Merging upstream version 1.67.1+dfsg1.

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

8 files changed, 568 insertions, 389 deletions

diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index 764a6d3aa..953f4aa8a 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -3,6 +3,7 @@ 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 thin_vec::ThinVec;
 
 use std::fmt::Debug;
 
@@ -43,7 +44,7 @@ where
         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, &[]) };
+        let trait_ref = tcx.mk_trait_ref(trait_def_id, [ty]);
         if !self.cx.generated_synthetics.insert((ty, trait_def_id)) {
             debug!("get_auto_trait_impl_for({:?}): already generated, aborting", trait_ref);
             return None;
@@ -110,7 +111,7 @@ where
                 );
                 let params = raw_generics.params;
 
-                Generics { params, where_predicates: Vec::new() }
+                Generics { params, where_predicates: ThinVec::new() }
             }
             AutoTraitResult::ExplicitImpl => return None,
         };
@@ -118,7 +119,6 @@ where
         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,
@@ -130,6 +130,7 @@ where
                 kind: ImplKind::Auto,
             }))),
             cfg: None,
+            inline_stmt_id: None,
         })
     }
 
@@ -183,7 +184,7 @@ where
     fn handle_lifetimes<'cx>(
         regions: &RegionConstraintData<'cx>,
         names_map: &FxHashMap<Symbol, Lifetime>,
-    ) -> Vec<WherePredicate> {
+    ) -> ThinVec<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
@@ -320,10 +321,10 @@ where
         let bound_predicate = pred.kind();
         let tcx = self.cx.tcx;
         let regions = match bound_predicate.skip_binder() {
-            ty::PredicateKind::Trait(poly_trait_pred) => {
+            ty::PredicateKind::Clause(ty::Clause::Trait(poly_trait_pred)) => {
                 tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred))
             }
-            ty::PredicateKind::Projection(poly_proj_pred) => {
+            ty::PredicateKind::Clause(ty::Clause::Projection(poly_proj_pred)) => {
                 tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_proj_pred))
             }
             _ => return FxHashSet::default(),
@@ -335,10 +336,7 @@ where
                 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![] },
-                    }),
+                    ty::BrNamed(_, name) => Some(GenericParamDef::lifetime(name)),
                     _ => None,
                 }
             })
@@ -429,7 +427,7 @@ where
         &mut self,
         item_def_id: DefId,
         param_env: ty::ParamEnv<'tcx>,
-        mut existing_predicates: Vec<WherePredicate>,
+        mut existing_predicates: ThinVec<WherePredicate>,
         vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'tcx>>,
     ) -> Generics {
         debug!(
@@ -453,7 +451,9 @@ where
             .filter(|p| {
                 !orig_bounds.contains(p)
                     || match p.kind().skip_binder() {
-                        ty::PredicateKind::Trait(pred) => pred.def_id() == sized_trait,
+                        ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => {
+                            pred.def_id() == sized_trait
+                        }
                         _ => false,
                     }
             })
@@ -663,7 +663,7 @@ where
     /// both for visual consistency between 'rustdoc' runs, and to
     /// make writing tests much easier
     #[inline]
-    fn sort_where_predicates(&self, predicates: &mut Vec<WherePredicate>) {
+    fn sort_where_predicates(&self, predicates: &mut [WherePredicate]) {
         // We should never have identical bounds - and if we do,
         // they're visually identical as well. Therefore, using
         // an unstable sort is fine.
@@ -710,7 +710,7 @@ where
     /// 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>) {
+    fn unstable_debug_sort<T: Debug>(&self, vec: &mut [T]) {
         vec.sort_by_cached_key(|x| format!("{:?}", x))
     }
 
diff --git a/src/librustdoc/clean/blanket_impl.rs b/src/librustdoc/clean/blanket_impl.rs
index 8b63c3db3..a1145b90d 100644
--- a/src/librustdoc/clean/blanket_impl.rs
+++ b/src/librustdoc/clean/blanket_impl.rs
@@ -20,7 +20,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
         trace!("get_blanket_impls({:?})", ty);
         let mut impls = Vec::new();
         for trait_def_id in cx.tcx.all_traits() {
-            if !cx.cache.effective_visibilities.is_directly_public(trait_def_id)
+            if !cx.cache.effective_visibilities.is_directly_public(cx.tcx, trait_def_id)
                 || cx.generated_synthetics.get(&(ty.0, trait_def_id)).is_some()
             {
                 continue;
@@ -67,15 +67,11 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     .instantiate(cx.tcx, impl_substs)
                     .predicates
                     .into_iter()
-                    .chain(Some(
-                        ty::Binder::dummy(impl_trait_ref)
-                            .to_poly_trait_predicate()
-                            .map_bound(ty::PredicateKind::Trait)
-                            .to_predicate(infcx.tcx),
-                    ));
+                    .chain(Some(ty::Binder::dummy(impl_trait_ref).to_predicate(infcx.tcx)));
                 for predicate in predicates {
                     debug!("testing predicate {:?}", predicate);
                     let obligation = traits::Obligation::new(
+                        infcx.tcx,
                         traits::ObligationCause::dummy(),
                         param_env,
                         predicate,
@@ -97,7 +93,6 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                 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,
@@ -128,6 +123,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                         ))),
                     }))),
                     cfg: None,
+                    inline_stmt_id: None,
                 });
             }
         }
diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
index f33f5d27d..1843a2120 100644
--- a/src/librustdoc/clean/cfg.rs
+++ b/src/librustdoc/clean/cfg.rs
@@ -50,7 +50,7 @@ impl Cfg {
     ) -> Result<Option<Cfg>, InvalidCfgError> {
         match nested_cfg {
             NestedMetaItem::MetaItem(ref cfg) => Cfg::parse_without(cfg, exclude),
-            NestedMetaItem::Literal(ref lit) => {
+            NestedMetaItem::Lit(ref lit) => {
                 Err(InvalidCfgError { msg: "unexpected literal", span: lit.span })
             }
         }
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 4e2031a91..e7c3e5a45 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -3,7 +3,7 @@
 use std::iter::once;
 use std::sync::Arc;
 
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashSet;
@@ -19,8 +19,7 @@ use rustc_span::symbol::{kw, sym, Symbol};
 use crate::clean::{
     self, clean_fn_decl_from_did_and_sig, clean_generics, clean_impl_item, clean_middle_assoc_item,
     clean_middle_field, clean_middle_ty, clean_trait_ref_with_bindings, clean_ty,
-    clean_ty_generics, clean_variant_def, clean_visibility, utils, Attributes, AttributesExt,
-    ImplKind, ItemId, Type, Visibility,
+    clean_ty_generics, clean_variant_def, utils, Attributes, AttributesExt, ImplKind, ItemId, Type,
 };
 use crate::core::DocContext;
 use crate::formats::item_type::ItemType;
@@ -152,18 +151,10 @@ pub(crate) fn try_inline(
 
     let (attrs, cfg) = merge_attrs(cx, Some(parent_module), load_attrs(cx, did), attrs);
     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));
-    }
+    let mut item =
+        clean::Item::from_def_id_and_attrs_and_parts(did, Some(name), kind, Box::new(attrs), cfg);
+    // The visibility needs to reflect the one from the reexport and not from the "source" DefId.
+    item.inline_stmt_id = import_def_id;
     ret.push(item);
     Some(ret)
 }
@@ -239,13 +230,7 @@ pub(crate) fn build_external_trait(cx: &mut DocContext<'_>, did: DefId) -> clean
         .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, ..clean_middle_assoc_item(item, cx) }
-        })
+        .map(|item| clean_middle_assoc_item(item, cx))
         .collect();
 
     let predicates = cx.tcx.predicates_of(did);
@@ -258,10 +243,19 @@ pub(crate) fn build_external_trait(cx: &mut DocContext<'_>, did: DefId) -> clean
 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 late_bound_regions = sig.bound_vars().into_iter().filter_map(|var| match var {
+        ty::BoundVariableKind::Region(ty::BrNamed(_, name)) if name != kw::UnderscoreLifetime => {
+            Some(clean::GenericParamDef::lifetime(name))
+        }
+        _ => None,
+    });
+
+    let predicates = cx.tcx.explicit_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 mut generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+        // FIXME: This does not place parameters in source order (late-bound ones come last)
+        generics.params.extend(late_bound_regions);
         let decl = clean_fn_decl_from_did_and_sig(cx, Some(did), sig);
         (generics, decl)
     });
@@ -282,7 +276,7 @@ fn build_struct(cx: &mut DocContext<'_>, did: DefId) -> clean::Struct {
     let variant = cx.tcx.adt_def(did).non_enum_variant();
 
     clean::Struct {
-        struct_type: variant.ctor_kind,
+        ctor_kind: 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(),
     }
@@ -389,7 +383,7 @@ pub(crate) fn build_impl(
     if !did.is_local() {
         if let Some(traitref) = associated_trait {
             let did = traitref.def_id;
-            if !cx.cache.effective_visibilities.is_directly_public(did) {
+            if !cx.cache.effective_visibilities.is_directly_public(tcx, did) {
                 return;
             }
 
