(
+    cx: &mut Context<'_>,
+    w: &mut Buffer,
+    impls: &[&&Impl],
+    containing_item: &clean::Item,
+    toggle_open_by_default: bool,
+) {
+    let tcx = cx.tcx();
+    let mut rendered_impls = impls
+        .iter()
+        .map(|i| {
+            let did = i.trait_did().unwrap();
+            let provided_trait_methods = i.inner_impl().provided_trait_methods(tcx);
+            let assoc_link = AssocItemLink::GotoSource(did.into(), &provided_trait_methods);
+            let mut buffer = if w.is_for_html() { Buffer::html() } else { Buffer::new() };
+            render_impl(
+                &mut buffer,
+                cx,
+                i,
+                containing_item,
+                assoc_link,
+                RenderMode::Normal,
+                None,
+                &[],
+                ImplRenderingParameters {
+                    show_def_docs: true,
+                    show_default_items: true,
+                    show_non_assoc_items: true,
+                    toggle_open_by_default,
+                },
+            );
+            buffer.into_inner()
+        })
+        .collect::<Vec<_>>();
+    rendered_impls.sort();
+    w.write_str(&rendered_impls.join(""));
+}
+
+/// Build a (possibly empty) `href` attribute (a key-value pair) for the given associated item.
+fn assoc_href_attr(it: &clean::Item, link: AssocItemLink<'_>, cx: &Context<'_>) -> String {
+    let name = it.name.unwrap();
+    let item_type = it.type_();
+
+    let href = match link {
+        AssocItemLink::Anchor(Some(ref id)) => Some(format!("#{}", id)),
+        AssocItemLink::Anchor(None) => Some(format!("#{}.{}", item_type, name)),
+        AssocItemLink::GotoSource(did, provided_methods) => {
+            // We're creating a link from the implementation of an associated item to its
+            // declaration in the trait declaration.
+            let item_type = match item_type {
+                // For historical but not technical reasons, the item type of methods in
+                // trait declarations depends on whether the method is required (`TyMethod`) or
+                // provided (`Method`).
+                ItemType::Method | ItemType::TyMethod => {
+                    if provided_methods.contains(&name) {
+                        ItemType::Method
+                    } else {
+                        ItemType::TyMethod
+                    }
+                }
+                // For associated types and constants, no such distinction exists.
+                item_type => item_type,
+            };
+
+            match href(did.expect_def_id(), cx) {
+                Ok((url, ..)) => Some(format!("{}#{}.{}", url, item_type, name)),
+                // The link is broken since it points to an external crate that wasn't documented.
+                // Do not create any link in such case. This is better than falling back to a
+                // dummy anchor like `#{item_type}.{name}` representing the `id` of *this* impl item
+                // (that used to happen in older versions). Indeed, in most cases this dummy would
+                // coincide with the `id`. However, it would not always do so.
+                // In general, this dummy would be incorrect:
+                // If the type with the trait impl also had an inherent impl with an assoc. item of
+                // the *same* name as this impl item, the dummy would link to that one even though
+                // those two items are distinct!
+                // In this scenario, the actual `id` of this impl item would be
+                // `#{item_type}.{name}-{n}` for some number `n` (a disambiguator).
+                Err(HrefError::DocumentationNotBuilt) => None,
+                Err(_) => Some(format!("#{}.{}", item_type, name)),
+            }
+        }
+    };
+
+    // If there is no `href` for the reason explained above, simply do not render it which is valid:
+    // https://html.spec.whatwg.org/multipage/links.html#links-created-by-a-and-area-elements
+    href.map(|href| format!(" href=\"{}\"", href)).unwrap_or_default()
+}
+
+fn assoc_const(
+    w: &mut Buffer,
+    it: &clean::Item,
+    ty: &clean::Type,
+    default: Option<&clean::ConstantKind>,
+    link: AssocItemLink<'_>,
+    extra: &str,
+    cx: &Context<'_>,
+) {
+    write!(
+        w,
+        "{extra}{vis}const <a{href} class=\"constant\">{name}</a>: {ty}",
+        extra = extra,
+        vis = it.visibility.print_with_space(it.item_id, cx),
+        href = assoc_href_attr(it, link, cx),
+        name = it.name.as_ref().unwrap(),
+        ty = ty.print(cx),
+    );
+    if let Some(default) = default {
+        write!(w, " = ");
+
+        // FIXME: `.value()` uses `clean::utils::format_integer_with_underscore_sep` under the
+        //        hood which adds noisy underscores and a type suffix to number literals.
+        //        This hurts readability in this context especially when more complex expressions
+        //        are involved and it doesn't add much of value.
+        //        Find a way to print constants here without all that jazz.
+        write!(w, "{}", Escape(&default.value(cx.tcx()).unwrap_or_else(|| default.expr(cx.tcx()))));
+    }
+}
+
+fn assoc_type(
+    w: &mut Buffer,
+    it: &clean::Item,
+    generics: &clean::Generics,
+    bounds: &[clean::GenericBound],
+    default: Option<&clean::Type>,
+    link: AssocItemLink<'_>,
+    indent: usize,
+    cx: &Context<'_>,
+) {
+    write!(
+        w,
+        "{indent}type <a{href} class=\"associatedtype\">{name}</a>{generics}",
+        indent = " ".repeat(indent),
+        href = assoc_href_attr(it, link, cx),
+        name = it.name.as_ref().unwrap(),
+        generics = generics.print(cx),
+    );
+    if !bounds.is_empty() {
+        write!(w, ": {}", print_generic_bounds(bounds, cx))
+    }
+    write!(w, "{}", print_where_clause(generics, cx, indent, Ending::NoNewline));
+    if let Some(default) = default {
+        write!(w, " = {}", default.print(cx))
+    }
+}
+
+fn assoc_method(
+    w: &mut Buffer,
+    meth: &clean::Item,
+    g: &clean::Generics,
+    d: &clean::FnDecl,
+    link: AssocItemLink<'_>,
+    parent: ItemType,
+    cx: &Context<'_>,
+    render_mode: RenderMode,
+) {
+    let header = meth.fn_header(cx.tcx()).expect("Trying to get header from a non-function item");
+    let name = meth.name.as_ref().unwrap();
+    let vis = meth.visibility.print_with_space(meth.item_id, cx).to_string();
+    // FIXME: Once https://github.com/rust-lang/rust/issues/67792 is implemented, we can remove
+    // this condition.
+    let constness = match render_mode {
+        RenderMode::Normal => {
+            print_constness_with_space(&header.constness, meth.const_stability(cx.tcx()))
+        }
+        RenderMode::ForDeref { .. } => "",
+    };
+    let asyncness = header.asyncness.print_with_space();
+    let unsafety = header.unsafety.print_with_space();
+    let defaultness = print_default_space(meth.is_default());
+    let abi = print_abi_with_space(header.abi).to_string();
+    let href = assoc_href_attr(meth, link, cx);
+
+    // NOTE: `{:#}` does not print HTML formatting, `{}` does. So `g.print` can't be reused between the length calculation and `write!`.
+    let generics_len = format!("{:#}", g.print(cx)).len();
+    let mut header_len = "fn ".len()
+        + vis.len()
+        + constness.len()
+        + asyncness.len()
+        + unsafety.len()
+        + defaultness.len()
+        + abi.len()
+        + name.as_str().len()
+        + generics_len;
+
+    let (indent, indent_str, end_newline) = if parent == ItemType::Trait {
+        header_len += 4;
+        let indent_str = "    ";
+        render_attributes_in_pre(w, meth, indent_str);
+        (4, indent_str, Ending::NoNewline)
+    } else {
+        render_attributes_in_code(w, meth);
+        (0, "", Ending::Newline)
+    };
+    w.reserve(header_len + "<a href=\"\" class=\"fnname\">{".len() + "</a>".len());
+    write!(
+        w,
+        "{indent}{vis}{constness}{asyncness}{unsafety}{defaultness}{abi}fn <a{href} class=\"fnname\">{name}</a>\
+         {generics}{decl}{notable_traits}{where_clause}",
+        indent = indent_str,
+        vis = vis,
+        constness = constness,
+        asyncness = asyncness,
+        unsafety = unsafety,
+        defaultness = defaultness,
+        abi = abi,
+        href = href,
+        name = name,
+        generics = g.print(cx),
+        decl = d.full_print(header_len, indent, header.asyncness, cx),
+        notable_traits = notable_traits_decl(d, cx),
+        where_clause = print_where_clause(g, cx, indent, end_newline),
+    )
+}
+
+/// Writes a span containing the versions at which an item became stable and/or const-stable. For
+/// example, if the item became stable at 1.0.0, and const-stable at 1.45.0, this function would
+/// write a span containing "1.0.0 (const: 1.45.0)".
+///
+/// Returns `true` if a stability annotation was rendered.
+///
+/// Stability and const-stability are considered separately. If the item is unstable, no version
+/// will be written. If the item is const-unstable, "const: unstable" will be appended to the
+/// span, with a link to the tracking issue if present. If an item's stability or const-stability
+/// version matches the version of its enclosing item, that version will be omitted.
+///
+/// Note that it is possible for an unstable function to be const-stable. In that case, the span
+/// will include the const-stable version, but no stable version will be emitted, as a natural
+/// consequence of the above rules.
+fn render_stability_since_raw(
+    w: &mut Buffer,
+    ver: Option<Symbol>,
+    const_stability: Option<ConstStability>,
+    containing_ver: Option<Symbol>,
+    containing_const_ver: Option<Symbol>,
+) -> bool {
+    let stable_version = ver.filter(|inner| !inner.is_empty() && Some(*inner) != containing_ver);
+
+    let mut title = String::new();
+    let mut stability = String::new();
+
+    if let Some(ver) = stable_version {
+        stability.push_str(ver.as_str());
+        title.push_str(&format!("Stable since Rust version {}", ver));
+    }
+
+    let const_title_and_stability = match const_stability {
+        Some(ConstStability { level: StabilityLevel::Stable { since, .. }, .. })
+            if Some(since) != containing_const_ver =>
+        {
+            Some((format!("const since {}", since), format!("const: {}", since)))
+        }
+        Some(ConstStability { level: StabilityLevel::Unstable { issue, .. }, feature, .. }) => {
+            let unstable = if let Some(n) = issue {
+                format!(
+                    r#"<a href="https://github.com/rust-lang/rust/issues/{}" title="Tracking issue for {}">unstable</a>"#,
+                    n, feature
+                )
+            } else {
+                String::from("unstable")
+            };
+
+            Some((String::from("const unstable"), format!("const: {}", unstable)))
+        }
+        _ => None,
+    };
+
+    if let Some((const_title, const_stability)) = const_title_and_stability {
+        if !title.is_empty() {
+            title.push_str(&format!(", {}", const_title));
+        } else {
+            title.push_str(&const_title);
+        }
+
+        if !stability.is_empty() {
+            stability.push_str(&format!(" ({})", const_stability));
+        } else {
+            stability.push_str(&const_stability);
+        }
+    }
+
+    if !stability.is_empty() {
+        write!(w, r#"<span class="since" title="{}">{}</span>"#, title, stability);
+    }
+
+    !stability.is_empty()
+}
+
+fn render_assoc_item(
+    w: &mut Buffer,
+    item: &clean::Item,
+    link: AssocItemLink<'_>,
+    parent: ItemType,
+    cx: &Context<'_>,
+    render_mode: RenderMode,
+) {
+    match &*item.kind {
+        clean::StrippedItem(..) => {}
+        clean::TyMethodItem(m) => {
+            assoc_method(w, item, &m.generics, &m.decl, link, parent, cx, render_mode)
+        }
+        clean::MethodItem(m, _) => {
+            assoc_method(w, item, &m.generics, &m.decl, link, parent, cx, render_mode)
+        }
+        kind @ (clean::TyAssocConstItem(ty) | clean::AssocConstItem(ty, _)) => assoc_const(
+            w,
+            item,
+            ty,
+            match kind {
+                clean::TyAssocConstItem(_) => None,
+                clean::AssocConstItem(_, default) => Some(default),
+                _ => unreachable!(),
+            },
+            link,
+            if parent == ItemType::Trait { "    " } else { "" },
+            cx,
+        ),
+        clean::TyAssocTypeItem(ref generics, ref bounds) => assoc_type(
+            w,
+            item,
+            generics,
+            bounds,
+            None,
+            link,
+            if parent == ItemType::Trait { 4 } else { 0 },
+            cx,
+        ),
+        clean::AssocTypeItem(ref ty, ref bounds) => assoc_type(
+            w,
+            item,
+            &ty.generics,
+            bounds,
+            Some(ty.item_type.as_ref().unwrap_or(&ty.type_)),
+            link,
+            if parent == ItemType::Trait { 4 } else { 0 },
+            cx,
+        ),
+        _ => panic!("render_assoc_item called on non-associated-item"),
+    }
+}
+
+const ALLOWED_ATTRIBUTES: &[Symbol] =
+    &[sym::export_name, sym::link_section, sym::no_mangle, sym::repr, sym::non_exhaustive];
+
+fn attributes(it: &clean::Item) -> Vec<String> {
+    it.attrs
+        .other_attrs
+        .iter()
+        .filter_map(|attr| {
+            if ALLOWED_ATTRIBUTES.contains(&attr.name_or_empty()) {
+                Some(
+                    pprust::attribute_to_string(attr)
+                        .replace("\\\n", "")
+                        .replace('\n', "")
+                        .replace("  ", " "),
+                )
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
+// When an attribute is rendered inside a `<pre>` tag, it is formatted using
+// a whitespace prefix and newline.
+fn render_attributes_in_pre(w: &mut Buffer, it: &clean::Item, prefix: &str) {
+    for a in attributes(it) {
+        writeln!(w, "{}{}", prefix, a);
+    }
+}
+
+// When an attribute is rendered inside a <code> tag, it is formatted using
+// a div to produce a newline after it.
+fn render_attributes_in_code(w: &mut Buffer, it: &clean::Item) {
+    for a in attributes(it) {
+        write!(w, "<div class=\"code-attribute\">{}</div>", a);
+    }
+}
+
+#[derive(Copy, Clone)]
+enum AssocItemLink<'a> {
+    Anchor(Option<&'a str>),
+    GotoSource(ItemId, &'a FxHashSet<Symbol>),
+}
+
+impl<'a> AssocItemLink<'a> {
+    fn anchor(&self, id: &'a str) -> Self {
+        match *self {
+            AssocItemLink::Anchor(_) => AssocItemLink::Anchor(Some(id)),
+            ref other => *other,
+        }
+    }
+}
+
+fn render_assoc_items(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    containing_item: &clean::Item,
+    it: DefId,
+    what: AssocItemRender<'_>,
+) {
+    let mut derefs = FxHashSet::default();
+    derefs.insert(it);
+    render_assoc_items_inner(w, cx, containing_item, it, what, &mut derefs)
+}
+
+fn render_assoc_items_inner(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    containing_item: &clean::Item,
+    it: DefId,
+    what: AssocItemRender<'_>,
+    derefs: &mut FxHashSet<DefId>,
+) {
+    info!("Documenting associated items of {:?}", containing_item.name);
+    let shared = Rc::clone(&cx.shared);
+    let cache = &shared.cache;
+    let Some(v) = cache.impls.get(&it) else { return };
+    let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
+    if !non_trait.is_empty() {
+        let mut tmp_buf = Buffer::empty_from(w);
+        let (render_mode, id) = match what {
+            AssocItemRender::All => {
+                tmp_buf.write_str(
+                    "<h2 id=\"implementations\" class=\"small-section-header\">\
+                         Implementations\
+                         <a href=\"#implementations\" class=\"anchor\"></a>\
+                     </h2>",
+                );
+                (RenderMode::Normal, "implementations-list".to_owned())
+            }
+            AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
+                let id =
+                    cx.derive_id(small_url_encode(format!("deref-methods-{:#}", type_.print(cx))));
+                if let Some(def_id) = type_.def_id(cx.cache()) {
+                    cx.deref_id_map.insert(def_id, id.clone());
+                }
+                write!(
+                    tmp_buf,
+                    "<h2 id=\"{id}\" class=\"small-section-header\">\
+                         <span>Methods from {trait_}&lt;Target = {type_}&gt;</span>\
+                         <a href=\"#{id}\" class=\"anchor\"></a>\
+                     </h2>",
+                    id = id,
+                    trait_ = trait_.print(cx),
+                    type_ = type_.print(cx),
+                );
+                (RenderMode::ForDeref { mut_: deref_mut_ }, cx.derive_id(id))
+            }
+        };
+        let mut impls_buf = Buffer::empty_from(w);
+        for i in &non_trait {
+            render_impl(
+                &mut impls_buf,
+                cx,
+                i,
+                containing_item,
+                AssocItemLink::Anchor(None),
+                render_mode,
+                None,
+                &[],
+                ImplRenderingParameters {
+                    show_def_docs: true,
+                    show_default_items: true,
+                    show_non_assoc_items: true,
+                    toggle_open_by_default: true,
+                },
+            );
+        }
+        if !impls_buf.is_empty() {
+            w.push_buffer(tmp_buf);
+            write!(w, "<div id=\"{}\">", id);
+            w.push_buffer(impls_buf);
+            w.write_str("</div>");
+        }
+    }
+
+    if !traits.is_empty() {
+        let deref_impl =
+            traits.iter().find(|t| t.trait_did() == cx.tcx().lang_items().deref_trait());
+        if let Some(impl_) = deref_impl {
+            let has_deref_mut =
+                traits.iter().any(|t| t.trait_did() == cx.tcx().lang_items().deref_mut_trait());
+            render_deref_methods(w, cx, impl_, containing_item, has_deref_mut, derefs);
+        }
+
+        // If we were already one level into rendering deref methods, we don't want to render
+        // anything after recursing into any further deref methods above.
+        if let AssocItemRender::DerefFor { .. } = what {
+            return;
+        }
+
+        let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) =
+            traits.iter().partition(|t| t.inner_impl().kind.is_auto());
+        let (blanket_impl, concrete): (Vec<&&Impl>, _) =
+            concrete.into_iter().partition(|t| t.inner_impl().kind.is_blanket());
+
+        let mut impls = Buffer::empty_from(w);
+        render_impls(cx, &mut impls, &concrete, containing_item, true);
+        let impls = impls.into_inner();
+        if !impls.is_empty() {
+            write!(
+                w,
+                "<h2 id=\"trait-implementations\" class=\"small-section-header\">\
+                     Trait Implementations\
+                     <a href=\"#trait-implementations\" class=\"anchor\"></a>\
+                 </h2>\
+                 <div id=\"trait-implementations-list\">{}</div>",
+                impls
+            );
+        }
+
+        if !synthetic.is_empty() {
+            w.write_str(
+                "<h2 id=\"synthetic-implementations\" class=\"small-section-header\">\
+                     Auto Trait Implementations\
+                     <a href=\"#synthetic-implementations\" class=\"anchor\"></a>\
+                 </h2>\
+                 <div id=\"synthetic-implementations-list\">",
+            );
+            render_impls(cx, w, &synthetic, containing_item, false);
+            w.write_str("</div>");
+        }
+
+        if !blanket_impl.is_empty() {
+            w.write_str(
+                "<h2 id=\"blanket-implementations\" class=\"small-section-header\">\
+                     Blanket Implementations\
+                     <a href=\"#blanket-implementations\" class=\"anchor\"></a>\
+                 </h2>\
+                 <div id=\"blanket-implementations-list\">",
+            );
+            render_impls(cx, w, &blanket_impl, containing_item, false);
+            w.write_str("</div>");
+        }
+    }
+}
+
+fn render_deref_methods(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    impl_: &Impl,
+    container_item: &clean::Item,
+    deref_mut: bool,
+    derefs: &mut FxHashSet<DefId>,
+) {
+    let cache = cx.cache();
+    let deref_type = impl_.inner_impl().trait_.as_ref().unwrap();
+    let (target, real_target) = impl_
+        .inner_impl()
+        .items
+        .iter()
+        .find_map(|item| match *item.kind {
+            clean::AssocTypeItem(box ref t, _) => Some(match *t {
+                clean::Typedef { item_type: Some(ref type_), .. } => (type_, &t.type_),
+                _ => (&t.type_, &t.type_),
+            }),
+            _ => None,
+        })
+        .expect("Expected associated type binding");
+    debug!("Render deref methods for {:#?}, target {:#?}", impl_.inner_impl().for_, target);
+    let what =
+        AssocItemRender::DerefFor { trait_: deref_type, type_: real_target, deref_mut_: deref_mut };
+    if let Some(did) = target.def_id(cache) {
+        if let Some(type_did) = impl_.inner_impl().for_.def_id(cache) {
+            // `impl Deref<Target = S> for S`
+            if did == type_did || !derefs.insert(did) {
+                // Avoid infinite cycles
+                return;
+            }
+        }
+        render_assoc_items_inner(w, cx, container_item, did, what, derefs);
+    } else if let Some(prim) = target.primitive_type() {
+        if let Some(&did) = cache.primitive_locations.get(&prim) {
+            render_assoc_items_inner(w, cx, container_item, did, what, derefs);
+        }
+    }
+}
+
+fn should_render_item(item: &clean::Item, deref_mut_: bool, tcx: TyCtxt<'_>) -> bool {
+    let self_type_opt = match *item.kind {
+        clean::MethodItem(ref method, _) => method.decl.self_type(),
+        clean::TyMethodItem(ref method) => method.decl.self_type(),
+        _ => None,
+    };
+
+    if let Some(self_ty) = self_type_opt {
+        let (by_mut_ref, by_box, by_value) = match self_ty {
+            SelfTy::SelfBorrowed(_, mutability)
+            | SelfTy::SelfExplicit(clean::BorrowedRef { mutability, .. }) => {
+                (mutability == Mutability::Mut, false, false)
+            }
+            SelfTy::SelfExplicit(clean::Type::Path { path }) => {
+                (false, Some(path.def_id()) == tcx.lang_items().owned_box(), false)
+            }
+            SelfTy::SelfValue => (false, false, true),
+            _ => (false, false, false),
+        };
+
+        (deref_mut_ || !by_mut_ref) && !by_box && !by_value
+    } else {
+        false
+    }
+}
+
+fn notable_traits_decl(decl: &clean::FnDecl, cx: &Context<'_>) -> String {
+    let mut out = Buffer::html();
+
+    if let Some((did, ty)) = decl.output.as_return().and_then(|t| Some((t.def_id(cx.cache())?, t)))
+    {
+        if let Some(impls) = cx.cache().impls.get(&did) {
+            for i in impls {
+                let impl_ = i.inner_impl();
+                if !impl_.for_.without_borrowed_ref().is_same(ty.without_borrowed_ref(), cx.cache())
+                {
+                    // Two different types might have the same did,
+                    // without actually being the same.
+                    continue;
+                }
+                if let Some(trait_) = &impl_.trait_ {
+                    let trait_did = trait_.def_id();
+
+                    if cx.cache().traits.get(&trait_did).map_or(false, |t| t.is_notable) {
+                        if out.is_empty() {
+                            write!(
+                                &mut out,
+                                "<span class=\"notable\">Notable traits for {}</span>\
+                             <code class=\"content\">",
+                                impl_.for_.print(cx)
+                            );
+                        }
+
+                        //use the "where" class here to make it small
+                        write!(
+                            &mut out,
+                            "<span class=\"where fmt-newline\">{}</span>",
+                            impl_.print(false, cx)
+                        );
+                        for it in &impl_.items {
+                            if let clean::AssocTypeItem(ref tydef, ref _bounds) = *it.kind {
+                                out.push_str("<span class=\"where fmt-newline\">    ");
+                                let empty_set = FxHashSet::default();
+                                let src_link =
+                                    AssocItemLink::GotoSource(trait_did.into(), &empty_set);
+                                assoc_type(
+                                    &mut out,
+                                    it,
+                                    &tydef.generics,
+                                    &[], // intentionally leaving out bounds
+                                    Some(&tydef.type_),
+                                    src_link,
+                                    0,
+                                    cx,
+                                );
+                                out.push_str(";</span>");
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    if !out.is_empty() {
+        out.insert_str(
+            0,
+            "<span class=\"notable-traits\"><span class=\"notable-traits-tooltip\">ⓘ\
+            <span class=\"notable-traits-tooltiptext\"><span class=\"docblock\">",
+        );
+        out.push_str("</code></span></span></span></span>");
+    }
+
+    out.into_inner()
+}
+
+#[derive(Clone, Copy, Debug)]
+struct ImplRenderingParameters {
+    show_def_docs: bool,
+    show_default_items: bool,
+    /// Whether or not to show methods.
+    show_non_assoc_items: bool,
+    toggle_open_by_default: bool,
+}
+
+fn render_impl(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    i: &Impl,
+    parent: &clean::Item,
+    link: AssocItemLink<'_>,
+    render_mode: RenderMode,
+    use_absolute: Option<bool>,
+    aliases: &[String],
+    rendering_params: ImplRenderingParameters,
+) {
+    let shared = Rc::clone(&cx.shared);
+    let cache = &shared.cache;
+    let traits = &cache.traits;
+    let trait_ = i.trait_did().map(|did| &traits[&did]);
+    let mut close_tags = String::new();
+
+    // For trait implementations, the `interesting` output contains all methods that have doc
+    // comments, and the `boring` output contains all methods that do not. The distinction is
+    // used to allow hiding the boring methods.
+    // `containing_item` is used for rendering stability info. If the parent is a trait impl,
+    // `containing_item` will the grandparent, since trait impls can't have stability attached.
+    fn doc_impl_item(
+        boring: &mut Buffer,
+        interesting: &mut Buffer,
+        cx: &mut Context<'_>,
+        item: &clean::Item,
+        parent: &clean::Item,
+        containing_item: &clean::Item,
+        link: AssocItemLink<'_>,
+        render_mode: RenderMode,
+        is_default_item: bool,
+        trait_: Option<&clean::Trait>,
+        rendering_params: ImplRenderingParameters,
+    ) {
+        let item_type = item.type_();
+        let name = item.name.as_ref().unwrap();
+
+        let render_method_item = rendering_params.show_non_assoc_items
+            && match render_mode {
+                RenderMode::Normal => true,
+                RenderMode::ForDeref { mut_: deref_mut_ } => {
+                    should_render_item(item, deref_mut_, cx.tcx())
+                }
+            };
+
+        let in_trait_class = if trait_.is_some() { " trait-impl" } else { "" };
+
+        let mut doc_buffer = Buffer::empty_from(boring);
+        let mut info_buffer = Buffer::empty_from(boring);
+        let mut short_documented = true;
+
+        if render_method_item {
+            if !is_default_item {
+                if let Some(t) = trait_ {
+                    // The trait item may have been stripped so we might not
+                    // find any documentation or stability for it.
+                    if let Some(it) = t.items.iter().find(|i| i.name == item.name) {
+                        // We need the stability of the item from the trait
+                        // because impls can't have a stability.
+                        if item.doc_value().is_some() {
+                            document_item_info(&mut info_buffer, cx, it, Some(parent));
+                            document_full(&mut doc_buffer, item, cx, HeadingOffset::H5);
+                            short_documented = false;
+                        } else {
+                            // In case the item isn't documented,
+                            // provide short documentation from the trait.
+                            document_short(
+                                &mut doc_buffer,
+                                it,
+                                cx,
+                                link,
+                                parent,
+                                rendering_params.show_def_docs,
+                            );
+                        }
+                    }
+                } else {
+                    document_item_info(&mut info_buffer, cx, item, Some(parent));
+                    if rendering_params.show_def_docs {
+                        document_full(&mut doc_buffer, item, cx, HeadingOffset::H5);
+                        short_documented = false;
+                    }
+                }
+            } else {
+                document_short(
+                    &mut doc_buffer,
+                    item,
+                    cx,
+                    link,
+                    parent,
+                    rendering_params.show_def_docs,
+                );
+            }
+        }
+        let w = if short_documented && trait_.is_some() { interesting } else { boring };
+
+        let toggled = !doc_buffer.is_empty();
+        if toggled {
+            let method_toggle_class =
+                if item_type == ItemType::Method { " method-toggle" } else { "" };
+            write!(w, "<details class=\"rustdoc-toggle{}\" open><summary>", method_toggle_class);
+        }
+        match &*item.kind {
+            clean::MethodItem(..) | clean::TyMethodItem(_) => {
+                // Only render when the method is not static or we allow static methods
+                if render_method_item {
+                    let id = cx.derive_id(format!("{}.{}", item_type, name));
+                    let source_id = trait_
+                        .and_then(|trait_| {
+                            trait_.items.iter().find(|item| {
+                                item.name.map(|n| n.as_str().eq(name.as_str())).unwrap_or(false)
+                            })
+                        })
+                        .map(|item| format!("{}.{}", item.type_(), name));
+                    write!(
+                        w,
+                        "<section id=\"{}\" class=\"{}{} has-srclink\">",
+                        id, item_type, in_trait_class,
+                    );
+                    render_rightside(w, cx, item, containing_item, render_mode);
+                    if trait_.is_some() {
+                        // Anchors are only used on trait impls.
+                        write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
+                    }
+                    w.write_str("<h4 class=\"code-header\">");
+                    render_assoc_item(
+                        w,
+                        item,
+                        link.anchor(source_id.as_ref().unwrap_or(&id)),
+                        ItemType::Impl,
+                        cx,
+                        render_mode,
+                    );
+                    w.write_str("</h4>");
+                    w.write_str("</section>");
+                }
+            }
+            kind @ (clean::TyAssocConstItem(ty) | clean::AssocConstItem(ty, _)) => {
+                let source_id = format!("{}.{}", item_type, name);
+                let id = cx.derive_id(source_id.clone());
+                write!(
+                    w,
+                    "<section id=\"{}\" class=\"{}{} has-srclink\">",
+                    id, item_type, in_trait_class
+                );
+                render_rightside(w, cx, item, containing_item, render_mode);
+                if trait_.is_some() {
+                    // Anchors are only used on trait impls.
+                    write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
+                }
+                w.write_str("<h4 class=\"code-header\">");
+                assoc_const(
+                    w,
+                    item,
+                    ty,
+                    match kind {
+                        clean::TyAssocConstItem(_) => None,
+                        clean::AssocConstItem(_, default) => Some(default),
+                        _ => unreachable!(),
+                    },
+                    link.anchor(if trait_.is_some() { &source_id } else { &id }),
+                    "",
+                    cx,
+                );
+                w.write_str("</h4>");
+                w.write_str("</section>");
+            }
+            clean::TyAssocTypeItem(generics, bounds) => {
+                let source_id = format!("{}.{}", item_type, name);
+                let id = cx.derive_id(source_id.clone());
+                write!(w, "<section id=\"{}\" class=\"{}{}\">", id, item_type, in_trait_class);
+                if trait_.is_some() {
+                    // Anchors are only used on trait impls.
+                    write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
+                }
+                w.write_str("<h4 class=\"code-header\">");
+                assoc_type(
+                    w,
+                    item,
+                    generics,
+                    bounds,
+                    None,
+                    link.anchor(if trait_.is_some() { &source_id } else { &id }),
+                    0,
+                    cx,
+                );
+                w.write_str("</h4>");
+                w.write_str("</section>");
+            }
+            clean::AssocTypeItem(tydef, _bounds) => {
+                let source_id = format!("{}.{}", item_type, name);
+                let id = cx.derive_id(source_id.clone());
+                write!(
+                    w,
+                    "<section id=\"{}\" class=\"{}{} has-srclink\">",
+                    id, item_type, in_trait_class
+                );
+                if trait_.is_some() {
+                    // Anchors are only used on trait impls.
+                    write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
+                }
+                w.write_str("<h4 class=\"code-header\">");
+                assoc_type(
+                    w,
+                    item,
+                    &tydef.generics,
+                    &[], // intentionally leaving out bounds
+                    Some(tydef.item_type.as_ref().unwrap_or(&tydef.type_)),
+                    link.anchor(if trait_.is_some() { &source_id } else { &id }),
+                    0,
+                    cx,
+                );
+                w.write_str("</h4>");
+                w.write_str("</section>");
+            }
+            clean::StrippedItem(..) => return,
+            _ => panic!("can't make docs for trait item with name {:?}", item.name),
+        }
+
+        w.push_buffer(info_buffer);
+        if toggled {
+            w.write_str("</summary>");
+            w.push_buffer(doc_buffer);
+            w.push_str("</details>");
+        }
+    }
+
+    let mut impl_items = Buffer::empty_from(w);
+    let mut default_impl_items = Buffer::empty_from(w);
+
+    for trait_item in &i.inner_impl().items {
+        doc_impl_item(
+            &mut default_impl_items,
+            &mut impl_items,
+            cx,
+            trait_item,
+            if trait_.is_some() { &i.impl_item } else { parent },
+            parent,
+            link,
+            render_mode,
+            false,
+            trait_.map(|t| &t.trait_),
+            rendering_params,
+        );
+    }
+
+    fn render_default_items(
+        boring: &mut Buffer,
+        interesting: &mut Buffer,
+        cx: &mut Context<'_>,
+        t: &clean::Trait,
+        i: &clean::Impl,
+        parent: &clean::Item,
+        containing_item: &clean::Item,
+        render_mode: RenderMode,
+        rendering_params: ImplRenderingParameters,
+    ) {
+        for trait_item in &t.items {
+            let n = trait_item.name;
+            if i.items.iter().any(|m| m.name == n) {
+                continue;
+            }
+            let did = i.trait_.as_ref().unwrap().def_id();
+            let provided_methods = i.provided_trait_methods(cx.tcx());
+            let assoc_link = AssocItemLink::GotoSource(did.into(), &provided_methods);
+
+            doc_impl_item(
+                boring,
+                interesting,
+                cx,
+                trait_item,
+                parent,
+                containing_item,
+                assoc_link,
+                render_mode,
+                true,
+                Some(t),
+                rendering_params,
+            );
+        }
+    }
+
+    // If we've implemented a trait, then also emit documentation for all
+    // default items which weren't overridden in the implementation block.
+    // We don't emit documentation for default items if they appear in the
+    // Implementations on Foreign Types or Implementors sections.
+    if rendering_params.show_default_items {
+        if let Some(t) = trait_ {
+            render_default_items(
+                &mut default_impl_items,
+                &mut impl_items,
+                cx,
+                &t.trait_,
+                i.inner_impl(),
+                &i.impl_item,
+                parent,
+                render_mode,
+                rendering_params,
+            );
+        }
+    }
+    if render_mode == RenderMode::Normal {
+        let toggled = !(impl_items.is_empty() && default_impl_items.is_empty());
+        if toggled {
+            close_tags.insert_str(0, "</details>");
+            write!(
+                w,
+                "<details class=\"rustdoc-toggle implementors-toggle\"{}>",
+                if rendering_params.toggle_open_by_default { " open" } else { "" }
+            );
+            write!(w, "<summary>")
+        }
+        render_impl_summary(
+            w,
+            cx,
+            i,
+            parent,
+            parent,
+            rendering_params.show_def_docs,
+            use_absolute,
+            aliases,
+        );
+        if toggled {
+            write!(w, "</summary>")
+        }
+
+        if let Some(ref dox) = i.impl_item.collapsed_doc_value() {
+            if trait_.is_none() && i.inner_impl().items.is_empty() {
+                w.write_str(
+                    "<div class=\"item-info\">\
+                    <div class=\"stab empty-impl\">This impl block contains no items.</div>
+                </div>",
+                );
+            }
+            write!(
+                w,
+                "<div class=\"docblock\">{}</div>",
+                Markdown {
+                    content: &*dox,
+                    links: &i.impl_item.links(cx),
+                    ids: &mut cx.id_map,
+                    error_codes: cx.shared.codes,
+                    edition: cx.shared.edition(),
+                    playground: &cx.shared.playground,
+                    heading_offset: HeadingOffset::H4
+                }
+                .into_string()
+            );
+        }
+    }
+    if !default_impl_items.is_empty() || !impl_items.is_empty() {
+        w.write_str("<div class=\"impl-items\">");
+        w.push_buffer(default_impl_items);
+        w.push_buffer(impl_items);
+        close_tags.insert_str(0, "</div>");
+    }
+    w.write_str(&close_tags);
+}
+
+// Render the items that appear on the right side of methods, impls, and
+// associated types. For example "1.0.0 (const: 1.39.0) · source".
+fn render_rightside(
+    w: &mut Buffer,
+    cx: &Context<'_>,
+    item: &clean::Item,
+    containing_item: &clean::Item,
+    render_mode: RenderMode,
+) {
+    let tcx = cx.tcx();
+
+    // FIXME: Once https://github.com/rust-lang/rust/issues/67792 is implemented, we can remove
+    // this condition.
+    let (const_stability, const_stable_since) = match render_mode {
+        RenderMode::Normal => (item.const_stability(tcx), containing_item.const_stable_since(tcx)),
+        RenderMode::ForDeref { .. } => (None, None),
+    };
+
+    let mut rightside = Buffer::new();
+    let has_stability = render_stability_since_raw(
+        &mut rightside,
+        item.stable_since(tcx),
+        const_stability,
+        containing_item.stable_since(tcx),
+        const_stable_since,
+    );
+    let mut srclink = Buffer::empty_from(w);
+    write_srclink(cx, item, &mut srclink);
+    if has_stability && !srclink.is_empty() {
+        rightside.write_str(" · ");
+    }
+    rightside.push_buffer(srclink);
+    if !rightside.is_empty() {
+        write!(w, "<span class=\"rightside\">{}</span>", rightside.into_inner());
+    }
+}
+
+pub(crate) fn render_impl_summary(
+    w: &mut Buffer,
+    cx: &mut Context<'_>,
+    i: &Impl,
+    parent: &clean::Item,
+    containing_item: &clean::Item,
+    show_def_docs: bool,
+    use_absolute: Option<bool>,
+    // This argument is used to reference same type with different paths to avoid duplication
+    // in documentation pages for trait with automatic implementations like "Send" and "Sync".
+    aliases: &[String],
+) {
+    let id =
+        cx.derive_id(get_id_for_impl(&i.inner_impl().for_, i.inner_impl().trait_.as_ref(), cx));
+    let aliases = if aliases.is_empty() {
+        String::new()
+    } else {
+        format!(" data-aliases=\"{}\"", aliases.join(","))
+    };
+    write!(w, "<section id=\"{}\" class=\"impl has-srclink\"{}>", id, aliases);
+    render_rightside(w, cx, &i.impl_item, containing_item, RenderMode::Normal);
+    write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
+    write!(w, "<h3 class=\"code-header in-band\">");
+
+    if let Some(use_absolute) = use_absolute {
+        write!(w, "{}", i.inner_impl().print(use_absolute, cx));
+        if show_def_docs {
+            for it in &i.inner_impl().items {
+                if let clean::AssocTypeItem(ref tydef, ref _bounds) = *it.kind {
+                    w.write_str("<span class=\"where fmt-newline\">  ");
+                    assoc_type(
+                        w,
+                        it,
+                        &tydef.generics,
+                        &[], // intentionally leaving out bounds
+                        Some(&tydef.type_),
+                        AssocItemLink::Anchor(None),
+                        0,
+                        cx,
+                    );
+                    w.write_str(";</span>");
+                }
+            }
+        }
+    } else {
+        write!(w, "{}", i.inner_impl().print(false, cx));
+    }
+    write!(w, "</h3>");
+
+    let is_trait = i.inner_impl().trait_.is_some();
+    if is_trait {
+        if let Some(portability) = portability(&i.impl_item, Some(parent)) {
+            write!(w, "<span class=\"item-info\">{}</span>", portability);
+        }
+    }
+
+    w.write_str("</section>");
+}
+
+fn print_sidebar(cx: &Context<'_>, it: &clean::Item, buffer: &mut Buffer) {
+    if it.is_struct()
+        || it.is_trait()
+        || it.is_primitive()
+        || it.is_union()
+        || it.is_enum()
+        || it.is_mod()
+        || it.is_typedef()
+    {
+        write!(
+            buffer,
+            "<h2 class=\"location\"><a href=\"#\">{}{}</a></h2>",
+            match *it.kind {
+                clean::ModuleItem(..) =>
+                    if it.is_crate() {
+                        "Crate "
+                    } else {
+                        "Module "
+                    },
+                _ => "",
+            },
+            it.name.as_ref().unwrap()
+        );
+    }
+
+    buffer.write_str("<div class=\"sidebar-elems\">");
+    if it.is_crate() {
+        write!(buffer, "<div class=\"block\"><ul>");
+        if let Some(ref version) = cx.cache().crate_version {
+            write!(buffer, "<li class=\"version\">Version {}</li>", Escape(version));
+        }
+        write!(buffer, "<li><a id=\"all-types\" href=\"all.html\">All Items</a></li>");
+        buffer.write_str("</ul></div>");
+    }
+
+    match *it.kind {
+        clean::StructItem(ref s) => sidebar_struct(cx, buffer, it, s),
+        clean::TraitItem(ref t) => sidebar_trait(cx, buffer, it, t),
+        clean::PrimitiveItem(_) => sidebar_primitive(cx, buffer, it),
+        clean::UnionItem(ref u) => sidebar_union(cx, buffer, it, u),
+        clean::EnumItem(ref e) => sidebar_enum(cx, buffer, it, e),
+        clean::TypedefItem(_) => sidebar_typedef(cx, buffer, it),
+        clean::ModuleItem(ref m) => sidebar_module(buffer, &m.items),
+        clean::ForeignTypeItem => sidebar_foreign_type(cx, buffer, it),
+        _ => {}
+    }
+
+    // The sidebar is designed to display sibling functions, modules and
+    // other miscellaneous information. since there are lots of sibling
+    // items (and that causes quadratic growth in large modules),
+    // we refactor common parts into a shared JavaScript file per module.
+    // still, we don't move everything into JS because we want to preserve
+    // as much HTML as possible in order to allow non-JS-enabled browsers
+    // to navigate the documentation (though slightly inefficiently).
+
+    if !it.is_mod() {
+        let path: String = cx.current.iter().map(|s| s.as_str()).intersperse("::").collect();
+
+        write!(buffer, "<h2 class=\"location\"><a href=\"index.html\">In {}</a></h2>", path);
+    }
+
+    // Closes sidebar-elems div.
+    buffer.write_str("</div>");
+}
+
+fn get_next_url(used_links: &mut FxHashSet<String>, url: String) -> String {
+    if used_links.insert(url.clone()) {
+        return url;
+    }
+    let mut add = 1;
+    while !used_links.insert(format!("{}-{}", url, add)) {
+        add += 1;
+    }
+    format!("{}-{}", url, add)
+}
+
+struct SidebarLink {
+    name: Symbol,
+    url: String,
+}
+
+impl fmt::Display for SidebarLink {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "<a href=\"#{}\">{}</a>", self.url, self.name)
+    }
+}
+
+impl PartialEq for SidebarLink {
+    fn eq(&self, other: &Self) -> bool {
+        self.url == other.url
+    }
+}
+
+impl Eq for SidebarLink {}
+
+impl PartialOrd for SidebarLink {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for SidebarLink {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.url.cmp(&other.url)
+    }
+}
+
+fn get_methods(
+    i: &clean::Impl,
+    for_deref: bool,
+    used_links: &mut FxHashSet<String>,
+    deref_mut: bool,
+    tcx: TyCtxt<'_>,
+) -> Vec<SidebarLink> {
+    i.items
+        .iter()
+        .filter_map(|item| match item.name {
+            Some(name) if !name.is_empty() && item.is_method() => {
+                if !for_deref || should_render_item(item, deref_mut, tcx) {
+                    Some(SidebarLink {
+                        name,
+                        url: get_next_url(used_links, format!("{}.{}", ItemType::Method, name)),
+                    })
+                } else {
+                    None
+                }
+            }
+            _ => None,
+        })
+        .collect::<Vec<_>>()
+}
+
+fn get_associated_constants(
+    i: &clean::Impl,
+    used_links: &mut FxHashSet<String>,
+) -> Vec<SidebarLink> {
+    i.items
+        .iter()
+        .filter_map(|item| match item.name {
+            Some(name) if !name.is_empty() && item.is_associated_const() => Some(SidebarLink {
+                name,
+                url: get_next_url(used_links, format!("{}.{}", ItemType::AssocConst, name)),
+            }),
+            _ => None,
+        })
+        .collect::<Vec<_>>()
+}
+
+// The point is to url encode any potential character from a type with genericity.
+fn small_url_encode(s: String) -> String {
+    let mut st = String::new();
+    let mut last_match = 0;
+    for (idx, c) in s.char_indices() {
+        let escaped = match c {
+            '<' => "%3C",
+            '>' => "%3E",
+            ' ' => "%20",
+            '?' => "%3F",
+            '\'' => "%27",
+            '&' => "%26",
+            ',' => "%2C",
+            ':' => "%3A",
+            ';' => "%3B",
+            '[' => "%5B",
+            ']' => "%5D",
+            '"' => "%22",
+            _ => continue,
+        };
+
+        st += &s[last_match..idx];
+        st += escaped;
+        // NOTE: we only expect single byte characters here - which is fine as long as we
+        // only match single byte characters
+        last_match = idx + 1;
+    }
+
+    if last_match != 0 {
+        st += &s[last_match..];
+        st
+    } else {
+        s
+    }
+}
+
+fn sidebar_assoc_items(cx: &Context<'_>, out: &mut Buffer, it: &clean::Item) {
+    let did = it.item_id.expect_def_id();
+    let cache = cx.cache();
+
+    if let Some(v) = cache.impls.get(&did) {
+        let mut used_links = FxHashSet::default();
+        let mut id_map = IdMap::new();
+
+        {
+            let used_links_bor = &mut used_links;
+            let mut assoc_consts = v
+                .iter()
+                .filter(|i| i.inner_impl().trait_.is_none())
+                .flat_map(|i| get_associated_constants(i.inner_impl(), used_links_bor))
+                .collect::<Vec<_>>();
+            if !assoc_consts.is_empty() {
+                // We want links' order to be reproducible so we don't use unstable sort.
+                assoc_consts.sort();
+
+                print_sidebar_block(
+                    out,
+                    "implementations",
+                    "Associated Constants",
+                    assoc_consts.iter(),
+                );
+            }
+            let mut methods = v
+                .iter()
+                .filter(|i| i.inner_impl().trait_.is_none())
+                .flat_map(|i| get_methods(i.inner_impl(), false, used_links_bor, false, cx.tcx()))
+                .collect::<Vec<_>>();
+            if !methods.is_empty() {
+                // We want links' order to be reproducible so we don't use unstable sort.
+                methods.sort();
+
+                print_sidebar_block(out, "implementations", "Methods", methods.iter());
+            }
+        }
+
+        if v.iter().any(|i| i.inner_impl().trait_.is_some()) {
+            if let Some(impl_) =
+                v.iter().find(|i| i.trait_did() == cx.tcx().lang_items().deref_trait())
+            {
+                let mut derefs = FxHashSet::default();
+                derefs.insert(did);
+                sidebar_deref_methods(cx, out, impl_, v, &mut derefs);
+            }
+
+            let format_impls = |impls: Vec<&Impl>, id_map: &mut IdMap| {
+                let mut links = FxHashSet::default();
+
+                let mut ret = impls
+                    .iter()
+                    .filter_map(|it| {
+                        let trait_ = it.inner_impl().trait_.as_ref()?;
+                        let encoded =
+                            id_map.derive(get_id_for_impl(&it.inner_impl().for_, Some(trait_), cx));
+
+                        let i_display = format!("{:#}", trait_.print(cx));
+                        let out = Escape(&i_display);
+                        let prefix = match it.inner_impl().polarity {
+                            ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => "",
+                            ty::ImplPolarity::Negative => "!",
+                        };
+                        let generated = format!("<a href=\"#{}\">{}{}</a>", encoded, prefix, out);
+                        if links.insert(generated.clone()) { Some(generated) } else { None }
+                    })
+                    .collect::<Vec<String>>();
+                ret.sort();
+                ret
+            };
+
+            let (synthetic, concrete): (Vec<&Impl>, Vec<&Impl>) =
+                v.iter().partition::<Vec<_>, _>(|i| i.inner_impl().kind.is_auto());
+            let (blanket_impl, concrete): (Vec<&Impl>, Vec<&Impl>) =
+                concrete.into_iter().partition::<Vec<_>, _>(|i| i.inner_impl().kind.is_blanket());
+
+            let concrete_format = format_impls(concrete, &mut id_map);
+            let synthetic_format = format_impls(synthetic, &mut id_map);
+            let blanket_format = format_impls(blanket_impl, &mut id_map);
+
+            if !concrete_format.is_empty() {
+                print_sidebar_block(
+                    out,
+                    "trait-implementations",
+                    "Trait Implementations",
+                    concrete_format.iter(),
+                );
+            }
+
+            if !synthetic_format.is_empty() {
+                print_sidebar_block(
+                    out,
+                    "synthetic-implementations",
+                    "Auto Trait Implementations",
+                    synthetic_format.iter(),
+                );
+            }
+
+            if !blanket_format.is_empty() {
+                print_sidebar_block(
+                    out,
+                    "blanket-implementations",
+                    "Blanket Implementations",
+                    blanket_format.iter(),
+                );
+            }
+        }
+    }
+}
+
+fn sidebar_deref_methods(
+    cx: &Context<'_>,
+    out: &mut Buffer,
+    impl_: &Impl,
+    v: &[Impl],
+    derefs: &mut FxHashSet<DefId>,
+) {
+    let c = cx.cache();
+
+    debug!("found Deref: {:?}", impl_);
+    if let Some((target, real_target)) =
+        impl_.inner_impl().items.iter().find_map(|item| match *item.kind {
+            clean::AssocTypeItem(box ref t, _) => Some(match *t {
+                clean::Typedef { item_type: Some(ref type_), .. } => (type_, &t.type_),
+                _ => (&t.type_, &t.type_),
+            }),
+            _ => None,
+        })
+    {
+        debug!("found target, real_target: {:?} {:?}", target, real_target);
+        if let Some(did) = target.def_id(c) {
+            if let Some(type_did) = impl_.inner_impl().for_.def_id(c) {
+                // `impl Deref<Target = S> for S`
+                if did == type_did || !derefs.insert(did) {
+                    // Avoid infinite cycles
+                    return;
+                }
+            }
+        }
+        let deref_mut = v.iter().any(|i| i.trait_did() == cx.tcx().lang_items().deref_mut_trait());
+        let inner_impl = target
+            .def_id(c)
+            .or_else(|| {
+                target.primitive_type().and_then(|prim| c.primitive_locations.get(&prim).cloned())
+            })
+            .and_then(|did| c.impls.get(&did));
+        if let Some(impls) = inner_impl {
+            debug!("found inner_impl: {:?}", impls);
+            let mut used_links = FxHashSet::default();
+            let mut ret = impls
+                .iter()
+                .filter(|i| i.inner_impl().trait_.is_none())
+                .flat_map(|i| {
+                    get_methods(i.inner_impl(), true, &mut used_links, deref_mut, cx.tcx())
+                })
+                .collect::<Vec<_>>();
+            if !ret.is_empty() {
+                let id = if let Some(target_def_id) = real_target.def_id(c) {
+                    cx.deref_id_map.get(&target_def_id).expect("Deref section without derived id")
+                } else {
+                    "deref-methods"
+                };
+                let title = format!(
+                    "Methods from {}&lt;Target={}&gt;",
+                    Escape(&format!("{:#}", impl_.inner_impl().trait_.as_ref().unwrap().print(cx))),
+                    Escape(&format!("{:#}", real_target.print(cx))),
+                );
+                // We want links' order to be reproducible so we don't use unstable sort.
+                ret.sort();
+                print_sidebar_block(out, id, &title, ret.iter());
+            }
+        }
+
+        // Recurse into any further impls that might exist for `target`
+        if let Some(target_did) = target.def_id(c) {
+            if let Some(target_impls) = c.impls.get(&target_did) {
+                if let Some(target_deref_impl) = target_impls.iter().find(|i| {
+                    i.inner_impl()
+                        .trait_
+                        .as_ref()
+                        .map(|t| Some(t.def_id()) == cx.tcx().lang_items().deref_trait())
+                        .unwrap_or(false)
+                }) {
+                    sidebar_deref_methods(cx, out, target_deref_impl, target_impls, derefs);
+                }
+            }
+        }
+    }
+}
+
+fn sidebar_struct(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, s: &clean::Struct) {
+    let mut sidebar = Buffer::new();
+    let fields = get_struct_fields_name(&s.fields);
+
+    if !fields.is_empty() {
+        match s.struct_type {
+            CtorKind::Fictive => {
+                print_sidebar_block(&mut sidebar, "fields", "Fields", fields.iter());
+            }
+            CtorKind::Fn => print_sidebar_title(&mut sidebar, "fields", "Tuple Fields"),
+            CtorKind::Const => {}
+        }
+    }
+
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+fn get_id_for_impl(for_: &clean::Type, trait_: Option<&clean::Path>, cx: &Context<'_>) -> String {
+    match trait_ {
+        Some(t) => small_url_encode(format!("impl-{:#}-for-{:#}", t.print(cx), for_.print(cx))),
+        None => small_url_encode(format!("impl-{:#}", for_.print(cx))),
+    }
+}
+
+fn extract_for_impl_name(item: &clean::Item, cx: &Context<'_>) -> Option<(String, String)> {
+    match *item.kind {
+        clean::ItemKind::ImplItem(ref i) => {
+            i.trait_.as_ref().map(|trait_| {
+                // Alternative format produces no URLs,
+                // so this parameter does nothing.
+                (format!("{:#}", i.for_.print(cx)), get_id_for_impl(&i.for_, Some(trait_), cx))
+            })
+        }
+        _ => None,
+    }
+}
+
+/// Don't call this function directly!!! Use `print_sidebar_title` or `print_sidebar_block` instead!
+fn print_sidebar_title_inner(buf: &mut Buffer, id: &str, title: &str) {
+    write!(
+        buf,
+        "<h3 class=\"sidebar-title\">\
+             <a href=\"#{}\">{}</a>\
+         </h3>",
+        id, title
+    );
+}
+
+fn print_sidebar_title(buf: &mut Buffer, id: &str, title: &str) {
+    buf.push_str("<div class=\"block\">");
+    print_sidebar_title_inner(buf, id, title);
+    buf.push_str("</div>");
+}
+
+fn print_sidebar_block(
+    buf: &mut Buffer,
+    id: &str,
+    title: &str,
+    items: impl Iterator<Item = impl fmt::Display>,
+) {
+    buf.push_str("<div class=\"block\">");
+    print_sidebar_title_inner(buf, id, title);
+    buf.push_str("<ul>");
+    for item in items {
+        write!(buf, "<li>{}</li>", item);
+    }
+    buf.push_str("</ul></div>");
+}
+
+fn sidebar_trait(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, t: &clean::Trait) {
+    buf.write_str("<section>");
+
+    fn print_sidebar_section(
+        out: &mut Buffer,
+        items: &[clean::Item],
+        id: &str,
+        title: &str,
+        filter: impl Fn(&clean::Item) -> bool,
+        mapper: impl Fn(&str) -> String,
+    ) {
+        let mut items: Vec<&str> = items
+            .iter()
+            .filter_map(|m| match m.name {
+                Some(ref name) if filter(m) => Some(name.as_str()),
+                _ => None,
+            })
+            .collect::<Vec<_>>();
+
+        if !items.is_empty() {
+            items.sort_unstable();
+            print_sidebar_block(out, id, title, items.into_iter().map(mapper));
+        }
+    }
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "required-associated-types",
+        "Required Associated Types",
+        |m| m.is_ty_associated_type(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::AssocType),
+    );
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "provided-associated-types",
+        "Provided Associated Types",
+        |m| m.is_associated_type(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::AssocType),
+    );
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "required-associated-consts",
+        "Required Associated Constants",
+        |m| m.is_ty_associated_const(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::AssocConst),
+    );
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "provided-associated-consts",
+        "Provided Associated Constants",
+        |m| m.is_associated_const(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::AssocConst),
+    );
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "required-methods",
+        "Required Methods",
+        |m| m.is_ty_method(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::TyMethod),
+    );
+
+    print_sidebar_section(
+        buf,
+        &t.items,
+        "provided-methods",
+        "Provided Methods",
+        |m| m.is_method(),
+        |sym| format!("<a href=\"#{1}.{0}\">{0}</a>", sym, ItemType::Method),
+    );
+
+    if let Some(implementors) = cx.cache().implementors.get(&it.item_id.expect_def_id()) {
+        let mut res = implementors
+            .iter()
+            .filter(|i| !i.is_on_local_type(cx))
+            .filter_map(|i| extract_for_impl_name(&i.impl_item, cx))
+            .collect::<Vec<_>>();
+
+        if !res.is_empty() {
+            res.sort();
+            print_sidebar_block(
+                buf,
+                "foreign-impls",
+                "Implementations on Foreign Types",
+                res.iter().map(|(name, id)| format!("<a href=\"#{}\">{}</a>", id, Escape(name))),
+            );
+        }
+    }
+
+    sidebar_assoc_items(cx, buf, it);
+
+    print_sidebar_title(buf, "implementors", "Implementors");
+    if t.is_auto(cx.tcx()) {
+        print_sidebar_title(buf, "synthetic-implementors", "Auto Implementors");
+    }
+
+    buf.push_str("</section>")
+}
+
+fn sidebar_primitive(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item) {
+    let mut sidebar = Buffer::new();
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+fn sidebar_typedef(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item) {
+    let mut sidebar = Buffer::new();
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+fn get_struct_fields_name(fields: &[clean::Item]) -> Vec<String> {
+    let mut fields = fields
+        .iter()
+        .filter(|f| matches!(*f.kind, clean::StructFieldItem(..)))
+        .filter_map(|f| {
+            f.name.map(|name| format!("<a href=\"#structfield.{name}\">{name}</a>", name = name))
+        })
+        .collect::<Vec<_>>();
+    fields.sort();
+    fields
+}
+
+fn sidebar_union(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, u: &clean::Union) {
+    let mut sidebar = Buffer::new();
+    let fields = get_struct_fields_name(&u.fields);
+
+    if !fields.is_empty() {
+        print_sidebar_block(&mut sidebar, "fields", "Fields", fields.iter());
+    }
+
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+fn sidebar_enum(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, e: &clean::Enum) {
+    let mut sidebar = Buffer::new();
+
+    let mut variants = e
+        .variants()
+        .filter_map(|v| {
+            v.name
+                .as_ref()
+                .map(|name| format!("<a href=\"#variant.{name}\">{name}</a>", name = name))
+        })
+        .collect::<Vec<_>>();
+    if !variants.is_empty() {
+        variants.sort_unstable();
+        print_sidebar_block(&mut sidebar, "variants", "Variants", variants.iter());
+    }
+
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+enum ItemSection {
+    Reexports,
+    PrimitiveTypes,
+    Modules,
+    Macros,
+    Structs,
+    Enums,
+    Constants,
+    Statics,
+    Traits,
+    Functions,
+    TypeDefinitions,
+    Unions,
+    Implementations,
+    TypeMethods,
+    Methods,
+    StructFields,
+    Variants,
+    AssociatedTypes,
+    AssociatedConstants,
+    ForeignTypes,
+    Keywords,
+    OpaqueTypes,
+    AttributeMacros,
+    DeriveMacros,
+    TraitAliases,
+}
+
+impl ItemSection {
+    const ALL: &'static [Self] = {
+        use ItemSection::*;
+        // NOTE: The order here affects the order in the UI.
+        &[
+            Reexports,
+            PrimitiveTypes,
+            Modules,
+            Macros,
+            Structs,
+            Enums,
+            Constants,
+            Statics,
+            Traits,
+            Functions,
+            TypeDefinitions,
+            Unions,
+            Implementations,
+            TypeMethods,
+            Methods,
+            StructFields,
+            Variants,
+            AssociatedTypes,
+            AssociatedConstants,
+            ForeignTypes,
+            Keywords,
+            OpaqueTypes,
+            AttributeMacros,
+            DeriveMacros,
+            TraitAliases,
+        ]
+    };
+
+    fn id(self) -> &'static str {
+        match self {
+            Self::Reexports => "reexports",
+            Self::Modules => "modules",
+            Self::Structs => "structs",
+            Self::Unions => "unions",
+            Self::Enums => "enums",
+            Self::Functions => "functions",
+            Self::TypeDefinitions => "types",
+            Self::Statics => "statics",
+            Self::Constants => "constants",
+            Self::Traits => "traits",
+            Self::Implementations => "impls",
+            Self::TypeMethods => "tymethods",
+            Self::Methods => "methods",
+            Self::StructFields => "fields",
+            Self::Variants => "variants",
+            Self::Macros => "macros",
+            Self::PrimitiveTypes => "primitives",
+            Self::AssociatedTypes => "associated-types",
+            Self::AssociatedConstants => "associated-consts",
+            Self::ForeignTypes => "foreign-types",
+            Self::Keywords => "keywords",
+            Self::OpaqueTypes => "opaque-types",
+            Self::AttributeMacros => "attributes",
+            Self::DeriveMacros => "derives",
+            Self::TraitAliases => "trait-aliases",
+        }
+    }
+
+    fn name(self) -> &'static str {
+        match self {
+            Self::Reexports => "Re-exports",
+            Self::Modules => "Modules",
+            Self::Structs => "Structs",
+            Self::Unions => "Unions",
+            Self::Enums => "Enums",
+            Self::Functions => "Functions",
+            Self::TypeDefinitions => "Type Definitions",
+            Self::Statics => "Statics",
+            Self::Constants => "Constants",
+            Self::Traits => "Traits",
+            Self::Implementations => "Implementations",
+            Self::TypeMethods => "Type Methods",
+            Self::Methods => "Methods",
+            Self::StructFields => "Struct Fields",
+            Self::Variants => "Variants",
+            Self::Macros => "Macros",
+            Self::PrimitiveTypes => "Primitive Types",
+            Self::AssociatedTypes => "Associated Types",
+            Self::AssociatedConstants => "Associated Constants",
+            Self::ForeignTypes => "Foreign Types",
+            Self::Keywords => "Keywords",
+            Self::OpaqueTypes => "Opaque Types",
+            Self::AttributeMacros => "Attribute Macros",
+            Self::DeriveMacros => "Derive Macros",
+            Self::TraitAliases => "Trait Aliases",
+        }
+    }
+}
+
+fn item_ty_to_section(ty: ItemType) -> ItemSection {
+    match ty {
+        ItemType::ExternCrate | ItemType::Import => ItemSection::Reexports,
+        ItemType::Module => ItemSection::Modules,
+        ItemType::Struct => ItemSection::Structs,
+        ItemType::Union => ItemSection::Unions,
+        ItemType::Enum => ItemSection::Enums,
+        ItemType::Function => ItemSection::Functions,
+        ItemType::Typedef => ItemSection::TypeDefinitions,
+        ItemType::Static => ItemSection::Statics,
+        ItemType::Constant => ItemSection::Constants,
+        ItemType::Trait => ItemSection::Traits,
+        ItemType::Impl => ItemSection::Implementations,
+        ItemType::TyMethod => ItemSection::TypeMethods,
+        ItemType::Method => ItemSection::Methods,
+        ItemType::StructField => ItemSection::StructFields,
+        ItemType::Variant => ItemSection::Variants,
+        ItemType::Macro => ItemSection::Macros,
+        ItemType::Primitive => ItemSection::PrimitiveTypes,
+        ItemType::AssocType => ItemSection::AssociatedTypes,
+        ItemType::AssocConst => ItemSection::AssociatedConstants,
+        ItemType::ForeignType => ItemSection::ForeignTypes,
+        ItemType::Keyword => ItemSection::Keywords,
+        ItemType::OpaqueTy => ItemSection::OpaqueTypes,
+        ItemType::ProcAttribute => ItemSection::AttributeMacros,
+        ItemType::ProcDerive => ItemSection::DeriveMacros,
+        ItemType::TraitAlias => ItemSection::TraitAliases,
+    }
+}
+
+fn sidebar_module(buf: &mut Buffer, items: &[clean::Item]) {
+    use std::fmt::Write as _;
+
+    let mut sidebar = String::new();
+
+    let item_sections_in_use: FxHashSet<_> = items
+        .iter()
+        .filter(|it| {
+            !it.is_stripped()
+                && it
+                    .name
+                    .or_else(|| {
+                        if let clean::ImportItem(ref i) = *it.kind &&
+                            let clean::ImportKind::Simple(s) = i.kind { Some(s) } else { None }
+                    })
+                    .is_some()
+        })
+        .map(|it| item_ty_to_section(it.type_()))
+        .collect();
+    for &sec in ItemSection::ALL.iter().filter(|sec| item_sections_in_use.contains(sec)) {
+        let _ = write!(sidebar, "<li><a href=\"#{}\">{}</a></li>", sec.id(), sec.name());
+    }
+
+    if !sidebar.is_empty() {
+        write!(
+            buf,
+            "<section>\
+                 <div class=\"block\">\
+                     <ul>{}</ul>\
+                 </div>\
+             </section>",
+            sidebar
+        );
+    }
+}
+
+fn sidebar_foreign_type(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item) {
+    let mut sidebar = Buffer::new();
+    sidebar_assoc_items(cx, &mut sidebar, it);
+
+    if !sidebar.is_empty() {
+        write!(buf, "<section>{}</section>", sidebar.into_inner());
+    }
+}
+
+pub(crate) const BASIC_KEYWORDS: &str = "rust, rustlang, rust-lang";
+
+/// Returns a list of all paths used in the type.
+/// This is used to help deduplicate imported impls
+/// for reexported types. If any of the contained
+/// types are re-exported, we don't use the corresponding
+/// entry from the js file, as inlining will have already
+/// picked up the impl
+fn collect_paths_for_type(first_ty: clean::Type, cache: &Cache) -> Vec<String> {
+    let mut out = Vec::new();
+    let mut visited = FxHashSet::default();
+    let mut work = VecDeque::new();
+
+    let mut process_path = |did: DefId| {
+        let get_extern = || cache.external_paths.get(&did).map(|s| s.0.clone());
+        let fqp = cache.exact_paths.get(&did).cloned().or_else(get_extern);
+
+        if let Some(path) = fqp {
+            out.push(join_with_double_colon(&path));
+        }
+    };
+
+    work.push_back(first_ty);
+
+    while let Some(ty) = work.pop_front() {
+        if !visited.insert(ty.clone()) {
+            continue;
+        }
+
+        match ty {
+            clean::Type::Path { path } => process_path(path.def_id()),
+            clean::Type::Tuple(tys) => {
+                work.extend(tys.into_iter());
+            }
+            clean::Type::Slice(ty) => {
+                work.push_back(*ty);
+            }
+            clean::Type::Array(ty, _) => {
+                work.push_back(*ty);
+            }
+            clean::Type::RawPointer(_, ty) => {
+                work.push_back(*ty);
+            }
+            clean::Type::BorrowedRef { type_, .. } => {
+                work.push_back(*type_);
+            }
+            clean::Type::QPath { self_type, trait_, .. } => {
+                work.push_back(*self_type);
+                process_path(trait_.def_id());
+            }
+            _ => {}
+        }
+    }
+    out
+}
+
+const MAX_FULL_EXAMPLES: usize = 5;
+const NUM_VISIBLE_LINES: usize = 10;
+
+/// Generates the HTML for example call locations generated via the --scrape-examples flag.
+fn render_call_locations(w: &mut Buffer, cx: &mut Context<'_>, item: &clean::Item) {
+    let tcx = cx.tcx();
+    let def_id = item.item_id.expect_def_id();
+    let key = tcx.def_path_hash(def_id);
+    let Some(call_locations) = cx.shared.call_locations.get(&key) else { return };
+
+    // Generate a unique ID so users can link to this section for a given method
+    let id = cx.id_map.derive("scraped-examples");
+    write!(
+        w,
+        "<div class=\"docblock scraped-example-list\">\
+          <span></span>\
+          <h5 id=\"{id}\">\
+             <a href=\"#{id}\">Examples found in repository</a>\
+             <a class=\"scrape-help\" href=\"{root_path}scrape-examples-help.html\">?</a>\
+          </h5>",
+        root_path = cx.root_path(),
+        id = id
+    );
+
+    // Create a URL to a particular location in a reverse-dependency's source file
+    let link_to_loc = |call_data: &CallData, loc: &CallLocation| -> (String, String) {
+        let (line_lo, line_hi) = loc.call_expr.line_span;
+        let (anchor, title) = if line_lo == line_hi {
+            ((line_lo + 1).to_string(), format!("line {}", line_lo + 1))
+        } else {
+            (
+                format!("{}-{}", line_lo + 1, line_hi + 1),
+                format!("lines {}-{}", line_lo + 1, line_hi + 1),
+            )
+        };
+        let url = format!("{}{}#{}", cx.root_path(), call_data.url, anchor);
+        (url, title)
+    };
+
+    // Generate the HTML for a single example, being the title and code block
+    let write_example = |w: &mut Buffer, (path, call_data): (&PathBuf, &CallData)| -> bool {
+        let contents = match fs::read_to_string(&path) {
+            Ok(contents) => contents,
+            Err(err) => {
+                let span = item.span(tcx).inner();
+                tcx.sess
+                    .span_err(span, &format!("failed to read file {}: {}", path.display(), err));
+                return false;
+            }
+        };
+
+        // To reduce file sizes, we only want to embed the source code needed to understand the example, not
+        // the entire file. So we find the smallest byte range that covers all items enclosing examples.
+        assert!(!call_data.locations.is_empty());
+        let min_loc =
+            call_data.locations.iter().min_by_key(|loc| loc.enclosing_item.byte_span.0).unwrap();
+        let byte_min = min_loc.enclosing_item.byte_span.0;
+        let line_min = min_loc.enclosing_item.line_span.0;
+        let max_loc =
+            call_data.locations.iter().max_by_key(|loc| loc.enclosing_item.byte_span.1).unwrap();
+        let byte_max = max_loc.enclosing_item.byte_span.1;
+        let line_max = max_loc.enclosing_item.line_span.1;
+
+        // The output code is limited to that byte range.
+        let contents_subset = &contents[(byte_min as usize)..(byte_max as usize)];
+
+        // The call locations need to be updated to reflect that the size of the program has changed.
+        // Specifically, the ranges are all subtracted by `byte_min` since that's the new zero point.
+        let (mut byte_ranges, line_ranges): (Vec<_>, Vec<_>) = call_data
+            .locations
+            .iter()
+            .map(|loc| {
+                let (byte_lo, byte_hi) = loc.call_ident.byte_span;
+                let (line_lo, line_hi) = loc.call_expr.line_span;
+                let byte_range = (byte_lo - byte_min, byte_hi - byte_min);
+
+                let line_range = (line_lo - line_min, line_hi - line_min);
+                let (line_url, line_title) = link_to_loc(call_data, loc);
+
+                (byte_range, (line_range, line_url, line_title))
+            })
+            .unzip();
+
+        let (_, init_url, init_title) = &line_ranges[0];
+        let needs_expansion = line_max - line_min > NUM_VISIBLE_LINES;
+        let locations_encoded = serde_json::to_string(&line_ranges).unwrap();
+
+        write!(
+            w,
+            "<div class=\"scraped-example {expanded_cls}\" data-locs=\"{locations}\">\
+                <div class=\"scraped-example-title\">\
+                   {name} (<a href=\"{url}\">{title}</a>)\
+                </div>\
+                <div class=\"code-wrapper\">",
+            expanded_cls = if needs_expansion { "" } else { "expanded" },
+            name = call_data.display_name,
+            url = init_url,
+            title = init_title,
+            // The locations are encoded as a data attribute, so they can be read
+            // later by the JS for interactions.
+            locations = Escape(&locations_encoded)
+        );
+
+        if line_ranges.len() > 1 {
+            write!(w, r#"<span class="prev">&pr;</span> <span class="next">&sc;</span>"#);
+        }
+
+        if needs_expansion {
+            write!(w, r#"<span class="expand">&varr;</span>"#);
+        }
+
+        // Look for the example file in the source map if it exists, otherwise return a dummy span
+        let file_span = (|| {
+            let source_map = tcx.sess.source_map();
+            let crate_src = tcx.sess.local_crate_source_file.as_ref()?;
+            let abs_crate_src = crate_src.canonicalize().ok()?;
+            let crate_root = abs_crate_src.parent()?.parent()?;
+            let rel_path = path.strip_prefix(crate_root).ok()?;
+            let files = source_map.files();
+            let file = files.iter().find(|file| match &file.name {
+                FileName::Real(RealFileName::LocalPath(other_path)) => rel_path == other_path,
+                _ => false,
+            })?;
+            Some(rustc_span::Span::with_root_ctxt(
+                file.start_pos + BytePos(byte_min),
+                file.start_pos + BytePos(byte_max),
+            ))
+        })()
+        .unwrap_or(rustc_span::DUMMY_SP);
+
+        // The root path is the inverse of Context::current
+        let root_path = vec!["../"; cx.current.len() - 1].join("");
+
+        let mut decoration_info = FxHashMap::default();
+        decoration_info.insert("highlight focus", vec![byte_ranges.remove(0)]);
+        decoration_info.insert("highlight", byte_ranges);
+
+        sources::print_src(
+            w,
+            contents_subset,
+            call_data.edition,
+            file_span,
+            cx,
+            &root_path,
+            Some(highlight::DecorationInfo(decoration_info)),
+            sources::SourceContext::Embedded { offset: line_min },
+        );
+        write!(w, "</div></div>");
+
+        true
+    };
+
+    // The call locations are output in sequence, so that sequence needs to be determined.
+    // Ideally the most "relevant" examples would be shown first, but there's no general algorithm
+    // for determining relevance. Instead, we prefer the smallest examples being likely the easiest to
+    // understand at a glance.
+    let ordered_locations = {
+        let sort_criterion = |(_, call_data): &(_, &CallData)| {
+            // Use the first location because that's what the user will see initially
+            let (lo, hi) = call_data.locations[0].enclosing_item.byte_span;
+            hi - lo
+        };
+
+        let mut locs = call_locations.iter().collect::<Vec<_>>();
+        locs.sort_by_key(sort_criterion);
+        locs
+    };
+
+    let mut it = ordered_locations.into_iter().peekable();
+
+    // An example may fail to write if its source can't be read for some reason, so this method
+    // continues iterating until a write succeeds
+    let write_and_skip_failure = |w: &mut Buffer, it: &mut Peekable<_>| {
+        while let Some(example) = it.next() {
+            if write_example(&mut *w, example) {
+                break;
+            }
+        }
+    };
+
+    // Write just one example that's visible by default in the method's description.
+    write_and_skip_failure(w, &mut it);
+
+    // Then add the remaining examples in a hidden section.
+    if it.peek().is_some() {
+        write!(
+            w,
+            "<details class=\"rustdoc-toggle more-examples-toggle\">\
+                  <summary class=\"hideme\">\
+                     <span>More examples</span>\
+                  </summary>\
+                  <div class=\"hide-more\">Hide additional examples</div>\
+                  <div class=\"more-scraped-examples\">\
+                    <div class=\"toggle-line\"><div class=\"toggle-line-inner\"></div></div>\
+                    <div class=\"more-scraped-examples-inner\">"
+        );
+
+        // Only generate inline code for MAX_FULL_EXAMPLES number of examples. Otherwise we could
+        // make the page arbitrarily huge!
+        for _ in 0..MAX_FULL_EXAMPLES {
+            write_and_skip_failure(w, &mut it);
+        }
+
+        // For the remaining examples, generate a <ul> containing links to the source files.
+        if it.peek().is_some() {
+            write!(w, r#"<div class="example-links">Additional examples can be found in:<br><ul>"#);
+            it.for_each(|(_, call_data)| {
+                let (url, _) = link_to_loc(call_data, &call_data.locations[0]);
+                write!(
+                    w,
+                    r#"<li><a href="{url}">{name}</a></li>"#,
+                    url = url,
+                    name = call_data.display_name
+                );
+            });
+            write!(w, "</ul></div>");
+        }
+
+        write!(w, "</div></div></details>");
+    }
+
+    write!(w, "</div>");
+}
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
new file mode 100644
index 000000000..99cf42919
--- /dev/null
+++ b/src/librustdoc/html/render/print_item.rs
@@ -0,0 +1,1974 @@
+use clean::AttributesExt;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir as hir;
+use rustc_hir::def::CtorKind;
+use rustc_hir::def_id::DefId;
+use rustc_middle::middle::stability;
+use rustc_middle::span_bug;
+use rustc_middle::ty::layout::LayoutError;
+use rustc_middle::ty::{Adt, TyCtxt};
+use rustc_span::hygiene::MacroKind;
+use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_target::abi::{Layout, Primitive, TagEncoding, Variants};
+use std::cmp::Ordering;
+use std::fmt;
+use std::rc::Rc;
+
+use super::{
+    collect_paths_for_type, document, ensure_trailing_slash, item_ty_to_section,
+    notable_traits_decl, render_assoc_item, render_assoc_items, render_attributes_in_code,
+    render_attributes_in_pre, render_impl, render_stability_since_raw, write_srclink,
+    AssocItemLink, Context, ImplRenderingParameters,
+};
+use crate::clean;
+use crate::config::ModuleSorting;
+use crate::formats::item_type::ItemType;
+use crate::formats::{AssocItemRender, Impl, RenderMode};
+use crate::html::escape::Escape;
+use crate::html::format::{
+    join_with_double_colon, print_abi_with_space, print_constness_with_space, print_where_clause,
+    Buffer, Ending, PrintWithSpace,
+};
+use crate::html::highlight;
+use crate::html::layout::Page;
+use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
+use crate::html::url_parts_builder::UrlPartsBuilder;
+
+use askama::Template;
+use itertools::Itertools;
+
+const ITEM_TABLE_OPEN: &str = "<div class=\"item-table\">";
+const ITEM_TABLE_CLOSE: &str = "</div>";
+const ITEM_TABLE_ROW_OPEN: &str = "<div class=\"item-row\">";
+const ITEM_TABLE_ROW_CLOSE: &str = "</div>";
+
+// A component in a `use` path, like `string` in std::string::ToString
+struct PathComponent {
+    path: String,
+    name: Symbol,
+}
+
+#[derive(Template)]
+#[template(path = "print_item.html")]
+struct ItemVars<'a> {
+    page: &'a Page<'a>,
+    static_root_path: &'a str,
+    typ: &'a str,
+    name: &'a str,
+    item_type: &'a str,
+    path_components: Vec<PathComponent>,
+    stability_since_raw: &'a str,
+    src_href: Option<&'a str>,
+}
+
+/// Calls `print_where_clause` and returns `true` if a `where` clause was generated.
+fn print_where_clause_and_check<'a, 'tcx: 'a>(
+    buffer: &mut Buffer,
+    gens: &'a clean::Generics,
+    cx: &'a Context<'tcx>,
+) -> bool {
+    let len_before = buffer.len();
+    write!(buffer, "{}", print_where_clause(gens, cx, 0, Ending::Newline));
+    len_before != buffer.len()
+}
+
+pub(super) fn print_item(
+    cx: &mut Context<'_>,
+    item: &clean::Item,
+    buf: &mut Buffer,
+    page: &Page<'_>,
+) {
+    debug_assert!(!item.is_stripped());
+    let typ = match *item.kind {
+        clean::ModuleItem(_) => {
+            if item.is_crate() {
+                "Crate "
+            } else {
+                "Module "
+            }
+        }
+        clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => "Function ",
+        clean::TraitItem(..) => "Trait ",
+        clean::StructItem(..) => "Struct ",
+        clean::UnionItem(..) => "Union ",
+        clean::EnumItem(..) => "Enum ",
+        clean::TypedefItem(..) => "Type Definition ",
+        clean::MacroItem(..) => "Macro ",
+        clean::ProcMacroItem(ref mac) => match mac.kind {
+            MacroKind::Bang => "Macro ",
+            MacroKind::Attr => "Attribute Macro ",
+            MacroKind::Derive => "Derive Macro ",
+        },
+        clean::PrimitiveItem(..) => "Primitive Type ",
+        clean::StaticItem(..) | clean::ForeignStaticItem(..) => "Static ",
+        clean::ConstantItem(..) => "Constant ",
+        clean::ForeignTypeItem => "Foreign Type ",
+        clean::KeywordItem => "Keyword ",
+        clean::OpaqueTyItem(..) => "Opaque Type ",
+        clean::TraitAliasItem(..) => "Trait Alias ",
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
+        }
+    };
+    let mut stability_since_raw = Buffer::new();
+    render_stability_since_raw(
+        &mut stability_since_raw,
+        item.stable_since(cx.tcx()),
+        item.const_stability(cx.tcx()),
+        None,
+        None,
+    );
+    let stability_since_raw: String = stability_since_raw.into_inner();
+
+    // Write source tag
+    //
+    // When this item is part of a `crate use` in a downstream crate, the
+    // source link in the downstream documentation will actually come back to
+    // this page, and this link will be auto-clicked. The `id` attribute is
+    // used to find the link to auto-click.
+    let src_href =
+        if cx.include_sources && !item.is_primitive() { cx.src_href(item) } else { None };
+
+    let path_components = if item.is_primitive() || item.is_keyword() {
+        vec![]
+    } else {
+        let cur = &cx.current;
+        let amt = if item.is_mod() { cur.len() - 1 } else { cur.len() };
+        cur.iter()
+            .enumerate()
+            .take(amt)
+            .map(|(i, component)| PathComponent {
+                path: "../".repeat(cur.len() - i - 1),
+                name: *component,
+            })
+            .collect()
+    };
+
+    let item_vars = ItemVars {
+        page,
+        static_root_path: page.get_static_root_path(),
+        typ,
+        name: item.name.as_ref().unwrap().as_str(),
+        item_type: &item.type_().to_string(),
+        path_components,
+        stability_since_raw: &stability_since_raw,
+        src_href: src_href.as_deref(),
+    };
+
+    item_vars.render_into(buf).unwrap();
+
+    match &*item.kind {
+        clean::ModuleItem(ref m) => item_module(buf, cx, item, &m.items),
+        clean::FunctionItem(ref f) | clean::ForeignFunctionItem(ref f) => {
+            item_function(buf, cx, item, f)
+        }
+        clean::TraitItem(ref t) => item_trait(buf, cx, item, t),
+        clean::StructItem(ref s) => item_struct(buf, cx, item, s),
+        clean::UnionItem(ref s) => item_union(buf, cx, item, s),
+        clean::EnumItem(ref e) => item_enum(buf, cx, item, e),
+        clean::TypedefItem(ref t) => item_typedef(buf, cx, item, t),
+        clean::MacroItem(ref m) => item_macro(buf, cx, item, m),
+        clean::ProcMacroItem(ref m) => item_proc_macro(buf, cx, item, m),
+        clean::PrimitiveItem(_) => item_primitive(buf, cx, item),
+        clean::StaticItem(ref i) | clean::ForeignStaticItem(ref i) => item_static(buf, cx, item, i),
+        clean::ConstantItem(ref c) => item_constant(buf, cx, item, c),
+        clean::ForeignTypeItem => item_foreign_type(buf, cx, item),
+        clean::KeywordItem => item_keyword(buf, cx, item),
+        clean::OpaqueTyItem(ref e) => item_opaque_ty(buf, cx, item, e),
+        clean::TraitAliasItem(ref ta) => item_trait_alias(buf, cx, item, ta),
+        _ => {
+            // We don't generate pages for any other type.
+            unreachable!();
+        }
+    }
+}
+
+/// For large structs, enums, unions, etc, determine whether to hide their fields
+fn should_hide_fields(n_fields: usize) -> bool {
+    n_fields > 12
+}
+
+fn toggle_open(w: &mut Buffer, text: impl fmt::Display) {
+    write!(
+        w,
+        "<details class=\"rustdoc-toggle type-contents-toggle\">\
+            <summary class=\"hideme\">\
+                <span>Show {}</span>\
+            </summary>",
+        text
+    );
+}
+
+fn toggle_close(w: &mut Buffer) {
+    w.write_str("</details>");
+}
+
+fn item_module(w: &mut Buffer, cx: &mut Context<'_>, item: &clean::Item, items: &[clean::Item]) {
+    document(w, cx, item, None, HeadingOffset::H2);
+
+    let mut indices = (0..items.len()).filter(|i| !items[*i].is_stripped()).collect::<Vec<usize>>();
+
+    // the order of item types in the listing
+    fn reorder(ty: ItemType) -> u8 {
+        match ty {
+            ItemType::ExternCrate => 0,
+            ItemType::Import => 1,
+            ItemType::Primitive => 2,
+            ItemType::Module => 3,
+            ItemType::Macro => 4,
+            ItemType::Struct => 5,
+            ItemType::Enum => 6,
+            ItemType::Constant => 7,
+            ItemType::Static => 8,
+            ItemType::Trait => 9,
+            ItemType::Function => 10,
+            ItemType::Typedef => 12,
+            ItemType::Union => 13,
+            _ => 14 + ty as u8,
+        }
+    }
+
+    fn cmp(
+        i1: &clean::Item,
+        i2: &clean::Item,
+        idx1: usize,
+        idx2: usize,
+        tcx: TyCtxt<'_>,
+    ) -> Ordering {
+        let ty1 = i1.type_();
+        let ty2 = i2.type_();
+        if item_ty_to_section(ty1) != item_ty_to_section(ty2)
+            || (ty1 != ty2 && (ty1 == ItemType::ExternCrate || ty2 == ItemType::ExternCrate))
+        {
+            return (reorder(ty1), idx1).cmp(&(reorder(ty2), idx2));
+        }
+        let s1 = i1.stability(tcx).as_ref().map(|s| s.level);
+        let s2 = i2.stability(tcx).as_ref().map(|s| s.level);
+        if let (Some(a), Some(b)) = (s1, s2) {
+            match (a.is_stable(), b.is_stable()) {
+                (true, true) | (false, false) => {}
+                (false, true) => return Ordering::Less,
+                (true, false) => return Ordering::Greater,
+            }
+        }
+        let lhs = i1.name.unwrap_or(kw::Empty);
+        let rhs = i2.name.unwrap_or(kw::Empty);
+        compare_names(lhs.as_str(), rhs.as_str())
+    }
+
+    match cx.shared.module_sorting {
+        ModuleSorting::Alphabetical => {
+            indices.sort_by(|&i1, &i2| cmp(&items[i1], &items[i2], i1, i2, cx.tcx()));
+        }
+        ModuleSorting::DeclarationOrder => {}
+    }
+    // This call is to remove re-export duplicates in cases such as:
+    //
+    // ```
+    // pub(crate) mod foo {
+    //     pub(crate) mod bar {
+    //         pub(crate) trait Double { fn foo(); }
+    //     }
+    // }
+    //
+    // pub(crate) use foo::bar::*;
+    // pub(crate) use foo::*;
+    // ```
+    //
+    // `Double` will appear twice in the generated docs.
+    //
+    // FIXME: This code is quite ugly and could be improved. Small issue: DefId
+    // can be identical even if the elements are different (mostly in imports).
+    // So in case this is an import, we keep everything by adding a "unique id"
+    // (which is the position in the vector).
+    indices.dedup_by_key(|i| {
+        (
+            items[*i].item_id,
+            if items[*i].name.is_some() { Some(full_path(cx, &items[*i])) } else { None },
+            items[*i].type_(),
+            if items[*i].is_import() { *i } else { 0 },
+        )
+    });
+
+    debug!("{:?}", indices);
+    let mut last_section = None;
+
+    for &idx in &indices {
+        let myitem = &items[idx];
+        if myitem.is_stripped() {
+            continue;
+        }
+
+        let my_section = item_ty_to_section(myitem.type_());
+        if Some(my_section) != last_section {
+            if last_section.is_some() {
+                w.write_str(ITEM_TABLE_CLOSE);
+            }
+            last_section = Some(my_section);
+            write!(
+                w,
+                "<h2 id=\"{id}\" class=\"small-section-header\">\
+                    <a href=\"#{id}\">{name}</a>\
+                 </h2>{}",
+                ITEM_TABLE_OPEN,
+                id = cx.derive_id(my_section.id().to_owned()),
+                name = my_section.name(),
+            );
+        }
+
+        match *myitem.kind {
+            clean::ExternCrateItem { ref src } => {
+                use crate::html::format::anchor;
+
+                w.write_str(ITEM_TABLE_ROW_OPEN);
+                match *src {
+                    Some(src) => write!(
+                        w,
+                        "<div class=\"item-left\"><code>{}extern crate {} as {};",
+                        myitem.visibility.print_with_space(myitem.item_id, cx),
+                        anchor(myitem.item_id.expect_def_id(), src, cx),
+                        myitem.name.unwrap(),
+                    ),
+                    None => write!(
+                        w,
+                        "<div class=\"item-left\"><code>{}extern crate {};",
+                        myitem.visibility.print_with_space(myitem.item_id, cx),
+                        anchor(myitem.item_id.expect_def_id(), myitem.name.unwrap(), cx),
+                    ),
+                }
+                w.write_str("</code></div>");
+                w.write_str(ITEM_TABLE_ROW_CLOSE);
+            }
+
+            clean::ImportItem(ref import) => {
+                let (stab, stab_tags) = if let Some(import_def_id) = import.source.did {
+                    let ast_attrs = cx.tcx().get_attrs_unchecked(import_def_id);
+                    let import_attrs = Box::new(clean::Attributes::from_ast(ast_attrs));
+
+                    // Just need an item with the correct def_id and attrs
+                    let import_item = clean::Item {
+                        item_id: import_def_id.into(),
+                        attrs: import_attrs,
+                        cfg: ast_attrs.cfg(cx.tcx(), &cx.cache().hidden_cfg),
+                        ..myitem.clone()
+                    };
+
+                    let stab = import_item.stability_class(cx.tcx());
+                    let stab_tags = Some(extra_info_tags(&import_item, item, cx.tcx()));
+                    (stab, stab_tags)
+                } else {
+                    (None, None)
+                };
+
+                let add = if stab.is_some() { " " } else { "" };
+
+                w.write_str(ITEM_TABLE_ROW_OPEN);
+                let id = match import.kind {
+                    clean::ImportKind::Simple(s) => {
+                        format!(" id=\"{}\"", cx.derive_id(format!("reexport.{}", s)))
+                    }
+                    clean::ImportKind::Glob => String::new(),
+                };
+                write!(
+                    w,
+                    "<div class=\"item-left {stab}{add}import-item\"{id}>\
+                         <code>{vis}{imp}</code>\
+                     </div>\
+                     <div class=\"item-right docblock-short\">{stab_tags}</div>",
+                    stab = stab.unwrap_or_default(),
+                    vis = myitem.visibility.print_with_space(myitem.item_id, cx),
+                    imp = import.print(cx),
+                    stab_tags = stab_tags.unwrap_or_default(),
+                );
+                w.write_str(ITEM_TABLE_ROW_CLOSE);
+            }
+
+            _ => {
+                if myitem.name.is_none() {
+                    continue;
+                }
+
+                let unsafety_flag = match *myitem.kind {
+                    clean::FunctionItem(_) | clean::ForeignFunctionItem(_)
+                        if myitem.fn_header(cx.tcx()).unwrap().unsafety
+                            == hir::Unsafety::Unsafe =>
+                    {
+                        "<a title=\"unsafe function\" href=\"#\"><sup>⚠</sup></a>"
+                    }
+                    _ => "",
+                };
+
+                let stab = myitem.stability_class(cx.tcx());
+                let add = if stab.is_some() { " " } else { "" };
+
+                let visibility_emoji = match myitem.visibility {
+                    clean::Visibility::Restricted(_) => {
+                        "<span title=\"Restricted Visibility\">&nbsp;🔒</span> "
+                    }
+                    _ => "",
+                };
+
+                let doc_value = myitem.doc_value().unwrap_or_default();
+                w.write_str(ITEM_TABLE_ROW_OPEN);
+                write!(
+                    w,
+                    "<div class=\"item-left {stab}{add}module-item\">\
+                        <a class=\"{class}\" href=\"{href}\" title=\"{title}\">{name}</a>\
+                        {visibility_emoji}\
+                        {unsafety_flag}\
+                        {stab_tags}\
+                     </div>\
+                     <div class=\"item-right docblock-short\">{docs}</div>",
+                    name = myitem.name.unwrap(),
+                    visibility_emoji = visibility_emoji,
+                    stab_tags = extra_info_tags(myitem, item, cx.tcx()),
+                    docs = MarkdownSummaryLine(&doc_value, &myitem.links(cx)).into_string(),
+                    class = myitem.type_(),
+                    add = add,
+                    stab = stab.unwrap_or_default(),
+                    unsafety_flag = unsafety_flag,
+                    href = item_path(myitem.type_(), myitem.name.unwrap().as_str()),
+                    title = [full_path(cx, myitem), myitem.type_().to_string()]
+                        .iter()
+                        .filter_map(|s| if !s.is_empty() { Some(s.as_str()) } else { None })
+                        .collect::<Vec<_>>()
+                        .join(" "),
+                );
+                w.write_str(ITEM_TABLE_ROW_CLOSE);
+            }
+        }
+    }
+
+    if last_section.is_some() {
+        w.write_str(ITEM_TABLE_CLOSE);
+    }
+}
+
+/// Render the stability, deprecation and portability tags that are displayed in the item's summary
+/// at the module level.
+fn extra_info_tags(item: &clean::Item, parent: &clean::Item, tcx: TyCtxt<'_>) -> String {
+    let mut tags = String::new();
+
+    fn tag_html(class: &str, title: &str, contents: &str) -> String {
+        format!(r#"<span class="stab {}" title="{}">{}</span>"#, class, Escape(title), contents)
+    }
+
+    // The trailing space after each tag is to space it properly against the rest of the docs.
+    if let Some(depr) = &item.deprecation(tcx) {
+        let mut message = "Deprecated";
+        if !stability::deprecation_in_effect(depr) {
+            message = "Deprecation planned";
+        }
+        tags += &tag_html("deprecated", "", message);
+    }
+
+    // The "rustc_private" crates are permanently unstable so it makes no sense
+    // to render "unstable" everywhere.
+    if item.stability(tcx).as_ref().map(|s| s.is_unstable() && s.feature != sym::rustc_private)
+        == Some(true)
+    {
+        tags += &tag_html("unstable", "", "Experimental");
+    }
+
+    let cfg = match (&item.cfg, parent.cfg.as_ref()) {
+        (Some(cfg), Some(parent_cfg)) => cfg.simplify_with(parent_cfg),
+        (cfg, _) => cfg.as_deref().cloned(),
+    };
+
+    debug!("Portability {:?} - {:?} = {:?}", item.cfg, parent.cfg, cfg);
+    if let Some(ref cfg) = cfg {
+        tags += &tag_html("portability", &cfg.render_long_plain(), &cfg.render_short_html());
+    }
+
+    tags
+}
+
+fn item_function(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, f: &clean::Function) {
+    let header = it.fn_header(cx.tcx()).expect("printing a function which isn't a function");
+    let constness = print_constness_with_space(&header.constness, it.const_stability(cx.tcx()));
+    let unsafety = header.unsafety.print_with_space();
+    let abi = print_abi_with_space(header.abi).to_string();
+    let asyncness = header.asyncness.print_with_space();
+    let visibility = it.visibility.print_with_space(it.item_id, cx).to_string();
+    let name = it.name.unwrap();
+
+    let generics_len = format!("{:#}", f.generics.print(cx)).len();
+    let header_len = "fn ".len()
+        + visibility.len()
+        + constness.len()
+        + asyncness.len()
+        + unsafety.len()
+        + abi.len()
+        + name.as_str().len()
+        + generics_len;
+
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "fn", |w| {
+            render_attributes_in_pre(w, it, "");
+            w.reserve(header_len);
+            write!(
+                w,
+                "{vis}{constness}{asyncness}{unsafety}{abi}fn \
+                 {name}{generics}{decl}{notable_traits}{where_clause}",
+                vis = visibility,
+                constness = constness,
+                asyncness = asyncness,
+                unsafety = unsafety,
+                abi = abi,
+                name = name,
+                generics = f.generics.print(cx),
+                where_clause = print_where_clause(&f.generics, cx, 0, Ending::Newline),
+                decl = f.decl.full_print(header_len, 0, header.asyncness, cx),
+                notable_traits = notable_traits_decl(&f.decl, cx),
+            );
+        });
+    });
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+fn item_trait(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Trait) {
+    let bounds = bounds(&t.bounds, false, cx);
+    let required_types = t.items.iter().filter(|m| m.is_ty_associated_type()).collect::<Vec<_>>();
+    let provided_types = t.items.iter().filter(|m| m.is_associated_type()).collect::<Vec<_>>();
+    let required_consts = t.items.iter().filter(|m| m.is_ty_associated_const()).collect::<Vec<_>>();
+    let provided_consts = t.items.iter().filter(|m| m.is_associated_const()).collect::<Vec<_>>();
+    let required_methods = t.items.iter().filter(|m| m.is_ty_method()).collect::<Vec<_>>();
+    let provided_methods = t.items.iter().filter(|m| m.is_method()).collect::<Vec<_>>();
+    let count_types = required_types.len() + provided_types.len();
+    let count_consts = required_consts.len() + provided_consts.len();
+    let count_methods = required_methods.len() + provided_methods.len();
+    let must_implement_one_of_functions =
+        cx.tcx().trait_def(t.def_id).must_implement_one_of.clone();
+
+    // Output the trait definition
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "trait", |w| {
+            render_attributes_in_pre(w, it, "");
+            write!(
+                w,
+                "{}{}{}trait {}{}{}",
+                it.visibility.print_with_space(it.item_id, cx),
+                t.unsafety(cx.tcx()).print_with_space(),
+                if t.is_auto(cx.tcx()) { "auto " } else { "" },
+                it.name.unwrap(),
+                t.generics.print(cx),
+                bounds
+            );
+
+            if !t.generics.where_predicates.is_empty() {
+                write!(w, "{}", print_where_clause(&t.generics, cx, 0, Ending::Newline));
+            } else {
+                w.write_str(" ");
+            }
+
+            if t.items.is_empty() {
+                w.write_str("{ }");
+            } else {
+                // FIXME: we should be using a derived_id for the Anchors here
+                w.write_str("{\n");
+                let mut toggle = false;
+
+                // If there are too many associated types, hide _everything_
+                if should_hide_fields(count_types) {
+                    toggle = true;
+                    toggle_open(
+                        w,
+                        format_args!(
+                            "{} associated items",
+                            count_types + count_consts + count_methods
+                        ),
+                    );
+                }
+                for types in [&required_types, &provided_types] {
+                    for t in types {
+                        render_assoc_item(
+                            w,
+                            t,
+                            AssocItemLink::Anchor(None),
+                            ItemType::Trait,
+                            cx,
+                            RenderMode::Normal,
+                        );
+                        w.write_str(";\n");
+                    }
+                }
+                // If there are too many associated constants, hide everything after them
+                // We also do this if the types + consts is large because otherwise we could
+                // render a bunch of types and _then_ a bunch of consts just because both were
+                // _just_ under the limit
+                if !toggle && should_hide_fields(count_types + count_consts) {
+                    toggle = true;
+                    toggle_open(
+                        w,
+                        format_args!(
+                            "{} associated constant{} and {} method{}",
+                            count_consts,
+                            pluralize(count_consts),
+                            count_methods,
+                            pluralize(count_methods),
+                        ),
+                    );
+                }
+                if count_types != 0 && (count_consts != 0 || count_methods != 0) {
+                    w.write_str("\n");
+                }
+                for consts in [&required_consts, &provided_consts] {
+                    for c in consts {
+                        render_assoc_item(
+                            w,
+                            c,
+                            AssocItemLink::Anchor(None),
+                            ItemType::Trait,
+                            cx,
+                            RenderMode::Normal,
+                        );
+                        w.write_str(";\n");
+                    }
+                }
+                if !toggle && should_hide_fields(count_methods) {
+                    toggle = true;
+                    toggle_open(w, format_args!("{} methods", count_methods));
+                }
+                if count_consts != 0 && count_methods != 0 {
+                    w.write_str("\n");
+                }
+                for (pos, m) in required_methods.iter().enumerate() {
+                    render_assoc_item(
+                        w,
+                        m,
+                        AssocItemLink::Anchor(None),
+                        ItemType::Trait,
+                        cx,
+                        RenderMode::Normal,
+                    );
+                    w.write_str(";\n");
+
+                    if pos < required_methods.len() - 1 {
+                        w.write_str("<span class=\"item-spacer\"></span>");
+                    }
+                }
+                if !required_methods.is_empty() && !provided_methods.is_empty() {
+                    w.write_str("\n");
+                }
+                for (pos, m) in provided_methods.iter().enumerate() {
+                    render_assoc_item(
+                        w,
+                        m,
+                        AssocItemLink::Anchor(None),
+                        ItemType::Trait,
+                        cx,
+                        RenderMode::Normal,
+                    );
+                    match *m.kind {
+                        clean::MethodItem(ref inner, _)
+                            if !inner.generics.where_predicates.is_empty() =>
+                        {
+                            w.write_str(",\n    { ... }\n");
+                        }
+                        _ => {
+                            w.write_str(" { ... }\n");
+                        }
+                    }
+
+                    if pos < provided_methods.len() - 1 {
+                        w.write_str("<span class=\"item-spacer\"></span>");
+                    }
+                }
+                if toggle {
+                    toggle_close(w);
+                }
+                w.write_str("}");
+            }
+        });
+    });
+
+    // Trait documentation
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    fn write_small_section_header(w: &mut Buffer, id: &str, title: &str, extra_content: &str) {
+        write!(
+            w,
+            "<h2 id=\"{0}\" class=\"small-section-header\">\
+                {1}<a href=\"#{0}\" class=\"anchor\"></a>\
+             </h2>{2}",
+            id, title, extra_content
+        )
+    }
+
+    fn trait_item(w: &mut Buffer, cx: &mut Context<'_>, m: &clean::Item, t: &clean::Item) {
+        let name = m.name.unwrap();
+        info!("Documenting {} on {:?}", name, t.name);
+        let item_type = m.type_();
+        let id = cx.derive_id(format!("{}.{}", item_type, name));
+        let mut content = Buffer::empty_from(w);
+        document(&mut content, cx, m, Some(t), HeadingOffset::H5);
+        let toggled = !content.is_empty();
+        if toggled {
+            write!(w, "<details class=\"rustdoc-toggle\" open><summary>");
+        }
+        write!(w, "<div id=\"{}\" class=\"method has-srclink\">", id);
+        write!(w, "<div class=\"rightside\">");
+
+        let has_stability = render_stability_since(w, m, t, cx.tcx());
+        if has_stability {
+            w.write_str(" · ");
+        }
+        write_srclink(cx, m, w);
+        write!(w, "</div>");
+        write!(w, "<h4 class=\"code-header\">");
+        render_assoc_item(
+            w,
+            m,
+            AssocItemLink::Anchor(Some(&id)),
+            ItemType::Impl,
+            cx,
+            RenderMode::Normal,
+        );
+        w.write_str("</h4>");
+        w.write_str("</div>");
+        if toggled {
+            write!(w, "</summary>");
+            w.push_buffer(content);
+            write!(w, "</details>");
+        }
+    }
+
+    if !required_types.is_empty() {
+        write_small_section_header(
+            w,
+            "required-associated-types",
+            "Required Associated Types",
+            "<div class=\"methods\">",
+        );
+        for t in required_types {
+            trait_item(w, cx, t, it);
+        }
+        w.write_str("</div>");
+    }
+    if !provided_types.is_empty() {
+        write_small_section_header(
+            w,
+            "provided-associated-types",
+            "Provided Associated Types",
+            "<div class=\"methods\">",
+        );
+        for t in provided_types {
+            trait_item(w, cx, t, it);
+        }
+        w.write_str("</div>");
+    }
+
+    if !required_consts.is_empty() {
+        write_small_section_header(
+            w,
+            "required-associated-consts",
+            "Required Associated Constants",
+            "<div class=\"methods\">",
+        );
+        for t in required_consts {
+            trait_item(w, cx, t, it);
+        }
+        w.write_str("</div>");
+    }
+    if !provided_consts.is_empty() {
+        write_small_section_header(
+            w,
+            "provided-associated-consts",
+            "Provided Associated Constants",
+            "<div class=\"methods\">",
+        );
+        for t in provided_consts {
+            trait_item(w, cx, t, it);
+        }
+        w.write_str("</div>");
+    }
+
+    // Output the documentation for each function individually
+    if !required_methods.is_empty() || must_implement_one_of_functions.is_some() {
+        write_small_section_header(
+            w,
+            "required-methods",
+            "Required Methods",
+            "<div class=\"methods\">",
+        );
+
+        if let Some(list) = must_implement_one_of_functions.as_deref() {
+            write!(
+                w,
+                "<div class=\"stab must_implement\">At least one of the `{}` methods is required.</div>",
+                list.iter().join("`, `")
+            );
+        }
+
+        for m in required_methods {
+            trait_item(w, cx, m, it);
+        }
+        w.write_str("</div>");
+    }
+    if !provided_methods.is_empty() {
+        write_small_section_header(
+            w,
+            "provided-methods",
+            "Provided Methods",
+            "<div class=\"methods\">",
+        );
+        for m in provided_methods {
+            trait_item(w, cx, m, it);
+        }
+        w.write_str("</div>");
+    }
+
+    // If there are methods directly on this trait object, render them here.
