Adding upstream version 1.69.0+dfsg1.upstream/1.69.0+dfsg1

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

87 files changed, 3136 insertions, 3327 deletions

diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index 543bd56a2..a2b78cc29 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -34,7 +34,7 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_type_ir = { path = "../rustc_type_ir" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec = "0.2.9"
+thin-vec = "0.2.12"
 tracing = "0.1"
 
 [features]
diff --git a/compiler/rustc_error_messages/locales/en-US/middle.ftl b/compiler/rustc_middle/locales/en-US.ftl
index 4f4e5c6a2..4f4e5c6a2 100644
--- a/compiler/rustc_error_messages/locales/en-US/middle.ftl
+++ b/compiler/rustc_middle/locales/en-US.ftl
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index f816d6145..62e44b629 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -8,7 +8,7 @@
 macro_rules! arena_types {
     ($macro:path) => (
         $macro!([
-            [] layout: rustc_target::abi::LayoutS<rustc_target::abi::VariantIdx>,
+            [] layout: rustc_target::abi::LayoutS,
             [] fn_abi: rustc_target::abi::call::FnAbi<'tcx, rustc_middle::ty::Ty<'tcx>>,
             // AdtDef are interned and compared by address
             [decode] adt_def: rustc_middle::ty::AdtDefData,
@@ -35,6 +35,8 @@ macro_rules! arena_types {
                 rustc_data_structures::sync::Lrc<rustc_ast::Crate>,
             )>,
             [] output_filenames: std::sync::Arc<rustc_session::config::OutputFilenames>,
+            [] metadata_loader: rustc_data_structures::steal::Steal<Box<rustc_session::cstore::MetadataLoaderDyn>>,
+            [] crate_for_resolver: rustc_data_structures::steal::Steal<rustc_ast::ast::Crate>,
             [] resolutions: rustc_middle::ty::ResolverGlobalCtxt,
             [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult,
             [decode] code_region: rustc_middle::mir::coverage::CodeRegion,
@@ -105,13 +107,16 @@ macro_rules! arena_types {
             // (during lowering) and the `librustc_middle` arena (for decoding MIR)
             [decode] asm_template: rustc_ast::InlineAsmTemplatePiece,
             [decode] used_trait_imports: rustc_data_structures::unord::UnordSet<rustc_hir::def_id::LocalDefId>,
-            [decode] is_late_bound_map: rustc_data_structures::fx::FxIndexSet<rustc_hir::def_id::LocalDefId>,
+            [decode] is_late_bound_map: rustc_data_structures::fx::FxIndexSet<rustc_hir::ItemLocalId>,
             [decode] impl_source: rustc_middle::traits::ImplSource<'tcx, ()>,
 
             [] dep_kind: rustc_middle::dep_graph::DepKindStruct<'tcx>,
 
             [decode] trait_impl_trait_tys: rustc_data_structures::fx::FxHashMap<rustc_hir::def_id::DefId, rustc_middle::ty::Ty<'tcx>>,
             [] bit_set_u32: rustc_index::bit_set::BitSet<u32>,
+            [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<'tcx>,
+            [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
+            [] closure_kind_origin: (rustc_span::Span, rustc_middle::hir::place::Place<'tcx>),
         ]);
     )
 }
diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 2e62bebc8..84510fe21 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -55,7 +55,7 @@ impl rustc_query_system::dep_graph::DepKind for DepKind {
         ty::tls::with_context(|icx| {
             let icx = ty::tls::ImplicitCtxt { task_deps, ..icx.clone() };
 
-            ty::tls::enter_context(&icx, |_| op())
+            ty::tls::enter_context(&icx, op)
         })
     }
 
@@ -74,8 +74,8 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
     type DepKind = DepKind;
 
     #[inline]
-    fn with_stable_hashing_context<R>(&self, f: impl FnOnce(StableHashingContext<'_>) -> R) -> R {
-        TyCtxt::with_stable_hashing_context(*self, f)
+    fn with_stable_hashing_context<R>(self, f: impl FnOnce(StableHashingContext<'_>) -> R) -> R {
+        TyCtxt::with_stable_hashing_context(self, f)
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 9e63c2bd2..4b5bacac8 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -18,24 +18,30 @@ use rustc_span::Span;
 use rustc_target::spec::abi::Abi;
 
 #[inline]
-pub fn associated_body(node: Node<'_>) -> Option<BodyId> {
+pub fn associated_body(node: Node<'_>) -> Option<(LocalDefId, BodyId)> {
     match node {
         Node::Item(Item {
+            owner_id,
             kind: ItemKind::Const(_, body) | ItemKind::Static(.., body) | ItemKind::Fn(.., body),
             ..
         })
         | Node::TraitItem(TraitItem {
+            owner_id,
             kind:
                 TraitItemKind::Const(_, Some(body)) | TraitItemKind::Fn(_, TraitFn::Provided(body)),
             ..
         })
         | Node::ImplItem(ImplItem {
+            owner_id,
             kind: ImplItemKind::Const(_, body) | ImplItemKind::Fn(_, body),
             ..
-        })
-        | Node::Expr(Expr { kind: ExprKind::Closure(Closure { body, .. }), .. }) => Some(*body),
+        }) => Some((owner_id.def_id, *body)),
+
+        Node::Expr(Expr { kind: ExprKind::Closure(Closure { def_id, body, .. }), .. }) => {
+            Some((*def_id, *body))
+        }
 
-        Node::AnonConst(constant) => Some(constant.body),
+        Node::AnonConst(constant) => Some((constant.def_id, constant.body)),
 
         _ => None,
     }
@@ -43,7 +49,7 @@ pub fn associated_body(node: Node<'_>) -> Option<BodyId> {
 
 fn is_body_owner(node: Node<'_>, hir_id: HirId) -> bool {
     match associated_body(node) {
-        Some(b) => b.hir_id == hir_id,
+        Some((_, b)) => b.hir_id == hir_id,
         None => false,
     }
 }
@@ -154,10 +160,6 @@ impl<'hir> Map<'hir> {
         self.tcx.definitions_untracked().def_key(def_id)
     }
 
-    pub fn def_path_from_hir_id(self, id: HirId) -> Option<DefPath> {
-        self.opt_local_def_id(id).map(|def_id| self.def_path(def_id))
-    }
-
     pub fn def_path(self, def_id: LocalDefId) -> DefPath {
         // Accessing the DefPath is ok, since it is part of DefPathHash.
         self.tcx.definitions_untracked().def_path(def_id)
@@ -170,32 +172,6 @@ impl<'hir> Map<'hir> {
     }
 
     #[inline]
-    #[track_caller]
-    pub fn local_def_id(self, hir_id: HirId) -> LocalDefId {
-        self.opt_local_def_id(hir_id).unwrap_or_else(|| {
-            bug!(
-                "local_def_id: no entry for `{:?}`, which has a map of `{:?}`",
-                hir_id,
-                self.find(hir_id)
-            )
-        })
-    }
-
-    #[inline]
-    pub fn opt_local_def_id(self, hir_id: HirId) -> Option<LocalDefId> {
-        if hir_id.local_id == ItemLocalId::new(0) {
-            Some(hir_id.owner.def_id)
-        } else {
-            self.tcx
-                .hir_owner_nodes(hir_id.owner)
-                .as_owner()?
-                .local_id_to_def_id
-                .get(&hir_id.local_id)
-                .copied()
-        }
-    }
-
-    #[inline]
     pub fn local_def_id_to_hir_id(self, def_id: LocalDefId) -> HirId {
         self.tcx.local_def_id_to_hir_id(def_id)
     }
@@ -227,7 +203,7 @@ impl<'hir> Map<'hir> {
                 ItemKind::Use(..) => DefKind::Use,
                 ItemKind::ForeignMod { .. } => DefKind::ForeignMod,
                 ItemKind::GlobalAsm(..) => DefKind::GlobalAsm,
-                ItemKind::Impl { .. } => DefKind::Impl,
+                ItemKind::Impl(impl_) => DefKind::Impl { of_trait: impl_.of_trait.is_some() },
             },
             Node::ForeignItem(item) => match item.kind {
                 ForeignItemKind::Fn(..) => DefKind::Fn,
@@ -314,7 +290,7 @@ impl<'hir> Map<'hir> {
     #[track_caller]
     pub fn parent_id(self, hir_id: HirId) -> HirId {
         self.opt_parent_id(hir_id)
-            .unwrap_or_else(|| bug!("No parent for node {:?}", self.node_to_string(hir_id)))
+            .unwrap_or_else(|| bug!("No parent for node {}", self.node_to_string(hir_id)))
     }
 
     pub fn get_parent(self, hir_id: HirId) -> Node<'hir> {
@@ -410,8 +386,8 @@ impl<'hir> Map<'hir> {
     #[track_caller]
     pub fn enclosing_body_owner(self, hir_id: HirId) -> LocalDefId {
         for (_, node) in self.parent_iter(hir_id) {
-            if let Some(body) = associated_body(node) {
-                return self.body_owner_def_id(body);
+            if let Some((def_id, _)) = associated_body(node) {
+                return def_id;
             }
         }
 
@@ -427,14 +403,17 @@ impl<'hir> Map<'hir> {
         parent
     }
 
-    pub fn body_owner_def_id(self, id: BodyId) -> LocalDefId {
-        self.local_def_id(self.body_owner(id))
+    pub fn body_owner_def_id(self, BodyId { hir_id }: BodyId) -> LocalDefId {
+        let parent = self.parent_id(hir_id);
+        associated_body(self.get(parent)).unwrap().0
     }
 
     /// Given a `LocalDefId`, returns the `BodyId` associated with it,
     /// if the node is a body owner, otherwise returns `None`.
     pub fn maybe_body_owned_by(self, id: LocalDefId) -> Option<BodyId> {
-        self.find_by_def_id(id).and_then(associated_body)
+        let node = self.find_by_def_id(id)?;
+        let (_, body_id) = associated_body(node)?;
+        Some(body_id)
     }
 
     /// Given a body owner's id, returns the `BodyId` associated with it.
@@ -870,6 +849,13 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    pub fn get_fn_output(self, def_id: LocalDefId) -> Option<&'hir FnRetTy<'hir>> {
+        match self.tcx.hir_owner(OwnerId { def_id }) {
+            Some(Owner { node, .. }) => node.fn_decl().map(|fn_decl| &fn_decl.output),
+            _ => None,
+        }
+    }
+
     pub fn expect_variant(self, id: HirId) -> &'hir Variant<'hir> {
         match self.find(id) {
             Some(Node::Variant(variant)) => variant,
@@ -917,6 +903,11 @@ impl<'hir> Map<'hir> {
     }
 
     #[inline]
+    pub fn ident(self, id: HirId) -> Ident {
+        self.opt_ident(id).unwrap()
+    }
+
+    #[inline]
     pub fn opt_name(self, id: HirId) -> Option<Symbol> {
         self.opt_ident(id).map(|ident| ident.name)
     }
@@ -1083,7 +1074,7 @@ impl<'hir> Map<'hir> {
     }
 
     pub fn span_if_local(self, id: DefId) -> Option<Span> {
-        if id.is_local() { Some(self.tcx.def_span(id)) } else { None }
+        id.is_local().then(|| self.tcx.def_span(id))
     }
 
     pub fn res_span(self, res: Res) -> Option<Span> {
@@ -1212,12 +1203,10 @@ fn upstream_crates(tcx: TyCtxt<'_>) -> Vec<(StableCrateId, Svh)> {
 }
 
 fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
-    let id_str = format!(" (hir_id={})", id);
-
     let path_str = |def_id: LocalDefId| map.tcx.def_path_str(def_id.to_def_id());
 
     let span_str = || map.tcx.sess.source_map().span_to_snippet(map.span(id)).unwrap_or_default();
-    let node_str = |prefix| format!("{} {}{}", prefix, span_str(), id_str);
+    let node_str = |prefix| format!("{id} ({prefix} `{}`)", span_str());
 
     match map.find(id) {
         Some(Node::Item(item)) => {
@@ -1246,10 +1235,10 @@ fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
                 ItemKind::TraitAlias(..) => "trait alias",
                 ItemKind::Impl { .. } => "impl",
             };
-            format!("{} {}{}", item_str, path_str(item.owner_id.def_id), id_str)
+            format!("{id} ({item_str} {})", path_str(item.owner_id.def_id))
         }
         Some(Node::ForeignItem(item)) => {
-            format!("foreign item {}{}", path_str(item.owner_id.def_id), id_str)
+            format!("{id} (foreign item {})", path_str(item.owner_id.def_id))
         }
         Some(Node::ImplItem(ii)) => {
             let kind = match ii.kind {
@@ -1257,7 +1246,7 @@ fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
                 ImplItemKind::Fn(..) => "method",
                 ImplItemKind::Type(_) => "assoc type",
             };
-            format!("{} {} in {}{}", kind, ii.ident, path_str(ii.owner_id.def_id), id_str)
+            format!("{id} ({kind} `{}` in {})", ii.ident, path_str(ii.owner_id.def_id))
         }
         Some(Node::TraitItem(ti)) => {
             let kind = match ti.kind {
@@ -1266,13 +1255,13 @@ fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
                 TraitItemKind::Type(..) => "assoc type",
             };
 
-            format!("{} {} in {}{}", kind, ti.ident, path_str(ti.owner_id.def_id), id_str)
+            format!("{id} ({kind} `{}` in {})", ti.ident, path_str(ti.owner_id.def_id))
         }
         Some(Node::Variant(ref variant)) => {
-            format!("variant {} in {}{}", variant.ident, path_str(variant.def_id), id_str)
+            format!("{id} (variant `{}` in {})", variant.ident, path_str(variant.def_id))
         }
         Some(Node::Field(ref field)) => {
-            format!("field {} in {}{}", field.ident, path_str(field.def_id), id_str)
+            format!("{id} (field `{}` in {})", field.ident, path_str(field.def_id))
         }
         Some(Node::AnonConst(_)) => node_str("const"),
         Some(Node::Expr(_)) => node_str("expr"),
@@ -1290,16 +1279,15 @@ fn hir_id_to_string(map: Map<'_>, id: HirId) -> String {
         Some(Node::Infer(_)) => node_str("infer"),
         Some(Node::Local(_)) => node_str("local"),
         Some(Node::Ctor(ctor)) => format!(
-            "ctor {}{}",
+            "{id} (ctor {})",
             ctor.ctor_def_id().map_or("<missing path>".into(), |def_id| path_str(def_id)),
-            id_str
         ),
         Some(Node::Lifetime(_)) => node_str("lifetime"),
         Some(Node::GenericParam(ref param)) => {
-            format!("generic_param {}{}", path_str(param.def_id), id_str)
+            format!("{id} (generic_param {})", path_str(param.def_id))
         }
-        Some(Node::Crate(..)) => String::from("root_crate"),
-        None => format!("unknown node{}", id_str),
+        Some(Node::Crate(..)) => String::from("(root_crate)"),
+        None => format!("{id} (unknown node)"),
     }
 }
 
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index dedc65f4c..c9da711e5 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -64,13 +64,17 @@ impl ModuleItems {
         self.foreign_items.iter().copied()
     }
 
-    pub fn definitions(&self) -> impl Iterator<Item = LocalDefId> + '_ {
+    pub fn owners(&self) -> impl Iterator<Item = OwnerId> + '_ {
         self.items
             .iter()
-            .map(|id| id.owner_id.def_id)
-            .chain(self.trait_items.iter().map(|id| id.owner_id.def_id))
-            .chain(self.impl_items.iter().map(|id| id.owner_id.def_id))
-            .chain(self.foreign_items.iter().map(|id| id.owner_id.def_id))
+            .map(|id| id.owner_id)
+            .chain(self.trait_items.iter().map(|id| id.owner_id))
+            .chain(self.impl_items.iter().map(|id| id.owner_id))
+            .chain(self.foreign_items.iter().map(|id| id.owner_id))
+    }
+
+    pub fn definitions(&self) -> impl Iterator<Item = LocalDefId> + '_ {
+        self.owners().map(|id| id.def_id)
     }
 
     pub fn par_items(&self, f: impl Fn(ItemId) + Send + Sync) {
@@ -104,7 +108,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self.impl_trait_ref(def_id)
             .map(|t| t.subst_identity())
             .map(ImplSubject::Trait)
-            .unwrap_or_else(|| ImplSubject::Inherent(self.type_of(def_id)))
+            .unwrap_or_else(|| ImplSubject::Inherent(self.type_of(def_id).subst_identity()))
     }
 }
 
@@ -121,13 +125,13 @@ pub fn provide(providers: &mut Providers) {
         let node = owner.node();
         Some(Owner { node, hash_without_bodies: owner.nodes.hash_without_bodies })
     };
-    providers.local_def_id_to_hir_id = |tcx, id| {
+    providers.opt_local_def_id_to_hir_id = |tcx, id| {
         let owner = tcx.hir_crate(()).owners[id].map(|_| ());
-        match owner {
+        Some(match owner {
             MaybeOwner::Owner(_) => HirId::make_owner(id),
             MaybeOwner::Phantom => bug!("No HirId for {:?}", id),
             MaybeOwner::NonOwner(hir_id) => hir_id,
-        }
+        })
     };
     providers.hir_owner_nodes = |tcx, id| tcx.hir_crate(()).owners[id.def_id].map(|i| &i.nodes);
     providers.hir_owner_parent = |tcx, id| {
@@ -173,6 +177,7 @@ pub fn provide(providers: &mut Providers) {
         }
     };
     providers.opt_def_kind = |tcx, def_id| tcx.hir().opt_def_kind(def_id.expect_local());
+    providers.opt_rpitit_info = |_, _| None;
     providers.all_local_trait_impls = |tcx, ()| &tcx.resolutions(()).trait_impls;
     providers.expn_that_defined = |tcx, id| {
         let id = id.expect_local();
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 43583b572..7f8fc1774 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -25,10 +25,8 @@ use crate::infer::MemberConstraint;
 use crate::mir::ConstraintCategory;
 use crate::ty::subst::GenericArg;
 use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt};
-use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use smallvec::SmallVec;
-use std::iter;
 use std::ops::Index;
 
 /// A "canonicalized" type `V` is one where all free inference
@@ -44,12 +42,12 @@ pub struct Canonical<'tcx, V> {
 
 pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo<'tcx>>;
 
-impl<'tcx> ty::TypeFoldable<'tcx> for CanonicalVarInfos<'tcx> {
-    fn try_fold_with<F: ty::FallibleTypeFolder<'tcx>>(
+impl<'tcx> ty::TypeFoldable<TyCtxt<'tcx>> for CanonicalVarInfos<'tcx> {
+    fn try_fold_with<F: ty::FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_canonical_var_infos(v))
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_canonical_var_infos(v))
     }
 }
 
@@ -62,23 +60,23 @@ impl<'tcx> ty::TypeFoldable<'tcx> for CanonicalVarInfos<'tcx> {
 /// vectors with the original values that were replaced by canonical
 /// variables. You will need to supply it later to instantiate the
 /// canonicalized query response.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct CanonicalVarValues<'tcx> {
-    pub var_values: IndexVec<BoundVar, GenericArg<'tcx>>,
+    pub var_values: ty::SubstsRef<'tcx>,
 }
 
 impl CanonicalVarValues<'_> {
     pub fn is_identity(&self) -> bool {
-        self.var_values.iter_enumerated().all(|(bv, arg)| match arg.unpack() {
+        self.var_values.iter().enumerate().all(|(bv, arg)| match arg.unpack() {
             ty::GenericArgKind::Lifetime(r) => {
-                matches!(*r, ty::ReLateBound(ty::INNERMOST, br) if br.var == bv)
+                matches!(*r, ty::ReLateBound(ty::INNERMOST, br) if br.var.as_usize() == bv)
             }
             ty::GenericArgKind::Type(ty) => {
-                matches!(*ty.kind(), ty::Bound(ty::INNERMOST, bt) if bt.var == bv)
+                matches!(*ty.kind(), ty::Bound(ty::INNERMOST, bt) if bt.var.as_usize() == bv)
             }
             ty::GenericArgKind::Const(ct) => {
-                matches!(ct.kind(), ty::ConstKind::Bound(ty::INNERMOST, bc) if bc == bv)
+                matches!(ct.kind(), ty::ConstKind::Bound(ty::INNERMOST, bc) if bc.as_usize() == bv)
             }
         })
     }
@@ -125,6 +123,11 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
         self.kind.universe()
     }
 
+    #[must_use]
+    pub fn with_updated_universe(self, ui: ty::UniverseIndex) -> CanonicalVarInfo<'tcx> {
+        CanonicalVarInfo { kind: self.kind.with_updated_universe(ui) }
+    }
+
     pub fn is_existential(&self) -> bool {
         match self.kind {
             CanonicalVarKind::Ty(_) => true,
@@ -135,6 +138,28 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
             CanonicalVarKind::PlaceholderConst(_, _) => false,
         }
     }
+
+    pub fn is_region(&self) -> bool {
+        match self.kind {
+            CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => true,
+            CanonicalVarKind::Ty(_)
+            | CanonicalVarKind::PlaceholderTy(_)
+            | CanonicalVarKind::Const(_, _)
+            | CanonicalVarKind::PlaceholderConst(_, _) => false,
+        }
+    }
+
+    pub fn expect_anon_placeholder(self) -> u32 {
+        match self.kind {
+            CanonicalVarKind::Ty(_)
+            | CanonicalVarKind::Region(_)
+            | CanonicalVarKind::Const(_, _) => bug!("expected placeholder: {self:?}"),
+
+            CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.name.expect_anon(),
+            CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.name.expect_anon(),
+            CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.name.as_u32(),
+        }
+    }
 }
 
 /// Describes the "kind" of the canonical variable. This is a "kind"
@@ -179,6 +204,38 @@ impl<'tcx> CanonicalVarKind<'tcx> {
             CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.universe,
         }
     }
+
+    /// Replaces the universe of this canonical variable with `ui`.
+    ///
+    /// In case this is a float or int variable, this causes an ICE if
+    /// the updated universe is not the root.
+    pub fn with_updated_universe(self, ui: ty::UniverseIndex) -> CanonicalVarKind<'tcx> {
+        match self {
+            CanonicalVarKind::Ty(kind) => match kind {
+                CanonicalTyVarKind::General(_) => {
+                    CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui))
+                }
+                CanonicalTyVarKind::Int | CanonicalTyVarKind::Float => {
+                    assert_eq!(ui, ty::UniverseIndex::ROOT);
+                    CanonicalVarKind::Ty(kind)
+                }
+            },
+            CanonicalVarKind::PlaceholderTy(placeholder) => {
+                CanonicalVarKind::PlaceholderTy(ty::Placeholder { universe: ui, ..placeholder })
+            }
+            CanonicalVarKind::Region(_) => CanonicalVarKind::Region(ui),
+            CanonicalVarKind::PlaceholderRegion(placeholder) => {
+                CanonicalVarKind::PlaceholderRegion(ty::Placeholder { universe: ui, ..placeholder })
+            }
+            CanonicalVarKind::Const(_, ty) => CanonicalVarKind::Const(ui, ty),
+            CanonicalVarKind::PlaceholderConst(placeholder, ty) => {
+                CanonicalVarKind::PlaceholderConst(
+                    ty::Placeholder { universe: ui, ..placeholder },
+                    ty,
+                )
+            }
+        }
+    }
 }
 
 /// Rust actually has more than one category of type variables;
@@ -215,7 +272,8 @@ pub struct QueryResponse<'tcx, R> {
     pub value: R,
 }
 
-#[derive(Clone, Debug, Default, HashStable, TypeFoldable, TypeVisitable, Lift)]
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct QueryRegionConstraints<'tcx> {
     pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
     pub member_constraints: Vec<MemberConstraint<'tcx>>,
@@ -326,10 +384,8 @@ impl<'tcx, V> Canonical<'tcx, V> {
     }
 }
 
-pub type QueryOutlivesConstraint<'tcx> = (
-    ty::Binder<'tcx, ty::OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>>,
-    ConstraintCategory<'tcx>,
-);
+pub type QueryOutlivesConstraint<'tcx> =
+    (ty::OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>, ConstraintCategory<'tcx>);
 
 TrivialTypeTraversalAndLiftImpls! {
     for <'tcx> {
@@ -339,57 +395,57 @@ TrivialTypeTraversalAndLiftImpls! {
 }
 
 impl<'tcx> CanonicalVarValues<'tcx> {
+    // Given a list of canonical variables, construct a set of values which are
+    // the identity response.
+    pub fn make_identity(
+        tcx: TyCtxt<'tcx>,
+        infos: CanonicalVarInfos<'tcx>,
+    ) -> CanonicalVarValues<'tcx> {
+        CanonicalVarValues {
+            var_values: tcx.mk_substs_from_iter(infos.iter().enumerate().map(
+                |(i, info)| -> ty::GenericArg<'tcx> {
+                    match info.kind {
+                        CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
+                            tcx.mk_bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into()).into()
+                        }
+                        CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
+                            let br = ty::BoundRegion {
+                                var: ty::BoundVar::from_usize(i),
+                                kind: ty::BrAnon(i as u32, None),
+                            };
+                            tcx.mk_re_late_bound(ty::INNERMOST, br).into()
+                        }
+                        CanonicalVarKind::Const(_, ty)
+                        | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
+                            .mk_const(
+                                ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)),
+                                ty,
+                            )
+                            .into(),
+                    }
+                },
+            )),
+        }
+    }
+
     /// Creates dummy var values which should not be used in a
     /// canonical response.
     pub fn dummy() -> CanonicalVarValues<'tcx> {
-        CanonicalVarValues { var_values: Default::default() }
+        CanonicalVarValues { var_values: ty::List::empty() }
     }
 
     #[inline]
     pub fn len(&self) -> usize {
         self.var_values.len()
     }
-
-    /// Makes an identity substitution from this one: each bound var
-    /// is matched to the same bound var, preserving the original kinds.
-    /// For example, if we have:
-    /// `self.var_values == [Type(u32), Lifetime('a), Type(u64)]`
-    /// we'll return a substitution `subst` with:
-    /// `subst.var_values == [Type(^0), Lifetime(^1), Type(^2)]`.
-    pub fn make_identity(&self, tcx: TyCtxt<'tcx>) -> Self {
-        use crate::ty::subst::GenericArgKind;
-
-        CanonicalVarValues {
-            var_values: iter::zip(&self.var_values, 0..)
-                .map(|(kind, i)| match kind.unpack() {
-                    GenericArgKind::Type(..) => {
-                        tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i).into())).into()
-                    }
-                    GenericArgKind::Lifetime(..) => {
-                        let br = ty::BoundRegion {
-                            var: ty::BoundVar::from_u32(i),
-                            kind: ty::BrAnon(i, None),
-                        };
-                        tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
-                    }
-                    GenericArgKind::Const(ct) => tcx
-                        .mk_const(
-                            ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i)),
-                            ct.ty(),
-                        )
-                        .into(),
-                })
-                .collect(),
-        }
-    }
 }
 
 impl<'a, 'tcx> IntoIterator for &'a CanonicalVarValues<'tcx> {
     type Item = GenericArg<'tcx>;
-    type IntoIter = ::std::iter::Cloned<::std::slice::Iter<'a, GenericArg<'tcx>>>;
+    type IntoIter = ::std::iter::Copied<::std::slice::Iter<'a, GenericArg<'tcx>>>;
 
     fn into_iter(self) -> Self::IntoIter {
-        self.var_values.iter().cloned()
+        self.var_values.iter()
     }
 }
 
@@ -397,6 +453,6 @@ impl<'tcx> Index<BoundVar> for CanonicalVarValues<'tcx> {
     type Output = GenericArg<'tcx>;
 
     fn index(&self, value: BoundVar) -> &GenericArg<'tcx> {
-        &self.var_values[value]
+        &self.var_values[value.as_usize()]
     }
 }
diff --git a/compiler/rustc_middle/src/infer/mod.rs b/compiler/rustc_middle/src/infer/mod.rs
index 38868c210..2db59f37f 100644
--- a/compiler/rustc_middle/src/infer/mod.rs
+++ b/compiler/rustc_middle/src/infer/mod.rs
@@ -12,7 +12,8 @@ use rustc_span::Span;
 /// ```text
 /// R0 member of [O1..On]
 /// ```
-#[derive(Debug, Clone, HashStable, TypeFoldable, TypeVisitable, Lift)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct MemberConstraint<'tcx> {
     /// The `DefId` and substs of the opaque type causing this constraint.
     /// Used for error reporting.
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 7e4063c2f..c33b9d84e 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -34,6 +34,7 @@
 #![feature(get_mut_unchecked)]
 #![feature(if_let_guard)]
 #![feature(iter_from_generator)]
+#![feature(local_key_cell_methods)]
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(extern_types)]
@@ -43,21 +44,21 @@
 #![feature(min_specialization)]
 #![feature(trusted_len)]
 #![feature(type_alias_impl_trait)]
+#![feature(strict_provenance)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
 #![feature(control_flow_enum)]
-#![feature(associated_type_defaults)]
 #![feature(trusted_step)]
 #![feature(try_blocks)]
 #![feature(try_reserve_kind)]
 #![feature(nonzero_ops)]
-#![feature(unwrap_infallible)]
 #![feature(decl_macro)]
 #![feature(drain_filter)]
 #![feature(intra_doc_pointers)]
 #![feature(yeet_expr)]
 #![feature(result_option_inspect)]
 #![feature(const_option)]
+#![feature(trait_alias)]
 #![recursion_limit = "512"]
 #![allow(rustc::potential_query_instability)]
 
@@ -72,6 +73,9 @@ extern crate tracing;
 #[macro_use]
 extern crate smallvec;
 
+use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
+use rustc_macros::fluent_messages;
+
 #[cfg(test)]
 mod tests;
 
@@ -104,3 +108,5 @@ pub mod util {
 
 // Allows macros to refer to this crate as `::rustc_middle`
 extern crate self as rustc_middle;
+
+fluent_messages! { "../locales/en-US.ftl" }
diff --git a/compiler/rustc_middle/src/macros.rs b/compiler/rustc_middle/src/macros.rs
index 250f3d079..a8d71ce03 100644
--- a/compiler/rustc_middle/src/macros.rs
+++ b/compiler/rustc_middle/src/macros.rs
@@ -69,8 +69,8 @@ macro_rules! CloneLiftImpls {
 macro_rules! TrivialTypeTraversalImpls {
     (for <$tcx:lifetime> { $($ty:ty,)+ }) => {
         $(
-            impl<$tcx> $crate::ty::fold::TypeFoldable<$tcx> for $ty {
-                fn try_fold_with<F: $crate::ty::fold::FallibleTypeFolder<$tcx>>(
+            impl<$tcx> $crate::ty::fold::TypeFoldable<$crate::ty::TyCtxt<$tcx>> for $ty {
+                fn try_fold_with<F: $crate::ty::fold::FallibleTypeFolder<$crate::ty::TyCtxt<$tcx>>>(
                     self,
                     _: &mut F,
                 ) -> ::std::result::Result<Self, F::Error> {
@@ -78,7 +78,7 @@ macro_rules! TrivialTypeTraversalImpls {
                 }
 
                 #[inline]
-                fn fold_with<F: $crate::ty::fold::TypeFolder<$tcx>>(
+                fn fold_with<F: $crate::ty::fold::TypeFolder<$crate::ty::TyCtxt<$tcx>>>(
                     self,
                     _: &mut F,
                 ) -> Self {
@@ -86,9 +86,9 @@ macro_rules! TrivialTypeTraversalImpls {
                 }
             }
 
-            impl<$tcx> $crate::ty::visit::TypeVisitable<$tcx> for $ty {
+            impl<$tcx> $crate::ty::visit::TypeVisitable<$crate::ty::TyCtxt<$tcx>> for $ty {
                 #[inline]
-                fn visit_with<F: $crate::ty::visit::TypeVisitor<$tcx>>(
+                fn visit_with<F: $crate::ty::visit::TypeVisitor<$crate::ty::TyCtxt<$tcx>>>(
                     &self,
                     _: &mut F)
                     -> ::std::ops::ControlFlow<F::BreakTy>
@@ -101,7 +101,7 @@ macro_rules! TrivialTypeTraversalImpls {
 
     ($($ty:ty,)+) => {
         TrivialTypeTraversalImpls! {
-            for <'tcx> {
+            for<'tcx> {
                 $($ty,)+
             }
         }
@@ -115,145 +115,3 @@ macro_rules! TrivialTypeTraversalAndLiftImpls {
         CloneLiftImpls! { $($t)* }
     }
 }
-
-#[macro_export]
-macro_rules! EnumTypeTraversalImpl {
-    (impl<$($p:tt),*> TypeFoldable<$tcx:tt> for $s:path {
-        $($variants:tt)*
-    } $(where $($wc:tt)*)*) => {
-        impl<$($p),*> $crate::ty::fold::TypeFoldable<$tcx> for $s
-            $(where $($wc)*)*
-        {
-            fn try_fold_with<V: $crate::ty::fold::FallibleTypeFolder<$tcx>>(
-                self,
-                folder: &mut V,
-            ) -> ::std::result::Result<Self, V::Error> {
-                EnumTypeTraversalImpl!(@FoldVariants(self, folder) input($($variants)*) output())
-            }
-        }
-    };
-
-    (impl<$($p:tt),*> TypeVisitable<$tcx:tt> for $s:path {
-        $($variants:tt)*
-    } $(where $($wc:tt)*)*) => {
-        impl<$($p),*> $crate::ty::visit::TypeVisitable<$tcx> for $s
-            $(where $($wc)*)*
-        {
-            fn visit_with<V: $crate::ty::visit::TypeVisitor<$tcx>>(
-                &self,
-                visitor: &mut V,
-            ) -> ::std::ops::ControlFlow<V::BreakTy> {
-                EnumTypeTraversalImpl!(@VisitVariants(self, visitor) input($($variants)*) output())
-            }
-        }
-    };
-
-    (@FoldVariants($this:expr, $folder:expr) input() output($($output:tt)*)) => {
-        Ok(match $this {
-            $($output)*
-        })
-    };
-
-    (@FoldVariants($this:expr, $folder:expr)
-     input( ($variant:path) ( $($variant_arg:ident),* ) , $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @FoldVariants($this, $folder)
-                input($($input)*)
-                output(
-                    $variant ( $($variant_arg),* ) => {
-                        $variant (
-                            $($crate::ty::fold::TypeFoldable::try_fold_with($variant_arg, $folder)?),*
-                        )
-                    }
-                    $($output)*
-                )
-        )
-    };
-
-    (@FoldVariants($this:expr, $folder:expr)
-     input( ($variant:path) { $($variant_arg:ident),* $(,)? } , $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @FoldVariants($this, $folder)
-                input($($input)*)
-                output(
-                    $variant { $($variant_arg),* } => {
-                        $variant {
-                            $($variant_arg: $crate::ty::fold::TypeFoldable::fold_with(
-                                $variant_arg, $folder
-                            )?),* }
-                    }
-                    $($output)*
-                )
-        )
-    };
-
-    (@FoldVariants($this:expr, $folder:expr)
-     input( ($variant:path), $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @FoldVariants($this, $folder)
-                input($($input)*)
-                output(
-                    $variant => { $variant }
-                    $($output)*
-                )
-        )
-    };
-
-    (@VisitVariants($this:expr, $visitor:expr) input() output($($output:tt)*)) => {
-        match $this {
-            $($output)*
-        }
-    };
-
-    (@VisitVariants($this:expr, $visitor:expr)
-     input( ($variant:path) ( $($variant_arg:ident),* ) , $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @VisitVariants($this, $visitor)
-                input($($input)*)
-                output(
-                    $variant ( $($variant_arg),* ) => {
-                        $($crate::ty::visit::TypeVisitable::visit_with(
-                            $variant_arg, $visitor
-                        )?;)*
-                        ::std::ops::ControlFlow::Continue(())
-                    }
-                    $($output)*
-                )
-        )
-    };
-
-    (@VisitVariants($this:expr, $visitor:expr)
-     input( ($variant:path) { $($variant_arg:ident),* $(,)? } , $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @VisitVariants($this, $visitor)
-                input($($input)*)
-                output(
-                    $variant { $($variant_arg),* } => {
-                        $($crate::ty::visit::TypeVisitable::visit_with(
-                            $variant_arg, $visitor
-                        )?;)*
-                        ::std::ops::ControlFlow::Continue(())
-                    }
-                    $($output)*
-                )
-        )
-    };
-
-    (@VisitVariants($this:expr, $visitor:expr)
-     input( ($variant:path), $($input:tt)*)
-     output( $($output:tt)*) ) => {
-        EnumTypeTraversalImpl!(
-            @VisitVariants($this, $visitor)
-                input($($input)*)
-                output(
-                    $variant => { ::std::ops::ControlFlow::Continue(()) }
-                    $($output)*
-                )
-        )
-    };
-}
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index bea884c85..c4601a1fb 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -91,7 +91,8 @@ bitflags! {
         /// the MIR `InstrumentCoverage` pass and not added to the coverage map
         /// during codegen.
         const NO_COVERAGE               = 1 << 15;
-        /// `#[used(linker)]`: indicates that LLVM nor the linker can eliminate this function.
+        /// `#[used(linker)]`:
+        /// indicates that neither LLVM nor the linker will eliminate this function.
         const USED_LINKER               = 1 << 16;
         /// `#[rustc_deallocator]`: a hint to LLVM that the function only deallocates memory.
         const DEALLOCATOR               = 1 << 17;
diff --git a/compiler/rustc_middle/src/middle/mod.rs b/compiler/rustc_middle/src/middle/mod.rs
index 8dc68b1f5..0b6774f1b 100644
--- a/compiler/rustc_middle/src/middle/mod.rs
+++ b/compiler/rustc_middle/src/middle/mod.rs
@@ -29,7 +29,7 @@ pub mod lib_features {
 pub mod limits;
 pub mod privacy;
 pub mod region;
-pub mod resolve_lifetime;
+pub mod resolve_bound_vars;
 pub mod stability;
 
 pub fn provide(providers: &mut crate::ty::query::Providers) {
diff --git a/compiler/rustc_middle/src/middle/privacy.rs b/compiler/rustc_middle/src/middle/privacy.rs
index 0e18ba73d..893bf54b8 100644
--- a/compiler/rustc_middle/src/middle/privacy.rs
+++ b/compiler/rustc_middle/src/middle/privacy.rs
@@ -194,11 +194,6 @@ impl EffectiveVisibilities {
     }
 }
 
-pub trait IntoDefIdTree {
-    type Tree: DefIdTree;
-    fn tree(self) -> Self::Tree;
-}
-
 impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
     pub fn iter(&self) -> impl Iterator<Item = (&Id, &EffectiveVisibility)> {
         self.map.iter()
@@ -217,25 +212,21 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
         self.map.entry(id).or_insert_with(|| EffectiveVisibility::from_vis(lazy_private_vis()))
     }
 
-    pub fn update<T: IntoDefIdTree>(
+    pub fn update(
         &mut self,
         id: Id,
         nominal_vis: Visibility,
-        lazy_private_vis: impl FnOnce(T) -> (Visibility, T),
+        lazy_private_vis: impl FnOnce() -> Visibility,
         inherited_effective_vis: EffectiveVisibility,
         level: Level,
-        mut into_tree: T,
+        tree: impl DefIdTree,
     ) -> bool {
         let mut changed = false;
-        let mut current_effective_vis = match self.map.get(&id).copied() {
-            Some(eff_vis) => eff_vis,
-            None => {
-                let private_vis;
-                (private_vis, into_tree) = lazy_private_vis(into_tree);
-                EffectiveVisibility::from_vis(private_vis)
-            }
-        };
-        let tree = into_tree.tree();
+        let mut current_effective_vis = self
+            .map
+            .get(&id)
+            .copied()
+            .unwrap_or_else(|| EffectiveVisibility::from_vis(lazy_private_vis()));
 
         let mut inherited_effective_vis_at_prev_level = *inherited_effective_vis.at_level(level);
         let mut calculated_effective_vis = inherited_effective_vis_at_prev_level;
diff --git a/compiler/rustc_middle/src/middle/resolve_lifetime.rs b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
index c3bf1c717..c59704fc0 100644
--- a/compiler/rustc_middle/src/middle/resolve_lifetime.rs
+++ b/compiler/rustc_middle/src/middle/resolve_bound_vars.rs
@@ -1,18 +1,20 @@
-//! Name resolution for lifetimes: type declarations.
+//! Name resolution for lifetimes and late-bound type and const variables: type declarations.
 
 use crate::ty;
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{ItemLocalId, OwnerId};
 use rustc_macros::HashStable;
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
-pub enum Region {
-    Static,
-    EarlyBound(/* lifetime decl */ DefId),
-    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* lifetime decl */ DefId),
+pub enum ResolvedArg {
+    StaticLifetime,
+    EarlyBound(/* decl */ DefId),
+    LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* decl */ DefId),
     Free(DefId, /* lifetime decl */ DefId),
+    Error(ErrorGuaranteed),
 }
 
 /// A set containing, at most, one known element.
@@ -46,10 +48,10 @@ pub enum ObjectLifetimeDefault {
 /// Maps the id of each lifetime reference to the lifetime decl
 /// that it corresponds to.
 #[derive(Default, HashStable, Debug)]
-pub struct ResolveLifetimes {
+pub struct ResolveBoundVars {
     /// Maps from every use of a named (not anonymous) lifetime to a
     /// `Region` describing how that region is bound
-    pub defs: FxHashMap<OwnerId, FxHashMap<ItemLocalId, Region>>,
+    pub defs: FxHashMap<OwnerId, FxHashMap<ItemLocalId, ResolvedArg>>,
 
     pub late_bound_vars: FxHashMap<OwnerId, FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>>,
 }
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 0836f236e..354c84e22 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -255,7 +255,7 @@ fn late_report_deprecation(
     let method_span = method_span.unwrap_or(span);
     tcx.struct_span_lint_hir(lint, hir_id, method_span, message, |diag| {
         if let hir::Node::Expr(_) = tcx.hir().get(hir_id) {
-            let kind = tcx.def_kind(def_id).descr(def_id);
+            let kind = tcx.def_descr(def_id);
             deprecation_suggestion(diag, kind, suggestion, method_span);
         }
         diag
@@ -392,7 +392,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     let lint = deprecation_lint(is_in_effect);
                     if self.lint_level_at_node(lint, id).0 != Level::Allow {
                         let def_path = with_no_trimmed_paths!(self.def_path_str(def_id));
-                        let def_kind = self.def_kind(def_id).descr(def_id);
+                        let def_kind = self.def_descr(def_id);
 
                         late_report_deprecation(
                             self,
diff --git a/compiler/rustc_middle/src/mir/basic_blocks.rs b/compiler/rustc_middle/src/mir/basic_blocks.rs
index 752cbdeae..b93871769 100644
--- a/compiler/rustc_middle/src/mir/basic_blocks.rs
+++ b/compiler/rustc_middle/src/mir/basic_blocks.rs
@@ -1,41 +1,46 @@
-use crate::mir::graph_cyclic_cache::GraphIsCyclicCache;
-use crate::mir::predecessors::{PredecessorCache, Predecessors};
-use crate::mir::switch_sources::{SwitchSourceCache, SwitchSources};
-use crate::mir::traversal::PostorderCache;
-use crate::mir::{BasicBlock, BasicBlockData, Successors, START_BLOCK};
+use crate::mir::traversal::Postorder;
+use crate::mir::{BasicBlock, BasicBlockData, Successors, Terminator, TerminatorKind, START_BLOCK};
 
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::graph;
 use rustc_data_structures::graph::dominators::{dominators, Dominators};
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::sync::OnceCell;
 use rustc_index::vec::IndexVec;
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
+use smallvec::SmallVec;
 
 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct BasicBlocks<'tcx> {
     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
-    predecessor_cache: PredecessorCache,
-    switch_source_cache: SwitchSourceCache,
-    is_cyclic: GraphIsCyclicCache,
-    postorder_cache: PostorderCache,
+    cache: Cache,
+}
+
+// Typically 95%+ of basic blocks have 4 or fewer predecessors.
+pub type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>;
+
+pub type SwitchSources = FxHashMap<(BasicBlock, BasicBlock), SmallVec<[Option<u128>; 1]>>;
+
+#[derive(Clone, Default, Debug)]
+struct Cache {
+    predecessors: OnceCell<Predecessors>,
+    switch_sources: OnceCell<SwitchSources>,
+    is_cyclic: OnceCell<bool>,
+    postorder: OnceCell<Vec<BasicBlock>>,
 }
 
 impl<'tcx> BasicBlocks<'tcx> {
     #[inline]
     pub fn new(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
-        BasicBlocks {
-            basic_blocks,
-            predecessor_cache: PredecessorCache::new(),
-            switch_source_cache: SwitchSourceCache::new(),
-            is_cyclic: GraphIsCyclicCache::new(),
-            postorder_cache: PostorderCache::new(),
-        }
+        BasicBlocks { basic_blocks, cache: Cache::default() }
     }
 
     /// Returns true if control-flow graph contains a cycle reachable from the `START_BLOCK`.
     #[inline]
     pub fn is_cfg_cyclic(&self) -> bool {
-        self.is_cyclic.is_cyclic(self)
+        *self.cache.is_cyclic.get_or_init(|| graph::is_cyclic(self))
     }
 
-    #[inline]
     pub fn dominators(&self) -> Dominators<BasicBlock> {
         dominators(&self)
     }
@@ -43,20 +48,46 @@ impl<'tcx> BasicBlocks<'tcx> {
     /// Returns predecessors for each basic block.
     #[inline]
     pub fn predecessors(&self) -> &Predecessors {
-        self.predecessor_cache.compute(&self.basic_blocks)
+        self.cache.predecessors.get_or_init(|| {
+            let mut preds = IndexVec::from_elem(SmallVec::new(), &self.basic_blocks);
+            for (bb, data) in self.basic_blocks.iter_enumerated() {
+                if let Some(term) = &data.terminator {
+                    for succ in term.successors() {
+                        preds[succ].push(bb);
+                    }
+                }
+            }
+            preds
+        })
     }
 
     /// Returns basic blocks in a postorder.
     #[inline]
     pub fn postorder(&self) -> &[BasicBlock] {
-        self.postorder_cache.compute(&self.basic_blocks)
+        self.cache.postorder.get_or_init(|| {
+            Postorder::new(&self.basic_blocks, START_BLOCK).map(|(bb, _)| bb).collect()
+        })
     }
 