@@ -418,7 +412,7 @@ pub(crate) fn build_impl(
     // reachable in rustdoc generated documentation
     if !did.is_local() {
         if let Some(did) = for_.def_id(&cx.cache) {
-            if !cx.cache.effective_visibilities.is_directly_public(did) {
+            if !cx.cache.effective_visibilities.is_directly_public(tcx, did) {
                 return;
             }
 
@@ -559,7 +553,6 @@ pub(crate) fn build_impl(
             },
         })),
         Box::new(merged_attrs),
-        cx,
         cfg,
     ));
 }
@@ -607,13 +600,12 @@ fn build_module_items(
                     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 {
+                                segments: thin_vec![clean::PathSegment {
                                     name: prim_ty.as_sym(),
                                     args: clean::GenericArgs::AngleBracketed {
                                         args: Default::default(),
@@ -626,6 +618,7 @@ fn build_module_items(
                         true,
                     ))),
                     cfg: None,
+                    inline_stmt_id: None,
                 });
             } else if let Some(i) = try_inline(cx, did, None, res, item.ident.name, None, visited) {
                 items.extend(i)
@@ -669,7 +662,7 @@ fn build_macro(
     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)));
+                let vis = 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),
                 })
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 64a18757b..2a2a9470d 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -12,7 +12,7 @@ pub(crate) mod utils;
 
 use rustc_ast as ast;
 use rustc_attr as attr;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet, IndexEntry};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
@@ -74,12 +74,12 @@ pub(crate) fn clean_doc_module<'tcx>(doc: &DocModule<'tcx>, cx: &mut DocContext<
     // 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(doc.items.iter().flat_map(|(item, renamed)| {
+    items.extend(doc.items.iter().flat_map(|(item, renamed, import_id)| {
         // 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);
+        let v = clean_maybe_renamed_item(cx, item, *renamed, *import_id);
         for item in &v {
             if let Some(name) = item.name && !item.attrs.lists(sym::doc).has_word(sym::hidden) {
                 inserted.insert((item.type_(), name));
@@ -87,7 +87,7 @@ pub(crate) fn clean_doc_module<'tcx>(doc: &DocModule<'tcx>, cx: &mut DocContext<
         }
         v
     }));
-    items.extend(doc.items.iter().flat_map(|(item, renamed)| {
+    items.extend(doc.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()));
@@ -182,10 +182,7 @@ fn clean_poly_trait_ref_with_bindings<'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![] },
-            }),
+            ty::BrNamed(_, name) if br.is_named() => Some(GenericParamDef::lifetime(name)),
             _ => None,
         })
         .collect();
@@ -209,7 +206,7 @@ fn clean_lifetime<'tcx>(lifetime: &hir::Lifetime, cx: &mut DocContext<'tcx>) ->
             return lt;
         }
     }
-    Lifetime(lifetime.name.ident().name)
+    Lifetime(lifetime.ident.name)
 }
 
 pub(crate) fn clean_const<'tcx>(constant: &hir::ConstArg, cx: &mut DocContext<'tcx>) -> Constant {
@@ -227,23 +224,18 @@ pub(crate) fn clean_middle_const<'tcx>(
     // 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() },
+        kind: ConstantKind::TyConst { expr: constant.to_string().into() },
     }
 }
 
 pub(crate) fn clean_middle_region<'tcx>(region: ty::Region<'tcx>) -> Option<Lifetime> {
     match *region {
         ty::ReStatic => Some(Lifetime::statik()),
+        _ if !region.has_name() => None,
         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
-            }
+            Some(Lifetime(name))
         }
+        ty::ReEarlyBound(ref data) => Some(Lifetime(data.name)),
         ty::ReLateBound(..)
         | ty::ReFree(..)
         | ty::ReVar(..)
@@ -303,12 +295,16 @@ pub(crate) fn clean_predicate<'tcx>(
 ) -> Option<WherePredicate> {
     let bound_predicate = predicate.kind();
     match bound_predicate.skip_binder() {
-        ty::PredicateKind::Trait(pred) => {
+        ty::PredicateKind::Clause(ty::Clause::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) => {
+        ty::PredicateKind::Clause(ty::Clause::RegionOutlives(pred)) => {
+            clean_region_outlives_predicate(pred)
+        }
+        ty::PredicateKind::Clause(ty::Clause::TypeOutlives(pred)) => {
+            clean_type_outlives_predicate(pred, cx)
+        }
+        ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
             Some(clean_projection_predicate(bound_predicate.rebind(pred), cx))
         }
         ty::PredicateKind::ConstEvaluatable(..) => None,
@@ -319,6 +315,7 @@ pub(crate) fn clean_predicate<'tcx>(
         | ty::PredicateKind::ObjectSafe(..)
         | ty::PredicateKind::ClosureKind(..)
         | ty::PredicateKind::ConstEquate(..)
+        | ty::PredicateKind::Ambiguous
         | ty::PredicateKind::TypeWellFormedFromEnv(..) => panic!("not user writable"),
     }
 }
@@ -396,7 +393,7 @@ fn clean_projection_predicate<'tcx>(
         .collect_referenced_late_bound_regions(&pred)
         .into_iter()
         .filter_map(|br| match br {
-            ty::BrNamed(_, name) if name != kw::UnderscoreLifetime => Some(Lifetime(name)),
+            ty::BrNamed(_, name) if br.is_named() => Some(Lifetime(name)),
             _ => None,
         })
         .collect();
@@ -601,47 +598,105 @@ pub(crate) fn clean_generics<'tcx>(
         })
         .collect::<Vec<_>>();
 
-    let mut params = Vec::with_capacity(gens.params.len());
-    for p in gens.params.iter().filter(|p| !is_impl_trait(p) && !is_elided_lifetime(p)) {
-        let p = clean_generic_param(cx, Some(gens), p);
-        params.push(p);
+    let mut bound_predicates = FxIndexMap::default();
+    let mut region_predicates = FxIndexMap::default();
+    let mut eq_predicates = ThinVec::default();
+    for pred in gens.predicates.iter().filter_map(|x| clean_where_predicate(x, cx)) {
+        match pred {
+            WherePredicate::BoundPredicate { ty, bounds, bound_params } => {
+                match bound_predicates.entry(ty) {
+                    IndexEntry::Vacant(v) => {
+                        v.insert((bounds, bound_params));
+                    }
+                    IndexEntry::Occupied(mut o) => {
+                        // we merge both bounds.
+                        for bound in bounds {
+                            if !o.get().0.contains(&bound) {
+                                o.get_mut().0.push(bound);
+                            }
+                        }
+                        for bound_param in bound_params {
+                            if !o.get().1.contains(&bound_param) {
+                                o.get_mut().1.push(bound_param);
+                            }
+                        }
+                    }
+                }
+            }
+            WherePredicate::RegionPredicate { lifetime, bounds } => {
+                match region_predicates.entry(lifetime) {
+                    IndexEntry::Vacant(v) => {
+                        v.insert(bounds);
+                    }
+                    IndexEntry::Occupied(mut o) => {
+                        // we merge both bounds.
+                        for bound in bounds {
+                            if !o.get().contains(&bound) {
+                                o.get_mut().push(bound);
+                            }
+                        }
+                    }
+                }
+            }
+            WherePredicate::EqPredicate { lhs, rhs, bound_params } => {
+                eq_predicates.push(WherePredicate::EqPredicate { lhs, rhs, bound_params });
+            }
+        }
     }
-    params.extend(impl_trait_params);
 