+    render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All);
+
+    let cloned_shared = Rc::clone(&cx.shared);
+    let cache = &cloned_shared.cache;
+    let mut extern_crates = FxHashSet::default();
+    if let Some(implementors) = cache.implementors.get(&it.item_id.expect_def_id()) {
+        // The DefId is for the first Type found with that name. The bool is
+        // if any Types with the same name but different DefId have been found.
+        let mut implementor_dups: FxHashMap<Symbol, (DefId, bool)> = FxHashMap::default();
+        for implementor in implementors {
+            if let Some(did) = implementor.inner_impl().for_.without_borrowed_ref().def_id(cache) &&
+                !did.is_local() {
+                extern_crates.insert(did.krate);
+            }
+            match implementor.inner_impl().for_.without_borrowed_ref() {
+                clean::Type::Path { ref path } if !path.is_assoc_ty() => {
+                    let did = path.def_id();
+                    let &mut (prev_did, ref mut has_duplicates) =
+                        implementor_dups.entry(path.last()).or_insert((did, false));
+                    if prev_did != did {
+                        *has_duplicates = true;
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        let (local, foreign) =
+            implementors.iter().partition::<Vec<_>, _>(|i| i.is_on_local_type(cx));
+
+        let (mut synthetic, mut concrete): (Vec<&&Impl>, Vec<&&Impl>) =
+            local.iter().partition(|i| i.inner_impl().kind.is_auto());
+
+        synthetic.sort_by(|a, b| compare_impl(a, b, cx));
+        concrete.sort_by(|a, b| compare_impl(a, b, cx));
+
+        if !foreign.is_empty() {
+            write_small_section_header(w, "foreign-impls", "Implementations on Foreign Types", "");
+
+            for implementor in foreign {
+                let provided_methods = implementor.inner_impl().provided_trait_methods(cx.tcx());
+                let assoc_link =
+                    AssocItemLink::GotoSource(implementor.impl_item.item_id, &provided_methods);
+                render_impl(
+                    w,
+                    cx,
+                    implementor,
+                    it,
+                    assoc_link,
+                    RenderMode::Normal,
+                    None,
+                    &[],
+                    ImplRenderingParameters {
+                        show_def_docs: false,
+                        show_default_items: false,
+                        show_non_assoc_items: true,
+                        toggle_open_by_default: false,
+                    },
+                );
+            }
+        }
+
+        write_small_section_header(
+            w,
+            "implementors",
+            "Implementors",
+            "<div class=\"item-list\" id=\"implementors-list\">",
+        );
+        for implementor in concrete {
+            render_implementor(cx, implementor, it, w, &implementor_dups, &[]);
+        }
+        w.write_str("</div>");
+
+        if t.is_auto(cx.tcx()) {
+            write_small_section_header(
+                w,
+                "synthetic-implementors",
+                "Auto implementors",
+                "<div class=\"item-list\" id=\"synthetic-implementors-list\">",
+            );
+            for implementor in synthetic {
+                render_implementor(
+                    cx,
+                    implementor,
+                    it,
+                    w,
+                    &implementor_dups,
+                    &collect_paths_for_type(implementor.inner_impl().for_.clone(), cache),
+                );
+            }
+            w.write_str("</div>");
+        }
+    } else {
+        // even without any implementations to write in, we still want the heading and list, so the
+        // implementors javascript file pulled in below has somewhere to write the impls into
+        write_small_section_header(
+            w,
+            "implementors",
+            "Implementors",
+            "<div class=\"item-list\" id=\"implementors-list\"></div>",
+        );
+
+        if t.is_auto(cx.tcx()) {
+            write_small_section_header(
+                w,
+                "synthetic-implementors",
+                "Auto implementors",
+                "<div class=\"item-list\" id=\"synthetic-implementors-list\"></div>",
+            );
+        }
+    }
+
+    // Include implementors in crates that depend on the current crate.
+    //
+    // This is complicated by the way rustdoc is invoked, which is basically
+    // the same way rustc is invoked: it gets called, one at a time, for each
+    // crate. When building the rustdocs for the current crate, rustdoc can
+    // see crate metadata for its dependencies, but cannot see metadata for its
+    // dependents.
+    //
+    // To make this work, we generate a "hook" at this stage, and our
+    // dependents can "plug in" to it when they build. For simplicity's sake,
+    // it's [JSONP]: a JavaScript file with the data we need (and can parse),
+    // surrounded by a tiny wrapper that the Rust side ignores, but allows the
+    // JavaScript side to include without having to worry about Same Origin
+    // Policy. The code for *that* is in `write_shared.rs`.
+    //
+    // This is further complicated by `#[doc(inline)]`. We want all copies
+    // of an inlined trait to reference the same JS file, to address complex
+    // dependency graphs like this one (lower crates depend on higher crates):
+    //
+    // ```text
+    //  --------------------------------------------
+    //  |            crate A: trait Foo            |
+    //  --------------------------------------------
+    //      |                               |
+    //  --------------------------------    |
+    //  | crate B: impl A::Foo for Bar |    |
+    //  --------------------------------    |
+    //      |                               |
+    //  ---------------------------------------------
+    //  | crate C: #[doc(inline)] use A::Foo as Baz |
+    //  |          impl Baz for Quux                |
+    //  ---------------------------------------------
+    // ```
+    //
+    // Basically, we want `C::Baz` and `A::Foo` to show the same set of
+    // impls, which is easier if they both treat `/implementors/A/trait.Foo.js`
+    // as the Single Source of Truth.
+    //
+    // We also want the `impl Baz for Quux` to be written to
+    // `trait.Foo.js`. However, when we generate plain HTML for `C::Baz`,
+    // we're going to want to generate plain HTML for `impl Baz for Quux` too,
+    // because that'll load faster, and it's better for SEO. And we don't want
+    // the same impl to show up twice on the same page.
+    //
+    // To make this work, the implementors JS file has a structure kinda
+    // like this:
+    //
+    // ```js
+    // JSONP({
+    // "B": {"impl A::Foo for Bar"},
+    // "C": {"impl Baz for Quux"},
+    // });
+    // ```
+    //
+    // First of all, this means we can rebuild a crate, and it'll replace its own
+    // data if something changes. That is, `rustdoc` is idempotent. The other
+    // advantage is that we can list the crates that get included in the HTML,
+    // and ignore them when doing the JavaScript-based part of rendering.
+    // So C's HTML will have something like this:
+    //
+    // ```html
+    // <script type="text/javascript" src="/implementors/A/trait.Foo.js"
+    //     data-ignore-extern-crates="A,B" async></script>
+    // ```
+    //
+    // And, when the JS runs, anything in data-ignore-extern-crates is known
+    // to already be in the HTML, and will be ignored.
+    //
+    // [JSONP]: https://en.wikipedia.org/wiki/JSONP
+    let mut js_src_path: UrlPartsBuilder = std::iter::repeat("..")
+        .take(cx.current.len())
+        .chain(std::iter::once("implementors"))
+        .collect();
+    if let Some(did) = it.item_id.as_def_id() &&
+        let get_extern = { || cache.external_paths.get(&did).map(|s| s.0.clone()) } &&
+        let Some(fqp) = cache.exact_paths.get(&did).cloned().or_else(get_extern) {
+        js_src_path.extend(fqp[..fqp.len() - 1].iter().copied());
+        js_src_path.push_fmt(format_args!("{}.{}.js", it.type_(), fqp.last().unwrap()));
+    } else {
+        js_src_path.extend(cx.current.iter().copied());
+        js_src_path.push_fmt(format_args!("{}.{}.js", it.type_(), it.name.unwrap()));
+    }
+    let extern_crates = extern_crates
+        .into_iter()
+        .map(|cnum| cx.shared.tcx.crate_name(cnum).to_string())
+        .collect::<Vec<_>>()
+        .join(",");
+    write!(
+        w,
+        "<script type=\"text/javascript\" src=\"{src}\" data-ignore-extern-crates=\"{extern_crates}\" async></script>",
+        src = js_src_path.finish(),
+    );
+}
+
+fn item_trait_alias(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::TraitAlias) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "trait-alias", |w| {
+            render_attributes_in_pre(w, it, "");
+            write!(
+                w,
+                "trait {}{}{} = {};",
+                it.name.unwrap(),
+                t.generics.print(cx),
+                print_where_clause(&t.generics, cx, 0, Ending::Newline),
+                bounds(&t.bounds, true, cx)
+            );
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    // Render any items associated directly to this alias, as otherwise they
+    // won't be visible anywhere in the docs. It would be nice to also show
+    // associated items from the aliased type (see discussion in #32077), but
+    // we need #14072 to make sense of the generics.
+    render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
+}
+
+fn item_opaque_ty(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::OpaqueTy) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "opaque", |w| {
+            render_attributes_in_pre(w, it, "");
+            write!(
+                w,
+                "type {}{}{where_clause} = impl {bounds};",
+                it.name.unwrap(),
+                t.generics.print(cx),
+                where_clause = print_where_clause(&t.generics, cx, 0, Ending::Newline),
+                bounds = bounds(&t.bounds, false, cx),
+            );
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    // Render any items associated directly to this alias, as otherwise they
+    // won't be visible anywhere in the docs. It would be nice to also show
+    // associated items from the aliased type (see discussion in #32077), but
+    // we need #14072 to make sense of the generics.
+    render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
+}
+
+fn item_typedef(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Typedef) {
+    fn write_content(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Typedef) {
+        wrap_item(w, "typedef", |w| {
+            render_attributes_in_pre(w, it, "");
+            write!(w, "{}", it.visibility.print_with_space(it.item_id, cx));
+            write!(
+                w,
+                "type {}{}{where_clause} = {type_};",
+                it.name.unwrap(),
+                t.generics.print(cx),
+                where_clause = print_where_clause(&t.generics, cx, 0, Ending::Newline),
+                type_ = t.type_.print(cx),
+            );
+        });
+    }
+
+    wrap_into_docblock(w, |w| write_content(w, cx, it, t));
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    let def_id = it.item_id.expect_def_id();
+    // Render any items associated directly to this alias, as otherwise they
+    // won't be visible anywhere in the docs. It would be nice to also show
+    // associated items from the aliased type (see discussion in #32077), but
+    // we need #14072 to make sense of the generics.
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_type_layout(w, cx, def_id);
+}
+
+fn item_union(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Union) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "union", |w| {
+            render_attributes_in_pre(w, it, "");
+            render_union(w, it, Some(&s.generics), &s.fields, "", cx);
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    let mut fields = s
+        .fields
+        .iter()
+        .filter_map(|f| match *f.kind {
+            clean::StructFieldItem(ref ty) => Some((f, ty)),
+            _ => None,
+        })
+        .peekable();
+    if fields.peek().is_some() {
+        write!(
+            w,
+            "<h2 id=\"fields\" class=\"fields small-section-header\">\
+                Fields<a href=\"#fields\" class=\"anchor\"></a>\
+            </h2>"
+        );
+        for (field, ty) in fields {
+            let name = field.name.expect("union field name");
+            let id = format!("{}.{}", ItemType::StructField, name);
+            write!(
+                w,
+                "<span id=\"{id}\" class=\"{shortty} small-section-header\">\
+                     <a href=\"#{id}\" class=\"anchor field\"></a>\
+                     <code>{name}: {ty}</code>\
+                 </span>",
+                id = id,
+                name = name,
+                shortty = ItemType::StructField,
+                ty = ty.print(cx),
+            );
+            if let Some(stability_class) = field.stability_class(cx.tcx()) {
+                write!(w, "<span class=\"stab {stab}\"></span>", stab = stability_class);
+            }
+            document(w, cx, field, Some(it), HeadingOffset::H3);
+        }
+    }
+    let def_id = it.item_id.expect_def_id();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_type_layout(w, cx, def_id);
+}
+
+fn print_tuple_struct_fields(w: &mut Buffer, cx: &Context<'_>, s: &[clean::Item]) {
+    for (i, ty) in s.iter().enumerate() {
+        if i > 0 {
+            w.write_str(",&nbsp;");
+        }
+        match *ty.kind {
+            clean::StrippedItem(box clean::StructFieldItem(_)) => w.write_str("_"),
+            clean::StructFieldItem(ref ty) => write!(w, "{}", ty.print(cx)),
+            _ => unreachable!(),
+        }
+    }
+}
+
+fn item_enum(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, e: &clean::Enum) {
+    let count_variants = e.variants().count();
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "enum", |w| {
+            render_attributes_in_pre(w, it, "");
+            write!(
+                w,
+                "{}enum {}{}",
+                it.visibility.print_with_space(it.item_id, cx),
+                it.name.unwrap(),
+                e.generics.print(cx),
+            );
+            if !print_where_clause_and_check(w, &e.generics, cx) {
+                // If there wasn't a `where` clause, we add a whitespace.
+                w.write_str(" ");
+            }
+
+            let variants_stripped = e.has_stripped_entries();
+            if count_variants == 0 && !variants_stripped {
+                w.write_str("{}");
+            } else {
+                w.write_str("{\n");
+                let toggle = should_hide_fields(count_variants);
+                if toggle {
+                    toggle_open(w, format_args!("{} variants", count_variants));
+                }
+                for v in e.variants() {
+                    w.write_str("    ");
+                    let name = v.name.unwrap();
+                    match *v.kind {
+                        clean::VariantItem(ref var) => match var {
+                            clean::Variant::CLike => write!(w, "{}", name),
+                            clean::Variant::Tuple(ref s) => {
+                                write!(w, "{}(", name);
+                                print_tuple_struct_fields(w, cx, s);
+                                w.write_str(")");
+                            }
+                            clean::Variant::Struct(ref s) => {
+                                render_struct(
+                                    w,
+                                    v,
+                                    None,
+                                    s.struct_type,
+                                    &s.fields,
+                                    "    ",
+                                    false,
+                                    cx,
+                                );
+                            }
+                        },
+                        _ => unreachable!(),
+                    }
+                    w.write_str(",\n");
+                }
+
+                if variants_stripped {
+                    w.write_str("    // some variants omitted\n");
+                }
+                if toggle {
+                    toggle_close(w);
+                }
+                w.write_str("}");
+            }
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    if count_variants != 0 {
+        write!(
+            w,
+            "<h2 id=\"variants\" class=\"variants small-section-header\">\
+                Variants{}<a href=\"#variants\" class=\"anchor\"></a>\
+            </h2>",
+            document_non_exhaustive_header(it)
+        );
+        document_non_exhaustive(w, it);
+        for variant in e.variants() {
+            let id = cx.derive_id(format!("{}.{}", ItemType::Variant, variant.name.unwrap()));
+            write!(
+                w,
+                "<h3 id=\"{id}\" class=\"variant small-section-header\">\
+                    <a href=\"#{id}\" class=\"anchor field\"></a>\
+                    <code>{name}",
+                id = id,
+                name = variant.name.unwrap()
+            );
+            if let clean::VariantItem(clean::Variant::Tuple(ref s)) = *variant.kind {
+                w.write_str("(");
+                print_tuple_struct_fields(w, cx, s);
+                w.write_str(")");
+            }
+            w.write_str("</code>");
+            render_stability_since(w, variant, it, cx.tcx());
+            w.write_str("</h3>");
+
+            use crate::clean::Variant;
+
+            let heading_and_fields = match &*variant.kind {
+                clean::VariantItem(Variant::Struct(s)) => Some(("Fields", &s.fields)),
+                // Documentation on tuple variant fields is rare, so to reduce noise we only emit
+                // the section if at least one field is documented.
+                clean::VariantItem(Variant::Tuple(fields))
+                    if fields.iter().any(|f| f.doc_value().is_some()) =>
+                {
+                    Some(("Tuple Fields", fields))
+                }
+                _ => None,
+            };
+
+            if let Some((heading, fields)) = heading_and_fields {
+                let variant_id =
+                    cx.derive_id(format!("{}.{}.fields", ItemType::Variant, variant.name.unwrap()));
+                write!(w, "<div class=\"sub-variant\" id=\"{id}\">", id = variant_id);
+                write!(w, "<h4>{heading}</h4>", heading = heading);
+                document_non_exhaustive(w, variant);
+                for field in fields {
+                    match *field.kind {
+                        clean::StrippedItem(box clean::StructFieldItem(_)) => {}
+                        clean::StructFieldItem(ref ty) => {
+                            let id = cx.derive_id(format!(
+                                "variant.{}.field.{}",
+                                variant.name.unwrap(),
+                                field.name.unwrap()
+                            ));
+                            write!(
+                                w,
+                                "<div class=\"sub-variant-field\">\
+                                 <span id=\"{id}\" class=\"variant small-section-header\">\
+                                     <a href=\"#{id}\" class=\"anchor field\"></a>\
+                                     <code>{f}:&nbsp;{t}</code>\
+                                 </span>",
+                                id = id,
+                                f = field.name.unwrap(),
+                                t = ty.print(cx)
+                            );
+                            document(w, cx, field, Some(variant), HeadingOffset::H5);
+                            write!(w, "</div>");
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+                w.write_str("</div>");
+            }
+
+            document(w, cx, variant, Some(it), HeadingOffset::H4);
+        }
+    }
+    let def_id = it.item_id.expect_def_id();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_type_layout(w, cx, def_id);
+}
+
+fn item_macro(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, t: &clean::Macro) {
+    wrap_into_docblock(w, |w| {
+        highlight::render_with_highlighting(
+            &t.source,
+            w,
+            Some("macro"),
+            None,
+            None,
+            it.span(cx.tcx()).inner().edition(),
+            None,
+            None,
+            None,
+        );
+    });
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+fn item_proc_macro(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, m: &clean::ProcMacro) {
+    wrap_into_docblock(w, |w| {
+        let name = it.name.expect("proc-macros always have names");
+        match m.kind {
+            MacroKind::Bang => {
+                wrap_item(w, "macro", |w| {
+                    write!(w, "{}!() {{ /* proc-macro */ }}", name);
+                });
+            }
+            MacroKind::Attr => {
+                wrap_item(w, "attr", |w| {
+                    write!(w, "#[{}]", name);
+                });
+            }
+            MacroKind::Derive => {
+                wrap_item(w, "derive", |w| {
+                    write!(w, "#[derive({})]", name);
+                    if !m.helpers.is_empty() {
+                        w.push_str("\n{\n");
+                        w.push_str("    // Attributes available to this derive:\n");
+                        for attr in &m.helpers {
+                            writeln!(w, "    #[{}]", attr);
+                        }
+                        w.push_str("}\n");
+                    }
+                });
+            }
+        }
+    });
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+fn item_primitive(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
+    document(w, cx, it, None, HeadingOffset::H2);
+    render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
+}
+
+fn item_constant(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, c: &clean::Constant) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "const", |w| {
+            render_attributes_in_code(w, it);
+
+            write!(
+                w,
+                "{vis}const {name}: {typ}",
+                vis = it.visibility.print_with_space(it.item_id, cx),
+                name = it.name.unwrap(),
+                typ = c.type_.print(cx),
+            );
+
+            // FIXME: The code below now prints
+            //            ` = _; // 100i32`
+            //        if the expression is
+            //            `50 + 50`
+            //        which looks just wrong.
+            //        Should we print
+            //            ` = 100i32;`
+            //        instead?
+
+            let value = c.value(cx.tcx());
+            let is_literal = c.is_literal(cx.tcx());
+            let expr = c.expr(cx.tcx());
+            if value.is_some() || is_literal {
+                write!(w, " = {expr};", expr = Escape(&expr));
+            } else {
+                w.write_str(";");
+            }
+
+            if !is_literal {
+                if let Some(value) = &value {
+                    let value_lowercase = value.to_lowercase();
+                    let expr_lowercase = expr.to_lowercase();
+
+                    if value_lowercase != expr_lowercase
+                        && value_lowercase.trim_end_matches("i32") != expr_lowercase
+                    {
+                        write!(w, " // {value}", value = Escape(value));
+                    }
+                }
+            }
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+fn item_struct(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Struct) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "struct", |w| {
+            render_attributes_in_code(w, it);
+            render_struct(w, it, Some(&s.generics), s.struct_type, &s.fields, "", true, cx);
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    let mut fields = s
+        .fields
+        .iter()
+        .filter_map(|f| match *f.kind {
+            clean::StructFieldItem(ref ty) => Some((f, ty)),
+            _ => None,
+        })
+        .peekable();
+    if let CtorKind::Fictive | CtorKind::Fn = s.struct_type {
+        if fields.peek().is_some() {
+            write!(
+                w,
+                "<h2 id=\"fields\" class=\"fields small-section-header\">\
+                     {}{}<a href=\"#fields\" class=\"anchor\"></a>\
+                 </h2>",
+                if let CtorKind::Fictive = s.struct_type { "Fields" } else { "Tuple Fields" },
+                document_non_exhaustive_header(it)
+            );
+            document_non_exhaustive(w, it);
+            for (index, (field, ty)) in fields.enumerate() {
+                let field_name =
+                    field.name.map_or_else(|| index.to_string(), |sym| sym.as_str().to_string());
+                let id = cx.derive_id(format!("{}.{}", ItemType::StructField, field_name));
+                write!(
+                    w,
+                    "<span id=\"{id}\" class=\"{item_type} small-section-header\">\
+                         <a href=\"#{id}\" class=\"anchor field\"></a>\
+                         <code>{name}: {ty}</code>\
+                     </span>",
+                    item_type = ItemType::StructField,
+                    id = id,
+                    name = field_name,
+                    ty = ty.print(cx)
+                );
+                document(w, cx, field, Some(it), HeadingOffset::H3);
+            }
+        }
+    }
+    let def_id = it.item_id.expect_def_id();
+    render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_type_layout(w, cx, def_id);
+}
+
+fn item_static(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, s: &clean::Static) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "static", |w| {
+            render_attributes_in_code(w, it);
+            write!(
+                w,
+                "{vis}static {mutability}{name}: {typ}",
+                vis = it.visibility.print_with_space(it.item_id, cx),
+                mutability = s.mutability.print_with_space(),
+                name = it.name.unwrap(),
+                typ = s.type_.print(cx)
+            );
+        });
+    });
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+fn item_foreign_type(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
+    wrap_into_docblock(w, |w| {
+        wrap_item(w, "foreigntype", |w| {
+            w.write_str("extern {\n");
+            render_attributes_in_code(w, it);
+            write!(
+                w,
+                "    {}type {};\n}}",
+                it.visibility.print_with_space(it.item_id, cx),
+                it.name.unwrap(),
+            );
+        });
+    });
+
+    document(w, cx, it, None, HeadingOffset::H2);
+
+    render_assoc_items(w, cx, it, it.item_id.expect_def_id(), AssocItemRender::All)
+}
+
+fn item_keyword(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item) {
+    document(w, cx, it, None, HeadingOffset::H2)
+}
+
+/// Compare two strings treating multi-digit numbers as single units (i.e. natural sort order).
+pub(crate) fn compare_names(mut lhs: &str, mut rhs: &str) -> Ordering {
+    /// Takes a non-numeric and a numeric part from the given &str.
+    fn take_parts<'a>(s: &mut &'a str) -> (&'a str, &'a str) {
+        let i = s.find(|c: char| c.is_ascii_digit());
+        let (a, b) = s.split_at(i.unwrap_or(s.len()));
+        let i = b.find(|c: char| !c.is_ascii_digit());
+        let (b, c) = b.split_at(i.unwrap_or(b.len()));
+        *s = c;
+        (a, b)
+    }
+
+    while !lhs.is_empty() || !rhs.is_empty() {
+        let (la, lb) = take_parts(&mut lhs);
+        let (ra, rb) = take_parts(&mut rhs);
+        // First process the non-numeric part.
+        match la.cmp(ra) {
+            Ordering::Equal => (),
+            x => return x,
+        }
+        // Then process the numeric part, if both sides have one (and they fit in a u64).
+        if let (Ok(ln), Ok(rn)) = (lb.parse::<u64>(), rb.parse::<u64>()) {
+            match ln.cmp(&rn) {
+                Ordering::Equal => (),
+                x => return x,
+            }
+        }
+        // Then process the numeric part again, but this time as strings.
+        match lb.cmp(rb) {
+            Ordering::Equal => (),
+            x => return x,
+        }
+    }
+
+    Ordering::Equal
+}
+
+pub(super) fn full_path(cx: &Context<'_>, item: &clean::Item) -> String {
+    let mut s = join_with_double_colon(&cx.current);
+    s.push_str("::");
+    s.push_str(item.name.unwrap().as_str());
+    s
+}
+
+pub(super) fn item_path(ty: ItemType, name: &str) -> String {
+    match ty {
+        ItemType::Module => format!("{}index.html", ensure_trailing_slash(name)),
+        _ => format!("{}.{}.html", ty, name),
+    }
+}
+
+fn bounds(t_bounds: &[clean::GenericBound], trait_alias: bool, cx: &Context<'_>) -> String {
+    let mut bounds = String::new();
+    if !t_bounds.is_empty() {
+        if !trait_alias {
+            bounds.push_str(": ");
+        }
+        for (i, p) in t_bounds.iter().enumerate() {
+            if i > 0 {
+                bounds.push_str(" + ");
+            }
+            bounds.push_str(&p.print(cx).to_string());
+        }
+    }
+    bounds
+}
+
+fn wrap_into_docblock<F>(w: &mut Buffer, f: F)
+where
+    F: FnOnce(&mut Buffer),
+{
+    w.write_str("<div class=\"docblock item-decl\">");
+    f(w);
+    w.write_str("</div>")
+}
+
+fn wrap_item<F>(w: &mut Buffer, item_name: &str, f: F)
+where
+    F: FnOnce(&mut Buffer),
+{
+    w.write_fmt(format_args!("<pre class=\"rust {}\"><code>", item_name));
+    f(w);
+    w.write_str("</code></pre>");
+}
+
+fn render_stability_since(
+    w: &mut Buffer,
+    item: &clean::Item,
+    containing_item: &clean::Item,
+    tcx: TyCtxt<'_>,
+) -> bool {
+    render_stability_since_raw(
+        w,
+        item.stable_since(tcx),
+        item.const_stability(tcx),
+        containing_item.stable_since(tcx),
+        containing_item.const_stable_since(tcx),
+    )
+}
+
+fn compare_impl<'a, 'b>(lhs: &'a &&Impl, rhs: &'b &&Impl, cx: &Context<'_>) -> Ordering {
+    let lhss = format!("{}", lhs.inner_impl().print(false, cx));
+    let rhss = format!("{}", rhs.inner_impl().print(false, cx));
+
+    // lhs and rhs are formatted as HTML, which may be unnecessary
+    compare_names(&lhss, &rhss)
+}
+
+fn render_implementor(
+    cx: &mut Context<'_>,
+    implementor: &Impl,
+    trait_: &clean::Item,
+    w: &mut Buffer,
+    implementor_dups: &FxHashMap<Symbol, (DefId, bool)>,
+    aliases: &[String],
+) {
+    // If there's already another implementor that has the same abridged name, use the
+    // full path, for example in `std::iter::ExactSizeIterator`
+    let use_absolute = match implementor.inner_impl().for_ {
+        clean::Type::Path { ref path, .. }
+        | clean::BorrowedRef { type_: box clean::Type::Path { ref path, .. }, .. }
+            if !path.is_assoc_ty() =>
+        {
+            implementor_dups[&path.last()].1
+        }
+        _ => false,
+    };
+    render_impl(
+        w,
+        cx,
+        implementor,
+        trait_,
+        AssocItemLink::Anchor(None),
+        RenderMode::Normal,
+        Some(use_absolute),
+        aliases,
+        ImplRenderingParameters {
+            show_def_docs: false,
+            show_default_items: false,
+            show_non_assoc_items: false,
+            toggle_open_by_default: false,
+        },
+    );
+}
+
+fn render_union(
+    w: &mut Buffer,
+    it: &clean::Item,
+    g: Option<&clean::Generics>,
+    fields: &[clean::Item],
+    tab: &str,
+    cx: &Context<'_>,
+) {
+    write!(w, "{}union {}", it.visibility.print_with_space(it.item_id, cx), it.name.unwrap(),);
+
+    let where_displayed = g
+        .map(|g| {
+            write!(w, "{}", g.print(cx));
+            print_where_clause_and_check(w, g, cx)
+        })
+        .unwrap_or(false);
+
+    // If there wasn't a `where` clause, we add a whitespace.
+    if !where_displayed {
+        w.write_str(" ");
+    }
+
+    write!(w, "{{\n{}", tab);
+    let count_fields =
+        fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
+    let toggle = should_hide_fields(count_fields);
+    if toggle {
+        toggle_open(w, format_args!("{} fields", count_fields));
+    }
+
+    for field in fields {
+        if let clean::StructFieldItem(ref ty) = *field.kind {
+            write!(
+                w,
+                "    {}{}: {},\n{}",
+                field.visibility.print_with_space(field.item_id, cx),
+                field.name.unwrap(),
+                ty.print(cx),
+                tab
+            );
+        }
+    }
+
+    if it.has_stripped_entries().unwrap() {
+        write!(w, "    /* private fields */\n{}", tab);
+    }
+    if toggle {
+        toggle_close(w);
+    }
+    w.write_str("}");
+}
+
+fn render_struct(
+    w: &mut Buffer,
+    it: &clean::Item,
+    g: Option<&clean::Generics>,
+    ty: CtorKind,
+    fields: &[clean::Item],
+    tab: &str,
+    structhead: bool,
+    cx: &Context<'_>,
+) {
+    write!(
+        w,
+        "{}{}{}",
+        it.visibility.print_with_space(it.item_id, cx),
+        if structhead { "struct " } else { "" },
+        it.name.unwrap()
+    );
+    if let Some(g) = g {
+        write!(w, "{}", g.print(cx))
+    }
+    match ty {
+        CtorKind::Fictive => {
+            let where_diplayed = g.map(|g| print_where_clause_and_check(w, g, cx)).unwrap_or(false);
+
+            // If there wasn't a `where` clause, we add a whitespace.
+            if !where_diplayed {
+                w.write_str(" {");
+            } else {
+                w.write_str("{");
+            }
+            let count_fields =
+                fields.iter().filter(|f| matches!(*f.kind, clean::StructFieldItem(..))).count();
+            let has_visible_fields = count_fields > 0;
+            let toggle = should_hide_fields(count_fields);
+            if toggle {
+                toggle_open(w, format_args!("{} fields", count_fields));
+            }
+            for field in fields {
+                if let clean::StructFieldItem(ref ty) = *field.kind {
+                    write!(
+                        w,
+                        "\n{}    {}{}: {},",
+                        tab,
+                        field.visibility.print_with_space(field.item_id, cx),
+                        field.name.unwrap(),
+                        ty.print(cx),
+                    );
+                }
+            }
+
+            if has_visible_fields {
+                if it.has_stripped_entries().unwrap() {
+                    write!(w, "\n{}    /* private fields */", tab);
+                }
+                write!(w, "\n{}", tab);
+            } else if it.has_stripped_entries().unwrap() {
+                write!(w, " /* private fields */ ");
+            }
+            if toggle {
+                toggle_close(w);
+            }
+            w.write_str("}");
+        }
+        CtorKind::Fn => {
+            w.write_str("(");
+            for (i, field) in fields.iter().enumerate() {
+                if i > 0 {
+                    w.write_str(", ");
+                }
+                match *field.kind {
+                    clean::StrippedItem(box clean::StructFieldItem(..)) => write!(w, "_"),
+                    clean::StructFieldItem(ref ty) => {
+                        write!(
+                            w,
+                            "{}{}",
+                            field.visibility.print_with_space(field.item_id, cx),
+                            ty.print(cx),
+                        )
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            w.write_str(")");
+            if let Some(g) = g {
+                write!(w, "{}", print_where_clause(g, cx, 0, Ending::NoNewline));
+            }
+            // We only want a ";" when we are displaying a tuple struct, not a variant tuple struct.
+            if structhead {
+                w.write_str(";");
+            }
+        }
+        CtorKind::Const => {
+            // Needed for PhantomData.
+            if let Some(g) = g {
+                write!(w, "{}", print_where_clause(g, cx, 0, Ending::NoNewline));
+            }
+            w.write_str(";");
+        }
+    }
+}
+
+fn document_non_exhaustive_header(item: &clean::Item) -> &str {
+    if item.is_non_exhaustive() { " (Non-exhaustive)" } else { "" }
+}
+
+fn document_non_exhaustive(w: &mut Buffer, item: &clean::Item) {
+    if item.is_non_exhaustive() {
+        write!(
+            w,
+            "<details class=\"rustdoc-toggle non-exhaustive\">\
+                 <summary class=\"hideme\"><span>{}</span></summary>\
+                 <div class=\"docblock\">",
+            {
+                if item.is_struct() {
+                    "This struct is marked as non-exhaustive"
+                } else if item.is_enum() {
+                    "This enum is marked as non-exhaustive"
+                } else if item.is_variant() {
+                    "This variant is marked as non-exhaustive"
+                } else {
+                    "This type is marked as non-exhaustive"
+                }
+            }
+        );
+
+        if item.is_struct() {
+            w.write_str(
+                "Non-exhaustive structs could have additional fields added in future. \
+                 Therefore, non-exhaustive structs cannot be constructed in external crates \
+                 using the traditional <code>Struct { .. }</code> syntax; cannot be \
+                 matched against without a wildcard <code>..</code>; and \
+                 struct update syntax will not work.",
+            );
+        } else if item.is_enum() {
+            w.write_str(
+                "Non-exhaustive enums could have additional variants added in future. \
+                 Therefore, when matching against variants of non-exhaustive enums, an \
+                 extra wildcard arm must be added to account for any future variants.",
+            );
+        } else if item.is_variant() {
+            w.write_str(
+                "Non-exhaustive enum variants could have additional fields added in future. \
+                 Therefore, non-exhaustive enum variants cannot be constructed in external \
+                 crates and cannot be matched against.",
+            );
+        } else {
+            w.write_str(
+                "This type will require a wildcard arm in any match statements or constructors.",
+            );
+        }
+
+        w.write_str("</div></details>");
+    }
+}
+
+fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
+    fn write_size_of_layout(w: &mut Buffer, layout: Layout<'_>, tag_size: u64) {
+        if layout.abi().is_unsized() {
+            write!(w, "(unsized)");
+        } else {
+            let bytes = layout.size().bytes() - tag_size;
+            write!(w, "{size} byte{pl}", size = bytes, pl = if bytes == 1 { "" } else { "s" },);
+        }
+    }
+
+    if !cx.shared.show_type_layout {
+        return;
+    }
+
+    writeln!(
+        w,
+        "<h2 id=\"layout\" class=\"small-section-header\"> \
+        Layout<a href=\"#layout\" class=\"anchor\"></a></h2>"
+    );
+    writeln!(w, "<div class=\"docblock\">");
+
+    let tcx = cx.tcx();
+    let param_env = tcx.param_env(ty_def_id);
+    let ty = tcx.type_of(ty_def_id);
+    match tcx.layout_of(param_env.and(ty)) {
+        Ok(ty_layout) => {
+            writeln!(
+                w,
+                "<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
+                 <strong>completely unstable</strong> and may even differ between compilations. \
+                 The only exception is types with certain <code>repr(...)</code> attributes. \
+                 Please see the Rust Reference’s \
+                 <a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
+                 chapter for details on type layout guarantees.</p></div>"
+            );
+            w.write_str("<p><strong>Size:</strong> ");
+            write_size_of_layout(w, ty_layout.layout, 0);
+            writeln!(w, "</p>");
+            if let Variants::Multiple { variants, tag, tag_encoding, .. } =
+                &ty_layout.layout.variants()
+            {
+                if !variants.is_empty() {
+                    w.write_str(
+                        "<p><strong>Size for each variant:</strong></p>\
+                            <ul>",
+                    );
+
+                    let Adt(adt, _) = ty_layout.ty.kind() else {
+                        span_bug!(tcx.def_span(ty_def_id), "not an adt")
+                    };
+
+                    let tag_size = if let TagEncoding::Niche { .. } = tag_encoding {
+                        0
+                    } else if let Primitive::Int(i, _) = tag.primitive() {
+                        i.size().bytes()
+                    } else {
+                        span_bug!(tcx.def_span(ty_def_id), "tag is neither niche nor int")
+                    };
+
+                    for (index, layout) in variants.iter_enumerated() {
+                        let name = adt.variant(index).name;
+                        write!(w, "<li><code>{name}</code>: ", name = name);
+                        write_size_of_layout(w, *layout, tag_size);
+                        writeln!(w, "</li>");
+                    }
+                    w.write_str("</ul>");
+                }
+            }
+        }
+        // This kind of layout error can occur with valid code, e.g. if you try to
+        // get the layout of a generic type such as `Vec<T>`.
+        Err(LayoutError::Unknown(_)) => {
+            writeln!(
+                w,
+                "<p><strong>Note:</strong> Unable to compute type layout, \
+                 possibly due to this type having generic parameters. \
+                 Layout can only be computed for concrete, fully-instantiated types.</p>"
+            );
+        }
+        // This kind of error probably can't happen with valid code, but we don't
+        // want to panic and prevent the docs from building, so we just let the
+        // user know that we couldn't compute the layout.
+        Err(LayoutError::SizeOverflow(_)) => {
+            writeln!(
+                w,
+                "<p><strong>Note:</strong> Encountered an error during type layout; \
+                 the type was too big.</p>"
+            );
+        }
+        Err(LayoutError::NormalizationFailure(_, _)) => {
+            writeln!(
+                w,
+                "<p><strong>Note:</strong> Encountered an error during type layout; \
+                the type failed to be normalized.</p>"
+            )
+        }
+    }
+
+    writeln!(w, "</div>");
+}
+
+fn pluralize(count: usize) -> &'static str {
+    if count > 1 { "s" } else { "" }
+}
diff --git a/src/librustdoc/html/render/search_index.rs b/src/librustdoc/html/render/search_index.rs
new file mode 100644
index 000000000..d672f0bb5
--- /dev/null
+++ b/src/librustdoc/html/render/search_index.rs
@@ -0,0 +1,589 @@
+use std::collections::hash_map::Entry;
+use std::collections::BTreeMap;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::def_id::LOCAL_CRATE;
+use rustc_span::symbol::Symbol;
+use serde::ser::{Serialize, SerializeStruct, Serializer};
+
+use crate::clean;
+use crate::clean::types::{
+    FnRetTy, Function, GenericBound, Generics, ItemId, Type, WherePredicate,
+};
+use crate::formats::cache::{Cache, OrphanImplItem};
+use crate::formats::item_type::ItemType;
+use crate::html::format::join_with_double_colon;
+use crate::html::markdown::short_markdown_summary;
+use crate::html::render::{IndexItem, IndexItemFunctionType, RenderType, RenderTypeId};
+
+/// Builds the search index from the collected metadata
+pub(crate) fn build_index<'tcx>(
+    krate: &clean::Crate,
+    cache: &mut Cache,
+    tcx: TyCtxt<'tcx>,
+) -> String {
+    let mut itemid_to_pathid = FxHashMap::default();
+    let mut crate_paths = vec![];
+
+    // Attach all orphan items to the type's definition if the type
+    // has since been learned.
+    for &OrphanImplItem { parent, ref item, ref impl_generics } in &cache.orphan_impl_items {
+        if let Some(&(ref fqp, _)) = cache.paths.get(&parent) {
+            let desc = item
+                .doc_value()
+                .map_or_else(String::new, |s| short_markdown_summary(&s, &item.link_names(cache)));
+            cache.search_index.push(IndexItem {
+                ty: item.type_(),
+                name: item.name.unwrap().to_string(),
+                path: join_with_double_colon(&fqp[..fqp.len() - 1]),
+                desc,
+                parent: Some(parent),
+                parent_idx: None,
+                search_type: get_function_type_for_search(item, tcx, impl_generics.as_ref(), cache),
+                aliases: item.attrs.get_doc_aliases(),
+            });
+        }
+    }
+
+    let crate_doc = krate
+        .module
+        .doc_value()
+        .map_or_else(String::new, |s| short_markdown_summary(&s, &krate.module.link_names(cache)));
+
+    // Aliases added through `#[doc(alias = "...")]`. Since a few items can have the same alias,
+    // we need the alias element to have an array of items.
+    let mut aliases: BTreeMap<String, Vec<usize>> = BTreeMap::new();
+
+    // Sort search index items. This improves the compressibility of the search index.
+    cache.search_index.sort_unstable_by(|k1, k2| {
+        // `sort_unstable_by_key` produces lifetime errors
+        let k1 = (&k1.path, &k1.name, &k1.ty, &k1.parent);
+        let k2 = (&k2.path, &k2.name, &k2.ty, &k2.parent);
+        std::cmp::Ord::cmp(&k1, &k2)
+    });
+
+    // Set up alias indexes.
+    for (i, item) in cache.search_index.iter().enumerate() {
+        for alias in &item.aliases[..] {
+            aliases.entry(alias.as_str().to_lowercase()).or_default().push(i);
+        }
+    }
+
+    // Reduce `DefId` in paths into smaller sequential numbers,
+    // and prune the paths that do not appear in the index.
+    let mut lastpath = "";
+    let mut lastpathid = 0usize;
+
+    // First, on function signatures
+    let mut search_index = std::mem::replace(&mut cache.search_index, Vec::new());
+    for item in search_index.iter_mut() {
+        fn convert_render_type(
+            ty: &mut RenderType,
+            cache: &mut Cache,
+            itemid_to_pathid: &mut FxHashMap<ItemId, usize>,
+            lastpathid: &mut usize,
+            crate_paths: &mut Vec<(ItemType, Symbol)>,
+        ) {
+            if let Some(generics) = &mut ty.generics {
+                for item in generics {
+                    convert_render_type(item, cache, itemid_to_pathid, lastpathid, crate_paths);
+                }
+            }
+            let Cache { ref paths, ref external_paths, .. } = *cache;
+            let Some(id) = ty.id.clone() else {
+                assert!(ty.generics.is_some());
+                return;
+            };
+            let (itemid, path, item_type) = match id {
+                RenderTypeId::DefId(defid) => {
+                    if let Some(&(ref fqp, item_type)) =
+                        paths.get(&defid).or_else(|| external_paths.get(&defid))
+                    {
+                        (ItemId::DefId(defid), *fqp.last().unwrap(), item_type)
+                    } else {
+                        ty.id = None;
+                        return;
+                    }
+                }
+                RenderTypeId::Primitive(primitive) => (
+                    ItemId::Primitive(primitive, LOCAL_CRATE),
+                    primitive.as_sym(),
+                    ItemType::Primitive,
+                ),
+                RenderTypeId::Index(_) => return,
+            };
+            match itemid_to_pathid.entry(itemid) {
+                Entry::Occupied(entry) => ty.id = Some(RenderTypeId::Index(*entry.get())),
+                Entry::Vacant(entry) => {
+                    let pathid = *lastpathid;
+                    entry.insert(pathid);
+                    *lastpathid += 1;
+                    crate_paths.push((item_type, path));
+                    ty.id = Some(RenderTypeId::Index(pathid));
+                }
+            }
+        }
+        if let Some(search_type) = &mut item.search_type {
+            for item in &mut search_type.inputs {
+                convert_render_type(
+                    item,
+                    cache,
+                    &mut itemid_to_pathid,
+                    &mut lastpathid,
+                    &mut crate_paths,
+                );
+            }
+            for item in &mut search_type.output {
+                convert_render_type(
+                    item,
+                    cache,
+                    &mut itemid_to_pathid,
+                    &mut lastpathid,
+                    &mut crate_paths,
+                );
+            }
+        }
+    }
+
+    let Cache { ref paths, .. } = *cache;
+
+    // Then, on parent modules
+    let crate_items: Vec<&IndexItem> = search_index
+        .iter_mut()
+        .map(|item| {
+            item.parent_idx =
+                item.parent.and_then(|defid| match itemid_to_pathid.entry(ItemId::DefId(defid)) {
+                    Entry::Occupied(entry) => Some(*entry.get()),
+                    Entry::Vacant(entry) => {
+                        let pathid = lastpathid;
+                        entry.insert(pathid);
+                        lastpathid += 1;
+
+                        if let Some(&(ref fqp, short)) = paths.get(&defid) {
+                            crate_paths.push((short, *fqp.last().unwrap()));
+                            Some(pathid)
+                        } else {
+                            None
+                        }
+                    }
+                });
+
+            // Omit the parent path if it is same to that of the prior item.
+            if lastpath == &item.path {
+                item.path.clear();
+            } else {
+                lastpath = &item.path;
+            }
+
+            &*item
+        })
+        .collect();
+
+    struct CrateData<'a> {
+        doc: String,
+        items: Vec<&'a IndexItem>,
+        paths: Vec<(ItemType, Symbol)>,
+        // The String is alias name and the vec is the list of the elements with this alias.
+        //
+        // To be noted: the `usize` elements are indexes to `items`.
+        aliases: &'a BTreeMap<String, Vec<usize>>,
+    }
+
+    impl<'a> Serialize for CrateData<'a> {
+        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where
+            S: Serializer,
+        {
+            let has_aliases = !self.aliases.is_empty();
+            let mut crate_data =
+                serializer.serialize_struct("CrateData", if has_aliases { 9 } else { 8 })?;
+            crate_data.serialize_field("doc", &self.doc)?;
+            crate_data.serialize_field(
+                "t",
+                &self.items.iter().map(|item| &item.ty).collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "n",
+                &self.items.iter().map(|item| &item.name).collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "q",
+                &self.items.iter().map(|item| &item.path).collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "d",
+                &self.items.iter().map(|item| &item.desc).collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "i",
+                &self
+                    .items
+                    .iter()
+                    .map(|item| {
+                        assert_eq!(
+                            item.parent.is_some(),
+                            item.parent_idx.is_some(),
+                            "`{}` is missing idx",
+                            item.name
+                        );
+                        // 0 is a sentinel, everything else is one-indexed
+                        item.parent_idx.map(|x| x + 1).unwrap_or(0)
+                    })
+                    .collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "f",
+                &self
+                    .items
+                    .iter()
+                    .map(|item| {
+                        // Fake option to get `0` out as a sentinel instead of `null`.
+                        // We want to use `0` because it's three less bytes.
+                        enum FunctionOption<'a> {
+                            Function(&'a IndexItemFunctionType),
+                            None,
+                        }
+                        impl<'a> Serialize for FunctionOption<'a> {
+                            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+                            where
+                                S: Serializer,
+                            {
+                                match self {
+                                    FunctionOption::None => 0.serialize(serializer),
+                                    FunctionOption::Function(ty) => ty.serialize(serializer),
+                                }
+                            }
+                        }
+                        match &item.search_type {
+                            Some(ty) => FunctionOption::Function(ty),
+                            None => FunctionOption::None,
+                        }
+                    })
+                    .collect::<Vec<_>>(),
+            )?;
+            crate_data.serialize_field(
+                "p",
+                &self.paths.iter().map(|(it, s)| (it, s.to_string())).collect::<Vec<_>>(),
+            )?;
+            if has_aliases {
+                crate_data.serialize_field("a", &self.aliases)?;
+            }
+            crate_data.end()
+        }
+    }
+
+    // Collect the index into a string
+    format!(
+        r#""{}":{}"#,
+        krate.name(tcx),
+        serde_json::to_string(&CrateData {
+            doc: crate_doc,
+            items: crate_items,
+            paths: crate_paths,
+            aliases: &aliases,
+        })
+        .expect("failed serde conversion")
+        // All these `replace` calls are because we have to go through JS string for JSON content.
+        .replace('\\', r"\\")
+        .replace('\'', r"\'")
+        // We need to escape double quotes for the JSON.
+        .replace("\\\"", "\\\\\"")
+    )
+}
+
+pub(crate) fn get_function_type_for_search<'tcx>(
+    item: &clean::Item,
+    tcx: TyCtxt<'tcx>,
+    impl_generics: Option<&(clean::Type, clean::Generics)>,
+    cache: &Cache,
+) -> Option<IndexItemFunctionType> {
+    let (mut inputs, mut output) = match *item.kind {
+        clean::FunctionItem(ref f) => get_fn_inputs_and_outputs(f, tcx, impl_generics, cache),
+        clean::MethodItem(ref m, _) => get_fn_inputs_and_outputs(m, tcx, impl_generics, cache),
+        clean::TyMethodItem(ref m) => get_fn_inputs_and_outputs(m, tcx, impl_generics, cache),
+        _ => return None,
+    };
+
+    inputs.retain(|a| a.id.is_some() || a.generics.is_some());
+    output.retain(|a| a.id.is_some() || a.generics.is_some());
+
+    Some(IndexItemFunctionType { inputs, output })
+}
+
+fn get_index_type(clean_type: &clean::Type, generics: Vec<RenderType>) -> RenderType {
+    RenderType {
+        id: get_index_type_id(clean_type),
+        generics: if generics.is_empty() { None } else { Some(generics) },
+    }
+}
+
+fn get_index_type_id(clean_type: &clean::Type) -> Option<RenderTypeId> {
+    match *clean_type {
+        clean::Type::Path { ref path, .. } => Some(RenderTypeId::DefId(path.def_id())),
+        clean::DynTrait(ref bounds, _) => {
+            let path = &bounds[0].trait_;
+            Some(RenderTypeId::DefId(path.def_id()))
+        }
+        clean::Primitive(p) => Some(RenderTypeId::Primitive(p)),
+        clean::BorrowedRef { ref type_, .. } | clean::RawPointer(_, ref type_) => {
+            get_index_type_id(type_)
+        }
+        clean::BareFunction(_)
+        | clean::Generic(_)
+        | clean::ImplTrait(_)
+        | clean::Tuple(_)
+        | clean::Slice(_)
+        | clean::Array(_, _)
+        | clean::QPath { .. }
+        | clean::Infer => None,
+    }
+}
+
+/// The point of this function is to replace bounds with types.
+///
+/// i.e. `[T, U]` when you have the following bounds: `T: Display, U: Option<T>` will return
+/// `[Display, Option]`. If a type parameter has no trait bound, it is discarded.
+///
+/// Important note: It goes through generics recursively. So if you have
+/// `T: Option<Result<(), ()>>`, it'll go into `Option` and then into `Result`.
+#[instrument(level = "trace", skip(tcx, res, cache))]
+fn add_generics_and_bounds_as_types<'tcx, 'a>(
+    self_: Option<&'a Type>,
+    generics: &Generics,
+    arg: &'a Type,
+    tcx: TyCtxt<'tcx>,
+    recurse: usize,
+    res: &mut Vec<RenderType>,
+    cache: &Cache,
+) {
+    fn insert_ty(res: &mut Vec<RenderType>, ty: Type, mut generics: Vec<RenderType>) {
+        // generics and impl trait are both identified by their generics,
+        // rather than a type name itself
+        let anonymous = ty.is_full_generic() || ty.is_impl_trait();
+        let generics_empty = generics.is_empty();
+
+        if anonymous {
+            if generics_empty {
+                // This is a type parameter with no trait bounds (for example: `T` in
+                // `fn f<T>(p: T)`, so not useful for the rustdoc search because we would end up
+                // with an empty type with an empty name. Let's just discard it.
+                return;
+            } else if generics.len() == 1 {
+                // In this case, no need to go through an intermediate state if the type parameter
+                // contains only one trait bound.
+                //
+                // For example:
+                //
+                // `fn foo<T: Display>(r: Option<T>) {}`
+                //
+                // In this case, it would contain:
+                //
+                // ```
+                // [{
+                //     name: "option",
+                //     generics: [{
+                //         name: "",
+                //         generics: [
+                //             name: "Display",
+                //             generics: []
+                //         }]
+                //     }]
+                // }]
+                // ```
+                //
+                // After removing the intermediate (unnecessary) type parameter, it'll become:
+                //
+                // ```
+                // [{
+                //     name: "option",
+                //     generics: [{
+                //         name: "Display",
+                //         generics: []
+                //     }]
+                // }]
+                // ```
+                //
+                // To be noted that it can work if there is ONLY ONE trait bound, otherwise we still
+                // need to keep it as is!
+                res.push(generics.pop().unwrap());
+                return;
+            }
+        }
+        let index_ty = get_index_type(&ty, generics);
+        if index_ty.id.is_none() && generics_empty {
+            return;
+        }
+        res.push(index_ty);
+    }
+
+    if recurse >= 10 {
+        // FIXME: remove this whole recurse thing when the recursion bug is fixed
+        // See #59502 for the original issue.
+        return;
+    }
+
+    // First, check if it's "Self".
+    let arg = if let Some(self_) = self_ {
+        match &*arg {
+            Type::BorrowedRef { type_, .. } if type_.is_self_type() => self_,
+            type_ if type_.is_self_type() => self_,
+            arg => arg,
+        }
+    } else {
+        arg
+    };
+
+    // If this argument is a type parameter and not a trait bound or a type, we need to look
+    // for its bounds.
+    if let Type::Generic(arg_s) = *arg {
+        // First we check if the bounds are in a `where` predicate...
+        if let Some(where_pred) = generics.where_predicates.iter().find(|g| match g {
+            WherePredicate::BoundPredicate { ty, .. } => ty.def_id(cache) == arg.def_id(cache),
+            _ => false,
+        }) {
+            let mut ty_generics = Vec::new();
+            let bounds = where_pred.get_bounds().unwrap_or_else(|| &[]);
+            for bound in bounds.iter() {
+                if let GenericBound::TraitBound(poly_trait, _) = bound {
+                    for param_def in poly_trait.generic_params.iter() {
+                        match &param_def.kind {
+                            clean::GenericParamDefKind::Type { default: Some(ty), .. } => {
+                                add_generics_and_bounds_as_types(
+                                    self_,
+                                    generics,
+                                    ty,
+                                    tcx,
+                                    recurse + 1,
+                                    &mut ty_generics,
+                                    cache,
+                                )
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+            }
+            insert_ty(res, arg.clone(), ty_generics);
+        }
+        // Otherwise we check if the trait bounds are "inlined" like `T: Option<u32>`...
+        if let Some(bound) = generics.params.iter().find(|g| g.is_type() && g.name == arg_s) {
+            let mut ty_generics = Vec::new();
+            for bound in bound.get_bounds().unwrap_or(&[]) {
+                if let Some(path) = bound.get_trait_path() {
+                    let ty = Type::Path { path };
+                    add_generics_and_bounds_as_types(
+                        self_,
+                        generics,
+                        &ty,
+                        tcx,
+                        recurse + 1,
+                        &mut ty_generics,
+                        cache,
+                    );
+                }
+            }
+            insert_ty(res, arg.clone(), ty_generics);
+        }
+    } else if let Type::ImplTrait(ref bounds) = *arg {
+        let mut ty_generics = Vec::new();
+        for bound in bounds {
+            if let Some(path) = bound.get_trait_path() {
+                let ty = Type::Path { path };
+                add_generics_and_bounds_as_types(
+                    self_,
+                    generics,
+                    &ty,
+                    tcx,
+                    recurse + 1,
+                    &mut ty_generics,
+                    cache,
+                );
+            }
+        }
+        insert_ty(res, arg.clone(), ty_generics);
+    } else {
+        // This is not a type parameter. So for example if we have `T, U: Option<T>`, and we're
+        // looking at `Option`, we enter this "else" condition, otherwise if it's `T`, we don't.
+        //
+        // So in here, we can add it directly and look for its own type parameters (so for `Option`,
+        // we will look for them but not for `T`).
+        let mut ty_generics = Vec::new();
+        if let Some(arg_generics) = arg.generics() {
+            for gen in arg_generics.iter() {
+                add_generics_and_bounds_as_types(
+                    self_,
+                    generics,
+                    gen,
+                    tcx,
+                    recurse + 1,
+                    &mut ty_generics,
+                    cache,
+                );
+            }
+        }
+        insert_ty(res, arg.clone(), ty_generics);
+    }
+}
+
+/// Return the full list of types when bounds have been resolved.
+///
+/// i.e. `fn foo<A: Display, B: Option<A>>(x: u32, y: B)` will return
+/// `[u32, Display, Option]`.
+fn get_fn_inputs_and_outputs<'tcx>(
+    func: &Function,
+    tcx: TyCtxt<'tcx>,
+    impl_generics: Option<&(clean::Type, clean::Generics)>,
+    cache: &Cache,
+) -> (Vec<RenderType>, Vec<RenderType>) {
+    let decl = &func.decl;
+
+    let combined_generics;
+    let (self_, generics) = if let Some(&(ref impl_self, ref impl_generics)) = impl_generics {
+        match (impl_generics.is_empty(), func.generics.is_empty()) {
+            (true, _) => (Some(impl_self), &func.generics),
+            (_, true) => (Some(impl_self), impl_generics),
+            (false, false) => {
+                let mut params = func.generics.params.clone();
+                params.extend(impl_generics.params.clone());
+                let mut where_predicates = func.generics.where_predicates.clone();
+                where_predicates.extend(impl_generics.where_predicates.clone());
+                combined_generics = clean::Generics { params, where_predicates };
+                (Some(impl_self), &combined_generics)
+            }
+        }
+    } else {
+        (None, &func.generics)
+    };
+
+    let mut all_types = Vec::new();
+    for arg in decl.inputs.values.iter() {
+        let mut args = Vec::new();
+        add_generics_and_bounds_as_types(self_, generics, &arg.type_, tcx, 0, &mut args, cache);
+        if !args.is_empty() {
+            all_types.extend(args);
+        } else {
+            all_types.push(get_index_type(&arg.type_, vec![]));
+        }
+    }
+
+    let mut ret_types = Vec::new();
+    match decl.output {
+        FnRetTy::Return(ref return_type) => {
+            add_generics_and_bounds_as_types(
+                self_,
+                generics,
+                return_type,
+                tcx,
+                0,
+                &mut ret_types,
+                cache,
+            );
+            if ret_types.is_empty() {
+                ret_types.push(get_index_type(return_type, vec![]));
+            }
+        }
+        _ => {}
+    };
+    (all_types, ret_types)
+}
diff --git a/src/librustdoc/html/render/span_map.rs b/src/librustdoc/html/render/span_map.rs
new file mode 100644
index 000000000..34d590fb2
--- /dev/null
+++ b/src/librustdoc/html/render/span_map.rs
@@ -0,0 +1,203 @@
+use crate::clean::{self, PrimitiveType};
+use crate::html::sources;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::{ExprKind, HirId, Mod, Node};
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::hygiene::MacroKind;
+use rustc_span::{BytePos, ExpnKind, Span};
+
+use std::path::{Path, PathBuf};
+
+/// This enum allows us to store two different kinds of information:
+///
+/// In case the `span` definition comes from the same crate, we can simply get the `span` and use
+/// it as is.
+///
+/// Otherwise, we store the definition `DefId` and will generate a link to the documentation page
+/// instead of the source code directly.
+#[derive(Debug)]
+pub(crate) enum LinkFromSrc {
+    Local(clean::Span),
+    External(DefId),
+    Primitive(PrimitiveType),
+}
+
+/// This function will do at most two things:
+///
+/// 1. Generate a `span` correspondance map which links an item `span` to its definition `span`.
+/// 2. Collect the source code files.
+///
+/// It returns the `krate`, the source code files and the `span` correspondance map.
+///
+/// Note about the `span` correspondance map: the keys are actually `(lo, hi)` of `span`s. We don't
+/// need the `span` context later on, only their position, so instead of keep a whole `Span`, we
+/// only keep the `lo` and `hi`.
+pub(crate) fn collect_spans_and_sources(
+    tcx: TyCtxt<'_>,
+    krate: &clean::Crate,
+    src_root: &Path,
+    include_sources: bool,
+    generate_link_to_definition: bool,
+) -> (FxHashMap<PathBuf, String>, FxHashMap<Span, LinkFromSrc>) {
+    let mut visitor = SpanMapVisitor { tcx, matches: FxHashMap::default() };
+
+    if include_sources {
+        if generate_link_to_definition {
+            tcx.hir().walk_toplevel_module(&mut visitor);
+        }
+        let sources = sources::collect_local_sources(tcx, src_root, krate);
+        (sources, visitor.matches)
+    } else {
+        (Default::default(), Default::default())
+    }
+}
+
+struct SpanMapVisitor<'tcx> {
+    pub(crate) tcx: TyCtxt<'tcx>,
+    pub(crate) matches: FxHashMap<Span, LinkFromSrc>,
+}
+
+impl<'tcx> SpanMapVisitor<'tcx> {
+    /// This function is where we handle `hir::Path` elements and add them into the "span map".
+    fn handle_path(&mut self, path: &rustc_hir::Path<'_>) {
+        let info = match path.res {
+            // FIXME: For now, we handle `DefKind` if it's not a `DefKind::TyParam`.
+            // Would be nice to support them too alongside the other `DefKind`
+            // (such as primitive types!).
+            Res::Def(kind, def_id) if kind != DefKind::TyParam => Some(def_id),
+            Res::Local(_) => None,
+            Res::PrimTy(p) => {
+                // FIXME: Doesn't handle "path-like" primitives like arrays or tuples.
+                self.matches.insert(path.span, LinkFromSrc::Primitive(PrimitiveType::from(p)));
+                return;
+            }
+            Res::Err => return,
+            _ => return,
+        };
+        if let Some(span) = self.tcx.hir().res_span(path.res) {
+            self.matches.insert(path.span, LinkFromSrc::Local(clean::Span::new(span)));
+        } else if let Some(def_id) = info {
+            self.matches.insert(path.span, LinkFromSrc::External(def_id));
+        }
+    }
+
+    /// Adds the macro call into the span map. Returns `true` if the `span` was inside a macro
+    /// expansion, whether or not it was added to the span map.
+    ///
+    /// The idea for the macro support is to check if the current `Span` comes from expansion. If
+    /// so, we loop until we find the macro definition by using `outer_expn_data` in a loop.
+    /// Finally, we get the information about the macro itself (`span` if "local", `DefId`
+    /// otherwise) and store it inside the span map.
+    fn handle_macro(&mut self, span: Span) -> bool {
+        if !span.from_expansion() {
+            return false;
+        }
+        // So if the `span` comes from a macro expansion, we need to get the original
+        // macro's `DefId`.
+        let mut data = span.ctxt().outer_expn_data();
+        let mut call_site = data.call_site;
+        // Macros can expand to code containing macros, which will in turn be expanded, etc.
+        // So the idea here is to "go up" until we're back to code that was generated from
+        // macro expansion so that we can get the `DefId` of the original macro that was at the
+        // origin of this expansion.
+        while call_site.from_expansion() {
+            data = call_site.ctxt().outer_expn_data();
+            call_site = data.call_site;
+        }
+
+        let macro_name = match data.kind {
+            ExpnKind::Macro(MacroKind::Bang, macro_name) => macro_name,
+            // Even though we don't handle this kind of macro, this `data` still comes from
+            // expansion so we return `true` so we don't go any deeper in this code.
+            _ => return true,
+        };
+        let link_from_src = match data.macro_def_id {
+            Some(macro_def_id) if macro_def_id.is_local() => {
+                LinkFromSrc::Local(clean::Span::new(data.def_site))
+            }
+            Some(macro_def_id) => LinkFromSrc::External(macro_def_id),
+            None => return true,
+        };
+        let new_span = data.call_site;
+        let macro_name = macro_name.as_str();
+        // The "call_site" includes the whole macro with its "arguments". We only want
+        // the macro name.
+        let new_span = new_span.with_hi(new_span.lo() + BytePos(macro_name.len() as u32));
+        self.matches.insert(new_span, link_from_src);
+        true
+    }
+}
+
+impl<'tcx> Visitor<'tcx> for SpanMapVisitor<'tcx> {
+    type NestedFilter = nested_filter::All;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.tcx.hir()
+    }
+
+    fn visit_path(&mut self, path: &'tcx rustc_hir::Path<'tcx>, _id: HirId) {
+        if self.handle_macro(path.span) {
+            return;
+        }
+        self.handle_path(path);
+        intravisit::walk_path(self, path);
+    }
+
+    fn visit_mod(&mut self, m: &'tcx Mod<'tcx>, span: Span, id: HirId) {
+        // To make the difference between "mod foo {}" and "mod foo;". In case we "import" another
+        // file, we want to link to it. Otherwise no need to create a link.
+        if !span.overlaps(m.spans.inner_span) {
+            // Now that we confirmed it's a file import, we want to get the span for the module
+            // name only and not all the "mod foo;".
+            if let Some(Node::Item(item)) = self.tcx.hir().find(id) {
+                self.matches.insert(
+                    item.ident.span,
+                    LinkFromSrc::Local(clean::Span::new(m.spans.inner_span)),
+                );
+            }
+        }
+        intravisit::walk_mod(self, m, id);
+    }
+
+    fn visit_expr(&mut self, expr: &'tcx rustc_hir::Expr<'tcx>) {
+        if let ExprKind::MethodCall(segment, ..) = expr.kind {
+            if let Some(hir_id) = segment.hir_id {
+                let hir = self.tcx.hir();
+                let body_id = hir.enclosing_body_owner(hir_id);
+                // FIXME: this is showing error messages for parts of the code that are not
+                // compiled (because of cfg)!
+                //
+                // See discussion in https://github.com/rust-lang/rust/issues/69426#issuecomment-1019412352
+                let typeck_results = self.tcx.typeck_body(
+                    hir.maybe_body_owned_by(body_id).expect("a body which isn't a body"),
+                );
+                if let Some(def_id) = typeck_results.type_dependent_def_id(expr.hir_id) {
+                    self.matches.insert(
+                        segment.ident.span,
+                        match hir.span_if_local(def_id) {
+                            Some(span) => LinkFromSrc::Local(clean::Span::new(span)),
+                            None => LinkFromSrc::External(def_id),
+                        },
+                    );
+                }
+            }
+        } else if self.handle_macro(expr.span) {
+            // We don't want to go deeper into the macro.
+            return;
+        }
+        intravisit::walk_expr(self, expr);
+    }
+
+    fn visit_use(&mut self, path: &'tcx rustc_hir::Path<'tcx>, id: HirId) {
+        if self.handle_macro(path.span) {
+            return;
+        }
+        self.handle_path(path);
+        intravisit::walk_use(self, path, id);
+    }
+}
diff --git a/src/librustdoc/html/render/tests.rs b/src/librustdoc/html/render/tests.rs
new file mode 100644
index 000000000..3175fbe56
--- /dev/null
+++ b/src/librustdoc/html/render/tests.rs
@@ -0,0 +1,54 @@
+use std::cmp::Ordering;
+
+use super::print_item::compare_names;
+use super::{AllTypes, Buffer};
+
+#[test]
+fn test_compare_names() {
+    for &(a, b) in &[
+        ("hello", "world"),
+        ("", "world"),
+        ("123", "hello"),
+        ("123", ""),
+        ("123test", "123"),
+        ("hello", ""),
+        ("hello", "hello"),
+        ("hello123", "hello123"),
+        ("hello123", "hello12"),
+        ("hello12", "hello123"),
+        ("hello01abc", "hello01xyz"),
+        ("hello0abc", "hello0"),
+        ("hello0", "hello0abc"),
+        ("01", "1"),
+    ] {
+        assert_eq!(compare_names(a, b), a.cmp(b), "{:?} - {:?}", a, b);
+    }
+    assert_eq!(compare_names("u8", "u16"), Ordering::Less);
+    assert_eq!(compare_names("u32", "u16"), Ordering::Greater);
+    assert_eq!(compare_names("u8_to_f64", "u16_to_f64"), Ordering::Less);
+    assert_eq!(compare_names("u32_to_f64", "u16_to_f64"), Ordering::Greater);
+    assert_eq!(compare_names("u16_to_f64", "u16_to_f64"), Ordering::Equal);
+    assert_eq!(compare_names("u16_to_f32", "u16_to_f64"), Ordering::Less);
+}
+
+#[test]
+fn test_name_sorting() {
+    let names = [
+        "Apple", "Banana", "Fruit", "Fruit0", "Fruit00", "Fruit01", "Fruit1", "Fruit02", "Fruit2",
+        "Fruit20", "Fruit30x", "Fruit100", "Pear",
+    ];
+    let mut sorted = names.to_owned();
+    sorted.sort_by(|&l, r| compare_names(l, r));
+    assert_eq!(names, sorted);
+}
+
+#[test]
+fn test_all_types_prints_header_once() {
+    // Regression test for #82477
+    let all_types = AllTypes::new();
+
+    let mut buffer = Buffer::new();
+    all_types.print(&mut buffer);
+
+    assert_eq!(1, buffer.into_inner().matches("List of all items").count());
+}
diff --git a/src/librustdoc/html/render/write_shared.rs b/src/librustdoc/html/render/write_shared.rs
new file mode 100644
index 000000000..6fb41ff32
--- /dev/null
+++ b/src/librustdoc/html/render/write_shared.rs
@@ -0,0 +1,600 @@
+use std::ffi::OsStr;
+use std::fmt::Write;
+use std::fs::{self, File};
+use std::io::prelude::*;
+use std::io::{self, BufReader};
+use std::path::{Component, Path, PathBuf};
+use std::rc::Rc;
+use std::sync::LazyLock as Lazy;
+
+use itertools::Itertools;
+use rustc_data_structures::flock;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use serde::Serialize;
+
+use super::{collect_paths_for_type, ensure_trailing_slash, Context, BASIC_KEYWORDS};
+use crate::clean::Crate;
+use crate::config::{EmitType, RenderOptions};
+use crate::docfs::PathError;
+use crate::error::Error;
+use crate::html::{layout, static_files};
+use crate::{try_err, try_none};
+
+static FILES_UNVERSIONED: Lazy<FxHashMap<&str, &[u8]>> = Lazy::new(|| {
+    map! {
+        "FiraSans-Regular.woff2" => static_files::fira_sans::REGULAR,
+        "FiraSans-Medium.woff2" => static_files::fira_sans::MEDIUM,
+        "FiraSans-LICENSE.txt" => static_files::fira_sans::LICENSE,
+        "SourceSerif4-Regular.ttf.woff2" => static_files::source_serif_4::REGULAR,
+        "SourceSerif4-Bold.ttf.woff2" => static_files::source_serif_4::BOLD,
+        "SourceSerif4-It.ttf.woff2" => static_files::source_serif_4::ITALIC,
+        "SourceSerif4-LICENSE.md" => static_files::source_serif_4::LICENSE,
+        "SourceCodePro-Regular.ttf.woff2" => static_files::source_code_pro::REGULAR,
+        "SourceCodePro-Semibold.ttf.woff2" => static_files::source_code_pro::SEMIBOLD,
+        "SourceCodePro-It.ttf.woff2" => static_files::source_code_pro::ITALIC,
+        "SourceCodePro-LICENSE.txt" => static_files::source_code_pro::LICENSE,
+        "NanumBarunGothic.ttf.woff2" => static_files::nanum_barun_gothic::REGULAR,
+        "NanumBarunGothic-LICENSE.txt" => static_files::nanum_barun_gothic::LICENSE,
+        "LICENSE-MIT.txt" => static_files::LICENSE_MIT,
+        "LICENSE-APACHE.txt" => static_files::LICENSE_APACHE,
+        "COPYRIGHT.txt" => static_files::COPYRIGHT,
+    }
+});
+
+enum SharedResource<'a> {
+    /// This file will never change, no matter what toolchain is used to build it.
+    ///
+    /// It does not have a resource suffix.
+    Unversioned { name: &'static str },
+    /// This file may change depending on the toolchain.
+    ///
+    /// It has a resource suffix.
+    ToolchainSpecific { basename: &'static str },
+    /// This file may change for any crate within a build, or based on the CLI arguments.
+    ///
+    /// This differs from normal invocation-specific files because it has a resource suffix.
+    InvocationSpecific { basename: &'a str },
+}
+
+impl SharedResource<'_> {
+    fn extension(&self) -> Option<&OsStr> {
+        use SharedResource::*;
+        match self {
+            Unversioned { name }
+            | ToolchainSpecific { basename: name }
+            | InvocationSpecific { basename: name } => Path::new(name).extension(),
+        }
+    }
+
+    fn path(&self, cx: &Context<'_>) -> PathBuf {
+        match self {
+            SharedResource::Unversioned { name } => cx.dst.join(name),
+            SharedResource::ToolchainSpecific { basename } => cx.suffix_path(basename),
+            SharedResource::InvocationSpecific { basename } => cx.suffix_path(basename),
+        }
+    }
+
+    fn should_emit(&self, emit: &[EmitType]) -> bool {
+        if emit.is_empty() {
+            return true;
+        }
+        let kind = match self {
+            SharedResource::Unversioned { .. } => EmitType::Unversioned,
+            SharedResource::ToolchainSpecific { .. } => EmitType::Toolchain,
+            SharedResource::InvocationSpecific { .. } => EmitType::InvocationSpecific,
+        };
+        emit.contains(&kind)
+    }
+}
+
+impl Context<'_> {
+    fn suffix_path(&self, filename: &str) -> PathBuf {
+        // We use splitn vs Path::extension here because we might get a filename
+        // like `style.min.css` and we want to process that into
+        // `style-suffix.min.css`.  Path::extension would just return `css`
+        // which would result in `style.min-suffix.css` which isn't what we
+        // want.
+        let (base, ext) = filename.split_once('.').unwrap();
+        let filename = format!("{}{}.{}", base, self.shared.resource_suffix, ext);
+        self.dst.join(&filename)
+    }
+
+    fn write_shared(
+        &self,
+        resource: SharedResource<'_>,
+        contents: impl 'static + Send + AsRef<[u8]>,
+        emit: &[EmitType],
+    ) -> Result<(), Error> {
+        if resource.should_emit(emit) {
+            self.shared.fs.write(resource.path(self), contents)
+        } else {
+            Ok(())
+        }
+    }
+
+    fn write_minify(
+        &self,
+        resource: SharedResource<'_>,
+        contents: impl 'static + Send + AsRef<str> + AsRef<[u8]>,
+        minify: bool,
+        emit: &[EmitType],
+    ) -> Result<(), Error> {
+        if minify {
+            let contents = contents.as_ref();
+            let contents = if resource.extension() == Some(OsStr::new("css")) {
+                minifier::css::minify(contents)
+                    .map_err(|e| {
+                        Error::new(format!("failed to minify CSS file: {}", e), resource.path(self))
+                    })?
+                    .to_string()
+            } else {
+                minifier::js::minify(contents).to_string()
+            };
+            self.write_shared(resource, contents, emit)
+        } else {
+            self.write_shared(resource, contents, emit)
+        }
+    }
+}
+
+pub(super) fn write_shared(
+    cx: &mut Context<'_>,
+    krate: &Crate,
+    search_index: String,
+    options: &RenderOptions,
+) -> Result<(), Error> {
+    // Write out the shared files. Note that these are shared among all rustdoc
+    // docs placed in the output directory, so this needs to be a synchronized
+    // operation with respect to all other rustdocs running around.
+    let lock_file = cx.dst.join(".lock");
+    let _lock = try_err!(flock::Lock::new(&lock_file, true, true, true), &lock_file);
+
+    // Minified resources are usually toolchain resources. If they're not, they should use `cx.write_minify` directly.
+    fn write_minify(
+        basename: &'static str,
+        contents: impl 'static + Send + AsRef<str> + AsRef<[u8]>,
+        cx: &Context<'_>,
+        options: &RenderOptions,
+    ) -> Result<(), Error> {
+        cx.write_minify(
+            SharedResource::ToolchainSpecific { basename },
+            contents,
+            options.enable_minification,
+            &options.emit,
+        )
+    }
+
+    // Toolchain resources should never be dynamic.
+    let write_toolchain = |p: &'static _, c: &'static _| {
+        cx.write_shared(SharedResource::ToolchainSpecific { basename: p }, c, &options.emit)
+    };
+
+    // Crate resources should always be dynamic.
+    let write_crate = |p: &_, make_content: &dyn Fn() -> Result<Vec<u8>, Error>| {
+        let content = make_content()?;
+        cx.write_shared(SharedResource::InvocationSpecific { basename: p }, content, &options.emit)
+    };
+
+    // Given "foo.svg", return e.g. "url(\"foo1.58.0.svg\")"
+    fn ver_url(cx: &Context<'_>, basename: &'static str) -> String {
+        format!(
+            "url(\"{}\")",
+            SharedResource::ToolchainSpecific { basename }
+                .path(cx)
+                .file_name()
+                .unwrap()
+                .to_str()
+                .unwrap()
+        )
+    }
+
+    // We use the AUTOREPLACE mechanism to inject into our static JS and CSS certain
+    // values that are only known at doc build time. Since this mechanism is somewhat
+    // surprising when reading the code, please limit it to rustdoc.css.
+    write_minify(
+        "rustdoc.css",
+        static_files::RUSTDOC_CSS
+            .replace(
+                "/* AUTOREPLACE: */url(\"toggle-minus.svg\")",
+                &ver_url(cx, "toggle-minus.svg"),
+            )
+            .replace("/* AUTOREPLACE: */url(\"toggle-plus.svg\")", &ver_url(cx, "toggle-plus.svg"))
+            .replace("/* AUTOREPLACE: */url(\"down-arrow.svg\")", &ver_url(cx, "down-arrow.svg")),
+        cx,
+        options,
+    )?;
+
+    // Add all the static files. These may already exist, but we just
+    // overwrite them anyway to make sure that they're fresh and up-to-date.
+    write_minify("settings.css", static_files::SETTINGS_CSS, cx, options)?;
+    write_minify("noscript.css", static_files::NOSCRIPT_CSS, cx, options)?;
+
+    // To avoid "light.css" to be overwritten, we'll first run over the received themes and only
+    // then we'll run over the "official" styles.
+    let mut themes: FxHashSet<String> = FxHashSet::default();
+
+    for entry in &cx.shared.style_files {
+        let theme = entry.basename()?;
+        let extension =
+            try_none!(try_none!(entry.path.extension(), &entry.path).to_str(), &entry.path);
+
+        // Handle the official themes
+        match theme.as_str() {
+            "light" => write_minify("light.css", static_files::themes::LIGHT, cx, options)?,
+            "dark" => write_minify("dark.css", static_files::themes::DARK, cx, options)?,
+            "ayu" => write_minify("ayu.css", static_files::themes::AYU, cx, options)?,
+            _ => {
+                // Handle added third-party themes
+                let filename = format!("{}.{}", theme, extension);
+                write_crate(&filename, &|| Ok(try_err!(fs::read(&entry.path), &entry.path)))?;
+            }
+        };
+
+        themes.insert(theme.to_owned());
+    }
+
+    if (*cx.shared).layout.logo.is_empty() {
+        write_toolchain("rust-logo.svg", static_files::RUST_LOGO_SVG)?;
+    }
+    if (*cx.shared).layout.favicon.is_empty() {
+        write_toolchain("favicon.svg", static_files::RUST_FAVICON_SVG)?;
+        write_toolchain("favicon-16x16.png", static_files::RUST_FAVICON_PNG_16)?;
+        write_toolchain("favicon-32x32.png", static_files::RUST_FAVICON_PNG_32)?;
+    }
+    write_toolchain("wheel.svg", static_files::WHEEL_SVG)?;
+    write_toolchain("clipboard.svg", static_files::CLIPBOARD_SVG)?;
+    write_toolchain("down-arrow.svg", static_files::DOWN_ARROW_SVG)?;
+    write_toolchain("toggle-minus.svg", static_files::TOGGLE_MINUS_PNG)?;
+    write_toolchain("toggle-plus.svg", static_files::TOGGLE_PLUS_PNG)?;
+
+    let mut themes: Vec<&String> = themes.iter().collect();
+    themes.sort();
+
+    write_minify("main.js", static_files::MAIN_JS, cx, options)?;
+    write_minify("search.js", static_files::SEARCH_JS, cx, options)?;
+    write_minify("settings.js", static_files::SETTINGS_JS, cx, options)?;
+
+    if cx.include_sources {
+        write_minify("source-script.js", static_files::sidebar::SOURCE_SCRIPT, cx, options)?;
+    }
+
+    write_minify("storage.js", static_files::STORAGE_JS, cx, options)?;
+
+    if cx.shared.layout.scrape_examples_extension {
+        cx.write_minify(
+            SharedResource::InvocationSpecific { basename: "scrape-examples.js" },
+            static_files::SCRAPE_EXAMPLES_JS,
+            options.enable_minification,
+            &options.emit,
+        )?;
+    }
+
+    if let Some(ref css) = cx.shared.layout.css_file_extension {
+        let buffer = try_err!(fs::read_to_string(css), css);
+        // This varies based on the invocation, so it can't go through the write_minify wrapper.
+        cx.write_minify(
+            SharedResource::InvocationSpecific { basename: "theme.css" },
+            buffer,
+            options.enable_minification,
+            &options.emit,
+        )?;
+    }
+    write_minify("normalize.css", static_files::NORMALIZE_CSS, cx, options)?;
+    for (name, contents) in &*FILES_UNVERSIONED {
+        cx.write_shared(SharedResource::Unversioned { name }, contents, &options.emit)?;
+    }
+
+    fn collect(path: &Path, krate: &str, key: &str) -> io::Result<(Vec<String>, Vec<String>)> {
+        let mut ret = Vec::new();
+        let mut krates = Vec::new();
+
+        if path.exists() {
+            let prefix = format!(r#"{}["{}"]"#, key, krate);
+            for line in BufReader::new(File::open(path)?).lines() {
+                let line = line?;
+                if !line.starts_with(key) {
+                    continue;
+                }
+                if line.starts_with(&prefix) {
+                    continue;
+                }
+                ret.push(line.to_string());
+                krates.push(
+                    line[key.len() + 2..]
+                        .split('"')
+                        .next()
+                        .map(|s| s.to_owned())
+                        .unwrap_or_else(String::new),
+                );
+            }
+        }
+        Ok((ret, krates))
+    }
+
+    fn collect_json(path: &Path, krate: &str) -> io::Result<(Vec<String>, Vec<String>)> {
+        let mut ret = Vec::new();
+        let mut krates = Vec::new();
+
+        if path.exists() {
+            let prefix = format!("\"{}\"", krate);
+            for line in BufReader::new(File::open(path)?).lines() {
+                let line = line?;
+                if !line.starts_with('"') {
+                    continue;
+                }
+                if line.starts_with(&prefix) {
+                    continue;
+                }
+                if line.ends_with(",\\") {
+                    ret.push(line[..line.len() - 2].to_string());
+                } else {
+                    // Ends with "\\" (it's the case for the last added crate line)
+                    ret.push(line[..line.len() - 1].to_string());
+                }
+                krates.push(
+                    line.split('"')
+                        .find(|s| !s.is_empty())
+                        .map(|s| s.to_owned())
+                        .unwrap_or_else(String::new),
+                );
+            }
+        }
+        Ok((ret, krates))
+    }
+
+    use std::ffi::OsString;
+
+    #[derive(Debug)]
+    struct Hierarchy {
+        elem: OsString,
+        children: FxHashMap<OsString, Hierarchy>,
+        elems: FxHashSet<OsString>,
+    }
+
+    impl Hierarchy {
+        fn new(elem: OsString) -> Hierarchy {
+            Hierarchy { elem, children: FxHashMap::default(), elems: FxHashSet::default() }
+        }
+
+        fn to_json_string(&self) -> String {
+            let mut subs: Vec<&Hierarchy> = self.children.values().collect();
+            subs.sort_unstable_by(|a, b| a.elem.cmp(&b.elem));
+            let mut files = self
+                .elems
+                .iter()
+                .map(|s| format!("\"{}\"", s.to_str().expect("invalid osstring conversion")))
+                .collect::<Vec<_>>();
+            files.sort_unstable();
+            let subs = subs.iter().map(|s| s.to_json_string()).collect::<Vec<_>>().join(",");
+            let dirs = if subs.is_empty() && files.is_empty() {
+                String::new()
+            } else {
+                format!(",[{}]", subs)
+            };
+            let files = files.join(",");
+            let files = if files.is_empty() { String::new() } else { format!(",[{}]", files) };
+            format!(
+                "[\"{name}\"{dirs}{files}]",
+                name = self.elem.to_str().expect("invalid osstring conversion"),
+                dirs = dirs,
+                files = files
+            )
+        }
+    }
+
+    if cx.include_sources {
+        let mut hierarchy = Hierarchy::new(OsString::new());
+        for source in cx
+            .shared
+            .local_sources
+            .iter()
+            .filter_map(|p| p.0.strip_prefix(&cx.shared.src_root).ok())
+        {
+            let mut h = &mut hierarchy;
+            let mut elems = source
+                .components()
+                .filter_map(|s| match s {
+                    Component::Normal(s) => Some(s.to_owned()),
+                    _ => None,
+                })
+                .peekable();
+            loop {
+                let cur_elem = elems.next().expect("empty file path");
+                if elems.peek().is_none() {
+                    h.elems.insert(cur_elem);
+                    break;
+                } else {
+                    let e = cur_elem.clone();
+                    h = h.children.entry(cur_elem.clone()).or_insert_with(|| Hierarchy::new(e));
+                }
+            }
+        }
+
+        let dst = cx.dst.join(&format!("source-files{}.js", cx.shared.resource_suffix));
+        let make_sources = || {
+            let (mut all_sources, _krates) =
+                try_err!(collect_json(&dst, krate.name(cx.tcx()).as_str()), &dst);
+            all_sources.push(format!(
+                r#""{}":{}"#,
+                &krate.name(cx.tcx()),
+                hierarchy
+                    .to_json_string()
+                    // All these `replace` calls are because we have to go through JS string for JSON content.
+                    .replace('\\', r"\\")
+                    .replace('\'', r"\'")
+                    // We need to escape double quotes for the JSON.
+                    .replace("\\\"", "\\\\\"")
+            ));
+            all_sources.sort();
+            let mut v = String::from("var sourcesIndex = JSON.parse('{\\\n");
+            v.push_str(&all_sources.join(",\\\n"));
+            v.push_str("\\\n}');\ncreateSourceSidebar();\n");
+            Ok(v.into_bytes())
+        };
+        write_crate("source-files.js", &make_sources)?;
+    }
+
+    // Update the search index and crate list.
+    let dst = cx.dst.join(&format!("search-index{}.js", cx.shared.resource_suffix));
+    let (mut all_indexes, mut krates) =
+        try_err!(collect_json(&dst, krate.name(cx.tcx()).as_str()), &dst);
+    all_indexes.push(search_index);
+    krates.push(krate.name(cx.tcx()).to_string());
+    krates.sort();
+
+    // Sort the indexes by crate so the file will be generated identically even
+    // with rustdoc running in parallel.
+    all_indexes.sort();
+    write_crate("search-index.js", &|| {
+        let mut v = String::from("var searchIndex = JSON.parse('{\\\n");
+        v.push_str(&all_indexes.join(",\\\n"));
+        v.push_str(
+            r#"\
+}');
+if (typeof window !== 'undefined' && window.initSearch) {window.initSearch(searchIndex)};
+if (typeof exports !== 'undefined') {exports.searchIndex = searchIndex};
+"#,
+        );
+        Ok(v.into_bytes())
+    })?;
+
+    write_crate("crates.js", &|| {
+        let krates = krates.iter().map(|k| format!("\"{}\"", k)).join(",");
+        Ok(format!("window.ALL_CRATES = [{}];", krates).into_bytes())
+    })?;
+
+    if options.enable_index_page {
+        if let Some(index_page) = options.index_page.clone() {
+            let mut md_opts = options.clone();
+            md_opts.output = cx.dst.clone();
+            md_opts.external_html = (*cx.shared).layout.external_html.clone();
+
+            crate::markdown::render(&index_page, md_opts, cx.shared.edition())
+                .map_err(|e| Error::new(e, &index_page))?;
+        } else {
+            let shared = Rc::clone(&cx.shared);
+            let dst = cx.dst.join("index.html");
+            let page = layout::Page {
+                title: "Index of crates",
+                css_class: "mod",
+                root_path: "./",
+                static_root_path: shared.static_root_path.as_deref(),
+                description: "List of crates",
+                keywords: BASIC_KEYWORDS,
+                resource_suffix: &shared.resource_suffix,
+            };
+
+            let content = format!(
+                "<h1 class=\"fqn\">\
+                     <span class=\"in-band\">List of all crates</span>\
+                </h1><ul class=\"crate mod\">{}</ul>",
+                krates
+                    .iter()
+                    .map(|s| {
+                        format!(
+                            "<li><a class=\"crate mod\" href=\"{}index.html\">{}</a></li>",
+                            ensure_trailing_slash(s),
+                            s
+                        )
+                    })
+                    .collect::<String>()
+            );
+            let v = layout::render(&shared.layout, &page, "", content, &shared.style_files);
+            shared.fs.write(dst, v)?;
+        }
+    }
+
+    // Update the list of all implementors for traits
+    let dst = cx.dst.join("implementors");
+    let cache = cx.cache();
+    for (&did, imps) in &cache.implementors {
+        // Private modules can leak through to this phase of rustdoc, which
+        // could contain implementations for otherwise private types. In some
+        // rare cases we could find an implementation for an item which wasn't
+        // indexed, so we just skip this step in that case.
+        //
+        // FIXME: this is a vague explanation for why this can't be a `get`, in
+        //        theory it should be...
+        let (remote_path, remote_item_type) = match cache.exact_paths.get(&did) {
+            Some(p) => match cache.paths.get(&did).or_else(|| cache.external_paths.get(&did)) {
+                Some((_, t)) => (p, t),
+                None => continue,
+            },
+            None => match cache.external_paths.get(&did) {
+                Some((p, t)) => (p, t),
+                None => continue,
+            },
+        };
+
+        #[derive(Serialize)]
+        struct Implementor {
+            text: String,
+            synthetic: bool,
+            types: Vec<String>,
+        }
+
+        let implementors = imps
+            .iter()
+            .filter_map(|imp| {
+                // If the trait and implementation are in the same crate, then
+                // there's no need to emit information about it (there's inlining
+                // going on). If they're in different crates then the crate defining
+                // the trait will be interested in our implementation.
+                //
+                // If the implementation is from another crate then that crate
+                // should add it.
+                if imp.impl_item.item_id.krate() == did.krate || !imp.impl_item.item_id.is_local() {
+                    None
+                } else {
+                    Some(Implementor {
+                        text: imp.inner_impl().print(false, cx).to_string(),
+                        synthetic: imp.inner_impl().kind.is_auto(),
+                        types: collect_paths_for_type(imp.inner_impl().for_.clone(), cache),
+                    })
+                }
+            })
+            .collect::<Vec<_>>();
+
+        // Only create a js file if we have impls to add to it. If the trait is
+        // documented locally though we always create the file to avoid dead
+        // links.
+        if implementors.is_empty() && !cache.paths.contains_key(&did) {
+            continue;
+        }
+
+        let implementors = format!(
+            r#"implementors["{}"] = {};"#,
+            krate.name(cx.tcx()),
+            serde_json::to_string(&implementors).unwrap()
+        );
+
+        let mut mydst = dst.clone();
+        for part in &remote_path[..remote_path.len() - 1] {
+            mydst.push(part.to_string());
+        }
+        cx.shared.ensure_dir(&mydst)?;
+        mydst.push(&format!("{}.{}.js", remote_item_type, remote_path[remote_path.len() - 1]));
+
+        let (mut all_implementors, _) =
+            try_err!(collect(&mydst, krate.name(cx.tcx()).as_str(), "implementors"), &mydst);
+        all_implementors.push(implementors);
+        // Sort the implementors by crate so the file will be generated
+        // identically even with rustdoc running in parallel.
+        all_implementors.sort();
+
+        let mut v = String::from("(function() {var implementors = {};\n");
+        for implementor in &all_implementors {
+            writeln!(v, "{}", *implementor).unwrap();
+        }
+        v.push_str(
+            "if (window.register_implementors) {\
+                 window.register_implementors(implementors);\
+             } else {\
+                 window.pending_implementors = implementors;\
+             }",
+        );
+        v.push_str("})()");
+        cx.shared.fs.write(mydst, v)?;
+    }
+    Ok(())
+}
diff --git a/src/librustdoc/html/sources.rs b/src/librustdoc/html/sources.rs
new file mode 100644
index 000000000..d0fd637ba
--- /dev/null
+++ b/src/librustdoc/html/sources.rs
@@ -0,0 +1,303 @@
+use crate::clean;
+use crate::docfs::PathError;
+use crate::error::Error;
+use crate::html::format::Buffer;
+use crate::html::highlight;
+use crate::html::layout;
+use crate::html::render::{Context, BASIC_KEYWORDS};
+use crate::visit::DocVisitor;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::Session;
+use rustc_span::edition::Edition;
+use rustc_span::source_map::FileName;
+
+use std::ffi::OsStr;
+use std::fs;
+use std::path::{Component, Path, PathBuf};
+use std::rc::Rc;
+
+pub(crate) fn render(cx: &mut Context<'_>, krate: &clean::Crate) -> Result<(), Error> {
+    info!("emitting source files");
+
+    let dst = cx.dst.join("src").join(krate.name(cx.tcx()).as_str());
+    cx.shared.ensure_dir(&dst)?;
+
+    let mut collector = SourceCollector { dst, cx, emitted_local_sources: FxHashSet::default() };
+    collector.visit_crate(krate);
+    Ok(())
+}
+
+pub(crate) fn collect_local_sources<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    src_root: &Path,
+    krate: &clean::Crate,
+) -> FxHashMap<PathBuf, String> {
+    let mut lsc = LocalSourcesCollector { tcx, local_sources: FxHashMap::default(), src_root };
+    lsc.visit_crate(krate);
+    lsc.local_sources
+}
+
+struct LocalSourcesCollector<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    local_sources: FxHashMap<PathBuf, String>,
+    src_root: &'a Path,
+}
+
+fn is_real_and_local(span: clean::Span, sess: &Session) -> bool {
+    span.cnum(sess) == LOCAL_CRATE && span.filename(sess).is_real()
+}
+
+impl LocalSourcesCollector<'_, '_> {
+    fn add_local_source(&mut self, item: &clean::Item) {
+        let sess = self.tcx.sess;
+        let span = item.span(self.tcx);
+        // skip all synthetic "files"
+        if !is_real_and_local(span, sess) {
+            return;
+        }
+        let filename = span.filename(sess);
+        let p = if let FileName::Real(file) = filename {
+            match file.into_local_path() {
+                Some(p) => p,
+                None => return,
+            }
+        } else {
+            return;
+        };
+        if self.local_sources.contains_key(&*p) {
+            // We've already emitted this source
+            return;
+        }
+
+        let mut href = String::new();
+        clean_path(self.src_root, &p, false, |component| {
+            href.push_str(&component.to_string_lossy());
+            href.push('/');
+        });
+
+        let mut src_fname = p.file_name().expect("source has no filename").to_os_string();
+        src_fname.push(".html");
+        href.push_str(&src_fname.to_string_lossy());
+        self.local_sources.insert(p, href);
+    }
+}
+
+impl DocVisitor for LocalSourcesCollector<'_, '_> {
+    fn visit_item(&mut self, item: &clean::Item) {
+        self.add_local_source(item);
+
+        self.visit_item_recur(item)
+    }
+}
+
+/// Helper struct to render all source code to HTML pages
+struct SourceCollector<'a, 'tcx> {
+    cx: &'a mut Context<'tcx>,
+
+    /// Root destination to place all HTML output into
+    dst: PathBuf,
+    emitted_local_sources: FxHashSet<PathBuf>,
+}
+
+impl DocVisitor for SourceCollector<'_, '_> {
+    fn visit_item(&mut self, item: &clean::Item) {
+        if !self.cx.include_sources {
+            return;
+        }
+
+        let tcx = self.cx.tcx();
+        let span = item.span(tcx);
+        let sess = tcx.sess;
+
+        // If we're not rendering sources, there's nothing to do.