     /// `switch_sources()[&(target, switch)]` returns a list of switch
     /// values that lead to a `target` block from a `switch` block.
     #[inline]
     pub fn switch_sources(&self) -> &SwitchSources {
-        self.switch_source_cache.compute(&self.basic_blocks)
+        self.cache.switch_sources.get_or_init(|| {
+            let mut switch_sources: SwitchSources = FxHashMap::default();
+            for (bb, data) in self.basic_blocks.iter_enumerated() {
+                if let Some(Terminator {
+                    kind: TerminatorKind::SwitchInt { targets, .. }, ..
+                }) = &data.terminator
+                {
+                    for (value, target) in targets.iter() {
+                        switch_sources.entry((target, bb)).or_default().push(Some(value));
+                    }
+                    switch_sources.entry((targets.otherwise(), bb)).or_default().push(None);
+                }
+            }
+            switch_sources
+        })
     }
 
     /// Returns mutable reference to basic blocks. Invalidates CFG cache.
@@ -88,10 +119,7 @@ impl<'tcx> BasicBlocks<'tcx> {
     /// All other methods that allow you to mutate the basic blocks also call this method
     /// themselves, thereby avoiding any risk of accidentally cache invalidation.
     pub fn invalidate_cfg_cache(&mut self) {
-        self.predecessor_cache.invalidate();
-        self.switch_source_cache.invalidate();
-        self.is_cyclic.invalidate();
-        self.postorder_cache.invalidate();
+        self.cache = Cache::default();
     }
 }
 
@@ -145,3 +173,24 @@ impl<'tcx> graph::WithPredecessors for BasicBlocks<'tcx> {
         self.predecessors()[node].iter().copied()
     }
 }
+
+TrivialTypeTraversalAndLiftImpls! {
+    Cache,
+}
+
+impl<S: Encoder> Encodable<S> for Cache {
+    #[inline]
+    fn encode(&self, _s: &mut S) {}
+}
+
+impl<D: Decoder> Decodable<D> for Cache {
+    #[inline]
+    fn decode(_: &mut D) -> Self {
+        Default::default()
+    }
+}
+
+impl<CTX> HashStable<CTX> for Cache {
+    #[inline]
+    fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {}
+}
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index e7bb3ab0b..db24dae11 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/compiler/rustc_middle/src/mir/coverage.rs
@@ -135,7 +135,10 @@ impl Debug for CoverageKind {
                 "Expression({:?}) = {} {} {}",
                 id.index(),
                 lhs.index(),
-                if *op == Op::Add { "+" } else { "-" },
+                match op {
+                    Op::Add => "+",
+                    Op::Subtract => "-",
+                },
                 rhs.index(),
             ),
             Unreachable => write!(fmt, "Unreachable"),
diff --git a/compiler/rustc_middle/src/mir/graph_cyclic_cache.rs b/compiler/rustc_middle/src/mir/graph_cyclic_cache.rs
deleted file mode 100644
index f97bf2883..000000000
--- a/compiler/rustc_middle/src/mir/graph_cyclic_cache.rs
+++ /dev/null
@@ -1,63 +0,0 @@
-use rustc_data_structures::graph::{
-    self, DirectedGraph, WithNumNodes, WithStartNode, WithSuccessors,
-};
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_data_structures::sync::OnceCell;
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
-
-/// Helper type to cache the result of `graph::is_cyclic`.
-#[derive(Clone, Debug)]
-pub(super) struct GraphIsCyclicCache {
-    cache: OnceCell<bool>,
-}
-
-impl GraphIsCyclicCache {
-    #[inline]
-    pub(super) fn new() -> Self {
-        GraphIsCyclicCache { cache: OnceCell::new() }
-    }
-
-    pub(super) fn is_cyclic<G>(&self, graph: &G) -> bool
-    where
-        G: ?Sized + DirectedGraph + WithStartNode + WithSuccessors + WithNumNodes,
-    {
-        *self.cache.get_or_init(|| graph::is_cyclic(graph))
-    }
-
-    /// Invalidates the cache.
-    #[inline]
-    pub(super) fn invalidate(&mut self) {
-        // Invalidating the cache requires mutating the MIR, which in turn requires a unique
-        // reference (`&mut`) to the `mir::Body`. Because of this, we can assume that all
-        // callers of `invalidate` have a unique reference to the MIR and thus to the
-        // cache. This means we never need to do synchronization when `invalidate` is called,
-        // we can simply reinitialize the `OnceCell`.
-        self.cache = OnceCell::new();
-    }
-}
-
-impl<S: Encoder> Encodable<S> for GraphIsCyclicCache {
-    #[inline]
-    fn encode(&self, s: &mut S) {
-        Encodable::encode(&(), s);
-    }
-}
-
-impl<D: Decoder> Decodable<D> for GraphIsCyclicCache {
-    #[inline]
-    fn decode(d: &mut D) -> Self {
-        let () = Decodable::decode(d);
-        Self::new()
-    }
-}
-
-impl<CTX> HashStable<CTX> for GraphIsCyclicCache {
-    #[inline]
-    fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
-        // do nothing
-    }
-}
-
-TrivialTypeTraversalAndLiftImpls! {
-    GraphIsCyclicCache,
-}
diff --git a/compiler/rustc_middle/src/mir/graphviz.rs b/compiler/rustc_middle/src/mir/graphviz.rs
index 5de56dad0..cf6d46e1e 100644
--- a/compiler/rustc_middle/src/mir/graphviz.rs
+++ b/compiler/rustc_middle/src/mir/graphviz.rs
@@ -110,7 +110,7 @@ fn write_graph_label<'tcx, W: std::fmt::Write>(
         let decl = &body.local_decls[local];
 
         write!(w, "let ")?;
-        if decl.mutability == Mutability::Mut {
+        if decl.mutability.is_mut() {
             write!(w, "mut ")?;
         }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 221105ac4..48375ed30 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -8,7 +8,8 @@ mod tests;
 use std::borrow::Cow;
 use std::fmt;
 use std::hash;
-use std::ops::Range;
+use std::hash::Hash;
+use std::ops::{Deref, DerefMut, Range};
 use std::ptr;
 
 use either::{Left, Right};
@@ -29,6 +30,39 @@ use provenance_map::*;
 
 pub use init_mask::{InitChunk, InitChunkIter};
 
+/// Functionality required for the bytes of an `Allocation`.
+pub trait AllocBytes:
+    Clone + fmt::Debug + Eq + PartialEq + Hash + Deref<Target = [u8]> + DerefMut<Target = [u8]>
+{
+    /// Adjust the bytes to the specified alignment -- by default, this is a no-op.
+    fn adjust_to_align(self, _align: Align) -> Self;
+
+    /// Create an `AllocBytes` from a slice of `u8`.
+    fn from_bytes<'a>(slice: impl Into<Cow<'a, [u8]>>, _align: Align) -> Self;
+
+    /// Create a zeroed `AllocBytes` of the specified size and alignment;
+    /// call the callback error handler if there is an error in allocating the memory.
+    fn zeroed(size: Size, _align: Align) -> Option<Self>;
+}
+
+// Default `bytes` for `Allocation` is a `Box<[u8]>`.
+impl AllocBytes for Box<[u8]> {
+    fn adjust_to_align(self, _align: Align) -> Self {
+        self
+    }
+
+    fn from_bytes<'a>(slice: impl Into<Cow<'a, [u8]>>, _align: Align) -> Self {
+        Box::<[u8]>::from(slice.into())
+    }
+
+    fn zeroed(size: Size, _align: Align) -> Option<Self> {
+        let bytes = Box::<[u8]>::try_new_zeroed_slice(size.bytes_usize()).ok()?;
+        // SAFETY: the box was zero-allocated, which is a valid initial value for Box<[u8]>
+        let bytes = unsafe { bytes.assume_init() };
+        Some(bytes)
+    }
+}
+
 /// This type represents an Allocation in the Miri/CTFE core engine.
 ///
 /// Its public API is rather low-level, working directly with allocation offsets and a custom error
@@ -38,10 +72,10 @@ pub use init_mask::{InitChunk, InitChunkIter};
 // hashed. (see the `Hash` impl below for more details), so the impl is not derived.
 #[derive(Clone, Eq, PartialEq, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
-pub struct Allocation<Prov: Provenance = AllocId, Extra = ()> {
+pub struct Allocation<Prov: Provenance = AllocId, Extra = (), Bytes = Box<[u8]>> {
     /// The actual bytes of the allocation.
     /// Note that the bytes of a pointer represent the offset of the pointer.
-    bytes: Box<[u8]>,
+    bytes: Bytes,
     /// Maps from byte addresses to extra provenance data for each pointer.
     /// Only the first byte of a pointer is inserted into the map; i.e.,
     /// every entry in this map applies to `pointer_size` consecutive bytes starting
@@ -220,14 +254,27 @@ impl AllocRange {
 }
 
 // The constructors are all without extra; the extra gets added by a machine hook later.
-impl<Prov: Provenance> Allocation<Prov> {
+impl<Prov: Provenance, Bytes: AllocBytes> Allocation<Prov, (), Bytes> {
+    /// Creates an allocation from an existing `Bytes` value - this is needed for miri FFI support
+    pub fn from_raw_bytes(bytes: Bytes, align: Align, mutability: Mutability) -> Self {
+        let size = Size::from_bytes(bytes.len());
+        Self {
+            bytes,
+            provenance: ProvenanceMap::new(),
+            init_mask: InitMask::new(size, true),
+            align,
+            mutability,
+            extra: (),
+        }
+    }
+
     /// Creates an allocation initialized by the given bytes
     pub fn from_bytes<'a>(
         slice: impl Into<Cow<'a, [u8]>>,
         align: Align,
         mutability: Mutability,
     ) -> Self {
-        let bytes = Box::<[u8]>::from(slice.into());
+        let bytes = Bytes::from_bytes(slice, align);
         let size = Size::from_bytes(bytes.len());
         Self {
             bytes,
@@ -248,7 +295,7 @@ impl<Prov: Provenance> Allocation<Prov> {
     ///
     /// If `panic_on_fail` is true, this will never return `Err`.
     pub fn uninit<'tcx>(size: Size, align: Align, panic_on_fail: bool) -> InterpResult<'tcx, Self> {
-        let bytes = Box::<[u8]>::try_new_zeroed_slice(size.bytes_usize()).map_err(|_| {
+        let bytes = Bytes::zeroed(size, align).ok_or_else(|| {
             // This results in an error that can happen non-deterministically, since the memory
             // available to the compiler can change between runs. Normally queries are always
             // deterministic. However, we can be non-deterministic here because all uses of const
@@ -262,8 +309,7 @@ impl<Prov: Provenance> Allocation<Prov> {
             });
             InterpError::ResourceExhaustion(ResourceExhaustionInfo::MemoryExhausted)
         })?;
-        // SAFETY: the box was zero-allocated, which is a valid initial value for Box<[u8]>
-        let bytes = unsafe { bytes.assume_init() };
+
         Ok(Allocation {
             bytes,
             provenance: ProvenanceMap::new(),
@@ -275,7 +321,7 @@ impl<Prov: Provenance> Allocation<Prov> {
     }
 }
 
-impl Allocation {
+impl<Bytes: AllocBytes> Allocation<AllocId, (), Bytes> {
     /// Adjust allocation from the ones in tcx to a custom Machine instance
     /// with a different Provenance and Extra type.
     pub fn adjust_from_tcx<Prov: Provenance, Extra, Err>(
@@ -283,9 +329,11 @@ impl Allocation {
         cx: &impl HasDataLayout,
         extra: Extra,
         mut adjust_ptr: impl FnMut(Pointer<AllocId>) -> Result<Pointer<Prov>, Err>,
-    ) -> Result<Allocation<Prov, Extra>, Err> {
-        // Compute new pointer provenance, which also adjusts the bytes.
-        let mut bytes = self.bytes;
+    ) -> Result<Allocation<Prov, Extra, Bytes>, Err> {
+        // Compute new pointer provenance, which also adjusts the bytes, and realign the pointer if
+        // necessary.
+        let mut bytes = self.bytes.adjust_to_align(self.align);
+
         let mut new_provenance = Vec::with_capacity(self.provenance.ptrs().len());
         let ptr_size = cx.data_layout().pointer_size.bytes_usize();
         let endian = cx.data_layout().endian;
@@ -311,7 +359,7 @@ impl Allocation {
 }
 
 /// Raw accessors. Provide access to otherwise private bytes.
-impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
+impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes> {
     pub fn len(&self) -> usize {
         self.bytes.len()
     }
@@ -340,7 +388,11 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
 }
 
 /// Byte accessors.
-impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
+impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes> {
+    pub fn base_addr(&self) -> *const u8 {
+        self.bytes.as_ptr()
+    }
+
     /// This is the entirely abstraction-violating way to just grab the raw bytes without
     /// caring about provenance or initialization.
     ///
@@ -412,7 +464,7 @@ impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
 }
 
 /// Reading and writing.
-impl<Prov: Provenance, Extra> Allocation<Prov, Extra> {
+impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes> {
     /// Sets the init bit for the given range.
     fn mark_init(&mut self, range: AllocRange, is_init: bool) {
         if range.size.bytes() == 0 {
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index bd9cd53e1..c5137cf06 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -323,7 +323,7 @@ impl fmt::Display for UndefinedBehaviorInfo {
                 write!(
                     f,
                     "{msg}{pointer} is a dangling pointer (it has no provenance)",
-                    pointer = Pointer::<Option<AllocId>>::from_addr(*i),
+                    pointer = Pointer::<Option<AllocId>>::from_addr_invalid(*i),
                 )
             }
             AlignmentCheckFailed { required, has } => write!(
@@ -430,8 +430,10 @@ pub enum ResourceExhaustionInfo {
     ///
     /// The exact limit is set by the `const_eval_limit` attribute.
     StepLimitReached,
-    /// There is not enough memory to perform an allocation.
+    /// There is not enough memory (on the host) to perform an allocation.
     MemoryExhausted,
+    /// The address space (of the target) is full.
+    AddressSpaceFull,
 }
 
 impl fmt::Display for ResourceExhaustionInfo {
@@ -447,6 +449,9 @@ impl fmt::Display for ResourceExhaustionInfo {
             MemoryExhausted => {
                 write!(f, "tried to allocate more memory than available to compiler")
             }
+            AddressSpaceFull => {
+                write!(f, "there are no more free addresses in the address space")
+            }
         }
     }
 }
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index 5f425a287..1766d7a66 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -110,7 +110,7 @@ use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_serialize::{Decodable, Encodable};
-use rustc_target::abi::Endian;
+use rustc_target::abi::{AddressSpace, Endian, HasDataLayout};
 
 use crate::mir;
 use crate::ty::codec::{TyDecoder, TyEncoder};
@@ -127,8 +127,8 @@ pub use self::error::{
 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar};
 
 pub use self::allocation::{
-    alloc_range, AllocError, AllocRange, AllocResult, Allocation, ConstAllocation, InitChunk,
-    InitChunkIter,
+    alloc_range, AllocBytes, AllocError, AllocRange, AllocResult, Allocation, ConstAllocation,
+    InitChunk, InitChunkIter,
 };
 
 pub use self::pointer::{Pointer, PointerArithmetic, Provenance};
@@ -438,6 +438,17 @@ impl<'tcx> GlobalAlloc<'tcx> {
             _ => bug!("expected vtable, got {:?}", self),
         }
     }
+
+    /// The address space that this `GlobalAlloc` should be placed in.
+    #[inline]
+    pub fn address_space(&self, cx: &impl HasDataLayout) -> AddressSpace {
+        match self {
+            GlobalAlloc::Function(..) => cx.data_layout().instruction_address_space,
+            GlobalAlloc::Static(..) | GlobalAlloc::Memory(..) | GlobalAlloc::VTable(..) => {
+                AddressSpace::DATA
+            }
+        }
+    }
 }
 
 pub(crate) struct AllocMap<'tcx> {
diff --git a/compiler/rustc_middle/src/mir/interpret/pointer.rs b/compiler/rustc_middle/src/mir/interpret/pointer.rs
index b08309910..60927eed8 100644
--- a/compiler/rustc_middle/src/mir/interpret/pointer.rs
+++ b/compiler/rustc_middle/src/mir/interpret/pointer.rs
@@ -19,29 +19,29 @@ pub trait PointerArithmetic: HasDataLayout {
 
     #[inline(always)]
     fn max_size_of_val(&self) -> Size {
-        Size::from_bytes(self.machine_isize_max())
+        Size::from_bytes(self.target_isize_max())
     }
 
     #[inline]
-    fn machine_usize_max(&self) -> u64 {
+    fn target_usize_max(&self) -> u64 {
         self.pointer_size().unsigned_int_max().try_into().unwrap()
     }
 
     #[inline]
-    fn machine_isize_min(&self) -> i64 {
+    fn target_isize_min(&self) -> i64 {
         self.pointer_size().signed_int_min().try_into().unwrap()
     }
 
     #[inline]
-    fn machine_isize_max(&self) -> i64 {
+    fn target_isize_max(&self) -> i64 {
         self.pointer_size().signed_int_max().try_into().unwrap()
     }
 
     #[inline]
-    fn machine_usize_to_isize(&self, val: u64) -> i64 {
+    fn target_usize_to_isize(&self, val: u64) -> i64 {
         let val = val as i64;
         // Now wrap-around into the machine_isize range.
-        if val > self.machine_isize_max() {
+        if val > self.target_isize_max() {
             // This can only happen if the ptr size is < 64, so we know max_usize_plus_1 fits into
             // i64.
             debug_assert!(self.pointer_size().bits() < 64);
@@ -76,11 +76,11 @@ pub trait PointerArithmetic: HasDataLayout {
         let n = i.unsigned_abs();
         if i >= 0 {
             let (val, over) = self.overflowing_offset(val, n);
-            (val, over || i > self.machine_isize_max())
+            (val, over || i > self.target_isize_max())
         } else {
             let res = val.overflowing_sub(n);
             let (val, over) = self.truncate_to_ptr(res);
-            (val, over || i < self.machine_isize_min())
+            (val, over || i < self.target_isize_min())
         }
     }
 
@@ -251,14 +251,16 @@ impl<Prov> Pointer<Option<Prov>> {
 }
 
 impl<Prov> Pointer<Option<Prov>> {
+    /// Creates a pointer to the given address, with invalid provenance (i.e., cannot be used for
+    /// any memory access).
     #[inline(always)]
-    pub fn from_addr(addr: u64) -> Self {
+    pub fn from_addr_invalid(addr: u64) -> Self {
         Pointer { provenance: None, offset: Size::from_bytes(addr) }
     }
 
     #[inline(always)]
     pub fn null() -> Self {
-        Pointer::from_addr(0)
+        Pointer::from_addr_invalid(0)
     }
 }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index b6c6e9d55..856d821a5 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -2,7 +2,7 @@ use super::{ErrorHandled, EvalToConstValueResult, EvalToValTreeResult, GlobalId}
 
 use crate::mir;
 use crate::ty::subst::InternalSubsts;
-use crate::ty::visit::TypeVisitable;
+use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{self, query::TyCtxtAt, query::TyCtxtEnsure, TyCtxt};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
diff --git a/compiler/rustc_middle/src/mir/interpret/value.rs b/compiler/rustc_middle/src/mir/interpret/value.rs
index 88fb14eb3..36dbbe4bf 100644
--- a/compiler/rustc_middle/src/mir/interpret/value.rs
+++ b/compiler/rustc_middle/src/mir/interpret/value.rs
@@ -75,8 +75,8 @@ impl<'tcx> ConstValue<'tcx> {
         self.try_to_scalar_int()?.try_into().ok()
     }
 
-    pub fn try_to_machine_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
-        self.try_to_scalar_int()?.try_to_machine_usize(tcx).ok()
+    pub fn try_to_target_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
+        self.try_to_scalar_int()?.try_to_target_usize(tcx).ok()
     }
 
     pub fn try_to_bits_for_ty(
@@ -97,8 +97,8 @@ impl<'tcx> ConstValue<'tcx> {
         ConstValue::Scalar(Scalar::from_u64(i))
     }
 
-    pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
-        ConstValue::Scalar(Scalar::from_machine_usize(i, cx))
+    pub fn from_target_usize(i: u64, cx: &impl HasDataLayout) -> Self {
+        ConstValue::Scalar(Scalar::from_target_usize(i, cx))
     }
 }
 
@@ -241,7 +241,7 @@ impl<Prov> Scalar<Prov> {
     }
 
     #[inline]
-    pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
+    pub fn from_target_usize(i: u64, cx: &impl HasDataLayout) -> Self {
         Self::from_uint(i, cx.data_layout().pointer_size)
     }
 
@@ -268,7 +268,7 @@ impl<Prov> Scalar<Prov> {
     }
 
     #[inline]
-    pub fn from_machine_isize(i: i64, cx: &impl HasDataLayout) -> Self {
+    pub fn from_target_isize(i: i64, cx: &impl HasDataLayout) -> Self {
         Self::from_int(i, cx.data_layout().pointer_size)
     }
 
@@ -322,7 +322,7 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
             Right(ptr) => Ok(ptr.into()),
             Left(bits) => {
                 let addr = u64::try_from(bits).unwrap();
-                Ok(Pointer::from_addr(addr))
+                Ok(Pointer::from_addr_invalid(addr))
             }
         }
     }
@@ -429,7 +429,7 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
 
     /// Converts the scalar to produce a machine-pointer-sized unsigned integer.
     /// Fails if the scalar is a pointer.
-    pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
+    pub fn to_target_usize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
         let b = self.to_uint(cx.data_layout().pointer_size)?;
         Ok(u64::try_from(b).unwrap())
     }
@@ -469,7 +469,7 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
 
     /// Converts the scalar to produce a machine-pointer-sized signed integer.
     /// Fails if the scalar is a pointer.
-    pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, i64> {
+    pub fn to_target_isize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, i64> {
         let b = self.to_int(cx.data_layout().pointer_size)?;
         Ok(i64::try_from(b).unwrap())
     }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index e52b243ec..99cdb769d 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -9,7 +9,7 @@ use crate::mir::visit::MirVisitable;
 use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::ty::print::{FmtPrinter, Printer};
-use crate::ty::visit::{TypeVisitable, TypeVisitor};
+use crate::ty::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor};
 use crate::ty::{self, DefIdTree, List, Ty, TyCtxt};
 use crate::ty::{AdtDef, InstanceDef, ScalarInt, UserTypeAnnotationIndex};
 use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
@@ -27,7 +27,6 @@ use polonius_engine::Atom;
 pub use rustc_ast::Mutability;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::graph::dominators::Dominators;
-use rustc_index::bit_set::BitMatrix;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::symbol::Symbol;
@@ -47,25 +46,21 @@ mod basic_blocks;
 pub mod coverage;
 mod generic_graph;
 pub mod generic_graphviz;
-mod graph_cyclic_cache;
 pub mod graphviz;
 pub mod interpret;
 pub mod mono;
 pub mod patch;
-mod predecessors;
 pub mod pretty;
 mod query;
 pub mod spanview;
 mod syntax;
 pub use syntax::*;
-mod switch_sources;
 pub mod tcx;
 pub mod terminator;
 pub use terminator::*;
 
 pub mod traversal;
 mod type_foldable;
-mod type_visitable;
 pub mod visit;
 
 pub use self::generic_graph::graphviz_safe_def_name;
@@ -419,11 +414,7 @@ impl<'tcx> Body<'tcx> {
         (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
             let local = Local::new(index);
             let decl = &self.local_decls[local];
-            if decl.is_user_variable() && decl.mutability == Mutability::Mut {
-                Some(local)
-            } else {
-                None
-            }
+            (decl.is_user_variable() && decl.mutability.is_mut()).then_some(local)
         })
     }
 
@@ -712,7 +703,11 @@ pub enum BindingForm<'tcx> {
     RefForGuard,
 }
 
-TrivialTypeTraversalAndLiftImpls! { BindingForm<'tcx>, }
+TrivialTypeTraversalAndLiftImpls! {
+    for<'tcx> {
+        BindingForm<'tcx>,
+    }
+}
 
 mod binding_form_impl {
     use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -905,6 +900,8 @@ pub enum LocalInfo<'tcx> {
     AggregateTemp,
     /// A temporary created during the pass `Derefer` to avoid it's retagging
     DerefTemp,
+    /// A temporary created for borrow checking.
+    FakeBorrow,
 }
 
 impl<'tcx> LocalDecl<'tcx> {
@@ -1464,6 +1461,7 @@ impl Debug for Statement<'_> {
             }
             Coverage(box ref coverage) => write!(fmt, "Coverage::{:?}", coverage.kind),
             Intrinsic(box ref intrinsic) => write!(fmt, "{intrinsic}"),
+            ConstEvalCounter => write!(fmt, "ConstEvalCounter"),
             Nop => write!(fmt, "nop"),
         }
     }
@@ -1622,7 +1620,7 @@ impl<'tcx> Place<'tcx> {
             &v
         };
 
-        Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
+        Place { local: self.local, projection: tcx.mk_place_elems(new_projections) }
     }
 }
 
@@ -1644,6 +1642,14 @@ impl<'tcx> PlaceRef<'tcx> {
         }
     }
 
+    /// Returns `true` if this `Place` contains a `Deref` projection.
+    ///
+    /// If `Place::is_indirect` returns false, the caller knows that the `Place` refers to the
+    /// same region of memory as its base.
+    pub fn is_indirect(&self) -> bool {
+        self.projection.iter().any(|elem| elem.is_indirect())
+    }
+
     /// If MirPhase >= Derefered and if projection contains Deref,
     /// It's guaranteed to be in the first place
     pub fn has_deref(&self) -> bool {
@@ -2102,10 +2108,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
                         let name = if tcx.sess.opts.unstable_opts.span_free_formats {
                             let substs = tcx.lift(substs).unwrap();
-                            format!(
-                                "[closure@{}]",
-                                tcx.def_path_str_with_substs(def_id.to_def_id(), substs),
-                            )
+                            format!("[closure@{}]", tcx.def_path_str_with_substs(def_id, substs),)
                         } else {
                             let span = tcx.def_span(def_id);
                             format!(
@@ -2116,11 +2119,17 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         let mut struct_fmt = fmt.debug_struct(&name);
 
                         // FIXME(project-rfc-2229#48): This should be a list of capture names/places
-                        if let Some(upvars) = tcx.upvars_mentioned(def_id) {
+                        if let Some(def_id) = def_id.as_local()
+                            && let Some(upvars) = tcx.upvars_mentioned(def_id)
+                        {
                             for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                 let var_name = tcx.hir().name(var_id);
                                 struct_fmt.field(var_name.as_str(), place);
                             }
+                        } else {
+                            for (index, place) in places.iter().enumerate() {
+                                struct_fmt.field(&format!("{index}"), place);
+                            }
                         }
 
                         struct_fmt.finish()
@@ -2131,11 +2140,17 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         let mut struct_fmt = fmt.debug_struct(&name);
 
                         // FIXME(project-rfc-2229#48): This should be a list of capture names/places
-                        if let Some(upvars) = tcx.upvars_mentioned(def_id) {
+                        if let Some(def_id) = def_id.as_local()
+                            && let Some(upvars) = tcx.upvars_mentioned(def_id)
+                        {
                             for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                 let var_name = tcx.hir().name(var_id);
                                 struct_fmt.field(var_name.as_str(), place);
                             }
+                        } else {
+                            for (index, place) in places.iter().enumerate() {
+                                struct_fmt.field(&format!("{index}"), place);
+                            }
                         }
 
                         struct_fmt.finish()
@@ -2335,13 +2350,17 @@ impl<'tcx> ConstantKind<'tcx> {
     }
 
     #[inline]
-    pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<u64> {
+    pub fn try_eval_target_usize(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> Option<u64> {
         match self {
-            Self::Ty(ct) => ct.try_eval_usize(tcx, param_env),
-            Self::Val(val, _) => val.try_to_machine_usize(tcx),
+            Self::Ty(ct) => ct.try_eval_target_usize(tcx, param_env),
+            Self::Val(val, _) => val.try_to_target_usize(tcx),
             Self::Unevaluated(uneval, _) => {
                 match tcx.const_eval_resolve(param_env, *uneval, None) {
-                    Ok(val) => val.try_to_machine_usize(tcx),
+                    Ok(val) => val.try_to_target_usize(tcx),
                     Err(_) => None,
                 }
             }
@@ -2478,7 +2497,7 @@ impl<'tcx> ConstantKind<'tcx> {
         };
         debug!("expr.kind: {:?}", expr.kind);
 
-        let ty = tcx.type_of(def.def_id_for_type_of());
+        let ty = tcx.type_of(def.def_id_for_type_of()).subst_identity();
         debug!(?ty);
 
         // FIXME(const_generics): We currently have to special case parameters because `min_const_generics`
@@ -2506,20 +2525,19 @@ impl<'tcx> ConstantKind<'tcx> {
         }
 
         let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
-        let parent_substs = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id) {
-            if let Some(parent_did) = tcx.hir().opt_local_def_id(parent_hir_id) {
-                InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
-            } else {
-                tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
-            }
+        let parent_substs = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id)
+            && let Some(parent_did) = parent_hir_id.as_owner()
+        {
+            InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
         } else {
-            tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
+            List::empty()
         };
         debug!(?parent_substs);
 
         let did = def.did.to_def_id();
         let child_substs = InternalSubsts::identity_for_item(tcx, did);
-        let substs = tcx.mk_substs(parent_substs.into_iter().chain(child_substs.into_iter()));
+        let substs =
+            tcx.mk_substs_from_iter(parent_substs.into_iter().chain(child_substs.into_iter()));
         debug!(?substs);
 
         let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
@@ -2737,8 +2755,11 @@ impl UserTypeProjection {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for UserTypeProjection {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(UserTypeProjection {
             base: self.base.try_fold_with(folder)?,
             projs: self.projs.try_fold_with(folder)?,
@@ -2746,8 +2767,11 @@ impl<'tcx> TypeFoldable<'tcx> for UserTypeProjection {
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for UserTypeProjection {
-    fn visit_with<Vs: TypeVisitor<'tcx>>(&self, visitor: &mut Vs) -> ControlFlow<Vs::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for UserTypeProjection {
+    fn visit_with<Vs: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut Vs,
+    ) -> ControlFlow<Vs::BreakTy> {
         self.base.visit_with(visitor)
         // Note: there's nothing in `self.proj` to visit.
     }
@@ -2884,7 +2908,7 @@ fn pretty_print_const_value<'tcx>(
             // the `destructure_const` query with an empty `ty::ParamEnv` without
             // introducing ICEs (e.g. via `layout_of`) from missing bounds.
             // E.g. `transmute([0usize; 2]): (u8, *mut T)` needs to know `T: Sized`
-            // to be able to destructure the tuple into `(0u8, *mut T)
+            // to be able to destructure the tuple into `(0u8, *mut T)`
             //
             // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
             // correct `ty::ParamEnv` to allow printing *all* constant values.
@@ -3049,7 +3073,7 @@ impl Location {
         if self.block == other.block {
             self.statement_index <= other.statement_index
         } else {
-            dominators.is_dominated_by(other.block, self.block)
+            dominators.dominates(self.block, other.block)
         }
     }
 }
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 1e8d5f7ea..7a05ee2ff 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -318,16 +318,19 @@ impl<'tcx> CodegenUnit<'tcx> {
         base_n::encode(hash, base_n::CASE_INSENSITIVE)
     }
 
-    pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
+    pub fn create_size_estimate(&mut self, tcx: TyCtxt<'tcx>) {
         // Estimate the size of a codegen unit as (approximately) the number of MIR
         // statements it corresponds to.
         self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
     }
 
     #[inline]
+    /// Should only be called if [`create_size_estimate`] has previously been called.
+    ///
+    /// [`create_size_estimate`]: Self::create_size_estimate
     pub fn size_estimate(&self) -> usize {
-        // Should only be called if `estimate_size` has previously been called.
-        self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
+        self.size_estimate
+            .expect("create_size_estimate must be called before getting a size_estimate")
     }
 
     pub fn modify_size_estimate(&mut self, delta: usize) {
diff --git a/compiler/rustc_middle/src/mir/predecessors.rs b/compiler/rustc_middle/src/mir/predecessors.rs
deleted file mode 100644
index 5f1fadaf3..000000000
--- a/compiler/rustc_middle/src/mir/predecessors.rs
+++ /dev/null
@@ -1,78 +0,0 @@
-//! Lazily compute the reverse control-flow graph for the MIR.
-
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_data_structures::sync::OnceCell;
-use rustc_index::vec::IndexVec;
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
-use smallvec::SmallVec;
-
-use crate::mir::{BasicBlock, BasicBlockData};
-
-// Typically 95%+ of basic blocks have 4 or fewer predecessors.
-pub type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>;
-
-#[derive(Clone, Debug)]
-pub(super) struct PredecessorCache {
-    cache: OnceCell<Predecessors>,
-}
-
-impl PredecessorCache {
-    #[inline]
-    pub(super) fn new() -> Self {
-        PredecessorCache { cache: OnceCell::new() }
-    }
-
-    /// Invalidates the predecessor cache.
-    #[inline]
-    pub(super) fn invalidate(&mut self) {
-        // Invalidating the predecessor cache requires mutating the MIR, which in turn requires a
-        // unique reference (`&mut`) to the `mir::Body`. Because of this, we can assume that all
-        // callers of `invalidate` have a unique reference to the MIR and thus to the predecessor
-        // cache. This means we never need to do synchronization when `invalidate` is called, we can
-        // simply reinitialize the `OnceCell`.
-        self.cache = OnceCell::new();
-    }
-
-    /// Returns the predecessor graph for this MIR.
-    #[inline]
-    pub(super) fn compute(
-        &self,
-        basic_blocks: &IndexVec<BasicBlock, BasicBlockData<'_>>,
-    ) -> &Predecessors {
-        self.cache.get_or_init(|| {
-            let mut preds = IndexVec::from_elem(SmallVec::new(), basic_blocks);
-            for (bb, data) in basic_blocks.iter_enumerated() {
-                if let Some(term) = &data.terminator {
-                    for succ in term.successors() {
-                        preds[succ].push(bb);
-                    }
-                }
-            }
-
-            preds
-        })
-    }
-}
-
-impl<S: Encoder> Encodable<S> for PredecessorCache {
-    #[inline]
-    fn encode(&self, _s: &mut S) {}
-}
-
-impl<D: Decoder> Decodable<D> for PredecessorCache {
-    #[inline]
-    fn decode(_: &mut D) -> Self {
-        Self::new()
-    }
-}
-
-impl<CTX> HashStable<CTX> for PredecessorCache {
-    #[inline]
-    fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
-        // do nothing
-    }
-}
-
-TrivialTypeTraversalAndLiftImpls! {
-    PredecessorCache,
-}
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 40289af25..d8829e3e7 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -12,8 +12,8 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
 use rustc_index::vec::Idx;
 use rustc_middle::mir::interpret::{
-    alloc_range, read_target_uint, AllocId, Allocation, ConstAllocation, ConstValue, GlobalAlloc,
-    Pointer, Provenance,
+    alloc_range, read_target_uint, AllocBytes, AllocId, Allocation, ConstAllocation, ConstValue,
+    GlobalAlloc, Pointer, Provenance,
 };
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
@@ -580,7 +580,7 @@ fn write_scope_tree(
             continue;
         }
 
-        let mut_str = if local_decl.mutability == Mutability::Mut { "mut " } else { "" };
+        let mut_str = local_decl.mutability.prefix_str();
 
         let mut indented_decl =
             format!("{0:1$}let {2}{3:?}: {4:?}", INDENT, indent, mut_str, local, local_decl.ty);
@@ -787,21 +787,21 @@ pub fn write_allocations<'tcx>(
 /// After the hex dump, an ascii dump follows, replacing all unprintable characters (control
 /// characters or characters whose value is larger than 127) with a `.`
 /// This also prints provenance adequately.
-pub fn display_allocation<'a, 'tcx, Prov: Provenance, Extra>(
+pub fn display_allocation<'a, 'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>(
     tcx: TyCtxt<'tcx>,
-    alloc: &'a Allocation<Prov, Extra>,
-) -> RenderAllocation<'a, 'tcx, Prov, Extra> {
+    alloc: &'a Allocation<Prov, Extra, Bytes>,
+) -> RenderAllocation<'a, 'tcx, Prov, Extra, Bytes> {
     RenderAllocation { tcx, alloc }
 }
 
 #[doc(hidden)]
-pub struct RenderAllocation<'a, 'tcx, Prov: Provenance, Extra> {
+pub struct RenderAllocation<'a, 'tcx, Prov: Provenance, Extra, Bytes: AllocBytes> {
     tcx: TyCtxt<'tcx>,
-    alloc: &'a Allocation<Prov, Extra>,
+    alloc: &'a Allocation<Prov, Extra, Bytes>,
 }
 
-impl<'a, 'tcx, Prov: Provenance, Extra> std::fmt::Display
-    for RenderAllocation<'a, 'tcx, Prov, Extra>
+impl<'a, 'tcx, Prov: Provenance, Extra, Bytes: AllocBytes> std::fmt::Display
+    for RenderAllocation<'a, 'tcx, Prov, Extra, Bytes>
 {
     fn fmt(&self, w: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let RenderAllocation { tcx, alloc } = *self;
@@ -845,9 +845,9 @@ fn write_allocation_newline(
 /// The `prefix` argument allows callers to add an arbitrary prefix before each line (even if there
 /// is only one line). Note that your prefix should contain a trailing space as the lines are
 /// printed directly after it.
-fn write_allocation_bytes<'tcx, Prov: Provenance, Extra>(
+fn write_allocation_bytes<'tcx, Prov: Provenance, Extra, Bytes: AllocBytes>(
     tcx: TyCtxt<'tcx>,
-    alloc: &Allocation<Prov, Extra>,
+    alloc: &Allocation<Prov, Extra, Bytes>,
     w: &mut dyn std::fmt::Write,
     prefix: &str,
 ) -> std::fmt::Result {
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index a8a453222..b964c1852 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -8,7 +8,7 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::bit_set::BitMatrix;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::{Idx, IndexVec};
 use rustc_span::Span;
 use rustc_target::abi::VariantIdx;
 use smallvec::SmallVec;
@@ -135,11 +135,20 @@ rustc_index::newtype_index! {
     pub struct GeneratorSavedLocal {}
 }
 
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
+pub struct GeneratorSavedTy<'tcx> {
+    pub ty: Ty<'tcx>,
+    /// Source info corresponding to the local in the original MIR body.
+    pub source_info: SourceInfo,
+    /// Whether the local should be ignored for trait bound computations.
+    pub ignore_for_traits: bool,
+}
+
 /// The layout of generator state.
 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct GeneratorLayout<'tcx> {
     /// The type of every local stored inside the generator.
-    pub field_tys: IndexVec<GeneratorSavedLocal, Ty<'tcx>>,
+    pub field_tys: IndexVec<GeneratorSavedLocal, GeneratorSavedTy<'tcx>>,
 
     /// Which of the above fields are in each variant. Note that one field may
     /// be stored in multiple variants.
@@ -152,6 +161,8 @@ pub struct GeneratorLayout<'tcx> {
     /// Which saved locals are storage-live at the same time. Locals that do not
     /// have conflicts with each other are allowed to overlap in the computed
     /// layout.
+    #[type_foldable(identity)]
+    #[type_visitable(ignore)]
     pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
 }
 
@@ -278,13 +289,6 @@ pub struct ConstQualifs {
 /// instance of the closure is created, the corresponding free regions
 /// can be extracted from its type and constrained to have the given
 /// outlives relationship.
-///
-/// In some cases, we have to record outlives requirements between types and
-/// regions as well. In that case, if those types include any regions, those
-/// regions are recorded using their external names (`ReStatic`,
-/// `ReEarlyBound`, `ReFree`). We use these because in a query response we
-/// cannot use `ReVar` (which is what we use internally within the rest of the
-/// NLL code).
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ClosureRegionRequirements<'tcx> {
     /// The number of external regions defined on the closure. In our
@@ -381,16 +385,59 @@ pub enum ClosureOutlivesSubject<'tcx> {
     /// Subject is a type, typically a type parameter, but could also
     /// be a projection. Indicates a requirement like `T: 'a` being
     /// passed to the caller, where the type here is `T`.
-    ///
-    /// The type here is guaranteed not to contain any free regions at
-    /// present.
-    Ty(Ty<'tcx>),
+    Ty(ClosureOutlivesSubjectTy<'tcx>),
 
     /// Subject is a free region from the closure. Indicates a requirement
     /// like `'a: 'b` being passed to the caller; the region here is `'a`.
     Region(ty::RegionVid),
 }
 
+/// Represents a `ty::Ty` for use in [`ClosureOutlivesSubject`].
+///
+/// This abstraction is necessary because the type may include `ReVar` regions,
+/// which is what we use internally within NLL code, and they can't be used in
+/// a query response.
+///
+/// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
+/// type is not recognized as a binder for late-bound region.
+#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct ClosureOutlivesSubjectTy<'tcx> {
+    inner: Ty<'tcx>,
+}
+
+impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
+    /// All regions of `ty` must be of kind `ReVar` and must represent
+    /// universal regions *external* to the closure.
+    pub fn bind(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
+        let inner = tcx.fold_regions(ty, |r, depth| match r.kind() {
+            ty::ReVar(vid) => {
+                let br = ty::BoundRegion {
+                    var: ty::BoundVar::new(vid.index()),
+                    kind: ty::BrAnon(vid.as_u32(), None),
+                };
+                tcx.mk_re_late_bound(depth, br)
+            }
+            _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
+        });
+
+        Self { inner }
+    }
+
+    pub fn instantiate(
+        self,
+        tcx: TyCtxt<'tcx>,
+        mut map: impl FnMut(ty::RegionVid) -> ty::Region<'tcx>,
+    ) -> Ty<'tcx> {
+        tcx.fold_regions(self.inner, |r, depth| match r.kind() {
+            ty::ReLateBound(debruijn, br) => {
+                debug_assert_eq!(debruijn, depth);
+                map(ty::RegionVid::new(br.var.index()))
+            }
+            _ => bug!("unexpected region {r:?}"),
+        })
+    }
+}
+
 /// The constituent parts of a mir constant of kind ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConstant<'tcx> {
diff --git a/compiler/rustc_middle/src/mir/spanview.rs b/compiler/rustc_middle/src/mir/spanview.rs
index 887ee5715..28a3b51b7 100644
--- a/compiler/rustc_middle/src/mir/spanview.rs
+++ b/compiler/rustc_middle/src/mir/spanview.rs
@@ -11,7 +11,7 @@ use std::io::{self, Write};
 pub const TOOLTIP_INDENT: &str = "    ";
 
 const CARET: char = '\u{2038}'; // Unicode `CARET`
-const ANNOTATION_LEFT_BRACKET: char = '\u{298a}'; // Unicode `Z NOTATION RIGHT BINDING BRACKET
+const ANNOTATION_LEFT_BRACKET: char = '\u{298a}'; // Unicode `Z NOTATION RIGHT BINDING BRACKET`
 const ANNOTATION_RIGHT_BRACKET: char = '\u{2989}'; // Unicode `Z NOTATION LEFT BINDING BRACKET`
 const NEW_LINE_SPAN: &str = "</span>\n<span class=\"line\">";
 const HEADER: &str = r#"<!DOCTYPE html>
@@ -250,6 +250,7 @@ pub fn statement_kind_name(statement: &Statement<'_>) -> &'static str {
         AscribeUserType(..) => "AscribeUserType",
         Coverage(..) => "Coverage",
         Intrinsic(..) => "Intrinsic",
+        ConstEvalCounter => "ConstEvalCounter",
         Nop => "Nop",
     }
 }
@@ -670,7 +671,7 @@ fn fn_span(tcx: TyCtxt<'_>, def_id: DefId) -> Span {
 
 fn hir_body(tcx: TyCtxt<'_>, def_id: DefId) -> Option<&rustc_hir::Body<'_>> {
     let hir_node = tcx.hir().get_if_local(def_id).expect("expected DefId is local");
-    hir::map::associated_body(hir_node).map(|fn_body_id| tcx.hir().body(fn_body_id))
+    hir::map::associated_body(hir_node).map(|(_, fn_body_id)| tcx.hir().body(fn_body_id))
 }
 
 fn escape_html(s: &str) -> String {
diff --git a/compiler/rustc_middle/src/mir/switch_sources.rs b/compiler/rustc_middle/src/mir/switch_sources.rs
deleted file mode 100644
index b91c0c257..000000000
--- a/compiler/rustc_middle/src/mir/switch_sources.rs
+++ /dev/null
@@ -1,78 +0,0 @@
-//! Lazily compute the inverse of each `SwitchInt`'s switch targets. Modeled after
-//! `Predecessors`/`PredecessorCache`.
-
-use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_data_structures::sync::OnceCell;
-use rustc_index::vec::IndexVec;
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
-use smallvec::SmallVec;
-
-use crate::mir::{BasicBlock, BasicBlockData, Terminator, TerminatorKind};
-
-pub type SwitchSources = FxHashMap<(BasicBlock, BasicBlock), SmallVec<[Option<u128>; 1]>>;
-
-#[derive(Clone, Debug)]
-pub(super) struct SwitchSourceCache {
-    cache: OnceCell<SwitchSources>,
-}
-
-impl SwitchSourceCache {
-    #[inline]
-    pub(super) fn new() -> Self {
-        SwitchSourceCache { cache: OnceCell::new() }
-    }
-
-    /// Invalidates the switch source cache.
-    #[inline]
-    pub(super) fn invalidate(&mut self) {
-        self.cache = OnceCell::new();
-    }
-
-    /// Returns the switch sources for this MIR.
-    #[inline]
-    pub(super) fn compute(
-        &self,
-        basic_blocks: &IndexVec<BasicBlock, BasicBlockData<'_>>,
-    ) -> &SwitchSources {
-        self.cache.get_or_init(|| {
-            let mut switch_sources: SwitchSources = FxHashMap::default();
-            for (bb, data) in basic_blocks.iter_enumerated() {
-                if let Some(Terminator {
-                    kind: TerminatorKind::SwitchInt { targets, .. }, ..
-                }) = &data.terminator
-                {
-                    for (value, target) in targets.iter() {
-                        switch_sources.entry((target, bb)).or_default().push(Some(value));
-                    }
-                    switch_sources.entry((targets.otherwise(), bb)).or_default().push(None);
-                }
-            }
-
-            switch_sources
-        })
-    }
-}
-
-impl<S: Encoder> Encodable<S> for SwitchSourceCache {
-    #[inline]
-    fn encode(&self, _s: &mut S) {}
-}
-
-impl<D: Decoder> Decodable<D> for SwitchSourceCache {
-    #[inline]
-    fn decode(_: &mut D) -> Self {
-        Self::new()
-    }
-}
-
-impl<CTX> HashStable<CTX> for SwitchSourceCache {
-    #[inline]
-    fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
-        // do nothing
-    }
-}
-
-TrivialTypeTraversalAndLiftImpls! {
-    SwitchSourceCache,
-}
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 52c2b10cb..ae09562a8 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -355,6 +355,12 @@ pub enum StatementKind<'tcx> {
     /// This avoids adding a new block and a terminator for simple intrinsics.
     Intrinsic(Box<NonDivergingIntrinsic<'tcx>>),
 