-    let mut generics = Generics {
-        params,
-        where_predicates: gens
-            .predicates
-            .iter()
-            .filter_map(|x| clean_where_predicate(x, 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 { .. } => {}
+    let mut params = ThinVec::with_capacity(gens.params.len());
+    // In this loop, we gather the generic parameters (`<'a, B: 'a>`) and check if they have
+    // bounds in the where predicates. If so, we move their bounds into the where predicates
+    // while also preventing duplicates.
+    for p in gens.params.iter().filter(|p| !is_impl_trait(p) && !is_elided_lifetime(p)) {
+        let mut p = clean_generic_param(cx, Some(gens), p);
+        match &mut p.kind {
+            GenericParamDefKind::Lifetime { ref mut outlives } => {
+                if let Some(region_pred) = region_predicates.get_mut(&Lifetime(p.name)) {
+                    // We merge bounds in the `where` clause.
+                    for outlive in outlives.drain(..) {
+                        let outlive = GenericBound::Outlives(outlive);
+                        if !region_pred.contains(&outlive) {
+                            region_pred.push(outlive);
+                        }
+                    }
+                }
+            }
+            GenericParamDefKind::Type { bounds, synthetic: false, .. } => {
+                if let Some(bound_pred) = bound_predicates.get_mut(&Type::Generic(p.name)) {
+                    // We merge bounds in the `where` clause.
+                    for bound in bounds.drain(..) {
+                        if !bound_pred.0.contains(&bound) {
+                            bound_pred.0.push(bound);
                         }
                     }
                 }
             }
-            _ => continue,
+            GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
+                // nothing to do here.
+            }
         }
+        params.push(p);
+    }
+    params.extend(impl_trait_params);
+
+    Generics {
+        params,
+        where_predicates: bound_predicates
+            .into_iter()
+            .map(|(ty, (bounds, bound_params))| WherePredicate::BoundPredicate {
+                ty,
+                bounds,
+                bound_params,
+            })
+            .chain(
+                region_predicates
+                    .into_iter()
+                    .map(|(lifetime, bounds)| WherePredicate::RegionPredicate { lifetime, bounds }),
+            )
+            .chain(eq_predicates.into_iter())
+            .collect(),
     }
-    generics
 }
 
 fn clean_ty_generics<'tcx>(
@@ -660,7 +715,7 @@ fn clean_ty_generics<'tcx>(
         .params
         .iter()
         .filter_map(|param| match param.kind {
-            ty::GenericParamDefKind::Lifetime if param.name == kw::UnderscoreLifetime => None,
+            ty::GenericParamDefKind::Lifetime if param.is_anonymous_lifetime() => None,
             ty::GenericParamDefKind::Lifetime => Some(clean_generic_param_def(param, cx)),
             ty::GenericParamDefKind::Type { synthetic, .. } => {
                 if param.name == kw::SelfUpper {
@@ -675,7 +730,7 @@ fn clean_ty_generics<'tcx>(
             }
             ty::GenericParamDefKind::Const { .. } => Some(clean_generic_param_def(param, cx)),
         })
-        .collect::<Vec<GenericParamDef>>();
+        .collect::<ThinVec<GenericParamDef>>();
 
     // param index -> [(trait DefId, associated type name & generics, type, higher-ranked params)]
     let mut impl_trait_proj =
@@ -689,17 +744,20 @@ fn clean_ty_generics<'tcx>(
             let param_idx = (|| {
                 let bound_p = p.kind();
                 match bound_p.skip_binder() {
-                    ty::PredicateKind::Trait(pred) => {
+                    ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => {
                         if let ty::Param(param) = pred.self_ty().kind() {
                             return Some(param.index);
                         }
                     }
-                    ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, _reg)) => {
+                    ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
+                        ty,
+                        _reg,
+                    ))) => {
                         if let ty::Param(param) = ty.kind() {
                             return Some(param.index);
                         }
                     }
-                    ty::PredicateKind::Projection(p) => {
+                    ty::PredicateKind::Clause(ty::Clause::Projection(p)) => {
                         if let ty::Param(param) = p.projection_ty.self_ty().kind() {
                             projection = Some(bound_p.rebind(p));
                             return Some(param.index);
@@ -741,10 +799,7 @@ fn clean_ty_generics<'tcx>(
                             p.get_bound_params()
                                 .into_iter()
                                 .flatten()
-                                .map(|param| GenericParamDef {
-                                    name: param.0,
-                                    kind: GenericParamDefKind::Lifetime { outlives: Vec::new() },
-                                })
+                                .map(|param| GenericParamDef::lifetime(param.0))
                                 .collect(),
                         ));
                     }
@@ -880,7 +935,7 @@ fn clean_fn_or_proc_macro<'tcx>(
             ProcMacroItem(ProcMacro { kind, helpers })
         }
         None => {
-            let mut func = clean_function(cx, sig, generics, body_id);
+            let mut func = clean_function(cx, sig, generics, FunctionArgs::Body(body_id));
             clean_fn_decl_legacy_const_generics(&mut func, attrs);
             FunctionItem(func)
         }
@@ -896,7 +951,7 @@ fn clean_fn_decl_legacy_const_generics(func: &mut Function, attrs: &[ast::Attrib
         .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() {
+        for (pos, literal) in meta_item_list.iter().filter_map(|meta| meta.lit()).enumerate() {
             match literal.kind {
                 ast::LitKind::Int(a, _) => {
                     let gen = func.generics.params.remove(0);
@@ -917,16 +972,28 @@ fn clean_fn_decl_legacy_const_generics(func: &mut Function, attrs: &[ast::Attrib
     }
 }
 
+enum FunctionArgs<'tcx> {
+    Body(hir::BodyId),
+    Names(&'tcx [Ident]),
+}
+
 fn clean_function<'tcx>(
     cx: &mut DocContext<'tcx>,
     sig: &hir::FnSig<'tcx>,
     generics: &hir::Generics<'tcx>,
-    body_id: hir::BodyId,
+    args: FunctionArgs<'tcx>,
 ) -> Box<Function> {
     let (generics, decl) = enter_impl_trait(cx, |cx| {
         // NOTE: generics must be cleaned before args
         let generics = clean_generics(generics, cx);
-        let args = clean_args_from_types_and_body_id(cx, sig.decl.inputs, body_id);
+        let args = match args {
+            FunctionArgs::Body(body_id) => {
+                clean_args_from_types_and_body_id(cx, sig.decl.inputs, body_id)
+            }
+            FunctionArgs::Names(names) => {
+                clean_args_from_types_and_names(cx, sig.decl.inputs, names)
+            }
+        };
         let mut decl = clean_fn_decl_with_args(cx, sig.decl, args);
         if sig.header.is_async() {
             decl.output = decl.sugared_async_return_type();
@@ -945,12 +1012,14 @@ fn clean_args_from_types_and_names<'tcx>(
         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 }
+            .map(|(i, ty)| Argument {
+                type_: clean_ty(ty, cx),
+                name: names
+                    .get(i)
+                    .map(|ident| ident.name)
+                    .filter(|ident| !ident.is_empty())
+                    .unwrap_or(kw::Underscore),
+                is_const: false,
             })
             .collect(),
     }
@@ -1012,7 +1081,11 @@ fn clean_fn_decl_from_did_and_sig<'tcx>(
                 .iter()
                 .map(|t| Argument {
                     type_: clean_middle_ty(*t, cx, None),
-                    name: names.next().map_or(kw::Empty, |i| i.name),
+                    name: names
+                        .next()
+                        .map(|i| i.name)
+                        .filter(|i| !i.is_empty())
+                        .unwrap_or(kw::Underscore),
                     is_const: false,
                 })
                 .collect(),
@@ -1051,18 +1124,12 @@ fn clean_trait_item<'tcx>(trait_item: &hir::TraitItem<'tcx>, cx: &mut DocContext
             ),
             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, trait_item.generics, body);
+                let m = clean_function(cx, sig, trait_item.generics, FunctionArgs::Body(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 = clean_generics(trait_item.generics, 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 }))
+                let m = clean_function(cx, sig, trait_item.generics, FunctionArgs::Names(names));
+                TyMethodItem(m)
             }
             hir::TraitItemKind::Type(bounds, Some(default)) => {
                 let generics = enter_impl_trait(cx, |cx| clean_generics(trait_item.generics, cx));
@@ -1080,13 +1147,10 @@ fn clean_trait_item<'tcx>(trait_item: &hir::TraitItem<'tcx>, cx: &mut DocContext
             hir::TraitItemKind::Type(bounds, None) => {
                 let generics = enter_impl_trait(cx, |cx| clean_generics(trait_item.generics, cx));
                 let bounds = bounds.iter().filter_map(|x| clean_generic_bound(x, cx)).collect();
-                TyAssocTypeItem(Box::new(generics), bounds)
+                TyAssocTypeItem(generics, bounds)
             }
         };
-        let what_rustc_thinks =
-            Item::from_def_id_and_parts(local_did, Some(trait_item.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 }
+        Item::from_def_id_and_parts(local_did, Some(trait_item.ident.name), inner, cx)
     })
 }
 