+        // If we're including source files, and we haven't seen this file yet,
+        // then we need to render it out to the filesystem.
+        if is_real_and_local(span, sess) {
+            let filename = span.filename(sess);
+            let span = span.inner();
+            let pos = sess.source_map().lookup_source_file(span.lo());
+            let file_span = span.with_lo(pos.start_pos).with_hi(pos.end_pos);
+            // If it turns out that we couldn't read this file, then we probably
+            // can't read any of the files (generating html output from json or
+            // something like that), so just don't include sources for the
+            // entire crate. The other option is maintaining this mapping on a
+            // per-file basis, but that's probably not worth it...
+            self.cx.include_sources = match self.emit_source(&filename, file_span) {
+                Ok(()) => true,
+                Err(e) => {
+                    self.cx.shared.tcx.sess.span_err(
+                        span,
+                        &format!(
+                            "failed to render source code for `{}`: {}",
+                            filename.prefer_local(),
+                            e,
+                        ),
+                    );
+                    false
+                }
+            };
+        }
+
+        self.visit_item_recur(item)
+    }
+}
+
+impl SourceCollector<'_, '_> {
+    /// Renders the given filename into its corresponding HTML source file.
+    fn emit_source(
+        &mut self,
+        filename: &FileName,
+        file_span: rustc_span::Span,
+    ) -> Result<(), Error> {
+        let p = match *filename {
+            FileName::Real(ref file) => {
+                if let Some(local_path) = file.local_path() {
+                    local_path.to_path_buf()
+                } else {
+                    unreachable!("only the current crate should have sources emitted");
+                }
+            }
+            _ => return Ok(()),
+        };
+        if self.emitted_local_sources.contains(&*p) {
+            // We've already emitted this source
+            return Ok(());
+        }
+
+        let contents = match fs::read_to_string(&p) {
+            Ok(contents) => contents,
+            Err(e) => {
+                return Err(Error::new(e, &p));
+            }
+        };
+
+        // Remove the utf-8 BOM if any
+        let contents = contents.strip_prefix('\u{feff}').unwrap_or(&contents);
+
+        let shared = Rc::clone(&self.cx.shared);
+        // Create the intermediate directories
+        let mut cur = self.dst.clone();
+        let mut root_path = String::from("../../");
+        clean_path(&shared.src_root, &p, false, |component| {
+            cur.push(component);
+            root_path.push_str("../");
+        });
+
+        shared.ensure_dir(&cur)?;
+
+        let src_fname = p.file_name().expect("source has no filename").to_os_string();
+        let mut fname = src_fname.clone();
+        fname.push(".html");
+        cur.push(&fname);
+
+        let title = format!("{} - source", src_fname.to_string_lossy());
+        let desc = format!("Source of the Rust file `{}`.", filename.prefer_remapped());
+        let page = layout::Page {
+            title: &title,
+            css_class: "source",
+            root_path: &root_path,
+            static_root_path: shared.static_root_path.as_deref(),
+            description: &desc,
+            keywords: BASIC_KEYWORDS,
+            resource_suffix: &shared.resource_suffix,
+        };
+        let v = layout::render(
+            &shared.layout,
+            &page,
+            "",
+            |buf: &mut _| {
+                let cx = &mut self.cx;
+                print_src(
+                    buf,
+                    contents,
+                    cx.shared.edition(),
+                    file_span,
+                    cx,
+                    &root_path,
+                    None,
+                    SourceContext::Standalone,
+                )
+            },
+            &shared.style_files,
+        );
+        shared.fs.write(cur, v)?;
+        self.emitted_local_sources.insert(p);
+        Ok(())
+    }
+}
+
+/// Takes a path to a source file and cleans the path to it. This canonicalizes
+/// things like ".." to components which preserve the "top down" hierarchy of a
+/// static HTML tree. Each component in the cleaned path will be passed as an
+/// argument to `f`. The very last component of the path (ie the file name) will
+/// be passed to `f` if `keep_filename` is true, and ignored otherwise.
+pub(crate) fn clean_path<F>(src_root: &Path, p: &Path, keep_filename: bool, mut f: F)
+where
+    F: FnMut(&OsStr),
+{
+    // make it relative, if possible
+    let p = p.strip_prefix(src_root).unwrap_or(p);
+
+    let mut iter = p.components().peekable();
+
+    while let Some(c) = iter.next() {
+        if !keep_filename && iter.peek().is_none() {
+            break;
+        }
+
+        match c {
+            Component::ParentDir => f("up".as_ref()),
+            Component::Normal(c) => f(c),
+            _ => continue,
+        }
+    }
+}
+
+pub(crate) enum SourceContext {
+    Standalone,
+    Embedded { offset: usize },
+}
+
+/// Wrapper struct to render the source code of a file. This will do things like
+/// adding line numbers to the left-hand side.
+pub(crate) fn print_src(
+    buf: &mut Buffer,
+    s: &str,
+    edition: Edition,
+    file_span: rustc_span::Span,
+    context: &Context<'_>,
+    root_path: &str,
+    decoration_info: Option<highlight::DecorationInfo>,
+    source_context: SourceContext,
+) {
+    let lines = s.lines().count();
+    let mut line_numbers = Buffer::empty_from(buf);
+    line_numbers.write_str("<pre class=\"line-numbers\">");
+    match source_context {
+        SourceContext::Standalone => {
+            for line in 1..=lines {
+                writeln!(line_numbers, "<span id=\"{0}\">{0}</span>", line)
+            }
+        }
+        SourceContext::Embedded { offset } => {
+            for line in 1..=lines {
+                writeln!(line_numbers, "<span>{0}</span>", line + offset)
+            }
+        }
+    }
+    line_numbers.write_str("</pre>");
+    highlight::render_with_highlighting(
+        s,
+        buf,
+        None,
+        None,
+        None,
+        edition,
+        Some(line_numbers),
+        Some(highlight::HrefContext { context, file_span, root_path }),
+        decoration_info,
+    );
+}
diff --git a/src/librustdoc/html/static/.eslintrc.js b/src/librustdoc/html/static/.eslintrc.js
new file mode 100644
index 000000000..fcd925bb3
--- /dev/null
+++ b/src/librustdoc/html/static/.eslintrc.js
@@ -0,0 +1,96 @@
+module.exports = {
+    "env": {
+        "browser": true,
+        "es6": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+        "ecmaVersion": 2015,
+        "sourceType": "module"
+    },
+    "rules": {
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ],
+        "quotes": [
+            "error",
+            "double"
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "no-trailing-spaces": "error",
+        "no-var": ["error"],
+        "prefer-const": ["error"],
+        "prefer-arrow-callback": ["error"],
+        "brace-style": [
+            "error",
+            "1tbs",
+            { "allowSingleLine": false }
+        ],
+        "keyword-spacing": [
+            "error",
+            { "before": true, "after": true }
+        ],
+        "arrow-spacing": [
+            "error",
+            { "before": true, "after": true }
+        ],
+        "key-spacing": [
+            "error",
+            { "beforeColon": false, "afterColon": true, "mode": "strict" }
+        ],
+        "func-call-spacing": ["error", "never"],
+        "space-infix-ops": "error",
+        "space-before-function-paren": ["error", "never"],
+        "space-before-blocks": "error",
+        "comma-dangle": ["error", "always-multiline"],
+        "comma-style": ["error", "last"],
+        "max-len": ["error", { "code": 100, "tabWidth": 4 }],
+        "eol-last": ["error", "always"],
+        "arrow-parens": ["error", "as-needed"],
+        "no-unused-vars": [
+            "error",
+            {
+                "argsIgnorePattern": "^_",
+                "varsIgnorePattern": "^_"
+            }
+        ],
+        "eqeqeq": "error",
+        "no-const-assign": "error",
+        "no-debugger": "error",
+        "no-dupe-args": "error",
+        "no-dupe-else-if": "error",
+        "no-dupe-keys": "error",
+        "no-duplicate-case": "error",
+        "no-ex-assign": "error",
+        "no-fallthrough": "error",
+        "no-invalid-regexp": "error",
+        "no-import-assign": "error",
+        "no-self-compare": "error",
+        "no-template-curly-in-string": "error",
+        "block-scoped-var": "error",
+        "guard-for-in": "error",
+        "no-alert": "error",
+        "no-confusing-arrow": "error",
+        "no-div-regex": "error",
+        "no-floating-decimal": "error",
+        "no-implicit-globals": "error",
+        "no-implied-eval": "error",
+        "no-label-var": "error",
+        "no-lonely-if": "error",
+        "no-mixed-operators": "error",
+        "no-multi-assign": "error",
+        "no-return-assign": "error",
+        "no-script-url": "error",
+        "no-sequences": "error",
+        "no-throw-literal": "error",
+        "no-div-regex": "error",
+    }
+};
diff --git a/src/librustdoc/html/static/COPYRIGHT.txt b/src/librustdoc/html/static/COPYRIGHT.txt
new file mode 100644
index 000000000..34e48134c
--- /dev/null
+++ b/src/librustdoc/html/static/COPYRIGHT.txt
@@ -0,0 +1,46 @@
+These documentation pages include resources by third parties. This copyright
+file applies only to those resources. The following third party resources are
+included, and carry their own copyright notices and license terms:
+
+* Fira Sans (FiraSans-Regular.woff2, FiraSans-Medium.woff2):
+
+    Copyright (c) 2014, Mozilla Foundation https://mozilla.org/
+    with Reserved Font Name Fira Sans.
+
+    Copyright (c) 2014, Telefonica S.A.
+
+    Licensed under the SIL Open Font License, Version 1.1.
+    See FiraSans-LICENSE.txt.
+
+* rustdoc.css, main.js, and playpen.js:
+
+    Copyright 2015 The Rust Developers.
+    Licensed under the Apache License, Version 2.0 (see LICENSE-APACHE.txt) or
+    the MIT license (LICENSE-MIT.txt) at your option.
+
+* normalize.css:
+
+    Copyright (c) Nicolas Gallagher and Jonathan Neal.
+    Licensed under the MIT license (see LICENSE-MIT.txt).
+
+* Source Code Pro (SourceCodePro-Regular.ttf.woff2,
+    SourceCodePro-Semibold.ttf.woff2, SourceCodePro-It.ttf.woff2):
+
+    Copyright 2010, 2012 Adobe Systems Incorporated (http://www.adobe.com/),
+    with Reserved Font Name 'Source'. All Rights Reserved. Source is a trademark
+    of Adobe Systems Incorporated in the United States and/or other countries.
+
+    Licensed under the SIL Open Font License, Version 1.1.
+    See SourceCodePro-LICENSE.txt.
+
+* Source Serif 4 (SourceSerif4-Regular.ttf.woff2, SourceSerif4-Bold.ttf.woff2,
+    SourceSerif4-It.ttf.woff2):
+
+    Copyright 2014-2021 Adobe (http://www.adobe.com/), with Reserved Font Name
+    'Source'. All Rights Reserved. Source is a trademark of Adobe in the United
+    States and/or other countries.
+
+    Licensed under the SIL Open Font License, Version 1.1.
+    See SourceSerif4-LICENSE.md.
+
+This copyright file is intended to be distributed with rustdoc output.
diff --git a/src/librustdoc/html/static/LICENSE-APACHE.txt b/src/librustdoc/html/static/LICENSE-APACHE.txt
new file mode 100644
index 000000000..16fe87b06
--- /dev/null
+++ b/src/librustdoc/html/static/LICENSE-APACHE.txt
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
+   control with that entity. For the purposes of this definition,
+   "control" means (i) the power, direct or indirect, to cause the
+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
+   and conversions to other media types.
+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
+   (an example is provided in the Appendix below).
+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
+   submitted to Licensor for inclusion in the Work by the copyright owner
+   or by an individual or Legal Entity authorized to submit on behalf of
+   the copyright owner. For the purposes of this definition, "submitted"
+   means any form of electronic, verbal, or written communication sent
+   to the Licensor or its representatives, including but not limited to
+   communication on electronic mailing lists, source code control systems,
+   and issue tracking systems that are managed by, or on behalf of, the
+   Licensor for the purpose of discussing and improving the Work, but
+   excluding communication that is conspicuously marked or otherwise
+   designated in writing by the copyright owner as "Not a Contribution."
+
+   "Contributor" shall mean Licensor and any individual or Legal Entity
+   on behalf of whom a Contribution has been received by Licensor and
+   subsequently incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   copyright license to reproduce, prepare Derivative Works of,
+   publicly display, publicly perform, sublicense, and distribute the
+   Work and such Derivative Works in Source or Object form.
+
+3. Grant of Patent License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   (except as stated in this section) patent license to make, have made,
+   use, offer to sell, sell, import, and otherwise transfer the Work,
+   where such license applies only to those patent claims licensable
+   by such Contributor that are necessarily infringed by their
+   Contribution(s) alone or by combination of their Contribution(s)
+   with the Work to which such Contribution(s) was submitted. If You
+   institute patent litigation against any entity (including a
+   cross-claim or counterclaim in a lawsuit) alleging that the Work
+   or a Contribution incorporated within the Work constitutes direct
+   or contributory patent infringement, then any patent licenses
+   granted to You under this License for that Work shall terminate
+   as of the date such litigation is filed.
+
+4. Redistribution. You may reproduce and distribute copies of the
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+   modifications, and in Source or Object form, provided that You
+   meet the following conditions:
+
+   (a) You must give any other recipients of the Work or
+       Derivative Works a copy of this License; and
+
+   (b) You must cause any modified files to carry prominent notices
+       stating that You changed the files; and
+
+   (c) You must retain, in the Source form of any Derivative Works
+       that You distribute, all copyright, patent, trademark, and
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+       excluding those notices that do not pertain to any part of
+       the Derivative Works; and
+
+   (d) If the Work includes a "NOTICE" text file as part of its
+       distribution, then any Derivative Works that You distribute must
+       include a readable copy of the attribution notices contained
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+       pertain to any part of the Derivative Works, in at least one
+       of the following places: within a NOTICE text file distributed
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+       wherever such third-party notices normally appear. The contents
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+       do not modify the License. You may add Your own attribution
+       notices within Derivative Works that You distribute, alongside
+       or as an addendum to the NOTICE text from the Work, provided
+       that such additional attribution notices cannot be construed
+       as modifying the License.
+
+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
+   risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
+   or other liability obligations and/or rights consistent with this
+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
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+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
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+
+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/src/librustdoc/html/static/LICENSE-MIT.txt b/src/librustdoc/html/static/LICENSE-MIT.txt
new file mode 100644
index 000000000..31aa79387
--- /dev/null
+++ b/src/librustdoc/html/static/LICENSE-MIT.txt
@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/src/librustdoc/html/static/css/normalize.css b/src/librustdoc/html/static/css/normalize.css
new file mode 100644
index 000000000..fdb8a8c65
--- /dev/null
+++ b/src/librustdoc/html/static/css/normalize.css
@@ -0,0 +1,2 @@
+/* ignore-tidy-linelength */
+/*! normalize.css v8.0.1 | MIT License | github.com/necolas/normalize.css */ html{line-height:1.15;-webkit-text-size-adjust:100%}body{margin:0}main{display:block}h1{font-size:2em;margin:0.67em 0}hr{box-sizing:content-box;height:0;overflow:visible}pre{font-family:monospace, monospace;font-size:1em}a{background-color:transparent}abbr[title]{border-bottom:none;text-decoration:underline;text-decoration:underline dotted}b,strong{font-weight:bolder}code,kbd,samp{font-family:monospace, monospace;font-size:1em}small{font-size:80%}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sub{bottom:-0.25em}sup{top:-0.5em}img{border-style:none}button,input,optgroup,select,textarea{font-family:inherit;font-size:100%;line-height:1.15;margin:0}button,input{overflow:visible}button,select{text-transform:none}[type="button"],[type="reset"],[type="submit"],button{-webkit-appearance:button}[type="button"]::-moz-focus-inner,[type="reset"]::-moz-focus-inner,[type="submit"]::-moz-focus-inner,button::-moz-focus-inner{border-style:none;padding:0}[type="button"]:-moz-focusring,[type="reset"]:-moz-focusring,[type="submit"]:-moz-focusring,button:-moz-focusring{outline:1px dotted ButtonText}fieldset{padding:0.35em 0.75em 0.625em}legend{box-sizing:border-box;color:inherit;display:table;max-width:100%;padding:0;white-space:normal}progress{vertical-align:baseline}textarea{overflow:auto}[type="checkbox"],[type="radio"]{box-sizing:border-box;padding:0}[type="number"]::-webkit-inner-spin-button,[type="number"]::-webkit-outer-spin-button{height:auto}[type="search"]{-webkit-appearance:textfield;outline-offset:-2px}[type="search"]::-webkit-search-decoration{-webkit-appearance:none}::-webkit-file-upload-button{-webkit-appearance:button;font:inherit}details{display:block}summary{display:list-item}template{display:none}[hidden]{display:none}
diff --git a/src/librustdoc/html/static/css/noscript.css b/src/librustdoc/html/static/css/noscript.css
new file mode 100644
index 000000000..0a19a99ab
--- /dev/null
+++ b/src/librustdoc/html/static/css/noscript.css
@@ -0,0 +1,20 @@
+/*
+This whole CSS file is used only in case rustdoc is rendered with javascript disabled. Since a lot
+of content is hidden by default (depending on the settings too), we have to overwrite some of the
+rules.
+*/
+
+#main-content .attributes {
+	/* Since there is no toggle (the "[-]") when JS is disabled, no need for this margin either. */
+	margin-left: 0 !important;
+}
+
+#copy-path {
+	/* It requires JS to work so no need to display it in this case. */
+	display: none;
+}
+
+.sub {
+	/* The search bar and related controls don't work without JS */
+	display: none;
+}
diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
new file mode 100644
index 000000000..83fe14550
--- /dev/null
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -0,0 +1,2335 @@
+/* See FiraSans-LICENSE.txt for the Fira Sans license. */
+@font-face {
+	font-family: 'Fira Sans';
+	font-style: normal;
+	font-weight: 400;
+	src: local('Fira Sans'),
+		url("FiraSans-Regular.woff2") format("woff2");
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Fira Sans';
+	font-style: normal;
+	font-weight: 500;
+	src: local('Fira Sans Medium'),
+		url("FiraSans-Medium.woff2") format("woff2");
+	font-display: swap;
+}
+
+/* See SourceSerif4-LICENSE.md for the Source Serif 4 license. */
+@font-face {
+	font-family: 'Source Serif 4';
+	font-style: normal;
+	font-weight: 400;
+	src: local('Source Serif 4'),
+		url("SourceSerif4-Regular.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Serif 4';
+	font-style: italic;
+	font-weight: 400;
+	src: local('Source Serif 4 Italic'),
+		url("SourceSerif4-It.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Serif 4';
+	font-style: normal;
+	font-weight: 700;
+	src: local('Source Serif 4 Bold'),
+		url("SourceSerif4-Bold.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+
+/* See SourceCodePro-LICENSE.txt for the Source Code Pro license. */
+@font-face {
+	font-family: 'Source Code Pro';
+	font-style: normal;
+	font-weight: 400;
+	/* Avoid using locally installed font because bad versions are in circulation:
+	 * see https://github.com/rust-lang/rust/issues/24355 */
+	src: url("SourceCodePro-Regular.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Code Pro';
+	font-style: italic;
+	font-weight: 400;
+	src: url("SourceCodePro-It.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Code Pro';
+	font-style: normal;
+	font-weight: 600;
+	src: url("SourceCodePro-Semibold.ttf.woff2") format("woff2");
+	font-display: swap;
+}
+
+/* Avoid using legacy CJK serif fonts in Windows like Batang. */
+@font-face {
+	font-family: 'NanumBarunGothic';
+	src: url("NanumBarunGothic.ttf.woff2") format("woff2");
+	font-display: swap;
+	unicode-range: U+AC00-D7AF, U+1100-11FF, U+3130-318F, U+A960-A97F, U+D7B0-D7FF;
+}
+
+* {
+	-webkit-box-sizing: border-box;
+	-moz-box-sizing: border-box;
+	box-sizing: border-box;
+}
+
+/* This part handles the "default" theme being used depending on the system one. */
+html {
+	content: "";
+}
+@media (prefers-color-scheme: light) {
+	html {
+		content: "light";
+	}
+}
+@media (prefers-color-scheme: dark) {
+	html {
+		content: "dark";
+	}
+}
+
+/* General structure and fonts */
+
+body {
+	/* Line spacing at least 1.5 per Web Content Accessibility Guidelines
+	   https://www.w3.org/WAI/WCAG21/Understanding/visual-presentation.html */
+	font: 1rem/1.5 "Source Serif 4", NanumBarunGothic, serif;
+	margin: 0;
+	position: relative;
+	/* We use overflow-wrap: break-word for Safari, which doesn't recognize
+	   `anywhere`: https://developer.mozilla.org/en-US/docs/Web/CSS/overflow-wrap */
+	overflow-wrap: break-word;
+	/* Then override it with `anywhere`, which is required to make non-Safari browsers break
+	   more aggressively when we want them to. */
+	overflow-wrap: anywhere;
+
+	-webkit-font-feature-settings: "kern", "liga";
+	-moz-font-feature-settings: "kern", "liga";
+	font-feature-settings: "kern", "liga";
+
+	background-color: var(--main-background-color);
+	color: var(--main-color);
+}
+
+h1 {
+	font-size: 1.5rem; /* 24px */
+}
+h2 {
+	font-size: 1.375rem; /* 22px */
+}
+h3 {
+	font-size: 1.25rem; /* 20px */
+}
+h1, h2, h3, h4, h5, h6 {
+	font-weight: 500;
+}
+h1, h2, h3, h4 {
+	margin: 20px 0 15px 0;
+	padding-bottom: 6px;
+}
+.docblock h3, .docblock h4, h5, h6 {
+	margin: 15px 0 5px 0;
+}
+h1.fqn {
+	margin: 0;
+	padding: 0;
+	border-bottom-color: var(--headings-border-bottom-color);
+}
+h2, h3, h4 {
+	border-bottom-color: var(--headings-border-bottom-color);
+}
+.main-heading {
+	display: flex;
+	flex-wrap: wrap;
+	justify-content: space-between;
+	padding-bottom: 6px;
+	margin-bottom: 15px;
+}
+.main-heading a:hover {
+	text-decoration: underline;
+}
+#toggle-all-docs {
+	text-decoration: none;
+}
+/* The only headings that get underlines are:
+	 Markdown-generated headings within the top-doc
+	 Rustdoc-generated h2 section headings (e.g. "Implementations", "Required Methods", etc)
+	Underlines elsewhere in the documentation break up visual flow and tend to invert
+	section hierarchies. */
+h2,
+.top-doc .docblock > h3,
+.top-doc .docblock > h4 {
+	border-bottom: 1px solid var(--headings-border-bottom-color);
+}
+h3.code-header {
+	font-size: 1.125rem; /* 18px */
+}
+h4.code-header {
+	font-size: 1rem;
+}
+.code-header {
+	font-weight: 600;
+	border-bottom-style: none;
+	margin: 0;
+	padding: 0;
+	margin-top: 0.6em;
+	margin-bottom: 0.4em;
+}
+.impl,
+.impl-items .method,
+.methods .method,
+.impl-items .type,
+.methods .type,
+.impl-items .associatedconstant,
+.methods .associatedconstant,
+.impl-items .associatedtype,
+.methods .associatedtype {
+	flex-basis: 100%;
+	font-weight: 600;
+	position: relative;
+}
+
+div.impl-items > div {
+	padding-left: 0;
+}
+
+h1, h2, h3, h4, h5, h6,
+.sidebar,
+.mobile-topbar,
+a.source,
+.search-input,
+.search-results .result-name,
+.content table td:first-child > a,
+.item-left > a,
+.out-of-band,
+span.since,
+#source-sidebar, #sidebar-toggle,
+details.rustdoc-toggle > summary::before,
+div.impl-items > div:not(.docblock):not(.item-info),
+.content ul.crate a.crate,
+a.srclink,
+#main-content > .since,
+#help-button > button,
+details.rustdoc-toggle.top-doc > summary,
+details.rustdoc-toggle.top-doc > summary::before,
+details.rustdoc-toggle.non-exhaustive > summary,
+details.rustdoc-toggle.non-exhaustive > summary::before,
+.scraped-example-title,
+.more-examples-toggle summary, .more-examples-toggle .hide-more,
+.example-links a,
+/* This selector is for the items listed in the "all items" page. */
+#main-content > ul.docblock > li > a {
+	font-family: "Fira Sans", Arial, NanumBarunGothic, sans-serif;
+}
+
+h1, h2, h3, h4,
+a#toggle-all-docs,
+a.anchor,
+.small-section-header a,
+#source-sidebar a,
+pre.rust a,
+.sidebar h2 a,
+.sidebar h3 a,
+.mobile-topbar h2 a,
+.in-band a,
+.search-results a,
+.module-item .stab,
+.import-item .stab,
+.result-name .primitive > i, .result-name .keyword > i,
+.content .method .where,
+.content .fn .where,
+.content .where.fmt-newline {
+	color: var(--main-color);
+}
+
+ol, ul {
+	padding-left: 24px;
+}
+ul ul, ol ul, ul ol, ol ol {
+	margin-bottom: .625em;
+}
+
+p {
+	/* Paragraph spacing at least 1.5 times line spacing per Web Content Accessibility Guidelines.
+	   Line-height is 1.5rem, so line spacing is .5rem; .75em is 1.5 times that.
+	   https://www.w3.org/WAI/WCAG21/Understanding/visual-presentation.html */
+	margin: 0 0 .75em 0;
+}
+
+summary {
+	outline: none;
+}
+
+/* Fix some style changes due to normalize.css 8 */
+
+td,
+th {
+	padding: 0;
+}
+
+table {
+	border-collapse: collapse;
+}
+
+button,
+input,
+optgroup,
+select,
+textarea {
+	color: inherit;
+	font: inherit;
+	margin: 0;
+}
+
+button {
+	/* Buttons on Safari have different default padding than other platforms. Make them the same. */
+	padding: 1px 6px;
+}
+
+/* end tweaks for normalize.css 8 */
+
+.rustdoc {
+	display: flex;
+	flex-direction: row;
+	flex-wrap: nowrap;
+}
+
+main {
+	position: relative;
+	flex-grow: 1;
+	padding: 10px 15px 40px 45px;
+	min-width: 0;
+}
+
+.source main {
+	padding: 15px;
+}
+
+.width-limiter {
+	max-width: 960px;
+	margin-right: auto;
+}
+
+.source .width-limiter {
+	max-width: unset;
+}
+
+details:not(.rustdoc-toggle) summary {
+	margin-bottom: .6em;
+}
+
+code, pre, a.test-arrow, .code-header {
+	font-family: "Source Code Pro", monospace;
+}
+.docblock code, .docblock-short code {
+	border-radius: 3px;
+	padding: 0 0.125em;
+}
+.docblock pre code, .docblock-short pre code {
+	padding: 0;
+}
+pre {
+	padding: 14px;
+}
+.docblock.item-decl {
+	margin-left: 0;
+}
+.item-decl pre {
+	overflow-x: auto;
+}
+
+.source .content pre {
+	padding: 20px;
+}
+
+img {
+	max-width: 100%;
+}
+
+li {
+	position: relative;
+}
+
+.source .content {
+	max-width: none;
+	overflow: visible;
+	margin-left: 0px;
+}
+
+nav.sub {
+	position: relative;
+	font-size: 1rem;
+}
+
+.sub-container {
+	display: flex;
+	flex-direction: row;
+	flex-wrap: nowrap;
+}
+
+.sub-logo-container {
+	display: none;
+	margin-right: 20px;
+}
+
+.source .sub-logo-container {
+	display: block;
+}
+
+.source .sub-logo-container > img {
+	height: 60px;
+	width: 60px;
+	object-fit: contain;
+}
+
+.sidebar, .mobile-topbar, .sidebar-menu-toggle {
+	background-color: var(--sidebar-background-color);
+}
+
+.sidebar {
+	font-size: 0.875rem;
+	width: 250px;
+	min-width: 200px;
+	overflow-y: scroll;
+	position: sticky;
+	height: 100vh;
+	top: 0;
+	left: 0;
+}
+
+.sidebar-elems,
+.sidebar > .location {
+	padding-left: 24px;
+}
+
+.sidebar .location {
+	overflow-wrap: anywhere;
+}
+
+.rustdoc.source .sidebar {
+	width: 50px;
+	min-width: 0px;
+	max-width: 300px;
+	flex-grow: 0;
+	flex-shrink: 0;
+	flex-basis: auto;
+	border-right: 1px solid;
+	overflow-x: hidden;
+	/* The sidebar is by default hidden  */
+	overflow-y: hidden;
+}
+
+.rustdoc.source .sidebar .sidebar-logo {
+	display: none;
+}
+
+.source .sidebar, #sidebar-toggle, #source-sidebar {
+	background-color: var(--sidebar-background-color);
+}
+
+#sidebar-toggle > button:hover, #sidebar-toggle > button:focus {
+	background-color: var(--sidebar-background-color-hover);
+}
+
+.source .sidebar > *:not(#sidebar-toggle) {
+	opacity: 0;
+	visibility: hidden;
+}
+
+.source-sidebar-expanded .source .sidebar {
+	overflow-y: auto;
+}
+
+.source-sidebar-expanded .source .sidebar > *:not(#sidebar-toggle) {
+	opacity: 1;
+	visibility: visible;
+}
+
+#all-types {
+	margin-top: 1em;
+}
+
+/* Improve the scrollbar display on firefox */
+* {
+	scrollbar-width: initial;
+	scrollbar-color: var(--scrollbar-color);
+}
+.sidebar {
+	scrollbar-width: thin;
+	scrollbar-color: var(--scrollbar-color);
+}
+
+/* Improve the scrollbar display on webkit-based browsers */
+::-webkit-scrollbar {
+	width: 12px;
+}
+.sidebar::-webkit-scrollbar {
+	width: 8px;
+}
+::-webkit-scrollbar-track {
+	-webkit-box-shadow: inset 0;
+	background-color: var(--scrollbar-track-background-color);
+}
+.sidebar::-webkit-scrollbar-track {
+	background-color: var(--scrollbar-track-background-color);
+}
+::-webkit-scrollbar-thumb, .sidebar::-webkit-scrollbar-thumb {
+	background-color: var(--scrollbar-thumb-background-color);
+}
+
+/* Everything else */
+
+.hidden {
+	display: none !important;
+}
+
+.sidebar .logo-container {
+	display: flex;
+	margin-top: 10px;
+	margin-bottom: 10px;
+	justify-content: center;
+}
+
+.version {
+	overflow-wrap: break-word;
+}
+
+.logo-container > img {
+	height: 100px;
+	width: 100px;
+}
+
+.location:empty {
+	border: none;
+}
+
+.location a:first-of-type {
+	font-weight: 500;
+}
+
+.block {
+	padding: 0;
+}
+.block ul, .block li {
+	padding: 0;
+	margin: 0;
+	list-style: none;
+}
+
+.block a,
+h2.location a {
+	display: block;
+	padding: 0.25rem;
+	margin-left: -0.25rem;
+
+	text-overflow: ellipsis;
+	overflow: hidden;
+}
+
+.sidebar h2 {
+	border-bottom: none;
+	font-weight: 500;
+	padding: 0;
+	margin: 0;
+	margin-top: 0.7rem;
+	margin-bottom: 0.7rem;
+}
+
+.sidebar h3 {
+	font-size: 1.125rem; /* 18px */
+	font-weight: 500;
+	padding: 0;
+	margin: 0;
+}
+
+.sidebar-elems .block {
+	margin-bottom: 2em;
+}
+
+.sidebar-elems .block li a {
+	white-space: nowrap;
+}
+
+.mobile-topbar {
+	display: none;
+}
+
+.source .content pre.rust {
+	white-space: pre;
+	overflow: auto;
+	padding-left: 0;
+}
+
+.rustdoc .example-wrap {
+	display: inline-flex;
+	margin-bottom: 10px;
+}
+
+.example-wrap {
+	position: relative;
+	width: 100%;
+}
+
+.example-wrap > pre.line-number {
+	overflow: initial;
+	border: 1px solid;
+	padding: 13px 8px;
+	text-align: right;
+	border-top-left-radius: 5px;
+	border-bottom-left-radius: 5px;
+}
+
+.example-wrap > pre.rust a:hover {
+	text-decoration: underline;
+}
+
+.line-numbers {
+	text-align: right;
+}
+.rustdoc:not(.source) .example-wrap > pre:not(.line-number) {
+	width: 100%;
+	overflow-x: auto;
+}
+
+.rustdoc:not(.source) .example-wrap > pre.line-numbers {
+	width: auto;
+	overflow-x: visible;
+}
+
+.rustdoc .example-wrap > pre {
+	margin: 0;
+}
+
+#search {
+	position: relative;
+}
+
+.search-loading {
+	text-align: center;
+}
+
+#results > table {
+	width: 100%;
+	table-layout: fixed;
+}
+
+.content > .example-wrap pre.line-numbers {
+	position: relative;
+	-webkit-user-select: none;
+	-moz-user-select: none;
+	-ms-user-select: none;
+	user-select: none;
+}
+.line-numbers span {
+	cursor: pointer;
+}
+
+.docblock-short {
+	overflow-wrap: break-word;
+	overflow-wrap: anywhere;
+}
+.docblock-short p {
+	display: inline;
+}
+
+.docblock-short p {
+	overflow: hidden;
+	text-overflow: ellipsis;
+	margin: 0;
+}
+/* Wrap non-pre code blocks (`text`) but not (```text```). */
+.docblock > :not(pre) > code,
+.docblock-short > :not(pre) > code {
+	white-space: pre-wrap;
+}
+
+.top-doc .docblock h2 { font-size: 1.375rem; }
+.top-doc .docblock h3 { font-size: 1.25rem; }
+.top-doc .docblock h4,
+.top-doc .docblock h5 {
+	font-size: 1.125rem;
+}
+.top-doc .docblock h6 {
+	font-size: 1rem;
+}
+
+.docblock h5 { font-size: 1rem; }
+.docblock h6 { font-size: 0.875rem; }
+.docblock h1, .docblock h2, .docblock h3, .docblock h4, .docblock h5, .docblock h6 {
+	border-bottom-color: var(--headings-border-bottom-color);
+}
+
+.docblock {
+	margin-left: 24px;
+	position: relative;
+}
+
+.docblock > :not(.information):not(.more-examples-toggle) {
+	max-width: 100%;
+	overflow-x: auto;
+}
+
+.content .out-of-band {
+	flex-grow: 0;
+	font-size: 1.125rem;
+	font-weight: normal;
+	float: right;
+}
+
+.method > .code-header, .trait-impl > .code-header {
+	max-width: calc(100% - 41px);
+	display: block;
+}
+
+.content .in-band {
+	flex-grow: 1;
+	margin: 0px;
+	padding: 0px;
+	overflow-wrap: break-word;
+	overflow-wrap: anywhere;
+}
+
+.in-band > code, .in-band > .code-header {
+	display: inline-block;
+}
+
+.docblock code, .docblock-short code,
+pre, .rustdoc.source .example-wrap {
+	background-color: var(--code-block-background-color);
+}
+
+#main-content {
+	position: relative;
+}
+#main-content > .since {
+	top: inherit;
+}
+
+.content table:not(.table-display) {
+	border-spacing: 0 5px;
+}
+.content td { vertical-align: top; }
+.content td:first-child { padding-right: 20px; }
+.content td p:first-child { margin-top: 0; }
+.content td h1, .content td h2 { margin-left: 0; font-size: 1.125rem; }
+.content tr:first-child td { border-top: 0; }
+
+.docblock table {
+	margin: .5em 0;
+	width: calc(100% - 2px);
+	overflow-x: auto;
+	display: block;
+}
+
+.docblock table td {
+	padding: .5em;
+	border: 1px dashed;
+}
+
+.docblock table th {
+	padding: .5em;
+	text-align: left;
+	border: 1px solid;
+}
+
+.fields + table {
+	margin-bottom: 1em;
+}
+
+.content .item-list {
+	list-style-type: none;
+	padding: 0;
+}
+
+.content .multi-column {
+	-moz-column-count: 5;
+	-moz-column-gap: 2.5em;
+	-webkit-column-count: 5;
+	-webkit-column-gap: 2.5em;
+	column-count: 5;
+	column-gap: 2.5em;
+}
+.content .multi-column li { width: 100%; display: inline-block; }
+
+.content > .methods > .method {
+	font-size: 1rem;
+	position: relative;
+}
+/* Shift "where ..." part of method or fn definition down a line */
+.content .method .where,
+.content .fn .where,
+.content .where.fmt-newline {
+	display: block;
+	font-size: 0.875rem;
+}
+
+.content .methods > div:not(.notable-traits):not(.method) {
+	margin-left: 40px;
+	margin-bottom: 15px;
+}
+
+.content .docblock > .impl-items {
+	margin-left: 20px;
+	margin-top: -34px;
+}
+.content .docblock >.impl-items .table-display {
+	margin: 0;
+}
+.content .docblock >.impl-items table td {
+	padding: 0;
+}
+.content .docblock > .impl-items .table-display, .impl-items table td {
+	border: none;
+}
+
+.item-info {
+	display: block;
+}
+
+.content .item-info code {
+	font-size: 0.875rem;
+}
+
+.content .item-info {
+	position: relative;
+	margin-left: 24px;
+}
+
+.sub-variant > div > .item-info {
+	margin-top: initial;
+}
+
+.content .impl-items .docblock, .content .impl-items .item-info {
+	margin-bottom: .6em;
+}
+
+.content .impl-items > .item-info {
+	margin-left: 40px;
+}
+
+.methods > .item-info, .content .impl-items > .item-info {
+	margin-top: -8px;
+}
+
+.impl-items {
+	flex-basis: 100%;
+}
+
+#main-content > .item-info {
+	margin-top: 0;
+	margin-left: 0;
+}
+
+nav.sub {
+	flex-grow: 1;
+	margin-bottom: 25px;
+}
+.source nav.sub {
+	margin-left: 32px;
+}
+nav.main {
+	padding: 20px 0;
+	text-align: center;
+}
+nav.main .current {
+	border-top: 1px solid;
+	border-bottom: 1px solid;
+}
+nav.main .separator {
+	border: 1px solid;
+	display: inline-block;
+	height: 23px;
+	margin: 0 20px;
+}
+nav.sum { text-align: right; }
+nav.sub form { display: inline; }
+
+a {
+	text-decoration: none;
+	background: transparent;
+}
+
+.small-section-header {
+	display: flex;
+	justify-content: space-between;
+	position: relative;
+}
+
+.small-section-header:hover > .anchor {
+	display: initial;
+}
+
+.in-band:hover > .anchor, .impl:hover > .anchor, .method.trait-impl:hover > .anchor,
+.type.trait-impl:hover > .anchor, .associatedconstant.trait-impl:hover > .anchor,
+.associatedtype.trait-impl:hover > .anchor {
+	display: inline-block;
+	position: absolute;
+}
+.anchor {
+	display: none;
+	position: absolute;
+	left: -0.5em;
+	background: none !important;
+}
+.anchor.field {
+	left: -5px;
+}
+.small-section-header > .anchor {
+	left: -15px;
+	padding-right: 8px;
+}
+h2.small-section-header > .anchor {
+	padding-right: 6px;
+}
+.anchor::before {
+	content: '§';
+}
+
+.docblock a:not(.srclink):not(.test-arrow):not(.scrape-help):hover,
+.docblock-short a:not(.srclink):not(.test-arrow):not(.scrape-help):hover, .item-info a {
+	text-decoration: underline;
+}
+
+.block a.current.crate { font-weight: 500; }
+
+/*  In most contexts we use `overflow-wrap: anywhere` to ensure that we can wrap
+	as much as needed on mobile (see
+	src/test/rustdoc-gui/type-declaration-overflow.goml for an example of why
+	this matters). The `anywhere` value means:
+
+	"Soft wrap opportunities introduced by the word break are considered when
+	 calculating min-content intrinsic sizes."
+
+	https://developer.mozilla.org/en-US/docs/Web/CSS/overflow-wrap#values
+
+	For table layouts, that becomes a problem: the browser tries to make each
+	column as narrow as possible, and `overflow-wrap: anywhere` means it can do
+	so by breaking words - even if some other column could be shrunk without
+	breaking words! This shows up, for instance, in the `Structs` / `Modules` /
+	`Functions` (etcetera) sections of a module page, and when a docblock
+	contains a table.
+
+	So, for table layouts, override the default with break-word, which does
+	_not_ affect min-content intrinsic sizes.
+*/
+table,
+.item-table {
+	overflow-wrap: break-word;
+}
+
+.item-table {
+	display: table;
+}
+.item-row {
+	display: table-row;
+}
+.item-left, .item-right {
+	display: table-cell;
+}
+.item-left {
+	padding-right: 1.25rem;
+}
+
+.search-container {
+	position: relative;
+	display: flex;
+	height: 34px;
+}
+.search-container > * {
+	height: 100%;
+}
+.search-results-title {
+	display: inline;
+}
+#search-settings {
+	font-size: 1.5rem;
+	font-weight: 500;
+	margin-bottom: 20px;
+}
+#crate-search {
+	min-width: 115px;
+	margin-top: 5px;
+	padding-left: 0.15em;
+	padding-right: 23px;
+	border: 1px solid;
+	border-radius: 4px;
+	outline: none;
+	cursor: pointer;
+	-moz-appearance: none;
+	-webkit-appearance: none;
+	/* Removes default arrow from firefox */
+	background-repeat: no-repeat;
+	background-color: transparent;
+	background-size: 20px;
+	background-position: calc(100% - 1px) 56%;
+	background-image: /* AUTOREPLACE: */url("down-arrow.svg");
+	max-width: 100%;
+	text-overflow: ellipsis;
+}
+.search-container {
+	margin-top: 4px;
+}
+.search-input {
+	/* Override Normalize.css: it has a rule that sets
+	   -webkit-appearance: textfield for search inputs. That
+	   causes rounded corners and no border on iOS Safari. */
+	-webkit-appearance: none;
+	/* Override Normalize.css: we have margins and do
+	 not want to overflow - the `moz` attribute is necessary
+	 until Firefox 29, too early to drop at this point */
+	-moz-box-sizing: border-box !important;
+	box-sizing: border-box !important;
+	outline: none;
+	border: 1px solid;
+	border-radius: 2px;
+	padding: 8px;
+	font-size: 1rem;
+	width: 100%;
+}
+
+.search-results {
+	display: none;
+	padding-bottom: 2em;
+}
+
+.search-results.active {
+	display: block;
+	/* prevent overhanging tabs from moving the first result */
+	clear: both;
+}
+
+.search-results .desc > span {
+	white-space: nowrap;
+	text-overflow: ellipsis;
+	overflow: hidden;
+	display: block;
+}
+
+.search-results > a {
+	display: block;
+	width: 100%;
+	/* A little margin ensures the browser's outlining of focused links has room to display. */
+	margin-left: 2px;
+	margin-right: 2px;
+	border-bottom: 1px solid #aaa3;
+}
+
+.search-results > a > div {
+	display: flex;
+	flex-flow: row wrap;
+}
+
+.search-results .result-name, .search-results div.desc, .search-results .result-description {
+	width: 50%;
+}
+.search-results .result-name {
+	padding-right: 1em;
+}
+
+.search-results .result-name > span {
+	display: inline-block;
+	margin: 0;
+	font-weight: normal;
+}
+
+.popover {
+	font-size: 1rem;
+	position: absolute;
+	right: 0;
+	z-index: 2;
+	display: block;
+	margin-top: 7px;
+	border-radius: 3px;
+	border: 1px solid;
+	font-size: 1rem;
+}
+
+/* This rule is to draw the little arrow connecting the settings menu to the gear icon. */
+.popover::before {
+	content: '';
+	position: absolute;
+	right: 11px;
+	border: solid;
+	border-width: 1px 1px 0 0;
+	display: inline-block;
+	padding: 4px;
+	transform: rotate(-45deg);
+	top: -5px;
+}
+
+.popover, .popover::before {
+	background-color: var(--main-background-color);
+	color: var(--main-color);
+}
+
+#help-button .popover {
+	max-width: 600px;
+}
+
+#help-button .popover::before {
+	right: 48px;
+}
+
+#help-button dt {
+	float: left;
+	clear: left;
+	display: block;
+	margin-right: 0.5rem;
+}
+#help-button span.top, #help-button span.bottom {
+	text-align: center;
+	display: block;
+	font-size: 1.125rem;
+}
+#help-button span.top {
+	text-align: center;
+	display: block;
+	margin: 10px 0;
+	border-bottom: 1px solid;
+	padding-bottom: 4px;
+	margin-bottom: 6px;
+}
+#help-button span.bottom {
+	clear: both;
+	border-top: 1px solid;
+}
+.side-by-side {
+	text-align: initial;
+}
+.side-by-side > div {
+	width: 50%;
+	float: left;
+	padding: 0 20px 20px 17px;
+}
+
+.item-info .stab {
+	width: fit-content;
+	/* This min-height is needed to unify the height of the stab elements because some of them
+	   have emojis.
+	*/
+	min-height: 36px;
+	display: flex;
+	align-items: center;
+	white-space: pre-wrap;
+}
+.stab {
+	padding: 3px;
+	margin-bottom: 5px;
+	font-size: 0.875rem;
+	font-weight: normal;
+}
+.stab p {
+	display: inline;
+	margin: 0;
+}
+
+.stab .emoji {
+	font-size: 1.25rem;
+}
+
+/* Black one-pixel outline around emoji shapes */
+.emoji {
+	text-shadow:
+		1px 0 0 black,
+		-1px 0 0 black,
+		0  1px 0 black,
+		0 -1px 0 black;
+}
+
+.module-item .stab,
+.import-item .stab {
+	border-radius: 3px;
+	display: inline-block;
+	font-size: 0.875rem;
+	line-height: 1.2;
+	margin-bottom: 0;
+	margin-left: 0.3125em;
+	padding: 2px;
+	vertical-align: text-bottom;
+}
+
+.module-item.unstable,
+.import-item.unstable {
+	opacity: 0.65;
+}
+
+.since {
+	font-weight: normal;
+	font-size: initial;
+}
+
+.rightside {
+	padding-left: 12px;
+	padding-right: 2px;
+	position: initial;
+}
+
+.impl-items .srclink, .impl .srclink, .methods .srclink {
+	/* Override header settings otherwise it's too bold */
+	font-weight: normal;
+	font-size: 1rem;
+}
+
+.rightside {
+	float: right;
+}
+
+.variants_table {
+	width: 100%;
+}
+
+.variants_table tbody tr td:first-child {
+	width: 1%; /* make the variant name as small as possible */
+}
+
+td.summary-column {
+	width: 100%;
+}
+
+.summary {
+	padding-right: 0px;
+}
+
+pre.rust .question-mark {
+	font-weight: bold;
+}
+
+a.test-arrow {
+	display: inline-block;
+	visibility: hidden;
+	position: absolute;
+	padding: 5px 10px 5px 10px;
+	border-radius: 5px;
+	font-size: 1.375rem;
+	top: 5px;
+	right: 5px;
+	z-index: 1;
+}
+.example-wrap:hover .test-arrow {
+	visibility: visible;
+}
+a.test-arrow:hover{
+	text-decoration: none;
+}
+
+.code-attribute {
+	font-weight: 300;
+}
+
+.item-spacer {
+	width: 100%;
+	height: 12px;
+}
+
+.out-of-band > span.since {
+	position: initial;
+	font-size: 1.25rem;
+}
+
+h3.variant {
+	font-weight: 600;
+	font-size: 1.125rem;
+	margin-bottom: 10px;
+	border-bottom: none;
+}
+
+.sub-variant h4 {
+	font-size: 1rem;
+	font-weight: 400;
+	border-bottom: none;
+	margin-top: 0;
+	margin-bottom: 0;
+}
+
+.sub-variant {
+	margin-left: 24px;
+	margin-bottom: 40px;
+}
+
+.sub-variant > .sub-variant-field {
+	margin-left: 24px;
+}
+
+.toggle-label {
+	display: inline-block;
+	margin-left: 4px;
+	margin-top: 3px;
+}
+
+:target > code, :target > .code-header {
+	opacity: 1;
+}
+
+:target {
+	padding-right: 3px;
+}
+
+.information {
+	position: absolute;
+	left: -25px;
+	margin-top: 7px;
+	z-index: 1;
+}
+
+.tooltip {
+	position: relative;
+	display: inline-block;
+	cursor: pointer;
+}
+
+.tooltip::after {
+	display: none;
+	text-align: center;
+	padding: 5px 3px 3px 3px;
+	border-radius: 6px;
+	margin-left: 5px;
+	font-size: 1rem;
+}
+
+.tooltip.ignore::after {
+	content: "This example is not tested";
+}
+.tooltip.compile_fail::after {
+	content: "This example deliberately fails to compile";
+}
+.tooltip.should_panic::after {
+	content: "This example panics";
+}
+.tooltip.edition::after {
+	content: "This code runs with edition " attr(data-edition);
+}
+
+.tooltip::before {
+	content: " ";
+	position: absolute;
+	top: 50%;
+	left: 16px;
+	margin-top: -5px;
+	border-width: 5px;
+	border-style: solid;
+	display: none;
+}
+
+.tooltip:hover::before, .tooltip:hover::after {
+	display: inline;
+}
+
+.tooltip.compile_fail, .tooltip.should_panic, .tooltip.ignore {
+	font-weight: bold;
+	font-size: 1.25rem;
+}
+
+.notable-traits-tooltip {
+	display: inline-block;
+	cursor: pointer;
+}
+
+.notable-traits:hover .notable-traits-tooltiptext,
+.notable-traits .notable-traits-tooltiptext.force-tooltip {
+	display: inline-block;
+}
+
+.notable-traits .notable-traits-tooltiptext {
+	display: none;
+	padding: 5px 3px 3px 3px;
+	border-radius: 6px;
+	margin-left: 5px;
+	z-index: 10;
+	font-size: 1rem;
+	cursor: default;
+	position: absolute;
+	border: 1px solid;
+}
+
+.notable-traits-tooltip::after {
+	/* The margin on the tooltip does not capture hover events,
+	   this extends the area of hover enough so that mouse hover is not
+	   lost when moving the mouse to the tooltip */
+	content: "\00a0\00a0\00a0";
+}
+
+.notable-traits .notable, .notable-traits .docblock {
+	margin: 0;
+}
+
+.notable-traits .notable {
+	margin: 0;
+	margin-bottom: 13px;
+	font-size: 1.1875rem;
+	font-weight: 600;
+	display: block;
+}
+
+.notable-traits .docblock code.content{
+	margin: 0;
+	padding: 0;
+	font-size: 1.25rem;
+}
+
+/* Example code has the "Run" button that needs to be positioned relative to the pre */
+pre.rust.rust-example-rendered {
+	position: relative;
+}
+
+pre.rust {
+	tab-size: 4;
+	-moz-tab-size: 4;
+}
+
+.search-failed {
+	text-align: center;
+	margin-top: 20px;
+	display: none;
+}
+
+.search-failed.active {
+	display: block;
+}
+
+.search-failed > ul {
+	text-align: left;
+	max-width: 570px;
+	margin-left: auto;
+	margin-right: auto;
+}
+
+#titles {
+	height: 35px;
+}
+
+#titles > button {
+	float: left;
+	width: 33.3%;
+	text-align: center;
+	font-size: 1.125rem;
+	cursor: pointer;
+	border: 0;
+	border-top: 2px solid;
+}
+
+#titles > button:first-child:last-child {
+	margin-right: 1px;
+	width: calc(100% - 1px);
+}
+
+#titles > button:not(:last-child) {
+	margin-right: 1px;
+	width: calc(33.3% - 1px);
+}
+
+#titles > button > div.count {
+	display: inline-block;
+	font-size: 1rem;
+}
+
+.notable-traits {
+	cursor: pointer;
+	z-index: 2;
+	margin-left: 5px;
+}
+
+#sidebar-toggle {
+	position: sticky;
+	top: 0;
+	left: 0;
+	font-weight: bold;
+	font-size: 1.25rem;
+	border-bottom: 1px solid;
+	display: flex;
+	height: 40px;
+	justify-content: center;
+	align-items: center;
+	z-index: 10;
+}
+#source-sidebar {
+	width: 100%;
+	z-index: 1;
+	overflow: auto;
+}
+#source-sidebar > .title {
+	font-size: 1.5rem;
+	text-align: center;
+	border-bottom: 1px solid;
+	margin-bottom: 6px;
+}
+#sidebar-toggle > button {
+	background: none;
+	color: inherit;
+	cursor: pointer;
+	text-align: center;
+	border: none;
+	outline: none;
+	position: absolute;
+	top: 0;
+	bottom: 0;
+	left: 0;
+	right: 0;
+	/* work around button layout strangeness: https://stackoverflow.com/q/7271561 */
+	width: 100%;
+	/* iOS button gradient: https://stackoverflow.com/q/5438567 */
+	-webkit-appearance: none;
+	opacity: 1;
+}
+#settings-menu, #help-button {
+	margin-left: 4px;
+	outline: none;
+}
+
+#copy-path {
+	height: 34px;
+}
+#settings-menu > a, #help-button > button, #copy-path {
+	padding: 5px;
+	width: 33px;
+	border: 1px solid;
+	border-radius: 2px;
+	cursor: pointer;
+}
+#settings-menu {
+	padding: 0;
+}
+#settings-menu > a, #help-button > button {
+	padding: 5px;
+	height: 100%;
+	display: block;
+}
+
+@keyframes rotating {
+	from {
+		transform: rotate(0deg);
+	}
+	to {
+		transform: rotate(360deg);
+	}
+}
+#settings-menu.rotate > a img {
+	animation: rotating 2s linear infinite;
+}
+
+.setting-line .radio-line input:checked {
+	box-shadow: inset 0 0 0 3px var(--main-background-color);
+	background-color: var(--settings-input-color);
+}
+.setting-line .radio-line input:focus {
+	box-shadow: 0 0 1px 1px var(--settings-input-color);
+}
+/* In here we combine both `:focus` and `:checked` properties. */
+.setting-line .radio-line input:checked:focus {
+	box-shadow: inset 0 0 0 3px var(--main-background-color),
+		0 0 2px 2px var(--settings-input-color);
+}
+.setting-line .radio-line input:hover {
+	border-color: var(--settings-input-color) !important;
+}
+input:checked + .slider {
+	background-color: var(--settings-input-color);
+}
+
+#help-button > button {
+	text-align: center;
+	/* Rare exception to specifying font sizes in rem. Since this is acting
+	   as an icon, it's okay to specify their sizes in pixels. */
+	font-size: 20px;
+	padding-top: 2px;
+}
+
+#copy-path {
+	background: initial;
+	margin-left: 10px;
+	padding: 0;
+	padding-left: 2px;
+	border: 0;
+}
+
+#theme-choices {
+	display: none;
+	position: absolute;
+	left: 0;
+	top: 28px;
+	border: 1px solid;
+	border-radius: 3px;
+	z-index: 1;
+	cursor: pointer;
+}
+
+#theme-choices > button {
+	border: none;
+	width: 100%;
+	padding: 4px 8px;
+	text-align: center;
+	background: rgba(0,0,0,0);
+	overflow-wrap: normal;
+}
+
+#theme-choices > button:not(:first-child) {
+	border-top: 1px solid;
+}
+
+kbd {
+	display: inline-block;
+	padding: 3px 5px;
+	font: 15px monospace;
+	line-height: 10px;
+	vertical-align: middle;
+	border: solid 1px;
+	border-radius: 3px;
+	cursor: default;
+}
+
+.hidden-by-impl-hider,
+.hidden-by-usual-hider {
+	/* important because of conflicting rule for small screens */
+	display: none !important;
+}
+
+#implementations-list > h3 > span.in-band {
+	width: 100%;
+}
+
+.table-display {
+	width: 100%;
+	border: 0;
+	border-collapse: collapse;
+	border-spacing: 0;
+	font-size: 1rem;
+}
+
+.table-display tr td:first-child {
+	padding-right: 0;
+}
+
+.table-display tr td:last-child {
+	float: right;
+}
+.table-display .out-of-band {
+	position: relative;
+	font-size: 1.125rem;
+	display: block;
+}
+
+.table-display td:hover .anchor {
+	display: block;
+	top: 2px;
+	left: -5px;
+}
+
+#main-content > ul {
+	padding-left: 10px;
+}
+#main-content > ul > li {
+	list-style: none;
+}
+
+.non-exhaustive {
+	margin-bottom: 1em;
+}
+
+details.dir-entry {
+	padding-left: 4px;
+}
+
+details.dir-entry > summary {
+	margin: 0 0 0 13px;
+	list-style-position: outside;
+	cursor: pointer;
+}
+
+details.dir-entry div.folders, details.dir-entry div.files {
+	padding-left: 23px;
+}
+
+details.dir-entry a {
+	display: block;
+}
+
+/* The hideme class is used on summary tags that contain a span with
+	placeholder text shown only when the toggle is closed. For instance,
+	"Expand description" or "Show methods". */
+details.rustdoc-toggle > summary.hideme {
+	cursor: pointer;
+}
+
+details.rustdoc-toggle > summary {
+	list-style: none;
+}
+details.rustdoc-toggle > summary::-webkit-details-marker,
+details.rustdoc-toggle > summary::marker {
+	display: none;
+}
+
+details.rustdoc-toggle > summary.hideme > span {
+	margin-left: 9px;
+}
+
+details.rustdoc-toggle > summary::before {
+	content: "";
+	cursor: pointer;
+	width: 16px;
+	height: 16px;
+	background-repeat: no-repeat;
+	background-position: top left;
+	display: inline-block;
+	vertical-align: middle;
+	opacity: .5;
+}
+
+/* Screen readers see the text version at the end the line.
+	Visual readers see the icon at the start of the line, but small and transparent. */
+details.rustdoc-toggle > summary::after {
+	content: "Expand";
+	overflow: hidden;
+	width: 0;
+	height: 0;
+	position: absolute;
+}
+
+details.rustdoc-toggle > summary.hideme::after {
+	/* "hideme" toggles already have a description when they're contracted */
+	content: "";
+}
+
+details.rustdoc-toggle > summary:focus::before,
+details.rustdoc-toggle > summary:hover::before {
+	opacity: 1;
+}
+
+details.rustdoc-toggle.top-doc > summary,
+details.rustdoc-toggle.top-doc > summary::before,
+details.rustdoc-toggle.non-exhaustive > summary,
+details.rustdoc-toggle.non-exhaustive > summary::before {
+	font-size: 1rem;
+}
+
+details.non-exhaustive {
+	margin-bottom: 8px;
+}
+
+details.rustdoc-toggle > summary.hideme::before {
+	position: relative;
+}
+
+details.rustdoc-toggle > summary:not(.hideme)::before {
+	position: absolute;
+	left: -24px;
+	top: 4px;
+}
+
+.impl-items > details.rustdoc-toggle > summary:not(.hideme)::before {
+	position: absolute;
+	left: -24px;
+}
+
+/* When a "hideme" summary is open and the "Expand description" or "Show
+	methods" text is hidden, we want the [-] toggle that remains to not
+	affect the layout of the items to its right. To do that, we use
+	absolute positioning. Note that we also set position: relative
+	on the parent <details> to make this work properly. */
+details.rustdoc-toggle[open] > summary.hideme {
+	position: absolute;
+}
+
+details.rustdoc-toggle {
+	position: relative;
+}
+
+details.rustdoc-toggle[open] > summary.hideme > span {
+	display: none;
+}
+
+details.rustdoc-toggle[open] > summary::before,
+details.rustdoc-toggle[open] > summary.hideme::before {
+	background-image: /* AUTOREPLACE: */url("toggle-minus.svg");
+}
+
+details.rustdoc-toggle > summary::before {
+	background-image: /* AUTOREPLACE: */url("toggle-plus.svg");
+}
+
+details.rustdoc-toggle[open] > summary::before,
+details.rustdoc-toggle[open] > summary.hideme::before {
+	width: 16px;
+	height: 16px;
+	background-repeat: no-repeat;
+	background-position: top left;
+	display: inline-block;
+	content: "";
+}
+
+details.rustdoc-toggle[open] > summary::after,
+details.rustdoc-toggle[open] > summary.hideme::after {
+	content: "Collapse";
+}
+
+/* This is needed in docblocks to have the "▶" element to be on the same line. */
+.docblock summary > * {
+	display: inline-block;
+}
+
+/* Media Queries */
+
+/*
+WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY;
+If you update this line, then you also need to update the line with the same warning
+in storage.js plus the media query with (max-width: 700px)
+*/
+@media (min-width: 701px) {
+	/* In case there is no documentation before a code block, we need to add some margin at the top
+	to prevent an overlay between the "collapse toggle" and the information tooltip.
+	However, it's not needed with smaller screen width because the doc/code block is always put
+	"one line" below. */
+	.docblock > .information:first-child > .tooltip {
+		margin-top: 16px;
+	}
+
+	/* When we expand the sidebar on the source code page, we hide the logo on the left of the
+	search bar to have more space. */
+	.source-sidebar-expanded .source .sidebar + main .width-limiter .sub-logo-container.rust-logo {
+		display: none;
+	}
+
+	.source-sidebar-expanded .source .sidebar {
+		width: 300px;
+	}
+}
+
+/*
+WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
+If you update this line, then you also need to update the line with the same warning
+in storage.js plus the media query with (min-width: 701px)
+*/
+@media (max-width: 700px) {
+	/* When linking to an item with an `id` (for instance, by clicking a link in the sidebar,
+	   or visiting a URL with a fragment like `#method.new`, we don't want the item to be obscured
+	   by the topbar. Anything with an `id` gets scroll-margin-top equal to .mobile-topbar's size.
+	*/
+	*[id] {
+		scroll-margin-top: 45px;
+	}
+
+	.rustdoc {
+		padding-top: 0px;
+		/* Sidebar should overlay main content, rather than pushing main content to the right.
+		   Turn off `display: flex` on the body element. */
+		display: block;
+	}
+
+	main {
+		padding-left: 15px;
+		padding-top: 0px;
+	}
+
+	.rustdoc,
+	.main-heading {
+		flex-direction: column;
+	}
+
+	.content .out-of-band {
+		text-align: left;
+		margin-left: initial;
+		padding: initial;
+	}
+
+	.content .out-of-band .since::before {
+		content: "Since ";
+	}
+
+	#copy-path {
+		display: none;
+	}
+
+	/* Hide the logo and item name from the sidebar. Those are displayed
+	   in the mobile-topbar instead. */
+	.sidebar .sidebar-logo,
+	.sidebar .location {
+		display: none;
+	}
+
+	.sidebar-elems {
+		margin-top: 1em;
+	}
+
+	.sidebar {
+		position: fixed;
+		top: 45px;
+		/* Hide the sidebar offscreen while not in use. Doing this instead of display: none means
+		   the sidebar stays visible for screen readers, which is useful for navigation. */
+		left: -1000px;
+		margin-left: 0;
+		margin: 0;
+		padding: 0;
+		z-index: 11;
+		/* Reduce height slightly to account for mobile topbar. */
+		height: calc(100vh - 45px);
+	}
+
+	/* The source view uses a different design for the sidebar toggle, and doesn't have a topbar,
+	   so don't bump down the main content or the sidebar. */
+	.source main,
+	.rustdoc.source .sidebar {
+		top: 0;
+		padding: 0;
+		height: 100vh;
+		border: 0;
+	}
+
+	.sidebar.shown,
+	.source-sidebar-expanded .source .sidebar,
+	.sidebar:focus-within {
+		left: 0;
+	}
+
+	.rustdoc.source > .sidebar {
+		position: fixed;
+		margin: 0;
+		z-index: 11;
+		width: 0;
+	}
+
+	.mobile-topbar .location a {
+		padding: 0;
+		margin: 0;
+	}
+
+	.mobile-topbar .location {
+		border: none;
+		padding: 0;
+		margin: auto 0.5em auto auto;
+		text-overflow: ellipsis;
+		overflow: hidden;
+		white-space: nowrap;
+		/* Rare exception to specifying font sizes in rem. Since the topbar
+		   height is specified in pixels, this also has to be specified in
+		   pixels to avoid overflowing the topbar when the user sets a bigger
+		   font size. */
+		font-size: 24px;
+	}
+
+	.mobile-topbar .logo-container {
+		max-height: 45px;
+	}
+
+	.mobile-topbar .logo-container > img {
+		max-width: 35px;
+		max-height: 35px;
+		margin-left: 20px;
+		margin-top: 5px;
+		margin-bottom: 5px;
+	}
+
+	.mobile-topbar {
+		display: flex;
+		flex-direction: row;
+		position: sticky;
+		z-index: 10;
+		font-size: 2rem;
+		height: 45px;
+		width: 100%;
+		left: 0;
+		top: 0;
+	}
+
+	.source .mobile-topbar {
+		display: none;
+	}
+
+	.sidebar-menu-toggle {
+		width: 45px;
+		/* Rare exception to specifying font sizes in rem. Since this is acting
+		   as an icon, it's okay to specify its sizes in pixels. */
+		font-size: 32px;
+		border: none;
+	}
+
+	.sidebar-elems {
+		background-color: var(--sidebar-background-color);
+	}
+
+	.source nav:not(.sidebar).sub {
+		margin-left: 32px;
+	}
+
+	.content {
+		margin-left: 0px;
+	}
+
+	.source .content {
+		margin-top: 10px;
+	}
+
+	#search {
+		margin-left: 0;
+		padding: 0;
+	}
+
+	.anchor {
+		display: none !important;
+	}
+
+	.notable-traits {
+		position: absolute;
+		left: -22px;
+		top: 24px;
+	}
+
+	#titles > button > div.count {
+		float: left;
+		width: 100%;
+	}
+
+	#titles {
+		height: 50px;
+	}
+
+	/* Because of ios, we need to actually have a full height sidebar title so the
+	 * actual sidebar can show up. But then we need to make it transparent so we don't
+	 * hide content. The filler just allows to create the background for the sidebar
+	 * title. But because of the absolute position, I had to lower the z-index.
+	 */
+	#sidebar-filler {
+		position: fixed;
+		left: 45px;
+		width: calc(100% - 45px);
+		top: 0;
+		height: 45px;
+		z-index: -1;
+		border-bottom: 1px solid;
+	}
+
+	#main-content > details.rustdoc-toggle > summary::before,
+	#main-content > div > details.rustdoc-toggle > summary::before {
+		left: -11px;
+	}
+
+	#sidebar-toggle {
+		position: fixed;
+		left: 1px;
+		top: 100px;
+		width: 30px;
+		font-size: 1.5rem;
+		text-align: center;
+		padding: 0;
+		z-index: 10;
+		border-top-right-radius: 3px;
+		border-bottom-right-radius: 3px;
+		cursor: pointer;
+		font-weight: bold;
+		border: 1px solid;
+		border-left: 0;
+	}
+
+	.source-sidebar-expanded #sidebar-toggle {
+		left: unset;
+		top: unset;
+		width: unset;
+		border-top-right-radius: unset;
+		border-bottom-right-radius: unset;
+		position: sticky;
+		border: 0;
+		border-bottom: 1px solid;
+	}
+
+	#source-sidebar {
+		z-index: 11;
+	}
+
+	#main-content > .line-numbers {
+		margin-top: 0;
+	}
+
+	.notable-traits .notable-traits-tooltiptext {
+		left: 0;
+		top: 100%;
+	}
+
+	/* We don't display the help button on mobile devices. */
+	#help-button {
+		display: none;
+	}
+
+	/* Display an alternating layout on tablets and phones */
+	.item-table {
+		display: block;
+	}
+	.item-row {
+		display: flex;
+		flex-flow: column wrap;
+	}
+	.item-left, .item-right {
+		width: 100%;
+	}
+
+	/* Display an alternating layout on tablets and phones */
+	.search-results > a {
+		border-bottom: 1px solid #aaa9;
+		padding: 5px 0px;
+	}
+	.search-results .result-name, .search-results div.desc, .search-results .result-description {
+		width: 100%;
+	}
+	.search-results div.desc, .search-results .result-description, .item-right {
+		padding-left: 2em;
+	}
+
+	.source-sidebar-expanded .source .sidebar {
+		max-width: 100vw;
+		width: 100vw;
+	}
+
+	/* Position of the "[-]" element. */
+	details.rustdoc-toggle:not(.top-doc) > summary {
+		margin-left: 10px;
+	}
+	.impl-items > details.rustdoc-toggle > summary:not(.hideme)::before,
+	#main-content > details.rustdoc-toggle:not(.top-doc) > summary::before,
+	#main-content > div > details.rustdoc-toggle > summary::before {
+		left: -11px;
+	}
+}
+
+@media print {
+	nav.sidebar, nav.sub, .content .out-of-band, a.srclink, #copy-path,
+	details.rustdoc-toggle[open] > summary::before, details.rustdoc-toggle > summary::before,
+	details.rustdoc-toggle.top-doc > summary {
+		display: none;
+	}
+
+	.docblock {
+		margin-left: 0;
+	}
+
+	main {
+		padding: 10px;
+	}
+}
+
+@media (max-width: 464px) {
+	#titles, #titles > button {
+		height: 73px;
+	}
+
+	#main-content > table:not(.table-display) td {
+		word-break: break-word;
+		width: 50%;
+	}
+
+	#crate-search {
+		border-radius: 4px;
+	}
+
+	.docblock {
+		margin-left: 12px;
+	}
+
+	.docblock code {
+		overflow-wrap: break-word;
+		overflow-wrap: anywhere;
+	}
+
+	.sub-container {
+		flex-direction: column;
+	}
+
+	.sub-logo-container {
+		align-self: center;
+	}
+
+	.source .sub-logo-container > img {
+		height: 35px;
+		width: 35px;
+	}
+
+	#sidebar-toggle {
+		top: 10px;
+	}
+	.source-sidebar-expanded #sidebar-toggle {
+		top: unset;
+	}
+}
+
+.method-toggle summary,
+.implementors-toggle summary,
+.impl {
+	margin-bottom: 0.75em;
+}
+
+.method-toggle[open] {
+	margin-bottom: 2em;
+}
+
+.implementors-toggle[open]  {
+	margin-bottom: 2em;
+}
+
+#trait-implementations-list .method-toggle,
+#synthetic-implementations-list .method-toggle,
+#blanket-implementations-list .method-toggle {
+	margin-bottom: 1em;
+}
+
+/* Begin: styles for --scrape-examples feature */
+
+.scraped-example-list .scrape-help {
+	margin-left: 10px;
+	padding: 0 4px;
+	font-weight: normal;
+	font-size: 12px;
+	position: relative;
+	bottom: 1px;
+	background: transparent;
+	border-width: 1px;
+	border-style: solid;
+	border-radius: 50px;
+}
+
+.scraped-example .code-wrapper {
+	position: relative;
+	display: flex;
+	flex-direction: row;
+	flex-wrap: wrap;
+	width: 100%;
+}
+
+.scraped-example:not(.expanded) .code-wrapper {
+	max-height: 240px;
+}
+
+.scraped-example:not(.expanded) .code-wrapper pre {
+	overflow-y: hidden;
+	max-height: 240px;
+	padding-bottom: 0;
+}
+
+.scraped-example:not(.expanded) .code-wrapper pre.line-numbers {
+	overflow-x: hidden;
+}
+
+.scraped-example .code-wrapper .prev {
+	position: absolute;
+	top: 0.25em;
+	right: 2.25em;
+	z-index: 100;
+	cursor: pointer;
+}
+
+.scraped-example .code-wrapper .next {
+	position: absolute;
+	top: 0.25em;
+	right: 1.25em;
+	z-index: 100;
+	cursor: pointer;
+}
+
+.scraped-example .code-wrapper .expand {
+	position: absolute;
+	top: 0.25em;
+	right: 0.25em;
+	z-index: 100;
+	cursor: pointer;
+}
+
+.scraped-example:not(.expanded) .code-wrapper:before {
+	content: " ";
+	width: 100%;
+	height: 5px;
+	position: absolute;
+	z-index: 100;
+	top: 0;
+}
+
+.scraped-example:not(.expanded) .code-wrapper:after {
+	content: " ";
+	width: 100%;
+	height: 5px;
+	position: absolute;
+	z-index: 100;
+	bottom: 0;
+}
+
+.scraped-example .code-wrapper .line-numbers {
+	margin: 0;
+	padding: 14px 0;
+}
+
+.scraped-example .code-wrapper .line-numbers span {
+	padding: 0 14px;
+}
+
+.scraped-example .code-wrapper .example-wrap {
+	flex: 1;
+	overflow-x: auto;
+	overflow-y: hidden;
+	margin-bottom: 0;
+}
+
+.scraped-example:not(.expanded) .code-wrapper .example-wrap {
+	overflow-x: hidden;
+}
+
+.scraped-example .code-wrapper .example-wrap pre.rust {
+	overflow-x: inherit;
+	width: inherit;
+	overflow-y: hidden;
+}
+
+
+.more-examples-toggle {
+	max-width: calc(100% + 25px);
+	margin-top: 10px;
+	margin-left: -25px;
+}
+
+.more-examples-toggle .hide-more {
+	margin-left: 25px;
+	margin-bottom: 5px;
+	cursor: pointer;
+}
+
+.more-scraped-examples {
+	margin-left: 5px;
+	display: flex;
+	flex-direction: row;
+}
+
+.more-scraped-examples-inner {
+	/* 20px is width of toggle-line + toggle-line-inner */
+	width: calc(100% - 20px);
+}
+
+.toggle-line {
+	align-self: stretch;
+	margin-right: 10px;
+	margin-top: 5px;
+	padding: 0 4px;
+	cursor: pointer;
+}
+
+.toggle-line-inner {
+	min-width: 2px;
+	height: 100%;
+}
+
+.more-scraped-examples .scraped-example {
+	margin-bottom: 20px;
+}
+
+.more-scraped-examples .scraped-example:last-child {
+	margin-bottom: 0;
+}
+
+.example-links a {
+	margin-top: 20px;
+}
+
+.example-links ul {
+	margin-bottom: 0;
+}
+
+/* End: styles for --scrape-examples feature */
diff --git a/src/librustdoc/html/static/css/settings.css b/src/librustdoc/html/static/css/settings.css
new file mode 100644
index 000000000..e82ec0426
--- /dev/null
+++ b/src/librustdoc/html/static/css/settings.css
@@ -0,0 +1,90 @@
+.setting-line {
+	margin: 0.6em 0 0.6em 0.3em;
+	position: relative;
+}
+
+.setting-line .choices {
+	display: flex;
+	flex-wrap: wrap;
+}
+
+.setting-line .radio-line input {
+	margin-right: 0.3em;
+	height: 1.2rem;
+	width: 1.2rem;
+	border: 1px solid;
+	outline: none;
+	-webkit-appearance: none;
+	cursor: pointer;
+	border-radius: 50%;
+}
+.setting-line .radio-line input + span {
+	padding-bottom: 1px;
+}
+
+.radio-line .setting-name {
+	width: 100%;
+}
+
+.radio-line .choice {
+	margin-top: 0.1em;
+	margin-bottom: 0.1em;
+	min-width: 3.8em;
+	padding: 0.3em;
+	display: flex;
+	align-items: center;
+	cursor: pointer;
+}
+.radio-line .choice + .choice {
+	margin-left: 0.5em;
+}
+
+.toggle {
+	position: relative;
+	width: 100%;
+	margin-right: 20px;
+	display: flex;
+	align-items: center;
+	cursor: pointer;
+}
+
+.toggle input {
+	opacity: 0;
+	position: absolute;
+}
+
+.slider {
+	position: relative;
+	width: 45px;
+	min-width: 45px;
+	display: block;
+	height: 28px;
+	margin-right: 20px;
+	cursor: pointer;
+	background-color: #ccc;
+	transition: .3s;
+}
+
+.slider:before {
+	position: absolute;
+	content: "";
+	height: 19px;
+	width: 19px;
+	left: 4px;
+	bottom: 4px;
+	transition: .3s;
+}
+
+input:checked + .slider:before {
+	transform: translateX(19px);
+}
+
+.setting-line > .sub-settings {
+	padding-left: 42px;
+	width: 100%;
+	display: block;
+}
+
+#settings .setting-line {
+	margin: 1.2em 0.6em;
+}
diff --git a/src/librustdoc/html/static/css/themes/ayu.css b/src/librustdoc/html/static/css/themes/ayu.css
new file mode 100644
index 000000000..c42cac59b
--- /dev/null
+++ b/src/librustdoc/html/static/css/themes/ayu.css
@@ -0,0 +1,563 @@
+/*
+Based off of the Ayu theme
+Original by Dempfi (https://github.com/dempfi/ayu)
+*/
+
+:root {
+	--main-background-color: #0f1419;
+	--main-color: #c5c5c5;
+	--settings-input-color: #ffb454;
+	--sidebar-background-color: #14191f;
+	--sidebar-background-color-hover: rgba(70, 70, 70, 0.33);
+	--code-block-background-color: #191f26;
+	--scrollbar-track-background-color: transparent;
+	--scrollbar-thumb-background-color: #5c6773;
+	--scrollbar-color: #5c6773 #24292f;
+	--headings-border-bottom-color: #5c6773;
+}
+
+.slider {
+	background-color: #ccc;
+}
+.slider:before {
+	background-color: white;
+}
+input:focus + .slider {
+	box-shadow: 0 0 0 2px #0a84ff, 0 0 0 6px rgba(10, 132, 255, 0.3);
+}
+
+h1, h2, h3, h4 {
+	color: white;
+}
+h1.fqn  a {
+	color: #fff;
+}
+h4 {
+	border: none;
+}
+
+.in-band {
+	background-color: #0f1419;
+}
+
+.docblock code {
+	color: #ffb454;
+}
+.code-header {
+	color: #e6e1cf;
+}
+.docblock pre > code, pre > code {
+	color: #e6e1cf;
+}
+span code {
+	color: #e6e1cf;
+}
+.docblock a > code {
+	color: #39AFD7 !important;
+}
+pre, .rustdoc.source .example-wrap {
+	color: #e6e1cf;
+}
+
+.rust-logo {
+	filter: drop-shadow(1px 0 0px #fff)
+		drop-shadow(0 1px 0 #fff)
+		drop-shadow(-1px 0 0 #fff)
+		drop-shadow(0 -1px 0 #fff);
+}
+
+.sidebar .current,
+.sidebar a:hover {
+	background-color: transparent;
+	color: #ffb44c;
+}
+
+.sidebar-elems .location {
+	color: #ff7733;
+}
+
+.line-numbers span { color: #5c6773; }
+.line-numbers .line-highlighted {
+	color: #708090;
+	background-color: rgba(255, 236, 164, 0.06);
+	padding-right: 4px;
+	border-right: 1px solid #ffb44c;
+}
+
+.docblock table td, .docblock table th {
+	border-color: #5c6773;
+}
+
+.search-results a:hover {
+	background-color: #777;
+}
+
+.search-results a:focus {
+	color: #000 !important;
+	background-color: #c6afb3;
+}
+.search-results a {
+	color: #0096cf;
+}
+.search-results a div.desc {
+	color: #c5c5c5;
+}
+
+.content .item-info::before { color: #ccc; }
+
+.content span.foreigntype, .content a.foreigntype { color: #ffa0a5; }
+.content span.union, .content a.union { color: #ffa0a5; }
+.content span.constant, .content a.constant,
+.content span.static, .content a.static { color: #39AFD7; }
+.content span.primitive, .content a.primitive { color: #ffa0a5; }
+.content span.traitalias, .content a.traitalias { color: #39AFD7; }
+.content span.keyword, .content a.keyword { color: #39AFD7; }
+
+.content span.externcrate, .content span.mod, .content a.mod {
+	color: #39AFD7;
+}
+.content span.struct, .content a.struct {
+	color: #ffa0a5;
+}
+.content span.enum, .content a.enum {
+	color: #ffa0a5;
+}
+.content span.trait, .content a.trait {
+	color: #39AFD7;
+}
+.content span.type, .content a.type {
+	color: #39AFD7;
+}
+.content span.type,
+.content a.type,
+.block a.current.type { color: #39AFD7; }
+.content span.associatedtype,
+.content a.associatedtype,
+.block a.current.associatedtype { color: #39AFD7; }
+.content span.fn, .content a.fn, .content span.method,
+.content a.method, .content span.tymethod,
+.content a.tymethod, .content .fnname {
+	color: #fdd687;
+}
+.content span.attr, .content a.attr, .content span.derive,
+.content a.derive, .content span.macro, .content a.macro {
+	color: #a37acc;
+}
+
+.sidebar a { color: #53b1db; }
+.sidebar a.current.type { color: #53b1db; }
+.sidebar a.current.associatedtype { color: #53b1db; }
+
+pre.rust .comment { color: #788797; }
+pre.rust .doccomment { color: #a1ac88; }
+
+nav.main .current {
+	border-top-color: #5c6773;
+	border-bottom-color: #5c6773;
+}
+nav.main .separator {
+	border: 1px solid #5c6773;
+}
+a {
+	color: #39AFD7;
+}
+
+.sidebar h2 a,
+.sidebar h3 a {
+	color: white;
+}
+.search-results a {
+	color: #0096cf;
+}
+body.source .example-wrap pre.rust a {
+	background: #333;
+}
+
+details.rustdoc-toggle > summary.hideme > span,
+details.rustdoc-toggle > summary::before {
+	color: #999;
+}
+
+details.rustdoc-toggle > summary::before {
+	filter: invert(100%);
+}
+
+#crate-search, .search-input {
+	background-color: #141920;
+	border-color: #424c57;
+}
+
+#crate-search {
+	/* Without the `!important`, the border-color is ignored for `<select>`...
+	   It cannot be in the group above because `.search-input` has a different border color on
+	   hover. */
+	border-color: #424c57 !important;
+}
+
+.search-input {
+	color: #ffffff;
+}
+
+.module-item .stab,
+.import-item .stab {
+	color: #000;
+}
+
+/* Created this empty rule to satisfy the theme checks. */
+.stab.empty-impl {}
+.stab.must_implement {}
+
+.stab.unstable,
+.stab.deprecated,
+.stab.portability,
+.stab.empty-impl,
+.stab.must_implement {
+	color: #c5c5c5;
+	background: #314559 !important;
+	border-style: none !important;
+	border-radius: 4px;
+	padding: 3px 6px 3px 6px;
+}
+
+.stab.portability > code {
+	color: #e6e1cf;
+	background: none;
+}
+
+.rightside,
+.out-of-band {
+	color: grey;
+}
+
+.result-name .primitive > i, .result-name .keyword > i {
+	color: #788797;
+}
+
+.line-numbers :target { background-color: transparent; }
+
+/* Code highlighting */
+pre.rust .number, pre.rust .string { color: #b8cc52; }
+pre.rust .kw, pre.rust .kw-2, pre.rust .prelude-ty,
+pre.rust .bool-val, pre.rust .prelude-val,
+pre.rust .op, pre.rust .lifetime { color: #ff7733; }
+pre.rust .macro, pre.rust .macro-nonterminal { color: #a37acc; }
+pre.rust .question-mark {
+	color: #ff9011;
+}
+pre.rust .self {
+	color: #36a3d9;
+	font-style: italic;
+}
+pre.rust .attribute {
+	color: #e6e1cf;
+}
+pre.rust .attribute .ident, pre.rust .attribute .op {
+	color: #e6e1cf;
+}
+
+.example-wrap > pre.line-number {
+	color: #5c67736e;
+	border: none;
+}
+
+a.test-arrow {
+	font-size: 100%;
+	color: #788797;
+	border-radius: 4px;
+	background-color: rgba(57, 175, 215, 0.09);
+}
+
+a.test-arrow:hover {
+	background-color: rgba(57, 175, 215, 0.368);
+	color: #c5c5c5;
+}
+
+.toggle-label,
+.code-attribute {
+	color: #999;
+}
+
+:target {
+	background: rgba(255, 236, 164, 0.06);
+	border-right: 3px solid rgba(255, 180, 76, 0.85);
+}
+
+pre.compile_fail {
+	border-left: 2px solid rgba(255,0,0,.4);
+}
+
+pre.compile_fail:hover, .information:hover + pre.compile_fail {
+	border-left: 2px solid #f00;
+}
+
+pre.should_panic {
+	border-left: 2px solid rgba(255,0,0,.4);
+}
+
+pre.should_panic:hover, .information:hover + pre.should_panic {
+	border-left: 2px solid #f00;
+}
+
+pre.ignore {
+	border-left: 2px solid rgba(255,142,0,.6);
+}
+
+pre.ignore:hover, .information:hover + pre.ignore {
+	border-left: 2px solid #ff9200;
+}
+
+.tooltip.compile_fail {
+	color: rgba(255,0,0,.5);
+}
+
+.information > .compile_fail:hover {
+	color: #f00;
+}
+
+.tooltip.should_panic {
+	color: rgba(255,0,0,.5);
+}
+
+.information > .should_panic:hover {
+	color: #f00;
+}
+
+.tooltip.ignore {
+	color: rgba(255,142,0,.6);
+}
+
+.information > .ignore:hover {
+	color: #ff9200;
+}
+
+.search-failed a {
+	color: #39AFD7;
+}
+
+.tooltip::after {
+	background-color: #314559;
+	color: #c5c5c5;
+	border: 1px solid #5c6773;
+}
+
+.tooltip::before {
+	border-color: transparent #314559 transparent transparent;
+}
+
+.notable-traits-tooltiptext {
+	background-color: #314559;
+	border-color: #5c6773;
+}
+
+.notable-traits-tooltiptext .notable {
+	border-bottom-color: #5c6773;
+}
+
+#titles > button.selected {
+	background-color: #141920 !important;
+	border-bottom: 1px solid #ffb44c !important;
+	border-top: none;
+}
+
+#titles > button:not(.selected) {
+	background-color: transparent !important;
+	border: none;
+}
+
+#titles > button:hover {
+	border-bottom: 1px solid rgba(242, 151, 24, 0.3);
+}
+
+#titles > button > div.count {
+	color: #888;
+}
+
+/* rules that this theme does not need to set, here to satisfy the rule checker */
+/* note that a lot of these are partially set in some way (meaning they are set
+individually rather than as a group) */
+/* FIXME: these rules should be at the bottom of the file but currently must be
+above the `@media (max-width: 700px)` rules due to a bug in the css checker */
+/* see https://github.com/rust-lang/rust/pull/71237#issuecomment-618170143 */
+.search-input:focus {}
+.content span.attr,.content a.attr,.block a.current.attr,.content span.derive,.content a.derive,
+.block a.current.derive,.content span.macro,.content a.macro,.block a.current.macro {}
+.content span.struct,.content a.struct,.block a.current.struct {}
+#titles>button:hover,#titles>button.selected {}
+.content span.typedef,.content a.typedef,.block a.current.typedef {}
+.content span.union,.content a.union,.block a.current.union {}
+pre.rust .lifetime {}
+.stab.unstable {}
+h2,
+h3:not(.impl):not(.method):not(.type):not(.tymethod), h4:not(.method):not(.type):not(.tymethod) {}
+.content span.enum,.content a.enum,.block a.current.enum {}
+.content span.constant,.content a.constant,.block a.current.constant,.content span.static,
+.content a.static, .block a.current.static {}
+.content span.keyword,.content a.keyword,.block a.current.keyword {}
+pre.rust .comment {}
+.content span.traitalias,.content a.traitalias,.block a.current.traitalias {}
+.content span.fn,.content a.fn,.block a.current.fn,.content span.method,.content a.method,
+.block a.current.method,.content span.tymethod,.content a.tymethod,.block a.current.tymethod,
+.content .fnname {}
+pre.rust .kw {}
+pre.rust .self,pre.rust .bool-val,pre.rust .prelude-val,pre.rust .attribute,
+pre.rust .attribute .ident {}
+.content span.foreigntype,.content a.foreigntype,.block a.current.foreigntype {}
+pre.rust .doccomment {}
+.stab.deprecated {}
+.content a.attr,.content a.derive,.content a.macro {}
+.stab.portability {}
+.content span.primitive,.content a.primitive,.block a.current.primitive {}
+.content span.externcrate,.content span.mod,.content a.mod,.block a.current.mod {}
+pre.rust .kw-2,pre.rust .prelude-ty {}
+.content span.trait,.content a.trait,.block a.current.trait {}
+
+.search-results a:focus span {}
+a.result-trait:focus {}
+a.result-traitalias:focus {}
+a.result-mod:focus,
+a.result-externcrate:focus {}
+a.result-mod:focus {}
+a.result-externcrate:focus {}
+a.result-enum:focus {}
+a.result-struct:focus {}
+a.result-union:focus {}
+a.result-fn:focus,
+a.result-method:focus,
+a.result-tymethod:focus {}
+a.result-type:focus {}
+a.result-associatedtype:focus {}
+a.result-foreigntype:focus {}
+a.result-attr:focus,
+a.result-derive:focus,
+a.result-macro:focus {}
+a.result-constant:focus,
+a.result-static:focus {}
+a.result-primitive:focus {}
+a.result-keyword:focus {}
+
+.sidebar a.current.enum {}
+.sidebar a.current.struct {}
+.sidebar a.current.foreigntype {}
+.sidebar a.current.attr,
+.sidebar a.current.derive,
+.sidebar a.current.macro {}
+.sidebar a.current.union {}
+.sidebar a.current.constant
+.sidebar a.current.static {}
+.sidebar a.current.primitive {}
+.sidebar a.current.externcrate
+.sidebar a.current.mod {}
+.sidebar a.current.trait {}
+.sidebar a.current.traitalias {}
+.sidebar a.current.fn,
+.sidebar a.current.method,
+.sidebar a.current.tymethod {}
+.sidebar a.current.keyword {}
+
+@media (max-width: 700px) {
+	.sidebar-elems {
+		border-right-color: #5c6773;
+	}
+}
+
+kbd {
+	color: #c5c5c5;
+	background-color: #314559;
+	border-color: #5c6773;
+	border-bottom-color: #5c6773;
+	box-shadow: inset 0 -1px 0 #5c6773;
+}
+
+#settings-menu > a, #help-button > button {
+	border-color: #5c6773;
+	background-color: #0f1419;
+	color: #fff;
+}
+
+#settings-menu > a img {
+	filter: invert(100);
+}
+
+.popover, .popover::before,
+#help-button span.top, #help-button span.bottom {
+	border-color: #5c6773;
+}
+
+#copy-path {
+	color: #fff;
+}
+#copy-path > img {
+	filter: invert(70%);
+}
+#copy-path:hover > img {
+	filter: invert(100%);
+}
+
+#settings-menu > a:hover, #settings-menu > a:focus,
+#help-button > button:hover, #help-button > button:focus {
+	border-color: #e0e0e0;
+}
+
+#theme-choices {
+	border-color: #5c6773;
+	background-color: #0f1419;
+}
+
+#theme-choices > button:not(:first-child) {
+	border-top-color: #5c6773;
+}
+
+#theme-choices > button:hover, #theme-choices > button:focus {
+	background-color: rgba(110, 110, 110, 0.33);
+}
+
+.search-results .result-name span.alias {
+	color: #c5c5c5;
+}
+.search-results .result-name span.grey {
+	color: #999;
+}
+
+#source-sidebar > .title {
+	color: #fff;
+	border-bottom-color: #5c6773;
+}
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
+	background-color: #14191f;
+	color: #ffb44c;
+}
+#source-sidebar div.files > a.selected {
+	background-color: #14191f;
+	color: #ffb44c;
+}
+
+.scraped-example-list .scrape-help {
+	border-color: #aaa;
+	color: #eee;
+}
+.scraped-example-list .scrape-help:hover {
+	border-color: white;
+	color: white;
+}
+.more-examples-toggle summary, .more-examples-toggle .hide-more {
+	color: #999;
+}
+.scraped-example .example-wrap .rust span.highlight {
+	background: rgb(91, 59, 1);
+}
+.scraped-example .example-wrap .rust span.highlight.focus {
+	background: rgb(124, 75, 15);
+}
+.scraped-example:not(.expanded) .code-wrapper:before {
+	background: linear-gradient(to bottom, rgba(15, 20, 25, 1), rgba(15, 20, 25, 0));
+}
+.scraped-example:not(.expanded) .code-wrapper:after {
+	background: linear-gradient(to top, rgba(15, 20, 25, 1), rgba(15, 20, 25, 0));
+}
+.toggle-line-inner {
+	background: #999;
+}
+.toggle-line:hover .toggle-line-inner {
+	background: #c5c5c5;
+}
diff --git a/src/librustdoc/html/static/css/themes/dark.css b/src/librustdoc/html/static/css/themes/dark.css
new file mode 100644
index 000000000..a550eb1c1
--- /dev/null
+++ b/src/librustdoc/html/static/css/themes/dark.css
@@ -0,0 +1,409 @@
+:root {
+	--main-background-color: #353535;
+	--main-color: #ddd;
+	--settings-input-color: #2196f3;
+	--sidebar-background-color: #505050;
+	--sidebar-background-color-hover: #676767;
+	--code-block-background-color: #2A2A2A;
+	--scrollbar-track-background-color: #717171;
+	--scrollbar-thumb-background-color: rgba(32, 34, 37, .6);
+	--scrollbar-color: rgba(32,34,37,.6) #5a5a5a;
+	--headings-border-bottom-color: #d2d2d2;
+}
+
+.slider {
+	background-color: #ccc;
+}
+.slider:before {
+	background-color: white;
+}
+input:focus + .slider {
+	box-shadow: 0 0 0 2px #0a84ff, 0 0 0 6px rgba(10, 132, 255, 0.3);
+}
+
+.in-band {
+	background-color: #353535;
+}
+
+.rust-logo {
+	filter: drop-shadow(1px 0 0px #fff)
+		drop-shadow(0 1px 0 #fff)
+		drop-shadow(-1px 0 0 #fff)
+		drop-shadow(0 -1px 0 #fff)
+}
+
+.sidebar .current,
+.sidebar a:hover {
+	background: #444;
+}
+
+.line-numbers span { color: #3B91E2; }
+.line-numbers .line-highlighted {
+	background-color: #0a042f !important;
+}
+
+.docblock table td, .docblock table th {
+	border-color: #ddd;
+}
+
+.search-results a:hover {
+	background-color: #777;
+}
+
+.search-results a:focus {
+	color: #eee !important;
+	background-color: #616161;
+}
+.search-results a:focus span { color: #eee !important; }
+a.result-trait:focus { background-color: #013191; }
+a.result-traitalias:focus { background-color: #013191; }
+a.result-mod:focus,
+a.result-externcrate:focus { background-color: #884719; }
+a.result-enum:focus { background-color: #194e9f; }
+a.result-struct:focus { background-color: #194e9f; }
+a.result-union:focus { background-color: #194e9f; }
+a.result-fn:focus,
+a.result-method:focus,
+a.result-tymethod:focus { background-color: #4950ed; }
+a.result-type:focus { background-color: #194e9f; }
+a.result-associatedtype:focus { background-color: #884719; }
+a.result-foreigntype:focus { background-color: #194e9f; }
+a.result-attr:focus,
+a.result-derive:focus,
+a.result-macro:focus { background-color: #217d1c; }
+a.result-constant:focus,
+a.result-static:focus { background-color: #884719; }
+a.result-primitive:focus { background-color: #194e9f; }
+a.result-keyword:focus { background-color: #884719; }
+
+.content .item-info::before { color: #ccc; }
+
+.content span.enum, .content a.enum, .block a.current.enum { color: #2dbfb8; }
+.content span.struct, .content a.struct, .block a.current.struct { color: #2dbfb8; }
+.content span.type, .content a.type, .block a.current.type { color: #2dbfb8; }
+.content span.associatedtype,
+.content a.associatedtype,
+.block a.current.associatedtype { color: #D2991D; }
+.content span.foreigntype, .content a.foreigntype, .block a.current.foreigntype { color: #2dbfb8; }
+.content span.attr, .content a.attr, .block a.current.attr,
+.content span.derive, .content a.derive, .block a.current.derive,
+.content span.macro, .content a.macro, .block a.current.macro { color: #09bd00; }
+.content span.union, .content a.union, .block a.current.union { color: #2dbfb8; }
+.content span.constant, .content a.constant, .block a.current.constant,
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+.sidebar a.current.keyword { color: #fdbf35; }
+
+pre.rust .comment { color: #8d8d8b; }
+pre.rust .doccomment { color: #8ca375; }
+
+nav.main .current {
+	border-top-color: #eee;
+	border-bottom-color: #eee;
+}
+nav.main .separator {
+	border-color: #eee;
+}
+
+a {
+	color: #D2991D;
+}
+
+body.source .example-wrap pre.rust a {
+	background: #333;
+}
+
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+	color: #999;
+}
+
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+	filter: invert(100%);
+}
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+#crate-search, .search-input {
+	color: #111;
+	background-color: #f0f0f0;
+	border-color: #f0f0f0;
+}
+
+#crate-search {
+	/* Without the `!important`, the border-color is ignored for `<select>`...