+    /// Instructs the const eval interpreter to increment a counter; this counter is used to track
+    /// how many steps the interpreter has taken. It is used to prevent the user from writing const
+    /// code that runs for too long or infinitely. Other than in the const eval interpreter, this
+    /// is a no-op.
+    ConstEvalCounter,
+
     /// No-op. Useful for deleting instructions without affecting statement indices.
     Nop,
 }
@@ -665,6 +671,12 @@ pub enum TerminatorKind<'tcx> {
     /// as parameters, and `None` for the destination. Keep in mind that the `cleanup` path is not
     /// necessarily executed even in the case of a panic, for example in `-C panic=abort`. If the
     /// assertion does not fail, execution continues at the specified basic block.
+    ///
+    /// When overflow checking is disabled and this is run-time MIR (as opposed to compile-time MIR
+    /// that is used for CTFE), the following variants of this terminator behave as `goto target`:
+    /// - `OverflowNeg(..)`,
+    /// - `Overflow(op, ..)` if op is a "checkable" operation (add, sub, mul, shl, shr, but NOT
+    /// div or rem).
     Assert {
         cond: Operand<'tcx>,
         expected: bool,
@@ -1097,10 +1109,6 @@ pub enum Rvalue<'tcx> {
 
     /// Same as `BinaryOp`, but yields `(T, bool)` with a `bool` indicating an error condition.
     ///
-    /// When overflow checking is disabled and we are generating run-time code, the error condition
-    /// is false. Otherwise, and always during CTFE, the error condition is determined as described
-    /// below.
-    ///
     /// For addition, subtraction, and multiplication on integers the error condition is set when
     /// the infinite precision result would be unequal to the actual result.
     ///
@@ -1197,10 +1205,8 @@ pub enum AggregateKind<'tcx> {
     /// active field index would identity the field `c`
     Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
 
-    // Note: We can use LocalDefId since closures and generators a deaggregated
-    // before codegen.
-    Closure(LocalDefId, SubstsRef<'tcx>),
-    Generator(LocalDefId, SubstsRef<'tcx>, hir::Movability),
+    Closure(DefId, SubstsRef<'tcx>),
+    Generator(DefId, SubstsRef<'tcx>, hir::Movability),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 599f0b9d3..0aa2c500f 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -97,7 +97,7 @@ impl<'tcx> PlaceTy<'tcx> {
                     ty::Slice(..) => self.ty,
                     ty::Array(inner, _) if !from_end => tcx.mk_array(*inner, (to - from) as u64),
                     ty::Array(inner, size) if from_end => {
-                        let size = size.eval_usize(tcx, param_env);
+                        let size = size.eval_target_usize(tcx, param_env);
                         let len = size - (from as u64) - (to as u64);
                         tcx.mk_array(*inner, len)
                     }
@@ -162,10 +162,10 @@ impl<'tcx> Rvalue<'tcx> {
         match *self {
             Rvalue::Use(ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Repeat(ref operand, count) => {
-                tcx.mk_ty(ty::Array(operand.ty(local_decls, tcx), count))
+                tcx.mk_array_with_const_len(operand.ty(local_decls, tcx), count)
             }
             Rvalue::ThreadLocalRef(did) => {
-                let static_ty = tcx.type_of(did);
+                let static_ty = tcx.type_of(did).subst_identity();
                 if tcx.is_mutable_static(did) {
                     tcx.mk_mut_ptr(static_ty)
                 } else if tcx.is_foreign_item(did) {
@@ -194,20 +194,20 @@ impl<'tcx> Rvalue<'tcx> {
                 let lhs_ty = lhs.ty(local_decls, tcx);
                 let rhs_ty = rhs.ty(local_decls, tcx);
                 let ty = op.ty(tcx, lhs_ty, rhs_ty);
-                tcx.intern_tup(&[ty, tcx.types.bool])
+                tcx.mk_tup(&[ty, tcx.types.bool])
             }
             Rvalue::UnaryOp(UnOp::Not | UnOp::Neg, ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Discriminant(ref place) => place.ty(local_decls, tcx).ty.discriminant_ty(tcx),
             Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => tcx.types.usize,
             Rvalue::Aggregate(ref ak, ref ops) => match **ak {
                 AggregateKind::Array(ty) => tcx.mk_array(ty, ops.len() as u64),
-                AggregateKind::Tuple => tcx.mk_tup(ops.iter().map(|op| op.ty(local_decls, tcx))),
-                AggregateKind::Adt(did, _, substs, _, _) => {
-                    tcx.bound_type_of(did).subst(tcx, substs)
+                AggregateKind::Tuple => {
+                    tcx.mk_tup_from_iter(ops.iter().map(|op| op.ty(local_decls, tcx)))
                 }
-                AggregateKind::Closure(did, substs) => tcx.mk_closure(did.to_def_id(), substs),
+                AggregateKind::Adt(did, _, substs, _, _) => tcx.type_of(did).subst(tcx, substs),
+                AggregateKind::Closure(did, substs) => tcx.mk_closure(did, substs),
                 AggregateKind::Generator(did, substs, movability) => {
-                    tcx.mk_generator(did.to_def_id(), substs, movability)
+                    tcx.mk_generator(did, substs, movability)
                 }
             },
             Rvalue::ShallowInitBox(_, ty) => tcx.mk_box(ty),
diff --git a/compiler/rustc_middle/src/mir/traversal.rs b/compiler/rustc_middle/src/mir/traversal.rs
index 0b461d1ce..f37222cb2 100644
--- a/compiler/rustc_middle/src/mir/traversal.rs
+++ b/compiler/rustc_middle/src/mir/traversal.rs
@@ -1,7 +1,4 @@
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_data_structures::sync::OnceCell;
 use rustc_index::bit_set::BitSet;
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use super::*;
 
@@ -339,50 +336,3 @@ pub fn reverse_postorder<'a, 'tcx>(body: &'a Body<'tcx>) -> ReversePostorderIter
     let len = blocks.len();
     ReversePostorderIter { body, blocks, idx: len }
 }
-
-#[derive(Clone, Debug)]
-pub(super) struct PostorderCache {
-    cache: OnceCell<Vec<BasicBlock>>,
-}
-
-impl PostorderCache {
-    #[inline]
-    pub(super) fn new() -> Self {
-        PostorderCache { cache: OnceCell::new() }
-    }
-
-    /// Invalidates the postorder cache.
-    #[inline]
-    pub(super) fn invalidate(&mut self) {
-        self.cache = OnceCell::new();
-    }
-
-    /// Returns the `&[BasicBlocks]` represents the postorder graph for this MIR.
-    #[inline]
-    pub(super) fn compute(&self, body: &IndexVec<BasicBlock, BasicBlockData<'_>>) -> &[BasicBlock] {
-        self.cache.get_or_init(|| Postorder::new(body, START_BLOCK).map(|(bb, _)| bb).collect())
-    }
-}
-
-impl<S: Encoder> Encodable<S> for PostorderCache {
-    #[inline]
-    fn encode(&self, _s: &mut S) {}
-}
-
-impl<D: Decoder> Decodable<D> for PostorderCache {
-    #[inline]
-    fn decode(_: &mut D) -> Self {
-        Self::new()
-    }
-}
-
-impl<CTX> HashStable<CTX> for PostorderCache {
-    #[inline]
-    fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
-        // do nothing
-    }
-}
-
-TrivialTypeTraversalAndLiftImpls! {
-    PostorderCache,
-}
diff --git a/compiler/rustc_middle/src/mir/type_foldable.rs b/compiler/rustc_middle/src/mir/type_foldable.rs
index 0705b4cff..988158321 100644
--- a/compiler/rustc_middle/src/mir/type_foldable.rs
+++ b/compiler/rustc_middle/src/mir/type_foldable.rs
@@ -30,26 +30,29 @@ TrivialTypeTraversalImpls! {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx [InlineAsmTemplatePiece] {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx [InlineAsmTemplatePiece] {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        _folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(self)
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx [Span] {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx [Span] {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        _folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(self)
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<PlaceElem<'tcx>> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_place_elems(v))
-    }
-}
-
-impl<'tcx, R: Idx, C: Idx> TypeFoldable<'tcx> for BitMatrix<R, C> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _: &mut F) -> Result<Self, F::Error> {
-        Ok(self)
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<PlaceElem<'tcx>> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_place_elems(v))
     }
 }
diff --git a/compiler/rustc_middle/src/mir/type_visitable.rs b/compiler/rustc_middle/src/mir/type_visitable.rs
deleted file mode 100644
index d44c6809b..000000000
--- a/compiler/rustc_middle/src/mir/type_visitable.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-//! `TypeVisitable` implementations for MIR types
-
-use super::*;
-
-impl<'tcx, R: Idx, C: Idx> TypeVisitable<'tcx> for BitMatrix<R, C> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, _: &mut V) -> ControlFlow<V::BreakTy> {
-        ControlFlow::Continue(())
-    }
-}
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 1a264d2d5..5c056b299 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -323,7 +323,7 @@ macro_rules! make_mir_visitor {
                     self.visit_source_scope($(& $mutability)? *parent_scope);
                 }
                 if let Some((callee, callsite_span)) = inlined {
-                    let location = START_BLOCK.start_location();
+                    let location = Location::START;
 
                     self.visit_span($(& $mutability)? *callsite_span);
 
@@ -427,6 +427,7 @@ macro_rules! make_mir_visitor {
                             }
                         }
                     }
+                    StatementKind::ConstEvalCounter => {}
                     StatementKind::Nop => {}
                 }
             }
@@ -836,7 +837,7 @@ macro_rules! make_mir_visitor {
                 } = var_debug_info;
 
                 self.visit_source_info(source_info);
-                let location = START_BLOCK.start_location();
+                let location = Location::START;
                 match value {
                     VarDebugInfoContents::Const(c) => self.visit_constant(c, location),
                     VarDebugInfoContents::Place(place) =>
@@ -1025,7 +1026,7 @@ macro_rules! super_body {
         $self.visit_span($(& $mutability)? $body.span);
 
         for const_ in &$($mutability)? $body.required_consts {
-            let location = START_BLOCK.start_location();
+            let location = Location::START;
             $self.visit_constant(const_, location);
         }
     }
@@ -1044,7 +1045,7 @@ macro_rules! visit_place_fns {
             self.visit_local(&mut place.local, context, location);
 
             if let Some(new_projection) = self.process_projection(&place.projection, location) {
-                place.projection = self.tcx().intern_place_elems(&new_projection);
+                place.projection = self.tcx().mk_place_elems(&new_projection);
             }
         }
 
@@ -1213,7 +1214,7 @@ impl<'tcx> MirVisitable<'tcx> for Option<Terminator<'tcx>> {
 
 /// Extra information passed to `visit_ty` and friends to give context
 /// about where the type etc appears.
-#[derive(Debug)]
+#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
 pub enum TyContext {
     LocalDecl {
         /// The index of the local variable we are visiting.
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index e4bb3ce3d..78ee8a6a8 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -4,11 +4,12 @@ use crate::infer::canonical::Canonical;
 use crate::mir;
 use crate::traits;
 use crate::ty::fast_reject::SimplifiedType;
+use crate::ty::layout::{TyAndLayout, ValidityRequirement};
 use crate::ty::subst::{GenericArg, SubstsRef};
-use crate::ty::{self, layout::TyAndLayout, Ty, TyCtxt};
+use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::hir_id::{HirId, OwnerId};
-use rustc_query_system::query::{DefaultCacheSelector, VecCacheSelector};
+use rustc_query_system::query::{DefaultCacheSelector, SingleCacheSelector, VecCacheSelector};
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
@@ -45,7 +46,7 @@ pub trait Key: Sized {
 }
 
 impl Key for () {
-    type CacheSelector = DefaultCacheSelector<Self>;
+    type CacheSelector = SingleCacheSelector;
 
     #[inline(always)]
     fn query_crate_is_local(&self) -> bool {
@@ -696,3 +697,24 @@ impl Key for HirId {
         None
     }
 }
+
+impl<'tcx> Key for (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>) {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
+    // Just forward to `Ty<'tcx>`
+    #[inline(always)]
+    fn query_crate_is_local(&self) -> bool {
+        true
+    }
+
+    fn default_span(&self, _: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+
+    fn ty_adt_id(&self) -> Option<DefId> {
+        match self.1.value.kind() {
+            ty::Adt(adt, _) => Some(adt.did()),
+            _ => None,
+        }
+    }
+}
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 6bbf7fa39..5133da342 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -33,7 +33,7 @@ rustc_queries! {
     }
 
     query resolver_for_lowering(_: ()) -> &'tcx Steal<(ty::ResolverAstLowering, Lrc<ast::Crate>)> {
-        feedable
+        eval_always
         no_hash
         desc { "getting the resolver for lowering" }
     }
@@ -54,14 +54,14 @@ rustc_queries! {
     /// This is because the `hir_crate` query gives you access to all other items.
     /// To avoid this fate, do not call `tcx.hir().krate()`; instead,
     /// prefer wrappers like `tcx.visit_all_items_in_krate()`.
-    query hir_crate(key: ()) -> Crate<'tcx> {
+    query hir_crate(key: ()) -> &'tcx Crate<'tcx> {
         arena_cache
         eval_always
         desc { "getting the crate HIR" }
     }
 
     /// All items in the crate.
-    query hir_crate_items(_: ()) -> rustc_middle::hir::ModuleItems {
+    query hir_crate_items(_: ()) -> &'tcx rustc_middle::hir::ModuleItems {
         arena_cache
         eval_always
         desc { "getting HIR crate items" }
@@ -71,7 +71,7 @@ rustc_queries! {
     ///
     /// This can be conveniently accessed by `tcx.hir().visit_item_likes_in_module`.
     /// Avoid calling this query directly.
-    query hir_module_items(key: LocalDefId) -> rustc_middle::hir::ModuleItems {
+    query hir_module_items(key: LocalDefId) -> &'tcx rustc_middle::hir::ModuleItems {
         arena_cache
         desc { |tcx| "getting HIR module items in `{}`", tcx.def_path_str(key.to_def_id()) }
         cache_on_disk_if { true }
@@ -85,12 +85,12 @@ rustc_queries! {
         desc { |tcx| "getting HIR owner of `{}`", tcx.def_path_str(key.to_def_id()) }
     }
 
-    /// Gives access to the HIR ID for the given `LocalDefId` owner `key`.
+    /// Gives access to the HIR ID for the given `LocalDefId` owner `key` if any.
     ///
-    /// This can be conveniently accessed by methods on `tcx.hir()`.
-    /// Avoid calling this query directly.
-    query local_def_id_to_hir_id(key: LocalDefId) -> hir::HirId {
+    /// Definitions that were generated with no HIR, would be feeded to return `None`.
+    query opt_local_def_id_to_hir_id(key: LocalDefId) -> Option<hir::HirId>{
         desc { |tcx| "getting HIR ID of `{}`", tcx.def_path_str(key.to_def_id()) }
+        feedable
     }
 
     /// Gives access to the HIR node's parent for the HIR owner `key`.
@@ -152,7 +152,7 @@ rustc_queries! {
     /// to an alias, it will "skip" this alias to return the aliased type.
     ///
     /// [`DefId`]: rustc_hir::def_id::DefId
-    query type_of(key: DefId) -> Ty<'tcx> {
+    query type_of(key: DefId) -> ty::EarlyBinder<Ty<'tcx>> {
         desc { |tcx|
             "{action} `{path}`",
             action = {
@@ -167,6 +167,7 @@ rustc_queries! {
         }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     query collect_return_position_impl_trait_in_trait_tys(key: DefId)
@@ -183,6 +184,15 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    query unsizing_params_for_adt(key: DefId) -> &'tcx rustc_index::bit_set::BitSet<u32>
+    {
+        arena_cache
+        desc { |tcx|
+            "determining what parameters of `{}` can participate in unsizing",
+            tcx.def_path_str(key),
+        }
+    }
+
     query analysis(key: ()) -> Result<(), ErrorGuaranteed> {
         eval_always
         desc { "running analysis passes on this crate" }
@@ -209,11 +219,12 @@ rustc_queries! {
 
     /// Maps from the `DefId` of an item (trait/struct/enum/fn) to its
     /// associated generics.
-    query generics_of(key: DefId) -> ty::Generics {
+    query generics_of(key: DefId) -> &'tcx ty::Generics {
         desc { |tcx| "computing generics of `{}`", tcx.def_path_str(key) }
         arena_cache
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     /// Maps from the `DefId` of an item (trait/struct/enum/fn) to the
@@ -256,6 +267,7 @@ rustc_queries! {
         desc { |tcx| "finding item bounds for `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     /// Elaborated version of the predicates from `explicit_item_bounds`.
@@ -286,19 +298,19 @@ rustc_queries! {
     /// These are assembled from the following places:
     /// - `extern` blocks (depending on their `link` attributes)
     /// - the `libs` (`-l`) option
-    query native_libraries(_: CrateNum) -> Vec<NativeLib> {
+    query native_libraries(_: CrateNum) -> &'tcx Vec<NativeLib> {
         arena_cache
         desc { "looking up the native libraries of a linked crate" }
         separate_provide_extern
     }
 
-    query shallow_lint_levels_on(key: hir::OwnerId) -> rustc_middle::lint::ShallowLintLevelMap {
+    query shallow_lint_levels_on(key: hir::OwnerId) -> &'tcx rustc_middle::lint::ShallowLintLevelMap {
         eval_always // fetches `resolutions`
         arena_cache
         desc { |tcx| "looking up lint levels for `{}`", tcx.def_path_str(key.to_def_id()) }
     }
 
-    query lint_expectations(_: ()) -> Vec<(LintExpectationId, LintExpectation)> {
+    query lint_expectations(_: ()) -> &'tcx Vec<(LintExpectationId, LintExpectation)> {
         arena_cache
         desc { "computing `#[expect]`ed lints in this crate" }
     }
@@ -338,7 +350,7 @@ rustc_queries! {
     }
 
     /// Set of param indexes for type params that are in the type's representation
-    query params_in_repr(key: DefId) -> rustc_index::bit_set::BitSet<u32> {
+    query params_in_repr(key: DefId) -> &'tcx rustc_index::bit_set::BitSet<u32> {
         desc { "finding type parameters in the representation" }
         arena_cache
         no_hash
@@ -355,16 +367,23 @@ rustc_queries! {
     }
 
     /// Create a THIR tree for debugging.
-    query thir_tree(key: ty::WithOptConstParam<LocalDefId>) -> String {
+    query thir_tree(key: ty::WithOptConstParam<LocalDefId>) -> &'tcx String {
         no_hash
         arena_cache
         desc { |tcx| "constructing THIR tree for `{}`", tcx.def_path_str(key.did.to_def_id()) }
     }
 
+    /// Create a list-like THIR representation for debugging.
+    query thir_flat(key: ty::WithOptConstParam<LocalDefId>) -> &'tcx String {
+        no_hash
+        arena_cache
+        desc { |tcx| "constructing flat THIR representation for `{}`", tcx.def_path_str(key.did.to_def_id()) }
+    }
+
     /// Set of all the `DefId`s in this crate that have MIR associated with
     /// them. This includes all the body owners, but also things like struct
     /// constructors.
-    query mir_keys(_: ()) -> rustc_data_structures::fx::FxIndexSet<LocalDefId> {
+    query mir_keys(_: ()) -> &'tcx rustc_data_structures::fx::FxIndexSet<LocalDefId> {
         arena_cache
         desc { "getting a list of all mir_keys" }
     }
@@ -460,17 +479,24 @@ rustc_queries! {
         }
     }
 
-    query symbols_for_closure_captures(
-        key: (LocalDefId, LocalDefId)
-    ) -> Vec<rustc_span::Symbol> {
-        arena_cache
+    query closure_typeinfo(key: LocalDefId) -> ty::ClosureTypeInfo<'tcx> {
         desc {
-            |tcx| "finding symbols for captures of closure `{}` in `{}`",
-            tcx.def_path_str(key.1.to_def_id()),
-            tcx.def_path_str(key.0.to_def_id())
+            |tcx| "finding symbols for captures of closure `{}`",
+            tcx.def_path_str(key.to_def_id())
         }
     }
 
+    query mir_generator_witnesses(key: DefId) -> &'tcx mir::GeneratorLayout<'tcx> {
+        arena_cache
+        desc { |tcx| "generator witness types for `{}`", tcx.def_path_str(key) }
+        cache_on_disk_if { key.is_local() }
+        separate_provide_extern
+    }
+
+    query check_generator_obligations(key: LocalDefId) {
+        desc { |tcx| "verify auto trait bounds for generator interior type `{}`", tcx.def_path_str(key.to_def_id()) }
+    }
+
     /// MIR after our optimization passes have run. This is MIR that is ready
     /// for codegen. This is also the only query that can fetch non-local MIR, at present.
     query optimized_mir(key: DefId) -> &'tcx mir::Body<'tcx> {
@@ -481,14 +507,14 @@ rustc_queries! {
 
     /// Returns coverage summary info for a function, after executing the `InstrumentCoverage`
     /// MIR pass (assuming the -Cinstrument-coverage option is enabled).
-    query coverageinfo(key: ty::InstanceDef<'tcx>) -> mir::CoverageInfo {
+    query coverageinfo(key: ty::InstanceDef<'tcx>) -> &'tcx mir::CoverageInfo {
         desc { |tcx| "retrieving coverage info from MIR for `{}`", tcx.def_path_str(key.def_id()) }
         arena_cache
     }
 
     /// Returns the `CodeRegions` for a function that has instrumented coverage, in case the
     /// function was optimized out before codegen, and before being added to the Coverage Map.
-    query covered_code_regions(key: DefId) -> Vec<&'tcx mir::coverage::CodeRegion> {
+    query covered_code_regions(key: DefId) -> &'tcx Vec<&'tcx mir::coverage::CodeRegion> {
         desc {
             |tcx| "retrieving the covered `CodeRegion`s, if instrumented, for `{}`",
             tcx.def_path_str(key)
@@ -530,7 +556,7 @@ rustc_queries! {
         desc { "erasing regions from `{}`", ty }
     }
 
-    query wasm_import_module_map(_: CrateNum) -> FxHashMap<DefId, String> {
+    query wasm_import_module_map(_: CrateNum) -> &'tcx FxHashMap<DefId, String> {
         arena_cache
         desc { "getting wasm import module map" }
     }
@@ -566,6 +592,7 @@ rustc_queries! {
         desc { |tcx| "computing explicit predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     /// Returns the inferred outlives predicates (e.g., for `struct
@@ -574,6 +601,7 @@ rustc_queries! {
         desc { |tcx| "computing inferred outlives predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     /// Maps from the `DefId` of a trait to the list of
@@ -605,7 +633,7 @@ rustc_queries! {
         desc { |tcx| "computing the bounds for type parameter `{}`", tcx.hir().ty_param_name(key.1) }
     }
 
-    query trait_def(key: DefId) -> ty::TraitDef {
+    query trait_def(key: DefId) -> &'tcx ty::TraitDef {
         desc { |tcx| "computing trait definition for `{}`", tcx.def_path_str(key) }
         arena_cache
         cache_on_disk_if { key.is_local() }
@@ -676,7 +704,7 @@ rustc_queries! {
     }
 
     /// Gets a map with the variance of every item; use `item_variance` instead.
-    query crate_variances(_: ()) -> ty::CrateVariancesMap<'tcx> {
+    query crate_variances(_: ()) -> &'tcx ty::CrateVariancesMap<'tcx> {
         arena_cache
         desc { "computing the variances for items in this crate" }
     }
@@ -689,7 +717,7 @@ rustc_queries! {
     }
 
     /// Maps from thee `DefId` of a type to its (inferred) outlives.
-    query inferred_outlives_crate(_: ()) -> ty::CratePredicatesMap<'tcx> {
+    query inferred_outlives_crate(_: ()) -> &'tcx ty::CratePredicatesMap<'tcx> {
         arena_cache
         desc { "computing the inferred outlives predicates for items in this crate" }
     }
@@ -704,13 +732,13 @@ rustc_queries! {
     /// Maps from a trait item to the trait item "descriptor".
     query associated_item(key: DefId) -> ty::AssocItem {
         desc { |tcx| "computing associated item data for `{}`", tcx.def_path_str(key) }
-        arena_cache
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
+        feedable
     }
 
     /// Collects the associated items defined on a trait or impl.
-    query associated_items(key: DefId) -> ty::AssocItems<'tcx> {
+    query associated_items(key: DefId) -> &'tcx ty::AssocItems {
         arena_cache
         desc { |tcx| "collecting associated items of `{}`", tcx.def_path_str(key) }
     }
@@ -736,11 +764,31 @@ rustc_queries! {
     ///
     /// The map returned for `tcx.impl_item_implementor_ids(impl_id)` would be
     ///`{ trait_f: impl_f, trait_g: impl_g }`
-    query impl_item_implementor_ids(impl_id: DefId) -> FxHashMap<DefId, DefId> {
+    query impl_item_implementor_ids(impl_id: DefId) -> &'tcx FxHashMap<DefId, DefId> {
         arena_cache
         desc { |tcx| "comparing impl items against trait for `{}`", tcx.def_path_str(impl_id) }
     }
 
+    /// Given `fn_def_id` of a trait or of an impl that implements a given trait:
+    /// if `fn_def_id` is the def id of a function defined inside a trait, then it creates and returns
+    /// the associated items that correspond to each impl trait in return position for that trait.
+    /// if `fn_def_id` is the def id of a function defined inside an impl that implements a trait, then it
+    /// creates and returns the associated items that correspond to each impl trait in return position
+    /// of the implemented trait.
+    query associated_items_for_impl_trait_in_trait(fn_def_id: DefId) -> &'tcx [DefId] {
+        desc { |tcx| "creating associated items for impl trait in trait returned by `{}`", tcx.def_path_str(fn_def_id) }
+        cache_on_disk_if { fn_def_id.is_local() }
+        separate_provide_extern
+    }
+
+    /// Given an impl trait in trait `opaque_ty_def_id`, create and return the corresponding
+    /// associated item.
+    query associated_item_for_impl_trait_in_trait(opaque_ty_def_id: LocalDefId) -> LocalDefId {
+        desc { |tcx| "creates the associated item corresponding to the opaque type `{}`", tcx.def_path_str(opaque_ty_def_id.to_def_id()) }
+        cache_on_disk_if { true }
+        separate_provide_extern
+    }
+
     /// Given an `impl_id`, return the trait it implements.
     /// Return `None` if this is an inherent impl.
     query impl_trait_ref(impl_id: DefId) -> Option<ty::EarlyBinder<ty::TraitRef<'tcx>>> {
@@ -754,7 +802,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query issue33140_self_ty(key: DefId) -> Option<ty::Ty<'tcx>> {
+    query issue33140_self_ty(key: DefId) -> Option<ty::EarlyBinder<ty::Ty<'tcx>>> {
         desc { |tcx| "computing Self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
     }
 
@@ -796,15 +844,6 @@ rustc_queries! {
         }
     }
 
-    /// HACK: when evaluated, this reports an "unsafe derive on repr(packed)" error.
-    ///
-    /// Unsafety checking is executed for each method separately, but we only want
-    /// to emit this error once per derive. As there are some impls with multiple
-    /// methods, we use a query for deduplication.
-    query unsafe_derive_on_repr_packed(key: LocalDefId) -> () {
-        desc { |tcx| "processing `{}`", tcx.def_path_str(key.to_def_id()) }
-    }
-
     /// Returns the types assumed to be well formed while "inside" of the given item.
     ///
     /// Note that we've liberated the late bound regions of function signatures, so
@@ -814,7 +853,7 @@ rustc_queries! {
     }
 
     /// Computes the signature of the function.
-    query fn_sig(key: DefId) -> ty::PolyFnSig<'tcx> {
+    query fn_sig(key: DefId) -> ty::EarlyBinder<ty::PolyFnSig<'tcx>> {
         desc { |tcx| "computing function signature of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
@@ -866,7 +905,7 @@ rustc_queries! {
     ///
     /// The second return value maps from ADTs to ignored derived traits (e.g. Debug and Clone) and
     /// their respective impl (i.e., part of the derive macro)
-    query live_symbols_and_ignored_derived_traits(_: ()) -> (
+    query live_symbols_and_ignored_derived_traits(_: ()) -> &'tcx (
         FxHashSet<LocalDefId>,
         FxHashMap<LocalDefId, Vec<(DefId, DefId)>>
     ) {
@@ -946,7 +985,7 @@ rustc_queries! {
 
     /// Gets a complete map from all types to their inherent impls.
     /// Not meant to be used directly outside of coherence.
-    query crate_inherent_impls(k: ()) -> CrateInherentImpls {
+    query crate_inherent_impls(k: ()) -> &'tcx CrateInherentImpls {
         arena_cache
         desc { "finding all inherent impls defined in crate" }
     }
@@ -1081,7 +1120,7 @@ rustc_queries! {
         desc { "checking for private elements in public interfaces" }
     }
 
-    query reachable_set(_: ()) -> FxHashSet<LocalDefId> {
+    query reachable_set(_: ()) -> &'tcx FxHashSet<LocalDefId> {
         arena_cache
         desc { "reachability" }
     }
@@ -1093,7 +1132,7 @@ rustc_queries! {
     }
 
     /// Generates a MIR body for the shim.
-    query mir_shims(key: ty::InstanceDef<'tcx>) -> mir::Body<'tcx> {
+    query mir_shims(key: ty::InstanceDef<'tcx>) -> &'tcx mir::Body<'tcx> {
         arena_cache
         desc { |tcx| "generating MIR shim for `{}`", tcx.def_path_str(key.def_id()) }
     }
@@ -1110,6 +1149,15 @@ rustc_queries! {
         desc { |tcx| "looking up definition kind of `{}`", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
         separate_provide_extern
+        feedable
+    }
+
+    /// The `opt_rpitit_info` query returns the pair of the def id of the function where the RPIT
+    /// is defined and the opaque def id if any.
+    query opt_rpitit_info(def_id: DefId) -> Option<ty::ImplTraitInTraitData> {
+        desc { |tcx| "opt_rpitit_info `{}`", tcx.def_path_str(def_id) }
+        cache_on_disk_if { def_id.is_local() }
+        feedable
     }
 
     /// Gets the span for the definition.
@@ -1125,6 +1173,7 @@ rustc_queries! {
         desc { |tcx| "looking up span for `{}`'s identifier", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
         separate_provide_extern
+        feedable
     }
 
     query lookup_stability(def_id: DefId) -> Option<attr::Stability> {
@@ -1157,6 +1206,7 @@ rustc_queries! {
     /// Determines whether an item is annotated with `doc(hidden)`.
     query is_doc_hidden(def_id: DefId) -> bool {
         desc { |tcx| "checking whether `{}` is `doc(hidden)`", tcx.def_path_str(def_id) }
+        separate_provide_extern
     }
 
     /// Determines whether an item is annotated with `doc(notable_trait)`.
@@ -1172,7 +1222,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query codegen_fn_attrs(def_id: DefId) -> CodegenFnAttrs {
+    query codegen_fn_attrs(def_id: DefId) -> &'tcx CodegenFnAttrs {
         desc { |tcx| "computing codegen attributes of `{}`", tcx.def_path_str(def_id) }
         arena_cache
         cache_on_disk_if { def_id.is_local() }
@@ -1190,7 +1240,7 @@ rustc_queries! {
     }
     /// Gets the rendered value of the specified constant or associated constant.
     /// Used by rustdoc.
-    query rendered_const(def_id: DefId) -> String {
+    query rendered_const(def_id: DefId) -> &'tcx String {
         arena_cache
         desc { |tcx| "rendering constant initializer of `{}`", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
@@ -1249,12 +1299,12 @@ rustc_queries! {
     }
 
     /// Given a trait `trait_id`, return all known `impl` blocks.
-    query trait_impls_of(trait_id: DefId) -> ty::trait_def::TraitImpls {
+    query trait_impls_of(trait_id: DefId) -> &'tcx ty::trait_def::TraitImpls {
         arena_cache
         desc { |tcx| "finding trait impls of `{}`", tcx.def_path_str(trait_id) }
     }
 
-    query specialization_graph_of(trait_id: DefId) -> specialization_graph::Graph {
+    query specialization_graph_of(trait_id: DefId) -> &'tcx specialization_graph::Graph {
         arena_cache
         desc { |tcx| "building specialization graph of trait `{}`", tcx.def_path_str(trait_id) }
         cache_on_disk_if { true }
@@ -1262,6 +1312,9 @@ rustc_queries! {
     query object_safety_violations(trait_id: DefId) -> &'tcx [traits::ObjectSafetyViolation] {
         desc { |tcx| "determining object safety of trait `{}`", tcx.def_path_str(trait_id) }
     }
+    query check_is_object_safe(trait_id: DefId) -> bool {
+        desc { |tcx| "checking if trait `{}` is object safe", tcx.def_path_str(trait_id) }
+    }
 
     /// Gets the ParameterEnvironment for a given item; this environment
     /// will be in "user-facing" mode, meaning that it is suitable for
@@ -1381,7 +1434,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query dependency_formats(_: ()) -> Lrc<crate::middle::dependency_format::Dependencies> {
+    query dependency_formats(_: ()) -> &'tcx Lrc<crate::middle::dependency_format::Dependencies> {
         arena_cache
         desc { "getting the linkage format of all dependencies" }
     }
@@ -1462,6 +1515,7 @@ rustc_queries! {
         desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
         separate_provide_extern
+        feedable
     }
 
     query check_well_formed(key: hir::OwnerId) -> () {
@@ -1481,7 +1535,7 @@ rustc_queries! {
     // Does not include external symbols that don't have a corresponding DefId,
     // like the compiler-generated `main` function and so on.
     query reachable_non_generics(_: CrateNum)
-        -> DefIdMap<SymbolExportInfo> {
+        -> &'tcx DefIdMap<SymbolExportInfo> {
         arena_cache
         desc { "looking up the exported symbols of a crate" }
         separate_provide_extern
@@ -1504,7 +1558,7 @@ rustc_queries! {
     /// added or removed in any upstream crate. Instead use the narrower
     /// `upstream_monomorphizations_for`, `upstream_drop_glue_for`, or, even
     /// better, `Instance::upstream_monomorphization()`.
-    query upstream_monomorphizations(_: ()) -> DefIdMap<FxHashMap<SubstsRef<'tcx>, CrateNum>> {
+    query upstream_monomorphizations(_: ()) -> &'tcx DefIdMap<FxHashMap<SubstsRef<'tcx>, CrateNum>> {
         arena_cache
         desc { "collecting available upstream monomorphizations" }
     }
@@ -1519,7 +1573,6 @@ rustc_queries! {
     query upstream_monomorphizations_for(def_id: DefId)
         -> Option<&'tcx FxHashMap<SubstsRef<'tcx>, CrateNum>>
     {
-        arena_cache
         desc { |tcx|
             "collecting available upstream monomorphizations for `{}`",
             tcx.def_path_str(def_id),
@@ -1547,7 +1600,7 @@ rustc_queries! {
     }
 
     /// Returns a list of all `extern` blocks of a crate.
-    query foreign_modules(_: CrateNum) -> FxHashMap<DefId, ForeignModule> {
+    query foreign_modules(_: CrateNum) -> &'tcx FxHashMap<DefId, ForeignModule> {
         arena_cache
         desc { "looking up the foreign modules of a linked crate" }
         separate_provide_extern
@@ -1581,7 +1634,7 @@ rustc_queries! {
 
     /// Gets the extra data to put in each output filename for a crate.
     /// For example, compiling the `foo` crate with `extra-filename=-a` creates a `libfoo-b.rlib` file.
-    query extra_filename(_: CrateNum) -> String {
+    query extra_filename(_: CrateNum) -> &'tcx String {
         arena_cache
         eval_always
         desc { "looking up the extra filename for a crate" }
@@ -1589,7 +1642,7 @@ rustc_queries! {
     }
 
     /// Gets the paths where the crate came from in the file system.
-    query crate_extern_paths(_: CrateNum) -> Vec<PathBuf> {
+    query crate_extern_paths(_: CrateNum) -> &'tcx Vec<PathBuf> {
         arena_cache
         eval_always
         desc { "looking up the paths for extern crates" }
@@ -1619,16 +1672,16 @@ rustc_queries! {
 
     /// Does lifetime resolution on items. Importantly, we can't resolve
     /// lifetimes directly on things like trait methods, because of trait params.
-    /// See `rustc_resolve::late::lifetimes for details.
-    query resolve_lifetimes(_: hir::OwnerId) -> ResolveLifetimes {
+    /// See `rustc_resolve::late::lifetimes` for details.
+    query resolve_bound_vars(_: hir::OwnerId) -> &'tcx ResolveBoundVars {
         arena_cache
         desc { "resolving lifetimes" }
     }
-    query named_region_map(_: hir::OwnerId) ->
-        Option<&'tcx FxHashMap<ItemLocalId, Region>> {
+    query named_variable_map(_: hir::OwnerId) ->
+        Option<&'tcx FxHashMap<ItemLocalId, ResolvedArg>> {
         desc { "looking up a named region" }
     }
-    query is_late_bound_map(_: LocalDefId) -> Option<&'tcx FxIndexSet<LocalDefId>> {
+    query is_late_bound_map(_: hir::OwnerId) -> Option<&'tcx FxIndexSet<ItemLocalId>> {
         desc { "testing if a region is late bound" }
     }
     /// For a given item's generic parameter, gets the default lifetimes to be used
@@ -1660,6 +1713,7 @@ rustc_queries! {
     query visibility(def_id: DefId) -> ty::Visibility<DefId> {
         desc { |tcx| "computing visibility of `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
+        feedable
     }
 
     query inhabited_predicate_adt(key: DefId) -> ty::inhabitedness::InhabitedPredicate<'tcx> {
@@ -1691,7 +1745,7 @@ rustc_queries! {
         desc { |tcx| "computing crate imported by `{}`", tcx.def_path_str(def_id.to_def_id()) }
     }
 
-    query lib_features(_: ()) -> LibFeatures {
+    query lib_features(_: ()) -> &'tcx LibFeatures {
         arena_cache
         desc { "calculating the lib features map" }
     }
@@ -1699,7 +1753,7 @@ rustc_queries! {
         desc { "calculating the lib features defined in a crate" }
         separate_provide_extern
     }
-    query stability_implications(_: CrateNum) -> FxHashMap<Symbol, Symbol> {
+    query stability_implications(_: CrateNum) -> &'tcx FxHashMap<Symbol, Symbol> {
         arena_cache
         desc { "calculating the implications between `#[unstable]` features defined in a crate" }
         separate_provide_extern
@@ -1710,14 +1764,14 @@ rustc_queries! {
         separate_provide_extern
     }
     /// Returns the lang items defined in another crate by loading it from metadata.
-    query get_lang_items(_: ()) -> LanguageItems {
+    query get_lang_items(_: ()) -> &'tcx LanguageItems {
         arena_cache
         eval_always
         desc { "calculating the lang items map" }
     }
 
     /// Returns all diagnostic items defined in all crates.
-    query all_diagnostic_items(_: ()) -> rustc_hir::diagnostic_items::DiagnosticItems {
+    query all_diagnostic_items(_: ()) -> &'tcx rustc_hir::diagnostic_items::DiagnosticItems {
         arena_cache
         eval_always
         desc { "calculating the diagnostic items map" }
@@ -1730,7 +1784,7 @@ rustc_queries! {
     }
 
     /// Returns the diagnostic items defined in a crate.
-    query diagnostic_items(_: CrateNum) -> rustc_hir::diagnostic_items::DiagnosticItems {
+    query diagnostic_items(_: CrateNum) -> &'tcx rustc_hir::diagnostic_items::DiagnosticItems {
         arena_cache
         desc { "calculating the diagnostic items map in a crate" }
         separate_provide_extern
@@ -1740,11 +1794,11 @@ rustc_queries! {
         desc { "calculating the missing lang items in a crate" }
         separate_provide_extern
     }
-    query visible_parent_map(_: ()) -> DefIdMap<DefId> {
+    query visible_parent_map(_: ()) -> &'tcx DefIdMap<DefId> {
         arena_cache
         desc { "calculating the visible parent map" }
     }
-    query trimmed_def_paths(_: ()) -> FxHashMap<DefId, Symbol> {
+    query trimmed_def_paths(_: ()) -> &'tcx FxHashMap<DefId, Symbol> {
         arena_cache
         desc { "calculating trimmed def paths" }
     }
@@ -1753,14 +1807,14 @@ rustc_queries! {
         desc { "seeing if we're missing an `extern crate` item for this crate" }
         separate_provide_extern
     }
-    query used_crate_source(_: CrateNum) -> Lrc<CrateSource> {
+    query used_crate_source(_: CrateNum) -> &'tcx Lrc<CrateSource> {
         arena_cache
         eval_always
         desc { "looking at the source for a crate" }
         separate_provide_extern
     }
     /// Returns the debugger visualizers defined for this crate.
-    query debugger_visualizers(_: CrateNum) -> Vec<rustc_span::DebuggerVisualizerFile> {
+    query debugger_visualizers(_: CrateNum) -> &'tcx Vec<rustc_span::DebuggerVisualizerFile> {
         arena_cache
         desc { "looking up the debugger visualizers for this crate" }
         separate_provide_extern
@@ -1791,14 +1845,11 @@ rustc_queries! {
     query maybe_unused_trait_imports(_: ()) -> &'tcx FxIndexSet<LocalDefId> {
         desc { "fetching potentially unused trait imports" }
     }
-    query maybe_unused_extern_crates(_: ()) -> &'tcx [(LocalDefId, Span)] {
-        desc { "looking up all possibly unused extern crates" }
-    }
     query names_imported_by_glob_use(def_id: LocalDefId) -> &'tcx FxHashSet<Symbol> {
         desc { |tcx| "finding names imported by glob use for `{}`", tcx.def_path_str(def_id.to_def_id()) }
     }
 
-    query stability_index(_: ()) -> stability::Index {
+    query stability_index(_: ()) -> &'tcx stability::Index {
         arena_cache
         eval_always
         desc { "calculating the stability index for the local crate" }
@@ -1815,6 +1866,11 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    query trait_impls_in_crate(_: CrateNum) -> &'tcx [DefId] {
+        desc { "fetching all trait impls in a crate" }
+        separate_provide_extern
+    }
+
     /// The list of symbols exported from the given crate.
     ///
     /// - All names contained in `exported_symbols(cnum)` are guaranteed to
@@ -1865,6 +1921,7 @@ rustc_queries! {
     query output_filenames(_: ()) -> &'tcx Arc<OutputFilenames> {
         feedable
         desc { "getting output filenames" }
+        arena_cache
     }
 
     /// Do not call this query directly: invoke `normalize` instead.
@@ -2034,7 +2091,7 @@ rustc_queries! {
         remap_env_constness
     }
 
-    query supported_target_features(_: CrateNum) -> FxHashMap<String, Option<Symbol>> {
+    query supported_target_features(_: CrateNum) -> &'tcx FxHashMap<String, Option<Symbol>> {
         arena_cache
         eval_always
         desc { "looking up supported target features" }
@@ -2051,6 +2108,18 @@ rustc_queries! {
         desc { "looking up enabled feature gates" }
     }
 
+    query metadata_loader((): ()) -> &'tcx Steal<Box<rustc_session::cstore::MetadataLoaderDyn>> {
+        feedable
+        no_hash
+        desc { "raw operations for metadata file access" }
+    }
+
+    query crate_for_resolver((): ()) -> &'tcx Steal<rustc_ast::ast::Crate> {
+        feedable
+        no_hash
+        desc { "the ast before macro expansion and name resolution" }
+    }
+
     /// Attempt to resolve the given `DefId` to an `Instance`, for the
     /// given generics args (`SubstsRef`), returning one of:
     ///  * `Ok(Some(instance))` on success
@@ -2093,34 +2162,31 @@ rustc_queries! {
     /// span) for an *existing* error. Therefore, it is best-effort, and may never handle
     /// all of the cases that the normal `ty::Ty`-based wfcheck does. This is fine,
     /// because the `ty::Ty`-based wfcheck is always run.
-    query diagnostic_hir_wf_check(key: (ty::Predicate<'tcx>, traits::WellFormedLoc)) -> Option<traits::ObligationCause<'tcx>> {
+    query diagnostic_hir_wf_check(
+        key: (ty::Predicate<'tcx>, traits::WellFormedLoc)
+    ) -> &'tcx Option<traits::ObligationCause<'tcx>> {
         arena_cache
         eval_always
         no_hash
         desc { "performing HIR wf-checking for predicate `{:?}` at item `{:?}`", key.0, key.1 }
     }
 
-
     /// The list of backend features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`,
     /// `--target` and similar).
-    query global_backend_features(_: ()) -> Vec<String> {
+    query global_backend_features(_: ()) -> &'tcx Vec<String> {
         arena_cache
         eval_always
         desc { "computing the backend features for CLI flags" }
     }
 
-    query generator_diagnostic_data(key: DefId) -> Option<GeneratorDiagnosticData<'tcx>> {
+    query generator_diagnostic_data(key: DefId) -> &'tcx Option<GeneratorDiagnosticData<'tcx>> {
         arena_cache
         desc { |tcx| "looking up generator diagnostic data of `{}`", tcx.def_path_str(key) }
         separate_provide_extern
     }
 