@@ -1102,7 +1166,7 @@ pub(crate) fn clean_impl_item<'tcx>(
                 AssocConstItem(clean_ty(ty, cx), default)
             }
             hir::ImplItemKind::Fn(ref sig, body) => {
-                let m = clean_function(cx, sig, impl_.generics, body);
+                let m = clean_function(cx, sig, impl_.generics, FunctionArgs::Body(body));
                 let defaultness = cx.tcx.impl_defaultness(impl_.owner_id);
                 MethodItem(m, Some(defaultness))
             }
@@ -1117,18 +1181,7 @@ pub(crate) fn clean_impl_item<'tcx>(
             }
         };
 
-        let mut what_rustc_thinks =
-            Item::from_def_id_and_parts(local_did, Some(impl_.ident.name), inner, cx);
-
-        let impl_ref = cx.tcx.impl_trait_ref(cx.tcx.local_parent(impl_.owner_id.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
+        Item::from_def_id_and_parts(local_did, Some(impl_.ident.name), inner, cx)
     })
 }
 
@@ -1152,12 +1205,25 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
             }
         }
         ty::AssocKind::Fn => {
-            let generics = clean_ty_generics(
+            let sig = tcx.fn_sig(assoc_item.def_id);
+
+            let late_bound_regions = sig.bound_vars().into_iter().filter_map(|var| match var {
+                ty::BoundVariableKind::Region(ty::BrNamed(_, name))
+                    if name != kw::UnderscoreLifetime =>
+                {
+                    Some(GenericParamDef::lifetime(name))
+                }
+                _ => None,
+            });
+
+            let mut generics = clean_ty_generics(
                 cx,
                 tcx.generics_of(assoc_item.def_id),
                 tcx.explicit_predicates_of(assoc_item.def_id),
             );
-            let sig = tcx.fn_sig(assoc_item.def_id);
+            // FIXME: This does not place parameters in source order (late-bound ones come last)
+            generics.params.extend(late_bound_regions);
+
             let mut decl = clean_fn_decl_from_did_and_sig(cx, Some(assoc_item.def_id), sig);
 
             if assoc_item.fn_has_self_parameter {
@@ -1208,7 +1274,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                         true
                     }
                     (GenericParamDefKind::Const { .. }, GenericArg::Const(c)) => match &c.kind {
-                        ConstantKind::TyConst { expr } => expr == param.name.as_str(),
+                        ConstantKind::TyConst { expr } => **expr == *param.name.as_str(),
                         _ => false,
                     },
                     _ => false,
@@ -1225,56 +1291,47 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                     tcx.generics_of(assoc_item.def_id),
                     ty::GenericPredicates { parent: None, predicates },
                 );
-                // Move bounds that are (likely) directly attached to the associated type
-                // from the where clause to the associated type.
-                // There is no guarantee that this is what the user actually wrote but we have
-                // no way of knowing.
-                let mut bounds = generics
-                    .where_predicates
-                    .drain_filter(|pred| match *pred {
-                        WherePredicate::BoundPredicate {
-                            ty: QPath(box QPathData { ref assoc, ref self_type, ref trait_, .. }),
-                            ..
-                        } => {
-                            if assoc.name != my_name {
-                                return false;
-                            }
-                            if trait_.def_id() != assoc_item.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.
+                // 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: Vec<GenericBound> = Vec::new();
+                generics.where_predicates.retain_mut(|pred| match *pred {
+                    WherePredicate::BoundPredicate {
+                        ty: QPath(box QPathData { ref assoc, ref self_type, ref trait_, .. }),
+                        bounds: ref mut pred_bounds,
+                        ..
+                    } => {
+                        if assoc.name != my_name {
+                            return true;
+                        }
+                        if trait_.def_id() != assoc_item.container_id(tcx) {
+                            return true;
+                        }
+                        match *self_type {
+                            Generic(ref s) if *s == kw::SelfUpper => {}
+                            _ => return true,
+                        }
+                        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 true;
                                 }
                             }
-                            true
-                        }
-                        _ => false,
-                    })
-                    .flat_map(|pred| {
-                        if let WherePredicate::BoundPredicate { bounds, .. } = pred {
-                            bounds
-                        } else {
-                            unreachable!()
+                            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.
+                            }
                         }
-                    })
-                    .collect::<Vec<_>>();
+                        bounds.extend(mem::replace(pred_bounds, Vec::new()));
+                        false
+                    }
+                    _ => true,
+                });
                 // 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
@@ -1290,7 +1347,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                 // (generic) associated type from the where clause to the respective parameter.
                 // There is no guarantee that this is what the user actually wrote but we have
                 // no way of knowing.
-                let mut where_predicates = Vec::new();
+                let mut where_predicates = ThinVec::new();
                 for mut pred in generics.where_predicates {
                     if let WherePredicate::BoundPredicate { ty: Generic(arg), bounds, .. } = &mut pred
                     && let Some(GenericParamDef {
@@ -1298,7 +1355,16 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                         ..
                     }) = generics.params.iter_mut().find(|param| &param.name == arg)
                     {
-                        param_bounds.extend(mem::take(bounds));
+                        param_bounds.append(bounds);
+                    } else if let WherePredicate::RegionPredicate { lifetime: Lifetime(arg), bounds } = &mut pred
+                    && let Some(GenericParamDef {
+                        kind: GenericParamDefKind::Lifetime { outlives: param_bounds },
+                        ..
+                    }) = generics.params.iter_mut().find(|param| &param.name == arg) {
+                        param_bounds.extend(bounds.drain(..).map(|bound| match bound {
+                            GenericBound::Outlives(lifetime) => lifetime,
+                            _ => unreachable!(),
+                        }));
                     } else {
                         where_predicates.push(pred);
                     }
@@ -1320,7 +1386,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                         bounds,
                     )
                 } else {
-                    TyAssocTypeItem(Box::new(generics), bounds)
+                    TyAssocTypeItem(generics, bounds)
                 }
             } else {
                 // FIXME: when could this happen? Associated items in inherent impls?
@@ -1331,7 +1397,10 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                             cx,
                             Some(assoc_item.def_id),
                         ),
-                        generics: Generics { params: Vec::new(), where_predicates: Vec::new() },
+                        generics: Generics {
+                            params: ThinVec::new(),
+                            where_predicates: ThinVec::new(),
+                        },
                         item_type: None,
                     }),
                     Vec::new(),
@@ -1340,18 +1409,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
         }
     };
 