+	   It cannot be in the group above because `.search-input` has a different border color on
+	   hover. */
+	border-color: #f0f0f0 !important;
+}
+
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+	border-color: #e0e0e0;
+}
+
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+}
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+.stab.portability > code { background: none; }
+
+.rightside,
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+	color: grey;
+}
+
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+
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+pre.rust .kw-2, pre.rust .prelude-ty { color: #769acb; }
+pre.rust .number, pre.rust .string { color: #83a300; }
+pre.rust .self, pre.rust .bool-val, pre.rust .prelude-val,
+pre.rust .attribute, pre.rust .attribute .ident { color: #ee6868; }
+pre.rust .macro, pre.rust .macro-nonterminal { color: #3E999F; }
+pre.rust .lifetime { color: #d97f26; }
+pre.rust .question-mark {
+	color: #ff9011;
+}
+
+.example-wrap > pre.line-number {
+	border-color: #4a4949;
+}
+
+a.test-arrow {
+	color: #dedede;
+	background-color: rgba(78, 139, 202, 0.2);
+}
+
+a.test-arrow:hover{
+	background-color: #4e8bca;
+}
+
+.toggle-label,
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+	color: #999;
+}
+
+:target {
+	background-color: #494a3d;
+	border-right: 3px solid #bb7410;
+}
+
+pre.compile_fail {
+	border-left: 2px solid rgba(255,0,0,.8);
+}
+
+pre.compile_fail:hover, .information:hover + pre.compile_fail {
+	border-left: 2px solid #f00;
+}
+
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+	border-left: 2px solid rgba(255,0,0,.8);
+}
+
+pre.should_panic:hover, .information:hover + pre.should_panic {
+	border-left: 2px solid #f00;
+}
+
+pre.ignore {
+	border-left: 2px solid rgba(255,142,0,.6);
+}
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+	border-left: 2px solid #ff9200;
+}
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+	color: rgba(255,0,0,.8);
+}
+
+.information > .compile_fail:hover {
+	color: #f00;
+}
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+	color: rgba(255,0,0,.8);
+}
+
+.information > .should_panic:hover {
+	color: #f00;
+}
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+	color: rgba(255,142,0,.6);
+}
+
+.information > .ignore:hover {
+	color: #ff9200;
+}
+
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+	color: #0089ff;
+}
+
+.tooltip::after {
+	background-color: #000;
+	color: #fff;
+	border-color: #000;
+}
+
+.tooltip::before {
+	border-color: transparent black transparent transparent;
+}
+
+.notable-traits-tooltiptext {
+	background-color: #111;
+	border-color: #777;
+}
+
+.notable-traits-tooltiptext .notable {
+	border-bottom-color: #d2d2d2;
+}
+
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+	background-color: #252525;
+	border-top-color: #252525;
+}
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+	border-top-color: #0089ff;
+	background-color: #353535;
+}
+
+#titles > button > div.count {
+	color: #888;
+}
+
+@media (max-width: 700px) {
+	.sidebar-elems {
+		border-right-color: #000;
+	}
+}
+
+kbd {
+	color: #000;
+	background-color: #fafbfc;
+	border-color: #d1d5da;
+	border-bottom-color: #c6cbd1;
+	box-shadow: inset 0 -1px 0 #c6cbd1;
+}
+
+#settings-menu > a, #help-button > button {
+	border-color: #e0e0e0;
+	background: #f0f0f0;
+	color: #000;
+}
+
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+#help-button > button:hover, #help-button > button:focus {
+	border-color: #ffb900;
+}
+
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+	border-color: #d2d2d2;
+}
+
+#copy-path {
+	color: #999;
+}
+#copy-path > img {
+	filter: invert(50%);
+}
+#copy-path:hover > img {
+	filter: invert(65%);
+}
+
+#theme-choices {
+	border-color: #e0e0e0;
+	background-color: #353535;
+}
+
+#theme-choices > button:not(:first-child) {
+	border-top-color: #e0e0e0;
+}
+
+#theme-choices > button:hover, #theme-choices > button:focus {
+	background-color: #4e4e4e;
+}
+
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+	color: #fff;
+}
+.search-results .result-name span.grey {
+	color: #ccc;
+}
+
+#source-sidebar > .title {
+	border-bottom-color: #ccc;
+}
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
+	background-color: #444;
+}
+#source-sidebar div.files > a.selected {
+	background-color: #333;
+}
+
+.scraped-example-list .scrape-help {
+	border-color: #aaa;
+	color: #eee;
+}
+.scraped-example-list .scrape-help:hover {
+	border-color: white;
+	color: white;
+}
+.more-examples-toggle summary, .more-examples-toggle .hide-more {
+	color: #999;
+}
+.scraped-example .example-wrap .rust span.highlight {
+	background: rgb(91, 59, 1);
+}
+.scraped-example .example-wrap .rust span.highlight.focus {
+	background: rgb(124, 75, 15);
+}
+.scraped-example:not(.expanded) .code-wrapper:before {
+	background: linear-gradient(to bottom, rgba(53, 53, 53, 1), rgba(53, 53, 53, 0));
+}
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+	background: linear-gradient(to top, rgba(53, 53, 53, 1), rgba(53, 53, 53, 0));
+}
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+	background: #999;
+}
+.toggle-line:hover .toggle-line-inner {
+	background: #c5c5c5;
+}
diff --git a/src/librustdoc/html/static/css/themes/light.css b/src/librustdoc/html/static/css/themes/light.css
new file mode 100644
index 000000000..b751acff1
--- /dev/null
+++ b/src/librustdoc/html/static/css/themes/light.css
@@ -0,0 +1,395 @@
+:root {
+	--main-background-color: white;
+	--main-color: black;
+	--settings-input-color: #2196f3;
+	--sidebar-background-color: #F5F5F5;
+	--sidebar-background-color-hover: #E0E0E0;
+	--code-block-background-color: #F5F5F5;
+	--scrollbar-track-background-color: #dcdcdc;
+	--scrollbar-thumb-background-color: rgba(36, 37, 39, 0.6);
+	--scrollbar-color: rgba(36, 37, 39, 0.6) #d9d9d9;
+	--headings-border-bottom-color: #ddd;
+}
+
+.slider {
+	background-color: #ccc;
+}
+.slider:before {
+	background-color: white;
+}
+input:focus + .slider {
+	box-shadow: 0 0 0 2px #0a84ff, 0 0 0 6px rgba(10, 132, 255, 0.3);
+}
+
+.in-band {
+	background-color: white;
+}
+
+.rust-logo {
+	/* This rule exists to force other themes to explicitly style the logo.
+	 * Rustdoc has a custom linter for this purpose.
+	 */
+}
+
+.sidebar .current,
+.sidebar a:hover {
+	background-color: #fff;
+}
+
+.line-numbers span { color: #c67e2d; }
+.line-numbers .line-highlighted {
+	background-color: #FDFFD3 !important;
+}
+
+.docblock table td, .docblock table th {
+	border-color: #ddd;
+}
+
+.search-results a:hover {
+	background-color: #ddd;
+}
+
+.search-results a:focus {
+	color: #000 !important;
+	background-color: #ccc;
+}
+.search-results a:focus span { color: #000 !important; }
+a.result-trait:focus { background-color: #c7b6ff; }
+a.result-traitalias:focus { background-color: #c7b6ff; }
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+a.result-associatedtype:focus { background-color: #afc6e4; }
+a.result-foreigntype:focus { background-color: #e7b1a0; }
+a.result-attr:focus,
+a.result-derive:focus,
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+a.result-primitive:focus { background-color: #e7b1a0; }
+a.result-keyword:focus { background-color: #afc6e4; }
+
+.content .item-info::before { color: #ccc; }
+
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+
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+
+nav.main .current {
+	border-top-color: #000;
+	border-bottom-color: #000;
+}
+nav.main .separator {
+	border: 1px solid #000;
+}
+
+a {
+	color: #3873AD;
+}
+
+body.source .example-wrap pre.rust a {
+	background: #eee;
+}
+
+details.rustdoc-toggle > summary.hideme > span,
+details.rustdoc-toggle > summary::before {
+	color: #999;
+}
+
+#crate-search, .search-input {
+	background-color: white;
+	border-color: #e0e0e0;
+}
+
+#crate-search {
+	/* Without the `!important`, the border-color is ignored for `<select>`...
+	   It cannot be in the group above because `.search-input` has a different border color on
+	   hover. */
+	border-color: #e0e0e0 !important;
+}
+
+.search-input:focus {
+	border-color: #66afe9;
+}
+
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+.stab.portability > code { background: none; }
+
+.rightside,
+.out-of-band {
+	color: grey;
+}
+
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+
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+pre.rust .kw-2, pre.rust .prelude-ty { color: #4271AE; }
+pre.rust .number, pre.rust .string { color: #718C00; }
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+pre.rust .comment { color: #8E908C; }
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+pre.rust .lifetime { color: #B76514; }
+pre.rust .question-mark {
+	color: #ff9011;
+}
+
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+	border-color: #c7c7c7;
+}
+
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+	color: #f5f5f5;
+	background-color: rgba(78, 139, 202, 0.2);
+}
+
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+	background-color: #4e8bca;
+}
+
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+	color: #999;
+}
+
+:target {
+	background: #FDFFD3;
+	border-right: 3px solid #AD7C37;
+}
+
+pre.compile_fail {
+	border-left: 2px solid rgba(255,0,0,.5);
+}
+
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+	border-left: 2px solid #f00;
+}
+
+pre.should_panic {
+	border-left: 2px solid rgba(255,0,0,.5);
+}
+
+pre.should_panic:hover, .information:hover + pre.should_panic {
+	border-left: 2px solid #f00;
+}
+
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+	border-left: 2px solid rgba(255,142,0,.6);
+}
+
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+	border-left: 2px solid #ff9200;
+}
+
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+	color: rgba(255,0,0,.5);
+}
+
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+}
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+	color: rgba(255,0,0,.5);
+}
+
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+	color: #f00;
+}
+
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+	color: rgba(255,142,0,.6);
+}
+
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+	color: #ff9200;
+}
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+	color: #3873AD;
+}
+
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+	background-color: #000;
+	color: #fff;
+}
+
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+}
+
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+	background-color: #eee;
+	border-color: #999;
+}
+
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+	border-bottom-color: #DDDDDD;
+}
+
+#titles > button:not(.selected) {
+	background-color: #e6e6e6;
+	border-top-color: #e6e6e6;
+}
+
+#titles > button:hover, #titles > button.selected {
+	background-color: #ffffff;
+	border-top-color: #0089ff;
+}
+
+#titles > button > div.count {
+	color: #888;
+}
+
+@media (max-width: 700px) {
+	.sidebar-elems {
+		border-right-color: #000;
+	}
+}
+
+kbd {
+	color: #000;
+	background-color: #fafbfc;
+	border-color: #d1d5da;
+	border-bottom-color: #c6cbd1;
+	box-shadow: inset 0 -1px 0 #c6cbd1;
+}
+
+#settings-menu > a, #help-button > button {
+	border-color: #e0e0e0;
+	background-color: #fff;
+}
+
+#settings-menu > a:hover, #settings-menu > a:focus,
+#help-button > button:hover, #help-button > button:focus {
+	border-color: #717171;
+}
+
+.popover, .popover::before,
+#help-button span.top, #help-button span.bottom {
+	border-color: #DDDDDD;
+}
+
+#copy-path {
+	color: #999;
+}
+#copy-path > img {
+	filter: invert(50%);
+}
+#copy-path:hover > img {
+	filter: invert(35%);
+}
+
+#theme-choices {
+	border-color: #ccc;
+	background-color: #fff;
+}
+
+#theme-choices > button:not(:first-child) {
+	border-top-color: #e0e0e0;
+}
+
+#theme-choices > button:hover, #theme-choices > button:focus {
+	background-color: #eee;
+}
+
+.search-results .result-name span.alias {
+	color: #000;
+}
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+	color: #999;
+}
+
+#source-sidebar > .title {
+	border-bottom-color: #ccc;
+}
+#source-sidebar div.files > a:hover, details.dir-entry summary:hover,
+#source-sidebar div.files > a:focus, details.dir-entry summary:focus {
+	background-color: #E0E0E0;
+}
+#source-sidebar div.files > a.selected {
+	background-color: #fff;
+}
+.scraped-example-list .scrape-help {
+	border-color: #555;
+	color: #333;
+}
+.scraped-example-list .scrape-help:hover {
+	border-color: black;
+	color: black;
+}
+.more-examples-toggle summary, .more-examples-toggle .hide-more {
+	color: #999;
+}
+.scraped-example .example-wrap .rust span.highlight {
+	background: #fcffd6;
+}
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+	background: #f6fdb0;
+}
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+	background: linear-gradient(to bottom, rgba(255, 255, 255, 1), rgba(255, 255, 255, 0));
+}
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+	background: linear-gradient(to top, rgba(255, 255, 255, 1), rgba(255, 255, 255, 0));
+}
+.toggle-line-inner {
+	background: #ccc;
+}
+.toggle-line:hover .toggle-line-inner {
+	background: #999;
+}
diff --git a/src/librustdoc/html/static/fonts/FiraSans-LICENSE.txt b/src/librustdoc/html/static/fonts/FiraSans-LICENSE.txt
new file mode 100644
index 000000000..ff9afab06
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/FiraSans-LICENSE.txt
@@ -0,0 +1,94 @@
+Digitized data copyright (c) 2012-2015, The Mozilla Foundation and Telefonica S.A.
+with Reserved Font Name < Fira >,
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/src/librustdoc/html/static/fonts/FiraSans-Medium.woff2 b/src/librustdoc/html/static/fonts/FiraSans-Medium.woff2
new file mode 100644
index 000000000..7a1e5fc54
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/FiraSans-Medium.woff2
diff --git a/src/librustdoc/html/static/fonts/FiraSans-Regular.woff2 b/src/librustdoc/html/static/fonts/FiraSans-Regular.woff2
new file mode 100644
index 000000000..e766e06cc
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/FiraSans-Regular.woff2
diff --git a/src/librustdoc/html/static/fonts/NanumBarunGothic-LICENSE.txt b/src/librustdoc/html/static/fonts/NanumBarunGothic-LICENSE.txt
new file mode 100644
index 000000000..0bf46682b
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/NanumBarunGothic-LICENSE.txt
@@ -0,0 +1,99 @@
+Copyright (c) 2010, NAVER Corporation (https://www.navercorp.com/),
+
+with Reserved Font Name Nanum, Naver Nanum, NanumGothic, Naver NanumGothic,
+NanumMyeongjo, Naver NanumMyeongjo, NanumBrush, Naver NanumBrush, NanumPen,
+Naver NanumPen, Naver NanumGothicEco, NanumGothicEco, Naver NanumMyeongjoEco,
+NanumMyeongjoEco, Naver NanumGothicLight, NanumGothicLight, NanumBarunGothic,
+Naver NanumBarunGothic, NanumSquareRound, NanumBarunPen, MaruBuri
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/src/librustdoc/html/static/fonts/NanumBarunGothic.ttf.woff2 b/src/librustdoc/html/static/fonts/NanumBarunGothic.ttf.woff2
new file mode 100644
index 000000000..1866ad4bc
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/NanumBarunGothic.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceCodePro-It.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceCodePro-It.ttf.woff2
new file mode 100644
index 000000000..462c34efc
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceCodePro-It.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceCodePro-LICENSE.txt b/src/librustdoc/html/static/fonts/SourceCodePro-LICENSE.txt
new file mode 100644
index 000000000..07542572e
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceCodePro-LICENSE.txt
@@ -0,0 +1,93 @@
+Copyright 2010, 2012 Adobe Systems Incorporated (http://www.adobe.com/), with Reserved Font Name 'Source'. All Rights Reserved. Source is a trademark of Adobe Systems Incorporated in the United States and/or other countries.
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+
+This license is copied below, and is also available with a FAQ at: http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/src/librustdoc/html/static/fonts/SourceCodePro-Regular.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceCodePro-Regular.ttf.woff2
new file mode 100644
index 000000000..10b558e0b
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceCodePro-Regular.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceCodePro-Semibold.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceCodePro-Semibold.ttf.woff2
new file mode 100644
index 000000000..5ec64eef0
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceCodePro-Semibold.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceSerif4-Bold.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceSerif4-Bold.ttf.woff2
new file mode 100644
index 000000000..db57d2145
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceSerif4-Bold.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceSerif4-It.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceSerif4-It.ttf.woff2
new file mode 100644
index 000000000..1cbc021a3
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceSerif4-It.ttf.woff2
diff --git a/src/librustdoc/html/static/fonts/SourceSerif4-LICENSE.md b/src/librustdoc/html/static/fonts/SourceSerif4-LICENSE.md
new file mode 100644
index 000000000..68ea18924
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceSerif4-LICENSE.md
@@ -0,0 +1,93 @@
+Copyright 2014-2021 Adobe (http://www.adobe.com/), with Reserved Font Name 'Source'. All Rights Reserved. Source is a trademark of Adobe in the United States and/or other countries.
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+
+This license is copied below, and is also available with a FAQ at: http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/src/librustdoc/html/static/fonts/SourceSerif4-Regular.ttf.woff2 b/src/librustdoc/html/static/fonts/SourceSerif4-Regular.ttf.woff2
new file mode 100644
index 000000000..2db73fe2b
--- /dev/null
+++ b/src/librustdoc/html/static/fonts/SourceSerif4-Regular.ttf.woff2
diff --git a/src/librustdoc/html/static/images/clipboard.svg b/src/librustdoc/html/static/images/clipboard.svg
new file mode 100644
index 000000000..8adbd9963
--- /dev/null
+++ b/src/librustdoc/html/static/images/clipboard.svg
@@ -0,0 +1 @@
+<svg width="24" height="25" viewBox="0 0 24 25" xmlns="http://www.w3.org/2000/svg" aria-label="Copy to clipboard"><path d="M18 20h2v3c0 1-1 2-2 2H2c-.998 0-2-1-2-2V5c0-.911.755-1.667 1.667-1.667h5A3.323 3.323 0 0110 0a3.323 3.323 0 013.333 3.333h5C19.245 3.333 20 4.09 20 5v8.333h-2V9H2v14h16v-3zM3 7h14c0-.911-.793-1.667-1.75-1.667H13.5c-.957 0-1.75-.755-1.75-1.666C11.75 2.755 10.957 2 10 2s-1.75.755-1.75 1.667c0 .911-.793 1.666-1.75 1.666H4.75C3.793 5.333 3 6.09 3 7z"/><path d="M4 19h6v2H4zM12 11H4v2h8zM4 17h4v-2H4zM15 15v-3l-4.5 4.5L15 21v-3l8.027-.032L23 15z"/></svg>
diff --git a/src/librustdoc/html/static/images/down-arrow.svg b/src/librustdoc/html/static/images/down-arrow.svg
new file mode 100644
index 000000000..35437e77a
--- /dev/null
+++ b/src/librustdoc/html/static/images/down-arrow.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" id="Layer_1" width="128" height="128" enable-background="new 0 0 128 128" version="1.1" viewBox="-30 -20 176 176" xml:space="preserve"><g><line x1="111" x2="64" y1="40.5" y2="87.499" fill="none" stroke="#2F3435" stroke-linecap="square" stroke-miterlimit="10" stroke-width="12"/><line x1="64" x2="17" y1="87.499" y2="40.5" fill="none" stroke="#2F3435" stroke-linecap="square" stroke-miterlimit="10" stroke-width="12"/></g></svg>
\ No newline at end of file
diff --git a/src/librustdoc/html/static/images/favicon-16x16.png b/src/librustdoc/html/static/images/favicon-16x16.png
new file mode 100644
index 000000000..ea4b45cae
--- /dev/null
+++ b/src/librustdoc/html/static/images/favicon-16x16.png
diff --git a/src/librustdoc/html/static/images/favicon-32x32.png b/src/librustdoc/html/static/images/favicon-32x32.png
new file mode 100644
index 000000000..69b8613ce
--- /dev/null
+++ b/src/librustdoc/html/static/images/favicon-32x32.png
diff --git a/src/librustdoc/html/static/images/favicon.svg b/src/librustdoc/html/static/images/favicon.svg
new file mode 100644
index 000000000..8b34b5119
--- /dev/null
+++ b/src/librustdoc/html/static/images/favicon.svg
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg width="100%" height="100%" viewBox="0 0 32 32" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" xmlns:serif="http://www.serif.com/" style="fill-rule:evenodd;clip-rule:evenodd;stroke-linecap:round;stroke-linejoin:round;">
+<defs>
+  <style type="text/css"><![CDATA[
+    #logo {
+      fill-rule: nonzero;
+    }
+    #logo-teeth {
+      stroke: #000000;
+      stroke-width: 0.92px;
+    }
+    @media (prefers-color-scheme: dark) {
+      #logo {
+        fill: #FFFFFF;
+        fill-rule: nonzero;
+      }
+      #logo-teeth {
+        fill: #FFFFFF;
+        stroke: #FFFFFF;
+        stroke-width: 0.92px;
+      }
+    }
+  ]]></style>
+</defs>
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diff --git a/src/librustdoc/html/static/images/rust-logo.svg b/src/librustdoc/html/static/images/rust-logo.svg
new file mode 100644
index 000000000..62424d8ff
--- /dev/null
+++ b/src/librustdoc/html/static/images/rust-logo.svg
@@ -0,0 +1,61 @@
+<svg version="1.1" height="106" width="106" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="logo" transform="translate(53, 53)">
+  <path id="r" transform="translate(0.5, 0.5)" stroke="black" stroke-width="1" stroke-linejoin="round" d="
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+    V 3 H 34 V 5 C 34,13 25,12 24,7 C 23,2 19,-2 18,-2 C 33,-10 24,-26 12,-26 H -35
+    V -15 H -25 V 11 H -40 Z" />
+  <g id="gear" mask="url(#holes)">
+    <circle r="43" fill="none" stroke="black" stroke-width="9" />
+    <g id="cogs">
+      <polygon id="cog" stroke="black" stroke-width="3" stroke-linejoin="round" points="46,3 51,0 46,-3" />
+      <use xlink:href="#cog" transform="rotate(11.25)" />
+      <use xlink:href="#cog" transform="rotate(22.50)" />
+      <use xlink:href="#cog" transform="rotate(33.75)" />
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+      <use xlink:href="#cog" transform="rotate(326.25)" />
+      <use xlink:href="#cog" transform="rotate(337.50)" />
+      <use xlink:href="#cog" transform="rotate(348.75)" />
+    </g>
+    <g id="mounts">
+      <polygon id="mount" stroke="black" stroke-width="6" stroke-linejoin="round" points="-7,-42 0,-35 7,-42" />
+      <use xlink:href="#mount" transform="rotate(72)" />
+      <use xlink:href="#mount" transform="rotate(144)" />
+      <use xlink:href="#mount" transform="rotate(216)" />
+      <use xlink:href="#mount" transform="rotate(288)" />
+    </g>
+  </g>
+  <mask id="holes">
+    <rect x="-60" y="-60" width="120" height="120" fill="white"/>
+    <circle id="hole" cy="-40" r="3" />
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+    <use xlink:href="#hole" transform="rotate(288)" />
+  </mask>
+</g>
+</svg>
diff --git a/src/librustdoc/html/static/images/toggle-minus.svg b/src/librustdoc/html/static/images/toggle-minus.svg
new file mode 100644
index 000000000..73154788a
--- /dev/null
+++ b/src/librustdoc/html/static/images/toggle-minus.svg
@@ -0,0 +1 @@
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new file mode 100644
index 000000000..08b17033e
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+++ b/src/librustdoc/html/static/images/toggle-plus.svg
@@ -0,0 +1 @@
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new file mode 100644
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@@ -0,0 +1 @@
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diff --git a/src/librustdoc/html/static/js/README.md b/src/librustdoc/html/static/js/README.md
new file mode 100644
index 000000000..1fd859ad7
--- /dev/null
+++ b/src/librustdoc/html/static/js/README.md
@@ -0,0 +1,15 @@
+# Rustdoc JS
+
+These JavaScript files are incorporated into the rustdoc binary at build time,
+and are minified and written to the filesystem as part of the doc build process.
+
+We use the [Closure Compiler](https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler)
+dialect of JSDoc to comment our code and annotate params and return types.
+To run a check:
+
+    ./x.py doc library/std
+    npm i -g google-closure-compiler
+    google-closure-compiler -W VERBOSE \
+      build/<YOUR PLATFORM>/doc/{search-index*.js,crates*.js} \
+      src/librustdoc/html/static/js/{search.js,main.js,storage.js} \
+      --externs src/librustdoc/html/static/js/externs.js >/dev/null
diff --git a/src/librustdoc/html/static/js/externs.js b/src/librustdoc/html/static/js/externs.js
new file mode 100644
index 000000000..ecbe15a59
--- /dev/null
+++ b/src/librustdoc/html/static/js/externs.js
@@ -0,0 +1,142 @@
+// This file contains type definitions that are processed by the Closure Compiler but are
+// not put into the JavaScript we include as part of the documentation. It is used for
+// type checking. See README.md in this directory for more info.
+
+/* eslint-disable */
+let searchState;
+function initSearch(searchIndex){}
+
+/**
+ * @typedef {{
+ *     name: string,
+ *     fullPath: Array<string>,
+ *     pathWithoutLast: Array<string>,
+ *     pathLast: string,
+ *     generics: Array<QueryElement>,
+ * }}
+ */
+let QueryElement;
+
+/**
+ * @typedef {{
+ *      pos: number,
+ *      totalElems: number,
+ *      typeFilter: (null|string),
+ *      userQuery: string,
+ * }}
+ */
+let ParserState;
+
+/**
+ * @typedef {{
+ *     original: string,
+ *     userQuery: string,
+ *     typeFilter: number,
+ *     elems: Array<QueryElement>,
+ *     args: Array<QueryElement>,
+ *     returned: Array<QueryElement>,
+ *     foundElems: number,
+ * }}
+ */
+let ParsedQuery;
+
+/**
+ * @typedef {{
+ *    crate: string,
+ *    desc: string,
+ *    id: number,
+ *    name: string,
+ *    normalizedName: string,
+ *    parent: (Object|null|undefined),
+ *    path: string,
+ *    ty: (Number|null|number),
+ *    type: (Array<?>|null)
+ * }}
+ */
+let Row;
+
+/**
+ * @typedef {{
+ *    in_args: Array<Object>,
+ *    returned: Array<Object>,
+ *    others: Array<Object>,
+ *    query: ParsedQuery,
+ * }}
+ */
+let ResultsTable;
+
+/**
+ * @typedef {{
+ *     desc: string,
+ *     displayPath: string,
+ *     fullPath: string,
+ *     href: string,
+ *     id: number,
+ *     lev: number,
+ *     name: string,
+ *     normalizedName: string,
+ *     parent: (Object|undefined),
+ *     path: string,
+ *     ty: number,
+ * }}
+ */
+let Results;
+
+/**
+ * A pair of [inputs, outputs], or 0 for null. This is stored in the search index.
+ * The JavaScript deserializes this into FunctionSearchType.
+ *
+ * Numeric IDs are *ONE-indexed* into the paths array (`p`). Zero is used as a sentinel for `null`
+ * because `null` is four bytes while `0` is one byte.
+ *
+ * An input or output can be encoded as just a number if there is only one of them, AND
+ * it has no generics. The no generics rule exists to avoid ambiguity: imagine if you had
+ * a function with a single output, and that output had a single generic:
+ *
+ *     fn something() -> Result<usize, usize>
+ *
+ * If output was allowed to be any RawFunctionType, it would look like this
+ *
+ *     [[], [50, [3, 3]]]
+ *
+ * The problem is that the above output could be interpreted as either a type with ID 50 and two
+ * generics, or it could be interpreted as a pair of types, the first one with ID 50 and the second
+ * with ID 3 and a single generic parameter that is also ID 3. We avoid this ambiguity by choosing
+ * in favor of the pair of types interpretation. This is why the `(number|Array<RawFunctionType>)`
+ * is used instead of `(RawFunctionType|Array<RawFunctionType>)`.
+ *
+ * @typedef {(
+ *     0 |
+ *     [(number|Array<RawFunctionType>)] |
+ *     [(number|Array<RawFunctionType>), (number|Array<RawFunctionType>)]
+ * )}
+ */
+let RawFunctionSearchType;
+
+/**
+ * A single function input or output type. This is either a single path ID, or a pair of
+ * [path ID, generics].
+ *
+ * Numeric IDs are *ONE-indexed* into the paths array (`p`). Zero is used as a sentinel for `null`
+ * because `null` is four bytes while `0` is one byte.
+ *
+ * @typedef {number | [number, Array<RawFunctionType>]}
+ */
+let RawFunctionType;
+
+/**
+ * @typedef {{
+ *     inputs: Array<FunctionType>,
+ *     outputs: Array<FunctionType>,
+ * }}
+ */
+let FunctionSearchType;
+
+/**
+ * @typedef {{
+ *     name: (null|string),
+ *     ty: (null|number),
+ *     generics: Array<FunctionType>,
+ * }}
+ */
+let FunctionType;
diff --git a/src/librustdoc/html/static/js/main.js b/src/librustdoc/html/static/js/main.js
new file mode 100644
index 000000000..0702b2b0b
--- /dev/null
+++ b/src/librustdoc/html/static/js/main.js
@@ -0,0 +1,974 @@
+// Local js definitions:
+/* global addClass, getSettingValue, hasClass, searchState */
+/* global onEach, onEachLazy, removeClass */
+
+"use strict";
+
+// Get a value from the rustdoc-vars div, which is used to convey data from
+// Rust to the JS. If there is no such element, return null.
+function getVar(name) {
+    const el = document.getElementById("rustdoc-vars");
+    if (el) {
+        return el.attributes["data-" + name].value;
+    } else {
+        return null;
+    }
+}
+
+// Given a basename (e.g. "storage") and an extension (e.g. ".js"), return a URL
+// for a resource under the root-path, with the resource-suffix.
+function resourcePath(basename, extension) {
+    return getVar("root-path") + basename + getVar("resource-suffix") + extension;
+}
+
+function hideMain() {
+    addClass(document.getElementById(MAIN_ID), "hidden");
+}
+
+function showMain() {
+    removeClass(document.getElementById(MAIN_ID), "hidden");
+}
+
+function elemIsInParent(elem, parent) {
+    while (elem && elem !== document.body) {
+        if (elem === parent) {
+            return true;
+        }
+        elem = elem.parentElement;
+    }
+    return false;
+}
+
+function blurHandler(event, parentElem, hideCallback) {
+    if (!elemIsInParent(document.activeElement, parentElem) &&
+        !elemIsInParent(event.relatedTarget, parentElem)
+    ) {
+        hideCallback();
+    }
+}
+
+(function() {
+    window.rootPath = getVar("root-path");
+    window.currentCrate = getVar("current-crate");
+}());
+
+function setMobileTopbar() {
+    // FIXME: It would be nicer to generate this text content directly in HTML,
+    // but with the current code it's hard to get the right information in the right place.
+    const mobileLocationTitle = document.querySelector(".mobile-topbar h2.location");
+    const locationTitle = document.querySelector(".sidebar h2.location");
+    if (mobileLocationTitle && locationTitle) {
+        mobileLocationTitle.innerHTML = locationTitle.innerHTML;
+    }
+}
+
+// Gets the human-readable string for the virtual-key code of the
+// given KeyboardEvent, ev.
+//
+// This function is meant as a polyfill for KeyboardEvent#key,
+// since it is not supported in IE 11 or Chrome for Android. We also test for
+// KeyboardEvent#keyCode because the handleShortcut handler is
+// also registered for the keydown event, because Blink doesn't fire
+// keypress on hitting the Escape key.
+//
+// So I guess you could say things are getting pretty interoperable.
+function getVirtualKey(ev) {
+    if ("key" in ev && typeof ev.key !== "undefined") {
+        return ev.key;
+    }
+
+    const c = ev.charCode || ev.keyCode;
+    if (c === 27) {
+        return "Escape";
+    }
+    return String.fromCharCode(c);
+}
+
+const MAIN_ID = "main-content";
+const SETTINGS_BUTTON_ID = "settings-menu";
+const ALTERNATIVE_DISPLAY_ID = "alternative-display";
+const NOT_DISPLAYED_ID = "not-displayed";
+const HELP_BUTTON_ID = "help-button";
+
+function getSettingsButton() {
+    return document.getElementById(SETTINGS_BUTTON_ID);
+}
+
+function getHelpButton() {
+    return document.getElementById(HELP_BUTTON_ID);
+}
+
+// Returns the current URL without any query parameter or hash.
+function getNakedUrl() {
+    return window.location.href.split("?")[0].split("#")[0];
+}
+
+/**
+ * This function inserts `newNode` after `referenceNode`. It doesn't work if `referenceNode`
+ * doesn't have a parent node.
+ *
+ * @param {HTMLElement} newNode
+ * @param {HTMLElement} referenceNode
+ */
+function insertAfter(newNode, referenceNode) {
+    referenceNode.parentNode.insertBefore(newNode, referenceNode.nextSibling);
+}
+
+/**
+ * This function creates a new `<section>` with the given `id` and `classes` if it doesn't already
+ * exist.
+ *
+ * More information about this in `switchDisplayedElement` documentation.
+ *
+ * @param {string} id
+ * @param {string} classes
+ */
+function getOrCreateSection(id, classes) {
+    let el = document.getElementById(id);
+
+    if (!el) {
+        el = document.createElement("section");
+        el.id = id;
+        el.className = classes;
+        insertAfter(el, document.getElementById(MAIN_ID));
+    }
+    return el;
+}
+
+/**
+ * Returns the `<section>` element which contains the displayed element.
+ *
+ * @return {HTMLElement}
+ */
+function getAlternativeDisplayElem() {
+    return getOrCreateSection(ALTERNATIVE_DISPLAY_ID, "content hidden");
+}
+
+/**
+ * Returns the `<section>` element which contains the not-displayed elements.
+ *
+ * @return {HTMLElement}
+ */
+function getNotDisplayedElem() {
+    return getOrCreateSection(NOT_DISPLAYED_ID, "hidden");
+}
+
+/**
+ * To nicely switch between displayed "extra" elements (such as search results or settings menu)
+ * and to alternate between the displayed and not displayed elements, we hold them in two different
+ * `<section>` elements. They work in pair: one holds the hidden elements while the other
+ * contains the displayed element (there can be only one at the same time!). So basically, we switch
+ * elements between the two `<section>` elements.
+ *
+ * @param {HTMLElement} elemToDisplay
+ */
+function switchDisplayedElement(elemToDisplay) {
+    const el = getAlternativeDisplayElem();
+
+    if (el.children.length > 0) {
+        getNotDisplayedElem().appendChild(el.firstElementChild);
+    }
+    if (elemToDisplay === null) {
+        addClass(el, "hidden");
+        showMain();
+        return;
+    }
+    el.appendChild(elemToDisplay);
+    hideMain();
+    removeClass(el, "hidden");
+}
+
+function browserSupportsHistoryApi() {
+    return window.history && typeof window.history.pushState === "function";
+}
+
+// eslint-disable-next-line no-unused-vars
+function loadCss(cssFileName) {
+    const link = document.createElement("link");
+    link.href = resourcePath(cssFileName, ".css");
+    link.type = "text/css";
+    link.rel = "stylesheet";
+    document.getElementsByTagName("head")[0].appendChild(link);
+}
+
+(function() {
+    function loadScript(url) {
+        const script = document.createElement("script");
+        script.src = url;
+        document.head.append(script);
+    }
+
+    getSettingsButton().onclick = event => {
+        addClass(getSettingsButton(), "rotate");
+        event.preventDefault();
+        // Sending request for the CSS and the JS files at the same time so it will
+        // hopefully be loaded when the JS will generate the settings content.
+        loadCss("settings");
+        loadScript(resourcePath("settings", ".js"));
+    };
+
+    window.searchState = {
+        loadingText: "Loading search results...",
+        input: document.getElementsByClassName("search-input")[0],
+        outputElement: () => {
+            let el = document.getElementById("search");
+            if (!el) {
+                el = document.createElement("section");
+                el.id = "search";
+                getNotDisplayedElem().appendChild(el);
+            }
+            return el;
+        },
+        title: document.title,
+        titleBeforeSearch: document.title,
+        timeout: null,
+        // On the search screen, so you remain on the last tab you opened.
+        //
+        // 0 for "In Names"
+        // 1 for "In Parameters"
+        // 2 for "In Return Types"
+        currentTab: 0,
+        // tab and back preserves the element that was focused.
+        focusedByTab: [null, null, null],
+        clearInputTimeout: () => {
+            if (searchState.timeout !== null) {
+                clearTimeout(searchState.timeout);
+                searchState.timeout = null;
+            }
+        },
+        isDisplayed: () => searchState.outputElement().parentElement.id === ALTERNATIVE_DISPLAY_ID,
+        // Sets the focus on the search bar at the top of the page
+        focus: () => {
+            searchState.input.focus();
+        },
+        // Removes the focus from the search bar.
+        defocus: () => {
+            searchState.input.blur();
+        },
+        showResults: search => {
+            if (search === null || typeof search === "undefined") {
+                search = searchState.outputElement();
+            }
+            switchDisplayedElement(search);
+            searchState.mouseMovedAfterSearch = false;
+            document.title = searchState.title;
+        },
+        hideResults: () => {
+            switchDisplayedElement(null);
+            document.title = searchState.titleBeforeSearch;
+            // We also remove the query parameter from the URL.
+            if (browserSupportsHistoryApi()) {
+                history.replaceState(null, window.currentCrate + " - Rust",
+                    getNakedUrl() + window.location.hash);
+            }
+        },
+        getQueryStringParams: () => {
+            const params = {};
+            window.location.search.substring(1).split("&").
+                map(s => {
+                    const pair = s.split("=");
+                    params[decodeURIComponent(pair[0])] =
+                        typeof pair[1] === "undefined" ? null : decodeURIComponent(pair[1]);
+                });
+            return params;
+        },
+        setup: () => {
+            const search_input = searchState.input;
+            if (!searchState.input) {
+                return;
+            }
+            let searchLoaded = false;
+            function loadSearch() {
+                if (!searchLoaded) {
+                    searchLoaded = true;
+                    loadScript(resourcePath("search", ".js"));
+                    loadScript(resourcePath("search-index", ".js"));
+                }
+            }
+
+            search_input.addEventListener("focus", () => {
+                search_input.origPlaceholder = search_input.placeholder;
+                search_input.placeholder = "Type your search here.";
+                loadSearch();
+            });
+
+            if (search_input.value !== "") {
+                loadSearch();
+            }
+
+            const params = searchState.getQueryStringParams();
+            if (params.search !== undefined) {
+                const search = searchState.outputElement();
+                search.innerHTML = "<h3 class=\"search-loading\">" +
+                    searchState.loadingText + "</h3>";
+                searchState.showResults(search);
+                loadSearch();
+            }
+        },
+    };
+
+    function getPageId() {
+        if (window.location.hash) {
+            const tmp = window.location.hash.replace(/^#/, "");
+            if (tmp.length > 0) {
+                return tmp;
+            }
+        }
+        return null;
+    }
+
+    const toggleAllDocsId = "toggle-all-docs";
+    let savedHash = "";
+
+    function handleHashes(ev) {
+        if (ev !== null && searchState.isDisplayed() && ev.newURL) {
+            // This block occurs when clicking on an element in the navbar while
+            // in a search.
+            switchDisplayedElement(null);
+            const hash = ev.newURL.slice(ev.newURL.indexOf("#") + 1);
+            if (browserSupportsHistoryApi()) {
+                // `window.location.search`` contains all the query parameters, not just `search`.
+                history.replaceState(null, "",
+                    getNakedUrl() + window.location.search + "#" + hash);
+            }
+            const elem = document.getElementById(hash);
+            if (elem) {
+                elem.scrollIntoView();
+            }
+        }
+        // This part is used in case an element is not visible.
+        if (savedHash !== window.location.hash) {
+            savedHash = window.location.hash;
+            if (savedHash.length === 0) {
+                return;
+            }
+            expandSection(savedHash.slice(1)); // we remove the '#'
+        }
+    }
+
+    function onHashChange(ev) {
+        // If we're in mobile mode, we should hide the sidebar in any case.
+        const sidebar = document.getElementsByClassName("sidebar")[0];
+        removeClass(sidebar, "shown");
+        handleHashes(ev);
+    }
+
+    function openParentDetails(elem) {
+        while (elem) {
+            if (elem.tagName === "DETAILS") {
+                elem.open = true;
+            }
+            elem = elem.parentNode;
+        }
+    }
+
+    function expandSection(id) {
+        openParentDetails(document.getElementById(id));
+    }
+
+    function handleEscape(ev) {
+        searchState.clearInputTimeout();
+        switchDisplayedElement(null);
+        if (browserSupportsHistoryApi()) {
+            history.replaceState(null, window.currentCrate + " - Rust",
+                getNakedUrl() + window.location.hash);
+        }
+        ev.preventDefault();
+        searchState.defocus();
+        window.hidePopoverMenus();
+    }
+
+    function handleShortcut(ev) {
+        // Don't interfere with browser shortcuts
+        const disableShortcuts = getSettingValue("disable-shortcuts") === "true";
+        if (ev.ctrlKey || ev.altKey || ev.metaKey || disableShortcuts) {
+            return;
+        }
+
+        if (document.activeElement.tagName === "INPUT" &&
+            document.activeElement.type !== "checkbox") {
+            switch (getVirtualKey(ev)) {
+            case "Escape":
+                handleEscape(ev);
+                break;
+            }
+        } else {
+            switch (getVirtualKey(ev)) {
+            case "Escape":
+                handleEscape(ev);
+                break;
+
+            case "s":
+            case "S":
+                ev.preventDefault();
+                searchState.focus();
+                break;
+
+            case "+":
+            case "-":
+                ev.preventDefault();
+                toggleAllDocs();
+                break;
+
+            case "?":
+                showHelp();
+                break;
+
+            default:
+                break;
+            }
+        }
+    }
+
+    document.addEventListener("keypress", handleShortcut);
+    document.addEventListener("keydown", handleShortcut);
+
+    function addSidebarItems() {
+        if (!window.SIDEBAR_ITEMS) {
+            return;
+        }
+        const sidebar = document.getElementsByClassName("sidebar-elems")[0];
+
+        /**
+         * Append to the sidebar a "block" of links - a heading along with a list (`<ul>`) of items.
+         *
+         * @param {string} shortty - A short type name, like "primitive", "mod", or "macro"
+         * @param {string} id - The HTML id of the corresponding section on the module page.
+         * @param {string} longty - A long, capitalized, plural name, like "Primitive Types",
+         *                          "Modules", or "Macros".
+         */
+        function block(shortty, id, longty) {
+            const filtered = window.SIDEBAR_ITEMS[shortty];
+            if (!filtered) {
+                return;
+            }
+
+            const div = document.createElement("div");
+            div.className = "block " + shortty;
+            const h3 = document.createElement("h3");
+            h3.innerHTML = `<a href="index.html#${id}">${longty}</a>`;
+            div.appendChild(h3);
+            const ul = document.createElement("ul");
+
+            for (const item of filtered) {
+                const name = item[0];
+                const desc = item[1]; // can be null
+
+                let klass = shortty;
+                let path;
+                if (shortty === "mod") {
+                    path = name + "/index.html";
+                } else {
+                    path = shortty + "." + name + ".html";
+                }
+                const current_page = document.location.href.split("/").pop();
+                if (path === current_page) {
+                    klass += " current";
+                }
+                const link = document.createElement("a");
+                link.href = path;
+                link.title = desc;
+                link.className = klass;
+                link.textContent = name;
+                const li = document.createElement("li");
+                li.appendChild(link);
+                ul.appendChild(li);
+            }
+            div.appendChild(ul);
+            sidebar.appendChild(div);
+        }
+
+        if (sidebar) {
+            block("primitive", "primitives", "Primitive Types");
+            block("mod", "modules", "Modules");
+            block("macro", "macros", "Macros");
+            block("struct", "structs", "Structs");
+            block("enum", "enums", "Enums");
+            block("union", "unions", "Unions");
+            block("constant", "constants", "Constants");
+            block("static", "static", "Statics");
+            block("trait", "traits", "Traits");
+            block("fn", "functions", "Functions");
+            block("type", "types", "Type Definitions");
+            block("foreigntype", "foreign-types", "Foreign Types");
+            block("keyword", "keywords", "Keywords");
+            block("traitalias", "trait-aliases", "Trait Aliases");
+        }
+    }
+
+    window.register_implementors = imp => {
+        const implementors = document.getElementById("implementors-list");
+        const synthetic_implementors = document.getElementById("synthetic-implementors-list");
+        const inlined_types = new Set();
+
+        if (synthetic_implementors) {
+            // This `inlined_types` variable is used to avoid having the same implementation
+            // showing up twice. For example "String" in the "Sync" doc page.
+            //
+            // By the way, this is only used by and useful for traits implemented automatically
+            // (like "Send" and "Sync").
+            onEachLazy(synthetic_implementors.getElementsByClassName("impl"), el => {
+                const aliases = el.getAttribute("data-aliases");
+                if (!aliases) {
+                    return;
+                }
+                aliases.split(",").forEach(alias => {
+                    inlined_types.add(alias);
+                });
+            });
+        }
+
+        let currentNbImpls = implementors.getElementsByClassName("impl").length;
+        const traitName = document.querySelector("h1.fqn > .in-band > .trait").textContent;
+        const baseIdName = "impl-" + traitName + "-";
+        const libs = Object.getOwnPropertyNames(imp);
+        // We don't want to include impls from this JS file, when the HTML already has them.
+        // The current crate should always be ignored. Other crates that should also be
+        // ignored are included in the attribute `data-ignore-extern-crates`.
+        const ignoreExternCrates = document
+            .querySelector("script[data-ignore-extern-crates]")
+            .getAttribute("data-ignore-extern-crates");
+        for (const lib of libs) {
+            if (lib === window.currentCrate || ignoreExternCrates.indexOf(lib) !== -1) {
+                continue;
+            }
+            const structs = imp[lib];
+
+            struct_loop:
+            for (const struct of structs) {
+                const list = struct.synthetic ? synthetic_implementors : implementors;
+
+                if (struct.synthetic) {
+                    for (const struct_type of struct.types) {
+                        if (inlined_types.has(struct_type)) {
+                            continue struct_loop;
+                        }
+                        inlined_types.add(struct_type);
+                    }
+                }
+
+                const code = document.createElement("h3");
+                code.innerHTML = struct.text;
+                addClass(code, "code-header");
+                addClass(code, "in-band");
+
+                onEachLazy(code.getElementsByTagName("a"), elem => {
+                    const href = elem.getAttribute("href");
+
+                    if (href && href.indexOf("http") !== 0) {
+                        elem.setAttribute("href", window.rootPath + href);
+                    }
+                });
+
+                const currentId = baseIdName + currentNbImpls;
+                const anchor = document.createElement("a");
+                anchor.href = "#" + currentId;
+                addClass(anchor, "anchor");
+
+                const display = document.createElement("div");
+                display.id = currentId;
+                addClass(display, "impl");
+                display.appendChild(anchor);
+                display.appendChild(code);
+                list.appendChild(display);
+                currentNbImpls += 1;
+            }
+        }
+    };
+    if (window.pending_implementors) {
+        window.register_implementors(window.pending_implementors);
+    }
+
+    function addSidebarCrates() {
+        if (!window.ALL_CRATES) {
+            return;
+        }
+        const sidebarElems = document.getElementsByClassName("sidebar-elems")[0];
+        if (!sidebarElems) {
+            return;
+        }
+        // Draw a convenient sidebar of known crates if we have a listing
+        const div = document.createElement("div");
+        div.className = "block crate";
+        div.innerHTML = "<h3>Crates</h3>";
+        const ul = document.createElement("ul");
+        div.appendChild(ul);
+
+        for (const crate of window.ALL_CRATES) {
+            let klass = "crate";
+            if (window.rootPath !== "./" && crate === window.currentCrate) {
+                klass += " current";
+            }
+            const link = document.createElement("a");
+            link.href = window.rootPath + crate + "/index.html";
+            link.className = klass;
+            link.textContent = crate;
+
+            const li = document.createElement("li");
+            li.appendChild(link);
+            ul.appendChild(li);
+        }
+        sidebarElems.appendChild(div);
+    }
+
+
+    function labelForToggleButton(sectionIsCollapsed) {
+        if (sectionIsCollapsed) {
+            // button will expand the section
+            return "+";
+        }
+        // button will collapse the section
+        // note that this text is also set in the HTML template in ../render/mod.rs
+        return "\u2212"; // "\u2212" is "−" minus sign
+    }
+
+    function toggleAllDocs() {
+        const innerToggle = document.getElementById(toggleAllDocsId);
+        if (!innerToggle) {
+            return;
+        }
+        let sectionIsCollapsed = false;
+        if (hasClass(innerToggle, "will-expand")) {
+            removeClass(innerToggle, "will-expand");
+            onEachLazy(document.getElementsByClassName("rustdoc-toggle"), e => {
+                if (!hasClass(e, "type-contents-toggle")) {
+                    e.open = true;
+                }
+            });
+            innerToggle.title = "collapse all docs";
+        } else {
+            addClass(innerToggle, "will-expand");
+            onEachLazy(document.getElementsByClassName("rustdoc-toggle"), e => {
+                if (e.parentNode.id !== "implementations-list" ||
+                    (!hasClass(e, "implementors-toggle") &&
+                     !hasClass(e, "type-contents-toggle"))
+                ) {
+                    e.open = false;
+                }
+            });
+            sectionIsCollapsed = true;
+            innerToggle.title = "expand all docs";
+        }
+        innerToggle.children[0].innerText = labelForToggleButton(sectionIsCollapsed);
+    }
+
+    (function() {
+        const toggles = document.getElementById(toggleAllDocsId);
+        if (toggles) {
+            toggles.onclick = toggleAllDocs;
+        }
+
+        const hideMethodDocs = getSettingValue("auto-hide-method-docs") === "true";
+        const hideImplementations = getSettingValue("auto-hide-trait-implementations") === "true";
+        const hideLargeItemContents = getSettingValue("auto-hide-large-items") !== "false";
+
+        function setImplementorsTogglesOpen(id, open) {
+            const list = document.getElementById(id);
+            if (list !== null) {
+                onEachLazy(list.getElementsByClassName("implementors-toggle"), e => {
+                    e.open = open;
+                });
+            }
+        }
+
+        if (hideImplementations) {
+            setImplementorsTogglesOpen("trait-implementations-list", false);
+            setImplementorsTogglesOpen("blanket-implementations-list", false);
+        }
+
+        onEachLazy(document.getElementsByClassName("rustdoc-toggle"), e => {
+            if (!hideLargeItemContents && hasClass(e, "type-contents-toggle")) {
+                e.open = true;
+            }
+            if (hideMethodDocs && hasClass(e, "method-toggle")) {
+                e.open = false;
+            }
+
+        });
+
+        const pageId = getPageId();
+        if (pageId !== null) {
+            expandSection(pageId);
+        }
+    }());
+
+    (function() {
+        // To avoid checking on "rustdoc-line-numbers" value on every loop...
+        let lineNumbersFunc = () => {};
+        if (getSettingValue("line-numbers") === "true") {
+            lineNumbersFunc = x => {
+                const count = x.textContent.split("\n").length;
+                const elems = [];
+                for (let i = 0; i < count; ++i) {
+                    elems.push(i + 1);
+                }
+                const node = document.createElement("pre");
+                addClass(node, "line-number");
+                node.innerHTML = elems.join("\n");
+                x.parentNode.insertBefore(node, x);
+            };
+        }
+        onEachLazy(document.getElementsByClassName("rust-example-rendered"), e => {
+            if (hasClass(e, "compile_fail")) {
+                e.addEventListener("mouseover", function() {
+                    this.parentElement.previousElementSibling.childNodes[0].style.color = "#f00";
+                });
+                e.addEventListener("mouseout", function() {
+                    this.parentElement.previousElementSibling.childNodes[0].style.color = "";
+                });
+            } else if (hasClass(e, "ignore")) {
+                e.addEventListener("mouseover", function() {
+                    this.parentElement.previousElementSibling.childNodes[0].style.color = "#ff9200";
+                });
+                e.addEventListener("mouseout", function() {
+                    this.parentElement.previousElementSibling.childNodes[0].style.color = "";
+                });
+            }
+            lineNumbersFunc(e);
+        });
+    }());
+
+    function hideSidebar() {
+        const sidebar = document.getElementsByClassName("sidebar")[0];
+        removeClass(sidebar, "shown");
+    }
+
+    function handleClick(id, f) {
+        const elem = document.getElementById(id);
+        if (elem) {
+            elem.addEventListener("click", f);
+        }
+    }
+    handleClick(MAIN_ID, () => {
+        hideSidebar();
+    });
+
+    onEachLazy(document.getElementsByTagName("a"), el => {
+        // For clicks on internal links (<A> tags with a hash property), we expand the section we're
+        // jumping to *before* jumping there. We can't do this in onHashChange, because it changes
+        // the height of the document so we wind up scrolled to the wrong place.
+        if (el.hash) {
+            el.addEventListener("click", () => {
+                expandSection(el.hash.slice(1));
+                hideSidebar();
+            });
+        }
+    });
+
+    onEachLazy(document.querySelectorAll(".rustdoc-toggle > summary:not(.hideme)"), el => {
+        el.addEventListener("click", e => {
+            if (e.target.tagName !== "SUMMARY" && e.target.tagName !== "A") {
+                e.preventDefault();
+            }
+        });
+    });
+
+    onEachLazy(document.getElementsByClassName("notable-traits"), e => {
+        e.onclick = function() {
+            this.getElementsByClassName("notable-traits-tooltiptext")[0]
+                .classList.toggle("force-tooltip");
+        };
+    });
+
+    const sidebar_menu_toggle = document.getElementsByClassName("sidebar-menu-toggle")[0];
+    if (sidebar_menu_toggle) {
+        sidebar_menu_toggle.addEventListener("click", () => {
+            const sidebar = document.getElementsByClassName("sidebar")[0];
+            if (!hasClass(sidebar, "shown")) {
+                addClass(sidebar, "shown");
+            } else {
+                removeClass(sidebar, "shown");
+            }
+        });
+    }
+
+    function helpBlurHandler(event) {
+        blurHandler(event, getHelpButton(), window.hidePopoverMenus);
+    }
+
+    function buildHelpMenu() {
+        const book_info = document.createElement("span");
+        book_info.className = "top";
+        book_info.innerHTML = "You can find more information in \
+            <a href=\"https://doc.rust-lang.org/rustdoc/\">the rustdoc book</a>.";
+
+        const shortcuts = [
+            ["?", "Show this help dialog"],
+            ["S", "Focus the search field"],
+            ["↑", "Move up in search results"],
+            ["↓", "Move down in search results"],
+            ["← / →", "Switch result tab (when results focused)"],
+            ["&#9166;", "Go to active search result"],
+            ["+", "Expand all sections"],
+            ["-", "Collapse all sections"],
+        ].map(x => "<dt>" +
+            x[0].split(" ")
+                .map((y, index) => ((index & 1) === 0 ? "<kbd>" + y + "</kbd>" : " " + y + " "))
+                .join("") + "</dt><dd>" + x[1] + "</dd>").join("");
+        const div_shortcuts = document.createElement("div");
+        addClass(div_shortcuts, "shortcuts");
+        div_shortcuts.innerHTML = "<h2>Keyboard Shortcuts</h2><dl>" + shortcuts + "</dl></div>";
+
+        const infos = [
+            "Prefix searches with a type followed by a colon (e.g., <code>fn:</code>) to \
+             restrict the search to a given item kind.",
+            "Accepted kinds are: <code>fn</code>, <code>mod</code>, <code>struct</code>, \
+             <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, \
+             and <code>const</code>.",
+            "Search functions by type signature (e.g., <code>vec -&gt; usize</code> or \
+             <code>-&gt; vec</code>)",
+            "Search multiple things at once by splitting your query with comma (e.g., \
+             <code>str,u8</code> or <code>String,struct:Vec,test</code>)",
+            "You can look for items with an exact name by putting double quotes around \
+             your request: <code>\"string\"</code>",
+            "Look for items inside another one by searching for a path: <code>vec::Vec</code>",
+        ].map(x => "<p>" + x + "</p>").join("");
+        const div_infos = document.createElement("div");
+        addClass(div_infos, "infos");
+        div_infos.innerHTML = "<h2>Search Tricks</h2>" + infos;
+
+        const rustdoc_version = document.createElement("span");
+        rustdoc_version.className = "bottom";
+        const rustdoc_version_code = document.createElement("code");
+        rustdoc_version_code.innerText = "rustdoc " + getVar("rustdoc-version");
+        rustdoc_version.appendChild(rustdoc_version_code);
+
+        const container = document.createElement("div");
+        container.className = "popover";
+        container.style.display = "none";
+
+        const side_by_side = document.createElement("div");
+        side_by_side.className = "side-by-side";
+        side_by_side.appendChild(div_shortcuts);
+        side_by_side.appendChild(div_infos);
+
+        container.appendChild(book_info);
+        container.appendChild(side_by_side);
+        container.appendChild(rustdoc_version);
+
+        const help_button = getHelpButton();
+        help_button.appendChild(container);
+
+        container.onblur = helpBlurHandler;
+        container.onclick = event => {
+            event.preventDefault();
+        };
+        help_button.onblur = helpBlurHandler;
+        help_button.children[0].onblur = helpBlurHandler;
+
+        return container;
+    }
+
+    /**
+     * Hide all the popover menus.
+     */
+    window.hidePopoverMenus = function() {
+        onEachLazy(document.querySelectorAll(".search-container .popover"), elem => {
+            elem.style.display = "none";
+        });
+    };
+
+    /**
+     * Returns the help menu element (not the button).
+     *
+     * @param {boolean} buildNeeded - If this argument is `false`, the help menu element won't be
+     *                                built if it doesn't exist.
+     *
+     * @return {HTMLElement}
+     */
+    function getHelpMenu(buildNeeded) {
+        let menu = getHelpButton().querySelector(".popover");
+        if (!menu && buildNeeded) {
+            menu = buildHelpMenu();
+        }
+        return menu;
+    }
+
+    /**
+     * Show the help popup menu.
+     */
+    function showHelp() {
+        const menu = getHelpMenu(true);
+        if (menu.style.display === "none") {
+            window.hidePopoverMenus();
+            menu.style.display = "";
+        }
+    }
+
+    document.querySelector(`#${HELP_BUTTON_ID} > button`).addEventListener("click", event => {
+        const target = event.target;
+        if (target.tagName !== "BUTTON" || target.parentElement.id !== HELP_BUTTON_ID) {
+            return;
+        }
+        const menu = getHelpMenu(true);
+        const shouldShowHelp = menu.style.display === "none";
+        if (shouldShowHelp) {
+            showHelp();
+        } else {
+            window.hidePopoverMenus();
+        }
+    });
+
+    setMobileTopbar();
+    addSidebarItems();
+    addSidebarCrates();
+    onHashChange(null);
+    window.addEventListener("hashchange", onHashChange);
+    searchState.setup();
+}());
+
+(function() {
+    let reset_button_timeout = null;
+
+    window.copy_path = but => {
+        const parent = but.parentElement;
+        const path = [];
+
+        onEach(parent.childNodes, child => {
+            if (child.tagName === "A") {
+                path.push(child.textContent);
+            }
+        });
+
+        const el = document.createElement("textarea");
+        el.value = path.join("::");
+        el.setAttribute("readonly", "");
+        // To not make it appear on the screen.
+        el.style.position = "absolute";
+        el.style.left = "-9999px";
+
+        document.body.appendChild(el);
+        el.select();
+        document.execCommand("copy");
+        document.body.removeChild(el);
+
+        // There is always one children, but multiple childNodes.
+        but.children[0].style.display = "none";
+
+        let tmp;
+        if (but.childNodes.length < 2) {
+            tmp = document.createTextNode("✓");
+            but.appendChild(tmp);
+        } else {
+            onEachLazy(but.childNodes, e => {
+                if (e.nodeType === Node.TEXT_NODE) {
+                    tmp = e;
+                    return true;
+                }
+            });
+            tmp.textContent = "✓";
+        }
+
+        if (reset_button_timeout !== null) {
+            window.clearTimeout(reset_button_timeout);
+        }
+
+        function reset_button() {
+            tmp.textContent = "";
+            reset_button_timeout = null;
+            but.children[0].style.display = "";
+        }
+
+        reset_button_timeout = window.setTimeout(reset_button, 1000);
+    };
+}());
diff --git a/src/librustdoc/html/static/js/scrape-examples.js b/src/librustdoc/html/static/js/scrape-examples.js
new file mode 100644
index 000000000..fd7a14497
--- /dev/null
+++ b/src/librustdoc/html/static/js/scrape-examples.js
@@ -0,0 +1,106 @@
+/* global addClass, hasClass, removeClass, onEachLazy */
+
+"use strict";
+
+(function() {
+    // Number of lines shown when code viewer is not expanded
+    const MAX_LINES = 10;
+
+    // Scroll code block to the given code location
+    function scrollToLoc(elt, loc) {
+        const lines = elt.querySelector(".line-numbers");
+        let scrollOffset;
+
+        // If the block is greater than the size of the viewer,
+        // then scroll to the top of the block. Otherwise scroll
+        // to the middle of the block.
+        if (loc[1] - loc[0] > MAX_LINES) {
+            const line = Math.max(0, loc[0] - 1);
+            scrollOffset = lines.children[line].offsetTop;
+        } else {
+            const wrapper = elt.querySelector(".code-wrapper");
+            const halfHeight = wrapper.offsetHeight / 2;
+            const offsetMid = (lines.children[loc[0]].offsetTop
+                             + lines.children[loc[1]].offsetTop) / 2;
+            scrollOffset = offsetMid - halfHeight;
+        }
+
+        lines.scrollTo(0, scrollOffset);
+        elt.querySelector(".rust").scrollTo(0, scrollOffset);
+    }
+
+    function updateScrapedExample(example) {
+        const locs = JSON.parse(example.attributes.getNamedItem("data-locs").textContent);
+        let locIndex = 0;
+        const highlights = Array.prototype.slice.call(example.querySelectorAll(".highlight"));
+        const link = example.querySelector(".scraped-example-title a");
+
+        if (locs.length > 1) {
+            // Toggle through list of examples in a given file
+            const onChangeLoc = changeIndex => {
+                removeClass(highlights[locIndex], "focus");
+                changeIndex();
+                scrollToLoc(example, locs[locIndex][0]);
+                addClass(highlights[locIndex], "focus");
+
+                const url = locs[locIndex][1];
+                const title = locs[locIndex][2];
+
+                link.href = url;
+                link.innerHTML = title;
+            };
+
+            example.querySelector(".prev")
+                .addEventListener("click", () => {
+                    onChangeLoc(() => {
+                        locIndex = (locIndex - 1 + locs.length) % locs.length;
+                    });
+                });
+
+            example.querySelector("next")
+                .addEventListener("click", () => {
+                    onChangeLoc(() => {
+                        locIndex = (locIndex + 1) % locs.length;
+                    });
+                });
+        }
+
+        const expandButton = example.querySelector(".expand");
+        if (expandButton) {
+            expandButton.addEventListener("click", () => {
+                if (hasClass(example, "expanded")) {
+                    removeClass(example, "expanded");
+                    scrollToLoc(example, locs[0][0]);
+                } else {
+                    addClass(example, "expanded");
+                }
+            });
+        }
+
+        // Start with the first example in view
+        scrollToLoc(example, locs[0][0]);
+    }
+
+    const firstExamples = document.querySelectorAll(".scraped-example-list > .scraped-example");
+    onEachLazy(firstExamples, updateScrapedExample);
+    onEachLazy(document.querySelectorAll(".more-examples-toggle"), toggle => {
+        // Allow users to click the left border of the <details> section to close it,
+        // since the section can be large and finding the [+] button is annoying.
+        onEachLazy(toggle.querySelectorAll(".toggle-line, .hide-more"), button => {
+            button.addEventListener("click", () => {
+                toggle.open = false;
+            });
+        });
+
+        const moreExamples = toggle.querySelectorAll(".scraped-example");
+        toggle.querySelector("summary").addEventListener("click", () => {
+            // Wrapping in setTimeout ensures the update happens after the elements are actually
+            // visible. This is necessary since updateScrapedExample calls scrollToLoc which
+            // depends on offsetHeight, a property that requires an element to be visible to
+            // compute correctly.
+            setTimeout(() => {
+                onEachLazy(moreExamples, updateScrapedExample);
+            });
+        }, {once: true});
+    });
+})();
diff --git a/src/librustdoc/html/static/js/search.js b/src/librustdoc/html/static/js/search.js
new file mode 100644
index 000000000..75c7bd45a
--- /dev/null
+++ b/src/librustdoc/html/static/js/search.js
@@ -0,0 +1,2297 @@
+/* global addClass, getNakedUrl, getSettingValue */
+/* global onEachLazy, removeClass, searchState, browserSupportsHistoryApi, exports */
+
+"use strict";
+
+(function() {
+// This mapping table should match the discriminants of
+// `rustdoc::formats::item_type::ItemType` type in Rust.
+const itemTypes = [
+    "mod",
+    "externcrate",
+    "import",
+    "struct",
+    "enum",
+    "fn",
+    "type",
+    "static",
+    "trait",
+    "impl",
+    "tymethod",
+    "method",
+    "structfield",
+    "variant",
+    "macro",
+    "primitive",
+    "associatedtype",
+    "constant",
+    "associatedconstant",
+    "union",
+    "foreigntype",
+    "keyword",
+    "existential",
+    "attr",
+    "derive",
+    "traitalias",
+];
+
+// used for special search precedence
+const TY_PRIMITIVE = itemTypes.indexOf("primitive");
+const TY_KEYWORD = itemTypes.indexOf("keyword");
+const ROOT_PATH = typeof window !== "undefined" ? window.rootPath : "../";
+
+function hasOwnPropertyRustdoc(obj, property) {
+    return Object.prototype.hasOwnProperty.call(obj, property);
+}
+
+// In the search display, allows to switch between tabs.
+function printTab(nb) {
+    let iter = 0;
+    let foundCurrentTab = false;
+    let foundCurrentResultSet = false;
+    onEachLazy(document.getElementById("titles").childNodes, elem => {
+        if (nb === iter) {
+            addClass(elem, "selected");
+            foundCurrentTab = true;
+        } else {
+            removeClass(elem, "selected");
+        }
+        iter += 1;
+    });
+    iter = 0;
+    onEachLazy(document.getElementById("results").childNodes, elem => {
+        if (nb === iter) {
+            addClass(elem, "active");
+            foundCurrentResultSet = true;
+        } else {
+            removeClass(elem, "active");
+        }
+        iter += 1;
+    });
+    if (foundCurrentTab && foundCurrentResultSet) {
+        searchState.currentTab = nb;
+    } else if (nb !== 0) {
+        printTab(0);
+    }
+}
+
+/**
+ * A function to compute the Levenshtein distance between two strings
+ * Licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported
+ * Full License can be found at http://creativecommons.org/licenses/by-sa/3.0/legalcode
+ * This code is an unmodified version of the code written by Marco de Wit
+ * and was found at https://stackoverflow.com/a/18514751/745719
+ */
+const levenshtein_row2 = [];
+function levenshtein(s1, s2) {
+    if (s1 === s2) {
+        return 0;
+    }
+    const s1_len = s1.length, s2_len = s2.length;
+    if (s1_len && s2_len) {
+        let i1 = 0, i2 = 0, a, b, c, c2;
+        const row = levenshtein_row2;
+        while (i1 < s1_len) {
+            row[i1] = ++i1;
+        }
+        while (i2 < s2_len) {
+            c2 = s2.charCodeAt(i2);
+            a = i2;
+            ++i2;
+            b = i2;
+            for (i1 = 0; i1 < s1_len; ++i1) {
+                c = a + (s1.charCodeAt(i1) !== c2 ? 1 : 0);
+                a = row[i1];
+                b = b < a ? (b < c ? b + 1 : c) : (a < c ? a + 1 : c);
+                row[i1] = b;
+            }
+        }
+        return b;
+    }
+    return s1_len + s2_len;
+}
+
+function initSearch(rawSearchIndex) {
+    const MAX_LEV_DISTANCE = 3;
+    const MAX_RESULTS = 200;
+    const NO_TYPE_FILTER = -1;
+    /**
+     *  @type {Array<Row>}
+     */
+    let searchIndex;
+    let currentResults;
+    const ALIASES = Object.create(null);
+
+    function isWhitespace(c) {
+        return " \t\n\r".indexOf(c) !== -1;
+    }
+
+    function isSpecialStartCharacter(c) {
+        return "<\"".indexOf(c) !== -1;
+    }
+
+    function isEndCharacter(c) {
+        return ",>-".indexOf(c) !== -1;
+    }
+
+    function isStopCharacter(c) {
+        return isWhitespace(c) || isEndCharacter(c);
+    }
+
+    function isErrorCharacter(c) {
+        return "()".indexOf(c) !== -1;
+    }
+
+    function itemTypeFromName(typename) {
+        for (let i = 0, len = itemTypes.length; i < len; ++i) {
+            if (itemTypes[i] === typename) {
+                return i;
+            }
+        }
+
+        throw new Error("Unknown type filter `" + typename + "`");
+    }
+
+    /**
+     * If we encounter a `"`, then we try to extract the string from it until we find another `"`.
+     *
+     * This function will throw an error in the following cases:
+     * * There is already another string element.
+     * * We are parsing a generic argument.
+     * * There is more than one element.
+     * * There is no closing `"`.
+     *
+     * @param {ParsedQuery} query
+     * @param {ParserState} parserState
+     * @param {boolean} isInGenerics
+     */
+    function getStringElem(query, parserState, isInGenerics) {
+        if (isInGenerics) {
+            throw new Error("`\"` cannot be used in generics");
+        } else if (query.literalSearch) {
+            throw new Error("Cannot have more than one literal search element");
+        } else if (parserState.totalElems - parserState.genericsElems > 0) {
+            throw new Error("Cannot use literal search when there is more than one element");
+        }
+        parserState.pos += 1;
+        const start = parserState.pos;
+        const end = getIdentEndPosition(parserState);
+        if (parserState.pos >= parserState.length) {
+            throw new Error("Unclosed `\"`");
+        } else if (parserState.userQuery[end] !== "\"") {
+            throw new Error(`Unexpected \`${parserState.userQuery[end]}\` in a string element`);
+        } else if (start === end) {
+            throw new Error("Cannot have empty string element");
+        }
+        // To skip the quote at the end.
+        parserState.pos += 1;
+        query.literalSearch = true;
+    }
+
+    /**
+     * Returns `true` if the current parser position is starting with "::".
+     *
+     * @param {ParserState} parserState
+     *
+     * @return {boolean}
+     */
+    function isPathStart(parserState) {
+        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) === "::";
+    }
+
+    /**
+     * Returns `true` if the current parser position is starting with "->".
+     *
+     * @param {ParserState} parserState
+     *
+     * @return {boolean}
+     */
+    function isReturnArrow(parserState) {
+        return parserState.userQuery.slice(parserState.pos, parserState.pos + 2) === "->";
+    }
+
+    /**
+     * Returns `true` if the given `c` character is valid for an ident.
+     *
+     * @param {string} c
+     *
+     * @return {boolean}
+     */
+    function isIdentCharacter(c) {
+        return (
+            c === "_" ||
+            (c >= "0" && c <= "9") ||
+            (c >= "a" && c <= "z") ||
+            (c >= "A" && c <= "Z"));
+    }
+
+    /**
+     * Returns `true` if the given `c` character is a separator.
+     *
+     * @param {string} c
+     *
+     * @return {boolean}
+     */
+    function isSeparatorCharacter(c) {
+        return c === "," || isWhitespaceCharacter(c);
+    }
+
+    /**
+     * Returns `true` if the given `c` character is a whitespace.
+     *
+     * @param {string} c
+     *
+     * @return {boolean}
+     */
+    function isWhitespaceCharacter(c) {
+        return c === " " || c === "\t";
+    }
+
+    /**
+     * @param {ParsedQuery} query
+     * @param {ParserState} parserState
+     * @param {string} name                  - Name of the query element.
+     * @param {Array<QueryElement>} generics - List of generics of this query element.
+     *
+     * @return {QueryElement}                - The newly created `QueryElement`.
+     */
+    function createQueryElement(query, parserState, name, generics, isInGenerics) {
+        if (name === "*" || (name.length === 0 && generics.length === 0)) {
+            return;
+        }
+        if (query.literalSearch && parserState.totalElems - parserState.genericsElems > 0) {
+            throw new Error("You cannot have more than one element if you use quotes");
+        }
+        const pathSegments = name.split("::");
+        if (pathSegments.length > 1) {
+            for (let i = 0, len = pathSegments.length; i < len; ++i) {
+                const pathSegment = pathSegments[i];
+
+                if (pathSegment.length === 0) {
+                    if (i === 0) {
+                        throw new Error("Paths cannot start with `::`");
+                    } else if (i + 1 === len) {
+                        throw new Error("Paths cannot end with `::`");
+                    }
+                    throw new Error("Unexpected `::::`");
+                }
+            }
+        }
+        // In case we only have something like `<p>`, there is no name.
+        if (pathSegments.length === 0 || (pathSegments.length === 1 && pathSegments[0] === "")) {
+            throw new Error("Found generics without a path");
+        }
+        parserState.totalElems += 1;
+        if (isInGenerics) {
+            parserState.genericsElems += 1;
+        }
+        return {
+            name: name,
+            fullPath: pathSegments,
+            pathWithoutLast: pathSegments.slice(0, pathSegments.length - 1),
+            pathLast: pathSegments[pathSegments.length - 1],
+            generics: generics,
+        };
+    }
+
+    /**
+     * This function goes through all characters until it reaches an invalid ident character or the
+     * end of the query. It returns the position of the last character of the ident.
+     *
+     * @param {ParserState} parserState
+     *
+     * @return {integer}
+     */
+    function getIdentEndPosition(parserState) {
+        let end = parserState.pos;
+        let foundExclamation = false;
+        while (parserState.pos < parserState.length) {
+            const c = parserState.userQuery[parserState.pos];
+            if (!isIdentCharacter(c)) {
+                if (c === "!") {
+                    if (foundExclamation) {
+                        throw new Error("Cannot have more than one `!` in an ident");
+                    } else if (parserState.pos + 1 < parserState.length &&
+                        isIdentCharacter(parserState.userQuery[parserState.pos + 1])
+                    ) {
+                        throw new Error("`!` can only be at the end of an ident");
+                    }
+                    foundExclamation = true;
+                } else if (isErrorCharacter(c)) {
+                    throw new Error(`Unexpected \`${c}\``);
+                } else if (
+                    isStopCharacter(c) ||
+                    isSpecialStartCharacter(c) ||
+                    isSeparatorCharacter(c)
+                ) {
+                    break;
+                } else if (c === ":") { // If we allow paths ("str::string" for example).
+                    if (!isPathStart(parserState)) {
+                        break;
+                    }
+                    // Skip current ":".
+                    parserState.pos += 1;
+                    foundExclamation = false;
+                } else {
+                    throw new Error(`Unexpected \`${c}\``);
+                }
+            }
+            parserState.pos += 1;
+            end = parserState.pos;
+        }
+        return end;
+    }
+
+    /**
+     * @param {ParsedQuery} query
+     * @param {ParserState} parserState
+     * @param {Array<QueryElement>} elems - This is where the new {QueryElement} will be added.
+     * @param {boolean} isInGenerics
+     */
+    function getNextElem(query, parserState, elems, isInGenerics) {
+        const generics = [];
+
+        let start = parserState.pos;
+        let end;
+        // We handle the strings on their own mostly to make code easier to follow.
+        if (parserState.userQuery[parserState.pos] === "\"") {
+            start += 1;
+            getStringElem(query, parserState, isInGenerics);
+            end = parserState.pos - 1;
+        } else {
+            end = getIdentEndPosition(parserState);
+        }
+        if (parserState.pos < parserState.length &&
+            parserState.userQuery[parserState.pos] === "<"
+        ) {
+            if (isInGenerics) {
+                throw new Error("Unexpected `<` after `<`");
+            } else if (start >= end) {
+                throw new Error("Found generics without a path");
+            }
+            parserState.pos += 1;
+            getItemsBefore(query, parserState, generics, ">");
+        }
+        if (start >= end && generics.length === 0) {
+            return;
+        }
+        elems.push(
+            createQueryElement(
+                query,
+                parserState,
+                parserState.userQuery.slice(start, end),
+                generics,
+                isInGenerics
+            )
+        );
+    }
+
+    /**
+     * This function parses the next query element until it finds `endChar`, calling `getNextElem`
+     * to collect each element.
+     *
+     * If there is no `endChar`, this function will implicitly stop at the end without raising an
+     * error.
+     *
+     * @param {ParsedQuery} query
+     * @param {ParserState} parserState
+     * @param {Array<QueryElement>} elems - This is where the new {QueryElement} will be added.
+     * @param {string} endChar            - This function will stop when it'll encounter this
+     *                                      character.
+     */
+    function getItemsBefore(query, parserState, elems, endChar) {
+        let foundStopChar = true;
+
+        while (parserState.pos < parserState.length) {
+            const c = parserState.userQuery[parserState.pos];
+            if (c === endChar) {
+                break;
+            } else if (isSeparatorCharacter(c)) {
+                parserState.pos += 1;
+                foundStopChar = true;
+                continue;
+            } else if (c === ":" && isPathStart(parserState)) {
+                throw new Error("Unexpected `::`: paths cannot start with `::`");
+            } else if (c === ":" || isEndCharacter(c)) {
+                let extra = "";
+                if (endChar === ">") {
+                    extra = "`<`";
+                } else if (endChar === "") {
+                    extra = "`->`";
+                }
+                throw new Error("Unexpected `" + c + "` after " + extra);
+            }
+            if (!foundStopChar) {
+                if (endChar !== "") {
+                    throw new Error(`Expected \`,\`, \` \` or \`${endChar}\`, found \`${c}\``);
+                }
+                throw new Error(`Expected \`,\` or \` \`, found \`${c}\``);
+            }
+            const posBefore = parserState.pos;
+            getNextElem(query, parserState, elems, endChar === ">");
+            // This case can be encountered if `getNextElem` encounted a "stop character" right from
+            // the start. For example if you have `,,` or `<>`. In this case, we simply move up the
+            // current position to continue the parsing.
+            if (posBefore === parserState.pos) {
+                parserState.pos += 1;
+            }
+            foundStopChar = false;
+        }
+        // We are either at the end of the string or on the `endChar`` character, let's move forward
+        // in any case.
+        parserState.pos += 1;
+    }
+
+    /**
+     * Checks that the type filter doesn't have unwanted characters like `<>` (which are ignored
+     * if empty).
+     *
+     * @param {ParserState} parserState
+     */
+    function checkExtraTypeFilterCharacters(parserState) {
+        const query = parserState.userQuery;
+
+        for (let pos = 0; pos < parserState.pos; ++pos) {
+            if (!isIdentCharacter(query[pos]) && !isWhitespaceCharacter(query[pos])) {
+                throw new Error(`Unexpected \`${query[pos]}\` in type filter`);
+            }
+        }
+    }
+
+    /**
+     * Parses the provided `query` input to fill `parserState`. If it encounters an error while
+     * parsing `query`, it'll throw an error.
+     *
+     * @param {ParsedQuery} query
+     * @param {ParserState} parserState
+     */
+    function parseInput(query, parserState) {
+        let c, before;
+        let foundStopChar = true;
+
+        while (parserState.pos < parserState.length) {
+            c = parserState.userQuery[parserState.pos];
+            if (isStopCharacter(c)) {
+                foundStopChar = true;
+                if (isSeparatorCharacter(c)) {
+                    parserState.pos += 1;
+                    continue;
+                } else if (c === "-" || c === ">") {
+                    if (isReturnArrow(parserState)) {
+                        break;
+                    }
+                    throw new Error(`Unexpected \`${c}\` (did you mean \`->\`?)`);
+                }
+                throw new Error(`Unexpected \`${c}\``);
+            } else if (c === ":" && !isPathStart(parserState)) {
+                if (parserState.typeFilter !== null) {
+                    throw new Error("Unexpected `:`");
+                }
+                if (query.elems.length === 0) {
+                    throw new Error("Expected type filter before `:`");
+                } else if (query.elems.length !== 1 || parserState.totalElems !== 1) {
+                    throw new Error("Unexpected `:`");
+                } else if (query.literalSearch) {
+                    throw new Error("You cannot use quotes on type filter");
+                }
+                checkExtraTypeFilterCharacters(parserState);
+                // The type filter doesn't count as an element since it's a modifier.
+                parserState.typeFilter = query.elems.pop().name;
+                parserState.pos += 1;
+                parserState.totalElems = 0;
+                query.literalSearch = false;
+                foundStopChar = true;
+                continue;
+            }
+            if (!foundStopChar) {
+                if (parserState.typeFilter !== null) {
+                    throw new Error(`Expected \`,\`, \` \` or \`->\`, found \`${c}\``);
+                }
+                throw new Error(`Expected \`,\`, \` \`, \`:\` or \`->\`, found \`${c}\``);
+            }
+            before = query.elems.length;
+            getNextElem(query, parserState, query.elems, false);
+            if (query.elems.length === before) {
+                // Nothing was added, weird... Let's increase the position to not remain stuck.
+                parserState.pos += 1;
+            }
+            foundStopChar = false;
+        }
+        while (parserState.pos < parserState.length) {
+            c = parserState.userQuery[parserState.pos];
+            if (isReturnArrow(parserState)) {
+                parserState.pos += 2;
+                // Get returned elements.
+                getItemsBefore(query, parserState, query.returned, "");
+                // Nothing can come afterward!
+                if (query.returned.length === 0) {
+                    throw new Error("Expected at least one item after `->`");
+                }
+                break;
+            } else {
+                parserState.pos += 1;
+            }
+        }
+    }
+
+    /**
+     * Takes the user search input and returns an empty `ParsedQuery`.
+     *
+     * @param {string} userQuery
+     *
+     * @return {ParsedQuery}
+     */
+    function newParsedQuery(userQuery) {
+        return {
+            original: userQuery,
+            userQuery: userQuery.toLowerCase(),
+            typeFilter: NO_TYPE_FILTER,
+            elems: [],
+            returned: [],
+            // Total number of "top" elements (does not include generics).
+            foundElems: 0,
+            literalSearch: false,
+            error: null,
+        };
+    }
+
+    /**
+     * Build an URL with search parameters.
+     *
+     * @param {string} search            - The current search being performed.
+     * @param {string|null} filterCrates - The current filtering crate (if any).
+     *
+     * @return {string}
+     */
+    function buildUrl(search, filterCrates) {
+        let extra = "?search=" + encodeURIComponent(search);
+
+        if (filterCrates !== null) {
+            extra += "&filter-crate=" + encodeURIComponent(filterCrates);
+        }
+        return getNakedUrl() + extra + window.location.hash;
+    }
+
+    /**
+     * Return the filtering crate or `null` if there is none.
+     *
+     * @return {string|null}
+     */
+    function getFilterCrates() {
+        const elem = document.getElementById("crate-search");
+
+        if (elem &&
+            elem.value !== "All crates" &&
+            hasOwnPropertyRustdoc(rawSearchIndex, elem.value)
+        ) {
+            return elem.value;
+        }
+        return null;
+    }
+
+    /**
+     * Parses the query.
+     *
+     * The supported syntax by this parser is as follow:
+     *
+     * ident = *(ALPHA / DIGIT / "_") [!]
+     * path = ident *(DOUBLE-COLON ident)
+     * arg = path [generics]
+     * arg-without-generic = path
+     * type-sep = COMMA/WS *(COMMA/WS)
+     * nonempty-arg-list = *(type-sep) arg *(type-sep arg) *(type-sep)
+     * nonempty-arg-list-without-generics = *(type-sep) arg-without-generic
+     *                                      *(type-sep arg-without-generic) *(type-sep)
+     * generics = OPEN-ANGLE-BRACKET [ nonempty-arg-list-without-generics ] *(type-sep)
+     *            CLOSE-ANGLE-BRACKET/EOF
+     * return-args = RETURN-ARROW *(type-sep) nonempty-arg-list
+     *
+     * exact-search = [type-filter *WS COLON] [ RETURN-ARROW ] *WS QUOTE ident QUOTE [ generics ]
+     * type-search = [type-filter *WS COLON] [ nonempty-arg-list ] [ return-args ]
+     *
+     * query = *WS (exact-search / type-search) *WS
+     *
+     * type-filter = (
+     *     "mod" /
+     *     "externcrate" /
+     *     "import" /
+     *     "struct" /
+     *     "enum" /
+     *     "fn" /
+     *     "type" /
+     *     "static" /
+     *     "trait" /
+     *     "impl" /
+     *     "tymethod" /
+     *     "method" /
+     *     "structfield" /
+     *     "variant" /
+     *     "macro" /
+     *     "primitive" /
+     *     "associatedtype" /
+     *     "constant" /
+     *     "associatedconstant" /
+     *     "union" /
+     *     "foreigntype" /
+     *     "keyword" /
+     *     "existential" /
+     *     "attr" /
+     *     "derive" /
+     *     "traitalias")
+     *
+     * OPEN-ANGLE-BRACKET = "<"
+     * CLOSE-ANGLE-BRACKET = ">"
+     * COLON = ":"
+     * DOUBLE-COLON = "::"
+     * QUOTE = %x22
+     * COMMA = ","
+     * RETURN-ARROW = "->"
+     *
+     * ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
+     * DIGIT = %x30-39
+     * WS = %x09 / " "
+     *
+     * @param  {string} val     - The user query
+     *
+     * @return {ParsedQuery}    - The parsed query
+     */
+    function parseQuery(userQuery) {
+        userQuery = userQuery.trim();
+        const parserState = {
+            length: userQuery.length,
+            pos: 0,
+            // Total number of elements (includes generics).
+            totalElems: 0,
+            genericsElems: 0,
+            typeFilter: null,
+            userQuery: userQuery.toLowerCase(),
+        };
+        let query = newParsedQuery(userQuery);
+
+        try {
+            parseInput(query, parserState);
+            if (parserState.typeFilter !== null) {
+                let typeFilter = parserState.typeFilter;
+                if (typeFilter === "const") {
+                    typeFilter = "constant";
+                }
+                query.typeFilter = itemTypeFromName(typeFilter);
+            }
+        } catch (err) {
+            query = newParsedQuery(userQuery);
+            query.error = err.message;
+            query.typeFilter = -1;
+            return query;
+        }
+
+        if (!query.literalSearch) {
+            // If there is more than one element in the query, we switch to literalSearch in any
+            // case.
+            query.literalSearch = parserState.totalElems > 1;
+        }
+        query.foundElems = query.elems.length + query.returned.length;
+        return query;
+    }
+
+    /**
+     * Creates the query results.
+     *
+     * @param {Array<Result>} results_in_args
+     * @param {Array<Result>} results_returned
+     * @param {Array<Result>} results_in_args
+     * @param {ParsedQuery} parsedQuery
+     *
+     * @return {ResultsTable}
+     */
+    function createQueryResults(results_in_args, results_returned, results_others, parsedQuery) {
+        return {
+            "in_args": results_in_args,
+            "returned": results_returned,
+            "others": results_others,
+            "query": parsedQuery,
+        };
+    }
+
+    /**
+     * Executes the parsed query and builds a {ResultsTable}.
+     *
+     * @param  {ParsedQuery} parsedQuery - The parsed user query
+     * @param  {Object} searchWords      - The list of search words to query against
+     * @param  {Object} [filterCrates]   - Crate to search in if defined
+     * @param  {Object} [currentCrate]   - Current crate, to rank results from this crate higher
+     *
+     * @return {ResultsTable}
+     */
+    function execQuery(parsedQuery, searchWords, filterCrates, currentCrate) {
+        const results_others = {}, results_in_args = {}, results_returned = {};
+
+        function transformResults(results) {
+            const duplicates = {};
+            const out = [];
+
+            for (const result of results) {
+                if (result.id > -1) {
+                    const obj = searchIndex[result.id];
+                    obj.lev = result.lev;
+                    const res = buildHrefAndPath(obj);
+                    obj.displayPath = pathSplitter(res[0]);
+                    obj.fullPath = obj.displayPath + obj.name;
+                    // To be sure than it some items aren't considered as duplicate.
+                    obj.fullPath += "|" + obj.ty;
+
+                    if (duplicates[obj.fullPath]) {
+                        continue;
+                    }
+                    duplicates[obj.fullPath] = true;
+
+                    obj.href = res[1];
+                    out.push(obj);
+                    if (out.length >= MAX_RESULTS) {
+                        break;
+                    }
+                }
+            }
+            return out;
+        }
+
+        function sortResults(results, isType, preferredCrate) {
+            const userQuery = parsedQuery.userQuery;
+            const ar = [];
+            for (const entry in results) {
+                if (hasOwnPropertyRustdoc(results, entry)) {
+                    const result = results[entry];
+                    result.word = searchWords[result.id];
+                    result.item = searchIndex[result.id] || {};
+                    ar.push(result);
+                }
+            }
+            results = ar;
+            // if there are no results then return to default and fail
+            if (results.length === 0) {
+                return [];
+            }
+
+            results.sort((aaa, bbb) => {
+                let a, b;
+
+                // sort by exact match with regard to the last word (mismatch goes later)
+                a = (aaa.word !== userQuery);
+                b = (bbb.word !== userQuery);
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // Sort by non levenshtein results and then levenshtein results by the distance
+                // (less changes required to match means higher rankings)
+                a = (aaa.lev);
+                b = (bbb.lev);
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // sort by crate (current crate comes first)
+                a = (aaa.item.crate !== preferredCrate);
+                b = (bbb.item.crate !== preferredCrate);
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // sort by item name length (longer goes later)
+                a = aaa.word.length;
+                b = bbb.word.length;
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // sort by item name (lexicographically larger goes later)
+                a = aaa.word;
+                b = bbb.word;
+                if (a !== b) {
+                    return (a > b ? +1 : -1);
+                }
+
+                // sort by index of keyword in item name (no literal occurrence goes later)
+                a = (aaa.index < 0);
+                b = (bbb.index < 0);
+                if (a !== b) {
+                    return a - b;
+                }
+                // (later literal occurrence, if any, goes later)
+                a = aaa.index;
+                b = bbb.index;
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // special precedence for primitive and keyword pages
+                if ((aaa.item.ty === TY_PRIMITIVE && bbb.item.ty !== TY_KEYWORD) ||
+                    (aaa.item.ty === TY_KEYWORD && bbb.item.ty !== TY_PRIMITIVE)) {
+                    return -1;
+                }
+                if ((bbb.item.ty === TY_PRIMITIVE && aaa.item.ty !== TY_PRIMITIVE) ||
+                    (bbb.item.ty === TY_KEYWORD && aaa.item.ty !== TY_KEYWORD)) {
+                    return 1;
+                }
+
+                // sort by description (no description goes later)
+                a = (aaa.item.desc === "");
+                b = (bbb.item.desc === "");
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // sort by type (later occurrence in `itemTypes` goes later)
+                a = aaa.item.ty;
+                b = bbb.item.ty;
+                if (a !== b) {
+                    return a - b;
+                }
+
+                // sort by path (lexicographically larger goes later)
+                a = aaa.item.path;
+                b = bbb.item.path;
+                if (a !== b) {
+                    return (a > b ? +1 : -1);
+                }
+
+                // que sera, sera
+                return 0;
+            });
+
+            let nameSplit = null;
+            if (parsedQuery.elems.length === 1) {
+                const hasPath = typeof parsedQuery.elems[0].path === "undefined";
+                nameSplit = hasPath ? null : parsedQuery.elems[0].path;
+            }
+
+            for (const result of results) {
+                // this validation does not make sense when searching by types
+                if (result.dontValidate) {
+                    continue;
+                }
+                const name = result.item.name.toLowerCase(),
+                    path = result.item.path.toLowerCase(),
+                    parent = result.item.parent;
+
+                if (!isType && !validateResult(name, path, nameSplit, parent)) {
+                    result.id = -1;
+                }
+            }
+            return transformResults(results);
+        }
+
+        /**
+         * This function checks if the object (`row`) generics match the given type (`elem`)
+         * generics. If there are no generics on `row`, `defaultLev` is returned.
+         *
+         * @param {Row} row            - The object to check.
+         * @param {QueryElement} elem  - The element from the parsed query.
+         * @param {integer} defaultLev - This is the value to return in case there are no generics.
+         *
+         * @return {integer}           - Returns the best match (if any) or `MAX_LEV_DISTANCE + 1`.
+         */
+        function checkGenerics(row, elem, defaultLev) {
+            if (row.generics.length === 0) {
+                return elem.generics.length === 0 ? defaultLev : MAX_LEV_DISTANCE + 1;
+            } else if (row.generics.length > 0 && row.generics[0].name === null) {
+                return checkGenerics(row.generics[0], elem, defaultLev);
+            }
+            // The names match, but we need to be sure that all generics kinda
+            // match as well.
+            let elem_name;
+            if (elem.generics.length > 0 && row.generics.length >= elem.generics.length) {
+                const elems = Object.create(null);
+                for (const entry of row.generics) {
+                    elem_name = entry.name;
+                    if (elem_name === "") {
+                        // Pure generic, needs to check into it.
+                        if (checkGenerics(entry, elem, MAX_LEV_DISTANCE + 1) !== 0) {
+                            return MAX_LEV_DISTANCE + 1;
+                        }
+                        continue;
+                    }
+                    if (elems[elem_name] === undefined) {
+                        elems[elem_name] = 0;
+                    }
+                    elems[elem_name] += 1;
+                }
+                // We need to find the type that matches the most to remove it in order
+                // to move forward.
+                for (const generic of elem.generics) {
+                    let match = null;
+                    if (elems[generic.name]) {
+                        match = generic.name;
+                    } else {
+                        for (elem_name in elems) {
+                            if (!hasOwnPropertyRustdoc(elems, elem_name)) {
+                                continue;
+                            }
+                            if (elem_name === generic) {
+                                match = elem_name;
+                                break;
+                            }
+                        }
+                    }
+                    if (match === null) {
+                        return MAX_LEV_DISTANCE + 1;
+                    }
+                    elems[match] -= 1;
+                    if (elems[match] === 0) {
+                        delete elems[match];
+                    }
+                }
+                return 0;
+            }
+            return MAX_LEV_DISTANCE + 1;
+        }
+
+        /**
+          * This function checks if the object (`row`) matches the given type (`elem`) and its
+          * generics (if any).
+          *
+          * @param {Row} row
+          * @param {QueryElement} elem    - The element from the parsed query.
+          *
+          * @return {integer} - Returns a Levenshtein distance to the best match.
+          */
+        function checkIfInGenerics(row, elem) {
+            let lev = MAX_LEV_DISTANCE + 1;
+            for (const entry of row.generics) {
+                lev = Math.min(checkType(entry, elem, true), lev);
+                if (lev === 0) {
+                    break;
+                }
+            }
+            return lev;
+        }
+
+        /**
+          * This function checks if the object (`row`) matches the given type (`elem`) and its
+          * generics (if any).
+          *
+          * @param {Row} row
+          * @param {QueryElement} elem      - The element from the parsed query.
+          * @param {boolean} literalSearch
+          *
+          * @return {integer} - Returns a Levenshtein distance to the best match. If there is
+          *                     no match, returns `MAX_LEV_DISTANCE + 1`.
+          */
+        function checkType(row, elem, literalSearch) {
+            if (row.name === null) {
+                // This is a pure "generic" search, no need to run other checks.
+                if (row.generics.length > 0) {
+                    return checkIfInGenerics(row, elem);
+                }
+                return MAX_LEV_DISTANCE + 1;
+            }
+
+            let lev = levenshtein(row.name, elem.name);
+            if (literalSearch) {
+                if (lev !== 0) {
+                    // The name didn't match, let's try to check if the generics do.
+                    if (elem.generics.length === 0) {
+                        const checkGeneric = row.generics.length > 0;
+                        if (checkGeneric && row.generics
+                            .findIndex(tmp_elem => tmp_elem.name === elem.name) !== -1) {
+                            return 0;
+                        }
+                    }
+                    return MAX_LEV_DISTANCE + 1;
+                } else if (elem.generics.length > 0) {
+                    return checkGenerics(row, elem, MAX_LEV_DISTANCE + 1);
+                }
+                return 0;
+            } else if (row.generics.length > 0) {
+                if (elem.generics.length === 0) {
+                    if (lev === 0) {
+                        return 0;
+                    }
+                    // The name didn't match so we now check if the type we're looking for is inside
+                    // the generics!
+                    lev = checkIfInGenerics(row, elem);
+                    // Now whatever happens, the returned distance is "less good" so we should mark
+                    // it as such, and so we add 0.5 to the distance to make it "less good".
+                    return lev + 0.5;
+                } else if (lev > MAX_LEV_DISTANCE) {
+                    // So our item's name doesn't match at all and has generics.
+                    //
+                    // Maybe it's present in a sub generic? For example "f<A<B<C>>>()", if we're
+                    // looking for "B<C>", we'll need to go down.
+                    return checkIfInGenerics(row, elem);
+                } else {
+                    // At this point, the name kinda match and we have generics to check, so
+                    // let's go!
+                    const tmp_lev = checkGenerics(row, elem, lev);
+                    if (tmp_lev > MAX_LEV_DISTANCE) {
+                        return MAX_LEV_DISTANCE + 1;
+                    }
+                    // We compute the median value of both checks and return it.
+                    return (tmp_lev + lev) / 2;
+                }
+            } else if (elem.generics.length > 0) {
+                // In this case, we were expecting generics but there isn't so we simply reject this
+                // one.
+                return MAX_LEV_DISTANCE + 1;
+            }
+            // No generics on our query or on the target type so we can return without doing
+            // anything else.
+            return lev;
+        }
+
+        /**
+         * This function checks if the object (`row`) has an argument with the given type (`elem`).
+         *
+         * @param {Row} row
+         * @param {QueryElement} elem    - The element from the parsed query.
+         * @param {integer} typeFilter
+         *
+         * @return {integer} - Returns a Levenshtein distance to the best match. If there is no
+         *                      match, returns `MAX_LEV_DISTANCE + 1`.
+         */
+        function findArg(row, elem, typeFilter) {
+            let lev = MAX_LEV_DISTANCE + 1;
+
+            if (row && row.type && row.type.inputs && row.type.inputs.length > 0) {
+                for (const input of row.type.inputs) {
+                    if (!typePassesFilter(typeFilter, input.ty)) {
+                        continue;
+                    }
+                    lev = Math.min(lev, checkType(input, elem, parsedQuery.literalSearch));
+                    if (lev === 0) {
+                        return 0;
+                    }
+                }
+            }
+            return parsedQuery.literalSearch ? MAX_LEV_DISTANCE + 1 : lev;
+        }
+
+        /**
+         * This function checks if the object (`row`) returns the given type (`elem`).
+         *
+         * @param {Row} row
+         * @param {QueryElement} elem   - The element from the parsed query.
+         * @param {integer} typeFilter
+         *
+         * @return {integer} - Returns a Levenshtein distance to the best match. If there is no
+         *                      match, returns `MAX_LEV_DISTANCE + 1`.
+         */
+        function checkReturned(row, elem, typeFilter) {
+            let lev = MAX_LEV_DISTANCE + 1;
+
+            if (row && row.type && row.type.output.length > 0) {
+                const ret = row.type.output;
+                for (const ret_ty of ret) {
+                    if (!typePassesFilter(typeFilter, ret_ty.ty)) {
+                        continue;
+                    }
+                    lev = Math.min(lev, checkType(ret_ty, elem, parsedQuery.literalSearch));
+                    if (lev === 0) {
+                        return 0;
+                    }
+                }
+            }
+            return parsedQuery.literalSearch ? MAX_LEV_DISTANCE + 1 : lev;
+        }
+
+        function checkPath(contains, ty) {
+            if (contains.length === 0) {
+                return 0;
+            }
+            let ret_lev = MAX_LEV_DISTANCE + 1;
+            const path = ty.path.split("::");
+
+            if (ty.parent && ty.parent.name) {
+                path.push(ty.parent.name.toLowerCase());
+            }
+
+            const length = path.length;
+            const clength = contains.length;
+            if (clength > length) {
+                return MAX_LEV_DISTANCE + 1;
+            }
+            for (let i = 0; i < length; ++i) {
+                if (i + clength > length) {
+                    break;
+                }
+                let lev_total = 0;
+                let aborted = false;
+                for (let x = 0; x < clength; ++x) {
+                    const lev = levenshtein(path[i + x], contains[x]);
+                    if (lev > MAX_LEV_DISTANCE) {
+                        aborted = true;
+                        break;
+                    }
+                    lev_total += lev;
+                }
+                if (!aborted) {
+                    ret_lev = Math.min(ret_lev, Math.round(lev_total / clength));
+                }
+            }
+            return ret_lev;
+        }
+
+        function typePassesFilter(filter, type) {
+            // No filter or Exact mach
+            if (filter <= NO_TYPE_FILTER || filter === type) return true;
+
+            // Match related items
+            const name = itemTypes[type];
+            switch (itemTypes[filter]) {
+                case "constant":
+                    return name === "associatedconstant";
+                case "fn":
+                    return name === "method" || name === "tymethod";
+                case "type":
+                    return name === "primitive" || name === "associatedtype";
+                case "trait":
+                    return name === "traitalias";
+            }
+
+            // No match
+            return false;
+        }
+
+        function createAliasFromItem(item) {
+            return {
+                crate: item.crate,
+                name: item.name,
+                path: item.path,
+                desc: item.desc,
+                ty: item.ty,
+                parent: item.parent,
+                type: item.type,
+                is_alias: true,
+            };
+        }
+
+        function handleAliases(ret, query, filterCrates, currentCrate) {
+            const lowerQuery = query.toLowerCase();
+            // We separate aliases and crate aliases because we want to have current crate
+            // aliases to be before the others in the displayed results.