-    query permits_uninit_init(key: TyAndLayout<'tcx>) -> bool {
-        desc { "checking to see if `{}` permits being left uninit", key.ty }
-    }
-
-    query permits_zero_init(key: TyAndLayout<'tcx>) -> bool {
-        desc { "checking to see if `{}` permits being left zeroed", key.ty }
+    query check_validity_requirement(key: (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, ty::layout::LayoutError<'tcx>> {
+        desc { "checking validity requirement for `{}`: {}", key.1.value, key.0 }
     }
 
     query compare_impl_const(
@@ -2133,4 +2199,23 @@ rustc_queries! {
         desc { |tcx| "deducing parameter attributes for {}", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
+
+    query doc_link_resolutions(def_id: DefId) -> &'tcx DocLinkResMap {
+        eval_always
+        desc { "resolutions for documentation links for a module" }
+        separate_provide_extern
+    }
+
+    query doc_link_traits_in_scope(def_id: DefId) -> &'tcx [DefId] {
+        eval_always
+        desc { "traits in scope for documentation links for a module" }
+        separate_provide_extern
+    }
+
+    /// Used in `super_combine_consts` to ICE if the type of the two consts are definitely not going to end up being
+    /// equal to eachother. This might return `Ok` even if the types are unequal, but will never return `Err` if
+    /// the types might be equal.
+    query check_tys_might_be_eq(arg: Canonical<'tcx, (ty::ParamEnv<'tcx>, Ty<'tcx>, Ty<'tcx>)>) -> Result<(), NoSolution> {
+        desc { "check whether two const param are definitely not equal to eachother"}
+    }
 }
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 5f320708c..3b11fab8c 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -20,7 +20,7 @@ use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Field, Mutability, UnOp};
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{self, AdtDef, Ty, UpvarSubsts};
+use rustc_middle::ty::{self, AdtDef, FnSig, Ty, UpvarSubsts};
 use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span, Symbol, DUMMY_SP};
@@ -32,7 +32,12 @@ use std::ops::Index;
 pub mod visit;
 
 macro_rules! thir_with_elements {
-    ($($name:ident: $id:ty => $value:ty => $format:literal,)*) => {
+    (
+        $($field_name:ident: $field_ty:ty,)*
+
+    @elements:
+        $($name:ident: $id:ty => $value:ty => $format:literal,)*
+    ) => {
         $(
             newtype_index! {
                 #[derive(HashStable)]
@@ -47,14 +52,20 @@ macro_rules! thir_with_elements {
         #[derive(Debug, HashStable, Clone)]
         pub struct Thir<'tcx> {
             $(
+                pub $field_name: $field_ty,
+            )*
+            $(
                 pub $name: IndexVec<$id, $value>,
             )*
         }
 
         impl<'tcx> Thir<'tcx> {
-            pub fn new() -> Thir<'tcx> {
+            pub fn new($($field_name: $field_ty,)*) -> Thir<'tcx> {
                 Thir {
                     $(
+                        $field_name,
+                    )*
+                    $(
                         $name: IndexVec::new(),
                     )*
                 }
@@ -75,6 +86,9 @@ macro_rules! thir_with_elements {
 pub const UPVAR_ENV_PARAM: ParamId = ParamId::from_u32(0);
 
 thir_with_elements! {
+    body_type: BodyTy<'tcx>,
+
+@elements:
     arms: ArmId => Arm<'tcx> => "a{}",
     blocks: BlockId => Block => "b{}",
     exprs: ExprId => Expr<'tcx> => "e{}",
@@ -82,6 +96,12 @@ thir_with_elements! {
     params: ParamId => Param<'tcx> => "p{}",
 }
 
+#[derive(Debug, HashStable, Clone)]
+pub enum BodyTy<'tcx> {
+    Const(Ty<'tcx>),
+    Fn(FnSig<'tcx>),
+}
+
 /// Description of a type-checked function parameter.
 #[derive(Clone, Debug, HashStable)]
 pub struct Param<'tcx> {
@@ -217,6 +237,9 @@ pub struct LocalVarId(pub hir::HirId);
 /// A THIR expression.
 #[derive(Clone, Debug, HashStable)]
 pub struct Expr<'tcx> {
+    /// kind of expression
+    pub kind: ExprKind<'tcx>,
+
     /// The type of this expression
     pub ty: Ty<'tcx>,
 
@@ -226,9 +249,6 @@ pub struct Expr<'tcx> {
 
     /// span of the expression in the source
     pub span: Span,
-
-    /// kind of expression
-    pub kind: ExprKind<'tcx>,
 }
 
 #[derive(Clone, Debug, HashStable)]
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index d00b26a5a..6231dd9b6 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -5,6 +5,7 @@
 mod chalk;
 pub mod query;
 pub mod select;
+pub mod solve;
 pub mod specialization_graph;
 mod structural_impls;
 pub mod util;
@@ -18,7 +19,8 @@ use crate::ty::{self, AdtKind, Ty, TyCtxt};
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::DefId;
+use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
 use smallvec::SmallVec;
@@ -36,7 +38,7 @@ pub use self::chalk::{ChalkEnvironmentAndGoal, RustInterner as ChalkRustInterner
 
 /// Depending on the stage of compilation, we want projection to be
 /// more or less conservative.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
 pub enum Reveal {
     /// At type-checking time, we refuse to project any associated
     /// type that is marked `default`. Non-`default` ("final") types
@@ -89,7 +91,8 @@ pub enum Reveal {
 ///
 /// We do not want to intern this as there are a lot of obligation causes which
 /// only live for a short period of time.
-#[derive(Clone, Debug, PartialEq, Eq, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub struct ObligationCause<'tcx> {
     pub span: Span,
 
@@ -99,7 +102,7 @@ pub struct ObligationCause<'tcx> {
     /// (in particular, closures can add new assumptions). See the
     /// field `region_obligations` of the `FulfillmentContext` for more
     /// information.
-    pub body_id: hir::HirId,
+    pub body_id: LocalDefId,
 
     code: InternedObligationCauseCode<'tcx>,
 }
@@ -120,13 +123,13 @@ impl<'tcx> ObligationCause<'tcx> {
     #[inline]
     pub fn new(
         span: Span,
-        body_id: hir::HirId,
+        body_id: LocalDefId,
         code: ObligationCauseCode<'tcx>,
     ) -> ObligationCause<'tcx> {
         ObligationCause { span, body_id, code: code.into() }
     }
 
-    pub fn misc(span: Span, body_id: hir::HirId) -> ObligationCause<'tcx> {
+    pub fn misc(span: Span, body_id: LocalDefId) -> ObligationCause<'tcx> {
         ObligationCause::new(span, body_id, MiscObligation)
     }
 
@@ -137,7 +140,7 @@ impl<'tcx> ObligationCause<'tcx> {
 
     #[inline(always)]
     pub fn dummy_with_span(span: Span) -> ObligationCause<'tcx> {
-        ObligationCause { span, body_id: hir::CRATE_HIR_ID, code: Default::default() }
+        ObligationCause { span, body_id: CRATE_DEF_ID, code: Default::default() }
     }
 
     pub fn span(&self) -> Span {
@@ -196,14 +199,16 @@ impl<'tcx> ObligationCause<'tcx> {
     }
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub struct UnifyReceiverContext<'tcx> {
     pub assoc_item: ty::AssocItem,
     pub param_env: ty::ParamEnv<'tcx>,
     pub substs: SubstsRef<'tcx>,
 }
 
-#[derive(Clone, PartialEq, Eq, Hash, Lift, Default)]
+#[derive(Clone, PartialEq, Eq, Hash, Lift, Default, HashStable)]
+#[derive(TypeVisitable, TypeFoldable, TyEncodable, TyDecodable)]
 pub struct InternedObligationCauseCode<'tcx> {
     /// `None` for `ObligationCauseCode::MiscObligation` (a common case, occurs ~60% of
     /// the time). `Some` otherwise.
@@ -238,7 +243,8 @@ impl<'tcx> std::ops::Deref for InternedObligationCauseCode<'tcx> {
     }
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub enum ObligationCauseCode<'tcx> {
     /// Not well classified or should be obvious from the span.
     MiscObligation,
@@ -446,7 +452,8 @@ pub enum ObligationCauseCode<'tcx> {
 /// This information is used to obtain an `hir::Ty`, which
 /// we can walk in order to obtain precise spans for any
 /// 'nested' types (e.g. `Foo` in `Option<Foo>`).
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub enum WellFormedLoc {
     /// Use the type of the provided definition.
     Ty(LocalDefId),
@@ -463,10 +470,17 @@ pub enum WellFormedLoc {
     },
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub struct ImplDerivedObligationCause<'tcx> {
     pub derived: DerivedObligationCause<'tcx>,
-    pub impl_def_id: DefId,
+    /// The `DefId` of the `impl` that gave rise to the `derived` obligation.
+    /// If the `derived` obligation arose from a trait alias, which conceptually has a synthetic impl,
+    /// then this will be the `DefId` of that trait alias. Care should therefore be taken to handle
+    /// that exceptional case where appropriate.
+    pub impl_or_alias_def_id: DefId,
+    /// The index of the derived predicate in the parent impl's predicates.
+    pub impl_def_predicate_index: Option<usize>,
     pub span: Span,
 }
 
@@ -517,7 +531,8 @@ impl<'tcx> ty::Lift<'tcx> for StatementAsExpression {
     }
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub struct MatchExpressionArmCause<'tcx> {
     pub arm_block_id: Option<hir::HirId>,
     pub arm_ty: Ty<'tcx>,
@@ -533,7 +548,7 @@ pub struct MatchExpressionArmCause<'tcx> {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(Lift, TypeFoldable, TypeVisitable)]
+#[derive(Lift, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
 pub struct IfExpressionCause<'tcx> {
     pub then_id: hir::HirId,
     pub else_id: hir::HirId,
@@ -543,7 +558,8 @@ pub struct IfExpressionCause<'tcx> {
     pub opt_suggest_box_span: Option<Span>,
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift, HashStable, TyEncodable, TyDecodable)]
+#[derive(TypeVisitable, TypeFoldable)]
 pub struct DerivedObligationCause<'tcx> {
     /// The trait predicate of the parent obligation that led to the
     /// current obligation. Note that only trait obligations lead to
diff --git a/compiler/rustc_middle/src/traits/query.rs b/compiler/rustc_middle/src/traits/query.rs
index 615154a55..c4f871875 100644
--- a/compiler/rustc_middle/src/traits/query.rs
+++ b/compiler/rustc_middle/src/traits/query.rs
@@ -14,7 +14,7 @@ use rustc_span::source_map::Span;
 
 pub mod type_op {
     use crate::ty::fold::TypeFoldable;
-    use crate::ty::{Predicate, Ty, UserType};
+    use crate::ty::{Predicate, Ty, TyCtxt, UserType};
     use std::fmt;
 
     #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, Lift)]
@@ -64,7 +64,7 @@ pub mod type_op {
 
     impl<'tcx, T> Normalize<T>
     where
-        T: fmt::Debug + TypeFoldable<'tcx>,
+        T: fmt::Debug + TypeFoldable<TyCtxt<'tcx>>,
     {
         pub fn new(value: T) -> Self {
             Self { value }
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
new file mode 100644
index 000000000..bd43867a3
--- /dev/null
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -0,0 +1,66 @@
+use std::ops::ControlFlow;
+
+use rustc_data_structures::intern::Interned;
+
+use crate::infer::canonical::QueryRegionConstraints;
+use crate::ty::{
+    FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
+};
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
+
+impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
+    type Target = ExternalConstraintsData<'tcx>;
+
+    fn deref(&self) -> &Self::Target {
+        &*self.0
+    }
+}
+
+/// Additional constraints returned on success.
+#[derive(Debug, PartialEq, Eq, Clone, Hash, Default, TypeFoldable, TypeVisitable)]
+pub struct ExternalConstraintsData<'tcx> {
+    // FIXME: implement this.
+    pub region_constraints: QueryRegionConstraints<'tcx>,
+    pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
+}
+
+// FIXME: Having to clone `region_constraints` for folding feels bad and
+// probably isn't great wrt performance.
+//
+// Not sure how to fix this, maybe we should also intern `opaque_types` and
+// `region_constraints` here or something.
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        Ok(FallibleTypeFolder::interner(folder).mk_external_constraints(ExternalConstraintsData {
+            region_constraints: self.region_constraints.clone().try_fold_with(folder)?,
+            opaque_types: self
+                .opaque_types
+                .iter()
+                .map(|opaque| opaque.try_fold_with(folder))
+                .collect::<Result<_, F::Error>>()?,
+        }))
+    }
+
+    fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
+        TypeFolder::interner(folder).mk_external_constraints(ExternalConstraintsData {
+            region_constraints: self.region_constraints.clone().fold_with(folder),
+            opaque_types: self.opaque_types.iter().map(|opaque| opaque.fold_with(folder)).collect(),
+        })
+    }
+}
+
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> std::ops::ControlFlow<V::BreakTy> {
+        self.region_constraints.visit_with(visitor)?;
+        self.opaque_types.visit_with(visitor)?;
+        ControlFlow::Continue(())
+    }
+}
diff --git a/compiler/rustc_middle/src/traits/specialization_graph.rs b/compiler/rustc_middle/src/traits/specialization_graph.rs
index aad5b2fbe..c016f7227 100644
--- a/compiler/rustc_middle/src/traits/specialization_graph.rs
+++ b/compiler/rustc_middle/src/traits/specialization_graph.rs
@@ -1,6 +1,6 @@
 use crate::error::StrictCoherenceNeedsNegativeCoherence;
 use crate::ty::fast_reject::SimplifiedType;
-use crate::ty::visit::TypeVisitable;
+use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{self, TyCtxt};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
@@ -133,11 +133,7 @@ impl Node {
     ///
     /// If this returns `None`, the item can potentially still be found in
     /// parents of this node.
-    pub fn item<'tcx>(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        trait_item_def_id: DefId,
-    ) -> Option<&'tcx ty::AssocItem> {
+    pub fn item<'tcx>(&self, tcx: TyCtxt<'tcx>, trait_item_def_id: DefId) -> Option<ty::AssocItem> {
         match *self {
             Node::Trait(_) => Some(tcx.associated_item(trait_item_def_id)),
             Node::Impl(impl_def_id) => {
@@ -239,7 +235,7 @@ impl<'tcx> Ancestors<'tcx> {
                     }
                 }
 
-                Some(LeafDef { item: *item, defining_node: node, finalizing_node })
+                Some(LeafDef { item, defining_node: node, finalizing_node })
             } else {
                 // Item not mentioned. This "finalizes" any defaulted item provided by an ancestor.
                 finalizing_node = Some(node);
@@ -263,7 +259,7 @@ pub fn ancestors(
 
     if let Some(reported) = specialization_graph.has_errored {
         Err(reported)
-    } else if let Err(reported) = tcx.type_of(start_from_impl).error_reported() {
+    } else if let Err(reported) = tcx.type_of(start_from_impl).subst_identity().error_reported() {
         Err(reported)
     } else {
         Ok(Ancestors {
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index b9c5a4e0d..df9aa765d 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -89,9 +89,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
                 Err(TypeError::Sorts(relate::expected_found(self, a, b)))
             }
 
-            (&ty::Error(guar), _) | (_, &ty::Error(guar)) => {
-                Ok(self.tcx().ty_error_with_guaranteed(guar))
-            }
+            (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(self.tcx().ty_error(guar)),
 
             _ => relate::super_relate_tys(self, a, b),
         }
diff --git a/compiler/rustc_middle/src/ty/abstract_const.rs b/compiler/rustc_middle/src/ty/abstract_const.rs
index 5de758ad9..f889ce827 100644
--- a/compiler/rustc_middle/src/ty/abstract_const.rs
+++ b/compiler/rustc_middle/src/ty/abstract_const.rs
@@ -1,7 +1,7 @@
 //! A subset of a mir body used for const evaluatability checking.
 use crate::ty::{
     self, Const, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitable,
+    TypeVisitableExt,
 };
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
@@ -48,13 +48,13 @@ impl<'tcx> TyCtxt<'tcx> {
         Ok(ac?.map(|ac| EarlyBinder(ac)))
     }
 
-    pub fn expand_abstract_consts<T: TypeFoldable<'tcx>>(self, ac: T) -> T {
+    pub fn expand_abstract_consts<T: TypeFoldable<TyCtxt<'tcx>>>(self, ac: T) -> T {
         struct Expander<'tcx> {
             tcx: TyCtxt<'tcx>,
         }
 
-        impl<'tcx> TypeFolder<'tcx> for Expander<'tcx> {
-            fn tcx(&self) -> TyCtxt<'tcx> {
+        impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Expander<'tcx> {
+            fn interner(&self) -> TyCtxt<'tcx> {
                 self.tcx
             }
             fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index d3d667f68..ec21030b3 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -54,7 +54,7 @@ bitflags! {
 
 /// The definition of a user-defined type, e.g., a `struct`, `enum`, or `union`.
 ///
-/// These are all interned (by `alloc_adt_def`) into the global arena.
+/// These are all interned (by `mk_adt_def`) into the global arena.
 ///
 /// The initialism *ADT* stands for an [*algebraic data type (ADT)*][adt].
 /// This is slightly wrong because `union`s are not ADTs.
@@ -188,7 +188,7 @@ impl<'tcx> AdtDef<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, TyEncodable, TyDecodable)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, HashStable, TyEncodable, TyDecodable)]
 pub enum AdtKind {
     Struct,
     Union,
@@ -406,6 +406,7 @@ impl<'tcx> AdtDef<'tcx> {
     }
 
     /// Return the index of `VariantDef` given a variant id.
+    #[inline]
     pub fn variant_index_with_id(self, vid: DefId) -> VariantIdx {
         self.variants()
             .iter_enumerated()
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index bb7fba3ee..f1a9e50a4 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -79,11 +79,11 @@ impl AssocItem {
                 // late-bound regions, and we don't want method signatures to show up
                 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
                 // regions just fine, showing `fn(&MyType)`.
-                tcx.fn_sig(self.def_id).skip_binder().to_string()
+                tcx.fn_sig(self.def_id).subst_identity().skip_binder().to_string()
             }
             ty::AssocKind::Type => format!("type {};", self.name),
             ty::AssocKind::Const => {
-                format!("const {}: {:?};", self.name, tcx.type_of(self.def_id))
+                format!("const {}: {:?};", self.name, tcx.type_of(self.def_id).subst_identity())
             }
         }
     }
@@ -129,13 +129,13 @@ impl std::fmt::Display for AssocKind {
 /// it is relatively expensive. Instead, items are indexed by `Symbol` and hygienic comparison is
 /// done only on items with the same name.
 #[derive(Debug, Clone, PartialEq, HashStable)]
-pub struct AssocItems<'tcx> {
-    pub(super) items: SortedIndexMultiMap<u32, Symbol, &'tcx ty::AssocItem>,
+pub struct AssocItems {
+    items: SortedIndexMultiMap<u32, Symbol, ty::AssocItem>,
 }
 
-impl<'tcx> AssocItems<'tcx> {
+impl AssocItems {
     /// Constructs an `AssociatedItems` map from a series of `ty::AssocItem`s in definition order.
-    pub fn new(items_in_def_order: impl IntoIterator<Item = &'tcx ty::AssocItem>) -> Self {
+    pub fn new(items_in_def_order: impl IntoIterator<Item = ty::AssocItem>) -> Self {
         let items = items_in_def_order.into_iter().map(|item| (item.name, item)).collect();
         AssocItems { items }
     }
@@ -145,7 +145,7 @@ impl<'tcx> AssocItems<'tcx> {
     /// New code should avoid relying on definition order. If you need a particular associated item
     /// for a known trait, make that trait a lang item instead of indexing this array.
     pub fn in_definition_order(&self) -> impl '_ + Iterator<Item = &ty::AssocItem> {
-        self.items.iter().map(|(_, v)| *v)
+        self.items.iter().map(|(_, v)| v)
     }
 
     pub fn len(&self) -> usize {
@@ -157,7 +157,7 @@ impl<'tcx> AssocItems<'tcx> {
         &self,
         name: Symbol,
     ) -> impl '_ + Iterator<Item = &ty::AssocItem> {
-        self.items.get_by_key(name).copied()
+        self.items.get_by_key(name)
     }
 
     /// Returns the associated item with the given name and `AssocKind`, if one exists.
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index 6ade8935f..dc2bd54b7 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -5,10 +5,10 @@ use crate::{mir, ty};
 
 use std::fmt::Write;
 
-use hir::LangItem;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
-use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::{self as hir, LangItem};
+use rustc_span::symbol::Ident;
 use rustc_span::{Span, Symbol};
 
 use super::{Ty, TyCtxt};
@@ -129,6 +129,9 @@ impl<'tcx> ClosureKind {
 #[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct CapturedPlace<'tcx> {
+    /// Name and span where the binding happens.
+    pub var_ident: Ident,
+
     /// The `Place` that is captured.
     pub place: HirPlace<'tcx>,
 
@@ -148,12 +151,8 @@ impl<'tcx> CapturedPlace<'tcx> {
     }
 
     /// Returns a symbol of the captured upvar, which looks like `name__field1__field2`.
-    fn to_symbol(&self, tcx: TyCtxt<'tcx>) -> Symbol {
-        let hir_id = match self.place.base {
-            HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
-            base => bug!("Expected an upvar, found {:?}", base),
-        };
-        let mut symbol = tcx.hir().name(hir_id).as_str().to_string();
+    pub fn to_symbol(&self) -> Symbol {
+        let mut symbol = self.var_ident.to_string();
 
         let mut ty = self.place.base_ty;
         for proj in self.place.projections.iter() {
@@ -169,11 +168,7 @@ impl<'tcx> CapturedPlace<'tcx> {
                         .unwrap();
                     }
                     ty => {
-                        span_bug!(
-                            self.get_capture_kind_span(tcx),
-                            "Unexpected type {:?} for `Field` projection",
-                            ty
-                        )
+                        bug!("Unexpected type {:?} for `Field` projection", ty)
                     }
                 },
 
@@ -238,10 +233,39 @@ impl<'tcx> CapturedPlace<'tcx> {
     }
 }
 
-fn symbols_for_closure_captures(tcx: TyCtxt<'_>, def_id: (LocalDefId, LocalDefId)) -> Vec<Symbol> {
-    let typeck_results = tcx.typeck(def_id.0);
-    let captures = typeck_results.closure_min_captures_flattened(def_id.1);
-    captures.into_iter().map(|captured_place| captured_place.to_symbol(tcx)).collect()
+#[derive(Copy, Clone, Debug, HashStable)]
+pub struct ClosureTypeInfo<'tcx> {
+    user_provided_sig: ty::CanonicalPolyFnSig<'tcx>,
+    captures: &'tcx [&'tcx ty::CapturedPlace<'tcx>],
+    kind_origin: Option<&'tcx (Span, HirPlace<'tcx>)>,
+}
+
+fn closure_typeinfo<'tcx>(tcx: TyCtxt<'tcx>, def: LocalDefId) -> ClosureTypeInfo<'tcx> {
+    debug_assert!(tcx.is_closure(def.to_def_id()));
+    let typeck_results = tcx.typeck(def);
+    let user_provided_sig = typeck_results.user_provided_sigs[&def];
+    let captures = typeck_results.closure_min_captures_flattened(def);
+    let captures = tcx.arena.alloc_from_iter(captures);
+    let hir_id = tcx.hir().local_def_id_to_hir_id(def);
+    let kind_origin = typeck_results.closure_kind_origins().get(hir_id);
+    ClosureTypeInfo { user_provided_sig, captures, kind_origin }
+}
+
+impl<'tcx> TyCtxt<'tcx> {
+    pub fn closure_kind_origin(self, def_id: LocalDefId) -> Option<&'tcx (Span, HirPlace<'tcx>)> {
+        self.closure_typeinfo(def_id).kind_origin
+    }
+
+    pub fn closure_user_provided_sig(self, def_id: LocalDefId) -> ty::CanonicalPolyFnSig<'tcx> {
+        self.closure_typeinfo(def_id).user_provided_sig
+    }
+
+    pub fn closure_captures(self, def_id: LocalDefId) -> &'tcx [&'tcx ty::CapturedPlace<'tcx>] {
+        if !self.is_closure(def_id.to_def_id()) {
+            return &[];
+        };
+        self.closure_typeinfo(def_id).captures
+    }
 }
 
 /// Return true if the `proj_possible_ancestor` represents an ancestor path
@@ -434,5 +458,5 @@ impl BorrowKind {
 }
 
 pub fn provide(providers: &mut ty::query::Providers) {
-    *providers = ty::query::Providers { symbols_for_closure_captures, ..*providers }
+    *providers = ty::query::Providers { closure_typeinfo, ..*providers }
 }
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 8cc8286c1..3ce80e06a 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -157,6 +157,14 @@ impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AllocId {
     }
 }
 
+impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::ParamEnv<'tcx> {
+    fn encode(&self, e: &mut E) {
+        self.caller_bounds().encode(e);
+        self.reveal().encode(e);
+        self.constness().encode(e);
+    }
+}
+
 #[inline]
 fn decode_arena_allocable<
     'tcx,
@@ -199,7 +207,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for Ty<'tcx> {
             })
         } else {
             let tcx = decoder.interner();
-            tcx.mk_ty(rustc_type_ir::TyKind::decode(decoder))
+            tcx.mk_ty_from_kind(rustc_type_ir::TyKind::decode(decoder))
         }
     }
 }
@@ -236,7 +244,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for SubstsRef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
         let tcx = decoder.interner();
-        tcx.mk_substs(
+        tcx.mk_substs_from_iter(
             (0..len).map::<ty::subst::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
         )
     }
@@ -246,7 +254,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let local: mir::Local = Decodable::decode(decoder);
         let len = decoder.read_usize();
-        let projection = decoder.interner().mk_place_elems(
+        let projection = decoder.interner().mk_place_elems_from_iter(
             (0..len).map::<mir::PlaceElem<'tcx>, _>(|_| Decodable::decode(decoder)),
         );
         mir::Place { local, projection }
@@ -255,16 +263,16 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
 
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Region<'tcx> {
     fn decode(decoder: &mut D) -> Self {
-        decoder.interner().mk_region(Decodable::decode(decoder))
+        decoder.interner().mk_region_from_kind(Decodable::decode(decoder))
     }
 }
 
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for CanonicalVarInfos<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
-        let interned: Vec<CanonicalVarInfo<'tcx>> =
-            (0..len).map(|_| Decodable::decode(decoder)).collect();
-        decoder.interner().intern_canonical_var_infos(interned.as_slice())
+        decoder.interner().mk_canonical_var_infos_from_iter(
+            (0..len).map::<CanonicalVarInfo<'tcx>, _>(|_| Decodable::decode(decoder)),
+        )
     }
 }
 
@@ -280,8 +288,17 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::SymbolName<'tcx>
     }
 }
 
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::ParamEnv<'tcx> {
+    fn decode(d: &mut D) -> Self {
+        let caller_bounds = Decodable::decode(d);
+        let reveal = Decodable::decode(d);
+        let constness = Decodable::decode(d);
+        ty::ParamEnv::new(caller_bounds, reveal, constness)
+    }
+}
+
 macro_rules! impl_decodable_via_ref {
-    ($($t:ty),+) => {
+    ($($t:ty,)+) => {
         $(impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for $t {
             fn decode(decoder: &mut D) -> Self {
                 RefDecodable::decode(decoder)
@@ -293,7 +310,9 @@ macro_rules! impl_decodable_via_ref {
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
-        decoder.interner().mk_type_list((0..len).map::<Ty<'tcx>, _>(|_| Decodable::decode(decoder)))
+        decoder
+            .interner()
+            .mk_type_list_from_iter((0..len).map::<Ty<'tcx>, _>(|_| Decodable::decode(decoder)))
     }
 }
 
@@ -302,7 +321,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
 {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
-        decoder.interner().mk_poly_existential_predicates(
+        decoder.interner().mk_poly_existential_predicates_from_iter(
             (0..len).map::<ty::Binder<'tcx, _>, _>(|_| Decodable::decode(decoder)),
         )
     }
@@ -325,13 +344,13 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [ty::ValTre
 
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ConstAllocation<'tcx> {
     fn decode(decoder: &mut D) -> Self {
-        decoder.interner().intern_const_alloc(Decodable::decode(decoder))
+        decoder.interner().mk_const_alloc(Decodable::decode(decoder))
     }
 }
 
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AdtDef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
-        decoder.interner().intern_adt_def(Decodable::decode(decoder))
+        decoder.interner().mk_adt_def_from_data(Decodable::decode(decoder))
     }
 }
 
@@ -358,7 +377,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
 {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
-        decoder.interner().mk_bound_variable_kinds(
+        decoder.interner().mk_bound_variable_kinds_from_iter(
             (0..len).map::<ty::BoundVariableKind, _>(|_| Decodable::decode(decoder)),
         )
     }
@@ -367,9 +386,18 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty::Const<'tcx>> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
-        decoder
-            .interner()
-            .mk_const_list((0..len).map::<ty::Const<'tcx>, _>(|_| Decodable::decode(decoder)))
+        decoder.interner().mk_const_list_from_iter(
+            (0..len).map::<ty::Const<'tcx>, _>(|_| Decodable::decode(decoder)),
+        )
+    }
+}
+
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty::Predicate<'tcx>> {
+    fn decode(decoder: &mut D) -> &'tcx Self {
+        let len = decoder.read_usize();
+        decoder.interner().mk_predicates_from_iter(
+            (0..len).map::<ty::Predicate<'tcx>, _>(|_| Decodable::decode(decoder)),
+        )
     }
 }
 
@@ -382,7 +410,8 @@ impl_decodable_via_ref! {
     &'tcx mir::UnsafetyCheckResult,
     &'tcx mir::BorrowCheckResult<'tcx>,
     &'tcx mir::coverage::CodeRegion,
-    &'tcx ty::List<ty::BoundVariableKind>
+    &'tcx ty::List<ty::BoundVariableKind>,
+    &'tcx ty::List<ty::Predicate<'tcx>>,
 }
 
 #[macro_export]
@@ -519,6 +548,8 @@ macro_rules! impl_binder_encode_decode {
 impl_binder_encode_decode! {
     &'tcx ty::List<Ty<'tcx>>,
     ty::FnSig<'tcx>,
+    ty::Predicate<'tcx>,
+    ty::TraitPredicate<'tcx>,
     ty::ExistentialPredicate<'tcx>,
     ty::TraitRef<'tcx>,
     Vec<ty::GeneratorInteriorTypeCause<'tcx>>,
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 65cbac3e8..527ec9f6e 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -1,7 +1,9 @@
+use crate::middle::resolve_bound_vars as rbv;
 use crate::mir::interpret::LitToConstInput;
 use crate::ty::{self, DefIdTree, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt};
 use rustc_data_structures::intern::Interned;
 use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_macros::HashStable;
 use std::fmt;
@@ -14,7 +16,7 @@ pub use int::*;
 pub use kind::*;
 pub use valtree::*;
 
-/// Use this rather than `ConstData, whenever possible.
+/// Use this rather than `ConstData`, whenever possible.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
 #[rustc_pass_by_value]
 pub struct Const<'tcx>(pub(super) Interned<'tcx, ConstData<'tcx>>);
@@ -71,7 +73,10 @@ impl<'tcx> Const<'tcx> {
         let expr = &tcx.hir().body(body_id).value;
         debug!(?expr);
 
-        let ty = tcx.type_of(def.def_id_for_type_of());
+        let ty = tcx
+            .type_of(def.def_id_for_type_of())
+            .no_bound_vars()
+            .expect("const parameter types cannot be generic");
 
         match Self::try_eval_lit_or_param(tcx, ty, expr) {
             Some(v) => v,
@@ -125,16 +130,30 @@ impl<'tcx> Const<'tcx> {
             }
         }
 
-        use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath};
         match expr.kind {
-            ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => {
-                // Find the name and index of the const parameter by indexing the generics of
-                // the parent item and construct a `ParamConst`.
-                let item_def_id = tcx.parent(def_id);
-                let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id];
-                let name = tcx.item_name(def_id);
-                Some(tcx.mk_const(ty::ParamConst::new(index, name), ty))
+            hir::ExprKind::Path(hir::QPath::Resolved(
+                _,
+                &hir::Path { res: Res::Def(DefKind::ConstParam, def_id), .. },
+            )) => {
+                match tcx.named_bound_var(expr.hir_id) {
+                    Some(rbv::ResolvedArg::EarlyBound(_)) => {
+                        // Find the name and index of the const parameter by indexing the generics of
+                        // the parent item and construct a `ParamConst`.
+                        let item_def_id = tcx.parent(def_id);
+                        let generics = tcx.generics_of(item_def_id);
+                        let index = generics.param_def_id_to_index[&def_id];
+                        let name = tcx.item_name(def_id);
+                        Some(tcx.mk_const(ty::ParamConst::new(index, name), ty))
+                    }
+                    Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => Some(tcx.mk_const(
+                        ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
+                        ty,
+                    )),
+                    Some(rbv::ResolvedArg::Error(guar)) => {
+                        Some(tcx.const_error_with_guaranteed(ty, guar))
+                    }
+                    arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
+                }
             }
             _ => None,
         }
@@ -175,7 +194,7 @@ impl<'tcx> Const<'tcx> {
 
     #[inline]
     /// Creates an interned usize constant.
-    pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self {
+    pub fn from_target_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self {
         Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize))
     }
 
@@ -201,8 +220,12 @@ impl<'tcx> Const<'tcx> {
     }
 
     #[inline]
-    pub fn try_eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> {
-        self.kind().eval(tcx, param_env).try_to_machine_usize(tcx)
+    pub fn try_eval_target_usize(
+        self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+    ) -> Option<u64> {
+        self.kind().eval(tcx, param_env).try_to_target_usize(tcx)
     }
 
     #[inline]
@@ -229,8 +252,8 @@ impl<'tcx> Const<'tcx> {
 
     #[inline]
     /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`.
-    pub fn eval_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
-        self.try_eval_usize(tcx, param_env)
+    pub fn eval_target_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
+        self.try_eval_target_usize(tcx, param_env)
             .unwrap_or_else(|| bug!("expected usize, got {:#?}", self))
     }
 
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index 48958e0d9..eecd78ab6 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -232,7 +232,7 @@ impl ScalarInt {
     }
 
     #[inline]
-    pub fn try_to_machine_usize(&self, tcx: TyCtxt<'_>) -> Result<u64, Size> {
+    pub fn try_to_target_usize(&self, tcx: TyCtxt<'_>) -> Result<u64, Size> {
         Ok(self.to_bits(tcx.data_layout.pointer_size)? as u64)
     }
 
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index d9721863a..560caa041 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -4,7 +4,7 @@ use crate::mir::interpret::{AllocId, ConstValue, Scalar};
 use crate::ty::abstract_const::CastKind;
 use crate::ty::subst::{InternalSubsts, SubstsRef};
 use crate::ty::ParamEnv;
-use crate::ty::{self, List, Ty, TyCtxt, TypeVisitable};
+use crate::ty::{self, List, Ty, TyCtxt, TypeVisitableExt};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
@@ -125,8 +125,8 @@ impl<'tcx> ConstKind<'tcx> {
     }
 
     #[inline]
-    pub fn try_to_machine_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
-        self.try_to_value()?.try_to_machine_usize(tcx)
+    pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
+        self.try_to_value()?.try_to_target_usize(tcx)
     }
 }
 
@@ -217,23 +217,21 @@ impl<'tcx> ConstKind<'tcx> {
             // Note that we erase regions *before* calling `with_reveal_all_normalized`,
             // so that we don't try to invoke this query with
             // any region variables.
-            let param_env_and = tcx
-                .erase_regions(param_env)
-                .with_reveal_all_normalized(tcx)
-                .and(tcx.erase_regions(unevaluated));
 
             // HACK(eddyb) when the query key would contain inference variables,
             // attempt using identity substs and `ParamEnv` instead, that will succeed
             // when the expression doesn't depend on any parameters.
             // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
             // we can call `infcx.const_eval_resolve` which handles inference variables.
-            let param_env_and = if param_env_and.needs_infer() {
+            let param_env_and = if (param_env, unevaluated).has_non_region_infer() {
                 tcx.param_env(unevaluated.def.did).and(ty::UnevaluatedConst {
                     def: unevaluated.def,
                     substs: InternalSubsts::identity_for_item(tcx, unevaluated.def.did),
                 })
             } else {
-                param_env_and
+                tcx.erase_regions(param_env)
+                    .with_reveal_all_normalized(tcx)
+                    .and(tcx.erase_regions(unevaluated))
             };
 
             // FIXME(eddyb) maybe the `const_eval_*` methods should take
diff --git a/compiler/rustc_middle/src/ty/consts/valtree.rs b/compiler/rustc_middle/src/ty/consts/valtree.rs
index a803fca0d..5ed4af2e9 100644
--- a/compiler/rustc_middle/src/ty/consts/valtree.rs
+++ b/compiler/rustc_middle/src/ty/consts/valtree.rs
@@ -78,8 +78,8 @@ impl<'tcx> ValTree<'tcx> {
         }
     }
 
-    pub fn try_to_machine_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
-        self.try_to_scalar_int().map(|s| s.try_to_machine_usize(tcx).ok()).flatten()
+    pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
+        self.try_to_scalar_int().map(|s| s.try_to_target_usize(tcx).ok()).flatten()
     }
 
     /// Get the values inside the ValTree as a slice of bytes. This only works for
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index ce04d8d21..d9af2fd74 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2,12 +2,14 @@
 
 #![allow(rustc::usage_of_ty_tykind)]
 
+pub mod tls;
+
 use crate::arena::Arena;
 use crate::dep_graph::{DepGraph, DepKindStruct};
-use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
+use crate::infer::canonical::CanonicalVarInfo;
 use crate::lint::struct_lint_level;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
-use crate::middle::resolve_lifetime;
+use crate::middle::resolve_bound_vars;
 use crate::middle::stability;
 use crate::mir::interpret::{self, Allocation, ConstAllocation};
 use crate::mir::{
@@ -15,6 +17,7 @@ use crate::mir::{
 };
 use crate::thir::Thir;
 use crate::traits;
+use crate::traits::solve::{ExternalConstraints, ExternalConstraintsData};
 use crate::ty::query::{self, TyCtxtAt};
 use crate::ty::{
     self, AdtDef, AdtDefData, AdtKind, Binder, Const, ConstData, DefIdTree, FloatTy, FloatVar,
@@ -33,7 +36,7 @@ use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
-use rustc_data_structures::sync::{self, Lock, Lrc, ReadGuard, WorkerLocal};
+use rustc_data_structures::sync::{self, Lock, Lrc, MappedReadGuard, ReadGuard, WorkerLocal};
 use rustc_errors::{
     DecorateLint, DiagnosticBuilder, DiagnosticMessage, ErrorGuaranteed, MultiSpan,
 };
@@ -64,7 +67,7 @@ use rustc_target::abi::{Layout, LayoutS, TargetDataLayout, VariantIdx};
 use rustc_target::spec::abi;
 use rustc_type_ir::sty::TyKind::*;
 use rustc_type_ir::WithCachedTypeInfo;
-use rustc_type_ir::{DynKind, InternAs, InternIteratorElement, Interner, TypeFlags};
+use rustc_type_ir::{CollectAndApply, DynKind, Interner, TypeFlags};
 
 use std::any::Any;
 use std::borrow::Borrow;
@@ -75,6 +78,8 @@ use std::iter;
 use std::mem;
 use std::ops::{Bound, Deref};
 
+const TINY_CONST_EVAL_LIMIT: Limit = Limit(20);
+
 pub trait OnDiskCache<'tcx>: rustc_data_structures::sync::Sync {
     /// Creates a new `OnDiskCache` instance from the serialized data in `data`.
     fn new(sess: &'tcx Session, data: Mmap, start_pos: usize) -> Self
@@ -95,9 +100,11 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     type AdtDef = ty::AdtDef<'tcx>;
     type SubstsRef = ty::SubstsRef<'tcx>;
     type DefId = DefId;
+    type Binder<T> = Binder<'tcx, T>;
     type Ty = Ty<'tcx>;
     type Const = ty::Const<'tcx>;
     type Region = Region<'tcx>;
+    type Predicate = Predicate<'tcx>;
     type TypeAndMut = TypeAndMut<'tcx>;
     type Mutability = hir::Mutability;
     type Movability = hir::Movability;
@@ -142,8 +149,9 @@ pub struct CtxtInterners<'tcx> {
     const_: InternedSet<'tcx, ConstData<'tcx>>,
     const_allocation: InternedSet<'tcx, Allocation>,
     bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
-    layout: InternedSet<'tcx, LayoutS<VariantIdx>>,
+    layout: InternedSet<'tcx, LayoutS>,
     adt_def: InternedSet<'tcx, AdtDefData>,
+    external_constraints: InternedSet<'tcx, ExternalConstraintsData<'tcx>>,
 }
 
 impl<'tcx> CtxtInterners<'tcx> {
@@ -165,10 +173,11 @@ impl<'tcx> CtxtInterners<'tcx> {
             bound_variable_kinds: Default::default(),
             layout: Default::default(),
             adt_def: Default::default(),
+            external_constraints: Default::default(),
         }
     }
 
-    /// Interns a type.
+    /// Interns a type. (Use `mk_*` functions instead, where possible.)
     #[allow(rustc::usage_of_ty_tykind)]
     #[inline(never)]
     fn intern_ty(&self, kind: TyKind<'tcx>, sess: &Session, untracked: &Untracked) -> Ty<'tcx> {
@@ -208,6 +217,7 @@ impl<'tcx> CtxtInterners<'tcx> {
         }
     }
 
+    /// Interns a predicate. (Use `mk_predicate` instead, where possible.)
     #[inline(never)]
     fn intern_predicate(
         &self,
@@ -234,6 +244,20 @@ impl<'tcx> CtxtInterners<'tcx> {
     }
 }
 
+// For these preinterned values, an alternative would be to have
+// variable-length vectors that grow as needed. But that turned out to be
+// slightly more complex and no faster.
+
+const NUM_PREINTERNED_TY_VARS: u32 = 100;
+const NUM_PREINTERNED_FRESH_TYS: u32 = 20;
+const NUM_PREINTERNED_FRESH_INT_TYS: u32 = 3;
+const NUM_PREINTERNED_FRESH_FLOAT_TYS: u32 = 3;
+
+// This number may seem high, but it is reached in all but the smallest crates.
+const NUM_PREINTERNED_RE_VARS: u32 = 500;
+const NUM_PREINTERNED_RE_LATE_BOUNDS_I: u32 = 2;
+const NUM_PREINTERNED_RE_LATE_BOUNDS_V: u32 = 20;
+
 pub struct CommonTypes<'tcx> {
     pub unit: Ty<'tcx>,
     pub bool: Ty<'tcx>,
@@ -259,7 +283,20 @@ pub struct CommonTypes<'tcx> {
     /// Dummy type used for the `Self` of a `TraitRef` created for converting
     /// a trait object, and which gets removed in `ExistentialTraitRef`.
     /// This type must not appear anywhere in other converted types.
+    /// `Infer(ty::FreshTy(0))` does the job.
     pub trait_object_dummy_self: Ty<'tcx>,
+
+    /// Pre-interned `Infer(ty::TyVar(n))` for small values of `n`.
+    pub ty_vars: Vec<Ty<'tcx>>,
+
+    /// Pre-interned `Infer(ty::FreshTy(n))` for small values of `n`.
+    pub fresh_tys: Vec<Ty<'tcx>>,
+
+    /// Pre-interned `Infer(ty::FreshIntTy(n))` for small values of `n`.
+    pub fresh_int_tys: Vec<Ty<'tcx>>,
+
+    /// Pre-interned `Infer(ty::FreshFloatTy(n))` for small values of `n`.
+    pub fresh_float_tys: Vec<Ty<'tcx>>,
 }
 
 pub struct CommonLifetimes<'tcx> {
@@ -268,6 +305,14 @@ pub struct CommonLifetimes<'tcx> {
 
     /// Erased region, used outside of type inference.
     pub re_erased: Region<'tcx>,
+
+    /// Pre-interned `ReVar(ty::RegionVar(n))` for small values of `n`.
+    pub re_vars: Vec<Region<'tcx>>,
+
+    /// Pre-interned values of the form:
+    /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(v, None) })`
+    /// for small values of `i` and `v`.
+    pub re_late_bounds: Vec<Vec<Region<'tcx>>>,
 }
 
 pub struct CommonConsts<'tcx> {
@@ -282,6 +327,15 @@ impl<'tcx> CommonTypes<'tcx> {
     ) -> CommonTypes<'tcx> {
         let mk = |ty| interners.intern_ty(ty, sess, untracked);
 
+        let ty_vars =
+            (0..NUM_PREINTERNED_TY_VARS).map(|n| mk(Infer(ty::TyVar(TyVid::from(n))))).collect();
+        let fresh_tys: Vec<_> =
+            (0..NUM_PREINTERNED_FRESH_TYS).map(|n| mk(Infer(ty::FreshTy(n)))).collect();
+        let fresh_int_tys: Vec<_> =
+            (0..NUM_PREINTERNED_FRESH_INT_TYS).map(|n| mk(Infer(ty::FreshIntTy(n)))).collect();
+        let fresh_float_tys: Vec<_> =
+            (0..NUM_PREINTERNED_FRESH_FLOAT_TYS).map(|n| mk(Infer(ty::FreshFloatTy(n)))).collect();
+
         CommonTypes {
             unit: mk(Tuple(List::empty())),
             bool: mk(Bool),
@@ -304,7 +358,12 @@ impl<'tcx> CommonTypes<'tcx> {
             str_: mk(Str),
             self_param: mk(ty::Param(ty::ParamTy { index: 0, name: kw::SelfUpper })),
 
-            trait_object_dummy_self: mk(Infer(ty::FreshTy(0))),
+            trait_object_dummy_self: fresh_tys[0],
+
+            ty_vars,
+            fresh_tys,
+            fresh_int_tys,
+            fresh_float_tys,
         }
     }
 }
@@ -317,7 +376,31 @@ impl<'tcx> CommonLifetimes<'tcx> {
             ))
         };
 
-        CommonLifetimes { re_static: mk(ty::ReStatic), re_erased: mk(ty::ReErased) }
+        let re_vars =
+            (0..NUM_PREINTERNED_RE_VARS).map(|n| mk(ty::ReVar(ty::RegionVid::from(n)))).collect();
+
+        let re_late_bounds = (0..NUM_PREINTERNED_RE_LATE_BOUNDS_I)
+            .map(|i| {
+                (0..NUM_PREINTERNED_RE_LATE_BOUNDS_V)
+                    .map(|v| {
+                        mk(ty::ReLateBound(
+                            ty::DebruijnIndex::from(i),
+                            ty::BoundRegion {
+                                var: ty::BoundVar::from(v),
+                                kind: ty::BrAnon(v, None),
+                            },
+                        ))
+                    })
+                    .collect()
+            })
+            .collect();
+
+        CommonLifetimes {
+            re_static: mk(ty::ReStatic),
+            re_erased: mk(ty::ReErased),
+            re_vars,
+            re_late_bounds,
+        }
     }
 }
 