-    let mut what_rustc_thinks =
-        Item::from_def_id_and_parts(assoc_item.def_id, Some(assoc_item.name), kind, cx);
-
-    let impl_ref = tcx.impl_trait_ref(tcx.parent(assoc_item.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
+    Item::from_def_id_and_parts(assoc_item.def_id, Some(assoc_item.name), kind, cx)
 }
 
 fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
@@ -1406,7 +1464,8 @@ fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type
                 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),
+                // Otherwise, this is an inherent associated type.
+                _ => return clean_middle_ty(ty, cx, None),
             };
             let trait_ = clean_path(&hir::Path { span, res, segments: &[] }, cx);
             register_res(cx, trait_.res);
@@ -1431,7 +1490,7 @@ fn maybe_expand_private_type_alias<'tcx>(
     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.effective_visibilities.is_exported(def_id.to_def_id()) {
+    let alias = if !cx.cache.effective_visibilities.is_exported(cx.tcx, def_id.to_def_id()) {
         &cx.tcx.hir().expect_item(def_id).kind
     } else {
         return None;
@@ -1459,8 +1518,11 @@ fn maybe_expand_private_type_alias<'tcx>(
                 });
                 if let Some(lt) = lifetime {
                     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() };
+                    let cleaned = if !lt.is_anonymous() {
+                        clean_lifetime(lt, cx)
+                    } else {
+                        Lifetime::elided()
+                    };
                     substs.insert(lt_def_id.to_def_id(), SubstParam::Lifetime(cleaned));
                 }
                 indices.lifetimes += 1;
@@ -1523,16 +1585,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
         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)) };
+            let lifetime = if l.is_anonymous() { 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))),
@@ -1554,7 +1607,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
                 }
             };
 
-            Array(Box::new(clean_ty(ty, cx)), length)
+            Array(Box::new(clean_ty(ty, cx)), length.into())
         }
         TyKind::Tup(tys) => Tuple(tys.iter().map(|ty| clean_ty(ty, cx)).collect()),
         TyKind::OpaqueDef(item_id, _, _) => {
@@ -1586,14 +1639,14 @@ fn normalize<'tcx>(cx: &mut DocContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>>
     }
 
     use crate::rustc_trait_selection::infer::TyCtxtInferExt;
-    use crate::rustc_trait_selection::traits::query::normalize::AtExt;
+    use crate::rustc_trait_selection::traits::query::normalize::QueryNormalizeExt;
     use rustc_middle::traits::ObligationCause;
 
     // Try to normalize `<X as Y>::T` to a type
     let infcx = cx.tcx.infer_ctxt().build();
     let normalized = infcx
         .at(&ObligationCause::dummy(), cx.param_env)
-        .normalize(ty)
+        .query_normalize(ty)
         .map(|resolved| infcx.resolve_vars_if_possible(resolved.value));
     match normalized {
         Ok(normalized_value) => {
@@ -1626,7 +1679,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
         ty::Array(ty, mut n) => {
             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)
+            Array(Box::new(clean_middle_ty(ty, cx, None)), n.into())
         }
         ty::RawPtr(mt) => RawPointer(mt.mutbl, Box::new(clean_middle_ty(mt.ty, cx, None))),
         ty::Ref(r, ty, mutbl) => BorrowedRef {
@@ -1677,6 +1730,9 @@ pub(crate) fn clean_middle_ty<'tcx>(
 
             inline::record_extern_fqn(cx, did, ItemType::Trait);
 
+            // FIXME(fmease): Hide the trait-object lifetime bound if it coincides with its default
+            // to partially address #44306. Follow the rules outlined at
+            // https://doc.rust-lang.org/reference/lifetime-elision.html#default-trait-object-lifetimes
             let lifetime = clean_middle_region(*reg);
             let mut bounds = dids
                 .map(|did| {
@@ -1704,8 +1760,22 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 })
                 .collect();
 
+            let late_bound_regions: FxIndexSet<_> = obj
+                .iter()
+                .flat_map(|pb| pb.bound_vars())
+                .filter_map(|br| match br {
+                    ty::BoundVariableKind::Region(ty::BrNamed(_, name))
+                        if name != kw::UnderscoreLifetime =>
+                    {
+                        Some(GenericParamDef::lifetime(name))
+                    }
+                    _ => None,
+                })
+                .collect();
+            let late_bound_regions = late_bound_regions.into_iter().collect();
+
             let path = external_path(cx, did, false, bindings, substs);
-            bounds.insert(0, PolyTrait { trait_: path, generic_params: Vec::new() });
+            bounds.insert(0, PolyTrait { trait_: path, generic_params: late_bound_regions });
 
             DynTrait(bounds, lifetime)
         }
@@ -1754,8 +1824,13 @@ fn clean_middle_opaque_bounds<'tcx>(
         .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)) => {
+                ty::PredicateKind::Clause(ty::Clause::Trait(tr)) => {
+                    bound_predicate.rebind(tr.trait_ref)
+                }
+                ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
+                    _ty,
+                    reg,
+                ))) => {
                     if let Some(r) = clean_middle_region(reg) {
                         regions.push(GenericBound::Outlives(r));
                     }
@@ -1774,7 +1849,9 @@ fn clean_middle_opaque_bounds<'tcx>(
             let bindings: ThinVec<_> = bounds
                 .iter()
                 .filter_map(|bound| {
-                    if let ty::PredicateKind::Projection(proj) = bound.kind().skip_binder() {
+                    if let ty::PredicateKind::Clause(ty::Clause::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),
@@ -1821,50 +1898,24 @@ pub(crate) fn clean_field_with_def_id(
     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<DefId>) -> Visibility {
-    match vis {
-        ty::Visibility::Public => Visibility::Public,
-        ty::Visibility::Restricted(module) => Visibility::Restricted(module),
-    }
+    Item::from_def_id_and_parts(def_id, Some(name), StructFieldItem(ty), cx)
 }
 
 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(match variant.discr {
+    let kind = match variant.ctor_kind() {
+        Some(CtorKind::Const) => Variant::CLike(match variant.discr {
             ty::VariantDiscr::Explicit(def_id) => Some(Discriminant { expr: None, value: def_id }),
             ty::VariantDiscr::Relative(_) => None,
         }),
-        CtorKind::Fn => Variant::Tuple(
+        Some(CtorKind::Fn) => Variant::Tuple(
             variant.fields.iter().map(|field| clean_middle_field(field, cx)).collect(),
         ),
-        CtorKind::Fictive => Variant::Struct(VariantStruct {
-            struct_type: CtorKind::Fictive,
+        None => Variant::Struct(VariantStruct {
+            ctor_kind: None,
             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 }
+    Item::from_def_id_and_parts(variant.def_id, Some(variant.name), VariantItem(kind), cx)
 }
 
 fn clean_variant_data<'tcx>(
@@ -1874,7 +1925,7 @@ fn clean_variant_data<'tcx>(
 ) -> Variant {
     match variant {
         hir::VariantData::Struct(..) => Variant::Struct(VariantStruct {
-            struct_type: CtorKind::from_hir(variant),
+            ctor_kind: None,
             fields: variant.fields().iter().map(|x| clean_field(x, cx)).collect(),
         }),
         hir::VariantData::Tuple(..) => {
@@ -1909,7 +1960,7 @@ fn clean_generic_args<'tcx>(
             .args
             .iter()
             .map(|arg| match arg {
-                hir::GenericArg::Lifetime(lt) if !lt.is_elided() => {
+                hir::GenericArg::Lifetime(lt) if !lt.is_anonymous() => {
                     GenericArg::Lifetime(clean_lifetime(*lt, cx))
                 }
                 hir::GenericArg::Lifetime(_) => GenericArg::Lifetime(Lifetime::elided()),
@@ -1951,10 +2002,84 @@ fn clean_bare_fn_ty<'tcx>(
     BareFunctionDecl { unsafety: bare_fn.unsafety, abi: bare_fn.abi, decl, generic_params }
 }
 