+            const aliases = [];
+            const crateAliases = [];
+            if (filterCrates !== null) {
+                if (ALIASES[filterCrates] && ALIASES[filterCrates][lowerQuery]) {
+                    const query_aliases = ALIASES[filterCrates][lowerQuery];
+                    for (const alias of query_aliases) {
+                        aliases.push(createAliasFromItem(searchIndex[alias]));
+                    }
+                }
+            } else {
+                Object.keys(ALIASES).forEach(crate => {
+                    if (ALIASES[crate][lowerQuery]) {
+                        const pushTo = crate === currentCrate ? crateAliases : aliases;
+                        const query_aliases = ALIASES[crate][lowerQuery];
+                        for (const alias of query_aliases) {
+                            pushTo.push(createAliasFromItem(searchIndex[alias]));
+                        }
+                    }
+                });
+            }
+
+            const sortFunc = (aaa, bbb) => {
+                if (aaa.path < bbb.path) {
+                    return 1;
+                } else if (aaa.path === bbb.path) {
+                    return 0;
+                }
+                return -1;
+            };
+            crateAliases.sort(sortFunc);
+            aliases.sort(sortFunc);
+
+            const pushFunc = alias => {
+                alias.alias = query;
+                const res = buildHrefAndPath(alias);
+                alias.displayPath = pathSplitter(res[0]);
+                alias.fullPath = alias.displayPath + alias.name;
+                alias.href = res[1];
+
+                ret.others.unshift(alias);
+                if (ret.others.length > MAX_RESULTS) {
+                    ret.others.pop();
+                }
+            };
+
+            aliases.forEach(pushFunc);
+            crateAliases.forEach(pushFunc);
+        }
+
+        /**
+         * This function adds the given result into the provided `results` map if it matches the
+         * following condition:
+         *
+         * * If it is a "literal search" (`parsedQuery.literalSearch`), then `lev` must be 0.
+         * * If it is not a "literal search", `lev` must be <= `MAX_LEV_DISTANCE`.
+         *
+         * The `results` map contains information which will be used to sort the search results:
+         *
+         * * `fullId` is a `string`` used as the key of the object we use for the `results` map.
+         * * `id` is the index in both `searchWords` and `searchIndex` arrays for this element.
+         * * `index` is an `integer`` used to sort by the position of the word in the item's name.
+         * * `lev` is the main metric used to sort the search results.
+         *
+         * @param {Results} results
+         * @param {string} fullId
+         * @param {integer} id
+         * @param {integer} index
+         * @param {integer} lev
+         */
+        function addIntoResults(results, fullId, id, index, lev) {
+            if (lev === 0 || (!parsedQuery.literalSearch && lev <= MAX_LEV_DISTANCE)) {
+                if (results[fullId] !== undefined) {
+                    const result = results[fullId];
+                    if (result.dontValidate || result.lev <= lev) {
+                        return;
+                    }
+                }
+                results[fullId] = {
+                    id: id,
+                    index: index,
+                    dontValidate: parsedQuery.literalSearch,
+                    lev: lev,
+                };
+            }
+        }
+
+        /**
+         * This function is called in case the query is only one element (with or without generics).
+         * This element will be compared to arguments' and returned values' items and also to items.
+         *
+         * Other important thing to note: since there is only one element, we use levenshtein
+         * distance for name comparisons.
+         *
+         * @param {Row} row
+         * @param {integer} pos              - Position in the `searchIndex`.
+         * @param {QueryElement} elem        - The element from the parsed query.
+         * @param {Results} results_others   - Unqualified results (not in arguments nor in
+         *                                     returned values).
+         * @param {Results} results_in_args  - Matching arguments results.
+         * @param {Results} results_returned - Matching returned arguments results.
+         */
+        function handleSingleArg(
+            row,
+            pos,
+            elem,
+            results_others,
+            results_in_args,
+            results_returned
+        ) {
+            if (!row || (filterCrates !== null && row.crate !== filterCrates)) {
+                return;
+            }
+            let lev, lev_add = 0, index = -1;
+            const fullId = row.id;
+
+            const in_args = findArg(row, elem, parsedQuery.typeFilter);
+            const returned = checkReturned(row, elem, parsedQuery.typeFilter);
+
+            addIntoResults(results_in_args, fullId, pos, index, in_args);
+            addIntoResults(results_returned, fullId, pos, index, returned);
+
+            if (!typePassesFilter(parsedQuery.typeFilter, row.ty)) {
+                return;
+            }
+            const searchWord = searchWords[pos];
+
+            if (parsedQuery.literalSearch) {
+                if (searchWord === elem.name) {
+                    addIntoResults(results_others, fullId, pos, -1, 0);
+                }
+                return;
+            }
+
+            // No need to check anything else if it's a "pure" generics search.
+            if (elem.name.length === 0) {
+                if (row.type !== null) {
+                    lev = checkGenerics(row.type, elem, MAX_LEV_DISTANCE + 1);
+                    addIntoResults(results_others, fullId, pos, index, lev);
+                }
+                return;
+            }
+
+            if (elem.fullPath.length > 1) {
+                lev = checkPath(elem.pathWithoutLast, row);
+                if (lev > MAX_LEV_DISTANCE || (parsedQuery.literalSearch && lev !== 0)) {
+                    return;
+                } else if (lev > 0) {
+                    lev_add = lev / 10;
+                }
+            }
+
+            if (searchWord.indexOf(elem.pathLast) > -1 ||
+                row.normalizedName.indexOf(elem.pathLast) > -1
+            ) {
+                index = row.normalizedName.indexOf(elem.pathLast);
+            }
+            lev = levenshtein(searchWord, elem.pathLast);
+            if (lev > 0 && elem.pathLast.length > 2 && searchWord.indexOf(elem.pathLast) > -1) {
+                if (elem.pathLast.length < 6) {
+                    lev = 1;
+                } else {
+                    lev = 0;
+                }
+            }
+            lev += lev_add;
+            if (lev > MAX_LEV_DISTANCE) {
+                return;
+            } else if (index !== -1 && elem.fullPath.length < 2) {
+                lev -= 1;
+            }
+            if (lev < 0) {
+                lev = 0;
+            }
+            addIntoResults(results_others, fullId, pos, index, lev);
+        }
+
+        /**
+         * This function is called in case the query has more than one element. In this case, it'll
+         * try to match the items which validates all the elements. For `aa -> bb` will look for
+         * functions which have a parameter `aa` and has `bb` in its returned values.
+         *
+         * @param {Row} row
+         * @param {integer} pos      - Position in the `searchIndex`.
+         * @param {Object} results
+         */
+        function handleArgs(row, pos, results) {
+            if (!row || (filterCrates !== null && row.crate !== filterCrates)) {
+                return;
+            }
+
+            let totalLev = 0;
+            let nbLev = 0;
+
+            // If the result is too "bad", we return false and it ends this search.
+            function checkArgs(elems, callback) {
+                for (const elem of elems) {
+                    // There is more than one parameter to the query so all checks should be "exact"
+                    const lev = callback(row, elem, NO_TYPE_FILTER);
+                    if (lev <= 1) {
+                        nbLev += 1;
+                        totalLev += lev;
+                    } else {
+                        return false;
+                    }
+                }
+                return true;
+            }
+            if (!checkArgs(parsedQuery.elems, findArg)) {
+                return;
+            }
+            if (!checkArgs(parsedQuery.returned, checkReturned)) {
+                return;
+            }
+
+            if (nbLev === 0) {
+                return;
+            }
+            const lev = Math.round(totalLev / nbLev);
+            addIntoResults(results, row.id, pos, 0, lev);
+        }
+
+        function innerRunQuery() {
+            let elem, i, nSearchWords, in_returned, row;
+
+            if (parsedQuery.foundElems === 1) {
+                if (parsedQuery.elems.length === 1) {
+                    elem = parsedQuery.elems[0];
+                    for (i = 0, nSearchWords = searchWords.length; i < nSearchWords; ++i) {
+                        // It means we want to check for this element everywhere (in names, args and
+                        // returned).
+                        handleSingleArg(
+                            searchIndex[i],
+                            i,
+                            elem,
+                            results_others,
+                            results_in_args,
+                            results_returned
+                        );
+                    }
+                } else if (parsedQuery.returned.length === 1) {
+                    // We received one returned argument to check, so looking into returned values.
+                    elem = parsedQuery.returned[0];
+                    for (i = 0, nSearchWords = searchWords.length; i < nSearchWords; ++i) {
+                        row = searchIndex[i];
+                        in_returned = checkReturned(row, elem, parsedQuery.typeFilter);
+                        addIntoResults(results_others, row.id, i, -1, in_returned);
+                    }
+                }
+            } else if (parsedQuery.foundElems > 0) {
+                for (i = 0, nSearchWords = searchWords.length; i < nSearchWords; ++i) {
+                    handleArgs(searchIndex[i], i, results_others);
+                }
+            }
+        }
+
+        if (parsedQuery.error === null) {
+            innerRunQuery();
+        }
+
+        const ret = createQueryResults(
+            sortResults(results_in_args, true, currentCrate),
+            sortResults(results_returned, true, currentCrate),
+            sortResults(results_others, false, currentCrate),
+            parsedQuery);
+        handleAliases(ret, parsedQuery.original.replace(/"/g, ""), filterCrates, currentCrate);
+        if (parsedQuery.error !== null && ret.others.length !== 0) {
+            // It means some doc aliases were found so let's "remove" the error!
+            ret.query.error = null;
+        }
+        return ret;
+    }
+
+    /**
+     * Validate performs the following boolean logic. For example:
+     * "File::open" will give IF A PARENT EXISTS => ("file" && "open")
+     * exists in (name || path || parent) OR => ("file" && "open") exists in
+     * (name || path )
+     *
+     * This could be written functionally, but I wanted to minimise
+     * functions on stack.
+     *
+     * @param  {string} name   - The name of the result
+     * @param  {string} path   - The path of the result
+     * @param  {string} keys   - The keys to be used (["file", "open"])
+     * @param  {Object} parent - The parent of the result
+     *
+     * @return {boolean}       - Whether the result is valid or not
+     */
+    function validateResult(name, path, keys, parent) {
+        if (!keys || !keys.length) {
+            return true;
+        }
+        for (const key of keys) {
+            // each check is for validation so we negate the conditions and invalidate
+            if (!(
+                // check for an exact name match
+                name.indexOf(key) > -1 ||
+                // then an exact path match
+                path.indexOf(key) > -1 ||
+                // next if there is a parent, check for exact parent match
+                (parent !== undefined && parent.name !== undefined &&
+                    parent.name.toLowerCase().indexOf(key) > -1) ||
+                // lastly check to see if the name was a levenshtein match
+                levenshtein(name, key) <= MAX_LEV_DISTANCE)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    function nextTab(direction) {
+        const next = (searchState.currentTab + direction + 3) % searchState.focusedByTab.length;
+        searchState.focusedByTab[searchState.currentTab] = document.activeElement;
+        printTab(next);
+        focusSearchResult();
+    }
+
+    // Focus the first search result on the active tab, or the result that
+    // was focused last time this tab was active.
+    function focusSearchResult() {
+        const target = searchState.focusedByTab[searchState.currentTab] ||
+            document.querySelectorAll(".search-results.active a").item(0) ||
+            document.querySelectorAll("#titles > button").item(searchState.currentTab);
+        if (target) {
+            target.focus();
+        }
+    }
+
+    function buildHrefAndPath(item) {
+        let displayPath;
+        let href;
+        const type = itemTypes[item.ty];
+        const name = item.name;
+        let path = item.path;
+
+        if (type === "mod") {
+            displayPath = path + "::";
+            href = ROOT_PATH + path.replace(/::/g, "/") + "/" +
+                name + "/index.html";
+        } else if (type === "import") {
+            displayPath = item.path + "::";
+            href = ROOT_PATH + item.path.replace(/::/g, "/") + "/index.html#reexport." + name;
+        } else if (type === "primitive" || type === "keyword") {
+            displayPath = "";
+            href = ROOT_PATH + path.replace(/::/g, "/") +
+                "/" + type + "." + name + ".html";
+        } else if (type === "externcrate") {
+            displayPath = "";
+            href = ROOT_PATH + name + "/index.html";
+        } else if (item.parent !== undefined) {
+            const myparent = item.parent;
+            let anchor = "#" + type + "." + name;
+            const parentType = itemTypes[myparent.ty];
+            let pageType = parentType;
+            let pageName = myparent.name;
+
+            if (parentType === "primitive") {
+                displayPath = myparent.name + "::";
+            } else if (type === "structfield" && parentType === "variant") {
+                // Structfields belonging to variants are special: the
+                // final path element is the enum name.
+                const enumNameIdx = item.path.lastIndexOf("::");
+                const enumName = item.path.substr(enumNameIdx + 2);
+                path = item.path.substr(0, enumNameIdx);
+                displayPath = path + "::" + enumName + "::" + myparent.name + "::";
+                anchor = "#variant." + myparent.name + ".field." + name;
+                pageType = "enum";
+                pageName = enumName;
+            } else {
+                displayPath = path + "::" + myparent.name + "::";
+            }
+            href = ROOT_PATH + path.replace(/::/g, "/") +
+                "/" + pageType +
+                "." + pageName +
+                ".html" + anchor;
+        } else {
+            displayPath = item.path + "::";
+            href = ROOT_PATH + item.path.replace(/::/g, "/") +
+                "/" + type + "." + name + ".html";
+        }
+        return [displayPath, href];
+    }
+
+    function escape(content) {
+        const h1 = document.createElement("h1");
+        h1.textContent = content;
+        return h1.innerHTML;
+    }
+
+    function pathSplitter(path) {
+        const tmp = "<span>" + path.replace(/::/g, "::</span><span>");
+        if (tmp.endsWith("<span>")) {
+            return tmp.slice(0, tmp.length - 6);
+        }
+        return tmp;
+    }
+
+    /**
+     * Render a set of search results for a single tab.
+     * @param {Array<?>}    array   - The search results for this tab
+     * @param {ParsedQuery} query
+     * @param {boolean}     display - True if this is the active tab
+     */
+    function addTab(array, query, display) {
+        let extraClass = "";
+        if (display === true) {
+            extraClass = " active";
+        }
+
+        const output = document.createElement("div");
+        let length = 0;
+        if (array.length > 0) {
+            output.className = "search-results " + extraClass;
+
+            array.forEach(item => {
+                const name = item.name;
+                const type = itemTypes[item.ty];
+
+                length += 1;
+
+                let extra = "";
+                if (type === "primitive") {
+                    extra = " <i>(primitive type)</i>";
+                } else if (type === "keyword") {
+                    extra = " <i>(keyword)</i>";
+                }
+
+                const link = document.createElement("a");
+                link.className = "result-" + type;
+                link.href = item.href;
+
+                const wrapper = document.createElement("div");
+                const resultName = document.createElement("div");
+                resultName.className = "result-name";
+
+                if (item.is_alias) {
+                    const alias = document.createElement("span");
+                    alias.className = "alias";
+
+                    const bold = document.createElement("b");
+                    bold.innerText = item.alias;
+                    alias.appendChild(bold);
+
+                    alias.insertAdjacentHTML(
+                        "beforeend",
+                        "<span class=\"grey\"><i>&nbsp;- see&nbsp;</i></span>");
+
+                    resultName.appendChild(alias);
+                }
+                resultName.insertAdjacentHTML(
+                    "beforeend",
+                    item.displayPath + "<span class=\"" + type + "\">" + name + extra + "</span>");
+                wrapper.appendChild(resultName);
+
+                const description = document.createElement("div");
+                description.className = "desc";
+                const spanDesc = document.createElement("span");
+                spanDesc.insertAdjacentHTML("beforeend", item.desc);
+
+                description.appendChild(spanDesc);
+                wrapper.appendChild(description);
+                link.appendChild(wrapper);
+                output.appendChild(link);
+            });
+        } else if (query.error === null) {
+            output.className = "search-failed" + extraClass;
+            output.innerHTML = "No results :(<br/>" +
+                "Try on <a href=\"https://duckduckgo.com/?q=" +
+                encodeURIComponent("rust " + query.userQuery) +
+                "\">DuckDuckGo</a>?<br/><br/>" +
+                "Or try looking in one of these:<ul><li>The <a " +
+                "href=\"https://doc.rust-lang.org/reference/index.html\">Rust Reference</a> " +
+                " for technical details about the language.</li><li><a " +
+                "href=\"https://doc.rust-lang.org/rust-by-example/index.html\">Rust By " +
+                "Example</a> for expository code examples.</a></li><li>The <a " +
+                "href=\"https://doc.rust-lang.org/book/index.html\">Rust Book</a> for " +
+                "introductions to language features and the language itself.</li><li><a " +
+                "href=\"https://docs.rs\">Docs.rs</a> for documentation of crates released on" +
+                " <a href=\"https://crates.io/\">crates.io</a>.</li></ul>";
+        }
+        return [output, length];
+    }
+
+    function makeTabHeader(tabNb, text, nbElems) {
+        if (searchState.currentTab === tabNb) {
+            return "<button class=\"selected\">" + text +
+                   " <div class=\"count\">(" + nbElems + ")</div></button>";
+        }
+        return "<button>" + text + " <div class=\"count\">(" + nbElems + ")</div></button>";
+    }
+
+    /**
+     * @param {ResultsTable} results
+     * @param {boolean} go_to_first
+     * @param {string} filterCrates
+     */
+    function showResults(results, go_to_first, filterCrates) {
+        const search = searchState.outputElement();
+        if (go_to_first || (results.others.length === 1
+            && getSettingValue("go-to-only-result") === "true"
+            // By default, the search DOM element is "empty" (meaning it has no children not
+            // text content). Once a search has been run, it won't be empty, even if you press
+            // ESC or empty the search input (which also "cancels" the search).
+            && (!search.firstChild || search.firstChild.innerText !== searchState.loadingText))
+        ) {
+            const elem = document.createElement("a");
+            elem.href = results.others[0].href;
+            removeClass(elem, "active");
+            // For firefox, we need the element to be in the DOM so it can be clicked.
+            document.body.appendChild(elem);
+            elem.click();
+            return;
+        }
+        if (results.query === undefined) {
+            results.query = parseQuery(searchState.input.value);
+        }
+
+        currentResults = results.query.userQuery;
+
+        const ret_others = addTab(results.others, results.query, true);
+        const ret_in_args = addTab(results.in_args, results.query, false);
+        const ret_returned = addTab(results.returned, results.query, false);
+
+        // Navigate to the relevant tab if the current tab is empty, like in case users search
+        // for "-> String". If they had selected another tab previously, they have to click on
+        // it again.
+        let currentTab = searchState.currentTab;
+        if ((currentTab === 0 && ret_others[1] === 0) ||
+                (currentTab === 1 && ret_in_args[1] === 0) ||
+                (currentTab === 2 && ret_returned[1] === 0)) {
+            if (ret_others[1] !== 0) {
+                currentTab = 0;
+            } else if (ret_in_args[1] !== 0) {
+                currentTab = 1;
+            } else if (ret_returned[1] !== 0) {
+                currentTab = 2;
+            }
+        }
+
+        let crates = "";
+        const crates_list = Object.keys(rawSearchIndex);
+        if (crates_list.length > 1) {
+            crates = " in <select id=\"crate-search\"><option value=\"All crates\">" +
+                "All crates</option>";
+            for (const c of crates_list) {
+                crates += `<option value="${c}" ${c === filterCrates && "selected"}>${c}</option>`;
+            }
+            crates += "</select>";
+        }
+
+        let typeFilter = "";
+        if (results.query.typeFilter !== NO_TYPE_FILTER) {
+            typeFilter = " (type: " + escape(itemTypes[results.query.typeFilter]) + ")";
+        }
+
+        let output = "<div id=\"search-settings\">" +
+            `<h1 class="search-results-title">Results for ${escape(results.query.userQuery)}` +
+            `${typeFilter}</h1>${crates}</div>`;
+        if (results.query.error !== null) {
+            output += `<h3>Query parser error: "${results.query.error}".</h3>`;
+            output += "<div id=\"titles\">" +
+                makeTabHeader(0, "In Names", ret_others[1]) +
+                "</div>";
+            currentTab = 0;
+        } else if (results.query.foundElems <= 1 && results.query.returned.length === 0) {
+            output += "<div id=\"titles\">" +
+                makeTabHeader(0, "In Names", ret_others[1]) +
+                makeTabHeader(1, "In Parameters", ret_in_args[1]) +
+                makeTabHeader(2, "In Return Types", ret_returned[1]) +
+                "</div>";
+        } else {
+            const signatureTabTitle =
+                results.query.elems.length === 0 ? "In Function Return Types" :
+                results.query.returned.length === 0 ? "In Function Parameters" :
+                "In Function Signatures";
+            output += "<div id=\"titles\">" +
+                makeTabHeader(0, signatureTabTitle, ret_others[1]) +
+                "</div>";
+            currentTab = 0;
+        }
+
+        const resultsElem = document.createElement("div");
+        resultsElem.id = "results";
+        resultsElem.appendChild(ret_others[0]);
+        resultsElem.appendChild(ret_in_args[0]);
+        resultsElem.appendChild(ret_returned[0]);
+
+        search.innerHTML = output;
+        const crateSearch = document.getElementById("crate-search");
+        if (crateSearch) {
+            crateSearch.addEventListener("input", updateCrate);
+        }
+        search.appendChild(resultsElem);
+        // Reset focused elements.
+        searchState.showResults(search);
+        const elems = document.getElementById("titles").childNodes;
+        searchState.focusedByTab = [];
+        let i = 0;
+        for (const elem of elems) {
+            const j = i;
+            elem.onclick = () => printTab(j);
+            searchState.focusedByTab.push(null);
+            i += 1;
+        }
+        printTab(currentTab);
+    }
+
+    /**
+     * Perform a search based on the current state of the search input element
+     * and display the results.
+     * @param {Event}   [e]       - The event that triggered this search, if any
+     * @param {boolean} [forced]
+     */
+    function search(e, forced) {
+        const params = searchState.getQueryStringParams();
+        const query = parseQuery(searchState.input.value.trim());
+
+        if (e) {
+            e.preventDefault();
+        }
+
+        if (!forced && query.userQuery === currentResults) {
+            if (query.userQuery.length > 0) {
+                putBackSearch();
+            }
+            return;
+        }
+
+        let filterCrates = getFilterCrates();
+
+        // In case we have no information about the saved crate and there is a URL query parameter,
+        // we override it with the URL query parameter.
+        if (filterCrates === null && params["filter-crate"] !== undefined) {
+            filterCrates = params["filter-crate"];
+        }
+
+        // Update document title to maintain a meaningful browser history
+        searchState.title = "Results for " + query.original + " - Rust";
+
+        // Because searching is incremental by character, only the most
+        // recent search query is added to the browser history.
+        if (browserSupportsHistoryApi()) {
+            const newURL = buildUrl(query.original, filterCrates);
+
+            if (!history.state && !params.search) {
+                history.pushState(null, "", newURL);
+            } else {
+                history.replaceState(null, "", newURL);
+            }
+        }
+
+        showResults(
+            execQuery(query, searchWords, filterCrates, window.currentCrate),
+            params.go_to_first,
+            filterCrates);
+    }
+
+    /**
+     * Convert a list of RawFunctionType / ID to object-based FunctionType.
+     *
+     * Crates often have lots of functions in them, and it's common to have a large number of
+     * functions that operate on a small set of data types, so the search index compresses them
+     * by encoding function parameter and return types as indexes into an array of names.
+     *
+     * Even when a general-purpose compression algorithm is used, this is still a win. I checked.
+     * https://github.com/rust-lang/rust/pull/98475#issue-1284395985
+     *
+     * The format for individual function types is encoded in
+     * librustdoc/html/render/mod.rs: impl Serialize for RenderType
+     *
+     * @param {null|Array<RawFunctionType>} types
+     * @param {Array<{name: string, ty: number}>} lowercasePaths
+     *
+     * @return {Array<FunctionSearchType>}
+     */
+    function buildItemSearchTypeAll(types, lowercasePaths) {
+        const PATH_INDEX_DATA = 0;
+        const GENERICS_DATA = 1;
+        return types.map(type => {
+            let pathIndex, generics;
+            if (typeof type === "number") {
+                pathIndex = type;
+                generics = [];
+            } else {
+                pathIndex = type[PATH_INDEX_DATA];
+                generics = buildItemSearchTypeAll(type[GENERICS_DATA], lowercasePaths);
+            }
+            return {
+                // `0` is used as a sentinel because it's fewer bytes than `null`
+                name: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].name,
+                ty: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].ty,
+                generics: generics,
+            };
+        });
+    }
+
+    /**
+     * Convert from RawFunctionSearchType to FunctionSearchType.
+     *
+     * Crates often have lots of functions in them, and function signatures are sometimes complex,
+     * so rustdoc uses a pretty tight encoding for them. This function converts it to a simpler,
+     * object-based encoding so that the actual search code is more readable and easier to debug.
+     *
+     * The raw function search type format is generated using serde in
+     * librustdoc/html/render/mod.rs: impl Serialize for IndexItemFunctionType
+     *
+     * @param {RawFunctionSearchType} functionSearchType
+     * @param {Array<{name: string, ty: number}>} lowercasePaths
+     *
+     * @return {null|FunctionSearchType}
+     */
+    function buildFunctionSearchType(functionSearchType, lowercasePaths) {
+        const INPUTS_DATA = 0;
+        const OUTPUT_DATA = 1;
+        // `0` is used as a sentinel because it's fewer bytes than `null`
+        if (functionSearchType === 0) {
+            return null;
+        }
+        let inputs, output;
+        if (typeof functionSearchType[INPUTS_DATA] === "number") {
+            const pathIndex = functionSearchType[INPUTS_DATA];
+            inputs = [{
+                name: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].name,
+                ty: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].ty,
+                generics: [],
+            }];
+        } else {
+            inputs = buildItemSearchTypeAll(functionSearchType[INPUTS_DATA], lowercasePaths);
+        }
+        if (functionSearchType.length > 1) {
+            if (typeof functionSearchType[OUTPUT_DATA] === "number") {
+                const pathIndex = functionSearchType[OUTPUT_DATA];
+                output = [{
+                    name: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].name,
+                    ty: pathIndex === 0 ? null : lowercasePaths[pathIndex - 1].ty,
+                    generics: [],
+                }];
+            } else {
+                output = buildItemSearchTypeAll(functionSearchType[OUTPUT_DATA], lowercasePaths);
+            }
+        } else {
+            output = [];
+        }
+        return {
+            inputs, output,
+        };
+    }
+
+    function buildIndex(rawSearchIndex) {
+        searchIndex = [];
+        /**
+         * @type {Array<string>}
+         */
+        const searchWords = [];
+        let i, word;
+        let currentIndex = 0;
+        let id = 0;
+
+        for (const crate in rawSearchIndex) {
+            if (!hasOwnPropertyRustdoc(rawSearchIndex, crate)) {
+                continue;
+            }
+
+            let crateSize = 0;
+
+            /**
+             * The raw search data for a given crate. `n`, `t`, `d`, and `q`, `i`, and `f`
+             * are arrays with the same length. n[i] contains the name of an item.
+             * t[i] contains the type of that item (as a small integer that represents an
+             * offset in `itemTypes`). d[i] contains the description of that item.
+             *
+             * q[i] contains the full path of the item, or an empty string indicating
+             * "same as q[i-1]".
+             *
+             * i[i] contains an item's parent, usually a module. For compactness,
+             * it is a set of indexes into the `p` array.
+             *
+             * f[i] contains function signatures, or `0` if the item isn't a function.
+             * Functions are themselves encoded as arrays. The first item is a list of
+             * types representing the function's inputs, and the second list item is a list
+             * of types representing the function's output. Tuples are flattened.
+             * Types are also represented as arrays; the first item is an index into the `p`
+             * array, while the second is a list of types representing any generic parameters.
+             *
+             * `a` defines aliases with an Array of pairs: [name, offset], where `offset`
+             * points into the n/t/d/q/i/f arrays.
+             *
+             * `doc` contains the description of the crate.
+             *
+             * `p` is a list of path/type pairs. It is used for parents and function parameters.
+             *
+             * @type {{
+             *   doc: string,
+             *   a: Object,
+             *   n: Array<string>,
+             *   t: Array<Number>,
+             *   d: Array<string>,
+             *   q: Array<string>,
+             *   i: Array<Number>,
+             *   f: Array<RawFunctionSearchType>,
+             *   p: Array<Object>,
+             * }}
+             */
+            const crateCorpus = rawSearchIndex[crate];
+
+            searchWords.push(crate);
+            // This object should have exactly the same set of fields as the "row"
+            // object defined below. Your JavaScript runtime will thank you.
+            // https://mathiasbynens.be/notes/shapes-ics
+            const crateRow = {
+                crate: crate,
+                ty: 1, // == ExternCrate
+                name: crate,
+                path: "",
+                desc: crateCorpus.doc,
+                parent: undefined,
+                type: null,
+                id: id,
+                normalizedName: crate.indexOf("_") === -1 ? crate : crate.replace(/_/g, ""),
+            };
+            id += 1;
+            searchIndex.push(crateRow);
+            currentIndex += 1;
+
+            // an array of (Number) item types
+            const itemTypes = crateCorpus.t;
+            // an array of (String) item names
+            const itemNames = crateCorpus.n;
+            // an array of (String) full paths (or empty string for previous path)
+            const itemPaths = crateCorpus.q;
+            // an array of (String) descriptions
+            const itemDescs = crateCorpus.d;
+            // an array of (Number) the parent path index + 1 to `paths`, or 0 if none
+            const itemParentIdxs = crateCorpus.i;
+            // an array of (Object | null) the type of the function, if any
+            const itemFunctionSearchTypes = crateCorpus.f;
+            // an array of [(Number) item type,
+            //              (String) name]
+            const paths = crateCorpus.p;
+            // an array of [(String) alias name
+            //             [Number] index to items]
+            const aliases = crateCorpus.a;
+
+            // an array of [{name: String, ty: Number}]
+            const lowercasePaths = [];
+
+            // convert `rawPaths` entries into object form
+            // generate normalizedPaths for function search mode
+            let len = paths.length;
+            for (i = 0; i < len; ++i) {
+                lowercasePaths.push({ty: paths[i][0], name: paths[i][1].toLowerCase()});
+                paths[i] = {ty: paths[i][0], name: paths[i][1]};
+            }
+
+            // convert `item*` into an object form, and construct word indices.
+            //
+            // before any analysis is performed lets gather the search terms to
+            // search against apart from the rest of the data.  This is a quick
+            // operation that is cached for the life of the page state so that
+            // all other search operations have access to this cached data for
+            // faster analysis operations
+            len = itemTypes.length;
+            let lastPath = "";
+            for (i = 0; i < len; ++i) {
+                // This object should have exactly the same set of fields as the "crateRow"
+                // object defined above.
+                if (typeof itemNames[i] === "string") {
+                    word = itemNames[i].toLowerCase();
+                    searchWords.push(word);
+                } else {
+                    word = "";
+                    searchWords.push("");
+                }
+                const row = {
+                    crate: crate,
+                    ty: itemTypes[i],
+                    name: itemNames[i],
+                    path: itemPaths[i] ? itemPaths[i] : lastPath,
+                    desc: itemDescs[i],
+                    parent: itemParentIdxs[i] > 0 ? paths[itemParentIdxs[i] - 1] : undefined,
+                    type: buildFunctionSearchType(itemFunctionSearchTypes[i], lowercasePaths),
+                    id: id,
+                    normalizedName: word.indexOf("_") === -1 ? word : word.replace(/_/g, ""),
+                };
+                id += 1;
+                searchIndex.push(row);
+                lastPath = row.path;
+                crateSize += 1;
+            }
+
+            if (aliases) {
+                ALIASES[crate] = Object.create(null);
+                for (const alias_name in aliases) {
+                    if (!hasOwnPropertyRustdoc(aliases, alias_name)) {
+                        continue;
+                    }
+
+                    if (!hasOwnPropertyRustdoc(ALIASES[crate], alias_name)) {
+                        ALIASES[crate][alias_name] = [];
+                    }
+                    for (const local_alias of aliases[alias_name]) {
+                        ALIASES[crate][alias_name].push(local_alias + currentIndex);
+                    }
+                }
+            }
+            currentIndex += crateSize;
+        }
+        return searchWords;
+    }
+
+    /**
+     * Callback for when the search form is submitted.
+     * @param {Event} [e] - The event that triggered this call, if any
+     */
+    function onSearchSubmit(e) {
+        e.preventDefault();
+        searchState.clearInputTimeout();
+        search();
+    }
+
+    function putBackSearch() {
+        const search_input = searchState.input;
+        if (!searchState.input) {
+            return;
+        }
+        if (search_input.value !== "" && !searchState.isDisplayed()) {
+            searchState.showResults();
+            if (browserSupportsHistoryApi()) {
+                history.replaceState(null, "",
+                    buildUrl(search_input.value, getFilterCrates()));
+            }
+            document.title = searchState.title;
+        }
+    }
+
+    function registerSearchEvents() {
+        const params = searchState.getQueryStringParams();
+
+        // Populate search bar with query string search term when provided,
+        // but only if the input bar is empty. This avoid the obnoxious issue
+        // where you start trying to do a search, and the index loads, and
+        // suddenly your search is gone!
+        if (searchState.input.value === "") {
+            searchState.input.value = params.search || "";
+        }
+
+        const searchAfter500ms = () => {
+            searchState.clearInputTimeout();
+            if (searchState.input.value.length === 0) {
+                if (browserSupportsHistoryApi()) {
+                    history.replaceState(null, window.currentCrate + " - Rust",
+                        getNakedUrl() + window.location.hash);
+                }
+                searchState.hideResults();
+            } else {
+                searchState.timeout = setTimeout(search, 500);
+            }
+        };
+        searchState.input.onkeyup = searchAfter500ms;
+        searchState.input.oninput = searchAfter500ms;
+        document.getElementsByClassName("search-form")[0].onsubmit = onSearchSubmit;
+        searchState.input.onchange = e => {
+            if (e.target !== document.activeElement) {
+                // To prevent doing anything when it's from a blur event.
+                return;
+            }
+            // Do NOT e.preventDefault() here. It will prevent pasting.
+            searchState.clearInputTimeout();
+            // zero-timeout necessary here because at the time of event handler execution the
+            // pasted content is not in the input field yet. Shouldn’t make any difference for
+            // change, though.
+            setTimeout(search, 0);
+        };
+        searchState.input.onpaste = searchState.input.onchange;
+
+        searchState.outputElement().addEventListener("keydown", e => {
+            // We only handle unmodified keystrokes here. We don't want to interfere with,
+            // for instance, alt-left and alt-right for history navigation.
+            if (e.altKey || e.ctrlKey || e.shiftKey || e.metaKey) {
+                return;
+            }
+            // up and down arrow select next/previous search result, or the
+            // search box if we're already at the top.
+            if (e.which === 38) { // up
+                const previous = document.activeElement.previousElementSibling;
+                if (previous) {
+                    previous.focus();
+                } else {
+                    searchState.focus();
+                }
+                e.preventDefault();
+            } else if (e.which === 40) { // down
+                const next = document.activeElement.nextElementSibling;
+                if (next) {
+                    next.focus();
+                }
+                const rect = document.activeElement.getBoundingClientRect();
+                if (window.innerHeight - rect.bottom < rect.height) {
+                    window.scrollBy(0, rect.height);
+                }
+                e.preventDefault();
+            } else if (e.which === 37) { // left
+                nextTab(-1);
+                e.preventDefault();
+            } else if (e.which === 39) { // right
+                nextTab(1);
+                e.preventDefault();
+            }
+        });
+
+        searchState.input.addEventListener("keydown", e => {
+            if (e.which === 40) { // down
+                focusSearchResult();
+                e.preventDefault();
+            }
+        });
+
+        searchState.input.addEventListener("focus", () => {
+            putBackSearch();
+        });
+
+        searchState.input.addEventListener("blur", () => {
+            searchState.input.placeholder = searchState.input.origPlaceholder;
+        });
+
+        // Push and pop states are used to add search results to the browser
+        // history.
+        if (browserSupportsHistoryApi()) {
+            // Store the previous <title> so we can revert back to it later.
+            const previousTitle = document.title;
+
+            window.addEventListener("popstate", e => {
+                const params = searchState.getQueryStringParams();
+                // Revert to the previous title manually since the History
+                // API ignores the title parameter.
+                document.title = previousTitle;
+                // When browsing forward to search results the previous
+                // search will be repeated, so the currentResults are
+                // cleared to ensure the search is successful.
+                currentResults = null;
+                // Synchronize search bar with query string state and
+                // perform the search. This will empty the bar if there's
+                // nothing there, which lets you really go back to a
+                // previous state with nothing in the bar.
+                if (params.search && params.search.length > 0) {
+                    searchState.input.value = params.search;
+                    // Some browsers fire "onpopstate" for every page load
+                    // (Chrome), while others fire the event only when actually
+                    // popping a state (Firefox), which is why search() is
+                    // called both here and at the end of the startSearch()
+                    // function.
+                    search(e);
+                } else {
+                    searchState.input.value = "";
+                    // When browsing back from search results the main page
+                    // visibility must be reset.
+                    searchState.hideResults();
+                }
+            });
+        }
+
+        // This is required in firefox to avoid this problem: Navigating to a search result
+        // with the keyboard, hitting enter, and then hitting back would take you back to
+        // the doc page, rather than the search that should overlay it.
+        // This was an interaction between the back-forward cache and our handlers
+        // that try to sync state between the URL and the search input. To work around it,
+        // do a small amount of re-init on page show.
+        window.onpageshow = () => {
+            const qSearch = searchState.getQueryStringParams().search;
+            if (searchState.input.value === "" && qSearch) {
+                searchState.input.value = qSearch;
+            }
+            search();
+        };
+    }
+
+    function updateCrate(ev) {
+        if (ev.target.value === "All crates") {
+            // If we don't remove it from the URL, it'll be picked up again by the search.
+            const params = searchState.getQueryStringParams();
+            const query = searchState.input.value.trim();
+            if (!history.state && !params.search) {
+                history.pushState(null, "", buildUrl(query, null));
+            } else {
+                history.replaceState(null, "", buildUrl(query, null));
+            }
+        }
+        // In case you "cut" the entry from the search input, then change the crate filter
+        // before paste back the previous search, you get the old search results without
+        // the filter. To prevent this, we need to remove the previous results.
+        currentResults = null;
+        search(undefined, true);
+    }
+
+    /**
+     *  @type {Array<string>}
+     */
+    const searchWords = buildIndex(rawSearchIndex);
+    if (typeof window !== "undefined") {
+        registerSearchEvents();
+        // If there's a search term in the URL, execute the search now.
+        if (window.searchState.getQueryStringParams().search) {
+            search();
+        }
+    }
+
+    if (typeof exports !== "undefined") {
+        exports.initSearch = initSearch;
+        exports.execQuery = execQuery;
+        exports.parseQuery = parseQuery;
+    }
+    return searchWords;
+}
+
+if (typeof window !== "undefined") {
+    window.initSearch = initSearch;
+    if (window.searchIndex !== undefined) {
+        initSearch(window.searchIndex);
+    }
+} else {
+    // Running in Node, not a browser. Run initSearch just to produce the
+    // exports.
+    initSearch({});
+}
+
+
+})();
diff --git a/src/librustdoc/html/static/js/settings.js b/src/librustdoc/html/static/js/settings.js
new file mode 100644
index 000000000..797b931af
--- /dev/null
+++ b/src/librustdoc/html/static/js/settings.js
@@ -0,0 +1,272 @@
+// Local js definitions:
+/* global getSettingValue, getVirtualKey, updateLocalStorage, updateSystemTheme */
+/* global addClass, removeClass, onEach, onEachLazy, blurHandler, elemIsInParent */
+/* global MAIN_ID, getVar, getSettingsButton */
+
+"use strict";
+
+(function() {
+    const isSettingsPage = window.location.pathname.endsWith("/settings.html");
+
+    function changeSetting(settingName, value) {
+        updateLocalStorage(settingName, value);
+
+        switch (settingName) {
+            case "theme":
+            case "preferred-dark-theme":
+            case "preferred-light-theme":
+            case "use-system-theme":
+                updateSystemTheme();
+                updateLightAndDark();
+                break;
+        }
+    }
+
+    function handleKey(ev) {
+        // Don't interfere with browser shortcuts
+        if (ev.ctrlKey || ev.altKey || ev.metaKey) {
+            return;
+        }
+        switch (getVirtualKey(ev)) {
+            case "Enter":
+            case "Return":
+            case "Space":
+                ev.target.checked = !ev.target.checked;
+                ev.preventDefault();
+                break;
+        }
+    }
+
+    function showLightAndDark() {
+        addClass(document.getElementById("theme").parentElement, "hidden");
+        removeClass(document.getElementById("preferred-light-theme").parentElement, "hidden");
+        removeClass(document.getElementById("preferred-dark-theme").parentElement, "hidden");
+    }
+
+    function hideLightAndDark() {
+        addClass(document.getElementById("preferred-light-theme").parentElement, "hidden");
+        addClass(document.getElementById("preferred-dark-theme").parentElement, "hidden");
+        removeClass(document.getElementById("theme").parentElement, "hidden");
+    }
+
+    function updateLightAndDark() {
+        if (getSettingValue("use-system-theme") !== "false") {
+            showLightAndDark();
+        } else {
+            hideLightAndDark();
+        }
+    }
+
+    function setEvents(settingsElement) {
+        updateLightAndDark();
+        onEachLazy(settingsElement.getElementsByClassName("slider"), elem => {
+            const toggle = elem.previousElementSibling;
+            const settingId = toggle.id;
+            const settingValue = getSettingValue(settingId);
+            if (settingValue !== null) {
+                toggle.checked = settingValue === "true";
+            }
+            toggle.onchange = function() {
+                changeSetting(this.id, this.checked);
+            };
+            toggle.onkeyup = handleKey;
+            toggle.onkeyrelease = handleKey;
+        });
+        onEachLazy(settingsElement.getElementsByClassName("select-wrapper"), elem => {
+            const select = elem.getElementsByTagName("select")[0];
+            const settingId = select.id;
+            const settingValue = getSettingValue(settingId);
+            if (settingValue !== null) {
+                select.value = settingValue;
+            }
+            select.onchange = function() {
+                changeSetting(this.id, this.value);
+            };
+        });
+        onEachLazy(settingsElement.querySelectorAll("input[type=\"radio\"]"), elem => {
+            const settingId = elem.name;
+            const settingValue = getSettingValue(settingId);
+            if (settingValue !== null && settingValue !== "null") {
+                elem.checked = settingValue === elem.value;
+            }
+            elem.addEventListener("change", ev => {
+                changeSetting(ev.target.name, ev.target.value);
+            });
+        });
+    }
+
+    /**
+     * This function builds the sections inside the "settings page". It takes a `settings` list
+     * as argument which describes each setting and how to render it. It returns a string
+     * representing the raw HTML.
+     *
+     * @param {Array<Object>} settings
+     *
+     * @return {string}
+     */
+    function buildSettingsPageSections(settings) {
+        let output = "";
+
+        for (const setting of settings) {
+            output += "<div class=\"setting-line\">";
+            const js_data_name = setting["js_name"];
+            const setting_name = setting["name"];
+
+            if (setting["options"] !== undefined) {
+                // This is a select setting.
+                output += `<div class="radio-line" id="${js_data_name}">\
+                        <span class="setting-name">${setting_name}</span>\
+                        <div class="choices">`;
+                onEach(setting["options"], option => {
+                    const checked = option === setting["default"] ? " checked" : "";
+
+                    output += `<label for="${js_data_name}-${option}" class="choice">\
+                           <input type="radio" name="${js_data_name}" \
+                                id="${js_data_name}-${option}" value="${option}"${checked}>\
+                           <span>${option}</span>\
+                         </label>`;
+                });
+                output += "</div></div>";
+            } else {
+                // This is a toggle.
+                const checked = setting["default"] === true ? " checked" : "";
+                output += `<label class="toggle">\
+                        <input type="checkbox" id="${js_data_name}"${checked}>\
+                        <span class="slider"></span>\
+                        <span class="label">${setting_name}</span>\
+                    </label>`;
+            }
+            output += "</div>";
+        }
+        return output;
+    }
+
+    /**
+     * This function builds the "settings page" and returns the generated HTML element.
+     *
+     * @return {HTMLElement}
+     */
+    function buildSettingsPage() {
+        const themes = getVar("themes").split(",");
+        const settings = [
+            {
+                "name": "Use system theme",
+                "js_name": "use-system-theme",
+                "default": true,
+            },
+            {
+                "name": "Theme",
+                "js_name": "theme",
+                "default": "light",
+                "options": themes,
+            },
+            {
+                "name": "Preferred light theme",
+                "js_name": "preferred-light-theme",
+                "default": "light",
+                "options": themes,
+            },
+            {
+                "name": "Preferred dark theme",
+                "js_name": "preferred-dark-theme",
+                "default": "dark",
+                "options": themes,
+            },
+            {
+                "name": "Auto-hide item contents for large items",
+                "js_name": "auto-hide-large-items",
+                "default": true,
+            },
+            {
+                "name": "Auto-hide item methods' documentation",
+                "js_name": "auto-hide-method-docs",
+                "default": false,
+            },
+            {
+                "name": "Auto-hide trait implementation documentation",
+                "js_name": "auto-hide-trait-implementations",
+                "default": false,
+            },
+            {
+                "name": "Directly go to item in search if there is only one result",
+                "js_name": "go-to-only-result",
+                "default": false,
+            },
+            {
+                "name": "Show line numbers on code examples",
+                "js_name": "line-numbers",
+                "default": false,
+            },
+            {
+                "name": "Disable keyboard shortcuts",
+                "js_name": "disable-shortcuts",
+                "default": false,
+            },
+        ];
+
+        // Then we build the DOM.
+        const elementKind = isSettingsPage ? "section" : "div";
+        const innerHTML = `<div class="settings">${buildSettingsPageSections(settings)}</div>`;
+        const el = document.createElement(elementKind);
+        el.id = "settings";
+        el.className = "popover";
+        el.innerHTML = innerHTML;
+
+        if (isSettingsPage) {
+            document.getElementById(MAIN_ID).appendChild(el);
+        } else {
+            el.setAttribute("tabindex", "-1");
+            getSettingsButton().appendChild(el);
+        }
+        return el;
+    }
+
+    const settingsMenu = buildSettingsPage();
+
+    function displaySettings() {
+        settingsMenu.style.display = "";
+    }
+
+    function settingsBlurHandler(event) {
+        blurHandler(event, getSettingsButton(), window.hidePopoverMenus);
+    }
+
+    if (isSettingsPage) {
+        // We replace the existing "onclick" callback to do nothing if clicked.
+        getSettingsButton().onclick = function(event) {
+            event.preventDefault();
+        };
+    } else {
+        // We replace the existing "onclick" callback.
+        const settingsButton = getSettingsButton();
+        const settingsMenu = document.getElementById("settings");
+        settingsButton.onclick = function(event) {
+            if (elemIsInParent(event.target, settingsMenu)) {
+                return;
+            }
+            event.preventDefault();
+            const shouldDisplaySettings = settingsMenu.style.display === "none";
+
+            window.hidePopoverMenus();
+            if (shouldDisplaySettings) {
+                displaySettings();
+            }
+        };
+        settingsButton.onblur = settingsBlurHandler;
+        settingsButton.querySelector("a").onblur = settingsBlurHandler;
+        onEachLazy(settingsMenu.querySelectorAll("input"), el => {
+            el.onblur = settingsBlurHandler;
+        });
+        settingsMenu.onblur = settingsBlurHandler;
+    }
+
+    // We now wait a bit for the web browser to end re-computing the DOM...
+    setTimeout(() => {
+        setEvents(settingsMenu);
+        // The setting menu is already displayed if we're on the settings page.
+        if (!isSettingsPage) {
+            displaySettings();
+        }
+        removeClass(getSettingsButton(), "rotate");
+    }, 0);
+})();
diff --git a/src/librustdoc/html/static/js/source-script.js b/src/librustdoc/html/static/js/source-script.js
new file mode 100644
index 000000000..c45d61429
--- /dev/null
+++ b/src/librustdoc/html/static/js/source-script.js
@@ -0,0 +1,241 @@
+// From rust:
+/* global sourcesIndex */
+
+// Local js definitions:
+/* global addClass, getCurrentValue, onEachLazy, removeClass, browserSupportsHistoryApi */
+/* global updateLocalStorage */
+
+"use strict";
+
+(function() {
+
+const rootPath = document.getElementById("rustdoc-vars").attributes["data-root-path"].value;
+let oldScrollPosition = 0;
+
+const NAME_OFFSET = 0;
+const DIRS_OFFSET = 1;
+const FILES_OFFSET = 2;
+
+function closeSidebarIfMobile() {
+    if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+        updateLocalStorage("source-sidebar-show", "false");
+    }
+}
+
+function createDirEntry(elem, parent, fullPath, hasFoundFile) {
+    const dirEntry = document.createElement("details");
+    const summary = document.createElement("summary");
+
+    dirEntry.className = "dir-entry";
+
+    fullPath += elem[NAME_OFFSET] + "/";
+
+    summary.innerText = elem[NAME_OFFSET];
+    dirEntry.appendChild(summary);
+
+    const folders = document.createElement("div");
+    folders.className = "folders";
+    if (elem[DIRS_OFFSET]) {
+        for (const dir of elem[DIRS_OFFSET]) {
+            if (createDirEntry(dir, folders, fullPath, false)) {
+                dirEntry.open = true;
+                hasFoundFile = true;
+            }
+        }
+    }
+    dirEntry.appendChild(folders);
+
+    const files = document.createElement("div");
+    files.className = "files";
+    if (elem[FILES_OFFSET]) {
+        for (const file_text of elem[FILES_OFFSET]) {
+            const file = document.createElement("a");
+            file.innerText = file_text;
+            file.href = rootPath + "src/" + fullPath + file_text + ".html";
+            file.addEventListener("click", closeSidebarIfMobile);
+            const w = window.location.href.split("#")[0];
+            if (!hasFoundFile && w === file.href) {
+                file.className = "selected";
+                dirEntry.open = true;
+                hasFoundFile = true;
+            }
+            files.appendChild(file);
+        }
+    }
+    dirEntry.appendChild(files);
+    parent.appendChild(dirEntry);
+    return hasFoundFile;
+}
+
+function toggleSidebar() {
+    const child = this.parentNode.children[0];
+    if (child.innerText === ">") {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+            // This is to keep the scroll position on mobile.
+            oldScrollPosition = window.scrollY;
+            document.body.style.position = "fixed";
+            document.body.style.top = `-${oldScrollPosition}px`;
+        }
+        addClass(document.documentElement, "source-sidebar-expanded");
+        child.innerText = "<";
+        updateLocalStorage("source-sidebar-show", "true");
+    } else {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+            // This is to keep the scroll position on mobile.
+            document.body.style.position = "";
+            document.body.style.top = "";
+            // The scroll position is lost when resetting the style, hence why we store it in
+            // `oldScroll`.
+            window.scrollTo(0, oldScrollPosition);
+        }
+        removeClass(document.documentElement, "source-sidebar-expanded");
+        child.innerText = ">";
+        updateLocalStorage("source-sidebar-show", "false");
+    }
+}
+
+function createSidebarToggle() {
+    const sidebarToggle = document.createElement("div");
+    sidebarToggle.id = "sidebar-toggle";
+
+    const inner = document.createElement("button");
+
+    if (getCurrentValue("source-sidebar-show") === "true") {
+        inner.innerText = "<";
+    } else {
+        inner.innerText = ">";
+    }
+    inner.onclick = toggleSidebar;
+
+    sidebarToggle.appendChild(inner);
+    return sidebarToggle;
+}
+
+// This function is called from "source-files.js", generated in `html/render/mod.rs`.
+// eslint-disable-next-line no-unused-vars
+function createSourceSidebar() {
+    const container = document.querySelector("nav.sidebar");
+
+    const sidebarToggle = createSidebarToggle();
+    container.insertBefore(sidebarToggle, container.firstChild);
+
+    const sidebar = document.createElement("div");
+    sidebar.id = "source-sidebar";
+
+    let hasFoundFile = false;
+
+    const title = document.createElement("div");
+    title.className = "title";
+    title.innerText = "Files";
+    sidebar.appendChild(title);
+    Object.keys(sourcesIndex).forEach(key => {
+        sourcesIndex[key][NAME_OFFSET] = key;
+        hasFoundFile = createDirEntry(sourcesIndex[key], sidebar, "",
+            hasFoundFile);
+    });
+
+    container.appendChild(sidebar);
+    // Focus on the current file in the source files sidebar.
+    const selected_elem = sidebar.getElementsByClassName("selected")[0];
+    if (typeof selected_elem !== "undefined") {
+        selected_elem.focus();
+    }
+}
+
+const lineNumbersRegex = /^#?(\d+)(?:-(\d+))?$/;
+
+function highlightSourceLines(match) {
+    if (typeof match === "undefined") {
+        match = window.location.hash.match(lineNumbersRegex);
+    }
+    if (!match) {
+        return;
+    }
+    let from = parseInt(match[1], 10);
+    let to = from;
+    if (typeof match[2] !== "undefined") {
+        to = parseInt(match[2], 10);
+    }
+    if (to < from) {
+        const tmp = to;
+        to = from;
+        from = tmp;
+    }
+    let elem = document.getElementById(from);
+    if (!elem) {
+        return;
+    }
+    const x = document.getElementById(from);
+    if (x) {
+        x.scrollIntoView();
+    }
+    onEachLazy(document.getElementsByClassName("line-numbers"), e => {
+        onEachLazy(e.getElementsByTagName("span"), i_e => {
+            removeClass(i_e, "line-highlighted");
+        });
+    });
+    for (let i = from; i <= to; ++i) {
+        elem = document.getElementById(i);
+        if (!elem) {
+            break;
+        }
+        addClass(elem, "line-highlighted");
+    }
+}
+
+const handleSourceHighlight = (function() {
+    let prev_line_id = 0;
+
+    const set_fragment = name => {
+        const x = window.scrollX,
+            y = window.scrollY;
+        if (browserSupportsHistoryApi()) {
+            history.replaceState(null, null, "#" + name);
+            highlightSourceLines();
+        } else {
+            location.replace("#" + name);
+        }
+        // Prevent jumps when selecting one or many lines
+        window.scrollTo(x, y);
+    };
+
+    return ev => {
+        let cur_line_id = parseInt(ev.target.id, 10);
+        // It can happen when clicking not on a line number span.
+        if (isNaN(cur_line_id)) {
+            return;
+        }
+        ev.preventDefault();
+
+        if (ev.shiftKey && prev_line_id) {
+            // Swap selection if needed
+            if (prev_line_id > cur_line_id) {
+                const tmp = prev_line_id;
+                prev_line_id = cur_line_id;
+                cur_line_id = tmp;
+            }
+
+            set_fragment(prev_line_id + "-" + cur_line_id);
+        } else {
+            prev_line_id = cur_line_id;
+
+            set_fragment(cur_line_id);
+        }
+    };
+}());
+
+window.addEventListener("hashchange", () => {
+    const match = window.location.hash.match(lineNumbersRegex);
+    if (match) {
+        return highlightSourceLines(match);
+    }
+});
+
+onEachLazy(document.getElementsByClassName("line-numbers"), el => {
+    el.addEventListener("click", handleSourceHighlight);
+});
+
+highlightSourceLines();
+
+window.createSourceSidebar = createSourceSidebar;
+})();
diff --git a/src/librustdoc/html/static/js/storage.js b/src/librustdoc/html/static/js/storage.js
new file mode 100644
index 000000000..0c5389d45
--- /dev/null
+++ b/src/librustdoc/html/static/js/storage.js
@@ -0,0 +1,268 @@
+// storage.js is loaded in the `<head>` of all rustdoc pages and doesn't
+// use `async` or `defer`. That means it blocks further parsing and rendering
+// of the page: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script.
+// This makes it the correct place to act on settings that affect the display of
+// the page, so we don't see major layout changes during the load of the page.
+"use strict";
+
+const darkThemes = ["dark", "ayu"];
+window.currentTheme = document.getElementById("themeStyle");
+window.mainTheme = document.getElementById("mainThemeStyle");
+
+// WARNING: RUSTDOC_MOBILE_BREAKPOINT MEDIA QUERY
+// If you update this line, then you also need to update the two media queries with the same
+// warning in rustdoc.css
+window.RUSTDOC_MOBILE_BREAKPOINT = 701;
+
+const settingsDataset = (function() {
+    const settingsElement = document.getElementById("default-settings");
+    if (settingsElement === null) {
+        return null;
+    }
+    const dataset = settingsElement.dataset;
+    if (dataset === undefined) {
+        return null;
+    }
+    return dataset;
+})();
+
+function getSettingValue(settingName) {
+    const current = getCurrentValue(settingName);
+    if (current !== null) {
+        return current;
+    }
+    if (settingsDataset !== null) {
+        // See the comment for `default_settings.into_iter()` etc. in
+        // `Options::from_matches` in `librustdoc/config.rs`.
+        const def = settingsDataset[settingName.replace(/-/g,"_")];
+        if (def !== undefined) {
+            return def;
+        }
+    }
+    return null;
+}
+
+const localStoredTheme = getSettingValue("theme");
+
+const savedHref = [];
+
+// eslint-disable-next-line no-unused-vars
+function hasClass(elem, className) {
+    return elem && elem.classList && elem.classList.contains(className);
+}
+
+// eslint-disable-next-line no-unused-vars
+function addClass(elem, className) {
+    if (!elem || !elem.classList) {
+        return;
+    }
+    elem.classList.add(className);
+}
+
+// eslint-disable-next-line no-unused-vars
+function removeClass(elem, className) {
+    if (!elem || !elem.classList) {
+        return;
+    }
+    elem.classList.remove(className);
+}
+
+/**
+ * Run a callback for every element of an Array.
+ * @param {Array<?>}    arr        - The array to iterate over
+ * @param {function(?)} func       - The callback
+ * @param {boolean}     [reversed] - Whether to iterate in reverse
+ */
+function onEach(arr, func, reversed) {
+    if (arr && arr.length > 0 && func) {
+        if (reversed) {
+            const length = arr.length;
+            for (let i = length - 1; i >= 0; --i) {
+                if (func(arr[i])) {
+                    return true;
+                }
+            }
+        } else {
+            for (const elem of arr) {
+                if (func(elem)) {
+                    return true;
+                }
+            }
+        }
+    }
+    return false;
+}
+
+/**
+ * Turn an HTMLCollection or a NodeList into an Array, then run a callback
+ * for every element. This is useful because iterating over an HTMLCollection
+ * or a "live" NodeList while modifying it can be very slow.
+ * https://developer.mozilla.org/en-US/docs/Web/API/HTMLCollection
+ * https://developer.mozilla.org/en-US/docs/Web/API/NodeList
+ * @param {NodeList<?>|HTMLCollection<?>} lazyArray  - An array to iterate over
+ * @param {function(?)}                   func       - The callback
+ * @param {boolean}                       [reversed] - Whether to iterate in reverse
+ */
+function onEachLazy(lazyArray, func, reversed) {
+    return onEach(
+        Array.prototype.slice.call(lazyArray),
+        func,
+        reversed);
+}
+
+function updateLocalStorage(name, value) {
+    try {
+        window.localStorage.setItem("rustdoc-" + name, value);
+    } catch (e) {
+        // localStorage is not accessible, do nothing
+    }
+}
+
+function getCurrentValue(name) {
+    try {
+        return window.localStorage.getItem("rustdoc-" + name);
+    } catch (e) {
+        return null;
+    }
+}
+
+function switchTheme(styleElem, mainStyleElem, newTheme, saveTheme) {
+    const newHref = mainStyleElem.href.replace(
+        /\/rustdoc([^/]*)\.css/, "/" + newTheme + "$1" + ".css");
+
+    // If this new value comes from a system setting or from the previously
+    // saved theme, no need to save it.
+    if (saveTheme) {
+        updateLocalStorage("theme", newTheme);
+    }
+
+    if (styleElem.href === newHref) {
+        return;
+    }
+
+    let found = false;
+    if (savedHref.length === 0) {
+        onEachLazy(document.getElementsByTagName("link"), el => {
+            savedHref.push(el.href);
+        });
+    }
+    onEach(savedHref, el => {
+        if (el === newHref) {
+            found = true;
+            return true;
+        }
+    });
+    if (found) {
+        styleElem.href = newHref;
+    }
+}
+
+// This function is called from "main.js".
+// eslint-disable-next-line no-unused-vars
+function useSystemTheme(value) {
+    if (value === undefined) {
+        value = true;
+    }
+
+    updateLocalStorage("use-system-theme", value);
+
+    // update the toggle if we're on the settings page
+    const toggle = document.getElementById("use-system-theme");
+    if (toggle && toggle instanceof HTMLInputElement) {
+        toggle.checked = value;
+    }
+}
+
+const updateSystemTheme = (function() {
+    if (!window.matchMedia) {
+        // fallback to the CSS computed value
+        return () => {
+            const cssTheme = getComputedStyle(document.documentElement)
+                .getPropertyValue("content");
+
+            switchTheme(
+                window.currentTheme,
+                window.mainTheme,
+                JSON.parse(cssTheme) || "light",
+                true
+            );
+        };
+    }
+
+    // only listen to (prefers-color-scheme: dark) because light is the default
+    const mql = window.matchMedia("(prefers-color-scheme: dark)");
+
+    function handlePreferenceChange(mql) {
+        const use = theme => {
+            switchTheme(window.currentTheme, window.mainTheme, theme, true);
+        };
+        // maybe the user has disabled the setting in the meantime!
+        if (getSettingValue("use-system-theme") !== "false") {
+            const lightTheme = getSettingValue("preferred-light-theme") || "light";
+            const darkTheme = getSettingValue("preferred-dark-theme") || "dark";
+
+            if (mql.matches) {
+                use(darkTheme);
+            } else {
+                // prefers a light theme, or has no preference
+                use(lightTheme);
+            }
+            // note: we save the theme so that it doesn't suddenly change when
+            // the user disables "use-system-theme" and reloads the page or
+            // navigates to another page
+        } else {
+            use(getSettingValue("theme"));
+        }
+    }
+
+    mql.addListener(handlePreferenceChange);
+
+    return () => {
+        handlePreferenceChange(mql);
+    };
+})();
+
+function switchToSavedTheme() {
+    switchTheme(
+        window.currentTheme,
+        window.mainTheme,
+        getSettingValue("theme") || "light",
+        false
+    );
+}
+
+if (getSettingValue("use-system-theme") !== "false" && window.matchMedia) {
+    // update the preferred dark theme if the user is already using a dark theme
+    // See https://github.com/rust-lang/rust/pull/77809#issuecomment-707875732
+    if (getSettingValue("use-system-theme") === null
+        && getSettingValue("preferred-dark-theme") === null
+        && darkThemes.indexOf(localStoredTheme) >= 0) {
+        updateLocalStorage("preferred-dark-theme", localStoredTheme);
+    }
+
+    // call the function to initialize the theme at least once!
+    updateSystemTheme();
+} else {
+    switchToSavedTheme();
+}
+
+if (getSettingValue("source-sidebar-show") === "true") {
+    // At this point in page load, `document.body` is not available yet.
+    // Set a class on the `<html>` element instead.
+    addClass(document.documentElement, "source-sidebar-expanded");
+}
+
+// If we navigate away (for example to a settings page), and then use the back or
+// forward button to get back to a page, the theme may have changed in the meantime.
+// But scripts may not be re-loaded in such a case due to the bfcache
+// (https://web.dev/bfcache/). The "pageshow" event triggers on such navigations.
+// Use that opportunity to update the theme.
+// We use a setTimeout with a 0 timeout here to put the change on the event queue.
+// For some reason, if we try to change the theme while the `pageshow` event is
+// running, it sometimes fails to take effect. The problem manifests on Chrome,
+// specifically when talking to a remote website with no caching.
+window.addEventListener("pageshow", ev => {
+    if (ev.persisted) {
+        setTimeout(switchToSavedTheme, 0);
+    }
+});
diff --git a/src/librustdoc/html/static/scrape-examples-help.md b/src/librustdoc/html/static/scrape-examples-help.md
new file mode 100644
index 000000000..035b2e18b
--- /dev/null
+++ b/src/librustdoc/html/static/scrape-examples-help.md
@@ -0,0 +1,34 @@
+Rustdoc will automatically scrape examples of documented items from the `examples/` directory of a project. These examples will be included within the generated documentation for that item. For example, if your library contains a public function:
+
+```rust
+// src/lib.rs
+pub fn a_func() {}
+```
+
+And you have an example calling this function:
+
+```rust
+// examples/ex.rs
+fn main() {
+  a_crate::a_func();
+}
+```
+
+Then this code snippet will be included in the documentation for `a_func`.
+
+## How to read scraped examples
+
+Scraped examples are shown as blocks of code from a given file. The relevant item will be highlighted. If the file is larger than a couple lines, only a small window will be shown which you can expand by clicking &varr; in the top-right. If a file contains multiple instances of an item, you can use the &pr; and &sc; buttons to toggle through each instance.
+
+If there is more than one file that contains examples, then you should click "More examples" to see these examples.
+
+
+## How Rustdoc scrapes examples
+
+When you run `cargo doc`, Rustdoc will analyze all the crates that match Cargo's `--examples` filter for instances of items that occur in the crates being documented. Then Rustdoc will include the source code of these instances in the generated documentation.
+
+Rustdoc has a few techniques to ensure this doesn't overwhelm documentation readers, and that it doesn't blow up the page size:
+
+1. For a given item, a maximum of 5 examples are included in the page. The remaining examples are just links to source code.
+2. Only one example is shown by default, and the remaining examples are hidden behind a toggle.
+3. For a given file that contains examples, only the item containing the examples will be included in the generated documentation.
diff --git a/src/librustdoc/html/static_files.rs b/src/librustdoc/html/static_files.rs
new file mode 100644
index 000000000..75f2b7e35
--- /dev/null
+++ b/src/librustdoc/html/static_files.rs
@@ -0,0 +1,168 @@
+//! Static files bundled with documentation output.
+//!
+//! All the static files are included here for centralized access in case anything other than the
+//! HTML rendering code (say, the theme checker) needs to access one of these files.
+//!
+//! Note about types: CSS and JavaScript files are included as `&'static str` to allow for the
+//! minifier to run on them. All other files are included as `&'static [u8]` so they can be
+//! directly written to a `Write` handle.
+
+/// The file contents of the main `rustdoc.css` file, responsible for the core layout of the page.
+pub(crate) static RUSTDOC_CSS: &str = include_str!("static/css/rustdoc.css");
+
+/// The file contents of `settings.css`, responsible for the items on the settings page.
+pub(crate) static SETTINGS_CSS: &str = include_str!("static/css/settings.css");
+
+/// The file contents of the `noscript.css` file, used in case JS isn't supported or is disabled.
+pub(crate) static NOSCRIPT_CSS: &str = include_str!("static/css/noscript.css");
+
+/// The file contents of `normalize.css`, included to even out standard elements between browser
+/// implementations.
+pub(crate) static NORMALIZE_CSS: &str = include_str!("static/css/normalize.css");
+
+/// The file contents of `main.js`, which contains the core JavaScript used on documentation pages,
+/// including search behavior and docblock folding, among others.
+pub(crate) static MAIN_JS: &str = include_str!("static/js/main.js");
+
+/// The file contents of `search.js`, which contains the search behavior.
+pub(crate) static SEARCH_JS: &str = include_str!("static/js/search.js");
+
+/// The file contents of `settings.js`, which contains the JavaScript used to handle the settings
+/// page.
+pub(crate) static SETTINGS_JS: &str = include_str!("static/js/settings.js");
+
+/// The file contents of `storage.js`, which contains functionality related to browser Local
+/// Storage, used to store documentation settings.
+pub(crate) static STORAGE_JS: &str = include_str!("static/js/storage.js");
+
+/// The file contents of `scraped-examples.js`, which contains functionality related to the
+/// --scrape-examples flag that inserts automatically-found examples of usages of items.
+pub(crate) static SCRAPE_EXAMPLES_JS: &str = include_str!("static/js/scrape-examples.js");
+
+pub(crate) static SCRAPE_EXAMPLES_HELP_MD: &str = include_str!("static/scrape-examples-help.md");
+
+/// The file contents of `wheel.svg`, the icon used for the settings button.
+pub(crate) static WHEEL_SVG: &[u8] = include_bytes!("static/images/wheel.svg");
+
+/// The file contents of `clipboard.svg`, the icon used for the "copy path" button.
+pub(crate) static CLIPBOARD_SVG: &[u8] = include_bytes!("static/images/clipboard.svg");
+
+/// The file contents of `down-arrow.svg`, the icon used for the crate choice combobox.
+pub(crate) static DOWN_ARROW_SVG: &[u8] = include_bytes!("static/images/down-arrow.svg");
+
+/// The file contents of `toggle-minus.svg`, the icon used for opened toggles.
+pub(crate) static TOGGLE_MINUS_PNG: &[u8] = include_bytes!("static/images/toggle-minus.svg");
+
+/// The file contents of `toggle-plus.svg`, the icon used for closed toggles.
+pub(crate) static TOGGLE_PLUS_PNG: &[u8] = include_bytes!("static/images/toggle-plus.svg");
+
+/// The contents of `COPYRIGHT.txt`, the license listing for files distributed with documentation
+/// output.
+pub(crate) static COPYRIGHT: &[u8] = include_bytes!("static/COPYRIGHT.txt");
+
+/// The contents of `LICENSE-APACHE.txt`, the text of the Apache License, version 2.0.
+pub(crate) static LICENSE_APACHE: &[u8] = include_bytes!("static/LICENSE-APACHE.txt");
+
+/// The contents of `LICENSE-MIT.txt`, the text of the MIT License.
+pub(crate) static LICENSE_MIT: &[u8] = include_bytes!("static/LICENSE-MIT.txt");
+
+/// The contents of `rust-logo.svg`, the default icon of the documentation.
+pub(crate) static RUST_LOGO_SVG: &[u8] = include_bytes!("static/images/rust-logo.svg");
+
+/// The default documentation favicons (SVG and PNG fallbacks)
+pub(crate) static RUST_FAVICON_SVG: &[u8] = include_bytes!("static/images/favicon.svg");
+pub(crate) static RUST_FAVICON_PNG_16: &[u8] = include_bytes!("static/images/favicon-16x16.png");
+pub(crate) static RUST_FAVICON_PNG_32: &[u8] = include_bytes!("static/images/favicon-32x32.png");
+
+/// The built-in themes given to every documentation site.
+pub(crate) mod themes {
+    /// The "light" theme, selected by default when no setting is available. Used as the basis for
+    /// the `--check-theme` functionality.
+    pub(crate) static LIGHT: &str = include_str!("static/css/themes/light.css");
+
+    /// The "dark" theme.
+    pub(crate) static DARK: &str = include_str!("static/css/themes/dark.css");
+
+    /// The "ayu" theme.
+    pub(crate) static AYU: &str = include_str!("static/css/themes/ayu.css");
+}
+
+/// Files related to the Fira Sans font.
+pub(crate) mod fira_sans {
+    /// The file `FiraSans-Regular.woff2`, the Regular variant of the Fira Sans font in woff2.
+    pub(crate) static REGULAR: &[u8] = include_bytes!("static/fonts/FiraSans-Regular.woff2");
+
+    /// The file `FiraSans-Medium.woff2`, the Medium variant of the Fira Sans font in woff2.
+    pub(crate) static MEDIUM: &[u8] = include_bytes!("static/fonts/FiraSans-Medium.woff2");
+
+    /// The file `FiraSans-LICENSE.txt`, the license text for the Fira Sans font.
+    pub(crate) static LICENSE: &[u8] = include_bytes!("static/fonts/FiraSans-LICENSE.txt");
+}
+
+/// Files related to the Source Serif 4 font.
+pub(crate) mod source_serif_4 {
+    /// The file `SourceSerif4-Regular.ttf.woff2`, the Regular variant of the Source Serif 4 font in
+    /// woff2.
+    pub(crate) static REGULAR: &[u8] =
+        include_bytes!("static/fonts/SourceSerif4-Regular.ttf.woff2");
+
+    /// The file `SourceSerif4-Bold.ttf.woff2`, the Bold variant of the Source Serif 4 font in
+    /// woff2.
+    pub(crate) static BOLD: &[u8] = include_bytes!("static/fonts/SourceSerif4-Bold.ttf.woff2");
+
+    /// The file `SourceSerif4-It.ttf.woff2`, the Italic variant of the Source Serif 4 font in
+    /// woff2.
+    pub(crate) static ITALIC: &[u8] = include_bytes!("static/fonts/SourceSerif4-It.ttf.woff2");
+
+    /// The file `SourceSerif4-LICENSE.txt`, the license text for the Source Serif 4 font.
+    pub(crate) static LICENSE: &[u8] = include_bytes!("static/fonts/SourceSerif4-LICENSE.md");
+}
+
+/// Files related to the Source Code Pro font.
+pub(crate) mod source_code_pro {
+    /// The file `SourceCodePro-Regular.ttf.woff2`, the Regular variant of the Source Code Pro font
+    /// in woff2.
+    pub(crate) static REGULAR: &[u8] =
+        include_bytes!("static/fonts/SourceCodePro-Regular.ttf.woff2");
+
+    /// The file `SourceCodePro-Semibold.ttf.woff2`, the Semibold variant of the Source Code Pro
+    /// font in woff2.
+    pub(crate) static SEMIBOLD: &[u8] =
+        include_bytes!("static/fonts/SourceCodePro-Semibold.ttf.woff2");
+
+    /// The file `SourceCodePro-It.ttf.woff2`, the Italic variant of the Source Code Pro font in
+    /// woff2.
+    pub(crate) static ITALIC: &[u8] = include_bytes!("static/fonts/SourceCodePro-It.ttf.woff2");
+
+    /// The file `SourceCodePro-LICENSE.txt`, the license text of the Source Code Pro font.
+    pub(crate) static LICENSE: &[u8] = include_bytes!("static/fonts/SourceCodePro-LICENSE.txt");
+}
+
+/// Files related to the Nanum Barun Gothic font.
+///
+/// These files are used to avoid some legacy CJK serif fonts in Windows.
+///
+/// Note that the Noto Sans KR font, which was used previously but was not very readable on Windows,
+/// has been replaced by the Nanum Barun Gothic font. This is due to Windows' implementation of font
+/// rendering that distorts OpenType fonts too much.
+///
+/// The font files were generated with these commands:
+///
+/// ```sh
+/// pyftsubset NanumBarunGothic.ttf \
+/// --unicodes=U+AC00-D7AF,U+1100-11FF,U+3130-318F,U+A960-A97F,U+D7B0-D7FF \
+/// --output-file=NanumBarunGothic.ttf.woff2 --flavor=woff2
+/// ```
+pub(crate) mod nanum_barun_gothic {
+    /// The file `NanumBarunGothic.ttf.woff2`, the Regular variant of the Nanum Barun Gothic font.
+    pub(crate) static REGULAR: &[u8] = include_bytes!("static/fonts/NanumBarunGothic.ttf.woff2");
+
+    /// The file `NanumBarunGothic-LICENSE.txt`, the license text of the Nanum Barun Gothic font.
+    pub(crate) static LICENSE: &[u8] = include_bytes!("static/fonts/NanumBarunGothic-LICENSE.txt");
+}
+
+/// Files related to the sidebar in rustdoc sources.
+pub(crate) mod sidebar {
+    /// File script to handle sidebar.
+    pub(crate) static SOURCE_SCRIPT: &str = include_str!("static/js/source-script.js");
+}
diff --git a/src/librustdoc/html/templates/STYLE.md b/src/librustdoc/html/templates/STYLE.md
new file mode 100644
index 000000000..fff65e3b5
--- /dev/null
+++ b/src/librustdoc/html/templates/STYLE.md
@@ -0,0 +1,37 @@
+# Style for Templates
+
+This directory has templates in the [Tera templating language](teradoc), which is very
+similar to [Jinja2](jinjadoc) and [Django](djangodoc) templates, and also to [Askama](askamadoc).
+
+[teradoc]: https://tera.netlify.app/docs/#templates
+[jinjadoc]: https://jinja.palletsprojects.com/en/3.0.x/templates/
+[djangodoc]: https://docs.djangoproject.com/en/3.2/topics/templates/
+[askamadoc]: https://docs.rs/askama/0.10.5/askama/
+
+We want our rendered output to have as little unnecessary whitespace as
+possible, so that pages load quickly. To achieve that we use Tera's
+[whitespace control] features. At the end of most lines, we put an empty comment
+tag with the whitespace control characters: `{#- -#}`. This causes all
+whitespace between the end of the line and the beginning of the next, including
+indentation, to be omitted on render. Sometimes we want to preserve a single
+space. In those cases we put the space at the end of the line, followed by
+`{# -#}`, which is a directive to remove following whitespace but not preceding.
+We also use the whitespace control characters in most instances of tags with
+control flow, for example `{%- if foo -%}`.
+
+[whitespace control]: https://tera.netlify.app/docs/#whitespace-control
+
+We want our templates to be readable, so we use indentation and newlines
+liberally. We indent by four spaces after opening an HTML tag _or_ a Tera
+tag. In most cases an HTML tag should be followed by a newline, but if the
+tag has simple contents and fits with its close tag on a single line, the
+contents don't necessarily need a new line.
+
+Tera templates support quite sophisticated control flow. To keep our templates
+simple and understandable, we use only a subset: `if` and `for`. In particular
+we avoid [assignments in the template logic](assignments) and [Tera
+macros](macros). This also may make things easier if we switch to a different
+Jinja-style template system, like Askama, in the future.
+
+[assignments]: https://tera.netlify.app/docs/#assignments
+[macros]: https://tera.netlify.app/docs/#macros
diff --git a/src/librustdoc/html/templates/page.html b/src/librustdoc/html/templates/page.html
new file mode 100644
index 000000000..8e25f6764
--- /dev/null
+++ b/src/librustdoc/html/templates/page.html
@@ -0,0 +1,148 @@
+<!DOCTYPE html> {#- -#}
+<html lang="en"> {#- -#}
+<head> {#- -#}
+    <meta charset="utf-8"> {#- -#}
+    <meta name="viewport" content="width=device-width, initial-scale=1.0"> {#- -#}
+    <meta name="generator" content="rustdoc"> {#- -#}
+    <meta name="description" content="{{page.description}}"> {#- -#}
+    <meta name="keywords" content="{{page.keywords}}"> {#- -#}
+    <title>{{page.title}}</title> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}SourceSerif4-Regular.ttf.woff2"> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}FiraSans-Regular.woff2"> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}FiraSans-Medium.woff2"> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}SourceCodePro-Regular.ttf.woff2"> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}SourceSerif4-Bold.ttf.woff2"> {#- -#}
+    <link rel="preload" as="font" type="font/woff2" crossorigin href="{{static_root_path|safe}}SourceCodePro-Semibold.ttf.woff2"> {#- -#}
+    <link rel="stylesheet" type="text/css" {# -#}
+          href="{{static_root_path|safe}}normalize{{page.resource_suffix}}.css"> {#- -#}
+    <link rel="stylesheet" type="text/css" {# -#}
+          href="{{static_root_path|safe}}rustdoc{{page.resource_suffix}}.css" {# -#}
+          id="mainThemeStyle"> {#- -#}
+    {%- for theme in themes -%}
+        <link rel="stylesheet" type="text/css" {# -#}
+            href="{{static_root_path|safe}}{{theme}}{{page.resource_suffix}}.css" {# -#}
+        {%- if theme == "light" -%}
+            id="themeStyle"
+        {%- else -%}
+            disabled
+        {%- endif -%}
+        >
+    {%- endfor -%}
+    <script id="default-settings" {# -#}
+      {% for (k, v) in layout.default_settings %}
+        data-{{k}}="{{v}}"
+      {%- endfor -%}
+    ></script> {#- -#}
+    <script src="{{static_root_path|safe}}storage{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- if page.css_class.contains("crate") -%}
+    <script defer src="{{page.root_path|safe}}crates{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- else if page.css_class == "source" -%}
+    <script defer src="{{static_root_path|safe}}source-script{{page.resource_suffix}}.js"></script> {#- -#}
+    <script defer src="{{page.root_path|safe}}source-files{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- else if !page.css_class.contains("mod") -%}
+    <script defer src="sidebar-items{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- endif -%}
+    <script defer src="{{static_root_path|safe}}main{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- if layout.scrape_examples_extension -%}
+    <script defer src="{{page.root_path|safe}}scrape-examples{{page.resource_suffix}}.js"></script> {#- -#}
+    {%- endif -%}
+    <noscript> {#- -#}
+        <link rel="stylesheet" {# -#}
+           href="{{static_root_path|safe}}noscript{{page.resource_suffix}}.css"> {#- -#}
+    </noscript> {#- -#}
+    {%- if layout.css_file_extension.is_some() -%}
+        <link rel="stylesheet" type="text/css" {# -#}
+            href="{{static_root_path|safe}}theme{{page.resource_suffix}}.css"> {#- -#}
+    {%- endif -%}
+    {%- if !layout.favicon.is_empty() -%}
+        <link rel="icon" href="{{layout.favicon}}"> {#- -#}
+    {%- else -%}
+        <link rel="alternate icon" type="image/png" {# -#}
+            href="{{static_root_path|safe}}favicon-16x16{{page.resource_suffix}}.png"> {#- -#}
+        <link rel="alternate icon" type="image/png" {# -#}
+            href="{{static_root_path|safe}}favicon-32x32{{page.resource_suffix}}.png"> {#- -#}
+        <link rel="icon" type="image/svg+xml" {# -#}
+            href="{{static_root_path|safe}}favicon{{page.resource_suffix}}.svg"> {#- -#}
+    {%- endif -%}
+    {{- layout.external_html.in_header|safe -}}
+</head> {#- -#}
+<body class="rustdoc {{page.css_class}}"> {#- -#}
+    <!--[if lte IE 11]> {#- -#}
+    <div class="warning"> {#- -#}
+        This old browser is unsupported and will most likely display funky things. {#- -#}
+    </div> {#- -#}
+    <![endif]--> {#- -#}
+    {{- layout.external_html.before_content|safe -}}
+    <nav class="mobile-topbar"> {#- -#}
+        <button class="sidebar-menu-toggle">&#9776;</button> {#- -#}
+        <a class="sidebar-logo" href="{{page.root_path|safe}}{{krate_with_trailing_slash|safe}}index.html"> {#- -#}
+            <div class="logo-container"> {#- -#}
+            {%- if !layout.logo.is_empty() -%}
+                <img src="{{layout.logo}}" alt="logo"> {#- -#}
+            {%- else -%}
+                <img class="rust-logo" src="{{static_root_path|safe}}rust-logo{{page.resource_suffix}}.svg" alt="logo"> {#- -#}
+            {%- endif -%}
+            </div> {#- -#}
+        </a> {#- -#}
+        <h2 class="location"></h2> {#- -#}
+    </nav> {#- -#}
+    <nav class="sidebar"> {#- -#}
+        <a class="sidebar-logo" href="{{page.root_path|safe}}{{krate_with_trailing_slash|safe}}index.html"> {#- -#}
+            <div class="logo-container"> {#- -#}
+                {%- if !layout.logo.is_empty()  %}
+                    <img src="{{layout.logo}}" alt="logo"> {#- -#}
+                {%- else -%}
+                    <img class="rust-logo" src="{{static_root_path|safe}}rust-logo{{page.resource_suffix}}.svg" alt="logo"> {#- -#}
+                {%- endif -%}
+            </div> {#- -#}
+        </a> {#- -#}
+        {{- sidebar|safe -}}
+    </nav> {#- -#}
+    <main> {#- -#}
+        <div class="width-limiter"> {#- -#}
+            <div class="sub-container"> {#- -#}
+                <a class="sub-logo-container" href="{{page.root_path|safe}}{{krate_with_trailing_slash|safe}}index.html"> {#- -#}
+                    {%- if !layout.logo.is_empty()  %}
+                        <img src="{{layout.logo}}" alt="logo"> {#- -#}
+                    {%- else -%}
+                        <img class="rust-logo" src="{{static_root_path|safe}}rust-logo{{page.resource_suffix}}.svg" alt="logo"> {#- -#}
+                    {%- endif -%}
+                </a> {#- -#}
+                <nav class="sub"> {#- -#}
+                    <form class="search-form"> {#- -#}
+                        <div class="search-container"> {#- -#}
+                            <span></span> {#- This empty span is a hacky fix for Safari - See #93184 -#}
+                            <input {# -#}
+                                class="search-input" {# -#}
+                                name="search" {# -#}
+                                autocomplete="off" {# -#}
+                                spellcheck="false" {# -#}
+                                placeholder="Click or press ‘S’ to search, ‘?’ for more options…" {# -#}
+                                type="search"> {#- -#}
+                            <div id="help-button" title="help" tabindex="-1"> {#- -#}
+                                <button type="button">?</button> {#- -#}
+                            </div> {#- -#}
+                            <div id="settings-menu" tabindex="-1"> {#- -#}
+                                <a href="{{page.root_path|safe}}settings.html" title="settings"> {#- -#}
+                                    <img width="22" height="22" alt="Change settings" {# -#}
+                                     src="{{static_root_path|safe}}wheel{{page.resource_suffix}}.svg"> {#- -#}
+                                </a> {#- -#}
+                            </div> {#- -#}
+                        </div> {#- -#}
+                    </form> {#- -#}
+                </nav> {#- -#}
+            </div> {#- -#}
+            <section id="main-content" class="content">{{- content|safe -}}</section> {#- -#}
+        </div> {#- -#}
+    </main> {#- -#}
+    {{- layout.external_html.after_content|safe -}}
+    <div id="rustdoc-vars" {# -#}
+         data-root-path="{{page.root_path|safe}}" {# -#}
+         data-current-crate="{{layout.krate}}" {# -#}
+         data-themes="{{themes|join(",") }}" {# -#}
+         data-resource-suffix="{{page.resource_suffix}}" {# -#}
+         data-rustdoc-version="{{rustdoc_version}}" {# -#}
+    > {#- -#}
+    </div> {#- -#}
+</body> {#- -#}
+</html> {#- -#}
diff --git a/src/librustdoc/html/templates/print_item.html b/src/librustdoc/html/templates/print_item.html
new file mode 100644
index 000000000..c755157d2
--- /dev/null
+++ b/src/librustdoc/html/templates/print_item.html
@@ -0,0 +1,30 @@
+<div class="main-heading"> {#- -#}
+    <h1 class="fqn"> {#- -#}
+        <span class="in-band"> {#- -#}
+            {{-typ-}}
+            {#- The breadcrumbs of the item path, like std::string -#}
+            {%- for component in path_components -%}
+            <a href="{{component.path|safe}}index.html">{{component.name}}</a>::<wbr>
+            {%- endfor -%}
+            <a class="{{item_type}}" href="#">{{name}}</a> {#- -#}
+            <button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"> {#- -#}
+                <img src="{{static_root_path|safe}}clipboard{{page.resource_suffix}}.svg" {# -#}
+                    width="19" height="18" {# -#}
+                    alt="Copy item path"> {#- -#}
+            </button> {#- -#}
+        </span> {#- -#}
+    </h1> {#- -#}
+    <span class="out-of-band"> {#- -#}
+        {% if !stability_since_raw.is_empty() %}
+        {{- stability_since_raw|safe }} · {# -#}
+        {% endif %}
+        {%- match src_href -%}
+            {%- when Some with (href) -%}
+                <a class="srclink" href="{{href|safe}}">source</a> · {# -#}
+            {%- else -%}
+        {%- endmatch -%}
+        <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs"> {#- -#}
+            [<span class="inner">&#x2212;</span>] {#- -#}
+        </a> {#- -#}
+    </span> {#- -#}
+</div> {#- -#}
diff --git a/src/librustdoc/html/tests.rs b/src/librustdoc/html/tests.rs
new file mode 100644
index 000000000..437d3995e
--- /dev/null
+++ b/src/librustdoc/html/tests.rs
@@ -0,0 +1,50 @@
+use crate::html::format::href_relative_parts;
+use rustc_span::{sym, Symbol};
+
+fn assert_relative_path(expected: &[Symbol], relative_to_fqp: &[Symbol], fqp: &[Symbol]) {
+    // No `create_default_session_globals_then` call is needed here because all
+    // the symbols used are static, and no `Symbol::intern` calls occur.
+    assert_eq!(expected, href_relative_parts(&fqp, &relative_to_fqp).collect::<Vec<_>>());
+}
+
+#[test]
+fn href_relative_parts_basic() {
+    let relative_to_fqp = &[sym::std, sym::vec];
+    let fqp = &[sym::std, sym::iter];
+    assert_relative_path(&[sym::dotdot, sym::iter], relative_to_fqp, fqp);
+}
+
+#[test]
+fn href_relative_parts_parent_module() {
+    let relative_to_fqp = &[sym::std, sym::vec];
+    let fqp = &[sym::std];
+    assert_relative_path(&[sym::dotdot], relative_to_fqp, fqp);
+}
+
+#[test]
+fn href_relative_parts_different_crate() {
+    let relative_to_fqp = &[sym::std, sym::vec];
+    let fqp = &[sym::core, sym::iter];
+    assert_relative_path(&[sym::dotdot, sym::dotdot, sym::core, sym::iter], relative_to_fqp, fqp);
+}
+
+#[test]
+fn href_relative_parts_same_module() {
+    let relative_to_fqp = &[sym::std, sym::vec];
+    let fqp = &[sym::std, sym::vec];
+    assert_relative_path(&[], relative_to_fqp, fqp);
+}
+
+#[test]
+fn href_relative_parts_child_module() {
+    let relative_to_fqp = &[sym::std];
+    let fqp = &[sym::std, sym::vec];
+    assert_relative_path(&[sym::vec], relative_to_fqp, fqp);
+}
+
+#[test]
+fn href_relative_parts_root() {
+    let relative_to_fqp = &[];
+    let fqp = &[sym::std];
+    assert_relative_path(&[sym::std], relative_to_fqp, fqp);
+}
diff --git a/src/librustdoc/html/toc.rs b/src/librustdoc/html/toc.rs
new file mode 100644
index 000000000..a12c2a6a1
--- /dev/null
+++ b/src/librustdoc/html/toc.rs
@@ -0,0 +1,191 @@
+//! Table-of-contents creation.
+
+/// A (recursive) table of contents
+#[derive(Debug, PartialEq)]
+pub(crate) struct Toc {
+    /// The levels are strictly decreasing, i.e.
+    ///
+    /// `entries[0].level >= entries[1].level >= ...`
+    ///
+    /// Normally they are equal, but can differ in cases like A and B,
+    /// both of which end up in the same `Toc` as they have the same
+    /// parent (Main).
+    ///
+    /// ```text
+    /// # Main
+    /// ### A
+    /// ## B
+    /// ```
+    entries: Vec<TocEntry>,
+}
+
+impl Toc {
+    fn count_entries_with_level(&self, level: u32) -> usize {
+        self.entries.iter().filter(|e| e.level == level).count()
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub(crate) struct TocEntry {
+    level: u32,
+    sec_number: String,
+    name: String,
+    id: String,
+    children: Toc,
+}
+
+/// Progressive construction of a table of contents.
+#[derive(PartialEq)]
+pub(crate) struct TocBuilder {
+    top_level: Toc,
+    /// The current hierarchy of parent headings, the levels are
+    /// strictly increasing (i.e., `chain[0].level < chain[1].level <
+    /// ...`) with each entry being the most recent occurrence of a
+    /// heading with that level (it doesn't include the most recent
+    /// occurrences of every level, just, if it *is* in `chain` then
+    /// it is the most recent one).
+    ///
+    /// We also have `chain[0].level <= top_level.entries[last]`.
+    chain: Vec<TocEntry>,
+}
+
+impl TocBuilder {
+    pub(crate) fn new() -> TocBuilder {
+        TocBuilder { top_level: Toc { entries: Vec::new() }, chain: Vec::new() }
+    }
+
+    /// Converts into a true `Toc` struct.
+    pub(crate) fn into_toc(mut self) -> Toc {
+        // we know all levels are >= 1.
+        self.fold_until(0);
+        self.top_level
+    }
+
+    /// Collapse the chain until the first heading more important than
+    /// `level` (i.e., lower level)
+    ///
+    /// Example:
+    ///
+    /// ```text
+    /// ## A
+    /// # B
+    /// # C
+    /// ## D
+    /// ## E
+    /// ### F
+    /// #### G
+    /// ### H
+    /// ```
+    ///
+    /// If we are considering H (i.e., level 3), then A and B are in
+    /// self.top_level, D is in C.children, and C, E, F, G are in
+    /// self.chain.
+    ///
+    /// When we attempt to push H, we realize that first G is not the
+    /// parent (level is too high) so it is popped from chain and put
+    /// into F.children, then F isn't the parent (level is equal, aka
+    /// sibling), so it's also popped and put into E.children.
+    ///
+    /// This leaves us looking at E, which does have a smaller level,
+    /// and, by construction, it's the most recent thing with smaller
+    /// level, i.e., it's the immediate parent of H.
+    fn fold_until(&mut self, level: u32) {
+        let mut this = None;
+        loop {
+            match self.chain.pop() {
+                Some(mut next) => {
+                    next.children.entries.extend(this);
+                    if next.level < level {
+                        // this is the parent we want, so return it to
+                        // its rightful place.
+                        self.chain.push(next);
+                        return;
+                    } else {
+                        this = Some(next);
+                    }
+                }
+                None => {
+                    self.top_level.entries.extend(this);
+                    return;
+                }
+            }
+        }
+    }
+
+    /// Push a level `level` heading into the appropriate place in the
+    /// hierarchy, returning a string containing the section number in
+    /// `<num>.<num>.<num>` format.
+    pub(crate) fn push(&mut self, level: u32, name: String, id: String) -> &str {
+        assert!(level >= 1);
+
+        // collapse all previous sections into their parents until we
+        // get to relevant heading (i.e., the first one with a smaller
+        // level than us)
+        self.fold_until(level);
+
+        let mut sec_number;
+        {
+            let (toc_level, toc) = match self.chain.last() {
+                None => {
+                    sec_number = String::new();
+                    (0, &self.top_level)
+                }
+                Some(entry) => {
+                    sec_number = entry.sec_number.clone();
+                    sec_number.push('.');
+                    (entry.level, &entry.children)
+                }
+            };
+            // fill in any missing zeros, e.g., for
+            // # Foo (1)
+            // ### Bar (1.0.1)
+            for _ in toc_level..level - 1 {
+                sec_number.push_str("0.");
+            }
+            let number = toc.count_entries_with_level(level);
+            sec_number.push_str(&(number + 1).to_string())
+        }
+
+        self.chain.push(TocEntry {
+            level,
+            name,
+            sec_number,
+            id,
+            children: Toc { entries: Vec::new() },
+        });
+
+        // get the thing we just pushed, so we can borrow the string
+        // out of it with the right lifetime
+        let just_inserted = self.chain.last_mut().unwrap();
+        &just_inserted.sec_number
+    }
+}
+
+impl Toc {
+    fn print_inner(&self, v: &mut String) {
+        use std::fmt::Write as _;
+
+        v.push_str("<ul>");
+        for entry in &self.entries {
+            // recursively format this table of contents
+            let _ = write!(
+                v,
+                "\n<li><a href=\"#{id}\">{num} {name}</a>",
+                id = entry.id,
+                num = entry.sec_number,
+                name = entry.name
+            );
+            entry.children.print_inner(&mut *v);
+            v.push_str("</li>");
+        }
+        v.push_str("</ul>");
+    }
+    pub(crate) fn print(&self) -> String {
+        let mut v = String::new();
+        self.print_inner(&mut v);
+        v
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/html/toc/tests.rs b/src/librustdoc/html/toc/tests.rs
new file mode 100644
index 000000000..014f34686
--- /dev/null
+++ b/src/librustdoc/html/toc/tests.rs
@@ -0,0 +1,79 @@
+use super::{Toc, TocBuilder, TocEntry};
+
+#[test]
+fn builder_smoke() {
+    let mut builder = TocBuilder::new();
+
+    // this is purposely not using a fancy macro like below so
+    // that we're sure that this is doing the correct thing, and
+    // there's been no macro mistake.
+    macro_rules! push {
+        ($level: expr, $name: expr) => {
+            assert_eq!(builder.push($level, $name.to_string(), "".to_string()), $name);
+        };
+    }
+    push!(2, "0.1");
+    push!(1, "1");
+    {
+        push!(2, "1.1");
+        {
+            push!(3, "1.1.1");
+            push!(3, "1.1.2");
+        }
+        push!(2, "1.2");
+        {
+            push!(3, "1.2.1");
+            push!(3, "1.2.2");
+        }
+    }
+    push!(1, "2");
+    push!(1, "3");
+    {
+        push!(4, "3.0.0.1");
+        {
+            push!(6, "3.0.0.1.0.1");
+        }
+        push!(4, "3.0.0.2");
+        push!(2, "3.1");
+        {
+            push!(4, "3.1.0.1");
+        }
+    }
+
+    macro_rules! toc {
+        ($(($level: expr, $name: expr, $(($sub: tt))* )),*) => {
+            Toc {
+                entries: vec![
+                    $(
+                        TocEntry {
+                            level: $level,
+                            name: $name.to_string(),
+                            sec_number: $name.to_string(),
+                            id: "".to_string(),
+                            children: toc!($($sub),*)
+                        }
+                        ),*
+                    ]
+            }
+        }
+    }
+    let expected = toc!(
+        (2, "0.1",),
+        (
+            1,
+            "1",
+            ((2, "1.1", ((3, "1.1.1",))((3, "1.1.2",))))((
+                2,
+                "1.2",
+                ((3, "1.2.1",))((3, "1.2.2",))
+            ))
+        ),
+        (1, "2",),
+        (
+            1,
+            "3",
+            ((4, "3.0.0.1", ((6, "3.0.0.1.0.1",))))((4, "3.0.0.2",))((2, "3.1", ((4, "3.1.0.1",))))
+        )
+    );
+    assert_eq!(expected, builder.into_toc());
+}
diff --git a/src/librustdoc/html/url_parts_builder.rs b/src/librustdoc/html/url_parts_builder.rs
new file mode 100644
index 000000000..1e6af6af6
--- /dev/null
+++ b/src/librustdoc/html/url_parts_builder.rs
@@ -0,0 +1,180 @@
+use std::fmt::{self, Write};
+
+use rustc_span::Symbol;
+
+/// A builder that allows efficiently and easily constructing the part of a URL
+/// after the domain: `nightly/core/str/struct.Bytes.html`.
+///
+/// This type is a wrapper around the final `String` buffer,
+/// but its API is like that of a `Vec` of URL components.
+#[derive(Debug)]
+pub(crate) struct UrlPartsBuilder {
+    buf: String,
+}
+
+impl UrlPartsBuilder {
+    /// Create an empty buffer.
+    #[allow(dead_code)]
+    pub(crate) fn new() -> Self {
+        Self { buf: String::new() }
+    }
+
+    /// Create an empty buffer with capacity for the specified number of bytes.