@@ -438,7 +521,7 @@ pub struct GlobalCtxt<'tcx> {
     pub on_disk_cache: Option<&'tcx dyn OnDiskCache<'tcx>>,
 
     pub queries: &'tcx dyn query::QueryEngine<'tcx>,
-    pub query_caches: query::QueryCaches<'tcx>,
+    pub query_system: query::QuerySystem<'tcx>,
     pub(crate) query_kinds: &'tcx [DepKindStruct<'tcx>],
 
     // Internal caches for metadata decoding. No need to track deps on this.
@@ -461,6 +544,18 @@ pub struct GlobalCtxt<'tcx> {
     pub(crate) alloc_map: Lock<interpret::AllocMap<'tcx>>,
 }
 
+impl<'tcx> GlobalCtxt<'tcx> {
+    /// Installs `self` in a `TyCtxt` and `ImplicitCtxt` for the duration of
+    /// `f`.
+    pub fn enter<'a: 'tcx, F, R>(&'a self, f: F) -> R
+    where
+        F: FnOnce(TyCtxt<'tcx>) -> R,
+    {
+        let icx = tls::ImplicitCtxt::new(self);
+        tls::enter_context(&icx, || f(icx.tcx))
+    }
+}
+
 impl<'tcx> TyCtxt<'tcx> {
     /// Expects a body and returns its codegen attributes.
     ///
@@ -521,21 +616,21 @@ impl<'tcx> TyCtxt<'tcx> {
         self.arena.alloc(Steal::new(promoted))
     }
 
-    pub fn alloc_adt_def(
+    pub fn mk_adt_def(
         self,
         did: DefId,
         kind: AdtKind,
         variants: IndexVec<VariantIdx, ty::VariantDef>,
         repr: ReprOptions,
     ) -> ty::AdtDef<'tcx> {
-        self.intern_adt_def(ty::AdtDefData::new(self, did, kind, variants, repr))
+        self.mk_adt_def_from_data(ty::AdtDefData::new(self, did, kind, variants, repr))
     }
 
     /// Allocates a read-only byte or string literal for `mir::interpret`.
     pub fn allocate_bytes(self, bytes: &[u8]) -> interpret::AllocId {
         // Create an allocation that just contains these bytes.
         let alloc = interpret::Allocation::from_bytes_byte_aligned_immutable(bytes);
-        let alloc = self.intern_const_alloc(alloc);
+        let alloc = self.mk_const_alloc(alloc);
         self.create_memory_alloc(alloc)
     }
 
@@ -611,7 +706,7 @@ impl<'tcx> TyCtxt<'tcx> {
             untracked,
             on_disk_cache,
             queries,
-            query_caches: query::QueryCaches::default(),
+            query_system: Default::default(),
             query_kinds,
             ty_rcache: Default::default(),
             pred_rcache: Default::default(),
@@ -624,13 +719,13 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Constructs a `TyKind::Error` type with current `ErrorGuaranteed`
     #[track_caller]
-    pub fn ty_error_with_guaranteed(self, reported: ErrorGuaranteed) -> Ty<'tcx> {
-        self.mk_ty(Error(reported))
+    pub fn ty_error(self, reported: ErrorGuaranteed) -> Ty<'tcx> {
+        self.mk_ty_from_kind(Error(reported))
     }
 
     /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
     #[track_caller]
-    pub fn ty_error(self) -> Ty<'tcx> {
+    pub fn ty_error_misc(self) -> Ty<'tcx> {
         self.ty_error_with_message(DUMMY_SP, "TyKind::Error constructed but no error reported")
     }
 
@@ -639,7 +734,31 @@ impl<'tcx> TyCtxt<'tcx> {
     #[track_caller]
     pub fn ty_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Ty<'tcx> {
         let reported = self.sess.delay_span_bug(span, msg);
-        self.mk_ty(Error(reported))
+        self.mk_ty_from_kind(Error(reported))
+    }
+
+    /// Constructs a `RegionKind::ReError` lifetime.
+    #[track_caller]
+    pub fn mk_re_error(self, reported: ErrorGuaranteed) -> Region<'tcx> {
+        self.intern_region(ty::ReError(reported))
+    }
+
+    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` to ensure it
+    /// gets used.
+    #[track_caller]
+    pub fn mk_re_error_misc(self) -> Region<'tcx> {
+        self.mk_re_error_with_message(
+            DUMMY_SP,
+            "RegionKind::ReError constructed but no error reported",
+        )
+    }
+
+    /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` with the given
+    /// `msg` to ensure it gets used.
+    #[track_caller]
+    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Region<'tcx> {
+        let reported = self.sess.delay_span_bug(span, msg);
+        self.mk_re_error(reported)
     }
 
     /// Like [TyCtxt::ty_error] but for constants, with current `ErrorGuaranteed`
@@ -675,8 +794,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn consider_optimizing<T: Fn() -> String>(self, msg: T) -> bool {
-        let cname = self.crate_name(LOCAL_CRATE);
-        self.sess.consider_optimizing(cname.as_str(), msg)
+        self.sess.consider_optimizing(|| self.crate_name(LOCAL_CRATE), msg)
     }
 
     /// Obtain all lang items of this crate and all dependencies (recursively)
@@ -718,7 +836,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if let Some(id) = id.as_local() {
             self.definitions_untracked().def_key(id)
         } else {
-            self.untracked.cstore.def_key(id)
+            self.cstore_untracked().def_key(id)
         }
     }
 
@@ -732,7 +850,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if let Some(id) = id.as_local() {
             self.definitions_untracked().def_path(id)
         } else {
-            self.untracked.cstore.def_path(id)
+            self.cstore_untracked().def_path(id)
         }
     }
 
@@ -742,7 +860,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if let Some(def_id) = def_id.as_local() {
             self.definitions_untracked().def_path_hash(def_id)
         } else {
-            self.untracked.cstore.def_path_hash(def_id)
+            self.cstore_untracked().def_path_hash(def_id)
         }
     }
 
@@ -751,7 +869,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if crate_num == LOCAL_CRATE {
             self.sess.local_stable_crate_id()
         } else {
-            self.untracked.cstore.stable_crate_id(crate_num)
+            self.cstore_untracked().stable_crate_id(crate_num)
         }
     }
 
@@ -762,7 +880,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if stable_crate_id == self.sess.local_stable_crate_id() {
             LOCAL_CRATE
         } else {
-            self.untracked.cstore.stable_crate_id_to_crate_num(stable_crate_id)
+            self.cstore_untracked().stable_crate_id_to_crate_num(stable_crate_id)
         }
     }
 
@@ -781,7 +899,7 @@ impl<'tcx> TyCtxt<'tcx> {
         } else {
             // If this is a DefPathHash from an upstream crate, let the CrateStore map
             // it to a DefId.
-            let cstore = &*self.untracked.cstore;
+            let cstore = &*self.cstore_untracked();
             let cnum = cstore.stable_crate_id_to_crate_num(stable_crate_id);
             cstore.def_path_hash_to_def_id(cnum, hash)
         }
@@ -795,7 +913,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let (crate_name, stable_crate_id) = if def_id.is_local() {
             (self.crate_name(LOCAL_CRATE), self.sess.local_stable_crate_id())
         } else {
-            let cstore = &*self.untracked.cstore;
+            let cstore = &*self.cstore_untracked();
             (cstore.crate_name(def_id.krate), cstore.stable_crate_id(def_id.krate))
         };
 
@@ -893,10 +1011,15 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Note that this is *untracked* and should only be used within the query
     /// system if the result is otherwise tracked through queries
-    pub fn cstore_untracked(self) -> &'tcx CrateStoreDyn {
-        &*self.untracked.cstore
+    #[inline]
+    pub fn cstore_untracked(self) -> MappedReadGuard<'tcx, CrateStoreDyn> {
+        ReadGuard::map(self.untracked.cstore.read(), |c| &**c)
     }
 
+    /// Give out access to the untracked data without any sanity checks.
+    pub fn untracked(self) -> &'tcx Untracked {
+        &self.untracked
+    }
     /// Note that this is *untracked* and should only be used within the query
     /// system if the result is otherwise tracked through queries
     #[inline]
@@ -908,7 +1031,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// system if the result is otherwise tracked through queries
     #[inline]
     pub fn source_span_untracked(self, def_id: LocalDefId) -> Span {
-        self.untracked.source_span.get(def_id).copied().unwrap_or(DUMMY_SP)
+        self.untracked.source_span.get(def_id).unwrap_or(DUMMY_SP)
     }
 
     #[inline(always)]
@@ -997,6 +1120,30 @@ impl<'tcx> TyCtxt<'tcx> {
         v.0
     }
 
+    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in its return type and associated alias span when type alias is used
+    pub fn return_type_impl_or_dyn_traits_with_type_alias(
+        self,
+        scope_def_id: LocalDefId,
+    ) -> Option<(Vec<&'tcx hir::Ty<'tcx>>, Span)> {
+        let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
+        let mut v = TraitObjectVisitor(vec![], self.hir());
+        // when the return type is a type alias
+        if let Some(hir::FnDecl { output: hir::FnRetTy::Return(hir_output), .. }) = self.hir().fn_decl_by_hir_id(hir_id)
+            && let hir::TyKind::Path(hir::QPath::Resolved(
+                None,
+                hir::Path { res: hir::def::Res::Def(DefKind::TyAlias, def_id), .. }, )) = hir_output.kind
+            && let Some(local_id) = def_id.as_local()
+            && let Some(alias_ty) = self.hir().get_by_def_id(local_id).alias_ty() // it is type alias
+            && let Some(alias_generics) = self.hir().get_by_def_id(local_id).generics()
+        {
+            v.visit_ty(alias_ty);
+            if !v.0.is_empty() {
+                return Some((v.0, alias_generics.span));
+            }
+        }
+        return None;
+    }
+
     pub fn return_type_impl_trait(self, scope_def_id: LocalDefId) -> Option<(Ty<'tcx>, Span)> {
         // `type_of()` will fail on these (#55796, #86483), so only allow `fn`s or closures.
         match self.hir().get_by_def_id(scope_def_id) {
@@ -1007,18 +1154,16 @@ impl<'tcx> TyCtxt<'tcx> {
             _ => return None,
         }
 
-        let ret_ty = self.type_of(scope_def_id);
+        let ret_ty = self.type_of(scope_def_id).subst_identity();
         match ret_ty.kind() {
             ty::FnDef(_, _) => {
                 let sig = ret_ty.fn_sig(self);
                 let output = self.erase_late_bound_regions(sig.output());
-                if output.is_impl_trait() {
+                output.is_impl_trait().then(|| {
                     let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
                     let fn_decl = self.hir().fn_decl_by_hir_id(hir_id).unwrap();
-                    Some((output, fn_decl.output.span()))
-                } else {
-                    None
-                }
+                    (output, fn_decl.output.span())
+                })
             }
             _ => None,
         }
@@ -1049,20 +1194,15 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn caller_location_ty(self) -> Ty<'tcx> {
         self.mk_imm_ref(
             self.lifetimes.re_static,
-            self.bound_type_of(self.require_lang_item(LangItem::PanicLocation, None))
-                .subst(self, self.mk_substs([self.lifetimes.re_static.into()].iter())),
+            self.type_of(self.require_lang_item(LangItem::PanicLocation, None))
+                .subst(self, self.mk_substs(&[self.lifetimes.re_static.into()])),
         )
     }
 
     /// Returns a displayable description and article for the given `def_id` (e.g. `("a", "struct")`).
     pub fn article_and_description(self, def_id: DefId) -> (&'static str, &'static str) {
-        match self.def_kind(def_id) {
-            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
-                rustc_hir::GeneratorKind::Async(..) => ("an", "async closure"),
-                rustc_hir::GeneratorKind::Gen => ("a", "generator"),
-            },
-            def_kind => (def_kind.article(), def_kind.descr(def_id)),
-        }
+        let kind = self.def_kind(def_id);
+        (self.def_kind_descr_article(kind, def_id), self.def_kind_descr(kind, def_id))
     }
 
     pub fn type_length_limit(self) -> Limit {
@@ -1078,7 +1218,11 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn const_eval_limit(self) -> Limit {
-        self.limits(()).const_eval_limit
+        if self.sess.opts.unstable_opts.tiny_const_eval_limit {
+            TINY_CONST_EVAL_LIMIT
+        } else {
+            self.limits(()).const_eval_limit
+        }
     }
 
     pub fn all_traits(self) -> impl Iterator<Item = DefId> + 'tcx {
@@ -1120,13 +1264,12 @@ macro_rules! nop_lift {
         impl<'a, 'tcx> Lift<'tcx> for $ty {
             type Lifted = $lifted;
             fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
-                if tcx.interners.$set.contains_pointer_to(&InternedInSet(&*self.0.0)) {
+                tcx.interners
+                    .$set
+                    .contains_pointer_to(&InternedInSet(&*self.0.0))
                     // SAFETY: `self` is interned and therefore valid
                     // for the entire lifetime of the `TyCtxt`.
-                    Some(unsafe { mem::transmute(self) })
-                } else {
-                    None
-                }
+                    .then(|| unsafe { mem::transmute(self) })
             }
         }
     };
@@ -1134,20 +1277,20 @@ macro_rules! nop_lift {
 
 // Can't use the macros as we have reuse the `substs` here.
 //
-// See `intern_type_list` for more info.
+// See `mk_type_list` for more info.
 impl<'a, 'tcx> Lift<'tcx> for &'a List<Ty<'a>> {
     type Lifted = &'tcx List<Ty<'tcx>>;
     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
         if self.is_empty() {
             return Some(List::empty());
         }
-        if tcx.interners.substs.contains_pointer_to(&InternedInSet(self.as_substs())) {
+
+        tcx.interners
+            .substs
+            .contains_pointer_to(&InternedInSet(self.as_substs()))
             // SAFETY: `self` is interned and therefore valid
             // for the entire lifetime of the `TyCtxt`.
-            Some(unsafe { mem::transmute::<&'a List<Ty<'a>>, &'tcx List<Ty<'tcx>>>(self) })
-        } else {
-            None
-        }
+            .then(|| unsafe { mem::transmute::<&'a List<Ty<'a>>, &'tcx List<Ty<'tcx>>>(self) })
     }
 }
 
@@ -1159,11 +1302,10 @@ macro_rules! nop_list_lift {
                 if self.is_empty() {
                     return Some(List::empty());
                 }
-                if tcx.interners.$set.contains_pointer_to(&InternedInSet(self)) {
-                    Some(unsafe { mem::transmute(self) })
-                } else {
-                    None
-                }
+                tcx.interners
+                    .$set
+                    .contains_pointer_to(&InternedInSet(self))
+                    .then(|| unsafe { mem::transmute(self) })
             }
         }
     };
@@ -1188,178 +1330,6 @@ CloneLiftImpls! { for<'tcx> {
     Constness, traits::WellFormedLoc, ImplPolarity, crate::mir::ReturnConstraint,
 } }
 
-pub mod tls {
-    use super::{ptr_eq, GlobalCtxt, TyCtxt};
-
-    use crate::dep_graph::TaskDepsRef;
-    use crate::ty::query;
-    use rustc_data_structures::sync::{self, Lock};
-    use rustc_errors::Diagnostic;
-    use std::mem;
-    use thin_vec::ThinVec;
-
-    #[cfg(not(parallel_compiler))]
-    use std::cell::Cell;
-
-    #[cfg(parallel_compiler)]
-    use rustc_rayon_core as rayon_core;
-
-    /// This is the implicit state of rustc. It contains the current
-    /// `TyCtxt` and query. It is updated when creating a local interner or
-    /// executing a new query. Whenever there's a `TyCtxt` value available
-    /// you should also have access to an `ImplicitCtxt` through the functions
-    /// in this module.
-    #[derive(Clone)]
-    pub struct ImplicitCtxt<'a, 'tcx> {
-        /// The current `TyCtxt`.
-        pub tcx: TyCtxt<'tcx>,
-
-        /// The current query job, if any. This is updated by `JobOwner::start` in
-        /// `ty::query::plumbing` when executing a query.
-        pub query: Option<query::QueryJobId>,
-
-        /// Where to store diagnostics for the current query job, if any.
-        /// This is updated by `JobOwner::start` in `ty::query::plumbing` when executing a query.
-        pub diagnostics: Option<&'a Lock<ThinVec<Diagnostic>>>,
-
-        /// Used to prevent queries from calling too deeply.
-        pub query_depth: usize,
-
-        /// The current dep graph task. This is used to add dependencies to queries
-        /// when executing them.
-        pub task_deps: TaskDepsRef<'a>,
-    }
-
-    impl<'a, 'tcx> ImplicitCtxt<'a, 'tcx> {
-        pub fn new(gcx: &'tcx GlobalCtxt<'tcx>) -> Self {
-            let tcx = TyCtxt { gcx };
-            ImplicitCtxt {
-                tcx,
-                query: None,
-                diagnostics: None,
-                query_depth: 0,
-                task_deps: TaskDepsRef::Ignore,
-            }
-        }
-    }
-
-    /// Sets Rayon's thread-local variable, which is preserved for Rayon jobs
-    /// to `value` during the call to `f`. It is restored to its previous value after.
-    /// This is used to set the pointer to the new `ImplicitCtxt`.
-    #[cfg(parallel_compiler)]
-    #[inline]
-    fn set_tlv<F: FnOnce() -> R, R>(value: usize, f: F) -> R {
-        rayon_core::tlv::with(value, f)
-    }
-
-    /// Gets Rayon's thread-local variable, which is preserved for Rayon jobs.
-    /// This is used to get the pointer to the current `ImplicitCtxt`.
-    #[cfg(parallel_compiler)]
-    #[inline]
-    pub fn get_tlv() -> usize {
-        rayon_core::tlv::get()
-    }
-
-    #[cfg(not(parallel_compiler))]
-    thread_local! {
-        /// A thread local variable that stores a pointer to the current `ImplicitCtxt`.
-        static TLV: Cell<usize> = const { Cell::new(0) };
-    }
-
-    /// Sets TLV to `value` during the call to `f`.
-    /// It is restored to its previous value after.
-    /// This is used to set the pointer to the new `ImplicitCtxt`.
-    #[cfg(not(parallel_compiler))]
-    #[inline]
-    fn set_tlv<F: FnOnce() -> R, R>(value: usize, f: F) -> R {
-        let old = get_tlv();
-        let _reset = rustc_data_structures::OnDrop(move || TLV.with(|tlv| tlv.set(old)));
-        TLV.with(|tlv| tlv.set(value));
-        f()
-    }
-
-    /// Gets the pointer to the current `ImplicitCtxt`.
-    #[cfg(not(parallel_compiler))]
-    #[inline]
-    fn get_tlv() -> usize {
-        TLV.with(|tlv| tlv.get())
-    }
-
-    /// Sets `context` as the new current `ImplicitCtxt` for the duration of the function `f`.
-    #[inline]
-    pub fn enter_context<'a, 'tcx, F, R>(context: &ImplicitCtxt<'a, 'tcx>, f: F) -> R
-    where
-        F: FnOnce(&ImplicitCtxt<'a, 'tcx>) -> R,
-    {
-        set_tlv(context as *const _ as usize, || f(&context))
-    }
-
-    /// Allows access to the current `ImplicitCtxt` in a closure if one is available.
-    #[inline]
-    pub fn with_context_opt<F, R>(f: F) -> R
-    where
-        F: for<'a, 'tcx> FnOnce(Option<&ImplicitCtxt<'a, 'tcx>>) -> R,
-    {
-        let context = get_tlv();
-        if context == 0 {
-            f(None)
-        } else {
-            // We could get an `ImplicitCtxt` pointer from another thread.
-            // Ensure that `ImplicitCtxt` is `Sync`.
-            sync::assert_sync::<ImplicitCtxt<'_, '_>>();
-
-            unsafe { f(Some(&*(context as *const ImplicitCtxt<'_, '_>))) }
-        }
-    }
-
-    /// Allows access to the current `ImplicitCtxt`.
-    /// Panics if there is no `ImplicitCtxt` available.
-    #[inline]
-    pub fn with_context<F, R>(f: F) -> R
-    where
-        F: for<'a, 'tcx> FnOnce(&ImplicitCtxt<'a, 'tcx>) -> R,
-    {
-        with_context_opt(|opt_context| f(opt_context.expect("no ImplicitCtxt stored in tls")))
-    }
-
-    /// Allows access to the current `ImplicitCtxt` whose tcx field is the same as the tcx argument
-    /// passed in. This means the closure is given an `ImplicitCtxt` with the same `'tcx` lifetime
-    /// as the `TyCtxt` passed in.
-    /// This will panic if you pass it a `TyCtxt` which is different from the current
-    /// `ImplicitCtxt`'s `tcx` field.
-    #[inline]
-    pub fn with_related_context<'tcx, F, R>(tcx: TyCtxt<'tcx>, f: F) -> R
-    where
-        F: FnOnce(&ImplicitCtxt<'_, 'tcx>) -> R,
-    {
-        with_context(|context| unsafe {
-            assert!(ptr_eq(context.tcx.gcx, tcx.gcx));
-            let context: &ImplicitCtxt<'_, '_> = mem::transmute(context);
-            f(context)
-        })
-    }
-
-    /// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
-    /// Panics if there is no `ImplicitCtxt` available.
-    #[inline]
-    pub fn with<F, R>(f: F) -> R
-    where
-        F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> R,
-    {
-        with_context(|context| f(context.tcx))
-    }
-
-    /// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
-    /// The closure is passed None if there is no `ImplicitCtxt` available.
-    #[inline]
-    pub fn with_opt<F, R>(f: F) -> R
-    where
-        F: for<'tcx> FnOnce(Option<TyCtxt<'tcx>>) -> R,
-    {
-        with_context_opt(|opt_context| f(opt_context.map(|context| context.tcx)))
-    }
-}
-
 macro_rules! sty_debug_print {
     ($fmt: expr, $ctxt: expr, $($variant: ident),*) => {{
         // Curious inner module to allow variant names to be used as
@@ -1452,6 +1422,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     Placeholder,
                     Generator,
                     GeneratorWitness,
+                    GeneratorWitnessMIR,
                     Dynamic,
                     Closure,
                     Tuple,
@@ -1547,7 +1518,7 @@ impl<'tcx, T: Hash> Hash for InternedInSet<'tcx, List<T>> {
 }
 
 macro_rules! direct_interners {
-    ($($name:ident: $method:ident($ty:ty): $ret_ctor:ident -> $ret_ty:ty,)+) => {
+    ($($name:ident: $vis:vis $method:ident($ty:ty): $ret_ctor:ident -> $ret_ty:ty,)+) => {
         $(impl<'tcx> Borrow<$ty> for InternedInSet<'tcx, $ty> {
             fn borrow<'a>(&'a self) -> &'a $ty {
                 &self.0
@@ -1573,7 +1544,7 @@ macro_rules! direct_interners {
         }
 
         impl<'tcx> TyCtxt<'tcx> {
-            pub fn $method(self, v: $ty) -> $ret_ty {
+            $vis fn $method(self, v: $ty) -> $ret_ty {
                 $ret_ctor(Interned::new_unchecked(self.interners.$name.intern(v, |v| {
                     InternedInSet(self.interners.arena.alloc(v))
                 }).0))
@@ -1582,36 +1553,47 @@ macro_rules! direct_interners {
     }
 }
 
+// Functions with a `mk_` prefix are intended for use outside this file and
+// crate. Functions with an `intern_` prefix are intended for use within this
+// file only, and have a corresponding `mk_` function.
 direct_interners! {
-    region: mk_region(RegionKind<'tcx>): Region -> Region<'tcx>,
-    const_: mk_const_internal(ConstData<'tcx>): Const -> Const<'tcx>,
-    const_allocation: intern_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
-    layout: intern_layout(LayoutS<VariantIdx>): Layout -> Layout<'tcx>,
-    adt_def: intern_adt_def(AdtDefData): AdtDef -> AdtDef<'tcx>,
+    region: intern_region(RegionKind<'tcx>): Region -> Region<'tcx>,
+    const_: intern_const(ConstData<'tcx>): Const -> Const<'tcx>,
+    const_allocation: pub mk_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
+    layout: pub mk_layout(LayoutS): Layout -> Layout<'tcx>,
+    adt_def: pub mk_adt_def_from_data(AdtDefData): AdtDef -> AdtDef<'tcx>,
+    external_constraints: pub mk_external_constraints(ExternalConstraintsData<'tcx>):
+        ExternalConstraints -> ExternalConstraints<'tcx>,
 }
 
 macro_rules! slice_interners {
-    ($($field:ident: $method:ident($ty:ty)),+ $(,)?) => (
+    ($($field:ident: $vis:vis $method:ident($ty:ty)),+ $(,)?) => (
         impl<'tcx> TyCtxt<'tcx> {
-            $(pub fn $method(self, v: &[$ty]) -> &'tcx List<$ty> {
-                self.interners.$field.intern_ref(v, || {
-                    InternedInSet(List::from_arena(&*self.arena, v))
-                }).0
+            $($vis fn $method(self, v: &[$ty]) -> &'tcx List<$ty> {
+                if v.is_empty() {
+                    List::empty()
+                } else {
+                    self.interners.$field.intern_ref(v, || {
+                        InternedInSet(List::from_arena(&*self.arena, v))
+                    }).0
+                }
             })+
         }
     );
 }
 
+// These functions intern slices. They all have a corresponding
+// `mk_foo_from_iter` function that interns an iterator. The slice version
+// should be used when possible, because it's faster.
 slice_interners!(
-    const_lists: _intern_const_list(Const<'tcx>),
-    substs: _intern_substs(GenericArg<'tcx>),
-    canonical_var_infos: _intern_canonical_var_infos(CanonicalVarInfo<'tcx>),
-    poly_existential_predicates:
-        _intern_poly_existential_predicates(PolyExistentialPredicate<'tcx>),
-    predicates: _intern_predicates(Predicate<'tcx>),
-    projs: _intern_projs(ProjectionKind),
-    place_elems: _intern_place_elems(PlaceElem<'tcx>),
-    bound_variable_kinds: _intern_bound_variable_kinds(ty::BoundVariableKind),
+    const_lists: pub mk_const_list(Const<'tcx>),
+    substs: pub mk_substs(GenericArg<'tcx>),
+    canonical_var_infos: pub mk_canonical_var_infos(CanonicalVarInfo<'tcx>),
+    poly_existential_predicates: intern_poly_existential_predicates(PolyExistentialPredicate<'tcx>),
+    predicates: intern_predicates(Predicate<'tcx>),
+    projs: pub mk_projs(ProjectionKind),
+    place_elems: pub mk_place_elems(PlaceElem<'tcx>),
+    bound_variable_kinds: pub mk_bound_variable_kinds(ty::BoundVariableKind),
 );
 
 impl<'tcx> TyCtxt<'tcx> {
@@ -1688,24 +1670,18 @@ impl<'tcx> TyCtxt<'tcx> {
         unsafety: hir::Unsafety,
     ) -> PolyFnSig<'tcx> {
         sig.map_bound(|s| {
-            let params_iter = match s.inputs()[0].kind() {
-                ty::Tuple(params) => params.into_iter(),
+            let params = match s.inputs()[0].kind() {
+                ty::Tuple(params) => *params,
                 _ => bug!(),
             };
-            self.mk_fn_sig(params_iter, s.output(), s.c_variadic, unsafety, abi::Abi::Rust)
+            self.mk_fn_sig(params, s.output(), s.c_variadic, unsafety, abi::Abi::Rust)
         })
     }
 
-    /// Same a `self.mk_region(kind)`, but avoids accessing the interners if
-    /// `*r == kind`.
-    #[inline]
-    pub fn reuse_or_mk_region(self, r: Region<'tcx>, kind: RegionKind<'tcx>) -> Region<'tcx> {
-        if *r == kind { r } else { self.mk_region(kind) }
-    }
-
+    // Avoid this in favour of more specific `mk_*` methods, where possible.
     #[allow(rustc::usage_of_ty_tykind)]
     #[inline]
-    pub fn mk_ty(self, st: TyKind<'tcx>) -> Ty<'tcx> {
+    pub fn mk_ty_from_kind(self, st: TyKind<'tcx>) -> Ty<'tcx> {
         self.interners.intern_ty(
             st,
             self.sess,
@@ -1770,12 +1746,12 @@ impl<'tcx> TyCtxt<'tcx> {
     #[inline]
     pub fn mk_adt(self, def: AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
         // Take a copy of substs so that we own the vectors inside.
-        self.mk_ty(Adt(def, substs))
+        self.mk_ty_from_kind(Adt(def, substs))
     }
 
     #[inline]
     pub fn mk_foreign(self, def_id: DefId) -> Ty<'tcx> {
-        self.mk_ty(Foreign(def_id))
+        self.mk_ty_from_kind(Foreign(def_id))
     }
 
     fn mk_generic_adt(self, wrapper_def_id: DefId, ty_param: Ty<'tcx>) -> Ty<'tcx> {
@@ -1788,11 +1764,11 @@ impl<'tcx> TyCtxt<'tcx> {
                         ty_param.into()
                     } else {
                         assert!(has_default);
-                        self.bound_type_of(param.def_id).subst(self, substs).into()
+                        self.type_of(param.def_id).subst(self, substs).into()
                     }
                 }
             });
-        self.mk_ty(Adt(adt_def, substs))
+        self.mk_ty_from_kind(Adt(adt_def, substs))
     }
 
     #[inline]
@@ -1821,12 +1797,12 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_ptr(self, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(RawPtr(tm))
+        self.mk_ty_from_kind(RawPtr(tm))
     }
 
     #[inline]
     pub fn mk_ref(self, r: Region<'tcx>, tm: TypeAndMut<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(Ref(r, tm.ty, tm.mutbl))
+        self.mk_ty_from_kind(Ref(r, tm.ty, tm.mutbl))
     }
 
     #[inline]
@@ -1851,21 +1827,34 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_array(self, ty: Ty<'tcx>, n: u64) -> Ty<'tcx> {
-        self.mk_ty(Array(ty, ty::Const::from_usize(self, n)))
+        self.mk_ty_from_kind(Array(ty, ty::Const::from_target_usize(self, n)))
+    }
+
+    #[inline]
+    pub fn mk_array_with_const_len(self, ty: Ty<'tcx>, ct: Const<'tcx>) -> Ty<'tcx> {
+        self.mk_ty_from_kind(Array(ty, ct))
     }
 
     #[inline]
     pub fn mk_slice(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(Slice(ty))
+        self.mk_ty_from_kind(Slice(ty))
     }
 
     #[inline]
-    pub fn intern_tup(self, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
-        self.mk_ty(Tuple(self.intern_type_list(&ts)))
+    pub fn mk_tup(self, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
+        if ts.is_empty() {
+            self.types.unit
+        } else {
+            self.mk_ty_from_kind(Tuple(self.mk_type_list(&ts)))
+        }
     }
 
-    pub fn mk_tup<I: InternAs<Ty<'tcx>, Ty<'tcx>>>(self, iter: I) -> I::Output {
-        iter.intern_with(|ts| self.mk_ty(Tuple(self.intern_type_list(&ts))))
+    pub fn mk_tup_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<Ty<'tcx>, Ty<'tcx>>,
+    {
+        T::collect_and_apply(iter, |ts| self.mk_tup(ts))
     }
 
     #[inline]
@@ -1882,17 +1871,17 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_fn_def(
         self,
         def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
-        let substs = self.check_substs(def_id, substs);
-        self.mk_ty(FnDef(def_id, substs))
+        let substs = self.check_and_mk_substs(def_id, substs);
+        self.mk_ty_from_kind(FnDef(def_id, substs))
     }
 
     #[inline(always)]
-    fn check_substs(
+    fn check_and_mk_substs(
         self,
         _def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> SubstsRef<'tcx> {
         let substs = substs.into_iter().map(Into::into);
         #[cfg(debug_assertions)]
@@ -1905,12 +1894,12 @@ impl<'tcx> TyCtxt<'tcx> {
                 substs.collect::<Vec<_>>(),
             );
         }
-        self.mk_substs(substs)
+        self.mk_substs_from_iter(substs)
     }
 
     #[inline]
     pub fn mk_fn_ptr(self, fty: PolyFnSig<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(FnPtr(fty))
+        self.mk_ty_from_kind(FnPtr(fty))
     }
 
     #[inline]
@@ -1920,21 +1909,21 @@ impl<'tcx> TyCtxt<'tcx> {
         reg: ty::Region<'tcx>,
         repr: DynKind,
     ) -> Ty<'tcx> {
-        self.mk_ty(Dynamic(obj, reg, repr))
+        self.mk_ty_from_kind(Dynamic(obj, reg, repr))
     }
 
     #[inline]
     pub fn mk_projection(
         self,
         item_def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
-        self.mk_ty(Alias(ty::Projection, self.mk_alias_ty(item_def_id, substs)))
+        self.mk_alias(ty::Projection, self.mk_alias_ty(item_def_id, substs))
     }
 
     #[inline]
     pub fn mk_closure(self, closure_id: DefId, closure_substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(Closure(closure_id, closure_substs))
+        self.mk_ty_from_kind(Closure(closure_id, closure_substs))
     }
 
     #[inline]
@@ -1944,71 +1933,183 @@ impl<'tcx> TyCtxt<'tcx> {
         generator_substs: SubstsRef<'tcx>,
         movability: hir::Movability,
     ) -> Ty<'tcx> {
-        self.mk_ty(Generator(id, generator_substs, movability))
+        self.mk_ty_from_kind(Generator(id, generator_substs, movability))
     }
 
     #[inline]
     pub fn mk_generator_witness(self, types: ty::Binder<'tcx, &'tcx List<Ty<'tcx>>>) -> Ty<'tcx> {
-        self.mk_ty(GeneratorWitness(types))
+        self.mk_ty_from_kind(GeneratorWitness(types))
     }
 
     /// Creates a `&mut Context<'_>` [`Ty`] with erased lifetimes.
     pub fn mk_task_context(self) -> Ty<'tcx> {
         let context_did = self.require_lang_item(LangItem::Context, None);
         let context_adt_ref = self.adt_def(context_did);
-        let context_substs = self.intern_substs(&[self.lifetimes.re_erased.into()]);
+        let context_substs = self.mk_substs(&[self.lifetimes.re_erased.into()]);
         let context_ty = self.mk_adt(context_adt_ref, context_substs);
         self.mk_mut_ref(self.lifetimes.re_erased, context_ty)
     }
 
     #[inline]
-    pub fn mk_ty_var(self, v: TyVid) -> Ty<'tcx> {
-        self.mk_ty_infer(TyVar(v))
+    pub fn mk_generator_witness_mir(self, id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
+        self.mk_ty_from_kind(GeneratorWitnessMIR(id, substs))
     }
 
     #[inline]
     pub fn mk_const(self, kind: impl Into<ty::ConstKind<'tcx>>, ty: Ty<'tcx>) -> Const<'tcx> {
-        self.mk_const_internal(ty::ConstData { kind: kind.into(), ty })
+        self.intern_const(ty::ConstData { kind: kind.into(), ty })
+    }
+
+    #[inline]
+    pub fn mk_ty_var(self, v: TyVid) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        self.types
+            .ty_vars
+            .get(v.as_usize())
+            .copied()
+            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(TyVar(v))))
     }
 
     #[inline]
     pub fn mk_int_var(self, v: IntVid) -> Ty<'tcx> {
-        self.mk_ty_infer(IntVar(v))
+        self.mk_ty_from_kind(Infer(IntVar(v)))
     }
 
     #[inline]
     pub fn mk_float_var(self, v: FloatVid) -> Ty<'tcx> {
-        self.mk_ty_infer(FloatVar(v))
+        self.mk_ty_from_kind(Infer(FloatVar(v)))
+    }
+
+    #[inline]
+    pub fn mk_fresh_ty(self, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        self.types
+            .fresh_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshTy(n))))
     }
 
     #[inline]
-    pub fn mk_ty_infer(self, it: InferTy) -> Ty<'tcx> {
-        self.mk_ty(Infer(it))
+    pub fn mk_fresh_int_ty(self, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        self.types
+            .fresh_int_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshIntTy(n))))
+    }
+
+    #[inline]
+    pub fn mk_fresh_float_ty(self, n: u32) -> Ty<'tcx> {
+        // Use a pre-interned one when possible.
+        self.types
+            .fresh_float_tys
+            .get(n as usize)
+            .copied()
+            .unwrap_or_else(|| self.mk_ty_from_kind(Infer(ty::FreshFloatTy(n))))
     }
 
     #[inline]
     pub fn mk_ty_param(self, index: u32, name: Symbol) -> Ty<'tcx> {
-        self.mk_ty(Param(ParamTy { index, name }))
+        self.mk_ty_from_kind(Param(ParamTy { index, name }))
     }
 
     pub fn mk_param_from_def(self, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
         match param.kind {
             GenericParamDefKind::Lifetime => {
-                self.mk_region(ty::ReEarlyBound(param.to_early_bound_region_data())).into()
+                self.mk_re_early_bound(param.to_early_bound_region_data()).into()
             }
             GenericParamDefKind::Type { .. } => self.mk_ty_param(param.index, param.name).into(),
             GenericParamDefKind::Const { .. } => self
                 .mk_const(
                     ParamConst { index: param.index, name: param.name },
-                    self.type_of(param.def_id),
+                    self.type_of(param.def_id)
+                        .no_bound_vars()
+                        .expect("const parameter types cannot be generic"),
                 )
                 .into(),
         }
     }
 
     #[inline]
+    pub fn mk_bound(self, index: ty::DebruijnIndex, bound_ty: ty::BoundTy) -> Ty<'tcx> {
+        self.mk_ty_from_kind(Bound(index, bound_ty))
+    }
+
+    #[inline]
+    pub fn mk_placeholder(self, placeholder: ty::PlaceholderType) -> Ty<'tcx> {
+        self.mk_ty_from_kind(Placeholder(placeholder))
+    }
+
+    #[inline]
+    pub fn mk_alias(self, kind: ty::AliasKind, alias_ty: ty::AliasTy<'tcx>) -> Ty<'tcx> {
+        self.mk_ty_from_kind(Alias(kind, alias_ty))
+    }
+
+    #[inline]
     pub fn mk_opaque(self, def_id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_ty(Alias(ty::Opaque, self.mk_alias_ty(def_id, substs)))
+        self.mk_alias(ty::Opaque, self.mk_alias_ty(def_id, substs))
+    }
+
+    #[inline]
+    pub fn mk_re_early_bound(self, early_bound_region: ty::EarlyBoundRegion) -> Region<'tcx> {
+        self.intern_region(ty::ReEarlyBound(early_bound_region))
+    }
+
+    #[inline]
+    pub fn mk_re_late_bound(
+        self,
+        debruijn: ty::DebruijnIndex,
+        bound_region: ty::BoundRegion,
+    ) -> Region<'tcx> {
+        // Use a pre-interned one when possible.
+        if let ty::BoundRegion { var, kind: ty::BrAnon(v, None) } = bound_region
+            && var.as_u32() == v
+            && let Some(inner) = self.lifetimes.re_late_bounds.get(debruijn.as_usize())
+            && let Some(re) = inner.get(v as usize).copied()
+        {
+            re
+        } else {
+            self.intern_region(ty::ReLateBound(debruijn, bound_region))
+        }
+    }
+
+    #[inline]
+    pub fn mk_re_free(self, scope: DefId, bound_region: ty::BoundRegionKind) -> Region<'tcx> {
+        self.intern_region(ty::ReFree(ty::FreeRegion { scope, bound_region }))
+    }
+
+    #[inline]
+    pub fn mk_re_var(self, v: ty::RegionVid) -> Region<'tcx> {
+        // Use a pre-interned one when possible.
+        self.lifetimes
+            .re_vars
+            .get(v.as_usize())
+            .copied()
+            .unwrap_or_else(|| self.intern_region(ty::ReVar(v)))
+    }
+
+    #[inline]
+    pub fn mk_re_placeholder(self, placeholder: ty::PlaceholderRegion) -> Region<'tcx> {
+        self.intern_region(ty::RePlaceholder(placeholder))
+    }
+
+    // Avoid this in favour of more specific `mk_re_*` methods, where possible,
+    // to avoid the cost of the `match`.
+    pub fn mk_region_from_kind(self, kind: ty::RegionKind<'tcx>) -> Region<'tcx> {
+        match kind {
+            ty::ReEarlyBound(region) => self.mk_re_early_bound(region),
+            ty::ReLateBound(debruijn, region) => self.mk_re_late_bound(debruijn, region),
+            ty::ReFree(ty::FreeRegion { scope, bound_region }) => {
+                self.mk_re_free(scope, bound_region)
+            }
+            ty::ReStatic => self.lifetimes.re_static,
+            ty::ReVar(vid) => self.mk_re_var(vid),
+            ty::RePlaceholder(region) => self.mk_re_placeholder(region),
+            ty::ReErased => self.lifetimes.re_erased,
+            ty::ReError(reported) => self.mk_re_error(reported),
+        }
     }
 
     pub fn mk_place_field(self, place: Place<'tcx>, f: Field, ty: Ty<'tcx>) -> Place<'tcx> {
@@ -2050,10 +2151,10 @@ impl<'tcx> TyCtxt<'tcx> {
         let mut projection = place.projection.to_vec();
         projection.push(elem);
 
-        Place { local: place.local, projection: self.intern_place_elems(&projection) }
+        Place { local: place.local, projection: self.mk_place_elems(&projection) }
     }
 
-    pub fn intern_poly_existential_predicates(
+    pub fn mk_poly_existential_predicates(
         self,
         eps: &[PolyExistentialPredicate<'tcx>],
     ) -> &'tcx List<PolyExistentialPredicate<'tcx>> {
@@ -2063,125 +2164,109 @@ impl<'tcx> TyCtxt<'tcx> {
                 .all(|[a, b]| a.skip_binder().stable_cmp(self, &b.skip_binder())
                     != Ordering::Greater)
         );
-        self._intern_poly_existential_predicates(eps)
+        self.intern_poly_existential_predicates(eps)
     }
 
-    pub fn intern_predicates(self, preds: &[Predicate<'tcx>]) -> &'tcx List<Predicate<'tcx>> {
+    pub fn mk_predicates(self, preds: &[Predicate<'tcx>]) -> &'tcx List<Predicate<'tcx>> {
         // FIXME consider asking the input slice to be sorted to avoid
         // re-interning permutations, in which case that would be asserted
         // here.
-        if preds.is_empty() {
-            // The macro-generated method below asserts we don't intern an empty slice.
-            List::empty()
-        } else {
-            self._intern_predicates(preds)
-        }
-    }
-
-    pub fn mk_const_list<I: InternAs<ty::Const<'tcx>, &'tcx List<ty::Const<'tcx>>>>(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_const_list(xs))
-    }
-
-    pub fn intern_const_list(self, cs: &[ty::Const<'tcx>]) -> &'tcx List<ty::Const<'tcx>> {
-        if cs.is_empty() { List::empty() } else { self._intern_const_list(cs) }
-    }
-
-    pub fn intern_type_list(self, ts: &[Ty<'tcx>]) -> &'tcx List<Ty<'tcx>> {
-        if ts.is_empty() {
-            List::empty()
-        } else {
-            // Actually intern type lists as lists of `GenericArg`s.
-            //
-            // Transmuting from `Ty<'tcx>` to `GenericArg<'tcx>` is sound
-            // as explained in ty_slice_as_generic_arg`. With this,
-            // we guarantee that even when transmuting between `List<Ty<'tcx>>`
-            // and `List<GenericArg<'tcx>>`, the uniqueness requirement for
-            // lists is upheld.
-            let substs = self._intern_substs(ty::subst::ty_slice_as_generic_args(ts));
-            substs.try_as_type_list().unwrap()
-        }
-    }
-
-    pub fn intern_substs(self, ts: &[GenericArg<'tcx>]) -> &'tcx List<GenericArg<'tcx>> {
-        if ts.is_empty() { List::empty() } else { self._intern_substs(ts) }
+        self.intern_predicates(preds)
     }
 
-    pub fn intern_projs(self, ps: &[ProjectionKind]) -> &'tcx List<ProjectionKind> {
-        if ps.is_empty() { List::empty() } else { self._intern_projs(ps) }
-    }
-
-    pub fn intern_place_elems(self, ts: &[PlaceElem<'tcx>]) -> &'tcx List<PlaceElem<'tcx>> {
-        if ts.is_empty() { List::empty() } else { self._intern_place_elems(ts) }
-    }
-
-    pub fn intern_canonical_var_infos(
-        self,
-        ts: &[CanonicalVarInfo<'tcx>],
-    ) -> CanonicalVarInfos<'tcx> {
-        if ts.is_empty() { List::empty() } else { self._intern_canonical_var_infos(ts) }
-    }
-
-    pub fn intern_bound_variable_kinds(
-        self,
-        ts: &[ty::BoundVariableKind],
-    ) -> &'tcx List<ty::BoundVariableKind> {
-        if ts.is_empty() { List::empty() } else { self._intern_bound_variable_kinds(ts) }
+    pub fn mk_const_list_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<ty::Const<'tcx>, &'tcx List<ty::Const<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_const_list(xs))
     }
 