+/// This visitor is used to go through only the "top level" of a item and not enter any sub
+/// item while looking for a given `Ident` which is stored into `item` if found.
+struct OneLevelVisitor<'hir> {
+    map: rustc_middle::hir::map::Map<'hir>,
+    item: Option<&'hir hir::Item<'hir>>,
+    looking_for: Ident,
+    target_hir_id: hir::HirId,
+}
+
+impl<'hir> OneLevelVisitor<'hir> {
+    fn new(map: rustc_middle::hir::map::Map<'hir>, target_hir_id: hir::HirId) -> Self {
+        Self { map, item: None, looking_for: Ident::empty(), target_hir_id }
+    }
+
+    fn reset(&mut self, looking_for: Ident) {
+        self.looking_for = looking_for;
+        self.item = None;
+    }
+}
+
+impl<'hir> hir::intravisit::Visitor<'hir> for OneLevelVisitor<'hir> {
+    type NestedFilter = rustc_middle::hir::nested_filter::All;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.map
+    }
+
+    fn visit_item(&mut self, item: &'hir hir::Item<'hir>) {
+        if self.item.is_none()
+            && item.ident == self.looking_for
+            && matches!(item.kind, hir::ItemKind::Use(_, _))
+            || item.hir_id() == self.target_hir_id
+        {
+            self.item = Some(item);
+        }
+    }
+}
+
+/// Because a `Use` item directly links to the imported item, we need to manually go through each
+/// import one by one. To do so, we go to the parent item and look for the `Ident` into it. Then,
+/// if we found the "end item" (the imported one), we stop there because we don't need its
+/// documentation. Otherwise, we repeat the same operation until we find the "end item".
+fn get_all_import_attributes<'hir>(
+    mut item: &hir::Item<'hir>,
+    tcx: TyCtxt<'hir>,
+    target_hir_id: hir::HirId,
+    attributes: &mut Vec<ast::Attribute>,
+) {
+    let hir_map = tcx.hir();
+    let mut visitor = OneLevelVisitor::new(hir_map, target_hir_id);
+    // If the item is an import and has at least a path with two parts, we go into it.
+    while let hir::ItemKind::Use(path, _) = item.kind &&
+        path.segments.len() > 1 &&
+        let hir::def::Res::Def(_, def_id) = path.segments[path.segments.len() - 2].res
+    {
+        if let Some(hir::Node::Item(parent_item)) = hir_map.get_if_local(def_id) {
+            // We add the attributes from this import into the list.
+            attributes.extend_from_slice(hir_map.attrs(item.hir_id()));
+            // We get the `Ident` we will be looking for into `item`.
+            let looking_for = path.segments[path.segments.len() - 1].ident;
+            visitor.reset(looking_for);
+            hir::intravisit::walk_item(&mut visitor, parent_item);
+            if let Some(i) = visitor.item {
+                item = i;
+            } else {
+                break;
+            }
+        } else {
+            break;
+        }
+    }
+}
+
 fn clean_maybe_renamed_item<'tcx>(
     cx: &mut DocContext<'tcx>,
     item: &hir::Item<'tcx>,
     renamed: Option<Symbol>,
+    import_id: Option<hir::HirId>,
 ) -> Vec<Item> {
     use hir::ItemKind;
 
@@ -1995,7 +2120,7 @@ fn clean_maybe_renamed_item<'tcx>(
                 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),
+                ctor_kind: variant_data.ctor_kind(),
                 generics: clean_generics(generics, cx),
                 fields: variant_data.fields().iter().map(|x| clean_field(x, cx)).collect(),
             }),
@@ -2005,7 +2130,7 @@ fn clean_maybe_renamed_item<'tcx>(
                 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));
+                let ty_vis = cx.tcx.visibility(def_id);
                 MacroItem(Macro {
                     source: display_macro_source(cx, name, macro_def, def_id, ty_vis),
                 })
@@ -2032,16 +2157,35 @@ fn clean_maybe_renamed_item<'tcx>(
             _ => unreachable!("not yet converted"),
         };
 
-        vec![Item::from_def_id_and_parts(def_id, Some(name), kind, cx)]
+        let mut extra_attrs = Vec::new();
+        if let Some(hir::Node::Item(use_node)) =
+            import_id.and_then(|hir_id| cx.tcx.hir().find(hir_id))
+        {
+            // We get all the various imports' attributes.
+            get_all_import_attributes(use_node, cx.tcx, item.hir_id(), &mut extra_attrs);
+        }
+
+        if !extra_attrs.is_empty() {
+            extra_attrs.extend_from_slice(inline::load_attrs(cx, def_id));
+            let attrs = Attributes::from_ast(&extra_attrs);
+            let cfg = extra_attrs.cfg(cx.tcx, &cx.cache.hidden_cfg);
+
+            vec![Item::from_def_id_and_attrs_and_parts(
+                def_id,
+                Some(name),
+                kind,
+                Box::new(attrs),
+                cfg,
+            )]
+        } else {
+            vec![Item::from_def_id_and_parts(def_id, Some(name), kind, cx)]
+        }
     })
 }
 
 fn clean_variant<'tcx>(variant: &hir::Variant<'tcx>, cx: &mut DocContext<'tcx>) -> Item {
     let kind = VariantItem(clean_variant_data(&variant.data, &variant.disr_expr, cx));
-    let what_rustc_thinks =
-        Item::from_hir_id_and_parts(variant.id, Some(variant.ident.name), kind, cx);
-    // don't show `pub` for variants, which are always public
-    Item { visibility: Inherited, ..what_rustc_thinks }
+    Item::from_hir_id_and_parts(variant.hir_id, Some(variant.ident.name), kind, cx)
 }
 
 fn clean_impl<'tcx>(
@@ -2114,6 +2258,7 @@ fn clean_extern_crate<'tcx>(
                 }
         });
 
+    let krate_owner_def_id = krate.owner_id.to_def_id();
     if please_inline {
         let mut visited = FxHashSet::default();
 
@@ -2122,7 +2267,7 @@ fn clean_extern_crate<'tcx>(
         if let Some(items) = inline::try_inline(
             cx,
             cx.tcx.parent_module(krate.hir_id()).to_def_id(),
-            Some(krate.owner_id.to_def_id()),
+            Some(krate_owner_def_id),
             res,
             name,
             Some(attrs),
@@ -2137,15 +2282,35 @@ fn clean_extern_crate<'tcx>(
         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),
+        inline_stmt_id: Some(krate_owner_def_id),
     }]
 }
 
 fn clean_use_statement<'tcx>(
     import: &hir::Item<'tcx>,
     name: Symbol,
+    path: &hir::UsePath<'tcx>,
+    kind: hir::UseKind,
+    cx: &mut DocContext<'tcx>,
+    inlined_names: &mut FxHashSet<(ItemType, Symbol)>,
+) -> Vec<Item> {
+    let mut items = Vec::new();
+    let hir::UsePath { segments, ref res, span } = *path;
+    for &res in res {
+        if let Res::Def(DefKind::Ctor(..), _) | Res::SelfCtor(..) = res {
+            continue;
+        }
+        let path = hir::Path { segments, res, span };
+        items.append(&mut clean_use_statement_inner(import, name, &path, kind, cx, inlined_names));
+    }
+    items
+}
+
+fn clean_use_statement_inner<'tcx>(
+    import: &hir::Item<'tcx>,
+    name: Symbol,
     path: &hir::Path<'tcx>,
     kind: hir::UseKind,
     cx: &mut DocContext<'tcx>,
diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
index 1bcb9fcd5..e96a9bab7 100644
--- a/src/librustdoc/clean/simplify.rs
+++ b/src/librustdoc/clean/simplify.rs
@@ -14,13 +14,14 @@
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty;
+use thin_vec::ThinVec;
 