+    fn with_capacity_bytes(count: usize) -> Self {
+        Self { buf: String::with_capacity(count) }
+    }
+
+    /// Create a buffer with one URL component.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```ignore (private-type)
+    /// let builder = UrlPartsBuilder::singleton("core");
+    /// assert_eq!(builder.finish(), "core");
+    /// ```
+    ///
+    /// Adding more components afterward.
+    ///
+    /// ```ignore (private-type)
+    /// let mut builder = UrlPartsBuilder::singleton("core");
+    /// builder.push("str");
+    /// builder.push_front("nightly");
+    /// assert_eq!(builder.finish(), "nightly/core/str");
+    /// ```
+    pub(crate) fn singleton(part: &str) -> Self {
+        Self { buf: part.to_owned() }
+    }
+
+    /// Push a component onto the buffer.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```ignore (private-type)
+    /// let mut builder = UrlPartsBuilder::new();
+    /// builder.push("core");
+    /// builder.push("str");
+    /// builder.push("struct.Bytes.html");
+    /// assert_eq!(builder.finish(), "core/str/struct.Bytes.html");
+    /// ```
+    pub(crate) fn push(&mut self, part: &str) {
+        if !self.buf.is_empty() {
+            self.buf.push('/');
+        }
+        self.buf.push_str(part);
+    }
+
+    /// Push a component onto the buffer, using [`format!`]'s formatting syntax.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage (equivalent to the example for [`UrlPartsBuilder::push`]):
+    ///
+    /// ```ignore (private-type)
+    /// let mut builder = UrlPartsBuilder::new();
+    /// builder.push("core");
+    /// builder.push("str");
+    /// builder.push_fmt(format_args!("{}.{}.html", "struct", "Bytes"));
+    /// assert_eq!(builder.finish(), "core/str/struct.Bytes.html");
+    /// ```
+    pub(crate) fn push_fmt(&mut self, args: fmt::Arguments<'_>) {
+        if !self.buf.is_empty() {
+            self.buf.push('/');
+        }
+        self.buf.write_fmt(args).unwrap()
+    }
+
+    /// Push a component onto the front of the buffer.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```ignore (private-type)
+    /// let mut builder = UrlPartsBuilder::new();
+    /// builder.push("core");
+    /// builder.push("str");
+    /// builder.push_front("nightly");
+    /// builder.push("struct.Bytes.html");
+    /// assert_eq!(builder.finish(), "nightly/core/str/struct.Bytes.html");
+    /// ```
+    pub(crate) fn push_front(&mut self, part: &str) {
+        let is_empty = self.buf.is_empty();
+        self.buf.reserve(part.len() + if !is_empty { 1 } else { 0 });
+        self.buf.insert_str(0, part);
+        if !is_empty {
+            self.buf.insert(part.len(), '/');
+        }
+    }
+
+    /// Get the final `String` buffer.
+    pub(crate) fn finish(self) -> String {
+        self.buf
+    }
+}
+
+/// This is just a guess at the average length of a URL part,
+/// used for [`String::with_capacity`] calls in the [`FromIterator`]
+/// and [`Extend`] impls, and for [estimating item path lengths].
+///
+/// The value `8` was chosen for two main reasons:
+///
+/// * It seems like a good guess for the average part length.
+/// * jemalloc's size classes are all multiples of eight,
+///   which means that the amount of memory it allocates will often match
+///   the amount requested, avoiding wasted bytes.
+///
+/// [estimating item path lengths]: estimate_item_path_byte_length
+const AVG_PART_LENGTH: usize = 8;
+
+/// Estimate the number of bytes in an item's path, based on how many segments it has.
+///
+/// **Note:** This is only to be used with, e.g., [`String::with_capacity()`];
+/// the return value is just a rough estimate.
+pub(crate) const fn estimate_item_path_byte_length(segment_count: usize) -> usize {
+    AVG_PART_LENGTH * segment_count
+}
+
+impl<'a> FromIterator<&'a str> for UrlPartsBuilder {
+    fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
+        let iter = iter.into_iter();
+        let mut builder = Self::with_capacity_bytes(AVG_PART_LENGTH * iter.size_hint().0);
+        iter.for_each(|part| builder.push(part));
+        builder
+    }
+}
+
+impl<'a> Extend<&'a str> for UrlPartsBuilder {
+    fn extend<T: IntoIterator<Item = &'a str>>(&mut self, iter: T) {
+        let iter = iter.into_iter();
+        self.buf.reserve(AVG_PART_LENGTH * iter.size_hint().0);
+        iter.for_each(|part| self.push(part));
+    }
+}
+
+impl FromIterator<Symbol> for UrlPartsBuilder {
+    fn from_iter<T: IntoIterator<Item = Symbol>>(iter: T) -> Self {
+        // This code has to be duplicated from the `&str` impl because of
+        // `Symbol::as_str`'s lifetimes.
+        let iter = iter.into_iter();
+        let mut builder = Self::with_capacity_bytes(AVG_PART_LENGTH * iter.size_hint().0);
+        iter.for_each(|part| builder.push(part.as_str()));
+        builder
+    }
+}
+
+impl Extend<Symbol> for UrlPartsBuilder {
+    fn extend<T: IntoIterator<Item = Symbol>>(&mut self, iter: T) {
+        // This code has to be duplicated from the `&str` impl because of
+        // `Symbol::as_str`'s lifetimes.
+        let iter = iter.into_iter();
+        self.buf.reserve(AVG_PART_LENGTH * iter.size_hint().0);
+        iter.for_each(|part| self.push(part.as_str()));
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/src/librustdoc/html/url_parts_builder/tests.rs b/src/librustdoc/html/url_parts_builder/tests.rs
new file mode 100644
index 000000000..636e1ab55
--- /dev/null
+++ b/src/librustdoc/html/url_parts_builder/tests.rs
@@ -0,0 +1,64 @@
+use super::*;
+
+fn t(builder: UrlPartsBuilder, expect: &str) {
+    assert_eq!(builder.finish(), expect);
+}
+
+#[test]
+fn empty() {
+    t(UrlPartsBuilder::new(), "");
+}
+
+#[test]
+fn singleton() {
+    t(UrlPartsBuilder::singleton("index.html"), "index.html");
+}
+
+#[test]
+fn push_several() {
+    let mut builder = UrlPartsBuilder::new();
+    builder.push("core");
+    builder.push("str");
+    builder.push("struct.Bytes.html");
+    t(builder, "core/str/struct.Bytes.html");
+}
+
+#[test]
+fn push_front_empty() {
+    let mut builder = UrlPartsBuilder::new();
+    builder.push_front("page.html");
+    t(builder, "page.html");
+}
+
+#[test]
+fn push_front_non_empty() {
+    let mut builder = UrlPartsBuilder::new();
+    builder.push("core");
+    builder.push("str");
+    builder.push("struct.Bytes.html");
+    builder.push_front("nightly");
+    t(builder, "nightly/core/str/struct.Bytes.html");
+}
+
+#[test]
+fn push_fmt() {
+    let mut builder = UrlPartsBuilder::new();
+    builder.push_fmt(format_args!("{}", "core"));
+    builder.push("str");
+    builder.push_front("nightly");
+    builder.push_fmt(format_args!("{}.{}.html", "struct", "Bytes"));
+    t(builder, "nightly/core/str/struct.Bytes.html");
+}
+
+#[test]
+fn collect() {
+    t(["core", "str"].into_iter().collect(), "core/str");
+    t(["core", "str", "struct.Bytes.html"].into_iter().collect(), "core/str/struct.Bytes.html");
+}
+
+#[test]
+fn extend() {
+    let mut builder = UrlPartsBuilder::singleton("core");
+    builder.extend(["str", "struct.Bytes.html"]);
+    t(builder, "core/str/struct.Bytes.html");
+}
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
new file mode 100644
index 000000000..716a4c9ea
--- /dev/null
+++ b/src/librustdoc/json/conversions.rs
@@ -0,0 +1,798 @@
+//! These from impls are used to create the JSON types which get serialized. They're very close to
+//! the `clean` types but with some fields removed or stringified to simplify the output and not
+//! expose unstable compiler internals.
+
+#![allow(rustc::default_hash_types)]
+
+use std::convert::From;
+use std::fmt;
+
+use rustc_ast::ast;
+use rustc_hir::{def::CtorKind, def_id::DefId};
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_span::{Pos, Symbol};
+use rustc_target::spec::abi::Abi as RustcAbi;
+
+use rustdoc_json_types::*;
+
+use crate::clean::utils::print_const_expr;
+use crate::clean::{self, ItemId};
+use crate::formats::item_type::ItemType;
+use crate::json::JsonRenderer;
+
+impl JsonRenderer<'_> {
+    pub(super) fn convert_item(&self, item: clean::Item) -> Option<Item> {
+        let deprecation = item.deprecation(self.tcx);
+        let links = self
+            .cache
+            .intra_doc_links
+            .get(&item.item_id)
+            .into_iter()
+            .flatten()
+            .map(|clean::ItemLink { link, did, .. }| {
+                (link.clone(), from_item_id((*did).into(), self.tcx))
+            })
+            .collect();
+        let docs = item.attrs.collapsed_doc_value();
+        let attrs = item
+            .attrs
+            .other_attrs
+            .iter()
+            .map(rustc_ast_pretty::pprust::attribute_to_string)
+            .collect();
+        let span = item.span(self.tcx);
+        let clean::Item { name, attrs: _, kind: _, visibility, item_id, cfg: _ } = item;
+        let inner = match *item.kind {
+            clean::KeywordItem => return None,
+            clean::StrippedItem(ref inner) => {
+                match &**inner {
+                    // We document non-empty stripped modules as with `Module::is_stripped` set to
+                    // `true`, to prevent contained items from being orphaned for downstream users,
+                    // as JSON does no inlining.
+                    clean::ModuleItem(m) if !m.items.is_empty() => from_clean_item(item, self.tcx),
+                    _ => return None,
+                }
+            }
+            _ => from_clean_item(item, self.tcx),
+        };
+        Some(Item {
+            id: from_item_id_with_name(item_id, self.tcx, name),
+            crate_id: item_id.krate().as_u32(),
+            name: name.map(|sym| sym.to_string()),
+            span: self.convert_span(span),
+            visibility: self.convert_visibility(visibility),
+            docs,
+            attrs,
+            deprecation: deprecation.map(from_deprecation),
+            inner,
+            links,
+        })
+    }
+
+    fn convert_span(&self, span: clean::Span) -> Option<Span> {
+        match span.filename(self.sess()) {
+            rustc_span::FileName::Real(name) => {
+                if let Some(local_path) = name.into_local_path() {
+                    let hi = span.hi(self.sess());
+                    let lo = span.lo(self.sess());
+                    Some(Span {
+                        filename: local_path,
+                        begin: (lo.line, lo.col.to_usize()),
+                        end: (hi.line, hi.col.to_usize()),
+                    })
+                } else {
+                    None
+                }
+            }
+            _ => None,
+        }
+    }
+
+    fn convert_visibility(&self, v: clean::Visibility) -> Visibility {
+        use clean::Visibility::*;
+        match v {
+            Public => Visibility::Public,
+            Inherited => Visibility::Default,
+            Restricted(did) if did.is_crate_root() => Visibility::Crate,
+            Restricted(did) => Visibility::Restricted {
+                parent: from_item_id(did.into(), self.tcx),
+                path: self.tcx.def_path(did).to_string_no_crate_verbose(),
+            },
+        }
+    }
+}
+
+pub(crate) trait FromWithTcx<T> {
+    fn from_tcx(f: T, tcx: TyCtxt<'_>) -> Self;
+}
+
+pub(crate) trait IntoWithTcx<T> {
+    fn into_tcx(self, tcx: TyCtxt<'_>) -> T;
+}
+
+impl<T, U> IntoWithTcx<U> for T
+where
+    U: FromWithTcx<T>,
+{
+    fn into_tcx(self, tcx: TyCtxt<'_>) -> U {
+        U::from_tcx(self, tcx)
+    }
+}
+
+pub(crate) fn from_deprecation(deprecation: rustc_attr::Deprecation) -> Deprecation {
+    #[rustfmt::skip]
+    let rustc_attr::Deprecation { since, note, is_since_rustc_version: _, suggestion: _ } = deprecation;
+    Deprecation { since: since.map(|s| s.to_string()), note: note.map(|s| s.to_string()) }
+}
+
+impl FromWithTcx<clean::GenericArgs> for GenericArgs {
+    fn from_tcx(args: clean::GenericArgs, tcx: TyCtxt<'_>) -> Self {
+        use clean::GenericArgs::*;
+        match args {
+            AngleBracketed { args, bindings } => GenericArgs::AngleBracketed {
+                args: args.into_vec().into_iter().map(|a| a.into_tcx(tcx)).collect(),
+                bindings: bindings.into_iter().map(|a| a.into_tcx(tcx)).collect(),
+            },
+            Parenthesized { inputs, output } => GenericArgs::Parenthesized {
+                inputs: inputs.into_vec().into_iter().map(|a| a.into_tcx(tcx)).collect(),
+                output: output.map(|a| (*a).into_tcx(tcx)),
+            },
+        }
+    }
+}
+
+impl FromWithTcx<clean::GenericArg> for GenericArg {
+    fn from_tcx(arg: clean::GenericArg, tcx: TyCtxt<'_>) -> Self {
+        use clean::GenericArg::*;
+        match arg {
+            Lifetime(l) => GenericArg::Lifetime(l.0.to_string()),
+            Type(t) => GenericArg::Type(t.into_tcx(tcx)),
+            Const(box c) => GenericArg::Const(c.into_tcx(tcx)),
+            Infer => GenericArg::Infer,
+        }
+    }
+}
+
+impl FromWithTcx<clean::Constant> for Constant {
+    fn from_tcx(constant: clean::Constant, tcx: TyCtxt<'_>) -> Self {
+        let expr = constant.expr(tcx);
+        let value = constant.value(tcx);
+        let is_literal = constant.is_literal(tcx);
+        Constant { type_: constant.type_.into_tcx(tcx), expr, value, is_literal }
+    }
+}
+
+impl FromWithTcx<clean::TypeBinding> for TypeBinding {
+    fn from_tcx(binding: clean::TypeBinding, tcx: TyCtxt<'_>) -> Self {
+        TypeBinding {
+            name: binding.assoc.name.to_string(),
+            args: binding.assoc.args.into_tcx(tcx),
+            binding: binding.kind.into_tcx(tcx),
+        }
+    }
+}
+
+impl FromWithTcx<clean::TypeBindingKind> for TypeBindingKind {
+    fn from_tcx(kind: clean::TypeBindingKind, tcx: TyCtxt<'_>) -> Self {
+        use clean::TypeBindingKind::*;
+        match kind {
+            Equality { term } => TypeBindingKind::Equality(term.into_tcx(tcx)),
+            Constraint { bounds } => {
+                TypeBindingKind::Constraint(bounds.into_iter().map(|a| a.into_tcx(tcx)).collect())
+            }
+        }
+    }
+}
+
+/// It generates an ID as follows:
+///
+/// `CRATE_ID:ITEM_ID[:NAME_ID]` (if there is no name, NAME_ID is not generated).
+pub(crate) fn from_item_id(item_id: ItemId, tcx: TyCtxt<'_>) -> Id {
+    from_item_id_with_name(item_id, tcx, None)
+}
+
+// FIXME: this function (and appending the name at the end of the ID) should be removed when
+// reexports are not inlined anymore for json format. It should be done in #93518.
+pub(crate) fn from_item_id_with_name(item_id: ItemId, tcx: TyCtxt<'_>, name: Option<Symbol>) -> Id {
+    struct DisplayDefId<'a>(DefId, TyCtxt<'a>, Option<Symbol>);
+
+    impl<'a> fmt::Display for DisplayDefId<'a> {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            let name = match self.2 {
+                Some(name) => format!(":{}", name.as_u32()),
+                None => self
+                    .1
+                    .opt_item_name(self.0)
+                    .map(|n| format!(":{}", n.as_u32()))
+                    .unwrap_or_default(),
+            };
+            write!(f, "{}:{}{}", self.0.krate.as_u32(), u32::from(self.0.index), name)
+        }
+    }
+
+    match item_id {
+        ItemId::DefId(did) => Id(format!("{}", DisplayDefId(did, tcx, name))),
+        ItemId::Blanket { for_, impl_id } => {
+            Id(format!("b:{}-{}", DisplayDefId(impl_id, tcx, None), DisplayDefId(for_, tcx, name)))
+        }
+        ItemId::Auto { for_, trait_ } => {
+            Id(format!("a:{}-{}", DisplayDefId(trait_, tcx, None), DisplayDefId(for_, tcx, name)))
+        }
+        ItemId::Primitive(ty, krate) => Id(format!("p:{}:{}", krate.as_u32(), ty.as_sym())),
+    }
+}
+
+fn from_clean_item(item: clean::Item, tcx: TyCtxt<'_>) -> ItemEnum {
+    use clean::ItemKind::*;
+    let name = item.name;
+    let is_crate = item.is_crate();
+    let header = item.fn_header(tcx);
+
+    match *item.kind {
+        ModuleItem(m) => {
+            ItemEnum::Module(Module { is_crate, items: ids(m.items, tcx), is_stripped: false })
+        }
+        ImportItem(i) => ItemEnum::Import(i.into_tcx(tcx)),
+        StructItem(s) => ItemEnum::Struct(s.into_tcx(tcx)),
+        UnionItem(u) => ItemEnum::Union(u.into_tcx(tcx)),
+        StructFieldItem(f) => ItemEnum::StructField(f.into_tcx(tcx)),
+        EnumItem(e) => ItemEnum::Enum(e.into_tcx(tcx)),
+        VariantItem(v) => ItemEnum::Variant(v.into_tcx(tcx)),
+        FunctionItem(f) => ItemEnum::Function(from_function(f, header.unwrap(), tcx)),
+        ForeignFunctionItem(f) => ItemEnum::Function(from_function(f, header.unwrap(), tcx)),
+        TraitItem(t) => ItemEnum::Trait(t.into_tcx(tcx)),
+        TraitAliasItem(t) => ItemEnum::TraitAlias(t.into_tcx(tcx)),
+        MethodItem(m, _) => ItemEnum::Method(from_function_method(m, true, header.unwrap(), tcx)),
+        TyMethodItem(m) => ItemEnum::Method(from_function_method(m, false, header.unwrap(), tcx)),
+        ImplItem(i) => ItemEnum::Impl(i.into_tcx(tcx)),
+        StaticItem(s) => ItemEnum::Static(s.into_tcx(tcx)),
+        ForeignStaticItem(s) => ItemEnum::Static(s.into_tcx(tcx)),
+        ForeignTypeItem => ItemEnum::ForeignType,
+        TypedefItem(t) => ItemEnum::Typedef(t.into_tcx(tcx)),
+        OpaqueTyItem(t) => ItemEnum::OpaqueTy(t.into_tcx(tcx)),
+        ConstantItem(c) => ItemEnum::Constant(c.into_tcx(tcx)),
+        MacroItem(m) => ItemEnum::Macro(m.source),
+        ProcMacroItem(m) => ItemEnum::ProcMacro(m.into_tcx(tcx)),
+        PrimitiveItem(p) => ItemEnum::PrimitiveType(p.as_sym().to_string()),
+        TyAssocConstItem(ty) => ItemEnum::AssocConst { type_: ty.into_tcx(tcx), default: None },
+        AssocConstItem(ty, default) => {
+            ItemEnum::AssocConst { type_: ty.into_tcx(tcx), default: Some(default.expr(tcx)) }
+        }
+        TyAssocTypeItem(g, b) => ItemEnum::AssocType {
+            generics: (*g).into_tcx(tcx),
+            bounds: b.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            default: None,
+        },
+        AssocTypeItem(t, b) => ItemEnum::AssocType {
+            generics: t.generics.into_tcx(tcx),
+            bounds: b.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            default: Some(t.item_type.unwrap_or(t.type_).into_tcx(tcx)),
+        },
+        // `convert_item` early returns `None` for stripped items and keywords.
+        KeywordItem => unreachable!(),
+        StrippedItem(inner) => {
+            match *inner {
+                ModuleItem(m) => ItemEnum::Module(Module {
+                    is_crate,
+                    items: ids(m.items, tcx),
+                    is_stripped: true,
+                }),
+                // `convert_item` early returns `None` for stripped items we're not including
+                _ => unreachable!(),
+            }
+        }
+        ExternCrateItem { ref src } => ItemEnum::ExternCrate {
+            name: name.as_ref().unwrap().to_string(),
+            rename: src.map(|x| x.to_string()),
+        },
+    }
+}
+
+impl FromWithTcx<clean::Struct> for Struct {
+    fn from_tcx(struct_: clean::Struct, tcx: TyCtxt<'_>) -> Self {
+        let fields_stripped = struct_.has_stripped_entries();
+        let clean::Struct { struct_type, generics, fields } = struct_;
+        Struct {
+            struct_type: from_ctor_kind(struct_type),
+            generics: generics.into_tcx(tcx),
+            fields_stripped,
+            fields: ids(fields, tcx),
+            impls: Vec::new(), // Added in JsonRenderer::item
+        }
+    }
+}
+
+impl FromWithTcx<clean::Union> for Union {
+    fn from_tcx(union_: clean::Union, tcx: TyCtxt<'_>) -> Self {
+        let fields_stripped = union_.has_stripped_entries();
+        let clean::Union { generics, fields } = union_;
+        Union {
+            generics: generics.into_tcx(tcx),
+            fields_stripped,
+            fields: ids(fields, tcx),
+            impls: Vec::new(), // Added in JsonRenderer::item
+        }
+    }
+}
+
+pub(crate) fn from_ctor_kind(struct_type: CtorKind) -> StructType {
+    match struct_type {
+        CtorKind::Fictive => StructType::Plain,
+        CtorKind::Fn => StructType::Tuple,
+        CtorKind::Const => StructType::Unit,
+    }
+}
+
+pub(crate) fn from_fn_header(header: &rustc_hir::FnHeader) -> Header {
+    Header {
+        async_: header.is_async(),
+        const_: header.is_const(),
+        unsafe_: header.is_unsafe(),
+        abi: convert_abi(header.abi),
+    }
+}
+
+fn convert_abi(a: RustcAbi) -> Abi {
+    match a {
+        RustcAbi::Rust => Abi::Rust,
+        RustcAbi::C { unwind } => Abi::C { unwind },
+        RustcAbi::Cdecl { unwind } => Abi::Cdecl { unwind },
+        RustcAbi::Stdcall { unwind } => Abi::Stdcall { unwind },
+        RustcAbi::Fastcall { unwind } => Abi::Fastcall { unwind },
+        RustcAbi::Aapcs { unwind } => Abi::Aapcs { unwind },
+        RustcAbi::Win64 { unwind } => Abi::Win64 { unwind },
+        RustcAbi::SysV64 { unwind } => Abi::SysV64 { unwind },
+        RustcAbi::System { unwind } => Abi::System { unwind },
+        _ => Abi::Other(a.to_string()),
+    }
+}
+
+impl FromWithTcx<clean::Generics> for Generics {
+    fn from_tcx(generics: clean::Generics, tcx: TyCtxt<'_>) -> Self {
+        Generics {
+            params: generics.params.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            where_predicates: generics
+                .where_predicates
+                .into_iter()
+                .map(|x| x.into_tcx(tcx))
+                .collect(),
+        }
+    }
+}
+
+impl FromWithTcx<clean::GenericParamDef> for GenericParamDef {
+    fn from_tcx(generic_param: clean::GenericParamDef, tcx: TyCtxt<'_>) -> Self {
+        GenericParamDef {
+            name: generic_param.name.to_string(),
+            kind: generic_param.kind.into_tcx(tcx),
+        }
+    }
+}
+
+impl FromWithTcx<clean::GenericParamDefKind> for GenericParamDefKind {
+    fn from_tcx(kind: clean::GenericParamDefKind, tcx: TyCtxt<'_>) -> Self {
+        use clean::GenericParamDefKind::*;
+        match kind {
+            Lifetime { outlives } => GenericParamDefKind::Lifetime {
+                outlives: outlives.into_iter().map(|lt| lt.0.to_string()).collect(),
+            },
+            Type { did: _, bounds, default, synthetic } => GenericParamDefKind::Type {
+                bounds: bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+                default: default.map(|x| (*x).into_tcx(tcx)),
+                synthetic,
+            },
+            Const { did: _, ty, default } => GenericParamDefKind::Const {
+                type_: (*ty).into_tcx(tcx),
+                default: default.map(|x| *x),
+            },
+        }
+    }
+}
+
+impl FromWithTcx<clean::WherePredicate> for WherePredicate {
+    fn from_tcx(predicate: clean::WherePredicate, tcx: TyCtxt<'_>) -> Self {
+        use clean::WherePredicate::*;
+        match predicate {
+            BoundPredicate { ty, bounds, bound_params } => WherePredicate::BoundPredicate {
+                type_: ty.into_tcx(tcx),
+                bounds: bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+                generic_params: bound_params
+                    .into_iter()
+                    .map(|x| GenericParamDef {
+                        name: x.0.to_string(),
+                        kind: GenericParamDefKind::Lifetime { outlives: vec![] },
+                    })
+                    .collect(),
+            },
+            RegionPredicate { lifetime, bounds } => WherePredicate::RegionPredicate {
+                lifetime: lifetime.0.to_string(),
+                bounds: bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            },
+            EqPredicate { lhs, rhs } => {
+                WherePredicate::EqPredicate { lhs: lhs.into_tcx(tcx), rhs: rhs.into_tcx(tcx) }
+            }
+        }
+    }
+}
+
+impl FromWithTcx<clean::GenericBound> for GenericBound {
+    fn from_tcx(bound: clean::GenericBound, tcx: TyCtxt<'_>) -> Self {
+        use clean::GenericBound::*;
+        match bound {
+            TraitBound(clean::PolyTrait { trait_, generic_params }, modifier) => {
+                // FIXME: should `trait_` be a clean::Path equivalent in JSON?
+                let trait_ = clean::Type::Path { path: trait_ }.into_tcx(tcx);
+                GenericBound::TraitBound {
+                    trait_,
+                    generic_params: generic_params.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+                    modifier: from_trait_bound_modifier(modifier),
+                }
+            }
+            Outlives(lifetime) => GenericBound::Outlives(lifetime.0.to_string()),
+        }
+    }
+}
+
+pub(crate) fn from_trait_bound_modifier(
+    modifier: rustc_hir::TraitBoundModifier,
+) -> TraitBoundModifier {
+    use rustc_hir::TraitBoundModifier::*;
+    match modifier {
+        None => TraitBoundModifier::None,
+        Maybe => TraitBoundModifier::Maybe,
+        MaybeConst => TraitBoundModifier::MaybeConst,
+    }
+}
+
+impl FromWithTcx<clean::Type> for Type {
+    fn from_tcx(ty: clean::Type, tcx: TyCtxt<'_>) -> Self {
+        use clean::Type::{
+            Array, BareFunction, BorrowedRef, DynTrait, Generic, ImplTrait, Infer, Primitive,
+            QPath, RawPointer, Slice, Tuple,
+        };
+
+        match ty {
+            clean::Type::Path { path } => Type::ResolvedPath {
+                name: path.whole_name(),
+                id: from_item_id(path.def_id().into(), tcx),
+                args: path.segments.last().map(|args| Box::new(args.clone().args.into_tcx(tcx))),
+                param_names: Vec::new(),
+            },
+            DynTrait(mut bounds, lt) => {
+                let first_trait = bounds.remove(0).trait_;
+
+                Type::ResolvedPath {
+                    name: first_trait.whole_name(),
+                    id: from_item_id(first_trait.def_id().into(), tcx),
+                    args: first_trait
+                        .segments
+                        .last()
+                        .map(|args| Box::new(args.clone().args.into_tcx(tcx))),
+                    param_names: bounds
+                        .into_iter()
+                        .map(|t| {
+                            clean::GenericBound::TraitBound(t, rustc_hir::TraitBoundModifier::None)
+                        })
+                        .chain(lt.map(clean::GenericBound::Outlives))
+                        .map(|bound| bound.into_tcx(tcx))
+                        .collect(),
+                }
+            }
+            Generic(s) => Type::Generic(s.to_string()),
+            Primitive(p) => Type::Primitive(p.as_sym().to_string()),
+            BareFunction(f) => Type::FunctionPointer(Box::new((*f).into_tcx(tcx))),
+            Tuple(t) => Type::Tuple(t.into_iter().map(|x| x.into_tcx(tcx)).collect()),
+            Slice(t) => Type::Slice(Box::new((*t).into_tcx(tcx))),
+            Array(t, s) => Type::Array { type_: Box::new((*t).into_tcx(tcx)), len: s },
+            ImplTrait(g) => Type::ImplTrait(g.into_iter().map(|x| x.into_tcx(tcx)).collect()),
+            Infer => Type::Infer,
+            RawPointer(mutability, type_) => Type::RawPointer {
+                mutable: mutability == ast::Mutability::Mut,
+                type_: Box::new((*type_).into_tcx(tcx)),
+            },
+            BorrowedRef { lifetime, mutability, type_ } => Type::BorrowedRef {
+                lifetime: lifetime.map(|l| l.0.to_string()),
+                mutable: mutability == ast::Mutability::Mut,
+                type_: Box::new((*type_).into_tcx(tcx)),
+            },
+            QPath { assoc, self_type, trait_, .. } => {
+                // FIXME: should `trait_` be a clean::Path equivalent in JSON?
+                let trait_ = clean::Type::Path { path: trait_ }.into_tcx(tcx);
+                Type::QualifiedPath {
+                    name: assoc.name.to_string(),
+                    args: Box::new(assoc.args.clone().into_tcx(tcx)),
+                    self_type: Box::new((*self_type).into_tcx(tcx)),
+                    trait_: Box::new(trait_),
+                }
+            }
+        }
+    }
+}
+
+impl FromWithTcx<clean::Term> for Term {
+    fn from_tcx(term: clean::Term, tcx: TyCtxt<'_>) -> Term {
+        match term {
+            clean::Term::Type(ty) => Term::Type(FromWithTcx::from_tcx(ty, tcx)),
+            clean::Term::Constant(c) => Term::Constant(FromWithTcx::from_tcx(c, tcx)),
+        }
+    }
+}
+
+impl FromWithTcx<clean::BareFunctionDecl> for FunctionPointer {
+    fn from_tcx(bare_decl: clean::BareFunctionDecl, tcx: TyCtxt<'_>) -> Self {
+        let clean::BareFunctionDecl { unsafety, generic_params, decl, abi } = bare_decl;
+        FunctionPointer {
+            header: Header {
+                unsafe_: matches!(unsafety, rustc_hir::Unsafety::Unsafe),
+                const_: false,
+                async_: false,
+                abi: convert_abi(abi),
+            },
+            generic_params: generic_params.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            decl: decl.into_tcx(tcx),
+        }
+    }
+}
+
+impl FromWithTcx<clean::FnDecl> for FnDecl {
+    fn from_tcx(decl: clean::FnDecl, tcx: TyCtxt<'_>) -> Self {
+        let clean::FnDecl { inputs, output, c_variadic } = decl;
+        FnDecl {
+            inputs: inputs
+                .values
+                .into_iter()
+                .map(|arg| (arg.name.to_string(), arg.type_.into_tcx(tcx)))
+                .collect(),
+            output: match output {
+                clean::FnRetTy::Return(t) => Some(t.into_tcx(tcx)),
+                clean::FnRetTy::DefaultReturn => None,
+            },
+            c_variadic,
+        }
+    }
+}
+
+impl FromWithTcx<clean::Trait> for Trait {
+    fn from_tcx(trait_: clean::Trait, tcx: TyCtxt<'_>) -> Self {
+        let is_auto = trait_.is_auto(tcx);
+        let is_unsafe = trait_.unsafety(tcx) == rustc_hir::Unsafety::Unsafe;
+        let clean::Trait { items, generics, bounds, .. } = trait_;
+        Trait {
+            is_auto,
+            is_unsafe,
+            items: ids(items, tcx),
+            generics: generics.into_tcx(tcx),
+            bounds: bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            implementations: Vec::new(), // Added in JsonRenderer::item
+        }
+    }
+}
+
+impl FromWithTcx<Box<clean::Impl>> for Impl {
+    fn from_tcx(impl_: Box<clean::Impl>, tcx: TyCtxt<'_>) -> Self {
+        let provided_trait_methods = impl_.provided_trait_methods(tcx);
+        let clean::Impl { unsafety, generics, trait_, for_, items, polarity, kind } = *impl_;
+        // FIXME: should `trait_` be a clean::Path equivalent in JSON?
+        let trait_ = trait_.map(|path| clean::Type::Path { path }.into_tcx(tcx));
+        // FIXME: use something like ImplKind in JSON?
+        let (synthetic, blanket_impl) = match kind {
+            clean::ImplKind::Normal | clean::ImplKind::FakeVaradic => (false, None),
+            clean::ImplKind::Auto => (true, None),
+            clean::ImplKind::Blanket(ty) => (false, Some(*ty)),
+        };
+        let negative_polarity = match polarity {
+            ty::ImplPolarity::Positive | ty::ImplPolarity::Reservation => false,
+            ty::ImplPolarity::Negative => true,
+        };
+        Impl {
+            is_unsafe: unsafety == rustc_hir::Unsafety::Unsafe,
+            generics: generics.into_tcx(tcx),
+            provided_trait_methods: provided_trait_methods
+                .into_iter()
+                .map(|x| x.to_string())
+                .collect(),
+            trait_,
+            for_: for_.into_tcx(tcx),
+            items: ids(items, tcx),
+            negative: negative_polarity,
+            synthetic,
+            blanket_impl: blanket_impl.map(|x| x.into_tcx(tcx)),
+        }
+    }
+}
+
+pub(crate) fn from_function(
+    function: Box<clean::Function>,
+    header: rustc_hir::FnHeader,
+    tcx: TyCtxt<'_>,
+) -> Function {
+    let clean::Function { decl, generics } = *function;
+    Function {
+        decl: decl.into_tcx(tcx),
+        generics: generics.into_tcx(tcx),
+        header: from_fn_header(&header),
+    }
+}
+
+pub(crate) fn from_function_method(
+    function: Box<clean::Function>,
+    has_body: bool,
+    header: rustc_hir::FnHeader,
+    tcx: TyCtxt<'_>,
+) -> Method {
+    let clean::Function { decl, generics } = *function;
+    Method {
+        decl: decl.into_tcx(tcx),
+        generics: generics.into_tcx(tcx),
+        header: from_fn_header(&header),
+        has_body,
+    }
+}
+
+impl FromWithTcx<clean::Enum> for Enum {
+    fn from_tcx(enum_: clean::Enum, tcx: TyCtxt<'_>) -> Self {
+        let variants_stripped = enum_.has_stripped_entries();
+        let clean::Enum { variants, generics } = enum_;
+        Enum {
+            generics: generics.into_tcx(tcx),
+            variants_stripped,
+            variants: ids(variants, tcx),
+            impls: Vec::new(), // Added in JsonRenderer::item
+        }
+    }
+}
+
+impl FromWithTcx<clean::VariantStruct> for Struct {
+    fn from_tcx(struct_: clean::VariantStruct, tcx: TyCtxt<'_>) -> Self {
+        let fields_stripped = struct_.has_stripped_entries();
+        let clean::VariantStruct { struct_type, fields } = struct_;
+        Struct {
+            struct_type: from_ctor_kind(struct_type),
+            generics: Generics { params: vec![], where_predicates: vec![] },
+            fields_stripped,
+            fields: ids(fields, tcx),
+            impls: Vec::new(),
+        }
+    }
+}
+
+impl FromWithTcx<clean::Variant> for Variant {
+    fn from_tcx(variant: clean::Variant, tcx: TyCtxt<'_>) -> Self {
+        use clean::Variant::*;
+        match variant {
+            CLike => Variant::Plain,
+            Tuple(fields) => Variant::Tuple(
+                fields
+                    .into_iter()
+                    .map(|f| {
+                        if let clean::StructFieldItem(ty) = *f.kind {
+                            ty.into_tcx(tcx)
+                        } else {
+                            unreachable!()
+                        }
+                    })
+                    .collect(),
+            ),
+            Struct(s) => Variant::Struct(ids(s.fields, tcx)),
+        }
+    }
+}
+
+impl FromWithTcx<clean::Import> for Import {
+    fn from_tcx(import: clean::Import, tcx: TyCtxt<'_>) -> Self {
+        use clean::ImportKind::*;
+        match import.kind {
+            Simple(s) => Import {
+                source: import.source.path.whole_name(),
+                name: s.to_string(),
+                id: import.source.did.map(ItemId::from).map(|i| from_item_id(i, tcx)),
+                glob: false,
+            },
+            Glob => Import {
+                source: import.source.path.whole_name(),
+                name: import
+                    .source
+                    .path
+                    .last_opt()
+                    .unwrap_or_else(|| Symbol::intern("*"))
+                    .to_string(),
+                id: import.source.did.map(ItemId::from).map(|i| from_item_id(i, tcx)),
+                glob: true,
+            },
+        }
+    }
+}
+
+impl FromWithTcx<clean::ProcMacro> for ProcMacro {
+    fn from_tcx(mac: clean::ProcMacro, _tcx: TyCtxt<'_>) -> Self {
+        ProcMacro {
+            kind: from_macro_kind(mac.kind),
+            helpers: mac.helpers.iter().map(|x| x.to_string()).collect(),
+        }
+    }
+}
+
+pub(crate) fn from_macro_kind(kind: rustc_span::hygiene::MacroKind) -> MacroKind {
+    use rustc_span::hygiene::MacroKind::*;
+    match kind {
+        Bang => MacroKind::Bang,
+        Attr => MacroKind::Attr,
+        Derive => MacroKind::Derive,
+    }
+}
+
+impl FromWithTcx<Box<clean::Typedef>> for Typedef {
+    fn from_tcx(typedef: Box<clean::Typedef>, tcx: TyCtxt<'_>) -> Self {
+        let clean::Typedef { type_, generics, item_type: _ } = *typedef;
+        Typedef { type_: type_.into_tcx(tcx), generics: generics.into_tcx(tcx) }
+    }
+}
+
+impl FromWithTcx<clean::OpaqueTy> for OpaqueTy {
+    fn from_tcx(opaque: clean::OpaqueTy, tcx: TyCtxt<'_>) -> Self {
+        OpaqueTy {
+            bounds: opaque.bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+            generics: opaque.generics.into_tcx(tcx),
+        }
+    }
+}
+
+impl FromWithTcx<clean::Static> for Static {
+    fn from_tcx(stat: clean::Static, tcx: TyCtxt<'_>) -> Self {
+        Static {
+            type_: stat.type_.into_tcx(tcx),
+            mutable: stat.mutability == ast::Mutability::Mut,
+            expr: stat.expr.map(|e| print_const_expr(tcx, e)).unwrap_or_default(),
+        }
+    }
+}
+
+impl FromWithTcx<clean::TraitAlias> for TraitAlias {
+    fn from_tcx(alias: clean::TraitAlias, tcx: TyCtxt<'_>) -> Self {
+        TraitAlias {
+            generics: alias.generics.into_tcx(tcx),
+            params: alias.bounds.into_iter().map(|x| x.into_tcx(tcx)).collect(),
+        }
+    }
+}
+
+impl FromWithTcx<ItemType> for ItemKind {
+    fn from_tcx(kind: ItemType, _tcx: TyCtxt<'_>) -> Self {
+        use ItemType::*;
+        match kind {
+            Module => ItemKind::Module,
+            ExternCrate => ItemKind::ExternCrate,
+            Import => ItemKind::Import,
+            Struct => ItemKind::Struct,
+            Union => ItemKind::Union,
+            Enum => ItemKind::Enum,
+            Function => ItemKind::Function,
+            Typedef => ItemKind::Typedef,
+            OpaqueTy => ItemKind::OpaqueTy,
+            Static => ItemKind::Static,
+            Constant => ItemKind::Constant,
+            Trait => ItemKind::Trait,
+            Impl => ItemKind::Impl,
+            TyMethod | Method => ItemKind::Method,
+            StructField => ItemKind::StructField,
+            Variant => ItemKind::Variant,
+            Macro => ItemKind::Macro,
+            Primitive => ItemKind::Primitive,
+            AssocConst => ItemKind::AssocConst,
+            AssocType => ItemKind::AssocType,
+            ForeignType => ItemKind::ForeignType,
+            Keyword => ItemKind::Keyword,
+            TraitAlias => ItemKind::TraitAlias,
+            ProcAttribute => ItemKind::ProcAttribute,
+            ProcDerive => ItemKind::ProcDerive,
+        }
+    }
+}
+
+fn ids(items: impl IntoIterator<Item = clean::Item>, tcx: TyCtxt<'_>) -> Vec<Id> {
+    items
+        .into_iter()
+        .filter(|x| !x.is_stripped() && !x.is_keyword())
+        .map(|i| from_item_id_with_name(i.item_id, tcx, i.name))
+        .collect()
+}
diff --git a/src/librustdoc/json/mod.rs b/src/librustdoc/json/mod.rs
new file mode 100644
index 000000000..6364d00d0
--- /dev/null
+++ b/src/librustdoc/json/mod.rs
@@ -0,0 +1,327 @@
+//! Rustdoc's JSON backend
+//!
+//! This module contains the logic for rendering a crate as JSON rather than the normal static HTML
+//! output. See [the RFC](https://github.com/rust-lang/rfcs/pull/2963) and the [`types`] module
+//! docs for usage and details.
+
+mod conversions;
+
+use std::cell::RefCell;
+use std::fs::{create_dir_all, File};
+use std::io::{BufWriter, Write};
+use std::path::PathBuf;
+use std::rc::Rc;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::Session;
+use rustc_span::def_id::LOCAL_CRATE;
+
+use rustdoc_json_types as types;
+
+use crate::clean::types::{ExternalCrate, ExternalLocation};
+use crate::clean::ItemKind;
+use crate::config::RenderOptions;
+use crate::docfs::PathError;
+use crate::error::Error;
+use crate::formats::cache::Cache;
+use crate::formats::FormatRenderer;
+use crate::json::conversions::{from_item_id, from_item_id_with_name, IntoWithTcx};
+use crate::{clean, try_err};
+
+#[derive(Clone)]
+pub(crate) struct JsonRenderer<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    /// A mapping of IDs that contains all local items for this crate which gets output as a top
+    /// level field of the JSON blob.
+    index: Rc<RefCell<FxHashMap<types::Id, types::Item>>>,
+    /// The directory where the blob will be written to.
+    out_path: PathBuf,
+    cache: Rc<Cache>,
+}
+
+impl<'tcx> JsonRenderer<'tcx> {
+    fn sess(&self) -> &'tcx Session {
+        self.tcx.sess
+    }
+
+    fn get_trait_implementors(&mut self, id: DefId) -> Vec<types::Id> {
+        Rc::clone(&self.cache)
+            .implementors
+            .get(&id)
+            .map(|implementors| {
+                implementors
+                    .iter()
+                    .map(|i| {
+                        let item = &i.impl_item;
+                        self.item(item.clone()).unwrap();
+                        from_item_id_with_name(item.item_id, self.tcx, item.name)
+                    })
+                    .collect()
+            })
+            .unwrap_or_default()
+    }
+
+    fn get_impls(&mut self, id: DefId) -> Vec<types::Id> {
+        Rc::clone(&self.cache)
+            .impls
+            .get(&id)
+            .map(|impls| {
+                impls
+                    .iter()
+                    .filter_map(|i| {
+                        let item = &i.impl_item;
+
+                        // HACK(hkmatsumoto): For impls of primitive types, we index them
+                        // regardless of whether they're local. This is because users can
+                        // document primitive items in an arbitrary crate by using
+                        // `doc(primitive)`.
+                        let mut is_primitive_impl = false;
+                        if let clean::types::ItemKind::ImplItem(ref impl_) = *item.kind {
+                            if impl_.trait_.is_none() {
+                                if let clean::types::Type::Primitive(_) = impl_.for_ {
+                                    is_primitive_impl = true;
+                                }
+                            }
+                        }
+
+                        if item.item_id.is_local() || is_primitive_impl {
+                            self.item(item.clone()).unwrap();
+                            Some(from_item_id_with_name(item.item_id, self.tcx, item.name))
+                        } else {
+                            None
+                        }
+                    })
+                    .collect()
+            })
+            .unwrap_or_default()
+    }
+
+    fn get_trait_items(&mut self) -> Vec<(types::Id, types::Item)> {
+        Rc::clone(&self.cache)
+            .traits
+            .iter()
+            .filter_map(|(&id, trait_item)| {
+                // only need to synthesize items for external traits
+                if !id.is_local() {
+                    let trait_item = &trait_item.trait_;
+                    trait_item.items.clone().into_iter().for_each(|i| self.item(i).unwrap());
+                    let item_id = from_item_id(id.into(), self.tcx);
+                    Some((
+                        item_id.clone(),
+                        types::Item {
+                            id: item_id,
+                            crate_id: id.krate.as_u32(),
+                            name: self
+                                .cache
+                                .paths
+                                .get(&id)
+                                .unwrap_or_else(|| {
+                                    self.cache
+                                        .external_paths
+                                        .get(&id)
+                                        .expect("Trait should either be in local or external paths")
+                                })
+                                .0
+                                .last()
+                                .map(|s| s.to_string()),
+                            visibility: types::Visibility::Public,
+                            inner: types::ItemEnum::Trait(trait_item.clone().into_tcx(self.tcx)),
+                            span: None,
+                            docs: Default::default(),
+                            links: Default::default(),
+                            attrs: Default::default(),
+                            deprecation: Default::default(),
+                        },
+                    ))
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+}
+
+impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
+    fn descr() -> &'static str {
+        "json"
+    }
+
+    const RUN_ON_MODULE: bool = false;
+
+    fn init(
+        krate: clean::Crate,
+        options: RenderOptions,
+        cache: Cache,
+        tcx: TyCtxt<'tcx>,
+    ) -> Result<(Self, clean::Crate), Error> {
+        debug!("Initializing json renderer");
+        Ok((
+            JsonRenderer {
+                tcx,
+                index: Rc::new(RefCell::new(FxHashMap::default())),
+                out_path: options.output,
+                cache: Rc::new(cache),
+            },
+            krate,
+        ))
+    }
+
+    fn make_child_renderer(&self) -> Self {
+        self.clone()
+    }
+
+    /// Inserts an item into the index. This should be used rather than directly calling insert on
+    /// the hashmap because certain items (traits and types) need to have their mappings for trait
+    /// implementations filled out before they're inserted.
+    fn item(&mut self, item: clean::Item) -> Result<(), Error> {
+        trace!("rendering {} {:?}", item.type_(), item.name);
+
+        // Flatten items that recursively store other items. We include orphaned items from
+        // stripped modules and etc that are otherwise reachable.
+        if let ItemKind::StrippedItem(inner) = &*item.kind {
+            inner.inner_items().for_each(|i| self.item(i.clone()).unwrap());
+        }
+
+        // Flatten items that recursively store other items
+        item.kind.inner_items().for_each(|i| self.item(i.clone()).unwrap());
+
+        let name = item.name;
+        let item_id = item.item_id;
+        if let Some(mut new_item) = self.convert_item(item) {
+            let can_be_ignored = match new_item.inner {
+                types::ItemEnum::Trait(ref mut t) => {
+                    t.implementations = self.get_trait_implementors(item_id.expect_def_id());
+                    false
+                }
+                types::ItemEnum::Struct(ref mut s) => {
+                    s.impls = self.get_impls(item_id.expect_def_id());
+                    false
+                }
+                types::ItemEnum::Enum(ref mut e) => {
+                    e.impls = self.get_impls(item_id.expect_def_id());
+                    false
+                }
+                types::ItemEnum::Union(ref mut u) => {
+                    u.impls = self.get_impls(item_id.expect_def_id());
+                    false
+                }
+
+                types::ItemEnum::Method(_)
+                | types::ItemEnum::AssocConst { .. }
+                | types::ItemEnum::AssocType { .. }
+                | types::ItemEnum::PrimitiveType(_) => true,
+                types::ItemEnum::Module(_)
+                | types::ItemEnum::ExternCrate { .. }
+                | types::ItemEnum::Import(_)
+                | types::ItemEnum::StructField(_)
+                | types::ItemEnum::Variant(_)
+                | types::ItemEnum::Function(_)
+                | types::ItemEnum::TraitAlias(_)
+                | types::ItemEnum::Impl(_)
+                | types::ItemEnum::Typedef(_)
+                | types::ItemEnum::OpaqueTy(_)
+                | types::ItemEnum::Constant(_)
+                | types::ItemEnum::Static(_)
+                | types::ItemEnum::ForeignType
+                | types::ItemEnum::Macro(_)
+                | types::ItemEnum::ProcMacro(_) => false,
+            };
+            let removed = self
+                .index
+                .borrow_mut()
+                .insert(from_item_id_with_name(item_id, self.tcx, name), new_item.clone());
+
+            // FIXME(adotinthevoid): Currently, the index is duplicated. This is a sanity check
+            // to make sure the items are unique. The main place this happens is when an item, is
+            // reexported in more than one place. See `rustdoc-json/reexport/in_root_and_mod`
+            if let Some(old_item) = removed {
+                // In case of generic implementations (like `impl<T> Trait for T {}`), all the
+                // inner items will be duplicated so we can ignore if they are slightly different.
+                if !can_be_ignored {
+                    assert_eq!(old_item, new_item);
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn mod_item_in(&mut self, _item: &clean::Item) -> Result<(), Error> {
+        unreachable!("RUN_ON_MODULE = false should never call mod_item_in")
+    }
+
+    fn after_krate(&mut self) -> Result<(), Error> {
+        debug!("Done with crate");
+
+        for primitive in Rc::clone(&self.cache).primitive_locations.values() {
+            self.get_impls(*primitive);
+        }
+
+        let e = ExternalCrate { crate_num: LOCAL_CRATE };
+
+        let mut index = (*self.index).clone().into_inner();
+        index.extend(self.get_trait_items());
+        // This needs to be the default HashMap for compatibility with the public interface for
+        // rustdoc-json-types
+        #[allow(rustc::default_hash_types)]
+        let output = types::Crate {
+            root: types::Id(format!("0:0:{}", e.name(self.tcx).as_u32())),
+            crate_version: self.cache.crate_version.clone(),
+            includes_private: self.cache.document_private,
+            index: index.into_iter().collect(),
+            paths: self
+                .cache
+                .paths
+                .clone()
+                .into_iter()
+                .chain(self.cache.external_paths.clone().into_iter())
+                .map(|(k, (path, kind))| {
+                    (
+                        from_item_id(k.into(), self.tcx),
+                        types::ItemSummary {
+                            crate_id: k.krate.as_u32(),
+                            path: path.iter().map(|s| s.to_string()).collect(),
+                            kind: kind.into_tcx(self.tcx),
+                        },
+                    )
+                })
+                .collect(),
+            external_crates: self
+                .cache
+                .extern_locations
+                .iter()
+                .map(|(crate_num, external_location)| {
+                    let e = ExternalCrate { crate_num: *crate_num };
+                    (
+                        crate_num.as_u32(),
+                        types::ExternalCrate {
+                            name: e.name(self.tcx).to_string(),
+                            html_root_url: match external_location {
+                                ExternalLocation::Remote(s) => Some(s.clone()),
+                                _ => None,
+                            },
+                        },
+                    )
+                })
+                .collect(),
+            format_version: types::FORMAT_VERSION,
+        };
+        let out_dir = self.out_path.clone();
+        try_err!(create_dir_all(&out_dir), out_dir);
+
+        let mut p = out_dir;
+        p.push(output.index.get(&output.root).unwrap().name.clone().unwrap());
+        p.set_extension("json");
+        let mut file = BufWriter::new(try_err!(File::create(&p), p));
+        serde_json::ser::to_writer(&mut file, &output).unwrap();
+        try_err!(file.flush(), p);
+
+        Ok(())
+    }
+
+    fn cache(&self) -> &Cache {
+        &self.cache
+    }
+}
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
new file mode 100644
index 000000000..92380d124
--- /dev/null
+++ b/src/librustdoc/lib.rs
@@ -0,0 +1,868 @@
+#![doc(
+    html_root_url = "https://doc.rust-lang.org/nightly/",
+    html_playground_url = "https://play.rust-lang.org/"
+)]
+#![feature(rustc_private)]
+#![feature(array_methods)]
+#![feature(assert_matches)]
+#![feature(box_patterns)]
+#![feature(control_flow_enum)]
+#![feature(drain_filter)]
+#![feature(let_chains)]
+#![feature(let_else)]
+#![feature(test)]
+#![feature(never_type)]
+#![feature(once_cell)]
+#![feature(type_ascription)]
+#![feature(iter_intersperse)]
+#![feature(type_alias_impl_trait)]
+#![feature(generic_associated_types)]
+#![recursion_limit = "256"]
+#![warn(rustc::internal)]
+#![allow(clippy::collapsible_if, clippy::collapsible_else_if)]
+#![allow(rustc::potential_query_instability)]
+
+#[macro_use]
+extern crate tracing;
+
+// N.B. these need `extern crate` even in 2018 edition
+// because they're loaded implicitly from the sysroot.
+// The reason they're loaded from the sysroot is because
+// the rustdoc artifacts aren't stored in rustc's cargo target directory.
+// So if `rustc` was specified in Cargo.toml, this would spuriously rebuild crates.
+//
+// Dependencies listed in Cargo.toml do not need `extern crate`.
+
+extern crate rustc_ast;
+extern crate rustc_ast_pretty;
+extern crate rustc_attr;
+extern crate rustc_const_eval;
+extern crate rustc_data_structures;
+extern crate rustc_driver;
+extern crate rustc_errors;
+extern crate rustc_expand;
+extern crate rustc_feature;
+extern crate rustc_hir;
+extern crate rustc_hir_pretty;
+extern crate rustc_index;
+extern crate rustc_infer;
+extern crate rustc_interface;
+extern crate rustc_lexer;
+extern crate rustc_lint;
+extern crate rustc_lint_defs;
+extern crate rustc_macros;
+extern crate rustc_metadata;
+extern crate rustc_middle;
+extern crate rustc_parse;
+extern crate rustc_passes;
+extern crate rustc_resolve;
+extern crate rustc_serialize;
+extern crate rustc_session;
+extern crate rustc_span;
+extern crate rustc_target;
+extern crate rustc_trait_selection;
+extern crate rustc_typeck;
+extern crate test;
+
+// See docs in https://github.com/rust-lang/rust/blob/master/compiler/rustc/src/main.rs
+// about jemalloc.
+#[cfg(feature = "jemalloc")]
+extern crate jemalloc_sys;
+
+use std::default::Default;
+use std::env::{self, VarError};
+use std::io;
+use std::process;
+
+use rustc_driver::abort_on_err;
+use rustc_errors::ErrorGuaranteed;
+use rustc_interface::interface;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::config::{make_crate_type_option, ErrorOutputType, RustcOptGroup};
+use rustc_session::getopts;
+use rustc_session::{early_error, early_warn};
+
+use crate::clean::utils::DOC_RUST_LANG_ORG_CHANNEL;
+use crate::passes::collect_intra_doc_links;
+
+/// A macro to create a FxHashMap.
+///
+/// Example:
+///
+/// ```ignore(cannot-test-this-because-non-exported-macro)
+/// let letters = map!{"a" => "b", "c" => "d"};
+/// ```
+///
+/// Trailing commas are allowed.
+/// Commas between elements are required (even if the expression is a block).
+macro_rules! map {
+    ($( $key: expr => $val: expr ),* $(,)*) => {{
+        let mut map = ::rustc_data_structures::fx::FxHashMap::default();
+        $( map.insert($key, $val); )*
+        map
+    }}
+}
+
+mod clean;
+mod config;
+mod core;
+mod docfs;
+mod doctest;
+mod error;
+mod externalfiles;
+mod fold;
+mod formats;
+// used by the error-index generator, so it needs to be public
+pub mod html;
+mod json;
+pub(crate) mod lint;
+mod markdown;
+mod passes;
+mod scrape_examples;
+mod theme;
+mod visit;
+mod visit_ast;
+mod visit_lib;
+
+pub fn main() {
+    // See docs in https://github.com/rust-lang/rust/blob/master/compiler/rustc/src/main.rs
+    // about jemalloc.
+    #[cfg(feature = "jemalloc")]
+    {
+        use std::os::raw::{c_int, c_void};
+
+        #[used]
+        static _F1: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::calloc;
+        #[used]
+        static _F2: unsafe extern "C" fn(*mut *mut c_void, usize, usize) -> c_int =
+            jemalloc_sys::posix_memalign;
+        #[used]
+        static _F3: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::aligned_alloc;
+        #[used]
+        static _F4: unsafe extern "C" fn(usize) -> *mut c_void = jemalloc_sys::malloc;
+        #[used]
+        static _F5: unsafe extern "C" fn(*mut c_void, usize) -> *mut c_void = jemalloc_sys::realloc;
+        #[used]
+        static _F6: unsafe extern "C" fn(*mut c_void) = jemalloc_sys::free;
+
+        #[cfg(target_os = "macos")]
+        {
+            extern "C" {
+                fn _rjem_je_zone_register();
+            }
+
+            #[used]
+            static _F7: unsafe extern "C" fn() = _rjem_je_zone_register;
+        }
+    }
+
+    rustc_driver::set_sigpipe_handler();
+    rustc_driver::install_ice_hook();
+
+    // When using CI artifacts (with `download_stage1 = true`), tracing is unconditionally built
+    // with `--features=static_max_level_info`, which disables almost all rustdoc logging. To avoid
+    // this, compile our own version of `tracing` that logs all levels.
+    // NOTE: this compiles both versions of tracing unconditionally, because
+    // - The compile time hit is not that bad, especially compared to rustdoc's incremental times, and
+    // - Otherwise, there's no warning that logging is being ignored when `download_stage1 = true`.
+    // NOTE: The reason this doesn't show double logging when `download_stage1 = false` and
+    // `debug_logging = true` is because all rustc logging goes to its version of tracing (the one
+    // in the sysroot), and all of rustdoc's logging goes to its version (the one in Cargo.toml).
+    init_logging();
+    rustc_driver::init_env_logger("RUSTDOC_LOG");
+
+    let exit_code = rustc_driver::catch_with_exit_code(|| match get_args() {
+        Some(args) => main_args(&args),
+        _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
+    });
+    process::exit(exit_code);
+}
+
+fn init_logging() {
+    let color_logs = match std::env::var("RUSTDOC_LOG_COLOR").as_deref() {
+        Ok("always") => true,
+        Ok("never") => false,
+        Ok("auto") | Err(VarError::NotPresent) => atty::is(atty::Stream::Stdout),
+        Ok(value) => early_error(
+            ErrorOutputType::default(),
+            &format!("invalid log color value '{}': expected one of always, never, or auto", value),
+        ),
+        Err(VarError::NotUnicode(value)) => early_error(
+            ErrorOutputType::default(),
+            &format!(
+                "invalid log color value '{}': expected one of always, never, or auto",
+                value.to_string_lossy()
+            ),
+        ),
+    };
+    let filter = tracing_subscriber::EnvFilter::from_env("RUSTDOC_LOG");
+    let layer = tracing_tree::HierarchicalLayer::default()
+        .with_writer(io::stderr)
+        .with_indent_lines(true)
+        .with_ansi(color_logs)
+        .with_targets(true)
+        .with_wraparound(10)
+        .with_verbose_exit(true)
+        .with_verbose_entry(true)
+        .with_indent_amount(2);
+    #[cfg(parallel_compiler)]
+    let layer = layer.with_thread_ids(true).with_thread_names(true);
+
+    use tracing_subscriber::layer::SubscriberExt;
+    let subscriber = tracing_subscriber::Registry::default().with(filter).with(layer);
+    tracing::subscriber::set_global_default(subscriber).unwrap();
+}
+
+fn get_args() -> Option<Vec<String>> {
+    env::args_os()
+        .enumerate()
+        .map(|(i, arg)| {
+            arg.into_string()
+                .map_err(|arg| {
+                    early_warn(
+                        ErrorOutputType::default(),
+                        &format!("Argument {} is not valid Unicode: {:?}", i, arg),
+                    );
+                })
+                .ok()
+        })
+        .collect()
+}
+
+fn opts() -> Vec<RustcOptGroup> {
+    let stable: fn(_, fn(&mut getopts::Options) -> &mut _) -> _ = RustcOptGroup::stable;
+    let unstable: fn(_, fn(&mut getopts::Options) -> &mut _) -> _ = RustcOptGroup::unstable;
+    vec![
+        stable("h", |o| o.optflagmulti("h", "help", "show this help message")),
+        stable("V", |o| o.optflagmulti("V", "version", "print rustdoc's version")),
+        stable("v", |o| o.optflagmulti("v", "verbose", "use verbose output")),
+        stable("w", |o| o.optopt("w", "output-format", "the output type to write", "[html]")),
+        stable("output", |o| {
+            o.optopt(
+                "",
+                "output",
+                "Which directory to place the output. \
+                 This option is deprecated, use --out-dir instead.",
+                "PATH",
+            )
+        }),
+        stable("o", |o| o.optopt("o", "out-dir", "which directory to place the output", "PATH")),
+        stable("crate-name", |o| {
+            o.optopt("", "crate-name", "specify the name of this crate", "NAME")
+        }),
+        make_crate_type_option(),
+        stable("L", |o| {
+            o.optmulti("L", "library-path", "directory to add to crate search path", "DIR")
+        }),
+        stable("cfg", |o| o.optmulti("", "cfg", "pass a --cfg to rustc", "")),
+        unstable("check-cfg", |o| o.optmulti("", "check-cfg", "pass a --check-cfg to rustc", "")),
+        stable("extern", |o| o.optmulti("", "extern", "pass an --extern to rustc", "NAME[=PATH]")),
+        unstable("extern-html-root-url", |o| {
+            o.optmulti(
+                "",
+                "extern-html-root-url",
+                "base URL to use for dependencies; for example, \
+                 \"std=/doc\" links std::vec::Vec to /doc/std/vec/struct.Vec.html",
+                "NAME=URL",
+            )
+        }),
+        unstable("extern-html-root-takes-precedence", |o| {
+            o.optflagmulti(
+                "",
+                "extern-html-root-takes-precedence",
+                "give precedence to `--extern-html-root-url`, not `html_root_url`",
+            )
+        }),
+        stable("C", |o| {
+            o.optmulti("C", "codegen", "pass a codegen option to rustc", "OPT[=VALUE]")
+        }),
+        stable("document-private-items", |o| {
+            o.optflagmulti("", "document-private-items", "document private items")
+        }),
+        unstable("document-hidden-items", |o| {
+            o.optflagmulti("", "document-hidden-items", "document items that have doc(hidden)")
+        }),
+        stable("test", |o| o.optflagmulti("", "test", "run code examples as tests")),
+        stable("test-args", |o| {
+            o.optmulti("", "test-args", "arguments to pass to the test runner", "ARGS")
+        }),
+        unstable("test-run-directory", |o| {
+            o.optopt(
+                "",
+                "test-run-directory",
+                "The working directory in which to run tests",
+                "PATH",
+            )
+        }),
+        stable("target", |o| o.optopt("", "target", "target triple to document", "TRIPLE")),
+        stable("markdown-css", |o| {
+            o.optmulti(
+                "",
+                "markdown-css",
+                "CSS files to include via <link> in a rendered Markdown file",
+                "FILES",
+            )
+        }),
+        stable("html-in-header", |o| {
+            o.optmulti(
+                "",
+                "html-in-header",
+                "files to include inline in the <head> section of a rendered Markdown file \
+                 or generated documentation",
+                "FILES",
+            )
+        }),
+        stable("html-before-content", |o| {
+            o.optmulti(
+                "",
+                "html-before-content",
+                "files to include inline between <body> and the content of a rendered \
+                 Markdown file or generated documentation",
+                "FILES",
+            )
+        }),
+        stable("html-after-content", |o| {
+            o.optmulti(
+                "",
+                "html-after-content",
+                "files to include inline between the content and </body> of a rendered \
+                 Markdown file or generated documentation",
+                "FILES",
+            )
+        }),
+        unstable("markdown-before-content", |o| {
+            o.optmulti(
+                "",
+                "markdown-before-content",
+                "files to include inline between <body> and the content of a rendered \
+                 Markdown file or generated documentation",
+                "FILES",
+            )
+        }),
+        unstable("markdown-after-content", |o| {
+            o.optmulti(
+                "",
+                "markdown-after-content",
+                "files to include inline between the content and </body> of a rendered \
+                 Markdown file or generated documentation",
+                "FILES",
+            )
+        }),
+        stable("markdown-playground-url", |o| {
+            o.optopt("", "markdown-playground-url", "URL to send code snippets to", "URL")
+        }),
+        stable("markdown-no-toc", |o| {
+            o.optflagmulti("", "markdown-no-toc", "don't include table of contents")
+        }),
+        stable("e", |o| {
+            o.optopt(
+                "e",
+                "extend-css",
+                "To add some CSS rules with a given file to generate doc with your \
+                 own theme. However, your theme might break if the rustdoc's generated HTML \
+                 changes, so be careful!",
+                "PATH",
+            )
+        }),
+        unstable("Z", |o| {
+            o.optmulti("Z", "", "unstable / perma-unstable options (only on nightly build)", "FLAG")
+        }),
+        stable("sysroot", |o| o.optopt("", "sysroot", "Override the system root", "PATH")),
+        unstable("playground-url", |o| {
+            o.optopt(
+                "",
+                "playground-url",
+                "URL to send code snippets to, may be reset by --markdown-playground-url \
+                 or `#![doc(html_playground_url=...)]`",
+                "URL",
+            )
+        }),
+        unstable("display-doctest-warnings", |o| {
+            o.optflagmulti(
+                "",
+                "display-doctest-warnings",
+                "show warnings that originate in doctests",
+            )
+        }),
+        stable("crate-version", |o| {
+            o.optopt("", "crate-version", "crate version to print into documentation", "VERSION")
+        }),
+        unstable("sort-modules-by-appearance", |o| {
+            o.optflagmulti(
+                "",
+                "sort-modules-by-appearance",
+                "sort modules by where they appear in the program, rather than alphabetically",
+            )
+        }),
+        stable("default-theme", |o| {
+            o.optopt(
+                "",
+                "default-theme",
+                "Set the default theme. THEME should be the theme name, generally lowercase. \
+                 If an unknown default theme is specified, the builtin default is used. \
+                 The set of themes, and the rustdoc built-in default, are not stable.",
+                "THEME",
+            )
+        }),
+        unstable("default-setting", |o| {
+            o.optmulti(
+                "",
+                "default-setting",
+                "Default value for a rustdoc setting (used when \"rustdoc-SETTING\" is absent \
+                 from web browser Local Storage). If VALUE is not supplied, \"true\" is used. \
+                 Supported SETTINGs and VALUEs are not documented and not stable.",
+                "SETTING[=VALUE]",
+            )
+        }),
+        stable("theme", |o| {
+            o.optmulti(
+                "",
+                "theme",
+                "additional themes which will be added to the generated docs",
+                "FILES",
+            )
+        }),
+        stable("check-theme", |o| {
+            o.optmulti("", "check-theme", "check if given theme is valid", "FILES")
+        }),
+        unstable("resource-suffix", |o| {
+            o.optopt(
+                "",
+                "resource-suffix",
+                "suffix to add to CSS and JavaScript files, e.g., \"light.css\" will become \
+                 \"light-suffix.css\"",
+                "PATH",
+            )
+        }),
+        stable("edition", |o| {
+            o.optopt(
+                "",
+                "edition",
+                "edition to use when compiling rust code (default: 2015)",
+                "EDITION",
+            )
+        }),
+        stable("color", |o| {
+            o.optopt(
+                "",
+                "color",
+                "Configure coloring of output:
+                                          auto   = colorize, if output goes to a tty (default);
+                                          always = always colorize output;
+                                          never  = never colorize output",
+                "auto|always|never",
+            )
+        }),
+        stable("error-format", |o| {
+            o.optopt(
+                "",
+                "error-format",
+                "How errors and other messages are produced",
+                "human|json|short",
+            )
+        }),
+        unstable("diagnostic-width", |o| {
+            o.optopt(
+                "",
+                "diagnostic-width",
+                "Provide width of the output for truncated error messages",
+                "WIDTH",
+            )
+        }),
+        stable("json", |o| {
+            o.optopt("", "json", "Configure the structure of JSON diagnostics", "CONFIG")
+        }),
+        unstable("disable-minification", |o| {
+            o.optflagmulti("", "disable-minification", "Disable minification applied on JS files")
+        }),
+        stable("allow", |o| o.optmulti("A", "allow", "Set lint allowed", "LINT")),
+        stable("warn", |o| o.optmulti("W", "warn", "Set lint warnings", "LINT")),
+        stable("force-warn", |o| o.optmulti("", "force-warn", "Set lint force-warn", "LINT")),
+        stable("deny", |o| o.optmulti("D", "deny", "Set lint denied", "LINT")),
+        stable("forbid", |o| o.optmulti("F", "forbid", "Set lint forbidden", "LINT")),
+        stable("cap-lints", |o| {
+            o.optmulti(
+                "",
+                "cap-lints",
+                "Set the most restrictive lint level. \
+                 More restrictive lints are capped at this \
+                 level. By default, it is at `forbid` level.",
+                "LEVEL",
+            )
+        }),
+        unstable("index-page", |o| {
+            o.optopt("", "index-page", "Markdown file to be used as index page", "PATH")
+        }),
+        unstable("enable-index-page", |o| {
+            o.optflagmulti("", "enable-index-page", "To enable generation of the index page")
+        }),
+        unstable("static-root-path", |o| {
+            o.optopt(
+                "",
+                "static-root-path",
+                "Path string to force loading static files from in output pages. \
+                 If not set, uses combinations of '../' to reach the documentation root.",
+                "PATH",
+            )
+        }),
+        unstable("disable-per-crate-search", |o| {
+            o.optflagmulti(
+                "",
+                "disable-per-crate-search",
+                "disables generating the crate selector on the search box",
+            )
+        }),
+        unstable("persist-doctests", |o| {
+            o.optopt(
+                "",
+                "persist-doctests",
+                "Directory to persist doctest executables into",
+                "PATH",
+            )
+        }),
+        unstable("show-coverage", |o| {
+            o.optflagmulti(
+                "",
+                "show-coverage",
+                "calculate percentage of public items with documentation",
+            )
+        }),
+        unstable("enable-per-target-ignores", |o| {
+            o.optflagmulti(
+                "",
+                "enable-per-target-ignores",
+                "parse ignore-foo for ignoring doctests on a per-target basis",
+            )
+        }),
+        unstable("runtool", |o| {
+            o.optopt(
+                "",
+                "runtool",
+                "",
+                "The tool to run tests with when building for a different target than host",
+            )
+        }),
+        unstable("runtool-arg", |o| {
+            o.optmulti(
+                "",
+                "runtool-arg",
+                "",
+                "One (of possibly many) arguments to pass to the runtool",
+            )
+        }),
+        unstable("test-builder", |o| {
+            o.optopt("", "test-builder", "The rustc-like binary to use as the test builder", "PATH")
+        }),
+        unstable("check", |o| o.optflagmulti("", "check", "Run rustdoc checks")),
+        unstable("generate-redirect-map", |o| {
+            o.optflagmulti(
+                "",
+                "generate-redirect-map",
+                "Generate JSON file at the top level instead of generating HTML redirection files",
+            )
+        }),
+        unstable("emit", |o| {
+            o.optmulti(
+                "",
+                "emit",
+                "Comma separated list of types of output for rustdoc to emit",
+                "[unversioned-shared-resources,toolchain-shared-resources,invocation-specific]",
+            )
+        }),
+        unstable("no-run", |o| {
+            o.optflagmulti("", "no-run", "Compile doctests without running them")
+        }),
+        unstable("show-type-layout", |o| {
+            o.optflagmulti("", "show-type-layout", "Include the memory layout of types in the docs")
+        }),
+        unstable("nocapture", |o| {
+            o.optflag("", "nocapture", "Don't capture stdout and stderr of tests")
+        }),
+        unstable("generate-link-to-definition", |o| {
+            o.optflag(
+                "",
+                "generate-link-to-definition",
+                "Make the identifiers in the HTML source code pages navigable",
+            )
+        }),
+        unstable("scrape-examples-output-path", |o| {
+            o.optopt(
+                "",
+                "scrape-examples-output-path",
+                "",
+                "collect function call information and output at the given path",
+            )
+        }),
+        unstable("scrape-examples-target-crate", |o| {
+            o.optmulti(
+                "",
+                "scrape-examples-target-crate",
+                "",
+                "collect function call information for functions from the target crate",
+            )
+        }),
+        unstable("scrape-tests", |o| {
+            o.optflag("", "scrape-tests", "Include test code when scraping examples")
+        }),
+        unstable("with-examples", |o| {
+            o.optmulti(
+                "",
+                "with-examples",
+                "",
+                "path to function call information (for displaying examples in the documentation)",
+            )
+        }),
+        // deprecated / removed options
+        stable("plugin-path", |o| {
+            o.optmulti(
+                "",
+                "plugin-path",
+                "removed, see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+                "DIR",
+            )
+        }),
+        stable("passes", |o| {
+            o.optmulti(
+                "",
+                "passes",
+                "removed, see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+                "PASSES",
+            )
+        }),
+        stable("plugins", |o| {
+            o.optmulti(
+                "",
+                "plugins",
+                "removed, see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+                "PLUGINS",
+            )
+        }),
+        stable("no-default", |o| {
+            o.optflagmulti(
+                "",
+                "no-defaults",
+                "removed, see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+            )
+        }),
+        stable("r", |o| {
+            o.optopt(
+                "r",
+                "input-format",
+                "removed, see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
+                for more information",
+                "[rust]",
+            )
+        }),
+    ]
+}
+
+fn usage(argv0: &str) {
+    let mut options = getopts::Options::new();
+    for option in opts() {
+        (option.apply)(&mut options);
+    }
+    println!("{}", options.usage(&format!("{} [options] <input>", argv0)));
+    println!("    @path               Read newline separated options from `path`\n");
+    println!(
+        "More information available at {}/rustdoc/what-is-rustdoc.html",
+        DOC_RUST_LANG_ORG_CHANNEL
+    );
+}
+
+/// A result type used by several functions under `main()`.
+type MainResult = Result<(), ErrorGuaranteed>;
+
+fn main_args(at_args: &[String]) -> MainResult {
+    let args = rustc_driver::args::arg_expand_all(at_args);
+
+    let mut options = getopts::Options::new();
+    for option in opts() {
+        (option.apply)(&mut options);
+    }
+    let matches = match options.parse(&args[1..]) {
+        Ok(m) => m,
+        Err(err) => {
+            early_error(ErrorOutputType::default(), &err.to_string());
+        }
+    };
+
+    // Note that we discard any distinction between different non-zero exit
+    // codes from `from_matches` here.
+    let options = match config::Options::from_matches(&matches, args) {
+        Ok(opts) => opts,
+        Err(code) => {
+            return if code == 0 {
+                Ok(())
+            } else {
+                Err(ErrorGuaranteed::unchecked_claim_error_was_emitted())
+            };
+        }
+    };
+    rustc_interface::util::run_in_thread_pool_with_globals(
+        options.edition,
+        1, // this runs single-threaded, even in a parallel compiler
+        move || main_options(options),
+    )
+}
+
+fn wrap_return(diag: &rustc_errors::Handler, res: Result<(), String>) -> MainResult {
+    match res {
+        Ok(()) => Ok(()),
+        Err(err) => {
+            let reported = diag.struct_err(&err).emit();
+            Err(reported)
+        }
+    }
+}
+
+fn run_renderer<'tcx, T: formats::FormatRenderer<'tcx>>(
+    krate: clean::Crate,
+    renderopts: config::RenderOptions,
+    cache: formats::cache::Cache,
+    tcx: TyCtxt<'tcx>,
+) -> MainResult {
+    match formats::run_format::<T>(krate, renderopts, cache, tcx) {
+        Ok(_) => Ok(()),
+        Err(e) => {
+            let mut msg =
+                tcx.sess.struct_err(&format!("couldn't generate documentation: {}", e.error));
+            let file = e.file.display().to_string();
+            if !file.is_empty() {
+                msg.note(&format!("failed to create or modify \"{}\"", file));
+            }
+            Err(msg.emit())
+        }
+    }
+}
+
+fn main_options(options: config::Options) -> MainResult {
+    let diag = core::new_handler(
+        options.error_format,
+        None,
+        options.diagnostic_width,
+        &options.unstable_opts,
+    );
+
+    match (options.should_test, options.markdown_input()) {
+        (true, true) => return wrap_return(&diag, markdown::test(options)),
+        (true, false) => return doctest::run(options),
+        (false, true) => {
+            return wrap_return(
+                &diag,
+                markdown::render(&options.input, options.render_options, options.edition),
+            );
+        }
+        (false, false) => {}
+    }
+
+    // need to move these items separately because we lose them by the time the closure is called,
+    // but we can't create the Handler ahead of time because it's not Send
+    let show_coverage = options.show_coverage;
+    let run_check = options.run_check;
+
+    // First, parse the crate and extract all relevant information.
+    info!("starting to run rustc");
+
+    // Interpret the input file as a rust source file, passing it through the
+    // compiler all the way through the analysis passes. The rustdoc output is
+    // then generated from the cleaned AST of the crate. This runs all the
+    // plug/cleaning passes.
+    let crate_version = options.crate_version.clone();
+
+    let output_format = options.output_format;
+    // FIXME: fix this clone (especially render_options)
+    let externs = options.externs.clone();
+    let render_options = options.render_options.clone();
+    let scrape_examples_options = options.scrape_examples_options.clone();
+    let document_private = options.render_options.document_private;
+    let config = core::create_config(options);
+
+    interface::create_compiler_and_run(config, |compiler| {
+        let sess = compiler.session();
+
+        if sess.opts.describe_lints {
+            let mut lint_store = rustc_lint::new_lint_store(
+                sess.opts.unstable_opts.no_interleave_lints,
+                sess.enable_internal_lints(),
+            );
+            let registered_lints = if let Some(register_lints) = compiler.register_lints() {
+                register_lints(sess, &mut lint_store);
+                true
+            } else {
+                false
+            };
+            rustc_driver::describe_lints(sess, &lint_store, registered_lints);
+            return Ok(());
+        }
+
+        compiler.enter(|queries| {
+            // We need to hold on to the complete resolver, so we cause everything to be
+            // cloned for the analysis passes to use. Suboptimal, but necessary in the
+            // current architecture.
+            // FIXME(#83761): Resolver cloning can lead to inconsistencies between data in the
+            // two copies because one of the copies can be modified after `TyCtxt` construction.
+            let (resolver, resolver_caches) = {
+                let (krate, resolver, _) = &*abort_on_err(queries.expansion(), sess).peek();
+                let resolver_caches = resolver.borrow_mut().access(|resolver| {
+                    collect_intra_doc_links::early_resolve_intra_doc_links(
+                        resolver,
+                        sess,
+                        krate,
+                        externs,
+                        document_private,
+                    )
+                });
+                (resolver.clone(), resolver_caches)
+            };
+
+            if sess.diagnostic().has_errors_or_lint_errors().is_some() {
+                sess.fatal("Compilation failed, aborting rustdoc");
+            }
+
+            let mut global_ctxt = abort_on_err(queries.global_ctxt(), sess).peek_mut();
+
+            global_ctxt.enter(|tcx| {
+                let (krate, render_opts, mut cache) = sess.time("run_global_ctxt", || {
+                    core::run_global_ctxt(
+                        tcx,
+                        resolver,
+                        resolver_caches,
+                        show_coverage,
+                        render_options,
+                        output_format,
+                    )
+                });
+                info!("finished with rustc");
+
+                if let Some(options) = scrape_examples_options {
+                    return scrape_examples::run(krate, render_opts, cache, tcx, options);
+                }
+
+                cache.crate_version = crate_version;
+
+                if show_coverage {
+                    // if we ran coverage, bail early, we don't need to also generate docs at this point
+                    // (also we didn't load in any of the useful passes)
+                    return Ok(());
+                } else if run_check {
+                    // Since we're in "check" mode, no need to generate anything beyond this point.
+                    return Ok(());
+                }
+
+                info!("going to format");
+                match output_format {
+                    config::OutputFormat::Html => sess.time("render_html", || {
+                        run_renderer::<html::render::Context<'_>>(krate, render_opts, cache, tcx)
+                    }),
+                    config::OutputFormat::Json => sess.time("render_json", || {
+                        run_renderer::<json::JsonRenderer<'_>>(krate, render_opts, cache, tcx)
+                    }),
+                }
+            })
+        })
+    })
+}
diff --git a/src/librustdoc/lint.rs b/src/librustdoc/lint.rs
new file mode 100644
index 000000000..240aec52c
--- /dev/null
+++ b/src/librustdoc/lint.rs
@@ -0,0 +1,202 @@
+use rustc_data_structures::fx::FxHashMap;
+use rustc_lint::LintStore;
+use rustc_lint_defs::{declare_tool_lint, Lint, LintId};
+use rustc_session::{lint, Session};
+
+use std::sync::LazyLock as Lazy;
+
+/// This function is used to setup the lint initialization. By default, in rustdoc, everything
+/// is "allowed". Depending if we run in test mode or not, we want some of them to be at their
+/// default level. For example, the "INVALID_CODEBLOCK_ATTRIBUTES" lint is activated in both
+/// modes.
+///
+/// A little detail easy to forget is that there is a way to set the lint level for all lints
+/// through the "WARNINGS" lint. To prevent this to happen, we set it back to its "normal" level
+/// inside this function.
+///
+/// It returns a tuple containing:
+///  * Vector of tuples of lints' name and their associated "max" level
+///  * HashMap of lint id with their associated "max" level
+pub(crate) fn init_lints<F>(
+    mut allowed_lints: Vec<String>,
+    lint_opts: Vec<(String, lint::Level)>,
+    filter_call: F,
+) -> (Vec<(String, lint::Level)>, FxHashMap<lint::LintId, lint::Level>)
+where
+    F: Fn(&lint::Lint) -> Option<(String, lint::Level)>,
+{
+    let warnings_lint_name = lint::builtin::WARNINGS.name;
+
+    allowed_lints.push(warnings_lint_name.to_owned());
+    allowed_lints.extend(lint_opts.iter().map(|(lint, _)| lint).cloned());
+
+    let lints = || {
+        lint::builtin::HardwiredLints::get_lints()
+            .into_iter()
+            .chain(rustc_lint::SoftLints::get_lints().into_iter())
+    };
+
+    let lint_opts = lints()
+        .filter_map(|lint| {
+            // Permit feature-gated lints to avoid feature errors when trying to
+            // allow all lints.
+            if lint.feature_gate.is_some() || allowed_lints.iter().any(|l| lint.name == l) {
+                None
+            } else {
+                filter_call(lint)
+            }
+        })
+        .chain(lint_opts.into_iter())
+        .collect::<Vec<_>>();
+
+    let lint_caps = lints()
+        .filter_map(|lint| {
+            // We don't want to allow *all* lints so let's ignore
+            // those ones.
+            if allowed_lints.iter().any(|l| lint.name == l) {
+                None
+            } else {
+                Some((lint::LintId::of(lint), lint::Allow))
+            }
+        })
+        .collect();
+    (lint_opts, lint_caps)
+}
+
+macro_rules! declare_rustdoc_lint {
+    ($(#[$attr:meta])* $name: ident, $level: ident, $descr: literal $(,)?) => {
+        declare_tool_lint! {
+            $(#[$attr])* pub rustdoc::$name, $level, $descr
+        }
+    }
+}
+
+declare_rustdoc_lint! {
+    /// The `broken_intra_doc_links` lint detects failures in resolving
+    /// intra-doc link targets. This is a `rustdoc` only lint, see the
+    /// documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#broken_intra_doc_links
+    BROKEN_INTRA_DOC_LINKS,
+    Warn,
+    "failures in resolving intra-doc link targets"
+}
+
+declare_rustdoc_lint! {
+    /// This is a subset of `broken_intra_doc_links` that warns when linking from
+    /// a public item to a private one. This is a `rustdoc` only lint, see the
+    /// documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#private_intra_doc_links
+    PRIVATE_INTRA_DOC_LINKS,
+    Warn,
+    "linking from a public item to a private one"
+}
+
+declare_rustdoc_lint! {
+    /// The `invalid_codeblock_attributes` lint detects code block attributes
+    /// in documentation examples that have potentially mis-typed values. This
+    /// is a `rustdoc` only lint, see the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_codeblock_attributes
+    INVALID_CODEBLOCK_ATTRIBUTES,
+    Warn,
+    "codeblock attribute looks a lot like a known one"
+}
+
+declare_rustdoc_lint! {
+    /// The `missing_crate_level_docs` lint detects if documentation is
+    /// missing at the crate root. This is a `rustdoc` only lint, see the
+    /// documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#missing_crate_level_docs
+    MISSING_CRATE_LEVEL_DOCS,
+    Allow,
+    "detects crates with no crate-level documentation"
+}
+
+declare_rustdoc_lint! {
+    /// The `missing_doc_code_examples` lint detects publicly-exported items
+    /// without code samples in their documentation. This is a `rustdoc` only
+    /// lint, see the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#missing_doc_code_examples
+    MISSING_DOC_CODE_EXAMPLES,
+    Allow,
+    "detects publicly-exported items without code samples in their documentation"
+}
+
+declare_rustdoc_lint! {
+    /// The `private_doc_tests` lint detects code samples in docs of private
+    /// items not documented by `rustdoc`. This is a `rustdoc` only lint, see
+    /// the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#private_doc_tests
+    PRIVATE_DOC_TESTS,
+    Allow,
+    "detects code samples in docs of private items not documented by rustdoc"
+}
+
+declare_rustdoc_lint! {
+    /// The `invalid_html_tags` lint detects invalid HTML tags. This is a
+    /// `rustdoc` only lint, see the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_html_tags
+    INVALID_HTML_TAGS,
+    Allow,
+    "detects invalid HTML tags in doc comments"
+}
+
+declare_rustdoc_lint! {
+    /// The `bare_urls` lint detects when a URL is not a hyperlink.
+    /// This is a `rustdoc` only lint, see the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#bare_urls
+    BARE_URLS,
+    Warn,
+    "detects URLs that are not hyperlinks"
+}
+
+declare_rustdoc_lint! {
+   /// The `invalid_rust_codeblocks` lint detects Rust code blocks in
+   /// documentation examples that are invalid (e.g. empty, not parsable as
+   /// Rust code). This is a `rustdoc` only lint, see the documentation in the
+   /// [rustdoc book].
+   ///
+   /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_rust_codeblocks
+   INVALID_RUST_CODEBLOCKS,
+   Warn,
+   "codeblock could not be parsed as valid Rust or is empty"
+}
+
+pub(crate) static RUSTDOC_LINTS: Lazy<Vec<&'static Lint>> = Lazy::new(|| {
+    vec![
+        BROKEN_INTRA_DOC_LINKS,
+        PRIVATE_INTRA_DOC_LINKS,
+        MISSING_DOC_CODE_EXAMPLES,
+        PRIVATE_DOC_TESTS,
+        INVALID_CODEBLOCK_ATTRIBUTES,
+        INVALID_RUST_CODEBLOCKS,
+        INVALID_HTML_TAGS,
+        BARE_URLS,
+        MISSING_CRATE_LEVEL_DOCS,
+    ]
+});
+
+pub(crate) fn register_lints(_sess: &Session, lint_store: &mut LintStore) {
+    lint_store.register_lints(&**RUSTDOC_LINTS);
+    lint_store.register_group(
+        true,
+        "rustdoc::all",
+        Some("rustdoc"),
+        RUSTDOC_LINTS.iter().map(|&lint| LintId::of(lint)).collect(),
+    );
+    for lint in &*RUSTDOC_LINTS {
+        let name = lint.name_lower();
+        lint_store.register_renamed(&name.replace("rustdoc::", ""), &name);
+    }
+    lint_store
+        .register_renamed("intra_doc_link_resolution_failure", "rustdoc::broken_intra_doc_links");
+    lint_store.register_renamed("non_autolinks", "rustdoc::bare_urls");
+    lint_store.register_renamed("rustdoc::non_autolinks", "rustdoc::bare_urls");
+}
diff --git a/src/librustdoc/markdown.rs b/src/librustdoc/markdown.rs
new file mode 100644
index 000000000..0b557ef24
--- /dev/null
+++ b/src/librustdoc/markdown.rs
@@ -0,0 +1,151 @@
+use std::fmt::Write as _;
+use std::fs::{create_dir_all, read_to_string, File};
+use std::io::prelude::*;
+use std::path::Path;
+
+use rustc_span::edition::Edition;
+use rustc_span::source_map::DUMMY_SP;
+use rustc_span::Symbol;
+
+use crate::config::{Options, RenderOptions};
+use crate::doctest::{Collector, GlobalTestOptions};
+use crate::html::escape::Escape;
+use crate::html::markdown;
+use crate::html::markdown::{
+    find_testable_code, ErrorCodes, HeadingOffset, IdMap, Markdown, MarkdownWithToc,
+};
+
+/// Separate any lines at the start of the file that begin with `# ` or `%`.
+fn extract_leading_metadata(s: &str) -> (Vec<&str>, &str) {
+    let mut metadata = Vec::new();
+    let mut count = 0;
+
+    for line in s.lines() {
+        if line.starts_with("# ") || line.starts_with('%') {
+            // trim the whitespace after the symbol
+            metadata.push(line[1..].trim_start());
+            count += line.len() + 1;
+        } else {
+            return (metadata, &s[count..]);
+        }
+    }
+
+    // if we're here, then all lines were metadata `# ` or `%` lines.
+    (metadata, "")
+}
+
+/// Render `input` (e.g., "foo.md") into an HTML file in `output`
+/// (e.g., output = "bar" => "bar/foo.html").
+pub(crate) fn render<P: AsRef<Path>>(
+    input: P,
+    options: RenderOptions,
+    edition: Edition,
+) -> Result<(), String> {
+    if let Err(e) = create_dir_all(&options.output) {
+        return Err(format!("{}: {}", options.output.display(), e));
+    }
+
+    let input = input.as_ref();
+    let mut output = options.output;
+    output.push(input.file_name().unwrap());
+    output.set_extension("html");
+
+    let mut css = String::new();
+    for name in &options.markdown_css {
+        write!(css, r#"<link rel="stylesheet" type="text/css" href="{name}">"#)
+            .expect("Writing to a String can't fail");
+    }
+
+    let input_str = read_to_string(input).map_err(|err| format!("{}: {}", input.display(), err))?;
+    let playground_url = options.markdown_playground_url.or(options.playground_url);
+    let playground = playground_url.map(|url| markdown::Playground { crate_name: None, url });
+
+    let mut out = File::create(&output).map_err(|e| format!("{}: {}", output.display(), e))?;
+
+    let (metadata, text) = extract_leading_metadata(&input_str);
+    if metadata.is_empty() {
+        return Err("invalid markdown file: no initial lines starting with `# ` or `%`".to_owned());
+    }
+    let title = metadata[0];
+
+    let mut ids = IdMap::new();
+    let error_codes = ErrorCodes::from(options.unstable_features.is_nightly_build());
+    let text = if !options.markdown_no_toc {
+        MarkdownWithToc(text, &mut ids, error_codes, edition, &playground).into_string()
+    } else {
+        Markdown {
+            content: text,
+            links: &[],
+            ids: &mut ids,
+            error_codes,
+            edition,
+            playground: &playground,
+            heading_offset: HeadingOffset::H1,
+        }
+        .into_string()
+    };
+
+    let err = write!(
+        &mut out,
+        r#"<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="generator" content="rustdoc">
+    <title>{title}</title>
+
+    {css}
+    {in_header}
+</head>
+<body class="rustdoc">
+    <!--[if lte IE 8]>
+    <div class="warning">
+        This old browser is unsupported and will most likely display funky
+        things.
+    </div>
+    <![endif]-->
+
+    {before_content}
+    <h1 class="title">{title}</h1>
+    {text}
+    {after_content}
+</body>
+</html>"#,
+        title = Escape(title),
+        css = css,
+        in_header = options.external_html.in_header,
+        before_content = options.external_html.before_content,
+        text = text,
+        after_content = options.external_html.after_content,
+    );
+
+    match err {
+        Err(e) => Err(format!("cannot write to `{}`: {}", output.display(), e)),
+        Ok(_) => Ok(()),
+    }
+}
+
+/// Runs any tests/code examples in the markdown file `input`.
+pub(crate) fn test(options: Options) -> Result<(), String> {
+    let input_str = read_to_string(&options.input)
+        .map_err(|err| format!("{}: {}", options.input.display(), err))?;
+    let mut opts = GlobalTestOptions::default();
+    opts.no_crate_inject = true;
+    let mut collector = Collector::new(
+        Symbol::intern(&options.input.display().to_string()),
+        options.clone(),
+        true,
+        opts,
+        None,
+        Some(options.input),
+        options.enable_per_target_ignores,
+    );
+    collector.set_position(DUMMY_SP);
+    let codes = ErrorCodes::from(options.render_options.unstable_features.is_nightly_build());
+
+    find_testable_code(&input_str, &mut collector, codes, options.enable_per_target_ignores, None);
+
+    crate::doctest::run_tests(options.test_args, options.nocapture, collector.tests);
+    Ok(())
+}
diff --git a/src/librustdoc/passes/bare_urls.rs b/src/librustdoc/passes/bare_urls.rs
new file mode 100644
index 000000000..392e26ea6
--- /dev/null
+++ b/src/librustdoc/passes/bare_urls.rs
@@ -0,0 +1,112 @@
+//! Detects links that are not linkified, e.g., in Markdown such as `Go to https://example.com/.`
+//! Suggests wrapping the link with angle brackets: `Go to <https://example.com/>.` to linkify it.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
+use core::ops::Range;
+use pulldown_cmark::{Event, Parser, Tag};
+use regex::Regex;
+use rustc_errors::Applicability;
+use std::mem;
+use std::sync::LazyLock;
+
+pub(crate) const CHECK_BARE_URLS: Pass = Pass {
+    name: "check-bare-urls",
+    run: check_bare_urls,
+    description: "detects URLs that are not hyperlinks",
+};
+
+static URL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(concat!(
+        r"https?://",                          // url scheme
+        r"([-a-zA-Z0-9@:%._\+~#=]{2,256}\.)+", // one or more subdomains
+        r"[a-zA-Z]{2,63}",                     // root domain
+        r"\b([-a-zA-Z0-9@:%_\+.~#?&/=]*)"      // optional query or url fragments
+    ))
+    .expect("failed to build regex")
+});
+
+struct BareUrlsLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> BareUrlsLinter<'a, 'tcx> {
+    fn find_raw_urls(
+        &self,
+        text: &str,
+        range: Range<usize>,
+        f: &impl Fn(&DocContext<'_>, &str, &str, Range<usize>),
+    ) {
+        trace!("looking for raw urls in {}", text);
+        // For now, we only check "full" URLs (meaning, starting with "http://" or "https://").
+        for match_ in URL_REGEX.find_iter(text) {
+            let url = match_.as_str();
+            let url_range = match_.range();
+            f(
+                self.cx,
+                "this URL is not a hyperlink",
+                url,
+                Range { start: range.start + url_range.start, end: range.start + url_range.end },
+            );
+        }
+    }
+}
+
+pub(crate) fn check_bare_urls(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    BareUrlsLinter { cx }.visit_crate(&krate);
+    krate
+}
+
+impl<'a, 'tcx> DocVisitor for BareUrlsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let Some(hir_id) = DocContext::as_local_hir_id(self.cx.tcx, item.item_id)
+        else {
+            // If non-local, no need to check anything.
+            return;
+        };
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        if !dox.is_empty() {
+            let report_diag = |cx: &DocContext<'_>, msg: &str, url: &str, range: Range<usize>| {
+                let sp = super::source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)
+                    .unwrap_or_else(|| item.attr_span(cx.tcx));
+                cx.tcx.struct_span_lint_hir(crate::lint::BARE_URLS, hir_id, sp, |lint| {
+                    lint.build(msg)
+                        .note("bare URLs are not automatically turned into clickable links")
+                        .span_suggestion(
+                            sp,
+                            "use an automatic link instead",
+                            format!("<{}>", url),
+                            Applicability::MachineApplicable,
+                        )
+                        .emit();
+                });
+            };
+
+            let mut p = Parser::new_ext(&dox, main_body_opts()).into_offset_iter();
+
+            while let Some((event, range)) = p.next() {
+                match event {
+                    Event::Text(s) => self.find_raw_urls(&s, range, &report_diag),
+                    // We don't want to check the text inside code blocks or links.
+                    Event::Start(tag @ (Tag::CodeBlock(_) | Tag::Link(..))) => {
+                        while let Some((event, _)) = p.next() {
+                            match event {
+                                Event::End(end)
+                                    if mem::discriminant(&end) == mem::discriminant(&tag) =>
+                                {
+                                    break;
+                                }
+                                _ => {}
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
diff --git a/src/librustdoc/passes/calculate_doc_coverage.rs b/src/librustdoc/passes/calculate_doc_coverage.rs
new file mode 100644
index 000000000..4c6e3eb04
--- /dev/null
+++ b/src/librustdoc/passes/calculate_doc_coverage.rs
@@ -0,0 +1,276 @@
+//! Calculates information used for the --show-coverage flag.
+use crate::clean;
+use crate::core::DocContext;
+use crate::html::markdown::{find_testable_code, ErrorCodes};
+use crate::passes::check_doc_test_visibility::{should_have_doc_example, Tests};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+use rustc_hir as hir;
+use rustc_lint::builtin::MISSING_DOCS;
+use rustc_middle::lint::LintLevelSource;
+use rustc_middle::ty::DefIdTree;
+use rustc_session::lint;
+use rustc_span::FileName;
+use serde::Serialize;
+
+use std::collections::BTreeMap;
+use std::ops;
+
+pub(crate) const CALCULATE_DOC_COVERAGE: Pass = Pass {
+    name: "calculate-doc-coverage",
+    run: calculate_doc_coverage,
+    description: "counts the number of items with and without documentation",
+};
+
+fn calculate_doc_coverage(krate: clean::Crate, ctx: &mut DocContext<'_>) -> clean::Crate {
+    let mut calc = CoverageCalculator { items: Default::default(), ctx };
+    calc.visit_crate(&krate);
+
+    calc.print_results();
+
+    krate
+}
+
+#[derive(Default, Copy, Clone, Serialize, Debug)]
+struct ItemCount {
+    total: u64,
+    with_docs: u64,
+    total_examples: u64,
+    with_examples: u64,
+}
+
+impl ItemCount {
+    fn count_item(
+        &mut self,
+        has_docs: bool,
+        has_doc_example: bool,
+        should_have_doc_examples: bool,
+        should_have_docs: bool,
+    ) {
+        if has_docs || should_have_docs {
+            self.total += 1;
+        }
+
+        if has_docs {
+            self.with_docs += 1;
+        }
+        if should_have_doc_examples || has_doc_example {
+            self.total_examples += 1;
+        }
+        if has_doc_example {
+            self.with_examples += 1;
+        }
+    }
+
+    fn percentage(&self) -> Option<f64> {
+        if self.total > 0 {
+            Some((self.with_docs as f64 * 100.0) / self.total as f64)
+        } else {
+            None
+        }
+    }
+
+    fn examples_percentage(&self) -> Option<f64> {
+        if self.total_examples > 0 {
+            Some((self.with_examples as f64 * 100.0) / self.total_examples as f64)
+        } else {
+            None
+        }
+    }
+}
+
+impl ops::Sub for ItemCount {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self {
+        ItemCount {
+            total: self.total - rhs.total,
+            with_docs: self.with_docs - rhs.with_docs,
+            total_examples: self.total_examples - rhs.total_examples,
+            with_examples: self.with_examples - rhs.with_examples,
+        }
+    }
+}
+
+impl ops::AddAssign for ItemCount {
+    fn add_assign(&mut self, rhs: Self) {
+        self.total += rhs.total;
+        self.with_docs += rhs.with_docs;
+        self.total_examples += rhs.total_examples;
+        self.with_examples += rhs.with_examples;
+    }
+}
+
+struct CoverageCalculator<'a, 'b> {
+    items: BTreeMap<FileName, ItemCount>,
+    ctx: &'a mut DocContext<'b>,
+}
+
+fn limit_filename_len(filename: String) -> String {
+    let nb_chars = filename.chars().count();
+    if nb_chars > 35 {
+        "...".to_string()
+            + &filename[filename.char_indices().nth(nb_chars - 32).map(|x| x.0).unwrap_or(0)..]