-    pub fn mk_fn_sig<I>(
+    pub fn mk_type_list(self, ts: &[Ty<'tcx>]) -> &'tcx List<Ty<'tcx>> {
+        // Actually intern type lists as lists of `GenericArg`s.
+        //
+        // Transmuting from `Ty<'tcx>` to `GenericArg<'tcx>` is sound
+        // as explained in `ty_slice_as_generic_arg`. With this,
+        // we guarantee that even when transmuting between `List<Ty<'tcx>>`
+        // and `List<GenericArg<'tcx>>`, the uniqueness requirement for
+        // lists is upheld.
+        let substs = self.mk_substs(ty::subst::ty_slice_as_generic_args(ts));
+        substs.try_as_type_list().unwrap()
+    }
+
+    // Unlike various other `mk_*_from_iter` functions, this one uses `I:
+    // IntoIterator` instead of `I: Iterator`, and it doesn't have a slice
+    // variant, because of the need to combine `inputs` and `output`. This
+    // explains the lack of `_from_iter` suffix.
+    pub fn mk_fn_sig<I, T>(
         self,
         inputs: I,
         output: I::Item,
         c_variadic: bool,
         unsafety: hir::Unsafety,
         abi: abi::Abi,
-    ) -> <I::Item as InternIteratorElement<Ty<'tcx>, ty::FnSig<'tcx>>>::Output
+    ) -> T::Output
     where
-        I: Iterator<Item: InternIteratorElement<Ty<'tcx>, ty::FnSig<'tcx>>>,
+        I: IntoIterator<Item = T>,
+        T: CollectAndApply<Ty<'tcx>, ty::FnSig<'tcx>>,
     {
-        inputs.chain(iter::once(output)).intern_with(|xs| ty::FnSig {
-            inputs_and_output: self.intern_type_list(xs),
+        T::collect_and_apply(inputs.into_iter().chain(iter::once(output)), |xs| ty::FnSig {
+            inputs_and_output: self.mk_type_list(xs),
             c_variadic,
             unsafety,
             abi,
         })
     }
 
-    pub fn mk_poly_existential_predicates<
-        I: InternAs<PolyExistentialPredicate<'tcx>, &'tcx List<PolyExistentialPredicate<'tcx>>>,
-    >(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_poly_existential_predicates(xs))
+    pub fn mk_poly_existential_predicates_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<
+                PolyExistentialPredicate<'tcx>,
+                &'tcx List<PolyExistentialPredicate<'tcx>>,
+            >,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_poly_existential_predicates(xs))
     }
 
-    pub fn mk_predicates<I: InternAs<Predicate<'tcx>, &'tcx List<Predicate<'tcx>>>>(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_predicates(xs))
+    pub fn mk_predicates_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<Predicate<'tcx>, &'tcx List<Predicate<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_predicates(xs))
     }
 
-    pub fn mk_type_list<I: InternAs<Ty<'tcx>, &'tcx List<Ty<'tcx>>>>(self, iter: I) -> I::Output {
-        iter.intern_with(|xs| self.intern_type_list(xs))
+    pub fn mk_type_list_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<Ty<'tcx>, &'tcx List<Ty<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_type_list(xs))
     }
 
-    pub fn mk_substs<I: InternAs<GenericArg<'tcx>, &'tcx List<GenericArg<'tcx>>>>(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_substs(xs))
+    pub fn mk_substs_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<GenericArg<'tcx>, &'tcx List<GenericArg<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_substs(xs))
     }
 
-    pub fn mk_place_elems<I: InternAs<PlaceElem<'tcx>, &'tcx List<PlaceElem<'tcx>>>>(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_place_elems(xs))
+    pub fn mk_canonical_var_infos_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<CanonicalVarInfo<'tcx>, &'tcx List<CanonicalVarInfo<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_canonical_var_infos(xs))
+    }
+
+    pub fn mk_place_elems_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<PlaceElem<'tcx>, &'tcx List<PlaceElem<'tcx>>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_place_elems(xs))
     }
 
     pub fn mk_substs_trait(
@@ -2189,34 +2274,33 @@ impl<'tcx> TyCtxt<'tcx> {
         self_ty: Ty<'tcx>,
         rest: impl IntoIterator<Item = GenericArg<'tcx>>,
     ) -> SubstsRef<'tcx> {
-        self.mk_substs(iter::once(self_ty.into()).chain(rest))
+        self.mk_substs_from_iter(iter::once(self_ty.into()).chain(rest))
     }
 
     pub fn mk_trait_ref(
         self,
         trait_def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
-        let substs = self.check_substs(trait_def_id, substs);
+        let substs = self.check_and_mk_substs(trait_def_id, substs);
         ty::TraitRef { def_id: trait_def_id, substs, _use_mk_trait_ref_instead: () }
     }
 
     pub fn mk_alias_ty(
         self,
         def_id: DefId,
-        substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> ty::AliasTy<'tcx> {
-        let substs = self.check_substs(def_id, substs);
+        let substs = self.check_and_mk_substs(def_id, substs);
         ty::AliasTy { def_id, substs, _use_mk_alias_ty_instead: () }
     }
 
-    pub fn mk_bound_variable_kinds<
-        I: InternAs<ty::BoundVariableKind, &'tcx List<ty::BoundVariableKind>>,
-    >(
-        self,
-        iter: I,
-    ) -> I::Output {
-        iter.intern_with(|xs| self.intern_bound_variable_kinds(xs))
+    pub fn mk_bound_variable_kinds_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<ty::BoundVariableKind, &'tcx List<ty::BoundVariableKind>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_bound_variable_kinds(xs))
     }
 
     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
@@ -2291,26 +2375,23 @@ impl<'tcx> TyCtxt<'tcx> {
         Some(&*candidates)
     }
 
-    pub fn named_region(self, id: HirId) -> Option<resolve_lifetime::Region> {
+    pub fn named_bound_var(self, id: HirId) -> Option<resolve_bound_vars::ResolvedArg> {
         debug!(?id, "named_region");
-        self.named_region_map(id.owner).and_then(|map| map.get(&id.local_id).cloned())
+        self.named_variable_map(id.owner).and_then(|map| map.get(&id.local_id).cloned())
     }
 
     pub fn is_late_bound(self, id: HirId) -> bool {
-        self.is_late_bound_map(id.owner.def_id).map_or(false, |set| {
-            let def_id = self.hir().local_def_id(id);
-            set.contains(&def_id)
-        })
+        self.is_late_bound_map(id.owner).map_or(false, |set| set.contains(&id.local_id))
     }
 
     pub fn late_bound_vars(self, id: HirId) -> &'tcx List<ty::BoundVariableKind> {
         self.mk_bound_variable_kinds(
-            self.late_bound_vars_map(id.owner)
+            &self
+                .late_bound_vars_map(id.owner)
                 .and_then(|map| map.get(&id.local_id).cloned())
                 .unwrap_or_else(|| {
-                    bug!("No bound vars found for {:?} ({:?})", self.hir().node_to_string(id), id)
-                })
-                .iter(),
+                    bug!("No bound vars found for {}", self.hir().node_to_string(id))
+                }),
         )
     }
 
@@ -2351,16 +2432,24 @@ impl<'tcx> TyCtxt<'tcx> {
             })
         )
     }
+
+    pub fn local_def_id_to_hir_id(self, local_def_id: LocalDefId) -> HirId {
+        self.opt_local_def_id_to_hir_id(local_def_id).unwrap()
+    }
+
+    pub fn trait_solver_next(self) -> bool {
+        self.sess.opts.unstable_opts.trait_solver == rustc_session::config::TraitSolver::Next
+    }
 }
 
 impl<'tcx> TyCtxtAt<'tcx> {
     /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
     #[track_caller]
-    pub fn ty_error(self) -> Ty<'tcx> {
+    pub fn ty_error_misc(self) -> Ty<'tcx> {
         self.tcx.ty_error_with_message(self.span, "TyKind::Error constructed but no error reported")
     }
 
-    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` with the given `msg to
+    /// Constructs a `TyKind::Error` type and registers a `delay_span_bug` with the given `msg` to
     /// ensure it gets used.
     #[track_caller]
     pub fn ty_error_with_message(self, msg: &str) -> Ty<'tcx> {
@@ -2370,7 +2459,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
     pub fn mk_trait_ref(
         self,
         trait_lang_item: LangItem,
-        substs: impl IntoIterator<Item = impl Into<ty::GenericArg<'tcx>>>,
+        substs: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
     ) -> ty::TraitRef<'tcx> {
         let trait_def_id = self.require_lang_item(trait_lang_item, Some(self.span));
         self.tcx.mk_trait_ref(trait_def_id, substs)
@@ -2392,19 +2481,11 @@ pub struct DeducedParamAttrs {
     pub read_only: bool,
 }
 
-// We are comparing types with different invariant lifetimes, so `ptr::eq`
-// won't work for us.
-fn ptr_eq<T, U>(t: *const T, u: *const U) -> bool {
-    t as *const () == u as *const ()
-}
-
 pub fn provide(providers: &mut ty::query::Providers) {
     providers.module_reexports =
         |tcx, id| tcx.resolutions(()).reexport_map.get(&id).map(|v| &v[..]);
     providers.maybe_unused_trait_imports =
         |tcx, ()| &tcx.resolutions(()).maybe_unused_trait_imports;
-    providers.maybe_unused_extern_crates =
-        |tcx, ()| &tcx.resolutions(()).maybe_unused_extern_crates[..];
     providers.names_imported_by_glob_use = |tcx, id| {
         tcx.arena.alloc(tcx.resolutions(()).glob_map.get(&id).cloned().unwrap_or_default())
     };
@@ -2424,6 +2505,5 @@ pub fn provide(providers: &mut ty::query::Providers) {
         // We want to check if the panic handler was defined in this crate
         tcx.lang_items().panic_impl().map_or(false, |did| did.is_local())
     };
-    providers.source_span =
-        |tcx, def_id| tcx.untracked.source_span.get(def_id).copied().unwrap_or(DUMMY_SP);
+    providers.source_span = |tcx, def_id| tcx.untracked.source_span.get(def_id).unwrap_or(DUMMY_SP);
 }
diff --git a/compiler/rustc_middle/src/ty/context/tls.rs b/compiler/rustc_middle/src/ty/context/tls.rs
new file mode 100644
index 000000000..5426ac8d7
--- /dev/null
+++ b/compiler/rustc_middle/src/ty/context/tls.rs
@@ -0,0 +1,186 @@
+use super::{GlobalCtxt, TyCtxt};
+
+use crate::dep_graph::TaskDepsRef;
+use crate::ty::query;
+use rustc_data_structures::sync::{self, Lock};
+use rustc_errors::Diagnostic;
+use std::mem;
+use std::ptr;
+use thin_vec::ThinVec;
+
+/// This is the implicit state of rustc. It contains the current
+/// `TyCtxt` and query. It is updated when creating a local interner or
+/// executing a new query. Whenever there's a `TyCtxt` value available
+/// you should also have access to an `ImplicitCtxt` through the functions
+/// in this module.
+#[derive(Clone)]
+pub struct ImplicitCtxt<'a, 'tcx> {
+    /// The current `TyCtxt`.
+    pub tcx: TyCtxt<'tcx>,
+
+    /// The current query job, if any. This is updated by `JobOwner::start` in
+    /// `ty::query::plumbing` when executing a query.
+    pub query: Option<query::QueryJobId>,
+
+    /// Where to store diagnostics for the current query job, if any.
+    /// This is updated by `JobOwner::start` in `ty::query::plumbing` when executing a query.
+    pub diagnostics: Option<&'a Lock<ThinVec<Diagnostic>>>,
+
+    /// Used to prevent queries from calling too deeply.
+    pub query_depth: usize,
+
+    /// The current dep graph task. This is used to add dependencies to queries
+    /// when executing them.
+    pub task_deps: TaskDepsRef<'a>,
+}
+
+impl<'a, 'tcx> ImplicitCtxt<'a, 'tcx> {
+    pub fn new(gcx: &'tcx GlobalCtxt<'tcx>) -> Self {
+        let tcx = TyCtxt { gcx };
+        ImplicitCtxt {
+            tcx,
+            query: None,
+            diagnostics: None,
+            query_depth: 0,
+            task_deps: TaskDepsRef::Ignore,
+        }
+    }
+}
+
+#[cfg(parallel_compiler)]
+mod tlv {
+    use rustc_rayon_core as rayon_core;
+    use std::ptr;
+
+    /// Gets Rayon's thread-local variable, which is preserved for Rayon jobs.
+    /// This is used to get the pointer to the current `ImplicitCtxt`.
+    #[inline]
+    pub(super) fn get_tlv() -> *const () {
+        ptr::from_exposed_addr(rayon_core::tlv::get())
+    }
+
+    /// Sets Rayon's thread-local variable, which is preserved for Rayon jobs
+    /// to `value` during the call to `f`. It is restored to its previous value after.
+    /// This is used to set the pointer to the new `ImplicitCtxt`.
+    #[inline]
+    pub(super) fn with_tlv<F: FnOnce() -> R, R>(value: *const (), f: F) -> R {
+        rayon_core::tlv::with(value.expose_addr(), f)
+    }
+}
+
+#[cfg(not(parallel_compiler))]
+mod tlv {
+    use std::cell::Cell;
+    use std::ptr;
+
+    thread_local! {
+        /// A thread local variable that stores a pointer to the current `ImplicitCtxt`.
+        static TLV: Cell<*const ()> = const { Cell::new(ptr::null()) };
+    }
+
+    /// Gets the pointer to the current `ImplicitCtxt`.
+    #[inline]
+    pub(super) fn get_tlv() -> *const () {
+        TLV.with(|tlv| tlv.get())
+    }
+
+    /// Sets TLV to `value` during the call to `f`.
+    /// It is restored to its previous value after.
+    /// This is used to set the pointer to the new `ImplicitCtxt`.
+    #[inline]
+    pub(super) fn with_tlv<F: FnOnce() -> R, R>(value: *const (), f: F) -> R {
+        let old = TLV.replace(value);
+        let _reset = rustc_data_structures::OnDrop(move || TLV.set(old));
+        f()
+    }
+}
+
+#[inline]
+fn erase(context: &ImplicitCtxt<'_, '_>) -> *const () {
+    context as *const _ as *const ()
+}
+
+#[inline]
+unsafe fn downcast<'a, 'tcx>(context: *const ()) -> &'a ImplicitCtxt<'a, 'tcx> {
+    &*(context as *const ImplicitCtxt<'a, 'tcx>)
+}
+
+/// Sets `context` as the new current `ImplicitCtxt` for the duration of the function `f`.
+#[inline]
+pub fn enter_context<'a, 'tcx, F, R>(context: &ImplicitCtxt<'a, 'tcx>, f: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    tlv::with_tlv(erase(context), f)
+}
+
+/// Allows access to the current `ImplicitCtxt` in a closure if one is available.
+#[inline]
+pub fn with_context_opt<F, R>(f: F) -> R
+where
+    F: for<'a, 'tcx> FnOnce(Option<&ImplicitCtxt<'a, 'tcx>>) -> R,
+{
+    let context = tlv::get_tlv();
+    if context.is_null() {
+        f(None)
+    } else {
+        // We could get an `ImplicitCtxt` pointer from another thread.
+        // Ensure that `ImplicitCtxt` is `Sync`.
+        sync::assert_sync::<ImplicitCtxt<'_, '_>>();
+
+        unsafe { f(Some(downcast(context))) }
+    }
+}
+
+/// Allows access to the current `ImplicitCtxt`.
+/// Panics if there is no `ImplicitCtxt` available.
+#[inline]
+pub fn with_context<F, R>(f: F) -> R
+where
+    F: for<'a, 'tcx> FnOnce(&ImplicitCtxt<'a, 'tcx>) -> R,
+{
+    with_context_opt(|opt_context| f(opt_context.expect("no ImplicitCtxt stored in tls")))
+}
+
+/// Allows access to the current `ImplicitCtxt` whose tcx field is the same as the tcx argument
+/// passed in. This means the closure is given an `ImplicitCtxt` with the same `'tcx` lifetime
+/// as the `TyCtxt` passed in.
+/// This will panic if you pass it a `TyCtxt` which is different from the current
+/// `ImplicitCtxt`'s `tcx` field.
+#[inline]
+pub fn with_related_context<'tcx, F, R>(tcx: TyCtxt<'tcx>, f: F) -> R
+where
+    F: FnOnce(&ImplicitCtxt<'_, 'tcx>) -> R,
+{
+    with_context(|context| {
+        // The two gcx have different invariant lifetimes, so we need to erase them for the comparison.
+        assert!(ptr::eq(
+            context.tcx.gcx as *const _ as *const (),
+            tcx.gcx as *const _ as *const ()
+        ));
+
+        let context: &ImplicitCtxt<'_, '_> = unsafe { mem::transmute(context) };
+
+        f(context)
+    })
+}
+
+/// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
+/// Panics if there is no `ImplicitCtxt` available.
+#[inline]
+pub fn with<F, R>(f: F) -> R
+where
+    F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> R,
+{
+    with_context(|context| f(context.tcx))
+}
+
+/// Allows access to the `TyCtxt` in the current `ImplicitCtxt`.
+/// The closure is passed None if there is no `ImplicitCtxt` available.
+#[inline]
+pub fn with_opt<F, R>(f: F) -> R
+where
+    F: for<'tcx> FnOnce(Option<TyCtxt<'tcx>>) -> R,
+{
+    with_context_opt(|opt_context| f(opt_context.map(|context| context.tcx)))
+}
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 4b4518f61..e894e1aaf 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -3,8 +3,9 @@
 use std::ops::ControlFlow;
 
 use crate::ty::{
-    visit::TypeVisitable, AliasTy, Const, ConstKind, DefIdTree, InferConst, InferTy, Opaque,
-    PolyTraitPredicate, Projection, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor,
+    AliasTy, Const, ConstKind, DefIdTree, FallibleTypeFolder, InferConst, InferTy, Opaque,
+    PolyTraitPredicate, Projection, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
+    TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
 
 use rustc_data_structures::fx::FxHashMap;
@@ -76,7 +77,7 @@ impl<'tcx> Ty<'tcx> {
     }
 }
 
-pub trait IsSuggestable<'tcx> {
+pub trait IsSuggestable<'tcx>: Sized {
     /// Whether this makes sense to suggest in a diagnostic.
     ///
     /// We filter out certain types and constants since they don't provide
@@ -87,15 +88,21 @@ pub trait IsSuggestable<'tcx> {
     /// Only if `infer_suggestable` is true, we consider type and const
     /// inference variables to be suggestable.
     fn is_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> bool;
+
+    fn make_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> Option<Self>;
 }
 
 impl<'tcx, T> IsSuggestable<'tcx> for T
 where
-    T: TypeVisitable<'tcx>,
+    T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
 {
     fn is_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> bool {
         self.visit_with(&mut IsSuggestableVisitor { tcx, infer_suggestable }).is_continue()
     }
+
+    fn make_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> Option<T> {
+        self.try_fold_with(&mut MakeSuggestableFolder { tcx, infer_suggestable }).ok()
+    }
 }
 
 pub fn suggest_arbitrary_trait_bound<'tcx>(
@@ -186,6 +193,9 @@ fn suggest_removing_unsized_bound(
 }
 
 /// Suggest restricting a type param with a new bound.
+///
+/// If `span_to_replace` is provided, then that span will be replaced with the
+/// `constraint`. If one wasn't provided, then the full bound will be suggested.
 pub fn suggest_constraining_type_param(
     tcx: TyCtxt<'_>,
     generics: &hir::Generics<'_>,
@@ -193,12 +203,14 @@ pub fn suggest_constraining_type_param(
     param_name: &str,
     constraint: &str,
     def_id: Option<DefId>,
+    span_to_replace: Option<Span>,
 ) -> bool {
     suggest_constraining_type_params(
         tcx,
         generics,
         err,
         [(param_name, constraint, def_id)].into_iter(),
+        span_to_replace,
     )
 }
 
@@ -208,6 +220,7 @@ pub fn suggest_constraining_type_params<'a>(
     generics: &hir::Generics<'_>,
     err: &mut Diagnostic,
     param_names_and_constraints: impl Iterator<Item = (&'a str, &'a str, Option<DefId>)>,
+    span_to_replace: Option<Span>,
 ) -> bool {
     let mut grouped = FxHashMap::default();
     param_names_and_constraints.for_each(|(param_name, constraint, def_id)| {
@@ -246,7 +259,9 @@ pub fn suggest_constraining_type_params<'a>(
         let mut suggest_restrict = |span, bound_list_non_empty| {
             suggestions.push((
                 span,
-                if bound_list_non_empty {
+                if span_to_replace.is_some() {
+                    constraint.clone()
+                } else if bound_list_non_empty {
                     format!(" + {}", constraint)
                 } else {
                     format!(" {}", constraint)
@@ -255,6 +270,11 @@ pub fn suggest_constraining_type_params<'a>(
             ))
         };
 
+        if let Some(span) = span_to_replace {
+            suggest_restrict(span, true);
+            continue;
+        }
+
         // When the type parameter has been provided bounds
         //
         //    Message:
@@ -440,7 +460,7 @@ pub struct IsSuggestableVisitor<'tcx> {
     infer_suggestable: bool,
 }
 
-impl<'tcx> TypeVisitor<'tcx> for IsSuggestableVisitor<'tcx> {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IsSuggestableVisitor<'tcx> {
     type BreakTy = ();
 
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
@@ -460,8 +480,9 @@ impl<'tcx> TypeVisitor<'tcx> for IsSuggestableVisitor<'tcx> {
 
             Alias(Opaque, AliasTy { def_id, .. }) => {
                 let parent = self.tcx.parent(def_id);
+                let parent_ty = self.tcx.type_of(parent).subst_identity();
                 if let DefKind::TyAlias | DefKind::AssocTy = self.tcx.def_kind(parent)
-                    && let Alias(Opaque, AliasTy { def_id: parent_opaque_def_id, .. }) = *self.tcx.type_of(parent).kind()
+                    && let Alias(Opaque, AliasTy { def_id: parent_opaque_def_id, .. }) = *parent_ty.kind()
                     && parent_opaque_def_id == def_id
                 {
                     // Okay
@@ -509,3 +530,92 @@ impl<'tcx> TypeVisitor<'tcx> for IsSuggestableVisitor<'tcx> {
         c.super_visit_with(self)
     }
 }
+
+pub struct MakeSuggestableFolder<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    infer_suggestable: bool,
+}
+
+impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for MakeSuggestableFolder<'tcx> {
+    type Error = ();
+
+    fn interner(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
+        let t = match *t.kind() {
+            Infer(InferTy::TyVar(_)) if self.infer_suggestable => t,
+
+            FnDef(def_id, substs) => {
+                self.tcx.mk_fn_ptr(self.tcx.fn_sig(def_id).subst(self.tcx, substs))
+            }
+
+            // FIXME(compiler-errors): We could replace these with infer, I guess.
+            Closure(..)
+            | Infer(..)
+            | Generator(..)
+            | GeneratorWitness(..)
+            | Bound(_, _)
+            | Placeholder(_)
+            | Error(_) => {
+                return Err(());
+            }
+
+            Alias(Opaque, AliasTy { def_id, .. }) => {
+                let parent = self.tcx.parent(def_id);
+                let parent_ty = self.tcx.type_of(parent).subst_identity();
+                if let hir::def::DefKind::TyAlias | hir::def::DefKind::AssocTy = self.tcx.def_kind(parent)
+                    && let Alias(Opaque, AliasTy { def_id: parent_opaque_def_id, .. }) = *parent_ty.kind()
+                    && parent_opaque_def_id == def_id
+                {
+                    t
+                } else {
+                    return Err(());
+                }
+            }
+
+            Param(param) => {
+                // FIXME: It would be nice to make this not use string manipulation,
+                // but it's pretty hard to do this, since `ty::ParamTy` is missing
+                // sufficient info to determine if it is synthetic, and we don't
+                // always have a convenient way of getting `ty::Generics` at the call
+                // sites we invoke `IsSuggestable::is_suggestable`.
+                if param.name.as_str().starts_with("impl ") {
+                    return Err(());
+                }
+
+                t
+            }
+
+            _ => t,
+        };
+
+        t.try_super_fold_with(self)
+    }
+
+    fn try_fold_const(&mut self, c: Const<'tcx>) -> Result<Const<'tcx>, ()> {
+        let c = match c.kind() {
+            ConstKind::Infer(InferConst::Var(_)) if self.infer_suggestable => c,
+
+            ConstKind::Infer(..)
+            | ConstKind::Bound(..)
+            | ConstKind::Placeholder(..)
+            | ConstKind::Error(..) => {
+                return Err(());
+            }
+
+            _ => c,
+        };
+
+        c.try_super_fold_with(self)
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(middle_const_not_used_in_type_alias)]
+pub(super) struct ConstNotUsedTraitAlias {
+    pub ct: String,
+    #[primary_span]
+    pub span: Span,
+}
diff --git a/compiler/rustc_middle/src/ty/erase_regions.rs b/compiler/rustc_middle/src/ty/erase_regions.rs
index 9e4f90caa..383773248 100644
--- a/compiler/rustc_middle/src/ty/erase_regions.rs
+++ b/compiler/rustc_middle/src/ty/erase_regions.rs
@@ -1,6 +1,5 @@
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use crate::ty::visit::TypeVisitable;
-use crate::ty::{self, Ty, TyCtxt, TypeFlags};
+use crate::ty::{self, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
 
 pub(super) fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { erase_regions_ty, ..*providers };
@@ -18,7 +17,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// subtyping, but they are anonymized and normalized as well)..
     pub fn erase_regions<T>(self, value: T) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         // If there's nothing to erase avoid performing the query at all
         if !value.has_type_flags(TypeFlags::HAS_LATE_BOUND | TypeFlags::HAS_FREE_REGIONS) {
@@ -35,8 +34,8 @@ struct RegionEraserVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
 }
 
-impl<'tcx> TypeFolder<'tcx> for RegionEraserVisitor<'tcx> {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
@@ -46,7 +45,7 @@ impl<'tcx> TypeFolder<'tcx> for RegionEraserVisitor<'tcx> {
 
     fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let u = self.tcx.anonymize_bound_vars(t);
         u.super_fold_with(self)
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 5d394f71f..9c171a69d 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -1,24 +1,16 @@
-use crate::traits::{ObligationCause, ObligationCauseCode};
-use crate::ty::diagnostics::suggest_constraining_type_param;
-use crate::ty::print::{with_forced_trimmed_paths, FmtPrinter, Printer};
+use crate::ty::print::{with_forced_trimmed_paths, FmtPrinter, PrettyPrinter};
 use crate::ty::{self, BoundRegionKind, Region, Ty, TyCtxt};
-use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
-use rustc_errors::{pluralize, Diagnostic, MultiSpan};
+use rustc_errors::pluralize;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind};
 use rustc_hir::def_id::DefId;
-use rustc_span::symbol::{sym, Symbol};
-use rustc_span::{BytePos, Span};
+use rustc_span::symbol::Symbol;
 use rustc_target::spec::abi;
-
 use std::borrow::Cow;
 use std::collections::hash_map::DefaultHasher;
-use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::path::PathBuf;
 
-use super::print::PrettyPrinter;
-
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable, Lift)]
 pub struct ExpectedFound<T> {
     pub expected: T,
@@ -36,7 +28,7 @@ impl<T> ExpectedFound<T> {
 }
 
 // Data structures used in type unification
-#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift)]
+#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, PartialEq, Eq)]
 #[rustc_pass_by_value]
 pub enum TypeError<'tcx> {
     Mismatch,
@@ -93,20 +85,16 @@ impl TypeError<'_> {
 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
 /// afterwards to present additional details, particularly when it comes to lifetime-related
 /// errors.
-impl<'tcx> fmt::Display for TypeError<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl<'tcx> TypeError<'tcx> {
+    pub fn to_string(self, tcx: TyCtxt<'tcx>) -> Cow<'static, str> {
         use self::TypeError::*;
-        fn report_maybe_different(
-            f: &mut fmt::Formatter<'_>,
-            expected: &str,
-            found: &str,
-        ) -> fmt::Result {
+        fn report_maybe_different(expected: &str, found: &str) -> String {
             // A naive approach to making sure that we're not reporting silly errors such as:
             // (expected closure, found closure).
             if expected == found {
-                write!(f, "expected {}, found a different {}", expected, found)
+                format!("expected {}, found a different {}", expected, found)
             } else {
-                write!(f, "expected {}, found {}", expected, found)
+                format!("expected {}, found {}", expected, found)
             }
         }
 
@@ -115,64 +103,63 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             _ => String::new(),
         };
 
-        match *self {
-            CyclicTy(_) => write!(f, "cyclic type of infinite size"),
-            CyclicConst(_) => write!(f, "encountered a self-referencing constant"),
-            Mismatch => write!(f, "types differ"),
+        match self {
+            CyclicTy(_) => "cyclic type of infinite size".into(),
+            CyclicConst(_) => "encountered a self-referencing constant".into(),
+            Mismatch => "types differ".into(),
             ConstnessMismatch(values) => {
-                write!(f, "expected {} bound, found {} bound", values.expected, values.found)
+                format!("expected {} bound, found {} bound", values.expected, values.found).into()
             }
             PolarityMismatch(values) => {
-                write!(f, "expected {} polarity, found {} polarity", values.expected, values.found)
+                format!("expected {} polarity, found {} polarity", values.expected, values.found)
+                    .into()
             }
             UnsafetyMismatch(values) => {
-                write!(f, "expected {} fn, found {} fn", values.expected, values.found)
+                format!("expected {} fn, found {} fn", values.expected, values.found).into()
             }
             AbiMismatch(values) => {
-                write!(f, "expected {} fn, found {} fn", values.expected, values.found)
+                format!("expected {} fn, found {} fn", values.expected, values.found).into()
             }
-            ArgumentMutability(_) | Mutability => write!(f, "types differ in mutability"),
-            TupleSize(values) => write!(
-                f,
+            ArgumentMutability(_) | Mutability => "types differ in mutability".into(),
+            TupleSize(values) => format!(
                 "expected a tuple with {} element{}, found one with {} element{}",
                 values.expected,
                 pluralize!(values.expected),
                 values.found,
                 pluralize!(values.found)
-            ),
-            FixedArraySize(values) => write!(
-                f,
+            )
+            .into(),
+            FixedArraySize(values) => format!(
                 "expected an array with a fixed size of {} element{}, found one with {} element{}",
                 values.expected,
                 pluralize!(values.expected),
                 values.found,
                 pluralize!(values.found)
-            ),
-            ArgCount => write!(f, "incorrect number of function parameters"),
-            FieldMisMatch(adt, field) => write!(f, "field type mismatch: {}.{}", adt, field),
-            RegionsDoesNotOutlive(..) => write!(f, "lifetime mismatch"),
+            )
+            .into(),
+            ArgCount => "incorrect number of function parameters".into(),
+            FieldMisMatch(adt, field) => format!("field type mismatch: {}.{}", adt, field).into(),
+            RegionsDoesNotOutlive(..) => "lifetime mismatch".into(),
             // Actually naming the region here is a bit confusing because context is lacking
             RegionsInsufficientlyPolymorphic(..) => {
-                write!(f, "one type is more general than the other")
+                "one type is more general than the other".into()
             }
-            RegionsOverlyPolymorphic(br, _) => write!(
-                f,
+            RegionsOverlyPolymorphic(br, _) => format!(
                 "expected concrete lifetime, found bound lifetime parameter{}",
                 br_string(br)
-            ),
-            RegionsPlaceholderMismatch => write!(f, "one type is more general than the other"),
-            ArgumentSorts(values, _) | Sorts(values) => ty::tls::with(|tcx| {
-                let (mut expected, mut found) = with_forced_trimmed_paths!((
-                    values.expected.sort_string(tcx),
-                    values.found.sort_string(tcx),
-                ));
+            )
+            .into(),
+            RegionsPlaceholderMismatch => "one type is more general than the other".into(),
+            ArgumentSorts(values, _) | Sorts(values) => {
+                let mut expected = values.expected.sort_string(tcx);
+                let mut found = values.found.sort_string(tcx);
                 if expected == found {
                     expected = values.expected.sort_string(tcx);
                     found = values.found.sort_string(tcx);
                 }
-                report_maybe_different(f, &expected, &found)
-            }),
-            Traits(values) => ty::tls::with(|tcx| {
+                report_maybe_different(&expected, &found).into()
+            }
+            Traits(values) => {
                 let (mut expected, mut found) = with_forced_trimmed_paths!((
                     tcx.def_path_str(values.expected),
                     tcx.def_path_str(values.found),
@@ -181,12 +168,9 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                     expected = tcx.def_path_str(values.expected);
                     found = tcx.def_path_str(values.found);
                 }
-                report_maybe_different(
-                    f,
-                    &format!("trait `{expected}`"),
-                    &format!("trait `{found}`"),
-                )
-            }),
+                report_maybe_different(&format!("trait `{expected}`"), &format!("trait `{found}`"))
+                    .into()
+            }
             IntMismatch(ref values) => {
                 let expected = match values.expected {
                     ty::IntVarValue::IntType(ty) => ty.name_str(),
@@ -196,43 +180,38 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                     ty::IntVarValue::IntType(ty) => ty.name_str(),
                     ty::IntVarValue::UintType(ty) => ty.name_str(),
                 };
-                write!(f, "expected `{}`, found `{}`", expected, found)
+                format!("expected `{}`, found `{}`", expected, found).into()
             }
-            FloatMismatch(ref values) => {
-                write!(
-                    f,
-                    "expected `{}`, found `{}`",
-                    values.expected.name_str(),
-                    values.found.name_str()
-                )
-            }
-            VariadicMismatch(ref values) => write!(
-                f,
+            FloatMismatch(ref values) => format!(
+                "expected `{}`, found `{}`",
+                values.expected.name_str(),
+                values.found.name_str()
+            )
+            .into(),
+            VariadicMismatch(ref values) => format!(
                 "expected {} fn, found {} function",
                 if values.expected { "variadic" } else { "non-variadic" },
                 if values.found { "variadic" } else { "non-variadic" }
-            ),
-            ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
-                write!(
-                    f,
-                    "expected {}, found {}",
-                    tcx.def_path_str(values.expected),
-                    tcx.def_path_str(values.found)
-                )
-            }),
+            )
+            .into(),
+            ProjectionMismatched(ref values) => format!(
+                "expected `{}`, found `{}`",
+                tcx.def_path_str(values.expected),
+                tcx.def_path_str(values.found)
+            )
+            .into(),
             ExistentialMismatch(ref values) => report_maybe_different(
-                f,
                 &format!("trait `{}`", values.expected),
                 &format!("trait `{}`", values.found),
-            ),
+            )
+            .into(),
             ConstMismatch(ref values) => {
-                write!(f, "expected `{}`, found `{}`", values.expected, values.found)
+                format!("expected `{}`, found `{}`", values.expected, values.found).into()
+            }
+            IntrinsicCast => "cannot coerce intrinsics to function pointers".into(),
+            TargetFeatureCast(_) => {
+                "cannot coerce functions with `#[target_feature]` to safe function pointers".into()
             }
-            IntrinsicCast => write!(f, "cannot coerce intrinsics to function pointers"),
-            TargetFeatureCast(_) => write!(
-                f,
-                "cannot coerce functions with `#[target_feature]` to safe function pointers"
-            ),
         }
     }
 }
@@ -265,60 +244,9 @@ impl<'tcx> TypeError<'tcx> {
 }
 
 impl<'tcx> Ty<'tcx> {
-    pub fn sort_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
+    pub fn sort_string(self, tcx: TyCtxt<'tcx>) -> Cow<'static, str> {
         match *self.kind() {
-            ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => {
-                format!("`{}`", self).into()
-            }
-            ty::Tuple(ref tys) if tys.is_empty() => format!("`{}`", self).into(),
-
-            ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did())).into(),
             ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(),
-            ty::Array(t, n) => {
-                if t.is_simple_ty() {
-                    return format!("array `{}`", self).into();
-                }
-
-                let n = tcx.lift(n).unwrap();
-                if let ty::ConstKind::Value(v) = n.kind() {
-                    if let Some(n) = v.try_to_machine_usize(tcx) {
-                        return format!("array of {} element{}", n, pluralize!(n)).into();
-                    }
-                }
-                "array".into()
-            }
-            ty::Slice(ty) if ty.is_simple_ty() => format!("slice `{}`", self).into(),
-            ty::Slice(_) => "slice".into(),
-            ty::RawPtr(tymut) => {
-                let tymut_string = match tymut.mutbl {
-                    hir::Mutability::Mut => tymut.to_string(),
-                    hir::Mutability::Not => format!("const {}", tymut.ty),
-                };
-
-                if tymut_string != "_" && (tymut.ty.is_simple_text() || tymut_string.len() < "const raw pointer".len()) {
-                    format!("`*{}`", tymut_string).into()
-                } else {
-                    // Unknown type name, it's long or has type arguments
-                    "raw pointer".into()
-                }
-            },
-            ty::Ref(_, ty, mutbl) => {
-                let tymut = ty::TypeAndMut { ty, mutbl };
-                let tymut_string = tymut.to_string();
-
-                if tymut_string != "_"
-                    && (ty.is_simple_text() || tymut_string.len() < "mutable reference".len())
-                {
-                    format!("`&{}`", tymut_string).into()
-                } else {
-                    // Unknown type name, it's long or has type arguments
-                    match mutbl {
-                        hir::Mutability::Mut => "mutable reference",
-                        _ => "reference",
-                    }
-                    .into()
-                }
-            }
             ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
                 DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
                 DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
@@ -326,13 +254,13 @@ impl<'tcx> Ty<'tcx> {
             },
             ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(ref inner, ..) if let Some(principal) = inner.principal() => {
-                format!("trait object `dyn {}`", tcx.def_path_str(principal.def_id())).into()
+                format!("`dyn {}`", tcx.def_path_str(principal.def_id())).into()
             }
             ty::Dynamic(..) => "trait object".into(),
             ty::Closure(..) => "closure".into(),
             ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
-            ty::GeneratorWitness(..) => "generator witness".into(),
-            ty::Tuple(..) => "tuple".into(),
+            ty::GeneratorWitness(..) |
+            ty::GeneratorWitnessMIR(..) => "generator witness".into(),
             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
             ty::Infer(ty::IntVar(_)) => "integer".into(),
             ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
@@ -342,9 +270,14 @@ impl<'tcx> Ty<'tcx> {
             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
             ty::Alias(ty::Projection, _) => "associated type".into(),
-            ty::Param(p) => format!("type parameter `{}`", p).into(),
-            ty::Alias(ty::Opaque, ..) => "opaque type".into(),
+            ty::Param(p) => format!("type parameter `{p}`").into(),
+            ty::Alias(ty::Opaque, ..) => if tcx.ty_is_opaque_future(self) { "future".into() } else { "opaque type".into() },
             ty::Error(_) => "type error".into(),
+            _ => {
+                let width = tcx.sess.diagnostic_width();
+                let length_limit = std::cmp::max(width / 4, 15);
+                format!("`{}`", tcx.ty_string_with_limit(self, length_limit)).into()
+            }
         }
     }
 