 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> {
+pub(crate) fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> ThinVec<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
@@ -50,16 +51,13 @@ pub(crate) fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> Vec<WP> {
         let Some((bounds, _)) = tybounds.get_mut(ty) else { return true };
         let bound_params = bound_params
             .into_iter()
-            .map(|param| clean::GenericParamDef {
-                name: param.0,
-                kind: clean::GenericParamDefKind::Lifetime { outlives: Vec::new() },
-            })
+            .map(|param| clean::GenericParamDef::lifetime(param.0))
             .collect();
         merge_bounds(cx, bounds, bound_params, trait_did, name, rhs)
     });
 
     // And finally, let's reassemble everything
-    let mut clauses = Vec::new();
+    let mut clauses = ThinVec::with_capacity(lifetimes.len() + tybounds.len() + equalities.len());
     clauses.extend(
         lifetimes.into_iter().map(|(lt, bounds)| WP::RegionPredicate { lifetime: lt, bounds }),
     );
@@ -98,9 +96,8 @@ pub(crate) fn merge_bounds(
         let last = trait_ref.trait_.segments.last_mut().expect("segments were empty");
 
         trait_ref.generic_params.append(&mut bound_params);
-        // Since the parameters (probably) originate from `tcx.collect_*_late_bound_regions` which
-        // returns a hash set, sort them alphabetically to guarantee a stable and deterministic
-        // output (and to fully deduplicate them).
+        // Sort parameters (likely) originating from a hashset alphabetically to
+        // produce predictable output (and to allow for full deduplication).
         trait_ref.generic_params.sort_unstable_by(|p, q| p.name.as_str().cmp(q.name.as_str()));
         trait_ref.generic_params.dedup_by_key(|p| p.name);
 
@@ -135,7 +132,7 @@ fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId, trait_: DefId)
         .predicates
         .iter()
         .filter_map(|(pred, _)| {
-            if let ty::PredicateKind::Trait(pred) = pred.kind().skip_binder() {
+            if let ty::PredicateKind::Clause(ty::Clause::Trait(pred)) = pred.kind().skip_binder() {
                 if pred.trait_ref.self_ty() == self_ty { Some(pred.def_id()) } else { None }
             } else {
                 None
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index cd1f972dc..2590bb0df 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -24,7 +24,7 @@ use rustc_hir::{BodyId, Mutability};
 use rustc_hir_analysis::check::intrinsic::intrinsic_operation_unsafety;
 use rustc_index::vec::IndexVec;
 use rustc_middle::ty::fast_reject::SimplifiedType;
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, TyCtxt, Visibility};
 use rustc_session::Session;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::DUMMY_SP;
@@ -34,7 +34,6 @@ use rustc_target::abi::VariantIdx;
 use rustc_target::spec::abi::Abi;
 
 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};
@@ -51,7 +50,6 @@ 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;
@@ -117,7 +115,6 @@ impl From<DefId> for ItemId {
 #[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, Trait>>>,
 }
@@ -245,7 +242,9 @@ impl ExternalCrate {
                         hir::ItemKind::Use(path, hir::UseKind::Single)
                             if tcx.visibility(id.owner_id).is_public() =>
                         {
-                            as_keyword(path.res.expect_non_local())
+                            path.res
+                                .iter()
+                                .find_map(|res| as_keyword(res.expect_non_local()))
                                 .map(|(_, prim)| (id.owner_id.to_def_id(), prim))
                         }
                         _ => None,
@@ -313,10 +312,11 @@ impl ExternalCrate {
                         hir::ItemKind::Use(path, hir::UseKind::Single)
                             if tcx.visibility(id.owner_id).is_public() =>
                         {
-                            as_primitive(path.res.expect_non_local()).map(|(_, prim)| {
+                            path.res
+                                .iter()
+                                .find_map(|res| as_primitive(res.expect_non_local()))
                                 // Pretend the primitive is local.
-                                (id.owner_id.to_def_id(), prim)
-                            })
+                                .map(|(_, prim)| (id.owner_id.to_def_id(), prim))
                         }
                         _ => None,
                     }
@@ -348,12 +348,12 @@ pub(crate) struct 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,
-
+    /// This is the `DefId` of the `use` statement if the item was inlined.
+    pub(crate) inline_stmt_id: Option<DefId>,
     pub(crate) cfg: Option<Arc<Cfg>>,
 }
 
@@ -364,9 +364,7 @@ impl fmt::Debug for Item {
         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);
+        fmt.field("name", &self.name).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);
@@ -388,6 +386,15 @@ pub(crate) fn rustc_span(def_id: DefId, tcx: TyCtxt<'_>) -> Span {
     ))
 }
 
+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),
+    }
+}
+
 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))
@@ -462,7 +469,6 @@ impl Item {
             name,
             kind,
             Box::new(Attributes::from_ast(ast_attrs)),
-            cx,
             ast_attrs.cfg(cx.tcx, &cx.cache.hidden_cfg),
         )
     }
@@ -472,21 +478,18 @@ impl Item {
         name: Option<Symbol>,
         kind: ItemKind,
         attrs: Box<Attributes>,
-        cx: &mut DocContext<'_>,
         cfg: Option<Arc<Cfg>>,
     ) -> Item {
         trace!("name={:?}, def_id={:?} cfg={:?}", name, def_id, cfg);
 
-        // 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 }
+        Item {
+            item_id: def_id.into(),
+            kind: Box::new(kind),
+            name,
+            attrs,
+            cfg,
+            inline_stmt_id: None,
+        }
     }
 
     /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
@@ -691,17 +694,61 @@ impl Item {
                     asyncness: hir::IsAsync::NotAsync,
                 }
             }
-            ItemKind::FunctionItem(_) | ItemKind::MethodItem(_, _) => {
+            ItemKind::FunctionItem(_) | ItemKind::MethodItem(_, _) | ItemKind::TyMethodItem(_) => {
                 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)
     }
+
+    /// Returns the visibility of the current item. If the visibility is "inherited", then `None`
+    /// is returned.
+    pub(crate) fn visibility(&self, tcx: TyCtxt<'_>) -> Option<Visibility<DefId>> {
+        let def_id = match self.item_id {
+            // Anything but DefId *shouldn't* matter, but return a reasonable value anyway.
+            ItemId::Auto { .. } | ItemId::Blanket { .. } => return None,
+            // 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.
+            ItemId::Primitive(..) => return Some(Visibility::Public),
+            ItemId::DefId(def_id) => def_id,
+        };
+
+        match *self.kind {
+            // Explication on `ItemId::Primitive` just above.
+            ItemKind::KeywordItem | ItemKind::PrimitiveItem(_) => return Some(Visibility::Public),
+            // Variant fields inherit their enum's visibility.
+            StructFieldItem(..) if is_field_vis_inherited(tcx, def_id) => {
+                return None;
+            }
+            // Variants always inherit visibility
+            VariantItem(..) => return None,
+            // Trait items inherit the trait's visibility
+            AssocConstItem(..) | TyAssocConstItem(..) | AssocTypeItem(..) | TyAssocTypeItem(..)
+            | TyMethodItem(..) | MethodItem(..) => {
+                let assoc_item = tcx.associated_item(def_id);
+                let is_trait_item = match assoc_item.container {
+                    ty::TraitContainer => true,
+                    ty::ImplContainer => {
+                        // Trait impl items always inherit the impl's visibility --
+                        // we don't want to show `pub`.
+                        tcx.impl_trait_ref(tcx.parent(assoc_item.def_id)).is_some()
+                    }
+                };
+                if is_trait_item {
+                    return None;
+                }
+            }
+            _ => {}
+        }
+        let def_id = match self.inline_stmt_id {
+            Some(inlined) => inlined,
+            None => def_id,
+        };
+        Some(tcx.visibility(def_id))
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -747,7 +794,7 @@ pub(crate) enum ItemKind {
     /// 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>),
+    TyAssocTypeItem(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
@@ -1261,7 +1308,7 @@ impl Attributes {
         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 {
+                    match l.lit().unwrap().kind {
                         ast::LitKind::Str(s, _) => {
                             aliases.insert(s);
                         }
@@ -1392,6 +1439,10 @@ pub(crate) struct GenericParamDef {
 }
 