+    } else {
+        filename
+    }
+}
+
+impl<'a, 'b> CoverageCalculator<'a, 'b> {
+    fn to_json(&self) -> String {
+        serde_json::to_string(
+            &self
+                .items
+                .iter()
+                .map(|(k, v)| (k.prefer_local().to_string(), v))
+                .collect::<BTreeMap<String, &ItemCount>>(),
+        )
+        .expect("failed to convert JSON data to string")
+    }
+
+    fn print_results(&self) {
+        let output_format = self.ctx.output_format;
+        if output_format.is_json() {
+            println!("{}", self.to_json());
+            return;
+        }
+        let mut total = ItemCount::default();
+
+        fn print_table_line() {
+            println!("+-{0:->35}-+-{0:->10}-+-{0:->10}-+-{0:->10}-+-{0:->10}-+", "");
+        }
+
+        fn print_table_record(
+            name: &str,
+            count: ItemCount,
+            percentage: f64,
+            examples_percentage: f64,
+        ) {
+            println!(
+                "| {:<35} | {:>10} | {:>9.1}% | {:>10} | {:>9.1}% |",
+                name, count.with_docs, percentage, count.with_examples, examples_percentage,
+            );
+        }
+
+        print_table_line();
+        println!(
+            "| {:<35} | {:>10} | {:>10} | {:>10} | {:>10} |",
+            "File", "Documented", "Percentage", "Examples", "Percentage",
+        );
+        print_table_line();
+
+        for (file, &count) in &self.items {
+            if let Some(percentage) = count.percentage() {
+                print_table_record(
+                    &limit_filename_len(file.prefer_local().to_string_lossy().into()),
+                    count,
+                    percentage,
+                    count.examples_percentage().unwrap_or(0.),
+                );
+
+                total += count;
+            }
+        }
+
+        print_table_line();
+        print_table_record(
+            "Total",
+            total,
+            total.percentage().unwrap_or(0.0),
+            total.examples_percentage().unwrap_or(0.0),
+        );
+        print_table_line();
+    }
+}
+
+impl<'a, 'b> DocVisitor for CoverageCalculator<'a, 'b> {
+    fn visit_item(&mut self, i: &clean::Item) {
+        if !i.item_id.is_local() {
+            // non-local items are skipped because they can be out of the users control,
+            // especially in the case of trait impls, which rustdoc eagerly inlines
+            return;
+        }
+
+        match *i.kind {
+            clean::StrippedItem(..) => {
+                // don't count items in stripped modules
+                return;
+            }
+            // docs on `use` and `extern crate` statements are not displayed, so they're not
+            // worth counting
+            clean::ImportItem(..) | clean::ExternCrateItem { .. } => {}
+            // Don't count trait impls, the missing-docs lint doesn't so we shouldn't either.
+            // Inherent impls *can* be documented, and those docs show up, but in most cases it
+            // doesn't make sense, as all methods on a type are in one single impl block
+            clean::ImplItem(_) => {}
+            _ => {
+                let has_docs = !i.attrs.doc_strings.is_empty();
+                let mut tests = Tests { found_tests: 0 };
+
+                find_testable_code(
+                    &i.attrs.collapsed_doc_value().unwrap_or_default(),
+                    &mut tests,
+                    ErrorCodes::No,
+                    false,
+                    None,
+                );
+
+                let filename = i.span(self.ctx.tcx).filename(self.ctx.sess());
+                let has_doc_example = tests.found_tests != 0;
+                // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+                // would presumably panic if a fake `DefIndex` were passed.
+                let hir_id = self
+                    .ctx
+                    .tcx
+                    .hir()
+                    .local_def_id_to_hir_id(i.item_id.expect_def_id().expect_local());
+                let (level, source) = self.ctx.tcx.lint_level_at_node(MISSING_DOCS, hir_id);
+
+                // In case we have:
+                //
+                // ```
+                // enum Foo { Bar(u32) }
+                // // or:
+                // struct Bar(u32);
+                // ```
+                //
+                // there is no need to require documentation on the fields of tuple variants and
+                // tuple structs.
+                let should_be_ignored = i
+                    .item_id
+                    .as_def_id()
+                    .and_then(|def_id| self.ctx.tcx.opt_parent(def_id))
+                    .and_then(|def_id| self.ctx.tcx.hir().get_if_local(def_id))
+                    .map(|node| {
+                        matches!(
+                            node,
+                            hir::Node::Variant(hir::Variant {
+                                data: hir::VariantData::Tuple(_, _),
+                                ..
+                            }) | hir::Node::Item(hir::Item {
+                                kind: hir::ItemKind::Struct(hir::VariantData::Tuple(_, _), _),
+                                ..
+                            })
+                        )
+                    })
+                    .unwrap_or(false);
+
+                // `missing_docs` is allow-by-default, so don't treat this as ignoring the item
+                // unless the user had an explicit `allow`.
+                //
+                let should_have_docs = !should_be_ignored
+                    && (level != lint::Level::Allow || matches!(source, LintLevelSource::Default));
+
+                debug!("counting {:?} {:?} in {:?}", i.type_(), i.name, filename);
+                self.items.entry(filename).or_default().count_item(
+                    has_docs,
+                    has_doc_example,
+                    should_have_doc_example(self.ctx, i),
+                    should_have_docs,
+                );
+            }
+        }
+
+        self.visit_item_recur(i)
+    }
+}
diff --git a/src/librustdoc/passes/check_code_block_syntax.rs b/src/librustdoc/passes/check_code_block_syntax.rs
new file mode 100644
index 000000000..0172ef570
--- /dev/null
+++ b/src/librustdoc/passes/check_code_block_syntax.rs
@@ -0,0 +1,205 @@
+//! Validates syntax inside Rust code blocks (\`\`\`rust).
+use rustc_data_structures::sync::{Lock, Lrc};
+use rustc_errors::{
+    emitter::Emitter, Applicability, Diagnostic, Handler, LazyFallbackBundle, LintDiagnosticBuilder,
+};
+use rustc_parse::parse_stream_from_source_str;
+use rustc_session::parse::ParseSess;
+use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId};
+use rustc_span::source_map::{FilePathMapping, SourceMap};
+use rustc_span::{FileName, InnerSpan, DUMMY_SP};
+
+use crate::clean;
+use crate::core::DocContext;
+use crate::html::markdown::{self, RustCodeBlock};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+
+pub(crate) const CHECK_CODE_BLOCK_SYNTAX: Pass = Pass {
+    name: "check-code-block-syntax",
+    run: check_code_block_syntax,
+    description: "validates syntax inside Rust code blocks",
+};
+
+pub(crate) fn check_code_block_syntax(
+    krate: clean::Crate,
+    cx: &mut DocContext<'_>,
+) -> clean::Crate {
+    SyntaxChecker { cx }.visit_crate(&krate);
+    krate
+}
+
+struct SyntaxChecker<'a, 'tcx> {
+    cx: &'a DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
+    fn check_rust_syntax(&self, item: &clean::Item, dox: &str, code_block: RustCodeBlock) {
+        let buffer = Lrc::new(Lock::new(Buffer::default()));
+        let fallback_bundle =
+            rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+        let emitter = BufferEmitter { buffer: Lrc::clone(&buffer), fallback_bundle };
+
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let handler = Handler::with_emitter(false, None, Box::new(emitter));
+        let source = dox[code_block.code].to_owned();
+        let sess = ParseSess::with_span_handler(handler, sm);
+
+        let edition = code_block.lang_string.edition.unwrap_or_else(|| self.cx.tcx.sess.edition());
+        let expn_data = ExpnData::default(
+            ExpnKind::AstPass(AstPass::TestHarness),
+            DUMMY_SP,
+            edition,
+            None,
+            None,
+        );
+        let expn_id =
+            self.cx.tcx.with_stable_hashing_context(|hcx| LocalExpnId::fresh(expn_data, hcx));
+        let span = DUMMY_SP.fresh_expansion(expn_id);
+
+        let is_empty = rustc_driver::catch_fatal_errors(|| {
+            parse_stream_from_source_str(
+                FileName::Custom(String::from("doctest")),
+                source,
+                &sess,
+                Some(span),
+            )
+            .is_empty()
+        })
+        .unwrap_or(false);
+        let buffer = buffer.borrow();
+
+        if !buffer.has_errors && !is_empty {
+            // No errors in a non-empty program.
+            return;
+        }
+
+        let Some(local_id) = item.item_id.as_def_id().and_then(|x| x.as_local())
+        else {
+            // We don't need to check the syntax for other crates so returning
+            // without doing anything should not be a problem.
+            return;
+        };
+
+        let hir_id = self.cx.tcx.hir().local_def_id_to_hir_id(local_id);
+        let empty_block = code_block.lang_string == Default::default() && code_block.is_fenced;
+        let is_ignore = code_block.lang_string.ignore != markdown::Ignore::None;
+
+        // The span and whether it is precise or not.
+        let (sp, precise_span) = match super::source_span_for_markdown_range(
+            self.cx.tcx,
+            dox,
+            &code_block.range,
+            &item.attrs,
+        ) {
+            Some(sp) => (sp, true),
+            None => (item.attr_span(self.cx.tcx), false),
+        };
+
+        // lambda that will use the lint to start a new diagnostic and add
+        // a suggestion to it when needed.
+        let diag_builder = |lint: LintDiagnosticBuilder<'_, ()>| {
+            let explanation = if is_ignore {
+                "`ignore` code blocks require valid Rust code for syntax highlighting; \
+                    mark blocks that do not contain Rust code as text"
+            } else {
+                "mark blocks that do not contain Rust code as text"
+            };
+            let msg = if buffer.has_errors {
+                "could not parse code block as Rust code"
+            } else {
+                "Rust code block is empty"
+            };
+            let mut diag = lint.build(msg);
+
+            if precise_span {
+                if is_ignore {
+                    // giving an accurate suggestion is hard because `ignore` might not have come first in the list.
+                    // just give a `help` instead.
+                    diag.span_help(
+                        sp.from_inner(InnerSpan::new(0, 3)),
+                        &format!("{}: ```text", explanation),
+                    );
+                } else if empty_block {
+                    diag.span_suggestion(
+                        sp.from_inner(InnerSpan::new(0, 3)).shrink_to_hi(),
+                        explanation,
+                        "text",
+                        Applicability::MachineApplicable,
+                    );
+                }
+            } else if empty_block || is_ignore {
+                diag.help(&format!("{}: ```text", explanation));
+            }
+
+            // FIXME(#67563): Provide more context for these errors by displaying the spans inline.
+            for message in buffer.messages.iter() {
+                diag.note(message);
+            }
+
+            diag.emit();
+        };
+
+        // Finally build and emit the completed diagnostic.
+        // All points of divergence have been handled earlier so this can be
+        // done the same way whether the span is precise or not.
+        self.cx.tcx.struct_span_lint_hir(
+            crate::lint::INVALID_RUST_CODEBLOCKS,
+            hir_id,
+            sp,
+            diag_builder,
+        );
+    }
+}
+
+impl<'a, 'tcx> DocVisitor for SyntaxChecker<'a, 'tcx> {
+    fn visit_item(&mut self, item: &clean::Item) {
+        if let Some(dox) = &item.attrs.collapsed_doc_value() {
+            let sp = item.attr_span(self.cx.tcx);
+            let extra = crate::html::markdown::ExtraInfo::new_did(
+                self.cx.tcx,
+                item.item_id.expect_def_id(),
+                sp,
+            );
+            for code_block in markdown::rust_code_blocks(dox, &extra) {
+                self.check_rust_syntax(item, dox, code_block);
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
+
+#[derive(Default)]
+struct Buffer {
+    messages: Vec<String>,
+    has_errors: bool,
+}
+
+struct BufferEmitter {
+    buffer: Lrc<Lock<Buffer>>,
+    fallback_bundle: LazyFallbackBundle,
+}
+
+impl Emitter for BufferEmitter {
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        let mut buffer = self.buffer.borrow_mut();
+        // FIXME(davidtwco): need to support translation here eventually
+        buffer.messages.push(format!("error from rustc: {}", diag.message[0].0.expect_str()));
+        if diag.is_error() {
+            buffer.has_errors = true;
+        }
+    }
+
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        None
+    }
+
+    fn fluent_bundle(&self) -> Option<&Lrc<rustc_errors::FluentBundle>> {
+        None
+    }
+
+    fn fallback_fluent_bundle(&self) -> &rustc_errors::FluentBundle {
+        &**self.fallback_bundle
+    }
+}
diff --git a/src/librustdoc/passes/check_doc_test_visibility.rs b/src/librustdoc/passes/check_doc_test_visibility.rs
new file mode 100644
index 000000000..e86f90833
--- /dev/null
+++ b/src/librustdoc/passes/check_doc_test_visibility.rs
@@ -0,0 +1,145 @@
+//! Looks for items missing (or incorrectly having) doctests.
+//!
+//! This pass is overloaded and runs two different lints.
+//!
+//! - MISSING_DOC_CODE_EXAMPLES: this lint is **UNSTABLE** and looks for public items missing doctests.
+//! - PRIVATE_DOC_TESTS: this lint is **STABLE** and looks for private items with doctests.
+
+use super::Pass;
+use crate::clean;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::{find_testable_code, ErrorCodes, Ignore, LangString};
+use crate::visit::DocVisitor;
+use crate::visit_ast::inherits_doc_hidden;
+use rustc_hir as hir;
+use rustc_middle::lint::LintLevelSource;
+use rustc_session::lint;
+use rustc_span::symbol::sym;
+
+pub(crate) const CHECK_DOC_TEST_VISIBILITY: Pass = Pass {
+    name: "check_doc_test_visibility",
+    run: check_doc_test_visibility,
+    description: "run various visibility-related lints on doctests",
+};
+
+struct DocTestVisibilityLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+pub(crate) fn check_doc_test_visibility(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let mut coll = DocTestVisibilityLinter { cx };
+    coll.visit_crate(&krate);
+    krate
+}
+
+impl<'a, 'tcx> DocVisitor for DocTestVisibilityLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+
+        look_for_tests(self.cx, &dox, item);
+
+        self.visit_item_recur(item)
+    }
+}
+
+pub(crate) struct Tests {
+    pub(crate) found_tests: usize,
+}
+
+impl crate::doctest::Tester for Tests {
+    fn add_test(&mut self, _: String, config: LangString, _: usize) {
+        if config.rust && config.ignore == Ignore::None {
+            self.found_tests += 1;
+        }
+    }
+}
+
+pub(crate) fn should_have_doc_example(cx: &DocContext<'_>, item: &clean::Item) -> bool {
+    if !cx.cache.access_levels.is_public(item.item_id.expect_def_id())
+        || matches!(
+            *item.kind,
+            clean::StructFieldItem(_)
+                | clean::VariantItem(_)
+                | clean::AssocConstItem(..)
+                | clean::AssocTypeItem(..)
+                | clean::TypedefItem(_)
+                | clean::StaticItem(_)
+                | clean::ConstantItem(_)
+                | clean::ExternCrateItem { .. }
+                | clean::ImportItem(_)
+                | clean::PrimitiveItem(_)
+                | clean::KeywordItem
+                // check for trait impl
+                | clean::ImplItem(box clean::Impl { trait_: Some(_), .. })
+        )
+    {
+        return false;
+    }
+
+    // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+    // would presumably panic if a fake `DefIndex` were passed.
+    let hir_id = cx.tcx.hir().local_def_id_to_hir_id(item.item_id.expect_def_id().expect_local());
+
+    // check if parent is trait impl
+    if let Some(parent_hir_id) = cx.tcx.hir().find_parent_node(hir_id) {
+        if let Some(parent_node) = cx.tcx.hir().find(parent_hir_id) {
+            if matches!(
+                parent_node,
+                hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }),
+                    ..
+                })
+            ) {
+                return false;
+            }
+        }
+    }
+
+    if cx.tcx.hir().attrs(hir_id).lists(sym::doc).has_word(sym::hidden)
+        || inherits_doc_hidden(cx.tcx, hir_id)
+        || cx.tcx.hir().span(hir_id).in_derive_expansion()
+    {
+        return false;
+    }
+    let (level, source) = cx.tcx.lint_level_at_node(crate::lint::MISSING_DOC_CODE_EXAMPLES, hir_id);
+    level != lint::Level::Allow || matches!(source, LintLevelSource::Default)
+}
+
+pub(crate) fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item) {
+    let Some(hir_id) = DocContext::as_local_hir_id(cx.tcx, item.item_id)
+    else {
+        // If non-local, no need to check anything.
+        return;
+    };
+
+    let mut tests = Tests { found_tests: 0 };
+
+    find_testable_code(dox, &mut tests, ErrorCodes::No, false, None);
+
+    if tests.found_tests == 0 && cx.tcx.sess.is_nightly_build() {
+        if should_have_doc_example(cx, item) {
+            debug!("reporting error for {:?} (hir_id={:?})", item, hir_id);
+            let sp = item.attr_span(cx.tcx);
+            cx.tcx.struct_span_lint_hir(
+                crate::lint::MISSING_DOC_CODE_EXAMPLES,
+                hir_id,
+                sp,
+                |lint| {
+                    lint.build("missing code example in this documentation").emit();
+                },
+            );
+        }
+    } else if tests.found_tests > 0
+        && !cx.cache.access_levels.is_exported(item.item_id.expect_def_id())
+    {
+        cx.tcx.struct_span_lint_hir(
+            crate::lint::PRIVATE_DOC_TESTS,
+            hir_id,
+            item.attr_span(cx.tcx),
+            |lint| {
+                lint.build("documentation test in private item").emit();
+            },
+        );
+    }
+}
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
new file mode 100644
index 000000000..7d7a63c53
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -0,0 +1,2161 @@
+//! This module implements [RFC 1946]: Intra-rustdoc-links
+//!
+//! [RFC 1946]: https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md
+
+use pulldown_cmark::LinkType;
+use rustc_ast::util::comments::may_have_doc_links;
+use rustc_data_structures::{
+    fx::{FxHashMap, FxHashSet},
+    intern::Interned,
+};
+use rustc_errors::{Applicability, Diagnostic};
+use rustc_hir::def::Namespace::*;
+use rustc_hir::def::{DefKind, Namespace, PerNS};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
+use rustc_hir::Mutability;
+use rustc_middle::ty::{DefIdTree, Ty, TyCtxt};
+use rustc_middle::{bug, ty};
+use rustc_resolve::ParentScope;
+use rustc_session::lint::Lint;
+use rustc_span::hygiene::MacroKind;
+use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::BytePos;
+use smallvec::{smallvec, SmallVec};
+
+use std::borrow::Cow;
+use std::mem;
+use std::ops::Range;
+
+use crate::clean::{self, utils::find_nearest_parent_module};
+use crate::clean::{Crate, Item, ItemId, ItemLink, PrimitiveType};
+use crate::core::DocContext;
+use crate::html::markdown::{markdown_links, MarkdownLink};
+use crate::lint::{BROKEN_INTRA_DOC_LINKS, PRIVATE_INTRA_DOC_LINKS};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+
+mod early;
+pub(crate) use early::early_resolve_intra_doc_links;
+
+pub(crate) const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
+    name: "collect-intra-doc-links",
+    run: collect_intra_doc_links,
+    description: "resolves intra-doc links",
+};
+
+fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let mut collector =
+        LinkCollector { cx, mod_ids: Vec::new(), visited_links: FxHashMap::default() };
+    collector.visit_crate(&krate);
+    krate
+}
+
+#[derive(Copy, Clone, Debug, Hash)]
+enum Res {
+    Def(DefKind, DefId),
+    Primitive(PrimitiveType),
+}
+
+type ResolveRes = rustc_hir::def::Res<rustc_ast::NodeId>;
+
+impl Res {
+    fn descr(self) -> &'static str {
+        match self {
+            Res::Def(kind, id) => ResolveRes::Def(kind, id).descr(),
+            Res::Primitive(_) => "builtin type",
+        }
+    }
+
+    fn article(self) -> &'static str {
+        match self {
+            Res::Def(kind, id) => ResolveRes::Def(kind, id).article(),
+            Res::Primitive(_) => "a",
+        }
+    }
+
+    fn name(self, tcx: TyCtxt<'_>) -> Symbol {
+        match self {
+            Res::Def(_, id) => tcx.item_name(id),
+            Res::Primitive(prim) => prim.as_sym(),
+        }
+    }
+
+    fn def_id(self, tcx: TyCtxt<'_>) -> DefId {
+        match self {
+            Res::Def(_, id) => id,
+            Res::Primitive(prim) => *PrimitiveType::primitive_locations(tcx).get(&prim).unwrap(),
+        }
+    }
+
+    fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Res {
+        Res::Def(tcx.def_kind(def_id), def_id)
+    }
+
+    /// Used for error reporting.
+    fn disambiguator_suggestion(self) -> Suggestion {
+        let kind = match self {
+            Res::Primitive(_) => return Suggestion::Prefix("prim"),
+            Res::Def(kind, _) => kind,
+        };
+        if kind == DefKind::Macro(MacroKind::Bang) {
+            return Suggestion::Macro;
+        } else if kind == DefKind::Fn || kind == DefKind::AssocFn {
+            return Suggestion::Function;
+        } else if kind == DefKind::Field {
+            return Suggestion::RemoveDisambiguator;
+        }
+
+        let prefix = match kind {
+            DefKind::Struct => "struct",
+            DefKind::Enum => "enum",
+            DefKind::Trait => "trait",
+            DefKind::Union => "union",
+            DefKind::Mod => "mod",
+            DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst => {
+                "const"
+            }
+            DefKind::Static(_) => "static",
+            DefKind::Macro(MacroKind::Derive) => "derive",
+            // Now handle things that don't have a specific disambiguator
+            _ => match kind
+                .ns()
+                .expect("tried to calculate a disambiguator for a def without a namespace?")
+            {
+                Namespace::TypeNS => "type",
+                Namespace::ValueNS => "value",
+                Namespace::MacroNS => "macro",
+            },
+        };
+
+        Suggestion::Prefix(prefix)
+    }
+}
+
+impl TryFrom<ResolveRes> for Res {
+    type Error = ();
+
+    fn try_from(res: ResolveRes) -> Result<Self, ()> {
+        use rustc_hir::def::Res::*;
+        match res {
+            Def(kind, id) => Ok(Res::Def(kind, id)),
+            PrimTy(prim) => Ok(Res::Primitive(PrimitiveType::from_hir(prim))),
+            // e.g. `#[derive]`
+            NonMacroAttr(..) | Err => Result::Err(()),
+            other => bug!("unrecognized res {:?}", other),
+        }
+    }
+}
+
+/// The link failed to resolve. [`resolution_failure`] should look to see if there's
+/// a more helpful error that can be given.
+#[derive(Debug)]
+struct UnresolvedPath<'a> {
+    /// Item on which the link is resolved, used for resolving `Self`.
+    item_id: ItemId,
+    /// The scope the link was resolved in.
+    module_id: DefId,
+    /// If part of the link resolved, this has the `Res`.
+    ///
+    /// In `[std::io::Error::x]`, `std::io::Error` would be a partial resolution.
+    partial_res: Option<Res>,
+    /// The remaining unresolved path segments.
+    ///
+    /// In `[std::io::Error::x]`, `x` would be unresolved.
+    unresolved: Cow<'a, str>,
+}
+
+#[derive(Debug)]
+enum ResolutionFailure<'a> {
+    /// This resolved, but with the wrong namespace.
+    WrongNamespace {
+        /// What the link resolved to.
+        res: Res,
+        /// The expected namespace for the resolution, determined from the link's disambiguator.
+        ///
+        /// E.g., for `[fn@Result]` this is [`Namespace::ValueNS`],
+        /// even though `Result`'s actual namespace is [`Namespace::TypeNS`].
+        expected_ns: Namespace,
+    },
+    NotResolved(UnresolvedPath<'a>),
+}
+
+#[derive(Clone, Copy, Debug)]
+enum MalformedGenerics {
+    /// This link has unbalanced angle brackets.
+    ///
+    /// For example, `Vec<T` should trigger this, as should `Vec<T>>`.
+    UnbalancedAngleBrackets,
+    /// The generics are not attached to a type.
+    ///
+    /// For example, `<T>` should trigger this.
+    ///
+    /// This is detected by checking if the path is empty after the generics are stripped.
+    MissingType,
+    /// The link uses fully-qualified syntax, which is currently unsupported.
+    ///
+    /// For example, `<Vec as IntoIterator>::into_iter` should trigger this.
+    ///
+    /// This is detected by checking if ` as ` (the keyword `as` with spaces around it) is inside
+    /// angle brackets.
+    HasFullyQualifiedSyntax,
+    /// The link has an invalid path separator.
+    ///
+    /// For example, `Vec:<T>:new()` should trigger this. Note that `Vec:new()` will **not**
+    /// trigger this because it has no generics and thus [`strip_generics_from_path`] will not be
+    /// called.
+    ///
+    /// Note that this will also **not** be triggered if the invalid path separator is inside angle
+    /// brackets because rustdoc mostly ignores what's inside angle brackets (except for
+    /// [`HasFullyQualifiedSyntax`](MalformedGenerics::HasFullyQualifiedSyntax)).
+    ///
+    /// This is detected by checking if there is a colon followed by a non-colon in the link.
+    InvalidPathSeparator,
+    /// The link has too many angle brackets.
+    ///
+    /// For example, `Vec<<T>>` should trigger this.
+    TooManyAngleBrackets,
+    /// The link has empty angle brackets.
+    ///
+    /// For example, `Vec<>` should trigger this.
+    EmptyAngleBrackets,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub(crate) enum UrlFragment {
+    Item(DefId),
+    UserWritten(String),
+}
+
+impl UrlFragment {
+    /// Render the fragment, including the leading `#`.
+    pub(crate) fn render(&self, s: &mut String, tcx: TyCtxt<'_>) {
+        s.push('#');
+        match self {
+            &UrlFragment::Item(def_id) => {
+                let kind = match tcx.def_kind(def_id) {
+                    DefKind::AssocFn => {
+                        if tcx.impl_defaultness(def_id).has_value() {
+                            "method."
+                        } else {
+                            "tymethod."
+                        }
+                    }
+                    DefKind::AssocConst => "associatedconstant.",
+                    DefKind::AssocTy => "associatedtype.",
+                    DefKind::Variant => "variant.",
+                    DefKind::Field => {
+                        let parent_id = tcx.parent(def_id);
+                        if tcx.def_kind(parent_id) == DefKind::Variant {
+                            s.push_str("variant.");
+                            s.push_str(tcx.item_name(parent_id).as_str());
+                            ".field."
+                        } else {
+                            "structfield."
+                        }
+                    }
+                    kind => bug!("unexpected associated item kind: {:?}", kind),
+                };
+                s.push_str(kind);
+                s.push_str(tcx.item_name(def_id).as_str());
+            }
+            UrlFragment::UserWritten(raw) => s.push_str(&raw),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+struct ResolutionInfo {
+    item_id: ItemId,
+    module_id: DefId,
+    dis: Option<Disambiguator>,
+    path_str: String,
+    extra_fragment: Option<String>,
+}
+
+#[derive(Clone)]
+struct DiagnosticInfo<'a> {
+    item: &'a Item,
+    dox: &'a str,
+    ori_link: &'a str,
+    link_range: Range<usize>,
+}
+
+struct LinkCollector<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+    /// A stack of modules used to decide what scope to resolve in.
+    ///
+    /// The last module will be used if the parent scope of the current item is
+    /// unknown.
+    mod_ids: Vec<DefId>,
+    /// Cache the resolved links so we can avoid resolving (and emitting errors for) the same link.
+    /// The link will be `None` if it could not be resolved (i.e. the error was cached).
+    visited_links: FxHashMap<ResolutionInfo, Option<(Res, Option<UrlFragment>)>>,
+}
+
+impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
+    /// Given a full link, parse it as an [enum struct variant].
+    ///
+    /// In particular, this will return an error whenever there aren't three
+    /// full path segments left in the link.
+    ///
+    /// [enum struct variant]: rustc_hir::VariantData::Struct
+    fn variant_field<'path>(
+        &self,
+        path_str: &'path str,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Result<(Res, DefId), UnresolvedPath<'path>> {
+        let tcx = self.cx.tcx;
+        let no_res = || UnresolvedPath {
+            item_id,
+            module_id,
+            partial_res: None,
+            unresolved: path_str.into(),
+        };
+
+        debug!("looking for enum variant {}", path_str);
+        let mut split = path_str.rsplitn(3, "::");
+        let variant_field_name = split
+            .next()
+            .map(|f| Symbol::intern(f))
+            .expect("fold_item should ensure link is non-empty");
+        let variant_name =
+            // we're not sure this is a variant at all, so use the full string
+            // If there's no second component, the link looks like `[path]`.
+            // So there's no partial res and we should say the whole link failed to resolve.
+            split.next().map(|f|  Symbol::intern(f)).ok_or_else(no_res)?;
+        let path = split
+            .next()
+            .map(|f| f.to_owned())
+            // If there's no third component, we saw `[a::b]` before and it failed to resolve.
+            // So there's no partial res.
+            .ok_or_else(no_res)?;
+        let ty_res = self.resolve_path(&path, TypeNS, item_id, module_id).ok_or_else(no_res)?;
+
+        match ty_res {
+            Res::Def(DefKind::Enum, did) => match tcx.type_of(did).kind() {
+                ty::Adt(def, _) if def.is_enum() => {
+                    if let Some(field) = def.all_fields().find(|f| f.name == variant_field_name) {
+                        Ok((ty_res, field.did))
+                    } else {
+                        Err(UnresolvedPath {
+                            item_id,
+                            module_id,
+                            partial_res: Some(Res::Def(DefKind::Enum, def.did())),
+                            unresolved: variant_field_name.to_string().into(),
+                        })
+                    }
+                }
+                _ => unreachable!(),
+            },
+            _ => Err(UnresolvedPath {
+                item_id,
+                module_id,
+                partial_res: Some(ty_res),
+                unresolved: variant_name.to_string().into(),
+            }),
+        }
+    }
+
+    /// Given a primitive type, try to resolve an associated item.
+    fn resolve_primitive_associated_item(
+        &self,
+        prim_ty: PrimitiveType,
+        ns: Namespace,
+        item_name: Symbol,
+    ) -> Option<(Res, DefId)> {
+        let tcx = self.cx.tcx;
+
+        prim_ty.impls(tcx).find_map(|impl_| {
+            tcx.associated_items(impl_)
+                .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, impl_)
+                .map(|item| (Res::Primitive(prim_ty), item.def_id))
+        })
+    }
+
+    fn resolve_self_ty(&self, path_str: &str, ns: Namespace, item_id: ItemId) -> Option<Res> {
+        if ns != TypeNS || path_str != "Self" {
+            return None;
+        }
+
+        let tcx = self.cx.tcx;
+        item_id
+            .as_def_id()
+            .map(|def_id| match tcx.def_kind(def_id) {
+                def_kind @ (DefKind::AssocFn
+                | DefKind::AssocConst
+                | DefKind::AssocTy
+                | DefKind::Variant
+                | DefKind::Field) => {
+                    let parent_def_id = tcx.parent(def_id);
+                    if def_kind == DefKind::Field && tcx.def_kind(parent_def_id) == DefKind::Variant
+                    {
+                        tcx.parent(parent_def_id)
+                    } else {
+                        parent_def_id
+                    }
+                }
+                _ => def_id,
+            })
+            .and_then(|self_id| match tcx.def_kind(self_id) {
+                DefKind::Impl => self.def_id_to_res(self_id),
+                def_kind => Some(Res::Def(def_kind, self_id)),
+            })
+    }
+
+    /// Convenience wrapper around `resolve_rustdoc_path`.
+    ///
+    /// This also handles resolving `true` and `false` as booleans.
+    /// NOTE: `resolve_rustdoc_path` knows only about paths, not about types.
+    /// Associated items will never be resolved by this function.
+    fn resolve_path(
+        &self,
+        path_str: &str,
+        ns: Namespace,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Option<Res> {
+        if let res @ Some(..) = self.resolve_self_ty(path_str, ns, item_id) {
+            return res;
+        }
+
+        // Resolver doesn't know about true, false, and types that aren't paths (e.g. `()`).
+        let result = self
+            .cx
+            .resolver_caches
+            .doc_link_resolutions
+            .get(&(Symbol::intern(path_str), ns, module_id))
+            .copied()
+            .unwrap_or_else(|| {
+                self.cx.enter_resolver(|resolver| {
+                    let parent_scope =
+                        ParentScope::module(resolver.expect_module(module_id), resolver);
+                    resolver.resolve_rustdoc_path(path_str, ns, parent_scope)
+                })
+            })
+            .and_then(|res| res.try_into().ok())
+            .or_else(|| resolve_primitive(path_str, ns));
+        debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
+        result
+    }
+
+    /// Resolves a string as a path within a particular namespace. Returns an
+    /// optional URL fragment in the case of variants and methods.
+    fn resolve<'path>(
+        &mut self,
+        path_str: &'path str,
+        ns: Namespace,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Result<(Res, Option<DefId>), UnresolvedPath<'path>> {
+        if let Some(res) = self.resolve_path(path_str, ns, item_id, module_id) {
+            return Ok(match res {
+                Res::Def(
+                    DefKind::AssocFn | DefKind::AssocConst | DefKind::AssocTy | DefKind::Variant,
+                    def_id,
+                ) => (Res::from_def_id(self.cx.tcx, self.cx.tcx.parent(def_id)), Some(def_id)),
+                _ => (res, None),
+            });
+        } else if ns == MacroNS {
+            return Err(UnresolvedPath {
+                item_id,
+                module_id,
+                partial_res: None,
+                unresolved: path_str.into(),
+            });
+        }
+
+        // Try looking for methods and associated items.
+        let mut split = path_str.rsplitn(2, "::");
+        // NB: `split`'s first element is always defined, even if the delimiter was not present.
+        // NB: `item_str` could be empty when resolving in the root namespace (e.g. `::std`).
+        let item_str = split.next().unwrap();
+        let item_name = Symbol::intern(item_str);
+        let path_root = split
+            .next()
+            .map(|f| f.to_owned())
+            // If there's no `::`, it's not an associated item.
+            // So we can be sure that `rustc_resolve` was accurate when it said it wasn't resolved.
+            .ok_or_else(|| {
+                debug!("found no `::`, assumming {} was correctly not in scope", item_name);
+                UnresolvedPath {
+                    item_id,
+                    module_id,
+                    partial_res: None,
+                    unresolved: item_str.into(),
+                }
+            })?;
+
+        // FIXME(#83862): this arbitrarily gives precedence to primitives over modules to support
+        // links to primitives when `#[doc(primitive)]` is present. It should give an ambiguity
+        // error instead and special case *only* modules with `#[doc(primitive)]`, not all
+        // primitives.
+        resolve_primitive(&path_root, TypeNS)
+            .or_else(|| self.resolve_path(&path_root, TypeNS, item_id, module_id))
+            .and_then(|ty_res| {
+                self.resolve_associated_item(ty_res, item_name, ns, module_id).map(Ok)
+            })
+            .unwrap_or_else(|| {
+                if ns == Namespace::ValueNS {
+                    self.variant_field(path_str, item_id, module_id)
+                } else {
+                    Err(UnresolvedPath {
+                        item_id,
+                        module_id,
+                        partial_res: None,
+                        unresolved: path_root.into(),
+                    })
+                }
+            })
+            .map(|(res, def_id)| (res, Some(def_id)))
+    }
+
+    /// Convert a DefId to a Res, where possible.
+    ///
+    /// This is used for resolving type aliases.
+    fn def_id_to_res(&self, ty_id: DefId) -> Option<Res> {
+        use PrimitiveType::*;
+        Some(match *self.cx.tcx.type_of(ty_id).kind() {
+            ty::Bool => Res::Primitive(Bool),
+            ty::Char => Res::Primitive(Char),
+            ty::Int(ity) => Res::Primitive(ity.into()),
+            ty::Uint(uty) => Res::Primitive(uty.into()),
+            ty::Float(fty) => Res::Primitive(fty.into()),
+            ty::Str => Res::Primitive(Str),
+            ty::Tuple(tys) if tys.is_empty() => Res::Primitive(Unit),
+            ty::Tuple(_) => Res::Primitive(Tuple),
+            ty::Array(..) => Res::Primitive(Array),
+            ty::Slice(_) => Res::Primitive(Slice),
+            ty::RawPtr(_) => Res::Primitive(RawPointer),
+            ty::Ref(..) => Res::Primitive(Reference),
+            ty::FnDef(..) => panic!("type alias to a function definition"),
+            ty::FnPtr(_) => Res::Primitive(Fn),
+            ty::Never => Res::Primitive(Never),
+            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did, .. }, _)), _) | ty::Foreign(did) => {
+                Res::from_def_id(self.cx.tcx, did)
+            }
+            ty::Projection(_)
+            | ty::Closure(..)
+            | ty::Generator(..)
+            | ty::GeneratorWitness(_)
+            | ty::Opaque(..)
+            | ty::Dynamic(..)
+            | ty::Param(_)
+            | ty::Bound(..)
+            | ty::Placeholder(_)
+            | ty::Infer(_)
+            | ty::Error(_) => return None,
+        })
+    }
+
+    /// Convert a PrimitiveType to a Ty, where possible.
+    ///
+    /// This is used for resolving trait impls for primitives
+    fn primitive_type_to_ty(&mut self, prim: PrimitiveType) -> Option<Ty<'tcx>> {
+        use PrimitiveType::*;
+        let tcx = self.cx.tcx;
+
+        // FIXME: Only simple types are supported here, see if we can support
+        // other types such as Tuple, Array, Slice, etc.
+        // See https://github.com/rust-lang/rust/issues/90703#issuecomment-1004263455
+        Some(tcx.mk_ty(match prim {
+            Bool => ty::Bool,
+            Str => ty::Str,
+            Char => ty::Char,
+            Never => ty::Never,
+            I8 => ty::Int(ty::IntTy::I8),
+            I16 => ty::Int(ty::IntTy::I16),
+            I32 => ty::Int(ty::IntTy::I32),
+            I64 => ty::Int(ty::IntTy::I64),
+            I128 => ty::Int(ty::IntTy::I128),
+            Isize => ty::Int(ty::IntTy::Isize),
+            F32 => ty::Float(ty::FloatTy::F32),
+            F64 => ty::Float(ty::FloatTy::F64),
+            U8 => ty::Uint(ty::UintTy::U8),
+            U16 => ty::Uint(ty::UintTy::U16),
+            U32 => ty::Uint(ty::UintTy::U32),
+            U64 => ty::Uint(ty::UintTy::U64),
+            U128 => ty::Uint(ty::UintTy::U128),
+            Usize => ty::Uint(ty::UintTy::Usize),
+            _ => return None,
+        }))
+    }
+
+    /// Resolve an associated item, returning its containing page's `Res`
+    /// and the fragment targeting the associated item on its page.
+    fn resolve_associated_item(
+        &mut self,
+        root_res: Res,
+        item_name: Symbol,
+        ns: Namespace,
+        module_id: DefId,
+    ) -> Option<(Res, DefId)> {
+        let tcx = self.cx.tcx;
+
+        match root_res {
+            Res::Primitive(prim) => {
+                self.resolve_primitive_associated_item(prim, ns, item_name).or_else(|| {
+                    self.primitive_type_to_ty(prim)
+                        .and_then(|ty| {
+                            resolve_associated_trait_item(ty, module_id, item_name, ns, self.cx)
+                        })
+                        .map(|item| (root_res, item.def_id))
+                })
+            }
+            Res::Def(DefKind::TyAlias, did) => {
+                // Resolve the link on the type the alias points to.
+                // FIXME: if the associated item is defined directly on the type alias,
+                // it will show up on its documentation page, we should link there instead.
+                let res = self.def_id_to_res(did)?;
+                self.resolve_associated_item(res, item_name, ns, module_id)
+            }
+            Res::Def(
+                def_kind @ (DefKind::Struct | DefKind::Union | DefKind::Enum | DefKind::ForeignTy),
+                did,
+            ) => {
+                debug!("looking for associated item named {} for item {:?}", item_name, did);
+                // Checks if item_name is a variant of the `SomeItem` enum
+                if ns == TypeNS && def_kind == DefKind::Enum {
+                    match tcx.type_of(did).kind() {
+                        ty::Adt(adt_def, _) => {
+                            for variant in adt_def.variants() {
+                                if variant.name == item_name {
+                                    return Some((root_res, variant.def_id));
+                                }
+                            }
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+
+                // Checks if item_name belongs to `impl SomeItem`
+                let assoc_item = tcx
+                    .inherent_impls(did)
+                    .iter()
+                    .flat_map(|&imp| {
+                        tcx.associated_items(imp).find_by_name_and_namespace(
+                            tcx,
+                            Ident::with_dummy_span(item_name),
+                            ns,
+                            imp,
+                        )
+                    })
+                    .copied()
+                    // There should only ever be one associated item that matches from any inherent impl
+                    .next()
+                    // Check if item_name belongs to `impl SomeTrait for SomeItem`
+                    // FIXME(#74563): This gives precedence to `impl SomeItem`:
+                    // Although having both would be ambiguous, use impl version for compatibility's sake.
+                    // To handle that properly resolve() would have to support
+                    // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
+                    .or_else(|| {
+                        resolve_associated_trait_item(
+                            tcx.type_of(did),
+                            module_id,
+                            item_name,
+                            ns,
+                            self.cx,
+                        )
+                    });
+
+                debug!("got associated item {:?}", assoc_item);
+
+                if let Some(item) = assoc_item {
+                    return Some((root_res, item.def_id));
+                }
+
+                if ns != Namespace::ValueNS {
+                    return None;
+                }
+                debug!("looking for fields named {} for {:?}", item_name, did);
+                // FIXME: this doesn't really belong in `associated_item` (maybe `variant_field` is better?)
+                // NOTE: it's different from variant_field because it only resolves struct fields,
+                // not variant fields (2 path segments, not 3).
+                //
+                // We need to handle struct (and union) fields in this code because
+                // syntactically their paths are identical to associated item paths:
+                // `module::Type::field` and `module::Type::Assoc`.
+                //
+                // On the other hand, variant fields can't be mistaken for associated
+                // items because they look like this: `module::Type::Variant::field`.
+                //
+                // Variants themselves don't need to be handled here, even though
+                // they also look like associated items (`module::Type::Variant`),
+                // because they are real Rust syntax (unlike the intra-doc links
+                // field syntax) and are handled by the compiler's resolver.
+                let def = match tcx.type_of(did).kind() {
+                    ty::Adt(def, _) if !def.is_enum() => def,
+                    _ => return None,
+                };
+                let field =
+                    def.non_enum_variant().fields.iter().find(|item| item.name == item_name)?;
+                Some((root_res, field.did))
+            }
+            Res::Def(DefKind::Trait, did) => tcx
+                .associated_items(did)
+                .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, did)
+                .map(|item| {
+                    let res = Res::Def(item.kind.as_def_kind(), item.def_id);
+                    (res, item.def_id)
+                }),
+            _ => None,
+        }
+    }
+}
+
+fn full_res(tcx: TyCtxt<'_>, (base, assoc_item): (Res, Option<DefId>)) -> Res {
+    assoc_item.map_or(base, |def_id| Res::from_def_id(tcx, def_id))
+}
+
+/// Look to see if a resolved item has an associated item named `item_name`.
+///
+/// Given `[std::io::Error::source]`, where `source` is unresolved, this would
+/// find `std::error::Error::source` and return
+/// `<io::Error as error::Error>::source`.
+fn resolve_associated_trait_item<'a>(
+    ty: Ty<'a>,
+    module: DefId,
+    item_name: Symbol,
+    ns: Namespace,
+    cx: &mut DocContext<'a>,
+) -> Option<ty::AssocItem> {
+    // FIXME: this should also consider blanket impls (`impl<T> X for T`). Unfortunately
+    // `get_auto_trait_and_blanket_impls` is broken because the caching behavior is wrong. In the
+    // meantime, just don't look for these blanket impls.
+
+    // Next consider explicit impls: `impl MyTrait for MyType`
+    // Give precedence to inherent impls.
+    let traits = trait_impls_for(cx, ty, module);
+    debug!("considering traits {:?}", traits);
+    let mut candidates = traits.iter().filter_map(|&(impl_, trait_)| {
+        cx.tcx
+            .associated_items(trait_)
+            .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, trait_)
+            .map(|trait_assoc| {
+                trait_assoc_to_impl_assoc_item(cx.tcx, impl_, trait_assoc.def_id)
+                    .unwrap_or(trait_assoc)
+            })
+    });
+    // FIXME(#74563): warn about ambiguity
+    debug!("the candidates were {:?}", candidates.clone().collect::<Vec<_>>());
+    candidates.next().copied()
+}
+
+/// Find the associated item in the impl `impl_id` that corresponds to the
+/// trait associated item `trait_assoc_id`.
+///
+/// This function returns `None` if no associated item was found in the impl.
+/// This can occur when the trait associated item has a default value that is
+/// not overridden in the impl.
+///
+/// This is just a wrapper around [`TyCtxt::impl_item_implementor_ids()`] and
+/// [`TyCtxt::associated_item()`] (with some helpful logging added).
+#[instrument(level = "debug", skip(tcx))]
+fn trait_assoc_to_impl_assoc_item<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    impl_id: DefId,
+    trait_assoc_id: DefId,
+) -> Option<&'tcx ty::AssocItem> {
+    let trait_to_impl_assoc_map = tcx.impl_item_implementor_ids(impl_id);
+    debug!(?trait_to_impl_assoc_map);
+    let impl_assoc_id = *trait_to_impl_assoc_map.get(&trait_assoc_id)?;
+    debug!(?impl_assoc_id);
+    let impl_assoc = tcx.associated_item(impl_assoc_id);
+    debug!(?impl_assoc);
+    Some(impl_assoc)
+}
+
+/// Given a type, return all trait impls in scope in `module` for that type.
+/// Returns a set of pairs of `(impl_id, trait_id)`.
+///
+/// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
+/// So it is not stable to serialize cross-crate.
+#[instrument(level = "debug", skip(cx))]
+fn trait_impls_for<'a>(
+    cx: &mut DocContext<'a>,
+    ty: Ty<'a>,
+    module: DefId,
+) -> FxHashSet<(DefId, DefId)> {
+    let tcx = cx.tcx;
+    let iter = cx.resolver_caches.traits_in_scope[&module].iter().flat_map(|trait_candidate| {
+        let trait_ = trait_candidate.def_id;
+        trace!("considering explicit impl for trait {:?}", trait_);
+
+        // Look at each trait implementation to see if it's an impl for `did`
+        tcx.find_map_relevant_impl(trait_, ty, |impl_| {
+            let trait_ref = tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
+            // Check if these are the same type.
+            let impl_type = trait_ref.self_ty();
+            trace!(
+                "comparing type {} with kind {:?} against type {:?}",
+                impl_type,
+                impl_type.kind(),
+                ty
+            );
+            // Fast path: if this is a primitive simple `==` will work
+            // NOTE: the `match` is necessary; see #92662.
+            // this allows us to ignore generics because the user input
+            // may not include the generic placeholders
+            // e.g. this allows us to match Foo (user comment) with Foo<T> (actual type)
+            let saw_impl = impl_type == ty
+                || match (impl_type.kind(), ty.kind()) {
+                    (ty::Adt(impl_def, _), ty::Adt(ty_def, _)) => {
+                        debug!("impl def_id: {:?}, ty def_id: {:?}", impl_def.did(), ty_def.did());
+                        impl_def.did() == ty_def.did()
+                    }
+                    _ => false,
+                };
+
+            if saw_impl { Some((impl_, trait_)) } else { None }
+        })
+    });
+    iter.collect()
+}
+
+/// Check for resolve collisions between a trait and its derive.
+///
+/// These are common and we should just resolve to the trait in that case.
+fn is_derive_trait_collision<T>(ns: &PerNS<Result<(Res, T), ResolutionFailure<'_>>>) -> bool {
+    matches!(
+        *ns,
+        PerNS {
+            type_ns: Ok((Res::Def(DefKind::Trait, _), _)),
+            macro_ns: Ok((Res::Def(DefKind::Macro(MacroKind::Derive), _), _)),
+            ..
+        }
+    )
+}
+
+impl<'a, 'tcx> DocVisitor for LinkCollector<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let parent_node =
+            item.item_id.as_def_id().and_then(|did| find_nearest_parent_module(self.cx.tcx, did));
+        if parent_node.is_some() {
+            trace!("got parent node for {:?} {:?}, id {:?}", item.type_(), item.name, item.item_id);
+        }
+
+        let inner_docs = item.inner_docs(self.cx.tcx);
+
+        if item.is_mod() && inner_docs {
+            self.mod_ids.push(item.item_id.expect_def_id());
+        }
+
+        // We want to resolve in the lexical scope of the documentation.
+        // In the presence of re-exports, this is not the same as the module of the item.
+        // Rather than merging all documentation into one, resolve it one attribute at a time
+        // so we know which module it came from.
+        for (parent_module, doc) in item.attrs.prepare_to_doc_link_resolution() {
+            if !may_have_doc_links(&doc) {
+                continue;
+            }
+            debug!("combined_docs={}", doc);
+            // NOTE: if there are links that start in one crate and end in another, this will not resolve them.
+            // This is a degenerate case and it's not supported by rustdoc.
+            let parent_node = parent_module.or(parent_node);
+            let mut tmp_links = self
+                .cx
+                .resolver_caches
+                .markdown_links
+                .take()
+                .expect("`markdown_links` are already borrowed");
+            if !tmp_links.contains_key(&doc) {
+                tmp_links.insert(doc.clone(), preprocessed_markdown_links(&doc));
+            }
+            for md_link in &tmp_links[&doc] {
+                let link = self.resolve_link(item, &doc, parent_node, md_link);
+                if let Some(link) = link {
+                    self.cx.cache.intra_doc_links.entry(item.item_id).or_default().push(link);
+                }
+            }
+            self.cx.resolver_caches.markdown_links = Some(tmp_links);
+        }
+
+        if item.is_mod() {
+            if !inner_docs {
+                self.mod_ids.push(item.item_id.expect_def_id());
+            }
+
+            self.visit_item_recur(item);
+            self.mod_ids.pop();
+        } else {
+            self.visit_item_recur(item)
+        }
+    }
+}
+
+enum PreprocessingError {
+    /// User error: `[std#x#y]` is not valid
+    MultipleAnchors,
+    Disambiguator(Range<usize>, String),
+    MalformedGenerics(MalformedGenerics, String),
+}
+
+impl PreprocessingError {
+    fn report(&self, cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>) {
+        match self {
+            PreprocessingError::MultipleAnchors => report_multiple_anchors(cx, diag_info),
+            PreprocessingError::Disambiguator(range, msg) => {
+                disambiguator_error(cx, diag_info, range.clone(), msg)
+            }
+            PreprocessingError::MalformedGenerics(err, path_str) => {
+                report_malformed_generics(cx, diag_info, *err, path_str)
+            }
+        }
+    }
+}
+
+#[derive(Clone)]
+struct PreprocessingInfo {
+    path_str: String,
+    disambiguator: Option<Disambiguator>,
+    extra_fragment: Option<String>,
+    link_text: String,
+}
+
+// Not a typedef to avoid leaking several private structures from this module.
+pub(crate) struct PreprocessedMarkdownLink(
+    Result<PreprocessingInfo, PreprocessingError>,
+    MarkdownLink,
+);
+
+/// Returns:
+/// - `None` if the link should be ignored.
+/// - `Some(Err)` if the link should emit an error
+/// - `Some(Ok)` if the link is valid
+///
+/// `link_buffer` is needed for lifetime reasons; it will always be overwritten and the contents ignored.
+fn preprocess_link(
+    ori_link: &MarkdownLink,
+) -> Option<Result<PreprocessingInfo, PreprocessingError>> {
+    // [] is mostly likely not supposed to be a link
+    if ori_link.link.is_empty() {
+        return None;
+    }
+
+    // Bail early for real links.
+    if ori_link.link.contains('/') {
+        return None;
+    }
+
+    let stripped = ori_link.link.replace('`', "");
+    let mut parts = stripped.split('#');
+
+    let link = parts.next().unwrap();
+    if link.trim().is_empty() {
+        // This is an anchor to an element of the current page, nothing to do in here!
+        return None;
+    }
+    let extra_fragment = parts.next();
+    if parts.next().is_some() {
+        // A valid link can't have multiple #'s
+        return Some(Err(PreprocessingError::MultipleAnchors));
+    }
+
+    // Parse and strip the disambiguator from the link, if present.
+    let (disambiguator, path_str, link_text) = match Disambiguator::from_str(link) {
+        Ok(Some((d, path, link_text))) => (Some(d), path.trim(), link_text.trim()),
+        Ok(None) => (None, link.trim(), link.trim()),
+        Err((err_msg, relative_range)) => {
+            // Only report error if we would not have ignored this link. See issue #83859.
+            if !should_ignore_link_with_disambiguators(link) {
+                let no_backticks_range = range_between_backticks(ori_link);
+                let disambiguator_range = (no_backticks_range.start + relative_range.start)
+                    ..(no_backticks_range.start + relative_range.end);
+                return Some(Err(PreprocessingError::Disambiguator(disambiguator_range, err_msg)));
+            } else {
+                return None;
+            }
+        }
+    };
+
+    if should_ignore_link(path_str) {
+        return None;
+    }
+
+    // Strip generics from the path.
+    let path_str = if path_str.contains(['<', '>'].as_slice()) {
+        match strip_generics_from_path(path_str) {
+            Ok(path) => path,
+            Err(err) => {
+                debug!("link has malformed generics: {}", path_str);
+                return Some(Err(PreprocessingError::MalformedGenerics(err, path_str.to_owned())));
+            }
+        }
+    } else {
+        path_str.to_owned()
+    };
+
+    // Sanity check to make sure we don't have any angle brackets after stripping generics.
+    assert!(!path_str.contains(['<', '>'].as_slice()));
+
+    // The link is not an intra-doc link if it still contains spaces after stripping generics.
+    if path_str.contains(' ') {
+        return None;
+    }
+
+    Some(Ok(PreprocessingInfo {
+        path_str,
+        disambiguator,
+        extra_fragment: extra_fragment.map(|frag| frag.to_owned()),
+        link_text: link_text.to_owned(),
+    }))
+}
+
+fn preprocessed_markdown_links(s: &str) -> Vec<PreprocessedMarkdownLink> {
+    markdown_links(s, |link| {
+        preprocess_link(&link).map(|pp_link| PreprocessedMarkdownLink(pp_link, link))
+    })
+}
+
+impl LinkCollector<'_, '_> {
+    /// This is the entry point for resolving an intra-doc link.
+    ///
+    /// FIXME(jynelson): this is way too many arguments
+    fn resolve_link(
+        &mut self,
+        item: &Item,
+        dox: &str,
+        parent_node: Option<DefId>,
+        link: &PreprocessedMarkdownLink,
+    ) -> Option<ItemLink> {
+        let PreprocessedMarkdownLink(pp_link, ori_link) = link;
+        trace!("considering link '{}'", ori_link.link);
+
+        let diag_info = DiagnosticInfo {
+            item,
+            dox,
+            ori_link: &ori_link.link,
+            link_range: ori_link.range.clone(),
+        };
+
+        let PreprocessingInfo { path_str, disambiguator, extra_fragment, link_text } =
+            pp_link.as_ref().map_err(|err| err.report(self.cx, diag_info.clone())).ok()?;
+        let disambiguator = *disambiguator;
+
+        // In order to correctly resolve intra-doc links we need to
+        // pick a base AST node to work from.  If the documentation for
+        // this module came from an inner comment (//!) then we anchor
+        // our name resolution *inside* the module.  If, on the other
+        // hand it was an outer comment (///) then we anchor the name
+        // resolution in the parent module on the basis that the names
+        // used are more likely to be intended to be parent names.  For
+        // this, we set base_node to None for inner comments since
+        // we've already pushed this node onto the resolution stack but
+        // for outer comments we explicitly try and resolve against the
+        // parent_node first.
+        let inner_docs = item.inner_docs(self.cx.tcx);
+        let base_node =
+            if item.is_mod() && inner_docs { self.mod_ids.last().copied() } else { parent_node };
+        let module_id = base_node.expect("doc link without parent module");
+
+        let (mut res, fragment) = self.resolve_with_disambiguator_cached(
+            ResolutionInfo {
+                item_id: item.item_id,
+                module_id,
+                dis: disambiguator,
+                path_str: path_str.to_owned(),
+                extra_fragment: extra_fragment.clone(),
+            },
+            diag_info.clone(), // this struct should really be Copy, but Range is not :(
+            // For reference-style links we want to report only one error so unsuccessful
+            // resolutions are cached, for other links we want to report an error every
+            // time so they are not cached.
+            matches!(ori_link.kind, LinkType::Reference | LinkType::Shortcut),
+        )?;
+
+        // Check for a primitive which might conflict with a module
+        // Report the ambiguity and require that the user specify which one they meant.
+        // FIXME: could there ever be a primitive not in the type namespace?
+        if matches!(
+            disambiguator,
+            None | Some(Disambiguator::Namespace(Namespace::TypeNS) | Disambiguator::Primitive)
+        ) && !matches!(res, Res::Primitive(_))
+        {
+            if let Some(prim) = resolve_primitive(path_str, TypeNS) {
+                // `prim@char`
+                if matches!(disambiguator, Some(Disambiguator::Primitive)) {
+                    res = prim;
+                } else {
+                    // `[char]` when a `char` module is in scope
+                    let candidates = vec![res, prim];
+                    ambiguity_error(self.cx, diag_info, path_str, candidates);
+                    return None;
+                }
+            }
+        }
+
+        match res {
+            Res::Primitive(prim) => {
+                if let Some(UrlFragment::Item(id)) = fragment {
+                    // We're actually resolving an associated item of a primitive, so we need to
+                    // verify the disambiguator (if any) matches the type of the associated item.
+                    // This case should really follow the same flow as the `Res::Def` branch below,
+                    // but attempting to add a call to `clean::register_res` causes an ICE. @jyn514
+                    // thinks `register_res` is only needed for cross-crate re-exports, but Rust
+                    // doesn't allow statements like `use str::trim;`, making this a (hopefully)
+                    // valid omission. See https://github.com/rust-lang/rust/pull/80660#discussion_r551585677
+                    // for discussion on the matter.
+                    let kind = self.cx.tcx.def_kind(id);
+                    self.verify_disambiguator(
+                        path_str,
+                        ori_link,
+                        kind,
+                        id,
+                        disambiguator,
+                        item,
+                        &diag_info,
+                    )?;
+
+                    // FIXME: it would be nice to check that the feature gate was enabled in the original crate, not just ignore it altogether.
+                    // However I'm not sure how to check that across crates.
+                    if prim == PrimitiveType::RawPointer
+                        && item.item_id.is_local()
+                        && !self.cx.tcx.features().intra_doc_pointers
+                    {
+                        self.report_rawptr_assoc_feature_gate(dox, ori_link, item);
+                    }
+                } else {
+                    match disambiguator {
+                        Some(Disambiguator::Primitive | Disambiguator::Namespace(_)) | None => {}
+                        Some(other) => {
+                            self.report_disambiguator_mismatch(
+                                path_str, ori_link, other, res, &diag_info,
+                            );
+                            return None;
+                        }
+                    }
+                }
+
+                Some(ItemLink {
+                    link: ori_link.link.clone(),
+                    link_text: link_text.clone(),
+                    did: res.def_id(self.cx.tcx),
+                    fragment,
+                })
+            }
+            Res::Def(kind, id) => {
+                let (kind_for_dis, id_for_dis) = if let Some(UrlFragment::Item(id)) = fragment {
+                    (self.cx.tcx.def_kind(id), id)
+                } else {
+                    (kind, id)
+                };
+                self.verify_disambiguator(
+                    path_str,
+                    ori_link,
+                    kind_for_dis,
+                    id_for_dis,
+                    disambiguator,
+                    item,
+                    &diag_info,
+                )?;
+                let id = clean::register_res(self.cx, rustc_hir::def::Res::Def(kind, id));
+                Some(ItemLink {
+                    link: ori_link.link.clone(),
+                    link_text: link_text.clone(),
+                    did: id,
+                    fragment,
+                })
+            }
+        }
+    }
+
+    fn verify_disambiguator(
+        &self,
+        path_str: &str,
+        ori_link: &MarkdownLink,
+        kind: DefKind,
+        id: DefId,
+        disambiguator: Option<Disambiguator>,
+        item: &Item,
+        diag_info: &DiagnosticInfo<'_>,
+    ) -> Option<()> {
+        debug!("intra-doc link to {} resolved to {:?}", path_str, (kind, id));
+
+        // Disallow e.g. linking to enums with `struct@`
+        debug!("saw kind {:?} with disambiguator {:?}", kind, disambiguator);
+        match (kind, disambiguator) {
+                | (DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst, Some(Disambiguator::Kind(DefKind::Const)))
+                // NOTE: this allows 'method' to mean both normal functions and associated functions
+                // This can't cause ambiguity because both are in the same namespace.
+                | (DefKind::Fn | DefKind::AssocFn, Some(Disambiguator::Kind(DefKind::Fn)))
+                // These are namespaces; allow anything in the namespace to match
+                | (_, Some(Disambiguator::Namespace(_)))
+                // If no disambiguator given, allow anything
+                | (_, None)
+                // All of these are valid, so do nothing
+                => {}
+                (actual, Some(Disambiguator::Kind(expected))) if actual == expected => {}
+                (_, Some(specified @ Disambiguator::Kind(_) | specified @ Disambiguator::Primitive)) => {
+                    self.report_disambiguator_mismatch(path_str,ori_link,specified, Res::Def(kind, id),diag_info);
+                    return None;
+                }
+            }
+
+        // item can be non-local e.g. when using #[doc(primitive = "pointer")]
+        if let Some((src_id, dst_id)) = id
+            .as_local()
+            // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+            // would presumably panic if a fake `DefIndex` were passed.
+            .and_then(|dst_id| {
+                item.item_id.expect_def_id().as_local().map(|src_id| (src_id, dst_id))
+            })
+        {
+            if self.cx.tcx.privacy_access_levels(()).is_exported(src_id)
+                && !self.cx.tcx.privacy_access_levels(()).is_exported(dst_id)
+            {
+                privacy_error(self.cx, diag_info, path_str);
+            }
+        }
+
+        Some(())
+    }
+
+    fn report_disambiguator_mismatch(
+        &self,
+        path_str: &str,
+        ori_link: &MarkdownLink,
+        specified: Disambiguator,
+        resolved: Res,
+        diag_info: &DiagnosticInfo<'_>,
+    ) {
+        // The resolved item did not match the disambiguator; give a better error than 'not found'
+        let msg = format!("incompatible link kind for `{}`", path_str);
+        let callback = |diag: &mut Diagnostic, sp: Option<rustc_span::Span>| {
+            let note = format!(
+                "this link resolved to {} {}, which is not {} {}",
+                resolved.article(),
+                resolved.descr(),
+                specified.article(),
+                specified.descr(),
+            );
+            if let Some(sp) = sp {
+                diag.span_label(sp, &note);
+            } else {
+                diag.note(&note);
+            }
+            suggest_disambiguator(resolved, diag, path_str, &ori_link.link, sp);
+        };
+        report_diagnostic(self.cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, diag_info, callback);
+    }
+
+    fn report_rawptr_assoc_feature_gate(&self, dox: &str, ori_link: &MarkdownLink, item: &Item) {
+        let span =
+            super::source_span_for_markdown_range(self.cx.tcx, dox, &ori_link.range, &item.attrs)
+                .unwrap_or_else(|| item.attr_span(self.cx.tcx));
+        rustc_session::parse::feature_err(
+            &self.cx.tcx.sess.parse_sess,
+            sym::intra_doc_pointers,
+            span,
+            "linking to associated items of raw pointers is experimental",
+        )
+        .note("rustdoc does not allow disambiguating between `*const` and `*mut`, and pointers are unstable until it does")
+        .emit();
+    }
+
+    fn resolve_with_disambiguator_cached(
+        &mut self,
+        key: ResolutionInfo,
+        diag: DiagnosticInfo<'_>,
+        // If errors are cached then they are only reported on first ocurrence
+        // which we want in some cases but not in others.
+        cache_errors: bool,
+    ) -> Option<(Res, Option<UrlFragment>)> {
+        if let Some(res) = self.visited_links.get(&key) {
+            if res.is_some() || cache_errors {
+                return res.clone();
+            }
+        }
+
+        let res = self.resolve_with_disambiguator(&key, diag.clone()).and_then(|(res, def_id)| {
+            let fragment = match (&key.extra_fragment, def_id) {
+                (Some(_), Some(def_id)) => {
+                    report_anchor_conflict(self.cx, diag, def_id);
+                    return None;
+                }
+                (Some(u_frag), None) => Some(UrlFragment::UserWritten(u_frag.clone())),
+                (None, Some(def_id)) => Some(UrlFragment::Item(def_id)),
+                (None, None) => None,
+            };
+            Some((res, fragment))
+        });
+
+        if res.is_some() || cache_errors {
+            self.visited_links.insert(key, res.clone());
+        }
+        res
+    }
+
+    /// After parsing the disambiguator, resolve the main part of the link.
+    // FIXME(jynelson): wow this is just so much
+    fn resolve_with_disambiguator(
+        &mut self,
+        key: &ResolutionInfo,
+        diag: DiagnosticInfo<'_>,
+    ) -> Option<(Res, Option<DefId>)> {
+        let disambiguator = key.dis;
+        let path_str = &key.path_str;
+        let item_id = key.item_id;
+        let base_node = key.module_id;
+
+        match disambiguator.map(Disambiguator::ns) {
+            Some(expected_ns) => {
+                match self.resolve(path_str, expected_ns, item_id, base_node) {
+                    Ok(res) => Some(res),
+                    Err(err) => {
+                        // We only looked in one namespace. Try to give a better error if possible.
+                        // FIXME: really it should be `resolution_failure` that does this, not `resolve_with_disambiguator`.
+                        // See https://github.com/rust-lang/rust/pull/76955#discussion_r493953382 for a good approach.
+                        let mut err = ResolutionFailure::NotResolved(err);
+                        for other_ns in [TypeNS, ValueNS, MacroNS] {
+                            if other_ns != expected_ns {
+                                if let Ok(res) =
+                                    self.resolve(path_str, other_ns, item_id, base_node)
+                                {
+                                    err = ResolutionFailure::WrongNamespace {
+                                        res: full_res(self.cx.tcx, res),
+                                        expected_ns,
+                                    };
+                                    break;
+                                }
+                            }
+                        }
+                        resolution_failure(self, diag, path_str, disambiguator, smallvec![err])
+                    }
+                }
+            }
+            None => {
+                // Try everything!
+                let mut candidate = |ns| {
+                    self.resolve(path_str, ns, item_id, base_node)
+                        .map_err(ResolutionFailure::NotResolved)
+                };
+
+                let candidates = PerNS {
+                    macro_ns: candidate(MacroNS),
+                    type_ns: candidate(TypeNS),
+                    value_ns: candidate(ValueNS).and_then(|(res, def_id)| {
+                        match res {
+                            // Constructors are picked up in the type namespace.
+                            Res::Def(DefKind::Ctor(..), _) => {
+                                Err(ResolutionFailure::WrongNamespace { res, expected_ns: TypeNS })
+                            }
+                            _ => Ok((res, def_id)),
+                        }
+                    }),
+                };
+
+                let len = candidates.iter().filter(|res| res.is_ok()).count();
+
+                if len == 0 {
+                    return resolution_failure(
+                        self,
+                        diag,
+                        path_str,
+                        disambiguator,
+                        candidates.into_iter().filter_map(|res| res.err()).collect(),
+                    );
+                }
+
+                if len == 1 {
+                    Some(candidates.into_iter().find_map(|res| res.ok()).unwrap())
+                } else if len == 2 && is_derive_trait_collision(&candidates) {
+                    Some(candidates.type_ns.unwrap())
+                } else {
+                    let ignore_macro = is_derive_trait_collision(&candidates);
+                    // If we're reporting an ambiguity, don't mention the namespaces that failed
+                    let mut candidates =
+                        candidates.map(|candidate| candidate.ok().map(|(res, _)| res));
+                    if ignore_macro {
+                        candidates.macro_ns = None;
+                    }
+                    ambiguity_error(self.cx, diag, path_str, candidates.present_items().collect());
+                    None
+                }
+            }
+        }
+    }
+}
+
+/// Get the section of a link between the backticks,
+/// or the whole link if there aren't any backticks.
+///
+/// For example:
+///
+/// ```text
+/// [`Foo`]
+///   ^^^
+/// ```
+fn range_between_backticks(ori_link: &MarkdownLink) -> Range<usize> {
+    let after_first_backtick_group = ori_link.link.bytes().position(|b| b != b'`').unwrap_or(0);
+    let before_second_backtick_group = ori_link
+        .link
+        .bytes()
+        .skip(after_first_backtick_group)
+        .position(|b| b == b'`')
+        .unwrap_or(ori_link.link.len());
+    (ori_link.range.start + after_first_backtick_group)
+        ..(ori_link.range.start + before_second_backtick_group)
+}
+
+/// Returns true if we should ignore `link` due to it being unlikely
+/// that it is an intra-doc link. `link` should still have disambiguators
+/// if there were any.
+///
+/// The difference between this and [`should_ignore_link()`] is that this
+/// check should only be used on links that still have disambiguators.
+fn should_ignore_link_with_disambiguators(link: &str) -> bool {
+    link.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;@()".contains(ch)))
+}
+
+/// Returns true if we should ignore `path_str` due to it being unlikely
+/// that it is an intra-doc link.
+fn should_ignore_link(path_str: &str) -> bool {
+    path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;".contains(ch)))
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+/// Disambiguators for a link.
+enum Disambiguator {
+    /// `prim@`
+    ///
+    /// This is buggy, see <https://github.com/rust-lang/rust/pull/77875#discussion_r503583103>
+    Primitive,
+    /// `struct@` or `f()`
+    Kind(DefKind),
+    /// `type@`
+    Namespace(Namespace),
+}
+
+impl Disambiguator {
+    /// Given a link, parse and return `(disambiguator, path_str, link_text)`.
+    ///
+    /// This returns `Ok(Some(...))` if a disambiguator was found,
+    /// `Ok(None)` if no disambiguator was found, or `Err(...)`
+    /// if there was a problem with the disambiguator.
+    fn from_str(link: &str) -> Result<Option<(Self, &str, &str)>, (String, Range<usize>)> {
+        use Disambiguator::{Kind, Namespace as NS, Primitive};
+
+        if let Some(idx) = link.find('@') {
+            let (prefix, rest) = link.split_at(idx);
+            let d = match prefix {
+                "struct" => Kind(DefKind::Struct),
+                "enum" => Kind(DefKind::Enum),
+                "trait" => Kind(DefKind::Trait),
+                "union" => Kind(DefKind::Union),
+                "module" | "mod" => Kind(DefKind::Mod),
+                "const" | "constant" => Kind(DefKind::Const),
+                "static" => Kind(DefKind::Static(Mutability::Not)),
+                "function" | "fn" | "method" => Kind(DefKind::Fn),
+                "derive" => Kind(DefKind::Macro(MacroKind::Derive)),
+                "type" => NS(Namespace::TypeNS),
+                "value" => NS(Namespace::ValueNS),
+                "macro" => NS(Namespace::MacroNS),
+                "prim" | "primitive" => Primitive,
+                _ => return Err((format!("unknown disambiguator `{}`", prefix), 0..idx)),
+            };
+            Ok(Some((d, &rest[1..], &rest[1..])))
+        } else {
+            let suffixes = [
+                ("!()", DefKind::Macro(MacroKind::Bang)),
+                ("!{}", DefKind::Macro(MacroKind::Bang)),
+                ("![]", DefKind::Macro(MacroKind::Bang)),
+                ("()", DefKind::Fn),
+                ("!", DefKind::Macro(MacroKind::Bang)),
+            ];
+            for (suffix, kind) in suffixes {
+                if let Some(path_str) = link.strip_suffix(suffix) {
+                    // Avoid turning `!` or `()` into an empty string
+                    if !path_str.is_empty() {
+                        return Ok(Some((Kind(kind), path_str, link)));
+                    }
+                }
+            }
+            Ok(None)
+        }
+    }
+
+    fn ns(self) -> Namespace {
+        match self {
+            Self::Namespace(n) => n,
+            Self::Kind(k) => {
+                k.ns().expect("only DefKinds with a valid namespace can be disambiguators")
+            }
+            Self::Primitive => TypeNS,
+        }
+    }
+
+    fn article(self) -> &'static str {
+        match self {
+            Self::Namespace(_) => panic!("article() doesn't make sense for namespaces"),
+            Self::Kind(k) => k.article(),
+            Self::Primitive => "a",
+        }
+    }
+
+    fn descr(self) -> &'static str {
+        match self {
+            Self::Namespace(n) => n.descr(),
+            // HACK(jynelson): the source of `DefKind::descr` only uses the DefId for
+            // printing "module" vs "crate" so using the wrong ID is not a huge problem
+            Self::Kind(k) => k.descr(CRATE_DEF_ID.to_def_id()),
+            Self::Primitive => "builtin type",
+        }
+    }
+}
+
+/// A suggestion to show in a diagnostic.
+enum Suggestion {
+    /// `struct@`
+    Prefix(&'static str),
+    /// `f()`
+    Function,
+    /// `m!`
+    Macro,
+    /// `foo` without any disambiguator
+    RemoveDisambiguator,
+}
+
+impl Suggestion {
+    fn descr(&self) -> Cow<'static, str> {
+        match self {
+            Self::Prefix(x) => format!("prefix with `{}@`", x).into(),
+            Self::Function => "add parentheses".into(),
+            Self::Macro => "add an exclamation mark".into(),
+            Self::RemoveDisambiguator => "remove the disambiguator".into(),
+        }
+    }
+
+    fn as_help(&self, path_str: &str) -> String {
+        // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
+        match self {
+            Self::Prefix(prefix) => format!("{}@{}", prefix, path_str),
+            Self::Function => format!("{}()", path_str),
+            Self::Macro => format!("{}!", path_str),
+            Self::RemoveDisambiguator => path_str.into(),
+        }
+    }
+
+    fn as_help_span(
+        &self,
+        path_str: &str,
+        ori_link: &str,
+        sp: rustc_span::Span,
+    ) -> Vec<(rustc_span::Span, String)> {
+        let inner_sp = match ori_link.find('(') {
+            Some(index) => sp.with_hi(sp.lo() + BytePos(index as _)),
+            None => sp,
+        };
+        let inner_sp = match ori_link.find('!') {
+            Some(index) => inner_sp.with_hi(inner_sp.lo() + BytePos(index as _)),
+            None => inner_sp,
+        };
+        let inner_sp = match ori_link.find('@') {
+            Some(index) => inner_sp.with_lo(inner_sp.lo() + BytePos(index as u32 + 1)),
+            None => inner_sp,
+        };
+        match self {
+            Self::Prefix(prefix) => {
+                // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
+                let mut sugg = vec![(sp.with_hi(inner_sp.lo()), format!("{}@", prefix))];
+                if sp.hi() != inner_sp.hi() {
+                    sugg.push((inner_sp.shrink_to_hi().with_hi(sp.hi()), String::new()));
+                }
+                sugg
+            }
+            Self::Function => {
+                let mut sugg = vec![(inner_sp.shrink_to_hi().with_hi(sp.hi()), "()".to_string())];
+                if sp.lo() != inner_sp.lo() {
+                    sugg.push((inner_sp.shrink_to_lo().with_lo(sp.lo()), String::new()));
+                }
+                sugg
+            }
+            Self::Macro => {
+                let mut sugg = vec![(inner_sp.shrink_to_hi(), "!".to_string())];
+                if sp.lo() != inner_sp.lo() {
+                    sugg.push((inner_sp.shrink_to_lo().with_lo(sp.lo()), String::new()));
+                }
+                sugg
+            }
+            Self::RemoveDisambiguator => vec![(sp, path_str.into())],
+        }
+    }
+}
+
+/// Reports a diagnostic for an intra-doc link.
+///
+/// If no link range is provided, or the source span of the link cannot be determined, the span of
+/// the entire documentation block is used for the lint. If a range is provided but the span
+/// calculation fails, a note is added to the diagnostic pointing to the link in the markdown.
+///
+/// The `decorate` callback is invoked in all cases to allow further customization of the
+/// diagnostic before emission. If the span of the link was able to be determined, the second
+/// parameter of the callback will contain it, and the primary span of the diagnostic will be set
+/// to it.
+fn report_diagnostic(
+    tcx: TyCtxt<'_>,
+    lint: &'static Lint,
+    msg: &str,
+    DiagnosticInfo { item, ori_link: _, dox, link_range }: &DiagnosticInfo<'_>,
+    decorate: impl FnOnce(&mut Diagnostic, Option<rustc_span::Span>),
+) {
+    let Some(hir_id) = DocContext::as_local_hir_id(tcx, item.item_id)
+    else {
+        // If non-local, no need to check anything.
+        info!("ignoring warning from parent crate: {}", msg);
+        return;
+    };
+
+    let sp = item.attr_span(tcx);
+
+    tcx.struct_span_lint_hir(lint, hir_id, sp, |lint| {
+        let mut diag = lint.build(msg);
+
+        let span =
+            super::source_span_for_markdown_range(tcx, dox, link_range, &item.attrs).map(|sp| {
+                if dox.as_bytes().get(link_range.start) == Some(&b'`')
+                    && dox.as_bytes().get(link_range.end - 1) == Some(&b'`')
+                {
+                    sp.with_lo(sp.lo() + BytePos(1)).with_hi(sp.hi() - BytePos(1))
+                } else {
+                    sp
+                }
+            });
+
+        if let Some(sp) = span {
+            diag.set_span(sp);
+        } else {
+            // blah blah blah\nblah\nblah [blah] blah blah\nblah blah
+            //                       ^     ~~~~
+            //                       |     link_range
+            //                       last_new_line_offset
+            let last_new_line_offset = dox[..link_range.start].rfind('\n').map_or(0, |n| n + 1);
+            let line = dox[last_new_line_offset..].lines().next().unwrap_or("");
+
+            // Print the line containing the `link_range` and manually mark it with '^'s.
+            diag.note(&format!(
+                "the link appears in this line:\n\n{line}\n\
+                     {indicator: <before$}{indicator:^<found$}",
+                line = line,
+                indicator = "",
+                before = link_range.start - last_new_line_offset,
+                found = link_range.len(),
+            ));
+        }
+
+        decorate(&mut diag, span);
+
+        diag.emit();
+    });
+}
+
+/// Reports a link that failed to resolve.
+///
+/// This also tries to resolve any intermediate path segments that weren't
+/// handled earlier. For example, if passed `Item::Crate(std)` and `path_str`
+/// `std::io::Error::x`, this will resolve `std::io::Error`.
+fn resolution_failure(
+    collector: &mut LinkCollector<'_, '_>,
+    diag_info: DiagnosticInfo<'_>,
+    path_str: &str,
+    disambiguator: Option<Disambiguator>,
+    kinds: SmallVec<[ResolutionFailure<'_>; 3]>,
+) -> Option<(Res, Option<DefId>)> {
+    let tcx = collector.cx.tcx;
+    let mut recovered_res = None;
+    report_diagnostic(
+        tcx,
+        BROKEN_INTRA_DOC_LINKS,
+        &format!("unresolved link to `{}`", path_str),
+        &diag_info,
+        |diag, sp| {
+            let item = |res: Res| format!("the {} `{}`", res.descr(), res.name(tcx),);
+            let assoc_item_not_allowed = |res: Res| {
+                let name = res.name(tcx);
+                format!(
+                    "`{}` is {} {}, not a module or type, and cannot have associated items",
+                    name,
+                    res.article(),
+                    res.descr()
+                )
+            };
+            // ignore duplicates
+            let mut variants_seen = SmallVec::<[_; 3]>::new();
+            for mut failure in kinds {
+                let variant = std::mem::discriminant(&failure);
+                if variants_seen.contains(&variant) {
+                    continue;
+                }
+                variants_seen.push(variant);
+
+                if let ResolutionFailure::NotResolved(UnresolvedPath {
+                    item_id,
+                    module_id,
+                    partial_res,
+                    unresolved,
+                }) = &mut failure
+                {
+                    use DefKind::*;
+
+                    let item_id = *item_id;
+                    let module_id = *module_id;
+                    // FIXME(jynelson): this might conflict with my `Self` fix in #76467
+                    // FIXME: maybe use itertools `collect_tuple` instead?
+                    fn split(path: &str) -> Option<(&str, &str)> {
+                        let mut splitter = path.rsplitn(2, "::");
+                        splitter.next().and_then(|right| splitter.next().map(|left| (left, right)))
+                    }
+
+                    // Check if _any_ parent of the path gets resolved.
+                    // If so, report it and say the first which failed; if not, say the first path segment didn't resolve.
+                    let mut name = path_str;
+                    'outer: loop {
+                        let Some((start, end)) = split(name) else {
+                            // avoid bug that marked [Quux::Z] as missing Z, not Quux
+                            if partial_res.is_none() {
+                                *unresolved = name.into();
+                            }
+                            break;
+                        };
+                        name = start;
+                        for ns in [TypeNS, ValueNS, MacroNS] {
+                            if let Ok(res) = collector.resolve(start, ns, item_id, module_id) {
+                                debug!("found partial_res={:?}", res);
+                                *partial_res = Some(full_res(collector.cx.tcx, res));
+                                *unresolved = end.into();
+                                break 'outer;
+                            }
+                        }
+                        *unresolved = end.into();
+                    }
+
+                    let last_found_module = match *partial_res {
+                        Some(Res::Def(DefKind::Mod, id)) => Some(id),
+                        None => Some(module_id),
+                        _ => None,
+                    };
+                    // See if this was a module: `[path]` or `[std::io::nope]`
+                    if let Some(module) = last_found_module {
+                        let note = if partial_res.is_some() {
+                            // Part of the link resolved; e.g. `std::io::nonexistent`
+                            let module_name = tcx.item_name(module);
+                            format!("no item named `{}` in module `{}`", unresolved, module_name)
+                        } else {
+                            // None of the link resolved; e.g. `Notimported`
+                            format!("no item named `{}` in scope", unresolved)
+                        };
+                        if let Some(span) = sp {
+                            diag.span_label(span, &note);
+                        } else {
+                            diag.note(&note);
+                        }
+
+                        if !path_str.contains("::") {
+                            if disambiguator.map_or(true, |d| d.ns() == MacroNS)
+                                && let Some(&res) = collector.cx.resolver_caches.all_macro_rules
+                                                             .get(&Symbol::intern(path_str))
+                            {
+                                diag.note(format!(
+                                    "`macro_rules` named `{path_str}` exists in this crate, \
+                                     but it is not in scope at this link's location"
+                                ));
+                                recovered_res = res.try_into().ok().map(|res| (res, None));
+                            } else {
+                                // If the link has `::` in it, assume it was meant to be an
+                                // intra-doc link. Otherwise, the `[]` might be unrelated.
+                                diag.help("to escape `[` and `]` characters, \
+                                           add '\\' before them like `\\[` or `\\]`");
+                            }
+                        }
+
+                        continue;
+                    }
+
+                    // Otherwise, it must be an associated item or variant
+                    let res = partial_res.expect("None case was handled by `last_found_module`");
+                    let name = res.name(tcx);
+                    let kind = match res {
+                        Res::Def(kind, _) => Some(kind),
+                        Res::Primitive(_) => None,
+                    };
+                    let path_description = if let Some(kind) = kind {
+                        match kind {
+                            Mod | ForeignMod => "inner item",
+                            Struct => "field or associated item",
+                            Enum | Union => "variant or associated item",
+                            Variant
+                            | Field
+                            | Closure
+                            | Generator
+                            | AssocTy
+                            | AssocConst
+                            | AssocFn
+                            | Fn
+                            | Macro(_)
+                            | Const
+                            | ConstParam
+                            | ExternCrate
+                            | Use
+                            | LifetimeParam
+                            | Ctor(_, _)
+                            | AnonConst
+                            | InlineConst => {
+                                let note = assoc_item_not_allowed(res);
+                                if let Some(span) = sp {
+                                    diag.span_label(span, &note);
+                                } else {
+                                    diag.note(&note);
+                                }
+                                return;
+                            }
+                            Trait | TyAlias | ForeignTy | OpaqueTy | TraitAlias | TyParam
+                            | Static(_) => "associated item",
+                            Impl | GlobalAsm => unreachable!("not a path"),
+                        }
+                    } else {
+                        "associated item"
+                    };
+                    let note = format!(
+                        "the {} `{}` has no {} named `{}`",
+                        res.descr(),
+                        name,
+                        disambiguator.map_or(path_description, |d| d.descr()),
+                        unresolved,
+                    );
+                    if let Some(span) = sp {
+                        diag.span_label(span, &note);
+                    } else {
+                        diag.note(&note);
+                    }
+
+                    continue;
+                }
+                let note = match failure {
+                    ResolutionFailure::NotResolved { .. } => unreachable!("handled above"),
+                    ResolutionFailure::WrongNamespace { res, expected_ns } => {
+                        suggest_disambiguator(res, diag, path_str, diag_info.ori_link, sp);
+
+                        format!(
+                            "this link resolves to {}, which is not in the {} namespace",
+                            item(res),
+                            expected_ns.descr()
+                        )
+                    }
+                };
+                if let Some(span) = sp {
+                    diag.span_label(span, &note);
+                } else {
+                    diag.note(&note);
+                }
+            }
+        },
+    );
+
+    recovered_res
+}
+
+fn report_multiple_anchors(cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>) {
+    let msg = format!("`{}` contains multiple anchors", diag_info.ori_link);
+    anchor_failure(cx, diag_info, &msg, 1)
+}
+
+fn report_anchor_conflict(cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>, def_id: DefId) {
+    let (link, kind) = (diag_info.ori_link, Res::from_def_id(cx.tcx, def_id).descr());
+    let msg = format!("`{link}` contains an anchor, but links to {kind}s are already anchored");
+    anchor_failure(cx, diag_info, &msg, 0)
+}
+
+/// Report an anchor failure.
+fn anchor_failure(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    msg: &str,
+    anchor_idx: usize,
+) {
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, &diag_info, |diag, sp| {
+        if let Some(mut sp) = sp {
+            if let Some((fragment_offset, _)) =
+                diag_info.ori_link.char_indices().filter(|(_, x)| *x == '#').nth(anchor_idx)
+            {
+                sp = sp.with_lo(sp.lo() + BytePos(fragment_offset as _));
+            }
+            diag.span_label(sp, "invalid anchor");
+        }
+    });
+}
+
+/// Report an error in the link disambiguator.
+fn disambiguator_error(
+    cx: &DocContext<'_>,
+    mut diag_info: DiagnosticInfo<'_>,
+    disambiguator_range: Range<usize>,
+    msg: &str,
+) {
+    diag_info.link_range = disambiguator_range;
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, &diag_info, |diag, _sp| {
+        let msg = format!(
+            "see {}/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators",
+            crate::DOC_RUST_LANG_ORG_CHANNEL
+        );
+        diag.note(&msg);
+    });
+}
+
+fn report_malformed_generics(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    err: MalformedGenerics,
+    path_str: &str,
+) {
+    report_diagnostic(
+        cx.tcx,
+        BROKEN_INTRA_DOC_LINKS,
+        &format!("unresolved link to `{}`", path_str),
+        &diag_info,
+        |diag, sp| {
+            let note = match err {
+                MalformedGenerics::UnbalancedAngleBrackets => "unbalanced angle brackets",
+                MalformedGenerics::MissingType => "missing type for generic parameters",
+                MalformedGenerics::HasFullyQualifiedSyntax => {
+                    diag.note(
+                        "see https://github.com/rust-lang/rust/issues/74563 for more information",
+                    );
+                    "fully-qualified syntax is unsupported"
+                }
+                MalformedGenerics::InvalidPathSeparator => "has invalid path separator",
+                MalformedGenerics::TooManyAngleBrackets => "too many angle brackets",
+                MalformedGenerics::EmptyAngleBrackets => "empty angle brackets",
+            };
+            if let Some(span) = sp {
+                diag.span_label(span, note);
+            } else {
+                diag.note(note);
+            }
+        },
+    );
+}
+
+/// Report an ambiguity error, where there were multiple possible resolutions.
+fn ambiguity_error(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    path_str: &str,
+    candidates: Vec<Res>,
+) {
+    let mut msg = format!("`{}` is ", path_str);
+
+    match candidates.as_slice() {
+        [first_def, second_def] => {
+            msg += &format!(
+                "both {} {} and {} {}",
+                first_def.article(),
+                first_def.descr(),
+                second_def.article(),
+                second_def.descr(),
+            );
+        }
+        _ => {
+            let mut candidates = candidates.iter().peekable();
+            while let Some(res) = candidates.next() {
+                if candidates.peek().is_some() {
+                    msg += &format!("{} {}, ", res.article(), res.descr());
+                } else {
+                    msg += &format!("and {} {}", res.article(), res.descr());
+                }
+            }
+        }
+    }
+
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, &diag_info, |diag, sp| {
+        if let Some(sp) = sp {
+            diag.span_label(sp, "ambiguous link");
+        } else {
+            diag.note("ambiguous link");
+        }
+
+        for res in candidates {
+            suggest_disambiguator(res, diag, path_str, diag_info.ori_link, sp);
+        }
+    });
+}
+
+/// In case of an ambiguity or mismatched disambiguator, suggest the correct
+/// disambiguator.
+fn suggest_disambiguator(
+    res: Res,
+    diag: &mut Diagnostic,
+    path_str: &str,
+    ori_link: &str,
+    sp: Option<rustc_span::Span>,
+) {
+    let suggestion = res.disambiguator_suggestion();
+    let help = format!("to link to the {}, {}", res.descr(), suggestion.descr());
+
+    if let Some(sp) = sp {
+        let mut spans = suggestion.as_help_span(path_str, ori_link, sp);
+        if spans.len() > 1 {
+            diag.multipart_suggestion(&help, spans, Applicability::MaybeIncorrect);
+        } else {
+            let (sp, suggestion_text) = spans.pop().unwrap();
+            diag.span_suggestion_verbose(sp, &help, suggestion_text, Applicability::MaybeIncorrect);
+        }
+    } else {
+        diag.help(&format!("{}: {}", help, suggestion.as_help(path_str)));
+    }
+}
+
+/// Report a link from a public item to a private one.
+fn privacy_error(cx: &DocContext<'_>, diag_info: &DiagnosticInfo<'_>, path_str: &str) {
+    let sym;
+    let item_name = match diag_info.item.name {
+        Some(name) => {
+            sym = name;
+            sym.as_str()
+        }
+        None => "<unknown>",
+    };
+    let msg =
+        format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
+
+    report_diagnostic(cx.tcx, PRIVATE_INTRA_DOC_LINKS, &msg, diag_info, |diag, sp| {
+        if let Some(sp) = sp {
+            diag.span_label(sp, "this item is private");
+        }
+
+        let note_msg = if cx.render_options.document_private {
+            "this link resolves only because you passed `--document-private-items`, but will break without"
+        } else {
+            "this link will resolve properly if you pass `--document-private-items`"
+        };
+        diag.note(note_msg);
+    });
+}
+
+/// Resolve a primitive type or value.
+fn resolve_primitive(path_str: &str, ns: Namespace) -> Option<Res> {
+    if ns != TypeNS {
+        return None;
+    }
+    use PrimitiveType::*;
+    let prim = match path_str {
+        "isize" => Isize,
+        "i8" => I8,
+        "i16" => I16,
+        "i32" => I32,
+        "i64" => I64,
+        "i128" => I128,
+        "usize" => Usize,
+        "u8" => U8,
+        "u16" => U16,
+        "u32" => U32,
+        "u64" => U64,
+        "u128" => U128,
+        "f32" => F32,
+        "f64" => F64,
+        "char" => Char,
+        "bool" | "true" | "false" => Bool,
+        "str" | "&str" => Str,
+        // See #80181 for why these don't have symbols associated.
+        "slice" => Slice,
+        "array" => Array,
+        "tuple" => Tuple,
+        "unit" => Unit,
+        "pointer" | "*const" | "*mut" => RawPointer,
+        "reference" | "&" | "&mut" => Reference,
+        "fn" => Fn,
+        "never" | "!" => Never,
+        _ => return None,
+    };
+    debug!("resolved primitives {:?}", prim);
+    Some(Res::Primitive(prim))
+}
+
+fn strip_generics_from_path(path_str: &str) -> Result<String, MalformedGenerics> {
+    let mut stripped_segments = vec![];
+    let mut path = path_str.chars().peekable();
+    let mut segment = Vec::new();
+
+    while let Some(chr) = path.next() {
+        match chr {
+            ':' => {
+                if path.next_if_eq(&':').is_some() {
+                    let stripped_segment =
+                        strip_generics_from_path_segment(mem::take(&mut segment))?;
+                    if !stripped_segment.is_empty() {
+                        stripped_segments.push(stripped_segment);
+                    }
+                } else {
+                    return Err(MalformedGenerics::InvalidPathSeparator);
+                }
+            }
+            '<' => {
+                segment.push(chr);
+
+                match path.next() {
+                    Some('<') => {
+                        return Err(MalformedGenerics::TooManyAngleBrackets);
+                    }
+                    Some('>') => {
+                        return Err(MalformedGenerics::EmptyAngleBrackets);
+                    }
+                    Some(chr) => {
+                        segment.push(chr);
+
+                        while let Some(chr) = path.next_if(|c| *c != '>') {
+                            segment.push(chr);
+                        }
+                    }
+                    None => break,
+                }
+            }
+            _ => segment.push(chr),
+        }
+        trace!("raw segment: {:?}", segment);
+    }
+
+    if !segment.is_empty() {
+        let stripped_segment = strip_generics_from_path_segment(segment)?;
+        if !stripped_segment.is_empty() {
+            stripped_segments.push(stripped_segment);
+        }
+    }
+
+    debug!("path_str: {:?}\nstripped segments: {:?}", path_str, &stripped_segments);
+
+    let stripped_path = stripped_segments.join("::");
+
+    if !stripped_path.is_empty() { Ok(stripped_path) } else { Err(MalformedGenerics::MissingType) }
+}
+
+fn strip_generics_from_path_segment(segment: Vec<char>) -> Result<String, MalformedGenerics> {
+    let mut stripped_segment = String::new();
+    let mut param_depth = 0;
+
+    let mut latest_generics_chunk = String::new();
+
+    for c in segment {
+        if c == '<' {
+            param_depth += 1;
+            latest_generics_chunk.clear();
+        } else if c == '>' {
+            param_depth -= 1;
+            if latest_generics_chunk.contains(" as ") {
+                // The segment tries to use fully-qualified syntax, which is currently unsupported.
+                // Give a helpful error message instead of completely ignoring the angle brackets.
+                return Err(MalformedGenerics::HasFullyQualifiedSyntax);
+            }
+        } else {
+            if param_depth == 0 {
+                stripped_segment.push(c);
+            } else {
+                latest_generics_chunk.push(c);
+            }
+        }
+    }
+
+    if param_depth == 0 {
+        Ok(stripped_segment)
+    } else {
+        // The segment has unbalanced angle brackets, e.g. `Vec<T` or `Vec<T>>`
+        Err(MalformedGenerics::UnbalancedAngleBrackets)
+    }
+}
diff --git a/src/librustdoc/passes/collect_intra_doc_links/early.rs b/src/librustdoc/passes/collect_intra_doc_links/early.rs
new file mode 100644
index 000000000..38cfd7a27
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links/early.rs
@@ -0,0 +1,405 @@
+use crate::clean::Attributes;
+use crate::core::ResolverCaches;
+use crate::passes::collect_intra_doc_links::preprocessed_markdown_links;
+use crate::passes::collect_intra_doc_links::{Disambiguator, PreprocessedMarkdownLink};
+
+use rustc_ast::visit::{self, AssocCtxt, Visitor};
+use rustc_ast::{self as ast, ItemKind};
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def::Namespace::*;
+use rustc_hir::def::{DefKind, Namespace, Res};
+use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, CRATE_DEF_ID};
+use rustc_hir::TraitCandidate;
+use rustc_middle::ty::{DefIdTree, Visibility};
+use rustc_resolve::{ParentScope, Resolver};
+use rustc_session::config::Externs;
+use rustc_session::Session;
+use rustc_span::symbol::sym;
+use rustc_span::{Symbol, SyntaxContext};
+
+use std::collections::hash_map::Entry;
+use std::mem;
+
+pub(crate) fn early_resolve_intra_doc_links(
+    resolver: &mut Resolver<'_>,
+    sess: &Session,
+    krate: &ast::Crate,
+    externs: Externs,
+    document_private_items: bool,
+) -> ResolverCaches {
+    let parent_scope =
+        ParentScope::module(resolver.expect_module(CRATE_DEF_ID.to_def_id()), resolver);
+    let mut link_resolver = EarlyDocLinkResolver {
+        resolver,
+        sess,
+        parent_scope,
+        visited_mods: Default::default(),
+        markdown_links: Default::default(),
+        doc_link_resolutions: Default::default(),
+        traits_in_scope: Default::default(),
+        all_traits: Default::default(),
+        all_trait_impls: Default::default(),
+        all_macro_rules: Default::default(),
+        document_private_items,
+    };
+
+    // Overridden `visit_item` below doesn't apply to the crate root,
+    // so we have to visit its attributes and reexports separately.
+    link_resolver.resolve_doc_links_local(&krate.attrs);
+    link_resolver.process_module_children_or_reexports(CRATE_DEF_ID.to_def_id());
+    visit::walk_crate(&mut link_resolver, krate);
+    link_resolver.process_extern_impls();
+
+    // FIXME: somehow rustdoc is still missing crates even though we loaded all
+    // the known necessary crates. Load them all unconditionally until we find a way to fix this.
+    // DO NOT REMOVE THIS without first testing on the reproducer in
+    // https://github.com/jyn514/objr/commit/edcee7b8124abf0e4c63873e8422ff81beb11ebb
+    for (extern_name, _) in externs.iter().filter(|(_, entry)| entry.add_prelude) {
+        link_resolver.resolver.resolve_rustdoc_path(extern_name, TypeNS, parent_scope);
+    }
+
+    ResolverCaches {
+        markdown_links: Some(link_resolver.markdown_links),
+        doc_link_resolutions: link_resolver.doc_link_resolutions,
+        traits_in_scope: link_resolver.traits_in_scope,
+        all_traits: Some(link_resolver.all_traits),
+        all_trait_impls: Some(link_resolver.all_trait_impls),
+        all_macro_rules: link_resolver.all_macro_rules,
+    }
+}
+
+fn doc_attrs<'a>(attrs: impl Iterator<Item = &'a ast::Attribute>) -> Attributes {
+    Attributes::from_ast_iter(attrs.map(|attr| (attr, None)), true)
+}
+
+struct EarlyDocLinkResolver<'r, 'ra> {
+    resolver: &'r mut Resolver<'ra>,
+    sess: &'r Session,
+    parent_scope: ParentScope<'ra>,
+    visited_mods: DefIdSet,
+    markdown_links: FxHashMap<String, Vec<PreprocessedMarkdownLink>>,
+    doc_link_resolutions: FxHashMap<(Symbol, Namespace, DefId), Option<Res<ast::NodeId>>>,
+    traits_in_scope: DefIdMap<Vec<TraitCandidate>>,
+    all_traits: Vec<DefId>,
+    all_trait_impls: Vec<DefId>,
+    all_macro_rules: FxHashMap<Symbol, Res<ast::NodeId>>,
+    document_private_items: bool,
+}
+
+impl<'ra> EarlyDocLinkResolver<'_, 'ra> {
+    fn add_traits_in_scope(&mut self, def_id: DefId) {
+        // Calls to `traits_in_scope` are expensive, so try to avoid them if only possible.