@@ -379,7 +312,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Dynamic(..) => "trait object".into(),
             ty::Closure(..) => "closure".into(),
             ty::Generator(def_id, ..) => tcx.generator_kind(def_id).unwrap().descr().into(),
-            ty::GeneratorWitness(..) => "generator witness".into(),
+            ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => "generator witness".into(),
             ty::Tuple(..) => "tuple".into(),
             ty::Placeholder(..) => "higher-ranked type".into(),
             ty::Bound(..) => "bound type variable".into(),
@@ -391,630 +324,14 @@ impl<'tcx> Ty<'tcx> {
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    pub fn note_and_explain_type_err(
-        self,
-        diag: &mut Diagnostic,
-        err: TypeError<'tcx>,
-        cause: &ObligationCause<'tcx>,
-        sp: Span,
-        body_owner_def_id: DefId,
-    ) {
-        use self::TypeError::*;
-        debug!("note_and_explain_type_err err={:?} cause={:?}", err, cause);
-        match err {
-            ArgumentSorts(values, _) | Sorts(values) => {
-                match (values.expected.kind(), values.found.kind()) {
-                    (ty::Closure(..), ty::Closure(..)) => {
-                        diag.note("no two closures, even if identical, have the same type");
-                        diag.help("consider boxing your closure and/or using it as a trait object");
-                    }
-                    (ty::Alias(ty::Opaque, ..), ty::Alias(ty::Opaque, ..)) => {
-                        // Issue #63167
-                        diag.note("distinct uses of `impl Trait` result in different opaque types");
-                    }
-                    (ty::Float(_), ty::Infer(ty::IntVar(_)))
-                        if let Ok(
-                            // Issue #53280
-                            snippet,
-                        ) = self.sess.source_map().span_to_snippet(sp) =>
-                    {
-                        if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
-                            diag.span_suggestion(
-                                sp,
-                                "use a float literal",
-                                format!("{}.0", snippet),
-                                MachineApplicable,
-                            );
-                        }
-                    }
-                    (ty::Param(expected), ty::Param(found)) => {
-                        let generics = self.generics_of(body_owner_def_id);
-                        let e_span = self.def_span(generics.type_param(expected, self).def_id);
-                        if !sp.contains(e_span) {
-                            diag.span_label(e_span, "expected type parameter");
-                        }
-                        let f_span = self.def_span(generics.type_param(found, self).def_id);
-                        if !sp.contains(f_span) {
-                            diag.span_label(f_span, "found type parameter");
-                        }
-                        diag.note(
-                            "a type parameter was expected, but a different one was found; \
-                             you might be missing a type parameter or trait bound",
-                        );
-                        diag.note(
-                            "for more information, visit \
-                             https://doc.rust-lang.org/book/ch10-02-traits.html\
-                             #traits-as-parameters",
-                        );
-                    }
-                    (ty::Alias(ty::Projection, _), ty::Alias(ty::Projection, _)) => {
-                        diag.note("an associated type was expected, but a different one was found");
-                    }
-                    (ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p))
-                        if self.def_kind(proj.def_id) != DefKind::ImplTraitPlaceholder =>
-                    {
-                        let generics = self.generics_of(body_owner_def_id);
-                        let p_span = self.def_span(generics.type_param(p, self).def_id);
-                        if !sp.contains(p_span) {
-                            diag.span_label(p_span, "this type parameter");
-                        }
-                        let hir = self.hir();
-                        let mut note = true;
-                        if let Some(generics) = generics
-                            .type_param(p, self)
-                            .def_id
-                            .as_local()
-                            .map(|id| hir.local_def_id_to_hir_id(id))
-                            .and_then(|id| self.hir().find_parent(id))
-                            .as_ref()
-                            .and_then(|node| node.generics())
-                        {
-                            // Synthesize the associated type restriction `Add<Output = Expected>`.
-                            // FIXME: extract this logic for use in other diagnostics.
-                            let (trait_ref, assoc_substs) = proj.trait_ref_and_own_substs(self);
-                            let path =
-                                self.def_path_str_with_substs(trait_ref.def_id, trait_ref.substs);
-                            let item_name = self.item_name(proj.def_id);
-                            let item_args = self.format_generic_args(assoc_substs);
-
-                            let path = if path.ends_with('>') {
-                                format!(
-                                    "{}, {}{} = {}>",
-                                    &path[..path.len() - 1],
-                                    item_name,
-                                    item_args,
-                                    p
-                                )
-                            } else {
-                                format!("{}<{}{} = {}>", path, item_name, item_args, p)
-                            };
-                            note = !suggest_constraining_type_param(
-                                self,
-                                generics,
-                                diag,
-                                &format!("{}", proj.self_ty()),
-                                &path,
-                                None,
-                            );
-                        }
-                        if note {
-                            diag.note("you might be missing a type parameter or trait bound");
-                        }
-                    }
-                    (ty::Param(p), ty::Dynamic(..) | ty::Alias(ty::Opaque, ..))
-                    | (ty::Dynamic(..) | ty::Alias(ty::Opaque, ..), ty::Param(p)) => {
-                        let generics = self.generics_of(body_owner_def_id);
-                        let p_span = self.def_span(generics.type_param(p, self).def_id);
-                        if !sp.contains(p_span) {
-                            diag.span_label(p_span, "this type parameter");
-                        }
-                        diag.help("type parameters must be constrained to match other types");
-                        if self.sess.teach(&diag.get_code().unwrap()) {
-                            diag.help(
-                                "given a type parameter `T` and a method `foo`:
-```
-trait Trait<T> { fn foo(&self) -> T; }
-```
-the only ways to implement method `foo` are:
-- constrain `T` with an explicit type:
-```
-impl Trait<String> for X {
-    fn foo(&self) -> String { String::new() }
-}
-```
-- add a trait bound to `T` and call a method on that trait that returns `Self`:
-```
-impl<T: std::default::Default> Trait<T> for X {
-    fn foo(&self) -> T { <T as std::default::Default>::default() }
-}
-```
-- change `foo` to return an argument of type `T`:
-```
-impl<T> Trait<T> for X {
-    fn foo(&self, x: T) -> T { x }
-}
-```",
-                            );
-                        }
-                        diag.note(
-                            "for more information, visit \
-                             https://doc.rust-lang.org/book/ch10-02-traits.html\
-                             #traits-as-parameters",
-                        );
-                    }
-                    (ty::Param(p), ty::Closure(..) | ty::Generator(..)) => {
-                        let generics = self.generics_of(body_owner_def_id);
-                        let p_span = self.def_span(generics.type_param(p, self).def_id);
-                        if !sp.contains(p_span) {
-                            diag.span_label(p_span, "this type parameter");
-                        }
-                        diag.help(&format!(
-                            "every closure has a distinct type and so could not always match the \
-                             caller-chosen type of parameter `{}`",
-                            p
-                        ));
-                    }
-                    (ty::Param(p), _) | (_, ty::Param(p)) => {
-                        let generics = self.generics_of(body_owner_def_id);
-                        let p_span = self.def_span(generics.type_param(p, self).def_id);
-                        if !sp.contains(p_span) {
-                            diag.span_label(p_span, "this type parameter");
-                        }
-                    }
-                    (ty::Alias(ty::Projection, proj_ty), _) if self.def_kind(proj_ty.def_id) != DefKind::ImplTraitPlaceholder => {
-                        self.expected_projection(
-                            diag,
-                            proj_ty,
-                            values,
-                            body_owner_def_id,
-                            cause.code(),
-                        );
-                    }
-                    (_, ty::Alias(ty::Projection, proj_ty)) if self.def_kind(proj_ty.def_id) != DefKind::ImplTraitPlaceholder => {
-                        let msg = format!(
-                            "consider constraining the associated type `{}` to `{}`",
-                            values.found, values.expected,
-                        );
-                        if !(self.suggest_constraining_opaque_associated_type(
-                            diag,
-                            &msg,
-                            proj_ty,
-                            values.expected,
-                        ) || self.suggest_constraint(
-                            diag,
-                            &msg,
-                            body_owner_def_id,
-                            proj_ty,
-                            values.expected,
-                        )) {
-                            diag.help(&msg);
-                            diag.note(
-                                "for more information, visit \
-                                https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
-                            );
-                        }
-                    }
-                    _ => {}
-                }
-                debug!(
-                    "note_and_explain_type_err expected={:?} ({:?}) found={:?} ({:?})",
-                    values.expected,
-                    values.expected.kind(),
-                    values.found,
-                    values.found.kind(),
-                );
-            }
-            CyclicTy(ty) => {
-                // Watch out for various cases of cyclic types and try to explain.
-                if ty.is_closure() || ty.is_generator() {
-                    diag.note(
-                        "closures cannot capture themselves or take themselves as argument;\n\
-                         this error may be the result of a recent compiler bug-fix,\n\
-                         see issue #46062 <https://github.com/rust-lang/rust/issues/46062>\n\
-                         for more information",
-                    );
-                }
-            }
-            TargetFeatureCast(def_id) => {
-                let target_spans =
-                    self.get_attrs(def_id, sym::target_feature).map(|attr| attr.span);
-                diag.note(
-                    "functions with `#[target_feature]` can only be coerced to `unsafe` function pointers"
-                );
-                diag.span_labels(target_spans, "`#[target_feature]` added here");
-            }
-            _ => {}
-        }
-    }
-
-    fn suggest_constraint(
-        self,
-        diag: &mut Diagnostic,
-        msg: &str,
-        body_owner_def_id: DefId,
-        proj_ty: &ty::AliasTy<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> bool {
-        let assoc = self.associated_item(proj_ty.def_id);
-        let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(self);
-        if let Some(item) = self.hir().get_if_local(body_owner_def_id) {
-            if let Some(hir_generics) = item.generics() {
-                // Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`.
-                // This will also work for `impl Trait`.
-                let def_id = if let ty::Param(param_ty) = proj_ty.self_ty().kind() {
-                    let generics = self.generics_of(body_owner_def_id);
-                    generics.type_param(param_ty, self).def_id
-                } else {
-                    return false;
-                };
-                let Some(def_id) = def_id.as_local() else {
-                    return false;
-                };
-
-                // First look in the `where` clause, as this might be
-                // `fn foo<T>(x: T) where T: Trait`.
-                for pred in hir_generics.bounds_for_param(def_id) {
-                    if self.constrain_generic_bound_associated_type_structured_suggestion(
-                        diag,
-                        &trait_ref,
-                        pred.bounds,
-                        &assoc,
-                        assoc_substs,
-                        ty,
-                        msg,
-                        false,
-                    ) {
-                        return true;
-                    }
-                }
-            }
-        }
-        false
-    }
-
-    /// An associated type was expected and a different type was found.
-    ///
-    /// We perform a few different checks to see what we can suggest:
-    ///
-    ///  - In the current item, look for associated functions that return the expected type and
-    ///    suggest calling them. (Not a structured suggestion.)
-    ///  - If any of the item's generic bounds can be constrained, we suggest constraining the
-    ///    associated type to the found type.
-    ///  - If the associated type has a default type and was expected inside of a `trait`, we
-    ///    mention that this is disallowed.
-    ///  - If all other things fail, and the error is not because of a mismatch between the `trait`
-    ///    and the `impl`, we provide a generic `help` to constrain the assoc type or call an assoc
-    ///    fn that returns the type.
-    fn expected_projection(
-        self,
-        diag: &mut Diagnostic,
-        proj_ty: &ty::AliasTy<'tcx>,
-        values: ExpectedFound<Ty<'tcx>>,
-        body_owner_def_id: DefId,
-        cause_code: &ObligationCauseCode<'_>,
-    ) {
-        let msg = format!(
-            "consider constraining the associated type `{}` to `{}`",
-            values.expected, values.found
-        );
-        let body_owner = self.hir().get_if_local(body_owner_def_id);
-        let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name);
-
-        // We don't want to suggest calling an assoc fn in a scope where that isn't feasible.
-        let callable_scope = matches!(
-            body_owner,
-            Some(
-                hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(..), .. })
-                    | hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
-                    | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }),
-            )
-        );
-        let impl_comparison =
-            matches!(cause_code, ObligationCauseCode::CompareImplItemObligation { .. });
-        let assoc = self.associated_item(proj_ty.def_id);
-        if !callable_scope || impl_comparison {
-            // We do not want to suggest calling functions when the reason of the
-            // type error is a comparison of an `impl` with its `trait` or when the
-            // scope is outside of a `Body`.
-        } else {
-            // If we find a suitable associated function that returns the expected type, we don't
-            // want the more general suggestion later in this method about "consider constraining
-            // the associated type or calling a method that returns the associated type".
-            let point_at_assoc_fn = self.point_at_methods_that_satisfy_associated_type(
-                diag,
-                assoc.container_id(self),
-                current_method_ident,
-                proj_ty.def_id,
-                values.expected,
-            );
-            // Possibly suggest constraining the associated type to conform to the
-            // found type.
-            if self.suggest_constraint(diag, &msg, body_owner_def_id, proj_ty, values.found)
-                || point_at_assoc_fn
-            {
-                return;
-            }
-        }
-
-        self.suggest_constraining_opaque_associated_type(diag, &msg, proj_ty, values.found);
-
-        if self.point_at_associated_type(diag, body_owner_def_id, values.found) {
-            return;
-        }
-
-        if !impl_comparison {
-            // Generic suggestion when we can't be more specific.
-            if callable_scope {
-                diag.help(&format!(
-                    "{} or calling a method that returns `{}`",
-                    msg, values.expected
-                ));
-            } else {
-                diag.help(&msg);
-            }
-            diag.note(
-                "for more information, visit \
-                 https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
-            );
-        }
-        if self.sess.teach(&diag.get_code().unwrap()) {
-            diag.help(
-                "given an associated type `T` and a method `foo`:
-```
-trait Trait {
-type T;
-fn foo(&self) -> Self::T;
-}
-```
-the only way of implementing method `foo` is to constrain `T` with an explicit associated type:
-```
-impl Trait for X {
-type T = String;
-fn foo(&self) -> Self::T { String::new() }
-}
-```",
-            );
-        }
-    }
-
-    /// When the expected `impl Trait` is not defined in the current item, it will come from
-    /// a return type. This can occur when dealing with `TryStream` (#71035).
-    fn suggest_constraining_opaque_associated_type(
-        self,
-        diag: &mut Diagnostic,
-        msg: &str,
-        proj_ty: &ty::AliasTy<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> bool {
-        let assoc = self.associated_item(proj_ty.def_id);
-        if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *proj_ty.self_ty().kind() {
-            let opaque_local_def_id = def_id.as_local();
-            let opaque_hir_ty = if let Some(opaque_local_def_id) = opaque_local_def_id {
-                match &self.hir().expect_item(opaque_local_def_id).kind {
-                    hir::ItemKind::OpaqueTy(opaque_hir_ty) => opaque_hir_ty,
-                    _ => bug!("The HirId comes from a `ty::Opaque`"),
-                }
-            } else {
-                return false;
-            };
-
-            let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(self);
-
-            self.constrain_generic_bound_associated_type_structured_suggestion(
-                diag,
-                &trait_ref,
-                opaque_hir_ty.bounds,
-                assoc,
-                assoc_substs,
-                ty,
-                msg,
-                true,
-            )
-        } else {
-            false
-        }
-    }
-
-    fn point_at_methods_that_satisfy_associated_type(
-        self,
-        diag: &mut Diagnostic,
-        assoc_container_id: DefId,
-        current_method_ident: Option<Symbol>,
-        proj_ty_item_def_id: DefId,
-        expected: Ty<'tcx>,
-    ) -> bool {
-        let items = self.associated_items(assoc_container_id);
-        // Find all the methods in the trait that could be called to construct the
-        // expected associated type.
-        // FIXME: consider suggesting the use of associated `const`s.
-        let methods: Vec<(Span, String)> = items
-            .items
-            .iter()
-            .filter(|(name, item)| {
-                ty::AssocKind::Fn == item.kind && Some(**name) != current_method_ident
-            })
-            .filter_map(|(_, item)| {
-                let method = self.fn_sig(item.def_id);
-                match *method.output().skip_binder().kind() {
-                    ty::Alias(ty::Projection, ty::AliasTy { def_id: item_def_id, .. })
-                        if item_def_id == proj_ty_item_def_id =>
-                    {
-                        Some((
-                            self.def_span(item.def_id),
-                            format!("consider calling `{}`", self.def_path_str(item.def_id)),
-                        ))
-                    }
-                    _ => None,
-                }
-            })
-            .collect();
-        if !methods.is_empty() {
-            // Use a single `help:` to show all the methods in the trait that can
-            // be used to construct the expected associated type.
-            let mut span: MultiSpan =
-                methods.iter().map(|(sp, _)| *sp).collect::<Vec<Span>>().into();
-            let msg = format!(
-                "{some} method{s} {are} available that return{r} `{ty}`",
-                some = if methods.len() == 1 { "a" } else { "some" },
-                s = pluralize!(methods.len()),
-                are = pluralize!("is", methods.len()),
-                r = if methods.len() == 1 { "s" } else { "" },
-                ty = expected
-            );
-            for (sp, label) in methods.into_iter() {
-                span.push_span_label(sp, label);
-            }
-            diag.span_help(span, &msg);
-            return true;
-        }
-        false
-    }
-
-    fn point_at_associated_type(
-        self,
-        diag: &mut Diagnostic,
-        body_owner_def_id: DefId,
-        found: Ty<'tcx>,
-    ) -> bool {
-        let Some(hir_id) = body_owner_def_id.as_local() else {
-            return false;
-        };
-        let hir_id = self.hir().local_def_id_to_hir_id(hir_id);
-        // When `body_owner` is an `impl` or `trait` item, look in its associated types for
-        // `expected` and point at it.
-        let parent_id = self.hir().get_parent_item(hir_id);
-        let item = self.hir().find_by_def_id(parent_id.def_id);
-        debug!("expected_projection parent item {:?}", item);
-        match item {
-            Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Trait(.., items), .. })) => {
-                // FIXME: account for `#![feature(specialization)]`
-                for item in &items[..] {
-                    match item.kind {
-                        hir::AssocItemKind::Type => {
-                            // FIXME: account for returning some type in a trait fn impl that has
-                            // an assoc type as a return type (#72076).
-                            if let hir::Defaultness::Default { has_value: true } =
-                                self.impl_defaultness(item.id.owner_id)
-                            {
-                                if self.type_of(item.id.owner_id) == found {
-                                    diag.span_label(
-                                        item.span,
-                                        "associated type defaults can't be assumed inside the \
-                                            trait defining them",
-                                    );
-                                    return true;
-                                }
-                            }
-                        }
-                        _ => {}
-                    }
-                }
-            }
-            Some(hir::Node::Item(hir::Item {
-                kind: hir::ItemKind::Impl(hir::Impl { items, .. }),
-                ..
-            })) => {
-                for item in &items[..] {
-                    if let hir::AssocItemKind::Type = item.kind {
-                        if self.type_of(item.id.owner_id) == found {
-                            diag.span_label(item.span, "expected this associated type");
-                            return true;
-                        }
-                    }
-                }
-            }
-            _ => {}
-        }
-        false
-    }
-
-    /// Given a slice of `hir::GenericBound`s, if any of them corresponds to the `trait_ref`
-    /// requirement, provide a structured suggestion to constrain it to a given type `ty`.
-    ///
-    /// `is_bound_surely_present` indicates whether we know the bound we're looking for is
-    /// inside `bounds`. If that's the case then we can consider `bounds` containing only one
-    /// trait bound as the one we're looking for. This can help in cases where the associated
-    /// type is defined on a supertrait of the one present in the bounds.
-    fn constrain_generic_bound_associated_type_structured_suggestion(
-        self,
-        diag: &mut Diagnostic,
-        trait_ref: &ty::TraitRef<'tcx>,
-        bounds: hir::GenericBounds<'_>,
-        assoc: &ty::AssocItem,
-        assoc_substs: &[ty::GenericArg<'tcx>],
-        ty: Ty<'tcx>,
-        msg: &str,
-        is_bound_surely_present: bool,
-    ) -> bool {
-        // FIXME: we would want to call `resolve_vars_if_possible` on `ty` before suggesting.
-
-        let trait_bounds = bounds.iter().filter_map(|bound| match bound {
-            hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::None) => Some(ptr),
-            _ => None,
-        });
-
-        let matching_trait_bounds = trait_bounds
-            .clone()
-            .filter(|ptr| ptr.trait_ref.trait_def_id() == Some(trait_ref.def_id))
-            .collect::<Vec<_>>();
-
-        let span = match &matching_trait_bounds[..] {
-            &[ptr] => ptr.span,
-            &[] if is_bound_surely_present => match &trait_bounds.collect::<Vec<_>>()[..] {
-                &[ptr] => ptr.span,
-                _ => return false,
-            },
-            _ => return false,
-        };
-
-        self.constrain_associated_type_structured_suggestion(
-            diag,
-            span,
-            assoc,
-            assoc_substs,
-            ty,
-            msg,
-        )
-    }
-
-    /// Given a span corresponding to a bound, provide a structured suggestion to set an
-    /// associated type to a given type `ty`.
-    fn constrain_associated_type_structured_suggestion(
-        self,
-        diag: &mut Diagnostic,
-        span: Span,
-        assoc: &ty::AssocItem,
-        assoc_substs: &[ty::GenericArg<'tcx>],
-        ty: Ty<'tcx>,
-        msg: &str,
-    ) -> bool {
-        if let Ok(has_params) =
-            self.sess.source_map().span_to_snippet(span).map(|snippet| snippet.ends_with('>'))
-        {
-            let (span, sugg) = if has_params {
-                let pos = span.hi() - BytePos(1);
-                let span = Span::new(pos, pos, span.ctxt(), span.parent());
-                (span, format!(", {} = {}", assoc.ident(self), ty))
-            } else {
-                let item_args = self.format_generic_args(assoc_substs);
-                (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(self), item_args, ty))
-            };
-            diag.span_suggestion_verbose(span, msg, sugg, MaybeIncorrect);
-            return true;
-        }
-        false
-    }
-
-    pub fn short_ty_string(self, ty: Ty<'tcx>) -> (String, Option<PathBuf>) {
-        let width = self.sess.diagnostic_width();
-        let length_limit = width.saturating_sub(30);
+    pub fn ty_string_with_limit(self, ty: Ty<'tcx>, length_limit: usize) -> String {
         let mut type_limit = 50;
         let regular = FmtPrinter::new(self, hir::def::Namespace::TypeNS)
             .pretty_print_type(ty)
             .expect("could not write to `String`")
             .into_buffer();
-        if regular.len() <= width {
-            return (regular, None);
+        if regular.len() <= length_limit {
+            return regular;
         }
         let mut short;
         loop {
@@ -1034,6 +351,20 @@ fn foo(&self) -> Self::T { String::new() }
             }
             type_limit -= 1;
         }
+        short
+    }
+
+    pub fn short_ty_string(self, ty: Ty<'tcx>) -> (String, Option<PathBuf>) {
+        let width = self.sess.diagnostic_width();
+        let length_limit = width.saturating_sub(30);
+        let regular = FmtPrinter::new(self, hir::def::Namespace::TypeNS)
+            .pretty_print_type(ty)
+            .expect("could not write to `String`")
+            .into_buffer();
+        if regular.len() <= width {
+            return (regular, None);
+        }
+        let short = self.ty_string_with_limit(ty, length_limit);
         if regular == short {
             return (regular, None);
         }
@@ -1047,11 +378,4 @@ fn foo(&self) -> Self::T { String::new() }
             Err(_) => (regular, None),
         }
     }
-
-    fn format_generic_args(self, args: &[ty::GenericArg<'tcx>]) -> String {
-        FmtPrinter::new(self, hir::def::Namespace::TypeNS)
-            .path_generic_args(Ok, args)
-            .expect("could not write to `String`.")
-            .into_buffer()
-    }
 }
diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index f785fb5c4..59deade0a 100644
--- a/compiler/rustc_middle/src/ty/fast_reject.rs
+++ b/compiler/rustc_middle/src/ty/fast_reject.rs
@@ -1,6 +1,6 @@
 use crate::mir::Mutability;
 use crate::ty::subst::GenericArgKind;
-use crate::ty::{self, Ty, TyCtxt, TypeVisitable};
+use crate::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_hir::def_id::DefId;
 use std::fmt::Debug;
 use std::hash::Hash;
@@ -32,6 +32,7 @@ pub enum SimplifiedType {
     ClosureSimplifiedType(DefId),
     GeneratorSimplifiedType(DefId),
     GeneratorWitnessSimplifiedType(usize),
+    GeneratorWitnessMIRSimplifiedType(DefId),
     FunctionSimplifiedType(usize),
     PlaceholderSimplifiedType,
 }
@@ -108,6 +109,7 @@ pub fn simplify_type<'tcx>(
         ty::FnDef(def_id, _) | ty::Closure(def_id, _) => Some(ClosureSimplifiedType(def_id)),
         ty::Generator(def_id, _, _) => Some(GeneratorSimplifiedType(def_id)),
         ty::GeneratorWitness(tys) => Some(GeneratorWitnessSimplifiedType(tys.skip_binder().len())),
+        ty::GeneratorWitnessMIR(def_id, _) => Some(GeneratorWitnessMIRSimplifiedType(def_id)),
         ty::Never => Some(NeverSimplifiedType),
         ty::Tuple(tys) => Some(TupleSimplifiedType(tys.len())),
         ty::FnPtr(f) => Some(FunctionSimplifiedType(f.skip_binder().inputs().len())),
@@ -139,7 +141,8 @@ impl SimplifiedType {
             | ForeignSimplifiedType(d)
             | TraitSimplifiedType(d)
             | ClosureSimplifiedType(d)
-            | GeneratorSimplifiedType(d) => Some(d),
+            | GeneratorSimplifiedType(d)
+            | GeneratorWitnessMIRSimplifiedType(d) => Some(d),
             _ => None,
         }
     }
@@ -208,6 +211,7 @@ impl DeepRejectCtxt {
             | ty::Closure(..)
             | ty::Generator(..)
             | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Placeholder(..)
             | ty::Bound(..)
             | ty::Infer(_) => bug!("unexpected impl_ty: {impl_ty}"),
@@ -286,7 +290,7 @@ impl DeepRejectCtxt {
             // Impls cannot contain these types as these cannot be named directly.
             ty::FnDef(..) | ty::Closure(..) | ty::Generator(..) => false,
 
-            ty::Placeholder(..) => false,
+            ty::Placeholder(..) | ty::Bound(..) => false,
 
             // Depending on the value of `treat_obligation_params`, we either
             // treat generic parameters like placeholders or like inference variables.
@@ -306,7 +310,7 @@ impl DeepRejectCtxt {
 
             ty::Error(_) => true,
 
-            ty::GeneratorWitness(..) | ty::Bound(..) => {
+            ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => {
                 bug!("unexpected obligation type: {:?}", obligation_ty)
             }
         }
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index b7eafc4b4..91241ff40 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -125,6 +125,16 @@ impl FlagComputation {
                 self.bound_computation(ts, |flags, ts| flags.add_tys(ts));
             }
 
+            ty::GeneratorWitnessMIR(_, substs) => {
+                let should_remove_further_specializable =
+                    !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
+                self.add_substs(substs);
+                if should_remove_further_specializable {
+                    self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
+                }
+                self.add_flags(TypeFlags::HAS_TY_GENERATOR);
+            }
+
             &ty::Closure(_, substs) => {
                 let substs = substs.as_closure();
                 let should_remove_further_specializable =
@@ -241,6 +251,10 @@ impl FlagComputation {
                 self.add_ty(ty);
                 self.add_region(region);
             }
+            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(ct, ty)) => {
+                self.add_const(ct);
+                self.add_ty(ty);
+            }
             ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
                 self.add_ty(a);
                 self.add_ty(b);
@@ -254,10 +268,7 @@ impl FlagComputation {
                 term,
             })) => {
                 self.add_projection_ty(projection_ty);
-                match term.unpack() {
-                    ty::TermKind::Ty(ty) => self.add_ty(ty),
-                    ty::TermKind::Const(c) => self.add_const(c),
-                }
+                self.add_term(term);
             }
             ty::PredicateKind::WellFormed(arg) => {
                 self.add_substs(slice::from_ref(&arg));
@@ -277,6 +288,10 @@ impl FlagComputation {
                 self.add_ty(ty);
             }
             ty::PredicateKind::Ambiguous => {}
+            ty::PredicateKind::AliasEq(t1, t2) => {
+                self.add_term(t1);
+                self.add_term(t2);
+            }
         }
     }
 
@@ -370,4 +385,11 @@ impl FlagComputation {
             }
         }
     }
+
+    fn add_term(&mut self, term: ty::Term<'_>) {
+        match term.unpack() {
+            ty::TermKind::Ty(ty) => self.add_ty(ty),
+            ty::TermKind::Const(ct) => self.add_const(ct),
+        }
+    }
 }
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 6b9a37d84..d66f436f9 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -1,210 +1,10 @@
-//! A folding traversal mechanism for complex data structures that contain type
-//! information.
-//!
-//! This is a modifying traversal. It consumes the data structure, producing a
-//! (possibly) modified version of it. Both fallible and infallible versions are
-//! available. The name is potentially confusing, because this traversal is more
-//! like `Iterator::map` than `Iterator::fold`.
-//!
-//! This traversal has limited flexibility. Only a small number of "types of
-//! interest" within the complex data structures can receive custom
-//! modification. These are the ones containing the most important type-related
-//! information, such as `Ty`, `Predicate`, `Region`, and `Const`.
-//!
-//! There are three groups of traits involved in each traversal.
-//! - `TypeFoldable`. This is implemented once for many types, including:
-//!   - Types of interest, for which the methods delegate to the folder.
-//!   - All other types, including generic containers like `Vec` and `Option`.
-//!     It defines a "skeleton" of how they should be folded.
-//! - `TypeSuperFoldable`. This is implemented only for each type of interest,
-//!   and defines the folding "skeleton" for these types.
-//! - `TypeFolder`/`FallibleTypeFolder. One of these is implemented for each
-//!   folder. This defines how types of interest are folded.
-//!
-//! This means each fold is a mixture of (a) generic folding operations, and (b)
-//! custom fold operations that are specific to the folder.
-//! - The `TypeFoldable` impls handle most of the traversal, and call into
-//!   `TypeFolder`/`FallibleTypeFolder` when they encounter a type of interest.
-//! - A `TypeFolder`/`FallibleTypeFolder` may call into another `TypeFoldable`
-//!   impl, because some of the types of interest are recursive and can contain
-//!   other types of interest.
-//! - A `TypeFolder`/`FallibleTypeFolder` may also call into a `TypeSuperFoldable`
-//!   impl, because each folder might provide custom handling only for some types
-//!   of interest, or only for some variants of each type of interest, and then
-//!   use default traversal for the remaining cases.
-//!
-//! For example, if you have `struct S(Ty, U)` where `S: TypeFoldable` and `U:
-//! TypeFoldable`, and an instance `s = S(ty, u)`, it would be folded like so:
-//! ```text
-//! s.fold_with(folder) calls
-//! - ty.fold_with(folder) calls
-//!   - folder.fold_ty(ty) may call
-//!     - ty.super_fold_with(folder)
-//! - u.fold_with(folder)
-//! ```
-use crate::ty::{self, Binder, BoundTy, Ty, TyCtxt, TypeVisitable};
+use crate::ty::{self, Binder, BoundTy, Ty, TyCtxt, TypeVisitableExt};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir::def_id::DefId;
 
 use std::collections::BTreeMap;
 
-/// This trait is implemented for every type that can be folded,
-/// providing the skeleton of the traversal.
-///
-/// To implement this conveniently, use the derive macro located in
-/// `rustc_macros`.
-pub trait TypeFoldable<'tcx>: TypeVisitable<'tcx> {
-    /// The entry point for folding. To fold a value `t` with a folder `f`
-    /// call: `t.try_fold_with(f)`.
-    ///
-    /// For most types, this just traverses the value, calling `try_fold_with`
-    /// on each field/element.
-    ///
-    /// For types of interest (such as `Ty`), the implementation of method
-    /// calls a folder method specifically for that type (such as
-    /// `F::try_fold_ty`). This is where control transfers from `TypeFoldable`
-    /// to `TypeFolder`.
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error>;
-
-    /// A convenient alternative to `try_fold_with` for use with infallible
-    /// folders. Do not override this method, to ensure coherence with
-    /// `try_fold_with`.
-    fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
-        self.try_fold_with(folder).into_ok()
-    }
-}
-
-// This trait is implemented for types of interest.
-pub trait TypeSuperFoldable<'tcx>: TypeFoldable<'tcx> {
-    /// Provides a default fold for a type of interest. This should only be
-    /// called within `TypeFolder` methods, when a non-custom traversal is
-    /// desired for the value of the type of interest passed to that method.
-    /// For example, in `MyFolder::try_fold_ty(ty)`, it is valid to call
-    /// `ty.try_super_fold_with(self)`, but any other folding should be done
-    /// with `xyz.try_fold_with(self)`.
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
-        self,
-        folder: &mut F,
-    ) -> Result<Self, F::Error>;
-
-    /// A convenient alternative to `try_super_fold_with` for use with
-    /// infallible folders. Do not override this method, to ensure coherence
-    /// with `try_super_fold_with`.
-    fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
-        self.try_super_fold_with(folder).into_ok()
-    }
-}
-
-/// This trait is implemented for every infallible folding traversal. There is
-/// a fold method defined for every type of interest. Each such method has a
-/// default that does an "identity" fold. Implementations of these methods
-/// often fall back to a `super_fold_with` method if the primary argument
-/// doesn't satisfy a particular condition.
-///
-/// A blanket implementation of [`FallibleTypeFolder`] will defer to
-/// the infallible methods of this trait to ensure that the two APIs
-/// are coherent.
-pub trait TypeFolder<'tcx>: FallibleTypeFolder<'tcx, Error = !> {
-    fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
-
-    fn fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T>
-    where
-        T: TypeFoldable<'tcx>,
-    {
-        t.super_fold_with(self)
-    }
-
-    fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        t.super_fold_with(self)
-    }
-
-    fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        r.super_fold_with(self)
-    }
-
-    fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
-        c.super_fold_with(self)
-    }
-
-    fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
-        p.super_fold_with(self)
-    }
-}
-
-/// This trait is implemented for every folding traversal. There is a fold
-/// method defined for every type of interest. Each such method has a default
-/// that does an "identity" fold.
-///
-/// A blanket implementation of this trait (that defers to the relevant
-/// method of [`TypeFolder`]) is provided for all infallible folders in
-/// order to ensure the two APIs are coherent.
-pub trait FallibleTypeFolder<'tcx>: Sized {
-    type Error;
-
-    fn tcx<'a>(&'a self) -> TyCtxt<'tcx>;
-
-    fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error>
-    where
-        T: TypeFoldable<'tcx>,
-    {
-        t.try_super_fold_with(self)
-    }
-
-    fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        t.try_super_fold_with(self)
-    }
-
-    fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
-        r.try_super_fold_with(self)
-    }
-
-    fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
-        c.try_super_fold_with(self)
-    }
-
-    fn try_fold_predicate(
-        &mut self,
-        p: ty::Predicate<'tcx>,
-    ) -> Result<ty::Predicate<'tcx>, Self::Error> {
-        p.try_super_fold_with(self)
-    }
-}
-
-// This blanket implementation of the fallible trait for infallible folders
-// delegates to infallible methods to ensure coherence.
-impl<'tcx, F> FallibleTypeFolder<'tcx> for F
-where
-    F: TypeFolder<'tcx>,
-{
-    type Error = !;
-
-    fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
-        TypeFolder::tcx(self)
-    }
-
-    fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, !>
-    where
-        T: TypeFoldable<'tcx>,
-    {
-        Ok(self.fold_binder(t))
-    }
-
-    fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, !> {
-        Ok(self.fold_ty(t))
-    }
-
-    fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, !> {
-        Ok(self.fold_region(r))
-    }
-
-    fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, !> {
-        Ok(self.fold_const(c))
-    }
-
-    fn try_fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> Result<ty::Predicate<'tcx>, !> {
-        Ok(self.fold_predicate(p))
-    }
-}
+pub use rustc_type_ir::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
 
 ///////////////////////////////////////////////////////////////////////////
 // Some sample folders
@@ -221,13 +21,13 @@ where
     pub ct_op: H,
 }
 
-impl<'tcx, F, G, H> TypeFolder<'tcx> for BottomUpFolder<'tcx, F, G, H>
+impl<'tcx, F, G, H> TypeFolder<TyCtxt<'tcx>> for BottomUpFolder<'tcx, F, G, H>
 where
     F: FnMut(Ty<'tcx>) -> Ty<'tcx>,
     G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>,
     H: FnMut(ty::Const<'tcx>) -> ty::Const<'tcx>,
 {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
@@ -260,7 +60,7 @@ impl<'tcx> TyCtxt<'tcx> {
         mut f: impl FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>,
     ) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         value.fold_with(&mut RegionFolder::new(self, &mut f))
     }
@@ -271,7 +71,7 @@ impl<'tcx> TyCtxt<'tcx> {
         mut f: impl FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>,
     ) -> T
     where
-        T: TypeSuperFoldable<'tcx>,
+        T: TypeSuperFoldable<TyCtxt<'tcx>>,
     {
         value.super_fold_with(&mut RegionFolder::new(self, &mut f))
     }
@@ -311,12 +111,12 @@ impl<'a, 'tcx> RegionFolder<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> TypeFolder<'tcx> for RegionFolder<'a, 'tcx> {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn fold_binder<T: TypeFoldable<'tcx>>(
+    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
         &mut self,
         t: ty::Binder<'tcx, T>,
     ) -> ty::Binder<'tcx, T> {
@@ -385,15 +185,15 @@ impl<'tcx, D: BoundVarReplacerDelegate<'tcx>> BoundVarReplacer<'tcx, D> {
     }
 }
 
-impl<'tcx, D> TypeFolder<'tcx> for BoundVarReplacer<'tcx, D>
+impl<'tcx, D> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'tcx, D>
 where
     D: BoundVarReplacerDelegate<'tcx>,
 {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn fold_binder<T: TypeFoldable<'tcx>>(
+    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
         &mut self,
         t: ty::Binder<'tcx, T>,
     ) -> ty::Binder<'tcx, T> {
@@ -425,7 +225,7 @@ where
                     // debruijn index. Then we adjust it to the
                     // correct depth.
                     assert_eq!(debruijn1, ty::INNERMOST);
-                    self.tcx.reuse_or_mk_region(region, ty::ReLateBound(debruijn, br))
+                    self.tcx.mk_re_late_bound(debruijn, br)
                 } else {
                     region
                 }
@@ -471,7 +271,7 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
     where
         F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let mut region_map = BTreeMap::new();
         let real_fld_r = |br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br));
@@ -486,7 +286,7 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> T
     where
         F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let value = value.skip_binder();
         if !value.has_escaping_bound_vars() {
@@ -505,7 +305,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Replaces all escaping bound vars. The `fld_r` closure replaces escaping
     /// bound regions; the `fld_t` closure replaces escaping bound types and the `fld_c`
     /// closure replaces escaping bound consts.
-    pub fn replace_escaping_bound_vars_uncached<T: TypeFoldable<'tcx>>(
+    pub fn replace_escaping_bound_vars_uncached<T: TypeFoldable<TyCtxt<'tcx>>>(
         self,
         value: T,
         delegate: impl BoundVarReplacerDelegate<'tcx>,
@@ -521,7 +321,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Replaces all types or regions bound by the given `Binder`. The `fld_r`
     /// closure replaces bound regions, the `fld_t` closure replaces bound
     /// types, and `fld_c` replaces bound constants.
-    pub fn replace_bound_vars_uncached<T: TypeFoldable<'tcx>>(
+    pub fn replace_bound_vars_uncached<T: TypeFoldable<TyCtxt<'tcx>>>(
         self,
         value: Binder<'tcx, T>,
         delegate: impl BoundVarReplacerDelegate<'tcx>,
@@ -537,35 +337,29 @@ impl<'tcx> TyCtxt<'tcx> {
         value: ty::Binder<'tcx, T>,
     ) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         self.replace_late_bound_regions_uncached(value, |br| {
-            self.mk_region(ty::ReFree(ty::FreeRegion {
-                scope: all_outlive_scope,
-                bound_region: br.kind,
-            }))
+            self.mk_re_free(all_outlive_scope, br.kind)
         })
     }
 
     pub fn shift_bound_var_indices<T>(self, bound_vars: usize, value: T) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let shift_bv = |bv: ty::BoundVar| ty::BoundVar::from_usize(bv.as_usize() + bound_vars);
         self.replace_escaping_bound_vars_uncached(
             value,
             FnMutDelegate {
                 regions: &mut |r: ty::BoundRegion| {
-                    self.mk_region(ty::ReLateBound(
+                    self.mk_re_late_bound(
                         ty::INNERMOST,
                         ty::BoundRegion { var: shift_bv(r.var), kind: r.kind },
-                    ))
+                    )
                 },
                 types: &mut |t: ty::BoundTy| {
-                    self.mk_ty(ty::Bound(
-                        ty::INNERMOST,
-                        ty::BoundTy { var: shift_bv(t.var), kind: t.kind },
-                    ))
+                    self.mk_bound(ty::INNERMOST, ty::BoundTy { var: shift_bv(t.var), kind: t.kind })
                 },
                 consts: &mut |c, ty: Ty<'tcx>| {
                     self.mk_const(ty::ConstKind::Bound(ty::INNERMOST, shift_bv(c)), ty)
@@ -578,7 +372,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// method lookup and a few other places where precise region relationships are not required.
     pub fn erase_late_bound_regions<T>(self, value: Binder<'tcx, T>) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         self.replace_late_bound_regions(value, |_| self.lifetimes.re_erased).0
     }
@@ -586,7 +380,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Anonymize all bound variables in `value`, this is mostly used to improve caching.
     pub fn anonymize_bound_vars<T>(self, value: Binder<'tcx, T>) -> Binder<'tcx, T>
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         struct Anonymize<'a, 'tcx> {
             tcx: TyCtxt<'tcx>,
@@ -603,16 +397,18 @@ impl<'tcx> TyCtxt<'tcx> {
                     })
                     .expect_region();
                 let br = ty::BoundRegion { var, kind };
-                self.tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br))
+                self.tcx.mk_re_late_bound(ty::INNERMOST, br)
             }
             fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
                 let entry = self.map.entry(bt.var);
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon))
+                    .or_insert_with(|| {
+                        ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon(index as u32))
+                    })
                     .expect_ty();
-                self.tcx.mk_ty(ty::Bound(ty::INNERMOST, BoundTy { var, kind }))
+                self.tcx.mk_bound(ty::INNERMOST, BoundTy { var, kind })
             }
             fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> {
                 let entry = self.map.entry(bv);
@@ -626,7 +422,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let mut map = Default::default();
         let delegate = Anonymize { tcx: self, map: &mut map };
         let inner = self.replace_escaping_bound_vars_uncached(value.skip_binder(), delegate);
-        let bound_vars = self.mk_bound_variable_kinds(map.into_values());
+        let bound_vars = self.mk_bound_variable_kinds_from_iter(map.into_values());
         Binder::bind_with_vars(inner, bound_vars)
     }
 }
@@ -652,12 +448,12 @@ impl<'tcx> Shifter<'tcx> {
     }
 }
 
-impl<'tcx> TypeFolder<'tcx> for Shifter<'tcx> {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Shifter<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn fold_binder<T: TypeFoldable<'tcx>>(
+    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
         &mut self,
         t: ty::Binder<'tcx, T>,
     ) -> ty::Binder<'tcx, T> {
@@ -671,8 +467,7 @@ impl<'tcx> TypeFolder<'tcx> for Shifter<'tcx> {
         match *r {
             ty::ReLateBound(debruijn, br) if debruijn >= self.current_index => {
                 let debruijn = debruijn.shifted_in(self.amount);
-                let shifted = ty::ReLateBound(debruijn, br);
-                self.tcx.mk_region(shifted)
+                self.tcx.mk_re_late_bound(debruijn, br)
             }
             _ => r,
         }
@@ -682,7 +477,7 @@ impl<'tcx> TypeFolder<'tcx> for Shifter<'tcx> {
         match *ty.kind() {
             ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => {
                 let debruijn = debruijn.shifted_in(self.amount);
-                self.tcx.mk_ty(ty::Bound(debruijn, bound_ty))
+                self.tcx.mk_bound(debruijn, bound_ty)
             }
 
             _ if ty.has_vars_bound_at_or_above(self.current_index) => ty.super_fold_with(self),
@@ -713,7 +508,7 @@ pub fn shift_region<'tcx>(
 ) -> ty::Region<'tcx> {
     match *region {
         ty::ReLateBound(debruijn, br) if amount > 0 => {
-            tcx.mk_region(ty::ReLateBound(debruijn.shifted_in(amount), br))
+            tcx.mk_re_late_bound(debruijn.shifted_in(amount), br)
         }
         _ => region,
     }
@@ -721,7 +516,7 @@ pub fn shift_region<'tcx>(
 
 pub fn shift_vars<'tcx, T>(tcx: TyCtxt<'tcx>, value: T, amount: u32) -> T
 where
-    T: TypeFoldable<'tcx>,
+    T: TypeFoldable<TyCtxt<'tcx>>,
 {
     debug!("shift_vars(value={:?}, amount={})", value, amount);
 
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 801ca6004..baef4ffed 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -85,7 +85,7 @@ impl GenericParamDef {
     ) -> Option<EarlyBinder<ty::GenericArg<'tcx>>> {
         match self.kind {
             GenericParamDefKind::Type { has_default, .. } if has_default => {
-                Some(tcx.bound_type_of(self.def_id).map_bound(|t| t.into()))
+                Some(tcx.type_of(self.def_id).map_bound(|t| t.into()))
             }
             GenericParamDefKind::Const { has_default } if has_default => {
                 Some(tcx.const_param_default(self.def_id).map_bound(|c| c.into()))
@@ -100,10 +100,10 @@ impl GenericParamDef {
         preceding_substs: &[ty::GenericArg<'tcx>],
     ) -> ty::GenericArg<'tcx> {
         match &self.kind {
-            ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
-            ty::GenericParamDefKind::Type { .. } => tcx.ty_error().into(),
+            ty::GenericParamDefKind::Lifetime => tcx.mk_re_error_misc().into(),
+            ty::GenericParamDefKind::Type { .. } => tcx.ty_error_misc().into(),
             ty::GenericParamDefKind::Const { .. } => {
-                tcx.const_error(tcx.bound_type_of(self.def_id).subst(tcx, preceding_substs)).into()
+                tcx.const_error(tcx.type_of(self.def_id).subst(tcx, preceding_substs)).into()
             }
         }
     }
diff --git a/compiler/rustc_middle/src/ty/impls_ty.rs b/compiler/rustc_middle/src/ty/impls_ty.rs
index 3e59c0b96..4c7822acd 100644
--- a/compiler/rustc_middle/src/ty/impls_ty.rs
+++ b/compiler/rustc_middle/src/ty/impls_ty.rs
@@ -79,7 +79,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArgKin
             // WARNING: We dedup cache the `HashStable` results for `List`
             // while ignoring types and freely transmute
             // between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
-            // See `fn intern_type_list` for more details.
+            // See `fn mk_type_list` for more details.
             //
             // We therefore hash types without adding a hash for their discriminant.
             //
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
index 33f727297..e268553f8 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
@@ -57,7 +57,7 @@ impl<'tcx> InhabitedPredicate<'tcx> {
         match self {
             Self::False => Ok(false),
             Self::True => Ok(true),
-            Self::ConstIsZero(const_) => match const_.try_eval_usize(tcx, param_env) {
+            Self::ConstIsZero(const_) => match const_.try_eval_target_usize(tcx, param_env) {
                 None | Some(0) => Ok(true),
                 Some(1..) => Ok(false),
             },
@@ -159,7 +159,7 @@ impl<'tcx> InhabitedPredicate<'tcx> {
         match self {
             Self::ConstIsZero(c) => {
                 let c = ty::EarlyBinder(c).subst(tcx, substs);
-                let pred = match c.kind().try_to_machine_usize(tcx) {
+                let pred = match c.kind().try_to_target_usize(tcx) {
                     Some(0) => Self::True,
                     Some(1..) => Self::False,
                     None => Self::ConstIsZero(c),
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
index 5d5089cec..92a040068 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
@@ -87,7 +87,7 @@ impl<'tcx> VariantDef {
         InhabitedPredicate::all(
             tcx,
             self.fields.iter().map(|field| {
-                let pred = tcx.type_of(field.did).inhabited_predicate(tcx);
+                let pred = tcx.type_of(field.did).subst_identity().inhabited_predicate(tcx);
                 if adt.is_enum() {
                     return pred;
                 }
@@ -105,7 +105,7 @@ impl<'tcx> VariantDef {
 impl<'tcx> Ty<'tcx> {
     pub fn inhabited_predicate(self, tcx: TyCtxt<'tcx>) -> InhabitedPredicate<'tcx> {
         match self.kind() {
-            // For now, union`s are always considered inhabited
+            // For now, unions are always considered inhabited
             Adt(adt, _) if adt.is_union() => InhabitedPredicate::True,
             // Non-exhaustive ADTs from other crates are always considered inhabited
             Adt(adt, _) if adt.is_variant_list_non_exhaustive() && !adt.did().is_local() => {
@@ -191,7 +191,7 @@ fn inhabited_predicate_type<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> InhabitedP
 
         // If we can evaluate the array length before having a `ParamEnv`, then
         // we can simplify the predicate. This is an optimization.
-        Array(ty, len) => match len.kind().try_to_machine_usize(tcx) {
+        Array(ty, len) => match len.kind().try_to_target_usize(tcx) {
             Some(0) => InhabitedPredicate::True,
             Some(1..) => ty.inhabited_predicate(tcx),
             None => ty.inhabited_predicate(tcx).or(tcx, InhabitedPredicate::ConstIsZero(len)),
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 6ac00d16c..f4028a5a9 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -1,7 +1,7 @@
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::print::{FmtPrinter, Printer};
-use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitable};
-use crate::ty::{EarlyBinder, InternalSubsts, SubstsRef};
+use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
+use crate::ty::{EarlyBinder, InternalSubsts, SubstsRef, TypeVisitableExt};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
@@ -103,7 +103,7 @@ impl<'tcx> Instance<'tcx> {
     /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
     pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
         let ty = tcx.type_of(self.def.def_id());
-        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
+        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty.skip_binder())
     }
 
     /// Finds a crate that contains a monomorphization of this instance that
@@ -459,7 +459,7 @@ impl<'tcx> Instance<'tcx> {
         substs: SubstsRef<'tcx>,
     ) -> Option<Instance<'tcx>> {
         debug!("resolve_for_vtable(def_id={:?}, substs={:?})", def_id, substs);
-        let fn_sig = tcx.fn_sig(def_id);
+        let fn_sig = tcx.fn_sig(def_id).subst_identity();
         let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
             && fn_sig.input(0).skip_binder().is_param(0)
             && tcx.generics_of(def_id).has_self;
@@ -540,7 +540,7 @@ impl<'tcx> Instance<'tcx> {
 
     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
         let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
-        let substs = tcx.intern_substs(&[ty.into()]);
+        let substs = tcx.mk_substs(&[ty.into()]);
         Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
     }
 
@@ -584,12 +584,12 @@ impl<'tcx> Instance<'tcx> {
     /// this function returns `None`, then the MIR body does not require substitution during
     /// codegen.
     fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
-        if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
+        self.def.has_polymorphic_mir_body().then_some(self.substs)
     }
 
     pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
     where
-        T: TypeFoldable<'tcx> + Copy,
+        T: TypeFoldable<TyCtxt<'tcx>> + Copy,
     {
         if let Some(substs) = self.substs_for_mir_body() {
             EarlyBinder(*v).subst(tcx, substs)
@@ -606,7 +606,7 @@ impl<'tcx> Instance<'tcx> {
         v: T,
     ) -> T
     where
-        T: TypeFoldable<'tcx> + Clone,
+        T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
@@ -623,7 +623,7 @@ impl<'tcx> Instance<'tcx> {
         v: T,
     ) -> Result<T, NormalizationError<'tcx>>
     where
-        T: TypeFoldable<'tcx> + Clone,
+        T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
@@ -662,7 +662,7 @@ fn polymorphize<'tcx>(
     let def_id = instance.def_id();
     let upvars_ty = if tcx.is_closure(def_id) {
         Some(substs.as_closure().tupled_upvars_ty())
-    } else if tcx.type_of(def_id).is_generator() {
+    } else if tcx.type_of(def_id).skip_binder().is_generator() {
         Some(substs.as_generator().tupled_upvars_ty())
     } else {
         None
@@ -674,8 +674,8 @@ fn polymorphize<'tcx>(
         tcx: TyCtxt<'tcx>,
     }
 
-    impl<'tcx> ty::TypeFolder<'tcx> for PolymorphizationFolder<'tcx> {
-        fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
+    impl<'tcx> ty::TypeFolder<TyCtxt<'tcx>> for PolymorphizationFolder<'tcx> {
+        fn interner(&self) -> TyCtxt<'tcx> {
             self.tcx
         }
 
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index dfd016569..254ffc33c 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1,11 +1,13 @@
+use crate::fluent_generated as fluent;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::normalize_erasing_regions::NormalizationError;
-use crate::ty::{self, ReprOptions, Ty, TyCtxt, TypeVisitable};
+use crate::ty::{self, ReprOptions, Ty, TyCtxt, TypeVisitableExt};
 use rustc_errors::{DiagnosticBuilder, Handler, IntoDiagnostic};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_index::vec::Idx;
 use rustc_session::config::OptLevel;
+use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::*;
@@ -91,7 +93,7 @@ impl IntegerExt for Integer {
             if discr < fit {
                 bug!(
                     "Integer::repr_discr: `#[repr]` hint too small for \
-                      discriminant range of enum `{}",
+                      discriminant range of enum `{}`",
                     ty
                 )
             }
@@ -128,7 +130,8 @@ impl PrimitiveExt for Primitive {
             Int(i, signed) => i.to_ty(tcx, signed),
             F32 => tcx.types.f32,
             F64 => tcx.types.f64,
-            Pointer => tcx.mk_mut_ptr(tcx.mk_unit()),
+            // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
+            Pointer(_) => tcx.mk_mut_ptr(tcx.mk_unit()),
         }
     }
 