 impl GenericParamDef {
+    pub(crate) fn lifetime(name: Symbol) -> Self {
+        Self { name, kind: GenericParamDefKind::Lifetime { outlives: Vec::new() } }
+    }
+
     pub(crate) fn is_synthetic_type_param(&self) -> bool {
         match self.kind {
             GenericParamDefKind::Lifetime { .. } | GenericParamDefKind::Const { .. } => false,
@@ -1414,8 +1465,8 @@ impl GenericParamDef {
 // 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>,
+    pub(crate) params: ThinVec<GenericParamDef>,
+    pub(crate) where_predicates: ThinVec<WherePredicate>,
 }
 
 impl Generics {
@@ -1576,7 +1627,7 @@ pub(crate) enum Type {
     /// An array type.
     ///
     /// The `String` field is a stringified version of the array's length parameter.
-    Array(Box<Type>, String),
+    Array(Box<Type>, Box<str>),
     /// A raw pointer type: `*const i32`, `*mut i32`
     RawPointer(Mutability, Box<Type>),
     /// A reference type: `&i32`, `&'a mut Foo`
@@ -2030,27 +2081,9 @@ impl From<hir::PrimTy> for PrimitiveType {
     }
 }
 
-#[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) ctor_kind: Option<CtorKind>,
     pub(crate) generics: Generics,
     pub(crate) fields: Vec<Item>,
 }
@@ -2078,7 +2111,7 @@ impl Union {
 /// only as a variant in an enum.
 #[derive(Clone, Debug)]
 pub(crate) struct VariantStruct {
-    pub(crate) struct_type: CtorKind,
+    pub(crate) ctor_kind: Option<CtorKind>,
     pub(crate) fields: Vec<Item>,
 }
 
@@ -2179,7 +2212,7 @@ impl Span {
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct Path {
     pub(crate) res: Res,
-    pub(crate) segments: Vec<PathSegment>,
+    pub(crate) segments: ThinVec<PathSegment>,
 }
 
 impl Path {
@@ -2329,7 +2362,7 @@ pub(crate) enum ConstantKind {
     ///
     /// 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 },
+    TyConst { expr: Box<str> },
     /// 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.
@@ -2357,7 +2390,7 @@ impl Constant {
 impl ConstantKind {
     pub(crate) fn expr(&self, tcx: TyCtxt<'_>) -> String {
         match *self {
-            ConstantKind::TyConst { ref expr } => expr.clone(),
+            ConstantKind::TyConst { ref expr } => expr.to_string(),
             ConstantKind::Extern { def_id } => print_inlined_const(tcx, def_id),
             ConstantKind::Local { body, .. } | ConstantKind::Anonymous { body } => {
                 print_const_expr(tcx, body)
@@ -2541,14 +2574,15 @@ mod size_asserts {
     use super::*;
     use rustc_data_structures::static_assert_size;
     // tidy-alphabetical-start
-    static_assert_size!(Crate, 72); // frequently moved by-value
+    static_assert_size!(Crate, 64); // frequently moved by-value
     static_assert_size!(DocFragment, 32);
-    static_assert_size!(GenericArg, 48);
+    static_assert_size!(GenericArg, 32);
     static_assert_size!(GenericArgs, 32);
     static_assert_size!(GenericParamDef, 56);
+    static_assert_size!(Generics, 16);
     static_assert_size!(Item, 56);
-    static_assert_size!(ItemKind, 88);
+    static_assert_size!(ItemKind, 64);
     static_assert_size!(PathSegment, 40);
-    static_assert_size!(Type, 48);
+    static_assert_size!(Type, 32);
     // tidy-alphabetical-end
 }
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 58767d3a4..246560bad 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -4,10 +4,10 @@ use crate::clean::render_macro_matchers::render_macro_matcher;
 use crate::clean::{
     clean_doc_module, clean_middle_const, clean_middle_region, clean_middle_ty, inline, Crate,
     ExternalCrate, Generic, GenericArg, GenericArgs, ImportSource, Item, ItemKind, Lifetime, Path,
-    PathSegment, Primitive, PrimitiveType, Type, TypeBinding, Visibility,
+    PathSegment, Primitive, PrimitiveType, Term, Type, TypeBinding, TypeBindingKind,
 };
 use crate::core::DocContext;
-use crate::visit_lib::LibEmbargoVisitor;
+use crate::html::format::visibility_to_src_with_space;
 
 use rustc_ast as ast;
 use rustc_ast::tokenstream::TokenTree;
@@ -21,7 +21,7 @@ use rustc_middle::ty::{self, DefIdTree, TyCtxt};
 use rustc_span::symbol::{kw, sym, Symbol};
 use std::fmt::Write as _;
 use std::mem;
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 #[cfg(test)]
 mod tests;
@@ -31,7 +31,7 @@ pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
 
     for &cnum in cx.tcx.crates(()) {
         // Analyze doc-reachability for extern items
-        LibEmbargoVisitor::new(cx).visit_lib(cnum);
+        crate::visit_lib::lib_embargo_visit_item(cx, cnum.as_def_id());
     }
 
     // Clean the crate, translating the entire librustc_ast AST to one that is
@@ -73,7 +73,7 @@ pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
         }));
     }
 
-    Crate { module, primitives, external_traits: cx.external_traits.clone() }
+    Crate { module, external_traits: cx.external_traits.clone() }
 }
 
 pub(crate) fn substs_to_args<'tcx>(
@@ -106,19 +106,19 @@ fn external_generic_args<'tcx>(
 ) -> GenericArgs {
     let args = substs_to_args(cx, substs, has_self);
 
-    if cx.tcx.fn_trait_kind_from_lang_item(did).is_some() {
+    if cx.tcx.fn_trait_kind_from_def_id(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 },
             };
-        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))
-        // };
+        let output = bindings.into_iter().next().and_then(|binding| match binding.kind {
+            TypeBindingKind::Equality { term: Term::Type(ty) } if ty != Type::Tuple(Vec::new()) => {
+                Some(Box::new(ty))
+            }
+            _ => None,
+        });
         GenericArgs::Parenthesized { inputs, output }
     } else {
         GenericArgs::AngleBracketed { args: args.into(), bindings: bindings.into() }
@@ -136,7 +136,7 @@ pub(super) fn external_path<'tcx>(
     let name = cx.tcx.item_name(did);
     Path {
         res: Res::Def(def_kind, did),
-        segments: vec![PathSegment {
+        segments: thin_vec![PathSegment {
             name,
             args: external_generic_args(cx, did, has_self, bindings, substs),
         }],
@@ -242,19 +242,13 @@ pub(crate) fn print_const(cx: &DocContext<'_>, n: ty::Const<'_>) -> String {
 
             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
+        // array lengths are obviously usize
+        ty::ConstKind::Value(ty::ValTree::Leaf(scalar))
+            if *n.ty().kind() == ty::Uint(ty::UintTy::Usize) =>
+        {
+            scalar.to_string()
         }
+        _ => n.to_string(),
     }
 }
 
@@ -584,9 +578,9 @@ pub(super) fn display_macro_source(
     name: Symbol,
     def: &ast::MacroDef,
     def_id: DefId,
-    vis: Visibility,
+    vis: ty::Visibility<DefId>,
 ) -> String {
-    let tts: Vec<_> = def.body.inner_tokens().into_trees().collect();
+    let tts: Vec<_> = def.body.tokens.clone().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]);
 
@@ -596,14 +590,14 @@ pub(super) fn display_macro_source(
         if matchers.len() <= 1 {
             format!(
                 "{}macro {}{} {{\n    ...\n}}",
-                vis.to_src_with_space(cx.tcx, def_id),
+                visibility_to_src_with_space(Some(vis), 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),
+                visibility_to_src_with_space(Some(vis), cx.tcx, def_id),
                 name,
                 render_macro_arms(cx.tcx, matchers, ","),
             )