+        // Keys in the `traits_in_scope` cache are always module IDs.
+        if let Entry::Vacant(entry) = self.traits_in_scope.entry(def_id) {
+            let module = self.resolver.get_nearest_non_block_module(def_id);
+            let module_id = module.def_id();
+            let entry = if module_id == def_id {
+                Some(entry)
+            } else if let Entry::Vacant(entry) = self.traits_in_scope.entry(module_id) {
+                Some(entry)
+            } else {
+                None
+            };
+            if let Some(entry) = entry {
+                entry.insert(self.resolver.traits_in_scope(
+                    None,
+                    &ParentScope::module(module, self.resolver),
+                    SyntaxContext::root(),
+                    None,
+                ));
+            }
+        }
+    }
+
+    /// Add traits in scope for links in impls collected by the `collect-intra-doc-links` pass.
+    /// That pass filters impls using type-based information, but we don't yet have such
+    /// information here, so we just conservatively calculate traits in scope for *all* modules
+    /// having impls in them.
+    fn process_extern_impls(&mut self) {
+        // Resolving links in already existing crates may trigger loading of new crates.
+        let mut start_cnum = 0;
+        loop {
+            let crates = Vec::from_iter(self.resolver.cstore().crates_untracked());
+            for &cnum in &crates[start_cnum..] {
+                let all_traits =
+                    Vec::from_iter(self.resolver.cstore().traits_in_crate_untracked(cnum));
+                let all_trait_impls =
+                    Vec::from_iter(self.resolver.cstore().trait_impls_in_crate_untracked(cnum));
+                let all_inherent_impls =
+                    Vec::from_iter(self.resolver.cstore().inherent_impls_in_crate_untracked(cnum));
+                let all_incoherent_impls = Vec::from_iter(
+                    self.resolver.cstore().incoherent_impls_in_crate_untracked(cnum),
+                );
+
+                // Querying traits in scope is expensive so we try to prune the impl and traits lists
+                // using privacy, private traits and impls from other crates are never documented in
+                // the current crate, and links in their doc comments are not resolved.
+                for &def_id in &all_traits {
+                    if self.resolver.cstore().visibility_untracked(def_id).is_public() {
+                        self.resolve_doc_links_extern_impl(def_id, false);
+                    }
+                }
+                for &(trait_def_id, impl_def_id, simplified_self_ty) in &all_trait_impls {
+                    if self.resolver.cstore().visibility_untracked(trait_def_id).is_public()
+                        && simplified_self_ty.and_then(|ty| ty.def()).map_or(true, |ty_def_id| {
+                            self.resolver.cstore().visibility_untracked(ty_def_id).is_public()
+                        })
+                    {
+                        self.resolve_doc_links_extern_impl(impl_def_id, false);
+                    }
+                }
+                for (ty_def_id, impl_def_id) in all_inherent_impls {
+                    if self.resolver.cstore().visibility_untracked(ty_def_id).is_public() {
+                        self.resolve_doc_links_extern_impl(impl_def_id, true);
+                    }
+                }
+                for impl_def_id in all_incoherent_impls {
+                    self.resolve_doc_links_extern_impl(impl_def_id, true);
+                }
+
+                self.all_traits.extend(all_traits);
+                self.all_trait_impls
+                    .extend(all_trait_impls.into_iter().map(|(_, def_id, _)| def_id));
+            }
+
+            if crates.len() > start_cnum {
+                start_cnum = crates.len();
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn resolve_doc_links_extern_impl(&mut self, def_id: DefId, is_inherent: bool) {
+        self.resolve_doc_links_extern_outer_fixme(def_id, def_id);
+        let assoc_item_def_ids = Vec::from_iter(
+            self.resolver.cstore().associated_item_def_ids_untracked(def_id, self.sess),
+        );
+        for assoc_def_id in assoc_item_def_ids {
+            if !is_inherent || self.resolver.cstore().visibility_untracked(assoc_def_id).is_public()
+            {
+                self.resolve_doc_links_extern_outer_fixme(assoc_def_id, def_id);
+            }
+        }
+    }
+
+    // FIXME: replace all uses with `resolve_doc_links_extern_outer` to actually resolve links, not
+    // just add traits in scope. This may be expensive and require benchmarking and optimization.
+    fn resolve_doc_links_extern_outer_fixme(&mut self, def_id: DefId, scope_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        if let Some(parent_id) = self.resolver.opt_parent(scope_id) {
+            self.add_traits_in_scope(parent_id);
+        }
+    }
+
+    fn resolve_doc_links_extern_outer(&mut self, def_id: DefId, scope_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        let attrs = Vec::from_iter(self.resolver.cstore().item_attrs_untracked(def_id, self.sess));
+        let parent_scope = ParentScope::module(
+            self.resolver.get_nearest_non_block_module(
+                self.resolver.opt_parent(scope_id).unwrap_or(scope_id),
+            ),
+            self.resolver,
+        );
+        self.resolve_doc_links(doc_attrs(attrs.iter()), parent_scope);
+    }
+
+    fn resolve_doc_links_extern_inner(&mut self, def_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        let attrs = Vec::from_iter(self.resolver.cstore().item_attrs_untracked(def_id, self.sess));
+        let parent_scope = ParentScope::module(self.resolver.expect_module(def_id), self.resolver);
+        self.resolve_doc_links(doc_attrs(attrs.iter()), parent_scope);
+    }
+
+    fn resolve_doc_links_local(&mut self, attrs: &[ast::Attribute]) {
+        if !attrs.iter().any(|attr| attr.may_have_doc_links()) {
+            return;
+        }
+        self.resolve_doc_links(doc_attrs(attrs.iter()), self.parent_scope);
+    }
+
+    fn resolve_and_cache(
+        &mut self,
+        path_str: &str,
+        ns: Namespace,
+        parent_scope: &ParentScope<'ra>,
+    ) -> bool {
+        // FIXME: This caching may be incorrect in case of multiple `macro_rules`
+        // items with the same name in the same module.
+        self.doc_link_resolutions
+            .entry((Symbol::intern(path_str), ns, parent_scope.module.def_id()))
+            .or_insert_with_key(|(path, ns, _)| {
+                self.resolver.resolve_rustdoc_path(path.as_str(), *ns, *parent_scope)
+            })
+            .is_some()
+    }
+
+    fn resolve_doc_links(&mut self, attrs: Attributes, parent_scope: ParentScope<'ra>) {
+        let mut need_traits_in_scope = false;
+        for (doc_module, doc) in attrs.prepare_to_doc_link_resolution() {
+            assert_eq!(doc_module, None);
+            let mut tmp_links = mem::take(&mut self.markdown_links);
+            let links =
+                tmp_links.entry(doc).or_insert_with_key(|doc| preprocessed_markdown_links(doc));
+            for PreprocessedMarkdownLink(pp_link, _) in links {
+                if let Ok(pinfo) = pp_link {
+                    // The logic here is a conservative approximation for path resolution in
+                    // `resolve_with_disambiguator`.
+                    if let Some(ns) = pinfo.disambiguator.map(Disambiguator::ns) {
+                        if self.resolve_and_cache(&pinfo.path_str, ns, &parent_scope) {
+                            continue;
+                        }
+                    }
+
+                    // Resolve all namespaces due to no disambiguator or for diagnostics.
+                    let mut any_resolved = false;
+                    let mut need_assoc = false;
+                    for ns in [TypeNS, ValueNS, MacroNS] {
+                        if self.resolve_and_cache(&pinfo.path_str, ns, &parent_scope) {
+                            any_resolved = true;
+                        } else if ns != MacroNS {
+                            need_assoc = true;
+                        }
+                    }
+
+                    // Resolve all prefixes for type-relative resolution or for diagnostics.
+                    if need_assoc || !any_resolved {
+                        let mut path = &pinfo.path_str[..];
+                        while let Some(idx) = path.rfind("::") {
+                            path = &path[..idx];
+                            need_traits_in_scope = true;
+                            for ns in [TypeNS, ValueNS, MacroNS] {
+                                self.resolve_and_cache(path, ns, &parent_scope);
+                            }
+                        }
+                    }
+                }
+            }
+            self.markdown_links = tmp_links;
+        }
+
+        if need_traits_in_scope {
+            self.add_traits_in_scope(parent_scope.module.def_id());
+        }
+    }
+
+    /// When reexports are inlined, they are replaced with item which they refer to, those items
+    /// may have links in their doc comments, those links are resolved at the item definition site,
+    /// so we need to know traits in scope at that definition site.
+    fn process_module_children_or_reexports(&mut self, module_id: DefId) {
+        if !self.visited_mods.insert(module_id) {
+            return; // avoid infinite recursion
+        }
+
+        for child in self.resolver.module_children_or_reexports(module_id) {
+            // This condition should give a superset of `denied` from `fn clean_use_statement`.
+            if child.vis.is_public()
+                || self.document_private_items
+                    && child.vis != Visibility::Restricted(module_id)
+                    && module_id.is_local()
+            {
+                if let Some(def_id) = child.res.opt_def_id() && !def_id.is_local() {
+                    let scope_id = match child.res {
+                        Res::Def(DefKind::Variant, ..) => self.resolver.parent(def_id),
+                        _ => def_id,
+                    };
+                    self.resolve_doc_links_extern_outer(def_id, scope_id); // Outer attribute scope
+                    if let Res::Def(DefKind::Mod, ..) = child.res {
+                        self.resolve_doc_links_extern_inner(def_id); // Inner attribute scope
+                    }
+                    // `DefKind::Trait`s are processed in `process_extern_impls`.
+                    if let Res::Def(DefKind::Mod | DefKind::Enum, ..) = child.res {
+                        self.process_module_children_or_reexports(def_id);
+                    }
+                    if let Res::Def(DefKind::Struct | DefKind::Union | DefKind::Variant, _) =
+                        child.res
+                    {
+                        let field_def_ids = Vec::from_iter(
+                            self.resolver
+                                .cstore()
+                                .associated_item_def_ids_untracked(def_id, self.sess),
+                        );
+                        for field_def_id in field_def_ids {
+                            self.resolve_doc_links_extern_outer(field_def_id, scope_id);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl Visitor<'_> for EarlyDocLinkResolver<'_, '_> {
+    fn visit_item(&mut self, item: &ast::Item) {
+        self.resolve_doc_links_local(&item.attrs); // Outer attribute scope
+        if let ItemKind::Mod(..) = item.kind {
+            let module_def_id = self.resolver.local_def_id(item.id).to_def_id();
+            let module = self.resolver.expect_module(module_def_id);
+            let old_module = mem::replace(&mut self.parent_scope.module, module);
+            let old_macro_rules = self.parent_scope.macro_rules;
+            self.resolve_doc_links_local(&item.attrs); // Inner attribute scope
+            self.process_module_children_or_reexports(module_def_id);
+            visit::walk_item(self, item);
+            if item
+                .attrs
+                .iter()
+                .all(|attr| !attr.has_name(sym::macro_use) && !attr.has_name(sym::macro_escape))
+            {
+                self.parent_scope.macro_rules = old_macro_rules;
+            }
+            self.parent_scope.module = old_module;
+        } else {
+            match &item.kind {
+                ItemKind::Trait(..) => {
+                    self.all_traits.push(self.resolver.local_def_id(item.id).to_def_id());
+                }
+                ItemKind::Impl(box ast::Impl { of_trait: Some(..), .. }) => {
+                    self.all_trait_impls.push(self.resolver.local_def_id(item.id).to_def_id());
+                }
+                ItemKind::MacroDef(macro_def) if macro_def.macro_rules => {
+                    let (macro_rules_scope, res) =
+                        self.resolver.macro_rules_scope(self.resolver.local_def_id(item.id));
+                    self.parent_scope.macro_rules = macro_rules_scope;
+                    self.all_macro_rules.insert(item.ident.name, res);
+                }
+                _ => {}
+            }
+            visit::walk_item(self, item);
+        }
+    }
+
+    fn visit_assoc_item(&mut self, item: &ast::AssocItem, ctxt: AssocCtxt) {
+        self.resolve_doc_links_local(&item.attrs);
+        visit::walk_assoc_item(self, item, ctxt)
+    }
+
+    fn visit_foreign_item(&mut self, item: &ast::ForeignItem) {
+        self.resolve_doc_links_local(&item.attrs);
+        visit::walk_foreign_item(self, item)
+    }
+
+    fn visit_variant(&mut self, v: &ast::Variant) {
+        self.resolve_doc_links_local(&v.attrs);
+        visit::walk_variant(self, v)
+    }
+
+    fn visit_field_def(&mut self, field: &ast::FieldDef) {
+        self.resolve_doc_links_local(&field.attrs);
+        visit::walk_field_def(self, field)
+    }
+
+    fn visit_block(&mut self, block: &ast::Block) {
+        let old_macro_rules = self.parent_scope.macro_rules;
+        visit::walk_block(self, block);
+        self.parent_scope.macro_rules = old_macro_rules;
+    }
+
+    // NOTE: if doc-comments are ever allowed on other nodes (e.g. function parameters),
+    // then this will have to implement other visitor methods too.
+}
diff --git a/src/librustdoc/passes/collect_trait_impls.rs b/src/librustdoc/passes/collect_trait_impls.rs
new file mode 100644
index 000000000..6b699c790
--- /dev/null
+++ b/src/librustdoc/passes/collect_trait_impls.rs
@@ -0,0 +1,273 @@
+//! Collects trait impls for each item in the crate. For example, if a crate
+//! defines a struct that implements a trait, this pass will note that the
+//! struct implements that trait.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::formats::cache::Cache;
+use crate::visit::DocVisitor;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::{self, DefIdTree};
+use rustc_span::symbol::sym;
+
+pub(crate) const COLLECT_TRAIT_IMPLS: Pass = Pass {
+    name: "collect-trait-impls",
+    run: collect_trait_impls,
+    description: "retrieves trait impls for items in the crate",
+};
+
+pub(crate) fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let synth_impls = cx.sess().time("collect_synthetic_impls", || {
+        let mut synth = SyntheticImplCollector { cx, impls: Vec::new() };
+        synth.visit_crate(&krate);
+        synth.impls
+    });
+
+    let prims: FxHashSet<PrimitiveType> = krate.primitives.iter().map(|p| p.1).collect();
+
+    let crate_items = {
+        let mut coll = ItemCollector::new();
+        cx.sess().time("collect_items_for_trait_impls", || coll.visit_crate(&krate));
+        coll.items
+    };
+
+    let mut new_items_external = Vec::new();
+    let mut new_items_local = Vec::new();
+
+    // External trait impls.
+    cx.with_all_trait_impls(|cx, all_trait_impls| {
+        let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
+        for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
+            inline::build_impl(cx, None, impl_def_id, None, &mut new_items_external);
+        }
+    });
+
+    // Local trait impls.
+    cx.with_all_trait_impls(|cx, all_trait_impls| {
+        let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
+        let mut attr_buf = Vec::new();
+        for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
+            let mut parent = Some(cx.tcx.parent(impl_def_id));
+            while let Some(did) = parent {
+                attr_buf.extend(
+                    cx.tcx
+                        .get_attrs(did, sym::doc)
+                        .filter(|attr| {
+                            if let Some([attr]) = attr.meta_item_list().as_deref() {
+                                attr.has_name(sym::cfg)
+                            } else {
+                                false
+                            }
+                        })
+                        .cloned(),
+                );
+                parent = cx.tcx.opt_parent(did);
+            }
+            inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items_local);
+            attr_buf.clear();
+        }
+    });
+
+    cx.tcx.sess.prof.generic_activity("build_primitive_trait_impls").run(|| {
+        for def_id in PrimitiveType::all_impls(cx.tcx) {
+            // Try to inline primitive impls from other crates.
+            if !def_id.is_local() {
+                inline::build_impl(cx, None, def_id, None, &mut new_items_external);
+            }
+        }
+        for (prim, did) in PrimitiveType::primitive_locations(cx.tcx) {
+            // Do not calculate blanket impl list for docs that are not going to be rendered.
+            // While the `impl` blocks themselves are only in `libcore`, the module with `doc`
+            // attached is directly included in `libstd` as well.
+            let tcx = cx.tcx;
+            if did.is_local() {
+                for def_id in prim.impls(tcx).filter(|def_id| {
+                    // Avoid including impl blocks with filled-in generics.
+                    // https://github.com/rust-lang/rust/issues/94937
+                    //
+                    // FIXME(notriddle): https://github.com/rust-lang/rust/issues/97129
+                    //
+                    // This tactic of using inherent impl blocks for getting
+                    // auto traits and blanket impls is a hack. What we really
+                    // want is to check if `[T]` impls `Send`, which has
+                    // nothing to do with the inherent impl.
+                    //
+                    // Rustdoc currently uses these `impl` block as a source of
+                    // the `Ty`, as well as the `ParamEnv`, `SubstsRef`, and
+                    // `Generics`. To avoid relying on the `impl` block, these
+                    // things would need to be created from wholecloth, in a
+                    // form that is valid for use in type inference.
+                    let ty = tcx.type_of(def_id);
+                    match ty.kind() {
+                        ty::Slice(ty)
+                        | ty::Ref(_, ty, _)
+                        | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
+                            matches!(ty.kind(), ty::Param(..))
+                        }
+                        ty::Tuple(tys) => tys.iter().all(|ty| matches!(ty.kind(), ty::Param(..))),
+                        _ => true,
+                    }
+                }) {
+                    let impls = get_auto_trait_and_blanket_impls(cx, def_id);
+                    new_items_external.extend(impls.filter(|i| cx.inlined.insert(i.item_id)));
+                }
+            }
+        }
+    });
+
+    let mut cleaner = BadImplStripper { prims, items: crate_items, cache: &cx.cache };
+    let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
+
+    // Follow all `Deref` targets of included items and recursively add them as valid
+    fn add_deref_target(
+        cx: &DocContext<'_>,
+        map: &FxHashMap<DefId, &Type>,
+        cleaner: &mut BadImplStripper<'_>,
+        targets: &mut FxHashSet<DefId>,
+        type_did: DefId,
+    ) {
+        if let Some(target) = map.get(&type_did) {
+            debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
+            if let Some(target_prim) = target.primitive_type() {
+                cleaner.prims.insert(target_prim);
+            } else if let Some(target_did) = target.def_id(&cx.cache) {
+                // `impl Deref<Target = S> for S`
+                if !targets.insert(target_did) {
+                    // Avoid infinite cycles
+                    return;
+                }
+                cleaner.items.insert(target_did.into());
+                add_deref_target(cx, map, cleaner, targets, target_did);
+            }
+        }
+    }
+
+    // scan through included items ahead of time to splice in Deref targets to the "valid" sets
+    for it in new_items_external.iter().chain(new_items_local.iter()) {
+        if let ImplItem(box Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
+            if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
+                && cleaner.keep_impl(for_, true)
+            {
+                let target = items
+                    .iter()
+                    .find_map(|item| match *item.kind {
+                        AssocTypeItem(ref t, _) => Some(&t.type_),
+                        _ => None,
+                    })
+                    .expect("Deref impl without Target type");
+
+                if let Some(prim) = target.primitive_type() {
+                    cleaner.prims.insert(prim);
+                } else if let Some(did) = target.def_id(&cx.cache) {
+                    cleaner.items.insert(did.into());
+                }
+                if let Some(for_did) = for_.def_id(&cx.cache) {
+                    if type_did_to_deref_target.insert(for_did, target).is_none() {
+                        // Since only the `DefId` portion of the `Type` instances is known to be same for both the
+                        // `Deref` target type and the impl for type positions, this map of types is keyed by
+                        // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
+                        if cleaner.keep_impl_with_def_id(for_did.into()) {
+                            let mut targets = FxHashSet::default();
+                            targets.insert(for_did);
+                            add_deref_target(
+                                cx,
+                                &type_did_to_deref_target,
+                                &mut cleaner,
+                                &mut targets,
+                                for_did,
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    // Filter out external items that are not needed
+    new_items_external.retain(|it| {
+        if let ImplItem(box Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
+            cleaner.keep_impl(
+                for_,
+                trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
+            ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
+                || kind.is_blanket()
+        } else {
+            true
+        }
+    });
+
+    if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
+        items.extend(synth_impls);
+        items.extend(new_items_external);
+        items.extend(new_items_local);
+    } else {
+        panic!("collect-trait-impls can't run");
+    };
+
+    krate
+}
+
+struct SyntheticImplCollector<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+    impls: Vec<Item>,
+}
+
+impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
+    fn visit_item(&mut self, i: &Item) {
+        if i.is_struct() || i.is_enum() || i.is_union() {
+            // FIXME(eddyb) is this `doc(hidden)` check needed?
+            if !self.cx.tcx.is_doc_hidden(i.item_id.expect_def_id()) {
+                self.impls
+                    .extend(get_auto_trait_and_blanket_impls(self.cx, i.item_id.expect_def_id()));
+            }
+        }
+
+        self.visit_item_recur(i)
+    }
+}
+
+#[derive(Default)]
+struct ItemCollector {
+    items: FxHashSet<ItemId>,
+}
+
+impl ItemCollector {
+    fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl DocVisitor for ItemCollector {
+    fn visit_item(&mut self, i: &Item) {
+        self.items.insert(i.item_id);
+
+        self.visit_item_recur(i)
+    }
+}
+
+struct BadImplStripper<'a> {
+    prims: FxHashSet<PrimitiveType>,
+    items: FxHashSet<ItemId>,
+    cache: &'a Cache,
+}
+
+impl<'a> BadImplStripper<'a> {
+    fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
+        if let Generic(_) = ty {
+            // keep impls made on generics
+            true
+        } else if let Some(prim) = ty.primitive_type() {
+            self.prims.contains(&prim)
+        } else if let Some(did) = ty.def_id(self.cache) {
+            is_deref || self.keep_impl_with_def_id(did.into())
+        } else {
+            false
+        }
+    }
+
+    fn keep_impl_with_def_id(&self, item_id: ItemId) -> bool {
+        self.items.contains(&item_id)
+    }
+}
diff --git a/src/librustdoc/passes/html_tags.rs b/src/librustdoc/passes/html_tags.rs
new file mode 100644
index 000000000..f3a3c853c
--- /dev/null
+++ b/src/librustdoc/passes/html_tags.rs
@@ -0,0 +1,303 @@
+//! Detects invalid HTML (like an unclosed `<span>`) in doc comments.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
+
+use pulldown_cmark::{BrokenLink, Event, LinkType, Parser, Tag};
+
+use std::iter::Peekable;
+use std::ops::Range;
+use std::str::CharIndices;
+
+pub(crate) const CHECK_INVALID_HTML_TAGS: Pass = Pass {
+    name: "check-invalid-html-tags",
+    run: check_invalid_html_tags,
+    description: "detects invalid HTML tags in doc comments",
+};
+
+struct InvalidHtmlTagsLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+pub(crate) fn check_invalid_html_tags(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    if cx.tcx.sess.is_nightly_build() {
+        let mut coll = InvalidHtmlTagsLinter { cx };
+        coll.visit_crate(&krate);
+    }
+    krate
+}
+
+const ALLOWED_UNCLOSED: &[&str] = &[
+    "area", "base", "br", "col", "embed", "hr", "img", "input", "keygen", "link", "meta", "param",
+    "source", "track", "wbr",
+];
+
+fn drop_tag(
+    tags: &mut Vec<(String, Range<usize>)>,
+    tag_name: String,
+    range: Range<usize>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let tag_name_low = tag_name.to_lowercase();
+    if let Some(pos) = tags.iter().rposition(|(t, _)| t.to_lowercase() == tag_name_low) {
+        // If the tag is nested inside a "<script>" or a "<style>" tag, no warning should
+        // be emitted.
+        let should_not_warn = tags.iter().take(pos + 1).any(|(at, _)| {
+            let at = at.to_lowercase();
+            at == "script" || at == "style"
+        });
+        for (last_tag_name, last_tag_span) in tags.drain(pos + 1..) {
+            if should_not_warn {
+                continue;
+            }
+            let last_tag_name_low = last_tag_name.to_lowercase();
+            if ALLOWED_UNCLOSED.contains(&last_tag_name_low.as_str()) {
+                continue;
+            }
+            // `tags` is used as a queue, meaning that everything after `pos` is included inside it.
+            // So `<h2><h3></h2>` will look like `["h2", "h3"]`. So when closing `h2`, we will still
+            // have `h3`, meaning the tag wasn't closed as it should have.
+            f(&format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span, true);
+        }
+        // Remove the `tag_name` that was originally closed
+        tags.pop();
+    } else {
+        // It can happen for example in this case: `<h2></script></h2>` (the `h2` tag isn't required
+        // but it helps for the visualization).
+        f(&format!("unopened HTML tag `{}`", tag_name), &range, false);
+    }
+}
+
+fn extract_path_backwards(text: &str, end_pos: usize) -> Option<usize> {
+    use rustc_lexer::{is_id_continue, is_id_start};
+    let mut current_pos = end_pos;
+    loop {
+        if current_pos >= 2 && text[..current_pos].ends_with("::") {
+            current_pos -= 2;
+        }
+        let new_pos = text[..current_pos]
+            .char_indices()
+            .rev()
+            .take_while(|(_, c)| is_id_start(*c) || is_id_continue(*c))
+            .reduce(|_accum, item| item)
+            .and_then(|(new_pos, c)| is_id_start(c).then_some(new_pos));
+        if let Some(new_pos) = new_pos {
+            if current_pos != new_pos {
+                current_pos = new_pos;
+                continue;
+            }
+        }
+        break;
+    }
+    if current_pos == end_pos { None } else { Some(current_pos) }
+}
+
+fn is_valid_for_html_tag_name(c: char, is_empty: bool) -> bool {
+    // https://spec.commonmark.org/0.30/#raw-html
+    //
+    // > A tag name consists of an ASCII letter followed by zero or more ASCII letters, digits, or
+    // > hyphens (-).
+    c.is_ascii_alphabetic() || !is_empty && (c == '-' || c.is_ascii_digit())
+}
+
+fn extract_html_tag(
+    tags: &mut Vec<(String, Range<usize>)>,
+    text: &str,
+    range: &Range<usize>,
+    start_pos: usize,
+    iter: &mut Peekable<CharIndices<'_>>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let mut tag_name = String::new();
+    let mut is_closing = false;
+    let mut prev_pos = start_pos;
+
+    loop {
+        let (pos, c) = match iter.peek() {
+            Some((pos, c)) => (*pos, *c),
+            // In case we reached the of the doc comment, we want to check that it's an
+            // unclosed HTML tag. For example "/// <h3".
+            None => (prev_pos, '\0'),
+        };
+        prev_pos = pos;
+        // Checking if this is a closing tag (like `</a>` for `<a>`).
+        if c == '/' && tag_name.is_empty() {
+            is_closing = true;
+        } else if is_valid_for_html_tag_name(c, tag_name.is_empty()) {
+            tag_name.push(c);
+        } else {
+            if !tag_name.is_empty() {
+                let mut r = Range { start: range.start + start_pos, end: range.start + pos };
+                if c == '>' {
+                    // In case we have a tag without attribute, we can consider the span to
+                    // refer to it fully.
+                    r.end += 1;
+                }
+                if is_closing {
+                    // In case we have "</div >" or even "</div         >".
+                    if c != '>' {
+                        if !c.is_whitespace() {
+                            // It seems like it's not a valid HTML tag.
+                            break;
+                        }
+                        let mut found = false;
+                        for (new_pos, c) in text[pos..].char_indices() {
+                            if !c.is_whitespace() {
+                                if c == '>' {
+                                    r.end = range.start + new_pos + 1;
+                                    found = true;
+                                }
+                                break;
+                            }
+                        }
+                        if !found {
+                            break;
+                        }
+                    }
+                    drop_tag(tags, tag_name, r, f);
+                } else {
+                    tags.push((tag_name, r));
+                }
+            }
+            break;
+        }
+        iter.next();
+    }
+}
+
+fn extract_tags(
+    tags: &mut Vec<(String, Range<usize>)>,
+    text: &str,
+    range: Range<usize>,
+    is_in_comment: &mut Option<Range<usize>>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let mut iter = text.char_indices().peekable();
+
+    while let Some((start_pos, c)) = iter.next() {
+        if is_in_comment.is_some() {
+            if text[start_pos..].starts_with("-->") {
+                *is_in_comment = None;
+            }
+        } else if c == '<' {
+            if text[start_pos..].starts_with("<!--") {
+                // We skip the "!--" part. (Once `advance_by` is stable, might be nice to use it!)
+                iter.next();
+                iter.next();
+                iter.next();
+                *is_in_comment = Some(Range {
+                    start: range.start + start_pos,
+                    end: range.start + start_pos + 3,
+                });
+            } else {
+                extract_html_tag(tags, text, &range, start_pos, &mut iter, f);
+            }
+        }
+    }
+}
+
+impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let tcx = self.cx.tcx;
+        let Some(hir_id) = DocContext::as_local_hir_id(tcx, item.item_id)
+        // If non-local, no need to check anything.
+        else { return };
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        if !dox.is_empty() {
+            let report_diag = |msg: &str, range: &Range<usize>, is_open_tag: bool| {
+                let sp = match super::source_span_for_markdown_range(tcx, &dox, range, &item.attrs)
+                {
+                    Some(sp) => sp,
+                    None => item.attr_span(tcx),
+                };
+                tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, |lint| {
+                    use rustc_lint_defs::Applicability;
+                    let mut diag = lint.build(msg);
+                    // If a tag looks like `<this>`, it might actually be a generic.
+                    // We don't try to detect stuff `<like, this>` because that's not valid HTML,
+                    // and we don't try to detect stuff `<like this>` because that's not valid Rust.
+                    if let Some(Some(generics_start)) = (is_open_tag
+                        && dox[..range.end].ends_with('>'))
+                    .then(|| extract_path_backwards(&dox, range.start))
+                    {
+                        let generics_sp = match super::source_span_for_markdown_range(
+                            tcx,
+                            &dox,
+                            &(generics_start..range.end),
+                            &item.attrs,
+                        ) {
+                            Some(sp) => sp,
+                            None => item.attr_span(tcx),
+                        };
+                        // multipart form is chosen here because ``Vec<i32>`` would be confusing.
+                        diag.multipart_suggestion(
+                            "try marking as source code",
+                            vec![
+                                (generics_sp.shrink_to_lo(), String::from("`")),
+                                (generics_sp.shrink_to_hi(), String::from("`")),
+                            ],
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
+                    diag.emit()
+                });
+            };
+
+            let mut tags = Vec::new();
+            let mut is_in_comment = None;
+            let mut in_code_block = false;
+
+            let link_names = item.link_names(&self.cx.cache);
+
+            let mut replacer = |broken_link: BrokenLink<'_>| {
+                if let Some(link) =
+                    link_names.iter().find(|link| *link.original_text == *broken_link.reference)
+                {
+                    Some((link.href.as_str().into(), link.new_text.as_str().into()))
+                } else if matches!(
+                    &broken_link.link_type,
+                    LinkType::Reference | LinkType::ReferenceUnknown
+                ) {
+                    // If the link is shaped [like][this], suppress any broken HTML in the [this] part.
+                    // The `broken_intra_doc_links` will report typos in there anyway.
+                    Some((
+                        broken_link.reference.to_string().into(),
+                        broken_link.reference.to_string().into(),
+                    ))
+                } else {
+                    None
+                }
+            };
+
+            let p =
+                Parser::new_with_broken_link_callback(&dox, main_body_opts(), Some(&mut replacer))
+                    .into_offset_iter();
+
+            for (event, range) in p {
+                match event {
+                    Event::Start(Tag::CodeBlock(_)) => in_code_block = true,
+                    Event::Html(text) | Event::Text(text) if !in_code_block => {
+                        extract_tags(&mut tags, &text, range, &mut is_in_comment, &report_diag)
+                    }
+                    Event::End(Tag::CodeBlock(_)) => in_code_block = false,
+                    _ => {}
+                }
+            }
+
+            for (tag, range) in tags.iter().filter(|(t, _)| {
+                let t = t.to_lowercase();
+                !ALLOWED_UNCLOSED.contains(&t.as_str())
+            }) {
+                report_diag(&format!("unclosed HTML tag `{}`", tag), range, true);
+            }
+
+            if let Some(range) = is_in_comment {
+                report_diag("Unclosed HTML comment", &range, false);
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
diff --git a/src/librustdoc/passes/mod.rs b/src/librustdoc/passes/mod.rs
new file mode 100644
index 000000000..f81b38ea3
--- /dev/null
+++ b/src/librustdoc/passes/mod.rs
@@ -0,0 +1,212 @@
+//! Contains information about "passes", used to modify crate information during the documentation
+//! process.
+
+use rustc_middle::ty::TyCtxt;
+use rustc_span::{InnerSpan, Span, DUMMY_SP};
+use std::ops::Range;
+
+use self::Condition::*;
+use crate::clean::{self, DocFragmentKind};
+use crate::core::DocContext;
+
+mod stripper;
+pub(crate) use stripper::*;
+
+mod bare_urls;
+pub(crate) use self::bare_urls::CHECK_BARE_URLS;
+
+mod strip_hidden;
+pub(crate) use self::strip_hidden::STRIP_HIDDEN;
+
+mod strip_private;
+pub(crate) use self::strip_private::STRIP_PRIVATE;
+
+mod strip_priv_imports;
+pub(crate) use self::strip_priv_imports::STRIP_PRIV_IMPORTS;
+
+mod propagate_doc_cfg;
+pub(crate) use self::propagate_doc_cfg::PROPAGATE_DOC_CFG;
+
+pub(crate) mod collect_intra_doc_links;
+pub(crate) use self::collect_intra_doc_links::COLLECT_INTRA_DOC_LINKS;
+
+mod check_doc_test_visibility;
+pub(crate) use self::check_doc_test_visibility::CHECK_DOC_TEST_VISIBILITY;
+
+mod collect_trait_impls;
+pub(crate) use self::collect_trait_impls::COLLECT_TRAIT_IMPLS;
+
+mod check_code_block_syntax;
+pub(crate) use self::check_code_block_syntax::CHECK_CODE_BLOCK_SYNTAX;
+
+mod calculate_doc_coverage;
+pub(crate) use self::calculate_doc_coverage::CALCULATE_DOC_COVERAGE;
+
+mod html_tags;
+pub(crate) use self::html_tags::CHECK_INVALID_HTML_TAGS;
+
+/// A single pass over the cleaned documentation.
+///
+/// Runs in the compiler context, so it has access to types and traits and the like.
+#[derive(Copy, Clone)]
+pub(crate) struct Pass {
+    pub(crate) name: &'static str,
+    pub(crate) run: fn(clean::Crate, &mut DocContext<'_>) -> clean::Crate,
+    pub(crate) description: &'static str,
+}
+
+/// In a list of passes, a pass that may or may not need to be run depending on options.
+#[derive(Copy, Clone)]
+pub(crate) struct ConditionalPass {
+    pub(crate) pass: Pass,
+    pub(crate) condition: Condition,
+}
+
+/// How to decide whether to run a conditional pass.
+#[derive(Copy, Clone)]
+pub(crate) enum Condition {
+    Always,
+    /// When `--document-private-items` is passed.
+    WhenDocumentPrivate,
+    /// When `--document-private-items` is not passed.
+    WhenNotDocumentPrivate,
+    /// When `--document-hidden-items` is not passed.
+    WhenNotDocumentHidden,
+}
+
+/// The full list of passes.
+pub(crate) const PASSES: &[Pass] = &[
+    CHECK_DOC_TEST_VISIBILITY,
+    STRIP_HIDDEN,
+    STRIP_PRIVATE,
+    STRIP_PRIV_IMPORTS,
+    PROPAGATE_DOC_CFG,
+    COLLECT_INTRA_DOC_LINKS,
+    CHECK_CODE_BLOCK_SYNTAX,
+    COLLECT_TRAIT_IMPLS,
+    CALCULATE_DOC_COVERAGE,
+    CHECK_INVALID_HTML_TAGS,
+    CHECK_BARE_URLS,
+];
+
+/// The list of passes run by default.
+pub(crate) const DEFAULT_PASSES: &[ConditionalPass] = &[
+    ConditionalPass::always(COLLECT_TRAIT_IMPLS),
+    ConditionalPass::always(CHECK_DOC_TEST_VISIBILITY),
+    ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
+    ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
+    ConditionalPass::new(STRIP_PRIV_IMPORTS, WhenDocumentPrivate),
+    ConditionalPass::always(COLLECT_INTRA_DOC_LINKS),
+    ConditionalPass::always(CHECK_CODE_BLOCK_SYNTAX),
+    ConditionalPass::always(CHECK_INVALID_HTML_TAGS),
+    ConditionalPass::always(PROPAGATE_DOC_CFG),
+    ConditionalPass::always(CHECK_BARE_URLS),
+];
+
+/// The list of default passes run when `--doc-coverage` is passed to rustdoc.
+pub(crate) const COVERAGE_PASSES: &[ConditionalPass] = &[
+    ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
+    ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
+    ConditionalPass::always(CALCULATE_DOC_COVERAGE),
+];
+
+impl ConditionalPass {
+    pub(crate) const fn always(pass: Pass) -> Self {
+        Self::new(pass, Always)
+    }
+
+    pub(crate) const fn new(pass: Pass, condition: Condition) -> Self {
+        ConditionalPass { pass, condition }
+    }
+}
+
+/// Returns the given default set of passes.
+pub(crate) fn defaults(show_coverage: bool) -> &'static [ConditionalPass] {
+    if show_coverage { COVERAGE_PASSES } else { DEFAULT_PASSES }
+}
+
+/// Returns a span encompassing all the given attributes.
+pub(crate) fn span_of_attrs(attrs: &clean::Attributes) -> Option<Span> {
+    if attrs.doc_strings.is_empty() {
+        return None;
+    }
+    let start = attrs.doc_strings[0].span;
+    if start == DUMMY_SP {
+        return None;
+    }
+    let end = attrs.doc_strings.last().expect("no doc strings provided").span;
+    Some(start.to(end))
+}
+
+/// Attempts to match a range of bytes from parsed markdown to a `Span` in the source code.
+///
+/// This method will return `None` if we cannot construct a span from the source map or if the
+/// attributes are not all sugared doc comments. It's difficult to calculate the correct span in
+/// that case due to escaping and other source features.
+pub(crate) fn source_span_for_markdown_range(
+    tcx: TyCtxt<'_>,
+    markdown: &str,
+    md_range: &Range<usize>,
+    attrs: &clean::Attributes,
+) -> Option<Span> {
+    let is_all_sugared_doc =
+        attrs.doc_strings.iter().all(|frag| frag.kind == DocFragmentKind::SugaredDoc);
+
+    if !is_all_sugared_doc {
+        return None;
+    }
+
+    let snippet = tcx.sess.source_map().span_to_snippet(span_of_attrs(attrs)?).ok()?;
+
+    let starting_line = markdown[..md_range.start].matches('\n').count();
+    let ending_line = starting_line + markdown[md_range.start..md_range.end].matches('\n').count();
+
+    // We use `split_terminator('\n')` instead of `lines()` when counting bytes so that we treat
+    // CRLF and LF line endings the same way.
+    let mut src_lines = snippet.split_terminator('\n');
+    let md_lines = markdown.split_terminator('\n');
+
+    // The number of bytes from the source span to the markdown span that are not part
+    // of the markdown, like comment markers.
+    let mut start_bytes = 0;
+    let mut end_bytes = 0;
+
+    'outer: for (line_no, md_line) in md_lines.enumerate() {
+        loop {
+            let source_line = src_lines.next()?;
+            match source_line.find(md_line) {
+                Some(offset) => {
+                    if line_no == starting_line {
+                        start_bytes += offset;
+
+                        if starting_line == ending_line {
+                            break 'outer;
+                        }
+                    } else if line_no == ending_line {
+                        end_bytes += offset;
+                        break 'outer;
+                    } else if line_no < starting_line {
+                        start_bytes += source_line.len() - md_line.len();
+                    } else {
+                        end_bytes += source_line.len() - md_line.len();
+                    }
+                    break;
+                }
+                None => {
+                    // Since this is a source line that doesn't include a markdown line,
+                    // we have to count the newline that we split from earlier.
+                    if line_no <= starting_line {
+                        start_bytes += source_line.len() + 1;
+                    } else {
+                        end_bytes += source_line.len() + 1;
+                    }
+                }
+            }
+        }
+    }
+
+    Some(span_of_attrs(attrs)?.from_inner(InnerSpan::new(
+        md_range.start + start_bytes,
+        md_range.end + start_bytes + end_bytes,
+    )))
+}
diff --git a/src/librustdoc/passes/propagate_doc_cfg.rs b/src/librustdoc/passes/propagate_doc_cfg.rs
new file mode 100644
index 000000000..0c5d83655
--- /dev/null
+++ b/src/librustdoc/passes/propagate_doc_cfg.rs
@@ -0,0 +1,45 @@
+//! Propagates [`#[doc(cfg(...))]`](https://github.com/rust-lang/rust/issues/43781) to child items.
+use std::sync::Arc;
+
+use crate::clean::cfg::Cfg;
+use crate::clean::{Crate, Item};
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::Pass;
+
+pub(crate) const PROPAGATE_DOC_CFG: Pass = Pass {
+    name: "propagate-doc-cfg",
+    run: propagate_doc_cfg,
+    description: "propagates `#[doc(cfg(...))]` to child items",
+};
+
+pub(crate) fn propagate_doc_cfg(cr: Crate, _: &mut DocContext<'_>) -> Crate {
+    CfgPropagator { parent_cfg: None }.fold_crate(cr)
+}
+
+struct CfgPropagator {
+    parent_cfg: Option<Arc<Cfg>>,
+}
+
+impl DocFolder for CfgPropagator {
+    fn fold_item(&mut self, mut item: Item) -> Option<Item> {
+        let old_parent_cfg = self.parent_cfg.clone();
+
+        let new_cfg = match (self.parent_cfg.take(), item.cfg.take()) {
+            (None, None) => None,
+            (Some(rc), None) | (None, Some(rc)) => Some(rc),
+            (Some(mut a), Some(b)) => {
+                let b = Arc::try_unwrap(b).unwrap_or_else(|rc| Cfg::clone(&rc));
+                *Arc::make_mut(&mut a) &= b;
+                Some(a)
+            }
+        };
+        self.parent_cfg = new_cfg.clone();
+        item.cfg = new_cfg;
+
+        let result = self.fold_item_recur(item);
+        self.parent_cfg = old_parent_cfg;
+
+        Some(result)
+    }
+}
diff --git a/src/librustdoc/passes/strip_hidden.rs b/src/librustdoc/passes/strip_hidden.rs
new file mode 100644
index 000000000..533e2ce46
--- /dev/null
+++ b/src/librustdoc/passes/strip_hidden.rs
@@ -0,0 +1,68 @@
+//! Strip all doc(hidden) items from the output.
+use rustc_span::symbol::sym;
+use std::mem;
+
+use crate::clean;
+use crate::clean::{Item, ItemIdSet, NestedAttributesExt};
+use crate::core::DocContext;
+use crate::fold::{strip_item, DocFolder};
+use crate::passes::{ImplStripper, Pass};
+
+pub(crate) const STRIP_HIDDEN: Pass = Pass {
+    name: "strip-hidden",
+    run: strip_hidden,
+    description: "strips all `#[doc(hidden)]` items from the output",
+};
+
+/// Strip items marked `#[doc(hidden)]`
+pub(crate) fn strip_hidden(krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
+    let mut retained = ItemIdSet::default();
+
+    // strip all #[doc(hidden)] items
+    let krate = {
+        let mut stripper = Stripper { retained: &mut retained, update_retained: true };
+        stripper.fold_crate(krate)
+    };
+
+    // strip all impls referencing stripped items
+    let mut stripper = ImplStripper { retained: &retained, cache: &cx.cache };
+    stripper.fold_crate(krate)
+}
+
+struct Stripper<'a> {
+    retained: &'a mut ItemIdSet,
+    update_retained: bool,
+}
+
+impl<'a> DocFolder for Stripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        if i.attrs.lists(sym::doc).has_word(sym::hidden) {
+            debug!("strip_hidden: stripping {:?} {:?}", i.type_(), i.name);
+            // Use a dedicated hidden item for fields, variants, and modules.
+            // We need to keep private fields and variants, so that the docs
+            // can show a placeholder "// some variants omitted". We need to keep
+            // private modules, because they can contain impl blocks, and impl
+            // block privacy is inherited from the type and trait, not from the
+            // module it's defined in. Both of these are marked "stripped," and
+            // not included in the final docs, but since they still have an effect
+            // on the final doc, cannot be completely removed from the Clean IR.
+            match *i.kind {
+                clean::StructFieldItem(..) | clean::ModuleItem(..) | clean::VariantItem(..) => {
+                    // We need to recurse into stripped modules to
+                    // strip things like impl methods but when doing so
+                    // we must not add any items to the `retained` set.
+                    let old = mem::replace(&mut self.update_retained, false);
+                    let ret = strip_item(self.fold_item_recur(i));
+                    self.update_retained = old;
+                    return Some(ret);
+                }
+                _ => return None,
+            }
+        } else {
+            if self.update_retained {
+                self.retained.insert(i.item_id);
+            }
+        }
+        Some(self.fold_item_recur(i))
+    }
+}
diff --git a/src/librustdoc/passes/strip_priv_imports.rs b/src/librustdoc/passes/strip_priv_imports.rs
new file mode 100644
index 000000000..85be8fa10
--- /dev/null
+++ b/src/librustdoc/passes/strip_priv_imports.rs
@@ -0,0 +1,16 @@
+//! Strips all private import statements (use, extern crate) from a
+//! crate.
+use crate::clean;
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::{ImportStripper, Pass};
+
+pub(crate) const STRIP_PRIV_IMPORTS: Pass = Pass {
+    name: "strip-priv-imports",
+    run: strip_priv_imports,
+    description: "strips all private import statements (`use`, `extern crate`) from a crate",
+};
+
+pub(crate) fn strip_priv_imports(krate: clean::Crate, _: &mut DocContext<'_>) -> clean::Crate {
+    ImportStripper.fold_crate(krate)
+}
diff --git a/src/librustdoc/passes/strip_private.rs b/src/librustdoc/passes/strip_private.rs
new file mode 100644
index 000000000..9ba841a31
--- /dev/null
+++ b/src/librustdoc/passes/strip_private.rs
@@ -0,0 +1,35 @@
+//! Strip all private items from the output. Additionally implies strip_priv_imports.
+//! Basically, the goal is to remove items that are not relevant for public documentation.
+use crate::clean::{self, ItemIdSet};
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::{ImplStripper, ImportStripper, Pass, Stripper};
+
+pub(crate) const STRIP_PRIVATE: Pass = Pass {
+    name: "strip-private",
+    run: strip_private,
+    description: "strips all private items from a crate which cannot be seen externally, \
+                  implies strip-priv-imports",
+};
+
+/// Strip private items from the point of view of a crate or externally from a
+/// crate, specified by the `xcrate` flag.
+pub(crate) fn strip_private(mut krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
+    // This stripper collects all *retained* nodes.
+    let mut retained = ItemIdSet::default();
+
+    // strip all private items
+    {
+        let mut stripper = Stripper {
+            retained: &mut retained,
+            access_levels: &cx.cache.access_levels,
+            update_retained: true,
+            is_json_output: cx.output_format.is_json() && !cx.show_coverage,
+        };
+        krate = ImportStripper.fold_crate(stripper.fold_crate(krate));
+    }
+
+    // strip all impls referencing private items
+    let mut stripper = ImplStripper { retained: &retained, cache: &cx.cache };
+    stripper.fold_crate(krate)
+}
diff --git a/src/librustdoc/passes/stripper.rs b/src/librustdoc/passes/stripper.rs
new file mode 100644
index 000000000..0d419042a
--- /dev/null
+++ b/src/librustdoc/passes/stripper.rs
@@ -0,0 +1,188 @@
+//! A collection of utility functions for the `strip_*` passes.
+use rustc_hir::def_id::DefId;
+use rustc_middle::middle::privacy::AccessLevels;
+use std::mem;
+
+use crate::clean::{self, Item, ItemId, ItemIdSet};
+use crate::fold::{strip_item, DocFolder};
+use crate::formats::cache::Cache;
+
+pub(crate) struct Stripper<'a> {
+    pub(crate) retained: &'a mut ItemIdSet,
+    pub(crate) access_levels: &'a AccessLevels<DefId>,
+    pub(crate) update_retained: bool,
+    pub(crate) is_json_output: bool,
+}
+
+impl<'a> Stripper<'a> {
+    // We need to handle this differently for the JSON output because some non exported items could
+    // be used in public API. And so, we need these items as well. `is_exported` only checks if they
+    // are in the public API, which is not enough.
+    #[inline]
+    fn is_item_reachable(&self, item_id: ItemId) -> bool {
+        if self.is_json_output {
+            self.access_levels.is_reachable(item_id.expect_def_id())
+        } else {
+            self.access_levels.is_exported(item_id.expect_def_id())
+        }
+    }
+}
+
+impl<'a> DocFolder for Stripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        match *i.kind {
+            clean::StrippedItem(..) => {
+                // We need to recurse into stripped modules to strip things
+                // like impl methods but when doing so we must not add any
+                // items to the `retained` set.
+                debug!("Stripper: recursing into stripped {:?} {:?}", i.type_(), i.name);
+                let old = mem::replace(&mut self.update_retained, false);
+                let ret = self.fold_item_recur(i);
+                self.update_retained = old;
+                return Some(ret);
+            }
+            // These items can all get re-exported
+            clean::OpaqueTyItem(..)
+            | clean::TypedefItem(..)
+            | clean::StaticItem(..)
+            | clean::StructItem(..)
+            | clean::EnumItem(..)
+            | clean::TraitItem(..)
+            | clean::FunctionItem(..)
+            | clean::VariantItem(..)
+            | clean::MethodItem(..)
+            | clean::ForeignFunctionItem(..)
+            | clean::ForeignStaticItem(..)
+            | clean::ConstantItem(..)
+            | clean::UnionItem(..)
+            | clean::AssocConstItem(..)
+            | clean::AssocTypeItem(..)
+            | clean::TraitAliasItem(..)
+            | clean::MacroItem(..)
+            | clean::ForeignTypeItem => {
+                let item_id = i.item_id;
+                if item_id.is_local() && !self.is_item_reachable(item_id) {
+                    debug!("Stripper: stripping {:?} {:?}", i.type_(), i.name);
+                    return None;
+                }
+            }
+
+            clean::StructFieldItem(..) => {
+                if !i.visibility.is_public() {
+                    return Some(strip_item(i));
+                }
+            }
+
+            clean::ModuleItem(..) => {
+                if i.item_id.is_local() && !i.visibility.is_public() {
+                    debug!("Stripper: stripping module {:?}", i.name);
+                    let old = mem::replace(&mut self.update_retained, false);
+                    let ret = strip_item(self.fold_item_recur(i));
+                    self.update_retained = old;
+                    return Some(ret);
+                }
+            }
+
+            // handled in the `strip-priv-imports` pass
+            clean::ExternCrateItem { .. } | clean::ImportItem(..) => {}
+
+            clean::ImplItem(..) => {}
+
+            // tymethods etc. have no control over privacy
+            clean::TyMethodItem(..) | clean::TyAssocConstItem(..) | clean::TyAssocTypeItem(..) => {}
+
+            // Proc-macros are always public
+            clean::ProcMacroItem(..) => {}
+
+            // Primitives are never stripped
+            clean::PrimitiveItem(..) => {}
+
+            // Keywords are never stripped
+            clean::KeywordItem => {}
+        }
+
+        let fastreturn = match *i.kind {
+            // nothing left to do for traits (don't want to filter their
+            // methods out, visibility controlled by the trait)
+            clean::TraitItem(..) => true,
+
+            // implementations of traits are always public.
+            clean::ImplItem(ref imp) if imp.trait_.is_some() => true,
+            // Variant fields have inherited visibility
+            clean::VariantItem(clean::Variant::Struct(..) | clean::Variant::Tuple(..)) => true,
+            _ => false,
+        };
+
+        let i = if fastreturn {
+            if self.update_retained {
+                self.retained.insert(i.item_id);
+            }
+            return Some(i);
+        } else {
+            self.fold_item_recur(i)
+        };
+
+        if self.update_retained {
+            self.retained.insert(i.item_id);
+        }
+        Some(i)
+    }
+}
+
+/// This stripper discards all impls which reference stripped items
+pub(crate) struct ImplStripper<'a> {
+    pub(crate) retained: &'a ItemIdSet,
+    pub(crate) cache: &'a Cache,
+}
+
+impl<'a> DocFolder for ImplStripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        if let clean::ImplItem(ref imp) = *i.kind {
+            // Impl blocks can be skipped if they are: empty; not a trait impl; and have no
+            // documentation.
+            if imp.trait_.is_none() && imp.items.is_empty() && i.doc_value().is_none() {
+                return None;
+            }
+            if let Some(did) = imp.for_.def_id(self.cache) {
+                if did.is_local() && !imp.for_.is_assoc_ty() && !self.retained.contains(&did.into())
+                {
+                    debug!("ImplStripper: impl item for stripped type; removing");
+                    return None;
+                }
+            }
+            if let Some(did) = imp.trait_.as_ref().map(|t| t.def_id()) {
+                if did.is_local() && !self.retained.contains(&did.into()) {
+                    debug!("ImplStripper: impl item for stripped trait; removing");
+                    return None;
+                }
+            }
+            if let Some(generics) = imp.trait_.as_ref().and_then(|t| t.generics()) {
+                for typaram in generics {
+                    if let Some(did) = typaram.def_id(self.cache) {
+                        if did.is_local() && !self.retained.contains(&did.into()) {
+                            debug!(
+                                "ImplStripper: stripped item in trait's generics; removing impl"
+                            );
+                            return None;
+                        }
+                    }
+                }
+            }
+        }
+        Some(self.fold_item_recur(i))
+    }
+}
+
+/// This stripper discards all private import statements (`use`, `extern crate`)
+pub(crate) struct ImportStripper;
+
+impl DocFolder for ImportStripper {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        match *i.kind {
+            clean::ExternCrateItem { .. } | clean::ImportItem(..) if !i.visibility.is_public() => {
+                None
+            }
+            _ => Some(self.fold_item_recur(i)),
+        }
+    }
+}
diff --git a/src/librustdoc/scrape_examples.rs b/src/librustdoc/scrape_examples.rs
new file mode 100644
index 000000000..0d9684025
--- /dev/null
+++ b/src/librustdoc/scrape_examples.rs
@@ -0,0 +1,359 @@
+//! This module analyzes crates to find call sites that can serve as examples in the documentation.
+
+use crate::clean;
+use crate::config;
+use crate::formats;
+use crate::formats::renderer::FormatRenderer;
+use crate::html::render::Context;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::{
+    self as hir,
+    intravisit::{self, Visitor},
+};
+use rustc_interface::interface;
+use rustc_macros::{Decodable, Encodable};
+use rustc_middle::hir::map::Map;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_serialize::{
+    opaque::{FileEncoder, MemDecoder},
+    Decodable, Encodable,
+};
+use rustc_session::getopts;
+use rustc_span::{
+    def_id::{CrateNum, DefPathHash, LOCAL_CRATE},
+    edition::Edition,
+    BytePos, FileName, SourceFile,
+};
+
+use std::fs;
+use std::path::PathBuf;
+
+#[derive(Debug, Clone)]
+pub(crate) struct ScrapeExamplesOptions {
+    output_path: PathBuf,
+    target_crates: Vec<String>,
+    pub(crate) scrape_tests: bool,
+}
+
+impl ScrapeExamplesOptions {
+    pub(crate) fn new(
+        matches: &getopts::Matches,
+        diag: &rustc_errors::Handler,
+    ) -> Result<Option<Self>, i32> {
+        let output_path = matches.opt_str("scrape-examples-output-path");
+        let target_crates = matches.opt_strs("scrape-examples-target-crate");
+        let scrape_tests = matches.opt_present("scrape-tests");
+        match (output_path, !target_crates.is_empty(), scrape_tests) {
+            (Some(output_path), true, _) => Ok(Some(ScrapeExamplesOptions {
+                output_path: PathBuf::from(output_path),
+                target_crates,
+                scrape_tests,
+            })),
+            (Some(_), false, _) | (None, true, _) => {
+                diag.err("must use --scrape-examples-output-path and --scrape-examples-target-crate together");
+                Err(1)
+            }
+            (None, false, true) => {
+                diag.err("must use --scrape-examples-output-path and --scrape-examples-target-crate with --scrape-tests");
+                Err(1)
+            }
+            (None, false, false) => Ok(None),
+        }
+    }
+}
+
+#[derive(Encodable, Decodable, Debug, Clone)]
+pub(crate) struct SyntaxRange {
+    pub(crate) byte_span: (u32, u32),
+    pub(crate) line_span: (usize, usize),
+}
+
+impl SyntaxRange {
+    fn new(span: rustc_span::Span, file: &SourceFile) -> Option<Self> {
+        let get_pos = |bytepos: BytePos| file.original_relative_byte_pos(bytepos).0;
+        let get_line = |bytepos: BytePos| file.lookup_line(bytepos);
+
+        Some(SyntaxRange {
+            byte_span: (get_pos(span.lo()), get_pos(span.hi())),
+            line_span: (get_line(span.lo())?, get_line(span.hi())?),
+        })
+    }
+}
+
+#[derive(Encodable, Decodable, Debug, Clone)]
+pub(crate) struct CallLocation {
+    pub(crate) call_expr: SyntaxRange,
+    pub(crate) call_ident: SyntaxRange,
+    pub(crate) enclosing_item: SyntaxRange,
+}
+
+impl CallLocation {
+    fn new(
+        expr_span: rustc_span::Span,
+        ident_span: rustc_span::Span,
+        enclosing_item_span: rustc_span::Span,
+        source_file: &SourceFile,
+    ) -> Option<Self> {
+        Some(CallLocation {
+            call_expr: SyntaxRange::new(expr_span, source_file)?,
+            call_ident: SyntaxRange::new(ident_span, source_file)?,
+            enclosing_item: SyntaxRange::new(enclosing_item_span, source_file)?,
+        })
+    }
+}
+
+#[derive(Encodable, Decodable, Debug, Clone)]
+pub(crate) struct CallData {
+    pub(crate) locations: Vec<CallLocation>,
+    pub(crate) url: String,
+    pub(crate) display_name: String,
+    pub(crate) edition: Edition,
+}
+
+pub(crate) type FnCallLocations = FxHashMap<PathBuf, CallData>;
+pub(crate) type AllCallLocations = FxHashMap<DefPathHash, FnCallLocations>;
+
+/// Visitor for traversing a crate and finding instances of function calls.
+struct FindCalls<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    map: Map<'tcx>,
+    cx: Context<'tcx>,
+    target_crates: Vec<CrateNum>,
+    calls: &'a mut AllCallLocations,
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for FindCalls<'a, 'tcx>
+where
+    'tcx: 'a,
+{
+    type NestedFilter = nested_filter::OnlyBodies;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.map
+    }
+
+    fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
+        intravisit::walk_expr(self, ex);
+
+        let tcx = self.tcx;
+
+        // If we visit an item that contains an expression outside a function body,
+        // then we need to exit before calling typeck (which will panic). See
+        // test/run-make/rustdoc-scrape-examples-invalid-expr for an example.
+        let hir = tcx.hir();
+        if hir.maybe_body_owned_by(ex.hir_id.owner).is_none() {
+            return;
+        }
+
+        // Get type of function if expression is a function call
+        let (ty, call_span, ident_span) = match ex.kind {
+            hir::ExprKind::Call(f, _) => {
+                let types = tcx.typeck(ex.hir_id.owner);
+
+                if let Some(ty) = types.node_type_opt(f.hir_id) {
+                    (ty, ex.span, f.span)
+                } else {
+                    trace!("node_type_opt({}) = None", f.hir_id);
+                    return;
+                }
+            }
+            hir::ExprKind::MethodCall(path, _, call_span) => {
+                let types = tcx.typeck(ex.hir_id.owner);
+                let Some(def_id) = types.type_dependent_def_id(ex.hir_id) else {
+                    trace!("type_dependent_def_id({}) = None", ex.hir_id);
+                    return;
+                };
+
+                let ident_span = path.ident.span;
+                (tcx.type_of(def_id), call_span, ident_span)
+            }
+            _ => {
+                return;
+            }
+        };
+
+        // If this span comes from a macro expansion, then the source code may not actually show
+        // a use of the given item, so it would be a poor example. Hence, we skip all uses in macros.
+        if call_span.from_expansion() {
+            trace!("Rejecting expr from macro: {call_span:?}");
+            return;
+        }
+
+        // If the enclosing item has a span coming from a proc macro, then we also don't want to include
+        // the example.
+        let enclosing_item_span = tcx
+            .hir()
+            .span_with_body(tcx.hir().local_def_id_to_hir_id(tcx.hir().get_parent_item(ex.hir_id)));
+        if enclosing_item_span.from_expansion() {
+            trace!("Rejecting expr ({call_span:?}) from macro item: {enclosing_item_span:?}");
+            return;
+        }
+
+        // If the enclosing item doesn't actually enclose the call, this means we probably have a weird
+        // macro issue even though the spans aren't tagged as being from an expansion.
+        if !enclosing_item_span.contains(call_span) {
+            warn!(
+                "Attempted to scrape call at [{call_span:?}] whose enclosing item [{enclosing_item_span:?}] doesn't contain the span of the call."
+            );
+            return;
+        }
+
+        // Similarly for the call w/ the function ident.
+        if !call_span.contains(ident_span) {
+            warn!(
+                "Attempted to scrape call at [{call_span:?}] whose identifier [{ident_span:?}] was not contained in the span of the call."
+            );
+            return;
+        }
+
+        // Save call site if the function resolves to a concrete definition
+        if let ty::FnDef(def_id, _) = ty.kind() {
+            if self.target_crates.iter().all(|krate| *krate != def_id.krate) {
+                trace!("Rejecting expr from crate not being documented: {call_span:?}");
+                return;
+            }
+
+            let source_map = tcx.sess.source_map();
+            let file = source_map.lookup_char_pos(call_span.lo()).file;
+            let file_path = match file.name.clone() {
+                FileName::Real(real_filename) => real_filename.into_local_path(),
+                _ => None,
+            };
+
+            if let Some(file_path) = file_path {
+                let abs_path = match fs::canonicalize(file_path.clone()) {
+                    Ok(abs_path) => abs_path,
+                    Err(_) => {
+                        trace!("Could not canonicalize file path: {}", file_path.display());
+                        return;
+                    }
+                };
+
+                let cx = &self.cx;
+                let clean_span = crate::clean::types::Span::new(call_span);
+                let url = match cx.href_from_span(clean_span, false) {
+                    Some(url) => url,
+                    None => {
+                        trace!(
+                            "Rejecting expr ({call_span:?}) whose clean span ({clean_span:?}) cannot be turned into a link"
+                        );
+                        return;
+                    }
+                };
+
+                let mk_call_data = || {
+                    let display_name = file_path.display().to_string();
+                    let edition = call_span.edition();
+                    CallData { locations: Vec::new(), url, display_name, edition }
+                };
+
+                let fn_key = tcx.def_path_hash(*def_id);
+                let fn_entries = self.calls.entry(fn_key).or_default();
+
+                trace!("Including expr: {:?}", call_span);
+                let enclosing_item_span =
+                    source_map.span_extend_to_prev_char(enclosing_item_span, '\n', false);
+                let location =
+                    match CallLocation::new(call_span, ident_span, enclosing_item_span, &file) {
+                        Some(location) => location,
+                        None => {
+                            trace!("Could not get serializable call location for {call_span:?}");
+                            return;
+                        }
+                    };
+                fn_entries.entry(abs_path).or_insert_with(mk_call_data).locations.push(location);
+            }
+        }
+    }
+}
+
+pub(crate) fn run(
+    krate: clean::Crate,
+    mut renderopts: config::RenderOptions,
+    cache: formats::cache::Cache,
+    tcx: TyCtxt<'_>,
+    options: ScrapeExamplesOptions,
+) -> interface::Result<()> {
+    let inner = move || -> Result<(), String> {
+        // Generates source files for examples
+        renderopts.no_emit_shared = true;
+        let (cx, _) = Context::init(krate, renderopts, cache, tcx).map_err(|e| e.to_string())?;
+
+        // Collect CrateIds corresponding to provided target crates
+        // If two different versions of the crate in the dependency tree, then examples will be collcted from both.
+        let all_crates = tcx
+            .crates(())
+            .iter()
+            .chain([&LOCAL_CRATE])
+            .map(|crate_num| (crate_num, tcx.crate_name(*crate_num)))
+            .collect::<Vec<_>>();
+        let target_crates = options
+            .target_crates
+            .into_iter()
+            .flat_map(|target| all_crates.iter().filter(move |(_, name)| name.as_str() == target))
+            .map(|(crate_num, _)| **crate_num)
+            .collect::<Vec<_>>();
+
+        debug!("All crates in TyCtxt: {all_crates:?}");
+        debug!("Scrape examples target_crates: {target_crates:?}");
+
+        // Run call-finder on all items
+        let mut calls = FxHashMap::default();
+        let mut finder = FindCalls { calls: &mut calls, tcx, map: tcx.hir(), cx, target_crates };
+        tcx.hir().visit_all_item_likes_in_crate(&mut finder);
+
+        // The visitor might have found a type error, which we need to
+        // promote to a fatal error
+        if tcx.sess.diagnostic().has_errors_or_lint_errors().is_some() {
+            return Err(String::from("Compilation failed, aborting rustdoc"));
+        }
+
+        // Sort call locations within a given file in document order
+        for fn_calls in calls.values_mut() {
+            for file_calls in fn_calls.values_mut() {
+                file_calls.locations.sort_by_key(|loc| loc.call_expr.byte_span.0);
+            }
+        }
+
+        // Save output to provided path
+        let mut encoder = FileEncoder::new(options.output_path).map_err(|e| e.to_string())?;
+        calls.encode(&mut encoder);
+        encoder.finish().map_err(|e| e.to_string())?;
+
+        Ok(())
+    };
+
+    if let Err(e) = inner() {
+        tcx.sess.fatal(&e);
+    }
+
+    Ok(())
+}
+
+// Note: the Handler must be passed in explicitly because sess isn't available while parsing options
+pub(crate) fn load_call_locations(
+    with_examples: Vec<String>,
+    diag: &rustc_errors::Handler,
+) -> Result<AllCallLocations, i32> {
+    let inner = || {
+        let mut all_calls: AllCallLocations = FxHashMap::default();
+        for path in with_examples {
+            let bytes = fs::read(&path).map_err(|e| format!("{} (for path {})", e, path))?;
+            let mut decoder = MemDecoder::new(&bytes, 0);
+            let calls = AllCallLocations::decode(&mut decoder);
+
+            for (function, fn_calls) in calls.into_iter() {
+                all_calls.entry(function).or_default().extend(fn_calls.into_iter());
+            }
+        }
+
+        Ok(all_calls)
+    };
+
+    inner().map_err(|e: String| {
+        diag.err(&format!("failed to load examples: {}", e));
+        1
+    })
+}
diff --git a/src/librustdoc/theme.rs b/src/librustdoc/theme.rs
new file mode 100644
index 000000000..0118d7dd2
--- /dev/null
+++ b/src/librustdoc/theme.rs
@@ -0,0 +1,271 @@
+use rustc_data_structures::fx::FxHashSet;
+use std::fs;
+use std::hash::{Hash, Hasher};
+use std::path::Path;
+
+use rustc_errors::Handler;
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Debug, Clone, Eq)]
+pub(crate) struct CssPath {
+    pub(crate) name: String,
+    pub(crate) children: FxHashSet<CssPath>,
+}
+
+// This PartialEq implementation IS NOT COMMUTATIVE!!!
+//
+// The order is very important: the second object must have all first's rules.
+// However, the first is not required to have all of the second's rules.
+impl PartialEq for CssPath {
+    fn eq(&self, other: &CssPath) -> bool {
+        if self.name != other.name {
+            false
+        } else {
+            for child in &self.children {
+                if !other.children.iter().any(|c| child == c) {
+                    return false;
+                }
+            }
+            true
+        }
+    }
+}
+
+impl Hash for CssPath {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.name.hash(state);
+        for x in &self.children {
+            x.hash(state);
+        }
+    }
+}
+
+impl CssPath {
+    fn new(name: String) -> CssPath {
+        CssPath { name, children: FxHashSet::default() }
+    }
+}
+
+/// All variants contain the position they occur.
+#[derive(Debug, Clone, Copy)]
+enum Events {
+    StartLineComment(usize),
+    StartComment(usize),
+    EndComment(usize),
+    InBlock(usize),
+    OutBlock(usize),
+}
+
+impl Events {
+    fn get_pos(&self) -> usize {
+        match *self {
+            Events::StartLineComment(p)
+            | Events::StartComment(p)
+            | Events::EndComment(p)
+            | Events::InBlock(p)
+            | Events::OutBlock(p) => p,
+        }
+    }
+
+    fn is_comment(&self) -> bool {
+        matches!(
+            self,
+            Events::StartLineComment(_) | Events::StartComment(_) | Events::EndComment(_)
+        )
+    }
+}
+
+fn previous_is_line_comment(events: &[Events]) -> bool {
+    matches!(events.last(), Some(&Events::StartLineComment(_)))
+}
+
+fn is_line_comment(pos: usize, v: &[u8], events: &[Events]) -> bool {
+    if let Some(&Events::StartComment(_)) = events.last() {
+        return false;
+    }
+    v[pos + 1] == b'/'
+}
+
+fn load_css_events(v: &[u8]) -> Vec<Events> {
+    let mut pos = 0;
+    let mut events = Vec::with_capacity(100);
+
+    while pos + 1 < v.len() {
+        match v[pos] {
+            b'/' if v[pos + 1] == b'*' => {
+                events.push(Events::StartComment(pos));
+                pos += 1;
+            }
+            b'/' if is_line_comment(pos, v, &events) => {
+                events.push(Events::StartLineComment(pos));
+                pos += 1;
+            }
+            b'\n' if previous_is_line_comment(&events) => {
+                events.push(Events::EndComment(pos));
+            }
+            b'*' if v[pos + 1] == b'/' => {
+                events.push(Events::EndComment(pos + 2));
+                pos += 1;
+            }
+            b'{' if !previous_is_line_comment(&events) => {
+                if let Some(&Events::StartComment(_)) = events.last() {
+                    pos += 1;
+                    continue;
+                }
+                events.push(Events::InBlock(pos + 1));
+            }
+            b'}' if !previous_is_line_comment(&events) => {
+                if let Some(&Events::StartComment(_)) = events.last() {
+                    pos += 1;
+                    continue;
+                }
+                events.push(Events::OutBlock(pos + 1));
+            }
+            _ => {}
+        }
+        pos += 1;
+    }
+    events
+}
+
+fn get_useful_next(events: &[Events], pos: &mut usize) -> Option<Events> {
+    while *pos < events.len() {
+        if !events[*pos].is_comment() {
+            return Some(events[*pos]);
+        }
+        *pos += 1;
+    }
+    None
+}
+
+fn get_previous_positions(events: &[Events], mut pos: usize) -> Vec<usize> {
+    let mut ret = Vec::with_capacity(3);
+
+    ret.push(events[pos].get_pos());
+    if pos > 0 {
+        pos -= 1;
+    }
+    loop {
+        if pos < 1 || !events[pos].is_comment() {
+            let x = events[pos].get_pos();
+            if *ret.last().unwrap() != x {
+                ret.push(x);
+            } else {
+                ret.push(0);
+            }
+            break;
+        }
+        ret.push(events[pos].get_pos());
+        pos -= 1;
+    }
+    if ret.len() & 1 != 0 && events[pos].is_comment() {
+        ret.push(0);
+    }
+    ret.iter().rev().cloned().collect()
+}
+
+fn build_rule(v: &[u8], positions: &[usize]) -> String {
+    minifier::css::minify(
+        &positions
+            .chunks(2)
+            .map(|x| ::std::str::from_utf8(&v[x[0]..x[1]]).unwrap_or(""))
+            .collect::<String>()
+            .trim()
+            .chars()
+            .filter_map(|c| match c {
+                '\n' | '\t' => Some(' '),
+                '/' | '{' | '}' => None,
+                c => Some(c),
+            })
+            .collect::<String>()
+            .split(' ')
+            .filter(|s| !s.is_empty())
+            .intersperse(" ")
+            .collect::<String>(),
+    )
+    .map(|css| css.to_string())
+    .unwrap_or_else(|_| String::new())
+}
+
+fn inner(v: &[u8], events: &[Events], pos: &mut usize) -> FxHashSet<CssPath> {
+    let mut paths = Vec::with_capacity(50);
+
+    while *pos < events.len() {
+        if let Some(Events::OutBlock(_)) = get_useful_next(events, pos) {
+            *pos += 1;
+            break;
+        }
+        if let Some(Events::InBlock(_)) = get_useful_next(events, pos) {
+            paths.push(CssPath::new(build_rule(v, &get_previous_positions(events, *pos))));
+            *pos += 1;
+        }
+        while let Some(Events::InBlock(_)) = get_useful_next(events, pos) {
+            if let Some(ref mut path) = paths.last_mut() {
+                for entry in inner(v, events, pos).iter() {
+                    path.children.insert(entry.clone());
+                }
+            }
+        }
+        if let Some(Events::OutBlock(_)) = get_useful_next(events, pos) {
+            *pos += 1;
+        }
+    }
+    paths.iter().cloned().collect()
+}
+
+pub(crate) fn load_css_paths(v: &[u8]) -> CssPath {
+    let events = load_css_events(v);
+    let mut pos = 0;
+
+    let mut parent = CssPath::new("parent".to_owned());
+    parent.children = inner(v, &events, &mut pos);
+    parent
+}
+
+pub(crate) fn get_differences(against: &CssPath, other: &CssPath, v: &mut Vec<String>) {
+    if against.name == other.name {
+        for child in &against.children {
+            let mut found = false;
+            let mut found_working = false;
+            let mut tmp = Vec::new();
+
+            for other_child in &other.children {
+                if child.name == other_child.name {
+                    if child != other_child {
+                        get_differences(child, other_child, &mut tmp);
+                    } else {
+                        found_working = true;
+                    }
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                v.push(format!("  Missing \"{}\" rule", child.name));
+            } else if !found_working {
+                v.extend(tmp.iter().cloned());
+            }
+        }
+    }
+}
+
+pub(crate) fn test_theme_against<P: AsRef<Path>>(
+    f: &P,
+    against: &CssPath,
+    diag: &Handler,
+) -> (bool, Vec<String>) {
+    let data = match fs::read(f) {
+        Ok(c) => c,
+        Err(e) => {
+            diag.struct_err(&e.to_string()).emit();
+            return (false, vec![]);
+        }
+    };
+
+    let paths = load_css_paths(&data);
+    let mut ret = vec![];
+    get_differences(against, &paths, &mut ret);
+    (true, ret)
+}
diff --git a/src/librustdoc/theme/tests.rs b/src/librustdoc/theme/tests.rs
new file mode 100644
index 000000000..ae8f43c6d
--- /dev/null
+++ b/src/librustdoc/theme/tests.rs
@@ -0,0 +1,117 @@
+use super::*;
+
+#[test]
+fn test_comments_in_rules() {
+    let text = r#"
+rule a {}
+
+rule b, c
+// a line comment
+{}
+
+rule d
+// another line comment
+e {}
+
+rule f/* a multine
+
+comment*/{}
+
+rule g/* another multine
+
+comment*/h
+
+i {}
+
+rule j/*commeeeeent
+
+you like things like "{}" in there? :)
+*/
+end {}"#;
+
+    let against = r#"
+rule a {}
+
+rule b, c {}
+
+rule d e {}
+
+rule f {}
+
+rule gh i {}
+
+rule j end {}
+"#;
+
+    let mut ret = Vec::new();
+    get_differences(
+        &load_css_paths(against.as_bytes()),
+        &load_css_paths(text.as_bytes()),
+        &mut ret,
+    );
+    assert!(ret.is_empty());
+}
+
+#[test]
+fn test_text() {
+    let text = r#"
+a
+/* sdfs
+*/ b
+c // sdf
+d {}
+"#;
+    let paths = load_css_paths(text.as_bytes());
+    assert!(paths.children.contains(&CssPath::new("a b c d".to_owned())));
+}
+
+#[test]
+fn test_comparison() {
+    let x = r#"
+a {
+    b {
+        c {}
+    }
+}
+"#;
+
+    let y = r#"
+a {
+    b {}
+}
+"#;
+
+    let against = load_css_paths(y.as_bytes());
+    let other = load_css_paths(x.as_bytes());
+
+    let mut ret = Vec::new();
+    get_differences(&against, &other, &mut ret);
+    assert!(ret.is_empty());
+    get_differences(&other, &against, &mut ret);
+    assert_eq!(ret, vec!["  Missing \"c\" rule".to_owned()]);
+}
+
+#[test]
+fn check_empty_css() {
+    let events = load_css_events(&[]);
+    assert_eq!(events.len(), 0);
+}
+
+#[test]
+fn check_invalid_css() {
+    let events = load_css_events(b"*");
+    assert_eq!(events.len(), 0);
+}
+
+#[test]
+fn test_with_minification() {
+    let text = include_str!("../html/static/css/themes/dark.css");
+    let minified = minifier::css::minify(&text).expect("CSS minification failed").to_string();
+
+    let against = load_css_paths(text.as_bytes());
+    let other = load_css_paths(minified.as_bytes());
+
+    let mut ret = Vec::new();
+    get_differences(&against, &other, &mut ret);
+    assert!(ret.is_empty());
+}
diff --git a/src/librustdoc/visit.rs b/src/librustdoc/visit.rs
new file mode 100644
index 000000000..0bb41977c
--- /dev/null
+++ b/src/librustdoc/visit.rs
@@ -0,0 +1,72 @@
+use crate::clean::*;
+
+pub(crate) trait DocVisitor: Sized {
+    fn visit_item(&mut self, item: &Item) {
+        self.visit_item_recur(item)
+    }
+
+    /// don't override!
+    fn visit_inner_recur(&mut self, kind: &ItemKind) {
+        match kind {
+            StrippedItem(..) => unreachable!(),
+            ModuleItem(i) => {
+                self.visit_mod(i);
+            }
+            StructItem(i) => i.fields.iter().for_each(|x| self.visit_item(x)),
+            UnionItem(i) => i.fields.iter().for_each(|x| self.visit_item(x)),
+            EnumItem(i) => i.variants.iter().for_each(|x| self.visit_item(x)),
+            TraitItem(i) => i.items.iter().for_each(|x| self.visit_item(x)),
+            ImplItem(i) => i.items.iter().for_each(|x| self.visit_item(x)),
+            VariantItem(i) => match i {
+                Variant::Struct(j) => j.fields.iter().for_each(|x| self.visit_item(x)),
+                Variant::Tuple(fields) => fields.iter().for_each(|x| self.visit_item(x)),
+                Variant::CLike => {}
+            },
+            ExternCrateItem { src: _ }
+            | ImportItem(_)
+            | FunctionItem(_)
+            | TypedefItem(_)
+            | OpaqueTyItem(_)
+            | StaticItem(_)
+            | ConstantItem(_)
+            | TraitAliasItem(_)
+            | TyMethodItem(_)
+            | MethodItem(_, _)
+            | StructFieldItem(_)
+            | ForeignFunctionItem(_)
+            | ForeignStaticItem(_)
+            | ForeignTypeItem
+            | MacroItem(_)
+            | ProcMacroItem(_)
+            | PrimitiveItem(_)
+            | TyAssocConstItem(..)
+            | AssocConstItem(..)
+            | TyAssocTypeItem(..)
+            | AssocTypeItem(..)
+            | KeywordItem => {}
+        }
+    }
+
+    /// don't override!
+    fn visit_item_recur(&mut self, item: &Item) {
+        match &*item.kind {
+            StrippedItem(i) => self.visit_inner_recur(i),
+            _ => self.visit_inner_recur(&item.kind),
+        }
+    }
+
+    fn visit_mod(&mut self, m: &Module) {
+        m.items.iter().for_each(|i| self.visit_item(i))
+    }
+
+    fn visit_crate(&mut self, c: &Crate) {
+        self.visit_item(&c.module);
+
+        // FIXME: make this a simple by-ref for loop once external_traits is cleaned up
+        let external_traits = { std::mem::take(&mut *c.external_traits.borrow_mut()) };
+        for (k, v) in external_traits {
+            v.trait_.items.iter().for_each(|i| self.visit_item(i));
+            c.external_traits.borrow_mut().insert(k, v);
+        }
+    }
+}
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
new file mode 100644
index 000000000..ca7a20bf3
--- /dev/null
+++ b/src/librustdoc/visit_ast.rs
@@ -0,0 +1,396 @@
+//! The Rust AST Visitor. Extracts useful information and massages it into a form
+//! usable for `clean`.
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_hir::Node;
+use rustc_hir::CRATE_HIR_ID;
+use rustc_middle::middle::privacy::AccessLevel;
+use rustc_middle::ty::TyCtxt;
+use rustc_span::def_id::{CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_span::Span;
+
+use std::mem;
+
+use crate::clean::{self, cfg::Cfg, AttributesExt, NestedAttributesExt};
+use crate::core;
+
+/// This module is used to store stuff from Rust's AST in a more convenient
+/// manner (and with prettier names) before cleaning.
+#[derive(Debug)]
+pub(crate) struct Module<'hir> {
+    pub(crate) name: Symbol,
+    pub(crate) where_inner: Span,
+    pub(crate) mods: Vec<Module<'hir>>,
+    pub(crate) id: hir::HirId,
+    // (item, renamed)
+    pub(crate) items: Vec<(&'hir hir::Item<'hir>, Option<Symbol>)>,
+    pub(crate) foreigns: Vec<(&'hir hir::ForeignItem<'hir>, Option<Symbol>)>,
+}
+
+impl Module<'_> {
+    pub(crate) fn new(name: Symbol, id: hir::HirId, where_inner: Span) -> Self {
+        Module { name, id, where_inner, mods: Vec::new(), items: Vec::new(), foreigns: Vec::new() }
+    }
+
+    pub(crate) fn where_outer(&self, tcx: TyCtxt<'_>) -> Span {
+        tcx.hir().span(self.id)
+    }
+}
+
+// FIXME: Should this be replaced with tcx.def_path_str?
+fn def_id_to_path(tcx: TyCtxt<'_>, did: DefId) -> Vec<Symbol> {
+    let crate_name = tcx.crate_name(did.krate);
+    let relative = tcx.def_path(did).data.into_iter().filter_map(|elem| elem.data.get_opt_name());
+    std::iter::once(crate_name).chain(relative).collect()
+}
+
+pub(crate) fn inherits_doc_hidden(tcx: TyCtxt<'_>, mut node: hir::HirId) -> bool {
+    while let Some(id) = tcx.hir().get_enclosing_scope(node) {
+        node = id;
+        if tcx.hir().attrs(node).lists(sym::doc).has_word(sym::hidden) {
+            return true;
+        }
+    }
+    false
+}
+
+// Also, is there some reason that this doesn't use the 'visit'
+// framework from syntax?.
+
+pub(crate) struct RustdocVisitor<'a, 'tcx> {
+    cx: &'a mut core::DocContext<'tcx>,
+    view_item_stack: FxHashSet<hir::HirId>,
+    inlining: bool,
+    /// Are the current module and all of its parents public?
+    inside_public_path: bool,
+    exact_paths: FxHashMap<DefId, Vec<Symbol>>,
+}
+
+impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
+    pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> RustdocVisitor<'a, 'tcx> {
+        // If the root is re-exported, terminate all recursion.
+        let mut stack = FxHashSet::default();
+        stack.insert(hir::CRATE_HIR_ID);
+        RustdocVisitor {
+            cx,
+            view_item_stack: stack,
+            inlining: false,
+            inside_public_path: true,
+            exact_paths: FxHashMap::default(),
+        }
+    }
+
+    fn store_path(&mut self, did: DefId) {
+        let tcx = self.cx.tcx;
+        self.exact_paths.entry(did).or_insert_with(|| def_id_to_path(tcx, did));
+    }
+
+    pub(crate) fn visit(mut self) -> Module<'tcx> {
+        let mut top_level_module = self.visit_mod_contents(
+            hir::CRATE_HIR_ID,
+            self.cx.tcx.hir().root_module(),
+            self.cx.tcx.crate_name(LOCAL_CRATE),
+        );
+
+        // `#[macro_export] macro_rules!` items are reexported at the top level of the
+        // crate, regardless of where they're defined. We want to document the
+        // top level rexport of the macro, not its original definition, since
+        // the rexport defines the path that a user will actually see. Accordingly,
+        // we add the rexport as an item here, and then skip over the original
+        // definition in `visit_item()` below.
+        //
+        // We also skip `#[macro_export] macro_rules!` that have already been inserted,
+        // it can happen if within the same module a `#[macro_export] macro_rules!`
+        // is declared but also a reexport of itself producing two exports of the same
+        // macro in the same module.
+        let mut inserted = FxHashSet::default();
+        for export in self.cx.tcx.module_reexports(CRATE_DEF_ID).unwrap_or(&[]) {
+            if let Res::Def(DefKind::Macro(_), def_id) = export.res {
+                if let Some(local_def_id) = def_id.as_local() {
+                    if self.cx.tcx.has_attr(def_id, sym::macro_export) {
+                        if inserted.insert(def_id) {
+                            let item = self.cx.tcx.hir().expect_item(local_def_id);
+                            top_level_module.items.push((item, None));
+                        }
+                    }
+                }
+            }
+        }
+
+        self.cx.cache.hidden_cfg = self
+            .cx
+            .tcx
+            .hir()
+            .attrs(CRATE_HIR_ID)
+            .iter()
+            .filter(|attr| attr.has_name(sym::doc))
+            .flat_map(|attr| attr.meta_item_list().into_iter().flatten())
+            .filter(|attr| attr.has_name(sym::cfg_hide))
+            .flat_map(|attr| {
+                attr.meta_item_list()
+                    .unwrap_or(&[])
+                    .iter()
+                    .filter_map(|attr| {
+                        Cfg::parse(attr.meta_item()?)
+                            .map_err(|e| self.cx.sess().diagnostic().span_err(e.span, e.msg))
+                            .ok()
+                    })
+                    .collect::<Vec<_>>()
+            })
+            .chain(
+                [Cfg::Cfg(sym::test, None), Cfg::Cfg(sym::doc, None), Cfg::Cfg(sym::doctest, None)]
+                    .into_iter(),
+            )
+            .collect();
+
+        self.cx.cache.exact_paths = self.exact_paths;
+        top_level_module
+    }
+
+    fn visit_mod_contents(
+        &mut self,
+        id: hir::HirId,
+        m: &'tcx hir::Mod<'tcx>,
+        name: Symbol,
+    ) -> Module<'tcx> {
+        let mut om = Module::new(name, id, m.spans.inner_span);
+        let def_id = self.cx.tcx.hir().local_def_id(id).to_def_id();
+        // Keep track of if there were any private modules in the path.
+        let orig_inside_public_path = self.inside_public_path;
+        self.inside_public_path &= self.cx.tcx.visibility(def_id).is_public();
+        for &i in m.item_ids {
+            let item = self.cx.tcx.hir().item(i);
+            self.visit_item(item, None, &mut om);
+        }
+        self.inside_public_path = orig_inside_public_path;
+        om
+    }
+
+    /// Tries to resolve the target of a `pub use` statement and inlines the
+    /// target if it is defined locally and would not be documented otherwise,
+    /// or when it is specifically requested with `please_inline`.
+    /// (the latter is the case when the import is marked `doc(inline)`)
+    ///
+    /// Cross-crate inlining occurs later on during crate cleaning
+    /// and follows different rules.
+    ///
+    /// Returns `true` if the target has been inlined.
+    fn maybe_inline_local(
+        &mut self,
+        id: hir::HirId,
+        res: Res,
+        renamed: Option<Symbol>,
+        glob: bool,
+        om: &mut Module<'tcx>,
+        please_inline: bool,
+    ) -> bool {
+        debug!("maybe_inline_local res: {:?}", res);
+
+        if self.cx.output_format.is_json() {
+            return false;
+        }
+
+        let tcx = self.cx.tcx;
+        let Some(res_did) = res.opt_def_id() else {
+            return false;
+        };
+
+        let use_attrs = tcx.hir().attrs(id);
+        // Don't inline `doc(hidden)` imports so they can be stripped at a later stage.
+        let is_no_inline = use_attrs.lists(sym::doc).has_word(sym::no_inline)
+            || use_attrs.lists(sym::doc).has_word(sym::hidden);
+
+        // For cross-crate impl inlining we need to know whether items are
+        // reachable in documentation -- a previously unreachable item can be
+        // made reachable by cross-crate inlining which we're checking here.
+        // (this is done here because we need to know this upfront).
+        if !res_did.is_local() && !is_no_inline {
+            let attrs = clean::inline::load_attrs(self.cx, res_did);
+            let self_is_hidden = attrs.lists(sym::doc).has_word(sym::hidden);
+            if !self_is_hidden {
+                if let Res::Def(kind, did) = res {
+                    if kind == DefKind::Mod {
+                        crate::visit_lib::LibEmbargoVisitor::new(self.cx).visit_mod(did)
+                    } else {
+                        // All items need to be handled here in case someone wishes to link
+                        // to them with intra-doc links
+                        self.cx.cache.access_levels.map.insert(did, AccessLevel::Public);
+                    }
+                }
+            }
+            return false;
+        }
+
+        let res_hir_id = match res_did.as_local() {
+            Some(n) => tcx.hir().local_def_id_to_hir_id(n),
+            None => return false,
+        };
+
+        let is_private = !self.cx.cache.access_levels.is_public(res_did);
+        let is_hidden = inherits_doc_hidden(self.cx.tcx, res_hir_id);
+
+        // Only inline if requested or if the item would otherwise be stripped.
+        if (!please_inline && !is_private && !is_hidden) || is_no_inline {
+            return false;
+        }
+
+        if !self.view_item_stack.insert(res_hir_id) {
+            return false;
+        }
+
+        let ret = match tcx.hir().get(res_hir_id) {
+            Node::Item(&hir::Item { kind: hir::ItemKind::Mod(ref m), .. }) if glob => {
+                let prev = mem::replace(&mut self.inlining, true);
+                for &i in m.item_ids {
+                    let i = self.cx.tcx.hir().item(i);
+                    self.visit_item(i, None, om);
+                }
+                self.inlining = prev;
+                true
+            }
+            Node::Item(it) if !glob => {
+                let prev = mem::replace(&mut self.inlining, true);
+                self.visit_item(it, renamed, om);
+                self.inlining = prev;
+                true
+            }
+            Node::ForeignItem(it) if !glob => {
+                let prev = mem::replace(&mut self.inlining, true);
+                self.visit_foreign_item(it, renamed, om);
+                self.inlining = prev;
+                true
+            }
+            _ => false,
+        };
+        self.view_item_stack.remove(&res_hir_id);
+        ret
+    }
+
+    fn visit_item(
+        &mut self,
+        item: &'tcx hir::Item<'_>,
+        renamed: Option<Symbol>,
+        om: &mut Module<'tcx>,
+    ) {
+        debug!("visiting item {:?}", item);
+        let name = renamed.unwrap_or(item.ident.name);
+
+        let def_id = item.def_id.to_def_id();
+        let is_pub = self.cx.tcx.visibility(def_id).is_public();
+
+        if is_pub {
+            self.store_path(item.def_id.to_def_id());
+        }
+
+        match item.kind {
+            hir::ItemKind::ForeignMod { items, .. } => {
+                for item in items {
+                    let item = self.cx.tcx.hir().foreign_item(item.id);
+                    self.visit_foreign_item(item, None, om);
+                }
+            }
+            // If we're inlining, skip private items or item reexported as "_".
+            _ if self.inlining && (!is_pub || renamed == Some(kw::Underscore)) => {}
+            hir::ItemKind::GlobalAsm(..) => {}
+            hir::ItemKind::Use(_, hir::UseKind::ListStem) => {}
+            hir::ItemKind::Use(path, kind) => {
+                let is_glob = kind == hir::UseKind::Glob;
+
+                // Struct and variant constructors and proc macro stubs always show up alongside
+                // their definitions, we've already processed them so just discard these.
+                if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = path.res {
+                    return;
+                }
+
+                let attrs = self.cx.tcx.hir().attrs(item.hir_id());
+
+                // If there was a private module in the current path then don't bother inlining
+                // anything as it will probably be stripped anyway.
+                if is_pub && self.inside_public_path {
+                    let please_inline = attrs.iter().any(|item| match item.meta_item_list() {
+                        Some(ref list) if item.has_name(sym::doc) => {
+                            list.iter().any(|i| i.has_name(sym::inline))
+                        }
+                        _ => false,
+                    });
+                    let ident = if is_glob { None } else { Some(name) };
+                    if self.maybe_inline_local(
+                        item.hir_id(),
+                        path.res,
+                        ident,
+                        is_glob,
+                        om,
+                        please_inline,
+                    ) {
+                        return;
+                    }
+                }
+
+                om.items.push((item, renamed))
+            }
+            hir::ItemKind::Macro(ref macro_def, _) => {
+                // `#[macro_export] macro_rules!` items are handled separately in `visit()`,
+                // above, since they need to be documented at the module top level. Accordingly,
+                // we only want to handle macros if one of three conditions holds:
+                //
+                // 1. This macro was defined by `macro`, and thus isn't covered by the case
+                //    above.
+                // 2. This macro isn't marked with `#[macro_export]`, and thus isn't covered
+                //    by the case above.
+                // 3. We're inlining, since a reexport where inlining has been requested
+                //    should be inlined even if it is also documented at the top level.
+
+                let def_id = item.def_id.to_def_id();
+                let is_macro_2_0 = !macro_def.macro_rules;
+                let nonexported = !self.cx.tcx.has_attr(def_id, sym::macro_export);
+
+                if is_macro_2_0 || nonexported || self.inlining {
+                    om.items.push((item, renamed));
+                }
+            }
+            hir::ItemKind::Mod(ref m) => {
+                om.mods.push(self.visit_mod_contents(item.hir_id(), m, name));
+            }
+            hir::ItemKind::Fn(..)
+            | hir::ItemKind::ExternCrate(..)
+            | hir::ItemKind::Enum(..)
+            | hir::ItemKind::Struct(..)
+            | hir::ItemKind::Union(..)
+            | hir::ItemKind::TyAlias(..)
+            | hir::ItemKind::OpaqueTy(..)
+            | hir::ItemKind::Static(..)
+            | hir::ItemKind::Trait(..)
+            | hir::ItemKind::TraitAlias(..) => om.items.push((item, renamed)),
+            hir::ItemKind::Const(..) => {
+                // Underscore constants do not correspond to a nameable item and
+                // so are never useful in documentation.
+                if name != kw::Underscore {
+                    om.items.push((item, renamed));
+                }
+            }
+            hir::ItemKind::Impl(impl_) => {
+                // Don't duplicate impls when inlining or if it's implementing a trait, we'll pick
+                // them up regardless of where they're located.
+                if !self.inlining && impl_.of_trait.is_none() {
+                    om.items.push((item, None));
+                }
+            }
+        }
+    }
+
+    fn visit_foreign_item(
+        &mut self,
+        item: &'tcx hir::ForeignItem<'_>,
+        renamed: Option<Symbol>,
+        om: &mut Module<'tcx>,
+    ) {
+        // If inlining we only want to include public functions.
+        if !self.inlining || self.cx.tcx.visibility(item.def_id).is_public() {
+            om.foreigns.push((item, renamed));
+        }
+    }
+}
diff --git a/src/librustdoc/visit_lib.rs b/src/librustdoc/visit_lib.rs
new file mode 100644
index 000000000..f01ec3866
--- /dev/null
+++ b/src/librustdoc/visit_lib.rs
@@ -0,0 +1,82 @@
+use rustc_data_structures::fx::FxHashSet;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::{CrateNum, DefId};
+use rustc_middle::middle::privacy::{AccessLevel, AccessLevels};
+use rustc_middle::ty::TyCtxt;
+
+// FIXME: this may not be exhaustive, but is sufficient for rustdocs current uses
+
+/// Similar to `librustc_privacy::EmbargoVisitor`, but also takes
+/// specific rustdoc annotations into account (i.e., `doc(hidden)`)
+pub(crate) struct LibEmbargoVisitor<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    // Accessibility levels for reachable nodes
+    access_levels: &'a mut AccessLevels<DefId>,
+    // Previous accessibility level, None means unreachable
+    prev_level: Option<AccessLevel>,
+    // Keeps track of already visited modules, in case a module re-exports its parent
+    visited_mods: FxHashSet<DefId>,
+}
+
+impl<'a, 'tcx> LibEmbargoVisitor<'a, 'tcx> {
+    pub(crate) fn new(cx: &'a mut crate::core::DocContext<'tcx>) -> LibEmbargoVisitor<'a, 'tcx> {
+        LibEmbargoVisitor {
+            tcx: cx.tcx,
+            access_levels: &mut cx.cache.access_levels,
+            prev_level: Some(AccessLevel::Public),
+            visited_mods: FxHashSet::default(),
+        }
+    }
+
+    pub(crate) fn visit_lib(&mut self, cnum: CrateNum) {
+        let did = cnum.as_def_id();
+        self.update(did, Some(AccessLevel::Public));
+        self.visit_mod(did);
+    }
+
+    // Updates node level and returns the updated level
+    fn update(&mut self, did: DefId, level: Option<AccessLevel>) -> Option<AccessLevel> {
+        let is_hidden = self.tcx.is_doc_hidden(did);
+
+        let old_level = self.access_levels.map.get(&did).cloned();
+        // Accessibility levels can only grow
+        if level > old_level && !is_hidden {
+            self.access_levels.map.insert(did, level.unwrap());
+            level
+        } else {
+            old_level
+        }
+    }
+
+    pub(crate) fn visit_mod(&mut self, def_id: DefId) {
+        if !self.visited_mods.insert(def_id) {
+            return;
+        }
+
+        for item in self.tcx.module_children(def_id).iter() {
+            if let Some(def_id) = item.res.opt_def_id() {
+                if self.tcx.def_key(def_id).parent.map_or(false, |d| d == def_id.index)
+                    || item.vis.is_public()
+                {
+                    self.visit_item(item.res);
+                }
+            }
+        }
+    }
+
+    fn visit_item(&mut self, res: Res<!>) {
+        let def_id = res.def_id();
+        let vis = self.tcx.visibility(def_id);
+        let inherited_item_level = if vis.is_public() { self.prev_level } else { None };
+
+        let item_level = self.update(def_id, inherited_item_level);
+
+        if let Res::Def(DefKind::Mod, _) = res {
+            let orig_level = self.prev_level;
+
+            self.prev_level = item_level;
+            self.visit_mod(def_id);
+            self.prev_level = orig_level;
+        }
+    }
+}