@@ -138,7 +141,11 @@ impl PrimitiveExt for Primitive {
     fn to_int_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match *self {
             Int(i, signed) => i.to_ty(tcx, signed),
-            Pointer => tcx.types.usize,
+            // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
+            Pointer(_) => {
+                let signed = false;
+                tcx.data_layout().ptr_sized_integer().to_ty(tcx, signed)
+            }
             F32 | F64 => bug!("floats do not have an int type"),
         }
     }
@@ -163,6 +170,41 @@ pub const FAT_PTR_EXTRA: usize = 1;
 /// * Cranelift stores the base-2 log of the lane count in a 4 bit integer.
 pub const MAX_SIMD_LANES: u64 = 1 << 0xF;
 
+/// Used in `check_validity_requirement` to indicate the kind of initialization
+/// that is checked to be valid
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+pub enum ValidityRequirement {
+    Inhabited,
+    Zero,
+    /// The return value of mem::uninitialized, 0x01
+    /// (unless -Zstrict-init-checks is on, in which case it's the same as Uninit).
+    UninitMitigated0x01Fill,
+    /// True uninitialized memory.
+    Uninit,
+}
+
+impl ValidityRequirement {
+    pub fn from_intrinsic(intrinsic: Symbol) -> Option<Self> {
+        match intrinsic {
+            sym::assert_inhabited => Some(Self::Inhabited),
+            sym::assert_zero_valid => Some(Self::Zero),
+            sym::assert_mem_uninitialized_valid => Some(Self::UninitMitigated0x01Fill),
+            _ => None,
+        }
+    }
+}
+
+impl fmt::Display for ValidityRequirement {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Inhabited => f.write_str("is inhabited"),
+            Self::Zero => f.write_str("allows being left zeroed"),
+            Self::UninitMitigated0x01Fill => f.write_str("allows being filled with 0x01"),
+            Self::Uninit => f.write_str("allows being left uninitialized"),
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
 pub enum LayoutError<'tcx> {
     Unknown(Ty<'tcx>),
@@ -177,16 +219,16 @@ impl IntoDiagnostic<'_, !> for LayoutError<'_> {
         match self {
             LayoutError::Unknown(ty) => {
                 diag.set_arg("ty", ty);
-                diag.set_primary_message(rustc_errors::fluent::middle_unknown_layout);
+                diag.set_primary_message(fluent::middle_unknown_layout);
             }
             LayoutError::SizeOverflow(ty) => {
                 diag.set_arg("ty", ty);
-                diag.set_primary_message(rustc_errors::fluent::middle_values_too_big);
+                diag.set_primary_message(fluent::middle_values_too_big);
             }
             LayoutError::NormalizationFailure(ty, e) => {
                 diag.set_arg("ty", ty);
                 diag.set_arg("failure_ty", e.get_type_for_failure());
-                diag.set_primary_message(rustc_errors::fluent::middle_cannot_be_normalized);
+                diag.set_primary_message(fluent::middle_cannot_be_normalized);
             }
         }
         diag
@@ -590,7 +632,7 @@ where
                     ty::Adt(def, _) => def.variant(variant_index).fields.len(),
                     _ => bug!(),
                 };
-                tcx.intern_layout(LayoutS {
+                tcx.mk_layout(LayoutS {
                     variants: Variants::Single { index: variant_index },
                     fields: match NonZeroUsize::new(fields) {
                         Some(fields) => FieldsShape::Union(fields),
@@ -603,7 +645,7 @@ where
                 })
             }
 
-            Variants::Multiple { ref variants, .. } => cx.tcx().intern_layout(variants[variant_index].clone()),
+            Variants::Multiple { ref variants, .. } => cx.tcx().mk_layout(variants[variant_index].clone()),
         };
 
         assert_eq!(*layout.variants(), Variants::Single { index: variant_index });
@@ -625,7 +667,7 @@ where
             let tcx = cx.tcx();
             let tag_layout = |tag: Scalar| -> TyAndLayout<'tcx> {
                 TyAndLayout {
-                    layout: tcx.intern_layout(LayoutS::scalar(cx, tag)),
+                    layout: tcx.mk_layout(LayoutS::scalar(cx, tag)),
                     ty: tag.primitive().to_ty(tcx),
                 }
             };
@@ -640,6 +682,7 @@ where
                 | ty::Never
                 | ty::FnDef(..)
                 | ty::GeneratorWitness(..)
+                | ty::GeneratorWitnessMIR(..)
                 | ty::Foreign(..)
                 | ty::Dynamic(_, _, ty::Dyn) => {
                     bug!("TyAndLayout::field({:?}): not applicable", this)
@@ -764,7 +807,7 @@ where
 
                 ty::Dynamic(_, _, ty::DynStar) => {
                     if i == 0 {
-                        TyMaybeWithLayout::Ty(tcx.types.usize)
+                        TyMaybeWithLayout::Ty(tcx.mk_mut_ptr(tcx.types.unit))
                     } else if i == 1 {
                         // FIXME(dyn-star) same FIXME as above applies here too
                         TyMaybeWithLayout::Ty(
@@ -812,17 +855,12 @@ where
         let tcx = cx.tcx();
         let param_env = cx.param_env();
 
-        let addr_space_of_ty = |ty: Ty<'tcx>| {
-            if ty.is_fn() { cx.data_layout().instruction_address_space } else { AddressSpace::DATA }
-        };
-
         let pointee_info = match *this.ty.kind() {
             ty::RawPtr(mt) if offset.bytes() == 0 => {
                 tcx.layout_of(param_env.and(mt.ty)).ok().map(|layout| PointeeInfo {
                     size: layout.size,
                     align: layout.align.abi,
                     safe: None,
-                    address_space: addr_space_of_ty(mt.ty),
                 })
             }
             ty::FnPtr(fn_sig) if offset.bytes() == 0 => {
@@ -830,44 +868,26 @@ where
                     size: layout.size,
                     align: layout.align.abi,
                     safe: None,
-                    address_space: cx.data_layout().instruction_address_space,
                 })
             }
             ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
-                let address_space = addr_space_of_ty(ty);
-                let kind = if tcx.sess.opts.optimize == OptLevel::No {
-                    // Use conservative pointer kind if not optimizing. This saves us the
-                    // Freeze/Unpin queries, and can save time in the codegen backend (noalias
-                    // attributes in LLVM have compile-time cost even in unoptimized builds).
-                    PointerKind::SharedMutable
-                } else {
-                    match mt {
-                        hir::Mutability::Not => {
-                            if ty.is_freeze(tcx, cx.param_env()) {
-                                PointerKind::Frozen
-                            } else {
-                                PointerKind::SharedMutable
-                            }
-                        }
-                        hir::Mutability::Mut => {
-                            // References to self-referential structures should not be considered
-                            // noalias, as another pointer to the structure can be obtained, that
-                            // is not based-on the original reference. We consider all !Unpin
-                            // types to be potentially self-referential here.
-                            if ty.is_unpin(tcx, cx.param_env()) {
-                                PointerKind::UniqueBorrowed
-                            } else {
-                                PointerKind::UniqueBorrowedPinned
-                            }
-                        }
-                    }
+                // Use conservative pointer kind if not optimizing. This saves us the
+                // Freeze/Unpin queries, and can save time in the codegen backend (noalias
+                // attributes in LLVM have compile-time cost even in unoptimized builds).
+                let optimize = tcx.sess.opts.optimize != OptLevel::No;
+                let kind = match mt {
+                    hir::Mutability::Not => PointerKind::SharedRef {
+                        frozen: optimize && ty.is_freeze(tcx, cx.param_env()),
+                    },
+                    hir::Mutability::Mut => PointerKind::MutableRef {
+                        unpin: optimize && ty.is_unpin(tcx, cx.param_env()),
+                    },
                 };
 
                 tcx.layout_of(param_env.and(ty)).ok().map(|layout| PointeeInfo {
                     size: layout.size,
                     align: layout.align.abi,
                     safe: Some(kind),
-                    address_space,
                 })
             }
 
@@ -904,7 +924,9 @@ where
                 let mut result = None;
 
                 if let Some(variant) = data_variant {
-                    let ptr_end = offset + Pointer.size(cx);
+                    // FIXME(erikdesjardins): handle non-default addrspace ptr sizes
+                    // (requires passing in the expected address space from the caller)
+                    let ptr_end = offset + Pointer(AddressSpace::DATA).size(cx);
                     for i in 0..variant.fields.count() {
                         let field_start = variant.fields.offset(i);
                         if field_start <= offset {
@@ -930,7 +952,10 @@ where
                 if let Some(ref mut pointee) = result {
                     if let ty::Adt(def, _) = this.ty.kind() {
                         if def.is_box() && offset.bytes() == 0 {
-                            pointee.safe = Some(PointerKind::UniqueOwned);
+                            let optimize = tcx.sess.opts.optimize != OptLevel::No;
+                            pointee.safe = Some(PointerKind::Box {
+                                unpin: optimize && this.ty.boxed_ty().is_unpin(tcx, cx.param_env()),
+                            });
                         }
                     }
                 }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 7dfcd1bb5..dce18a585 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -12,7 +12,7 @@
 #![allow(rustc::usage_of_ty_tykind)]
 
 pub use self::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
-pub use self::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
+pub use self::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 pub use self::AssocItemContainer::*;
 pub use self::BorrowKind::*;
 pub use self::IntVarValue::*;
@@ -31,23 +31,22 @@ pub use generics::*;
 use rustc_ast as ast;
 use rustc_ast::node_id::NodeMap;
 use rustc_attr as attr;
-use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
-use rustc_hir::def::{CtorKind, CtorOf, DefKind, LifetimeRes, Res};
+use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
 use rustc_hir::Node;
 use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_serialize::{Decodable, Encodable};
-use rustc_session::cstore::Untracked;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
-use rustc_span::{ExpnId, Span};
+use rustc_span::{ExpnId, ExpnKind, Span};
 use rustc_target::abi::{Align, Integer, IntegerType, VariantIdx};
 pub use rustc_target::abi::{ReprFlags, ReprOptions};
 use rustc_type_ir::WithCachedTypeInfo;
@@ -74,7 +73,7 @@ pub use self::binding::BindingMode;
 pub use self::binding::BindingMode::*;
 pub use self::closure::{
     is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
-    CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
+    CapturedPlace, ClosureKind, ClosureTypeInfo, MinCaptureInformationMap, MinCaptureList,
     RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
     CAPTURE_STRUCT_LOCAL,
 };
@@ -154,7 +153,6 @@ pub type RegisteredTools = FxHashSet<Ident>;
 pub struct ResolverOutputs {
     pub global_ctxt: ResolverGlobalCtxt,
     pub ast_lowering: ResolverAstLowering,
-    pub untracked: Untracked,
 }
 
 #[derive(Debug)]
@@ -167,12 +165,8 @@ pub struct ResolverGlobalCtxt {
     pub effective_visibilities: EffectiveVisibilities,
     pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
-    pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
     pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
-    /// Extern prelude entries. The value is `true` if the entry was introduced
-    /// via `extern crate` item and not `--extern` option or compiler built-in.
-    pub extern_prelude: FxHashMap<Symbol, bool>,
     pub main_def: Option<MainDefinition>,
     pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
     /// A list of proc macro LocalDefIds, written out in the order in which
@@ -182,6 +176,9 @@ pub struct ResolverGlobalCtxt {
     /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
     pub confused_type_with_std_module: FxHashMap<Span, Span>,
     pub registered_tools: RegisteredTools,
+    pub doc_link_resolutions: FxHashMap<LocalDefId, DocLinkResMap>,
+    pub doc_link_traits_in_scope: FxHashMap<LocalDefId, Vec<DefId>>,
+    pub all_macro_rules: FxHashMap<Symbol, Res<ast::NodeId>>,
 }
 
 /// Resolutions that should only be used for lowering.
@@ -453,18 +450,6 @@ pub struct CReaderCacheKey {
 #[rustc_pass_by_value]
 pub struct Ty<'tcx>(Interned<'tcx, WithCachedTypeInfo<TyKind<'tcx>>>);
 
-impl<'tcx> TyCtxt<'tcx> {
-    /// A "bool" type used in rustc_mir_transform unit tests when we
-    /// have not spun up a TyCtxt.
-    pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> =
-        Ty(Interned::new_unchecked(&WithCachedTypeInfo {
-            internee: ty::Bool,
-            stable_hash: Fingerprint::ZERO,
-            flags: TypeFlags::empty(),
-            outer_exclusive_binder: DebruijnIndex::from_usize(0),
-        }));
-}
-
 impl ty::EarlyBoundRegion {
     /// Does this early bound region have a name? Early bound regions normally
     /// always have names except when using anonymous lifetimes (`'_`).
@@ -558,6 +543,8 @@ impl<'tcx> Predicate<'tcx> {
             | PredicateKind::Clause(Clause::RegionOutlives(_))
             | PredicateKind::Clause(Clause::TypeOutlives(_))
             | PredicateKind::Clause(Clause::Projection(_))
+            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            | PredicateKind::AliasEq(..)
             | PredicateKind::ObjectSafe(_)
             | PredicateKind::ClosureKind(_, _, _)
             | PredicateKind::Subtype(_)
@@ -595,6 +582,10 @@ pub enum Clause<'tcx> {
     /// `where <T as TraitRef>::Name == X`, approximately.
     /// See the `ProjectionPredicate` struct for details.
     Projection(ProjectionPredicate<'tcx>),
+
+    /// Ensures that a const generic argument to a parameter `const N: u8`
+    /// is of type `u8`.
+    ConstArgHasType(Const<'tcx>, Ty<'tcx>),
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
@@ -645,6 +636,12 @@ pub enum PredicateKind<'tcx> {
     /// A marker predicate that is always ambiguous.
     /// Used for coherence to mark opaque types as possibly equal to each other but ambiguous.
     Ambiguous,
+
+    /// Separate from `Clause::Projection` which is used for normalization in new solver.
+    /// This predicate requires two terms to be equal to eachother.
+    ///
+    /// Only used for new solver
+    AliasEq(Term<'tcx>, Term<'tcx>),
 }
 
 /// The crate outlives map is computed during typeck and contains the
@@ -713,7 +710,7 @@ impl<'tcx> Predicate<'tcx> {
         //   The substitution from the input trait-ref is therefore going to be
         //   `'a => 'x` (where `'x` has a DB index of 1).
         // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
-        //   early-bound parameter and `'b' is a late-bound parameter with a
+        //   early-bound parameter and `'b` is a late-bound parameter with a
         //   DB index of 1.
         // - If we replace `'a` with `'x` from the input, it too will have
         //   a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
@@ -756,7 +753,7 @@ impl<'tcx> Predicate<'tcx> {
         let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
         // 3) ['x] + ['b] -> ['x, 'b]
         let bound_vars =
-            tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
+            tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(pred_bound_vars));
         tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
     }
 }
@@ -917,14 +914,17 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Term<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for Term<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Term<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(self.unpack().try_fold_with(folder)?.pack())
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for Term<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Term<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         self.unpack().visit_with(visitor)
     }
 }
@@ -976,6 +976,33 @@ impl<'tcx> Term<'tcx> {
             TermKind::Const(c) => c.into(),
         }
     }
+
+    /// This function returns `None` for `AliasKind::Opaque`.
+    ///
+    /// FIXME: rename `AliasTy` to `AliasTerm` and make sure we correctly
+    /// deal with constants.
+    pub fn to_alias_term_no_opaque(&self, tcx: TyCtxt<'tcx>) -> Option<AliasTy<'tcx>> {
+        match self.unpack() {
+            TermKind::Ty(ty) => match ty.kind() {
+                ty::Alias(kind, alias_ty) => match kind {
+                    AliasKind::Projection => Some(*alias_ty),
+                    AliasKind::Opaque => None,
+                },
+                _ => None,
+            },
+            TermKind::Const(ct) => match ct.kind() {
+                ConstKind::Unevaluated(uv) => Some(tcx.mk_alias_ty(uv.def.did, uv.substs)),
+                _ => None,
+            },
+        }
+    }
+
+    pub fn is_infer(&self) -> bool {
+        match self.unpack() {
+            TermKind::Ty(ty) => ty.is_ty_or_numeric_infer(),
+            TermKind::Const(ct) => ct.is_ct_infer(),
+        }
+    }
 }
 
 const TAG_MASK: usize = 0b11;
@@ -1165,6 +1192,8 @@ impl<'tcx> Predicate<'tcx> {
         match predicate.skip_binder() {
             PredicateKind::Clause(Clause::Trait(t)) => Some(predicate.rebind(t)),
             PredicateKind::Clause(Clause::Projection(..))
+            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            | PredicateKind::AliasEq(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1184,6 +1213,8 @@ impl<'tcx> Predicate<'tcx> {
         match predicate.skip_binder() {
             PredicateKind::Clause(Clause::Projection(t)) => Some(predicate.rebind(t)),
             PredicateKind::Clause(Clause::Trait(..))
+            | PredicateKind::Clause(Clause::ConstArgHasType(..))
+            | PredicateKind::AliasEq(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1203,7 +1234,9 @@ impl<'tcx> Predicate<'tcx> {
         match predicate.skip_binder() {
             PredicateKind::Clause(Clause::TypeOutlives(data)) => Some(predicate.rebind(data)),
             PredicateKind::Clause(Clause::Trait(..))
+            | PredicateKind::Clause(Clause::ConstArgHasType(..))
             | PredicateKind::Clause(Clause::Projection(..))
+            | PredicateKind::AliasEq(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1322,7 +1355,7 @@ pub struct OpaqueHiddenType<'tcx> {
 }
 
 impl<'tcx> OpaqueHiddenType<'tcx> {
-    pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
+    pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) -> ErrorGuaranteed {
         // Found different concrete types for the opaque type.
         let sub_diag = if self.span == other.span {
             TypeMismatchReason::ConflictType { span: self.span }
@@ -1334,7 +1367,7 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
             other_ty: other.ty,
             other_span: other.span,
             sub: sub_diag,
-        });
+        })
     }
 
     #[instrument(level = "debug", skip(tcx), ret)]
@@ -1382,7 +1415,7 @@ pub struct Placeholder<T> {
 
 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
 
-pub type PlaceholderType = Placeholder<BoundVar>;
+pub type PlaceholderType = Placeholder<BoundTyKind>;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
@@ -1589,8 +1622,8 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
-    fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ParamEnv<'tcx> {
+    fn try_fold_with<F: ty::fold::FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -1602,8 +1635,8 @@ impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ParamEnv<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         self.caller_bounds().visit_with(visitor)?;
         self.reveal().visit_with(visitor)
     }
@@ -1728,7 +1761,7 @@ impl<'tcx> ParamEnv<'tcx> {
     /// `where Box<u32>: Copy`, which are clearly never
     /// satisfiable. We generally want to behave as if they were true,
     /// although the surrounding function is never reachable.
-    pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
+    pub fn and<T: TypeVisitable<TyCtxt<'tcx>>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
         match self.reveal() {
             Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
 
@@ -1986,7 +2019,7 @@ impl<'tcx> FieldDef {
     /// Returns the type of this field. The resulting type is not normalized. The `subst` is
     /// typically obtained via the second field of [`TyKind::Adt`].
     pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
-        tcx.bound_type_of(self.did).subst(tcx, subst)
+        tcx.type_of(self.did).subst(tcx, subst)
     }
 
     /// Computes the `Ident` of this variant by looking up the `Span`
@@ -2038,6 +2071,12 @@ pub enum ImplOverlapKind {
     Issue33140,
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+pub enum ImplTraitInTraitData {
+    Trait { fn_def_id: DefId, opaque_def_id: DefId },
+    Impl { fn_def_id: DefId },
+}
+
 impl<'tcx> TyCtxt<'tcx> {
     pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
         self.typeck(self.hir().body_owner_def_id(body))
@@ -2167,7 +2206,7 @@ impl<'tcx> TyCtxt<'tcx> {
         Some(Ident::new(def, span))
     }
 
-    pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
+    pub fn opt_associated_item(self, def_id: DefId) -> Option<AssocItem> {
         if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
             Some(self.associated_item(def_id))
         } else {
@@ -2357,15 +2396,17 @@ impl<'tcx> TyCtxt<'tcx> {
         self.trait_def(trait_def_id).has_auto_impl
     }
 
+    /// Returns `true` if this is coinductive, either because it is
+    /// an auto trait or because it has the `#[rustc_coinductive]` attribute.
+    pub fn trait_is_coinductive(self, trait_def_id: DefId) -> bool {
+        self.trait_def(trait_def_id).is_coinductive
+    }
+
     /// Returns `true` if this is a trait alias.
     pub fn trait_is_alias(self, trait_def_id: DefId) -> bool {
         self.def_kind(trait_def_id) == DefKind::TraitAlias
     }
 
-    pub fn trait_is_coinductive(self, trait_def_id: DefId) -> bool {
-        self.trait_is_auto(trait_def_id) || self.lang_items().sized_trait() == Some(trait_def_id)
-    }
-
     /// Returns layout of a generator. Layout might be unavailable if the
     /// generator is tainted by errors.
     pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
@@ -2396,15 +2437,30 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
         if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
             let parent = self.parent(def_id);
-            if let DefKind::Impl = self.def_kind(parent) {
+            if let DefKind::Impl { .. } = self.def_kind(parent) {
                 return Some(parent);
             }
         }
         None
     }
 
-    /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
-    pub fn is_builtin_derive(self, def_id: DefId) -> bool {
+    /// Check if the given `DefId` is `#\[automatically_derived\]`, *and*
+    /// whether it was produced by expanding a builtin derive macro.
+    pub fn is_builtin_derived(self, def_id: DefId) -> bool {
+        if self.is_automatically_derived(def_id)
+            && let Some(def_id) = def_id.as_local()
+            && let outer = self.def_span(def_id).ctxt().outer_expn_data()
+            && matches!(outer.kind, ExpnKind::Macro(MacroKind::Derive, _))
+            && self.has_attr(outer.macro_def_id.unwrap(), sym::rustc_builtin_macro)
+        {
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Check if the given `DefId` is `#\[automatically_derived\]`.
+    pub fn is_automatically_derived(self, def_id: DefId) -> bool {
         self.has_attr(def_id, sym::automatically_derived)
     }
 
@@ -2437,6 +2493,7 @@ impl<'tcx> TyCtxt<'tcx> {
         ident
     }
 
+    // FIXME(vincenzoapalzzo): move the HirId to a LocalDefId
     pub fn adjust_ident_and_get_scope(
         self,
         mut ident: Ident,
@@ -2470,10 +2527,6 @@ impl<'tcx> TyCtxt<'tcx> {
             }
     }
 
-    pub fn is_object_safe(self, key: DefId) -> bool {
-        self.object_safety_violations(key).is_empty()
-    }
-
     #[inline]
     pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
         matches!(
@@ -2494,6 +2547,34 @@ impl<'tcx> TyCtxt<'tcx> {
         }
         def_id
     }
+
+    pub fn impl_method_has_trait_impl_trait_tys(self, def_id: DefId) -> bool {
+        if self.def_kind(def_id) != DefKind::AssocFn {
+            return false;
+        }
+
+        let Some(item) = self.opt_associated_item(def_id) else { return false; };
+        if item.container != ty::AssocItemContainer::ImplContainer {
+            return false;
+        }
+
+        let Some(trait_item_def_id) = item.trait_item_def_id else { return false; };
+
+        // FIXME(RPITIT): This does a somewhat manual walk through the signature
+        // of the trait fn to look for any RPITITs, but that's kinda doing a lot
+        // of work. We can probably remove this when we refactor RPITITs to be
+        // associated types.
+        self.fn_sig(trait_item_def_id).subst_identity().skip_binder().output().walk().any(|arg| {
+            if let ty::GenericArgKind::Type(ty) = arg.unpack()
+                && let ty::Alias(ty::Projection, data) = ty.kind()
+                && self.def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
+            {
+                true
+            } else {
+                false
+            }
+        })
+    }
 }
 
 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
@@ -2619,7 +2700,7 @@ impl<'tcx> fmt::Debug for SymbolName<'tcx> {
 }
 
 #[derive(Debug, Default, Copy, Clone)]
-pub struct FoundRelationships {
+pub struct InferVarInfo {
     /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
     /// obligation, where:
     ///
diff --git a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
index ee13920d5..7c59879a1 100644
--- a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
+++ b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
@@ -7,16 +7,14 @@
 //! `normalize_generic_arg_after_erasing_regions` query for each type
 //! or constant found within. (This underlying query is what is cached.)
 
-use crate::mir;
 use crate::traits::query::NoSolution;
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
-use crate::ty::{self, EarlyBinder, SubstsRef, Ty, TyCtxt};
+use crate::ty::{self, EarlyBinder, SubstsRef, Ty, TyCtxt, TypeVisitableExt};
 
 #[derive(Debug, Copy, Clone, HashStable, TyEncodable, TyDecodable)]
 pub enum NormalizationError<'tcx> {
     Type(Ty<'tcx>),
     Const(ty::Const<'tcx>),
-    ConstantKind(mir::ConstantKind<'tcx>),
 }
 
 impl<'tcx> NormalizationError<'tcx> {
@@ -24,7 +22,6 @@ impl<'tcx> NormalizationError<'tcx> {
         match self {
             NormalizationError::Type(t) => format!("{}", t),
             NormalizationError::Const(c) => format!("{}", c),
-            NormalizationError::ConstantKind(ck) => format!("{}", ck),
         }
     }
 }
@@ -38,7 +35,7 @@ impl<'tcx> TyCtxt<'tcx> {
     #[tracing::instrument(level = "debug", skip(self, param_env))]
     pub fn normalize_erasing_regions<T>(self, param_env: ty::ParamEnv<'tcx>, value: T) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         debug!(
             "normalize_erasing_regions::<{}>(value={:?}, param_env={:?})",
@@ -70,7 +67,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: T,
     ) -> Result<T, NormalizationError<'tcx>>
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         debug!(
             "try_normalize_erasing_regions::<{}>(value={:?}, param_env={:?})",
@@ -107,7 +104,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: ty::Binder<'tcx, T>,
     ) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let value = self.erase_late_bound_regions(value);
         self.normalize_erasing_regions(param_env, value)
@@ -127,7 +124,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: ty::Binder<'tcx, T>,
     ) -> Result<T, NormalizationError<'tcx>>
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         let value = self.erase_late_bound_regions(value);
         self.try_normalize_erasing_regions(param_env, value)
@@ -145,7 +142,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: T,
     ) -> T
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         debug!(
             "subst_and_normalize_erasing_regions(\
@@ -169,7 +166,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: T,
     ) -> Result<T, NormalizationError<'tcx>>
     where
-        T: TypeFoldable<'tcx>,
+        T: TypeFoldable<TyCtxt<'tcx>>,
     {
         debug!(
             "subst_and_normalize_erasing_regions(\
@@ -196,14 +193,14 @@ impl<'tcx> NormalizeAfterErasingRegionsFolder<'tcx> {
         let arg = self.param_env.and(arg);
 
         self.tcx.try_normalize_generic_arg_after_erasing_regions(arg).unwrap_or_else(|_| bug!(
-                "Failed to normalize {:?}, maybe try to call `try_normalize_erasing_regions` instead",
-                arg.value
-            ))
+            "Failed to normalize {:?}, maybe try to call `try_normalize_erasing_regions` instead",
+            arg.value
+        ))
     }
 }
 
-impl<'tcx> TypeFolder<'tcx> for NormalizeAfterErasingRegionsFolder<'tcx> {
-    fn tcx(&self) -> TyCtxt<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for NormalizeAfterErasingRegionsFolder<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
@@ -238,10 +235,10 @@ impl<'tcx> TryNormalizeAfterErasingRegionsFolder<'tcx> {
     }
 }
 
-impl<'tcx> FallibleTypeFolder<'tcx> for TryNormalizeAfterErasingRegionsFolder<'tcx> {
+impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for TryNormalizeAfterErasingRegionsFolder<'tcx> {
     type Error = NormalizationError<'tcx>;
 
-    fn tcx(&self) -> TyCtxt<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
diff --git a/compiler/rustc_middle/src/ty/opaque_types.rs b/compiler/rustc_middle/src/ty/opaque_types.rs
index 98cd92007..751f3066c 100644
--- a/compiler/rustc_middle/src/ty/opaque_types.rs
+++ b/compiler/rustc_middle/src/ty/opaque_types.rs
@@ -3,6 +3,7 @@ use crate::ty::fold::{TypeFolder, TypeSuperFoldable};
 use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc_data_structures::fx::FxHashMap;
+use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
 /// Converts generic params of a TypeFoldable from one
@@ -47,10 +48,51 @@ impl<'tcx> ReverseMapper<'tcx> {
         assert!(!self.do_not_error);
         kind.fold_with(self)
     }
+
+    fn fold_closure_substs(
+        &mut self,
+        def_id: DefId,
+        substs: ty::SubstsRef<'tcx>,
+    ) -> ty::SubstsRef<'tcx> {
+        // I am a horrible monster and I pray for death. When
+        // we encounter a closure here, it is always a closure
+        // from within the function that we are currently
+        // type-checking -- one that is now being encapsulated
+        // in an opaque type. Ideally, we would
+        // go through the types/lifetimes that it references
+        // and treat them just like we would any other type,
+        // which means we would error out if we find any
+        // reference to a type/region that is not in the
+        // "reverse map".
+        //
+        // **However,** in the case of closures, there is a
+        // somewhat subtle (read: hacky) consideration. The
+        // problem is that our closure types currently include
+        // all the lifetime parameters declared on the
+        // enclosing function, even if they are unused by the
+        // closure itself. We can't readily filter them out,
+        // so here we replace those values with `'empty`. This
+        // can't really make a difference to the rest of the
+        // compiler; those regions are ignored for the
+        // outlives relation, and hence don't affect trait
+        // selection or auto traits, and they are erased
+        // during codegen.
+
+        let generics = self.tcx.generics_of(def_id);
+        self.tcx.mk_substs_from_iter(substs.iter().enumerate().map(|(index, kind)| {
+            if index < generics.parent_count {
+                // Accommodate missing regions in the parent kinds...
+                self.fold_kind_no_missing_regions_error(kind)
+            } else {
+                // ...but not elsewhere.
+                self.fold_kind_normally(kind)
+            }
+        }))
+    }
 }
 
-impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
-    fn tcx(&self) -> TyCtxt<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
@@ -67,6 +109,8 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
             // them.
             ty::ReErased => return r,
 
+            ty::ReError(_) => return r,
+
             // The regions that we expect from borrow checking.
             ty::ReEarlyBound(_) | ty::ReFree(_) => {}
 
@@ -83,20 +127,21 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
             Some(u) => panic!("region mapped to unexpected kind: {:?}", u),
             None if self.do_not_error => self.tcx.lifetimes.re_static,
             None => {
-                self.tcx
+                let e = self
+                    .tcx
                     .sess
                     .struct_span_err(self.span, "non-defining opaque type use in defining scope")
                     .span_label(
                         self.span,
                         format!(
                             "lifetime `{}` is part of concrete type but not used in \
-                                 parameter list of the `impl Trait` type alias",
+                             parameter list of the `impl Trait` type alias",
                             r
                         ),
                     )
                     .emit();
 
-                self.tcx().lifetimes.re_static
+                self.interner().mk_re_error(e)
             }
         }
     }
@@ -104,59 +149,20 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
         match *ty.kind() {
             ty::Closure(def_id, substs) => {
-                // I am a horrible monster and I pray for death. When
-                // we encounter a closure here, it is always a closure
-                // from within the function that we are currently
-                // type-checking -- one that is now being encapsulated
-                // in an opaque type. Ideally, we would
-                // go through the types/lifetimes that it references
-                // and treat them just like we would any other type,
-                // which means we would error out if we find any
-                // reference to a type/region that is not in the
-                // "reverse map".
-                //
-                // **However,** in the case of closures, there is a
-                // somewhat subtle (read: hacky) consideration. The
-                // problem is that our closure types currently include
-                // all the lifetime parameters declared on the
-                // enclosing function, even if they are unused by the
-                // closure itself. We can't readily filter them out,
-                // so here we replace those values with `'empty`. This
-                // can't really make a difference to the rest of the
-                // compiler; those regions are ignored for the
-                // outlives relation, and hence don't affect trait
-                // selection or auto traits, and they are erased
-                // during codegen.
-
-                let generics = self.tcx.generics_of(def_id);
-                let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
-                    if index < generics.parent_count {
-                        // Accommodate missing regions in the parent kinds...
-                        self.fold_kind_no_missing_regions_error(kind)
-                    } else {
-                        // ...but not elsewhere.
-                        self.fold_kind_normally(kind)
-                    }
-                }));
-
+                let substs = self.fold_closure_substs(def_id, substs);
                 self.tcx.mk_closure(def_id, substs)
             }
 
             ty::Generator(def_id, substs, movability) => {
-                let generics = self.tcx.generics_of(def_id);
-                let substs = self.tcx.mk_substs(substs.iter().enumerate().map(|(index, kind)| {
-                    if index < generics.parent_count {
-                        // Accommodate missing regions in the parent kinds...
-                        self.fold_kind_no_missing_regions_error(kind)
-                    } else {
-                        // ...but not elsewhere.
-                        self.fold_kind_normally(kind)
-                    }
-                }));
-
+                let substs = self.fold_closure_substs(def_id, substs);
                 self.tcx.mk_generator(def_id, substs, movability)
             }
 
+            ty::GeneratorWitnessMIR(def_id, substs) => {
+                let substs = self.fold_closure_substs(def_id, substs);
+                self.tcx.mk_generator_witness_mir(def_id, substs)
+            }
+
             ty::Param(param) => {
                 // Look it up in the substitution list.
                 match self.map.get(&ty.into()).map(|k| k.unpack()) {
@@ -180,7 +186,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
                                 .emit();
                         }
 
-                        self.tcx().ty_error()
+                        self.interner().ty_error_misc()
                     }
                 }
             }
@@ -208,7 +214,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
                             });
                         }
 
-                        self.tcx().const_error(ct.ty())
+                        self.interner().const_error(ct.ty())
                     }
                 }
             }
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 24f3d1acf..8849e7eab 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -57,7 +57,7 @@ trivially_parameterized_over_tcx! {
     crate::metadata::ModChild,
     crate::middle::codegen_fn_attrs::CodegenFnAttrs,
     crate::middle::exported_symbols::SymbolExportInfo,
-    crate::middle::resolve_lifetime::ObjectLifetimeDefault,
+    crate::middle::resolve_bound_vars::ObjectLifetimeDefault,
     crate::mir::ConstQualifs,
     ty::AssocItemContainer,
     ty::DeducedParamAttrs,
@@ -81,6 +81,8 @@ trivially_parameterized_over_tcx! {
     rustc_hir::IsAsync,
     rustc_hir::LangItem,
     rustc_hir::def::DefKind,
+    rustc_hir::def::DocLinkResMap,
+    rustc_hir::def_id::DefId,
     rustc_hir::def_id::DefIndex,
     rustc_hir::definitions::DefKey,
     rustc_index::bit_set::BitSet<u32>,
@@ -117,6 +119,7 @@ macro_rules! parameterized_over_tcx {
 parameterized_over_tcx! {
     crate::middle::exported_symbols::ExportedSymbol,
     crate::mir::Body,
+    crate::mir::GeneratorLayout,
     ty::Ty,
     ty::FnSig,
     ty::GenericPredicates,
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index c302c4611..021c20b58 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -115,7 +115,7 @@ pub trait Printer<'tcx>: Sized {
 
             DefPathData::Impl => {
                 let generics = self.tcx().generics_of(def_id);
-                let self_ty = self.tcx().bound_type_of(def_id);
+                let self_ty = self.tcx().type_of(def_id);
                 let impl_trait_ref = self.tcx().impl_trait_ref(def_id);
                 let (self_ty, impl_trait_ref) = if substs.len() >= generics.count() {
                     (
@@ -265,6 +265,7 @@ fn characteristic_def_id_of_type_cached<'a>(
         ty::FnDef(def_id, _)
         | ty::Closure(def_id, _)
         | ty::Generator(def_id, _, _)
+        | ty::GeneratorWitnessMIR(def_id, _)
         | ty::Foreign(def_id) => Some(def_id),
 
         ty::Bool
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index ae7c20fff..6a053c368 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1,7 +1,7 @@
 use crate::mir::interpret::{AllocRange, GlobalAlloc, Pointer, Provenance, Scalar};
 use crate::ty::{
     self, ConstInt, DefIdTree, ParamConst, ScalarInt, Term, TermKind, Ty, TyCtxt, TypeFoldable,
-    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable,
+    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
 use crate::ty::{GenericArg, GenericArgKind};
 use rustc_apfloat::ieee::{Double, Single};
@@ -22,7 +22,6 @@ use rustc_target::spec::abi::Abi;
 use smallvec::SmallVec;
 
 use std::cell::Cell;
-use std::char;
 use std::collections::BTreeMap;
 use std::fmt::{self, Write as _};
 use std::iter;
@@ -183,7 +182,7 @@ impl<'tcx> RegionHighlightMode<'tcx> {
 
     /// Convenience wrapper for `highlighting_region`.
     pub fn highlighting_region_vid(&mut self, vid: ty::RegionVid, number: usize) {
-        self.highlighting_region(self.tcx.mk_region(ty::ReVar(vid)), number)
+        self.highlighting_region(self.tcx.mk_re_var(vid), number)
     }
 
     /// Returns `Some(n)` with the number to use for the given region, if any.
@@ -226,7 +225,7 @@ pub trait PrettyPrinter<'tcx>:
 
     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         value.as_ref().skip_binder().print(self)
     }
@@ -237,7 +236,7 @@ pub trait PrettyPrinter<'tcx>:
         f: F,
     ) -> Result<Self, Self::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         f(value.as_ref().skip_binder(), self)
     }
@@ -675,8 +674,12 @@ pub trait PrettyPrinter<'tcx>:
                 p!(")")
             }
             ty::FnDef(def_id, substs) => {
-                let sig = self.tcx().bound_fn_sig(def_id).subst(self.tcx(), substs);
-                p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
+                if NO_QUERIES.with(|q| q.get()) {
+                    p!(print_def_path(def_id, substs));
+                } else {
+                    let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
+                    p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
+                }
             }
             ty::FnPtr(ref bare_fn) => p!(print(bare_fn)),
             ty::Infer(infer_ty) => {
@@ -698,8 +701,10 @@ pub trait PrettyPrinter<'tcx>:
             ty::Error(_) => p!("[type error]"),
             ty::Param(ref param_ty) => p!(print(param_ty)),
             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
-                ty::BoundTyKind::Anon => self.pretty_print_bound_var(debruijn, bound_ty.var)?,
-                ty::BoundTyKind::Param(p) => p!(write("{}", p)),
+                ty::BoundTyKind::Anon(bv) => {
+                    self.pretty_print_bound_var(debruijn, ty::BoundVar::from_u32(bv))?
+                }
+                ty::BoundTyKind::Param(_, s) => p!(write("{}", s)),
             },
             ty::Adt(def, substs) => {
                 p!(print_def_path(def.did(), substs));
@@ -730,15 +735,18 @@ pub trait PrettyPrinter<'tcx>:
                     p!(print(data))
                 }
             }
-            ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
+            ty::Placeholder(placeholder) => match placeholder.name {
+                ty::BoundTyKind::Anon(_) => p!(write("Placeholder({:?})", placeholder)),
+                ty::BoundTyKind::Param(_, name) => p!(write("{}", name)),
+            },
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                // FIXME(eddyb) print this with `print_def_path`.
                 // We use verbose printing in 'NO_QUERIES' mode, to
                 // avoid needing to call `predicates_of`. This should
                 // only affect certain debug messages (e.g. messages printed
                 // from `rustc_middle::ty` during the computation of `tcx.predicates_of`),
                 // and should have no effect on any compiler output.
-                if self.should_print_verbose() || NO_QUERIES.with(|q| q.get()) {
+                if self.should_print_verbose() {
+                    // FIXME(eddyb) print this with `print_def_path`.
                     p!(write("Opaque({:?}, {:?})", def_id, substs));
                     return Ok(self);
                 }
@@ -746,8 +754,10 @@ pub trait PrettyPrinter<'tcx>:
                 let parent = self.tcx().parent(def_id);
                 match self.tcx().def_kind(parent) {
                     DefKind::TyAlias | DefKind::AssocTy => {
+                        // NOTE: I know we should check for NO_QUERIES here, but it's alright.
+                        // `type_of` on a type alias or assoc type should never cause a cycle.
                         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: d, .. }) =
-                            *self.tcx().type_of(parent).kind()
+                            *self.tcx().type_of(parent).subst_identity().kind()
                         {
                             if d == def_id {
                                 // If the type alias directly starts with the `impl` of the
@@ -760,7 +770,14 @@ pub trait PrettyPrinter<'tcx>:
                         p!(print_def_path(def_id, substs));
                         return Ok(self);
                     }
-                    _ => return self.pretty_print_opaque_impl_type(def_id, substs),
+                    _ => {
+                        if NO_QUERIES.with(|q| q.get()) {
+                            p!(print_def_path(def_id, &[]));
+                            return Ok(self);
+                        } else {
+                            return self.pretty_print_opaque_impl_type(def_id, substs);
+                        }
+                    }
                 }
             }
             ty::Str => p!("str"),
@@ -811,6 +828,28 @@ pub trait PrettyPrinter<'tcx>:
             ty::GeneratorWitness(types) => {
                 p!(in_binder(&types));
             }
+            ty::GeneratorWitnessMIR(did, substs) => {
+                p!(write("["));
+                if !self.tcx().sess.verbose() {
+                    p!("generator witness");
+                    // FIXME(eddyb) should use `def_span`.
+                    if let Some(did) = did.as_local() {
+                        let span = self.tcx().def_span(did);
+                        p!(write(
+                            "@{}",
+                            // This may end up in stderr diagnostics but it may also be emitted
+                            // into MIR. Hence we use the remapped path if available
+                            self.tcx().sess.source_map().span_to_embeddable_string(span)
+                        ));
+                    } else {
+                        p!(write("@"), print_def_path(did, substs));
+                    }
+                } else {
+                    p!(print_def_path(did, substs));
+                }
+
+                p!("]")
+            }
             ty::Closure(did, substs) => {
                 p!(write("["));
                 if !self.should_print_verbose() {
@@ -1062,9 +1101,11 @@ pub trait PrettyPrinter<'tcx>:
             write!(self, "Sized")?;
         }
 
-        for re in lifetimes {
-            write!(self, " + ")?;
-            self = self.print_region(re)?;
+        if !FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+            for re in lifetimes {
+                write!(self, " + ")?;
+                self = self.print_region(re)?;
+            }
         }
 
         Ok(self)
@@ -1171,7 +1212,7 @@ pub trait PrettyPrinter<'tcx>:
                 // in order to place the projections inside the `<...>`.
                 if !resugared {
                     // Use a type that can't appear in defaults of type parameters.
-                    let dummy_cx = cx.tcx().mk_ty_infer(ty::FreshTy(0));
+                    let dummy_cx = cx.tcx().mk_fresh_ty(0);
                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
 
                     let args = cx
@@ -1992,7 +2033,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         self.pretty_in_binder(value)
     }
@@ -2003,7 +2044,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         f: C,
     ) -> Result<Self, Self::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = Self::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         self.pretty_wrap_binder(value, f)
     }
@@ -2048,6 +2089,10 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
             return true;
         }
 
+        if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
+            return false;
+        }
+
         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
 
         match *region {
@@ -2071,7 +2116,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
             ty::ReVar(_) if identify_regions => true,
 
-            ty::ReVar(_) | ty::ReErased => false,
+            ty::ReVar(_) | ty::ReErased | ty::ReError(_) => false,
 
             ty::ReStatic => true,
         }
@@ -2151,6 +2196,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             }
             ty::ReVar(_) => {}
             ty::ReErased => {}
+            ty::ReError(_) => {}
             ty::ReStatic => {
                 p!("'static");
                 return Ok(self);
@@ -2178,12 +2224,12 @@ struct RegionFolder<'a, 'tcx> {
             ),
 }
 
-impl<'a, 'tcx> ty::TypeFolder<'tcx> for RegionFolder<'a, 'tcx> {
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn fold_binder<T: TypeFoldable<'tcx>>(
+    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
         &mut self,
         t: ty::Binder<'tcx, T>,
     ) -> ty::Binder<'tcx, T> {
@@ -2228,7 +2274,7 @@ impl<'a, 'tcx> ty::TypeFolder<'tcx> for RegionFolder<'a, 'tcx> {
         };
         if let ty::ReLateBound(debruijn1, br) = *region {
             assert_eq!(debruijn1, ty::INNERMOST);
-            self.tcx.mk_region(ty::ReLateBound(self.current_index, br))
+            self.tcx.mk_re_late_bound(self.current_index, br)
         } else {
             region
         }
@@ -2243,7 +2289,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         value: &ty::Binder<'tcx, T>,
     ) -> Result<(Self, T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>), fmt::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         fn name_by_region_index(
             index: usize,
@@ -2324,6 +2370,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         } else {
             let tcx = self.tcx;
 
+            let trim_path = FORCE_TRIMMED_PATH.with(|flag| flag.get());
             // Closure used in `RegionFolder` to create names for anonymous late-bound
             // regions. We use two `DebruijnIndex`es (one for the currently folded
             // late-bound region and the other for the binder level) to determine
@@ -2339,10 +2386,10 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = ty::BrNamed(CRATE_DEF_ID.to_def_id(), name);
-                                return tcx.mk_region(ty::ReLateBound(
+                                return tcx.mk_re_late_bound(
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
-                                ));
+                                );
                             }
                         }
 
@@ -2354,10 +2401,10 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = ty::BrNamed(def_id, name);
-                                return tcx.mk_region(ty::ReLateBound(
+                                return tcx.mk_re_late_bound(
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
-                                ));
+                                );
                             }
                         }
 
@@ -2367,10 +2414,10 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                         if let Some(lt_idx) = lifetime_idx {
                             if lt_idx > binder_level_idx {
                                 let kind = br.kind;
-                                return tcx.mk_region(ty::ReLateBound(
+                                return tcx.mk_re_late_bound(
                                     ty::INNERMOST,
                                     ty::BoundRegion { var: br.var, kind },
-                                ));
+                                );
                             }
                         }
 
@@ -2378,9 +2425,11 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                     }
                 };
 
-                start_or_continue(&mut self, "for<", ", ");
-                do_continue(&mut self, name);
-                tcx.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind }))
+                if !trim_path {
+                    start_or_continue(&mut self, "for<", ", ");
+                    do_continue(&mut self, name);
+                }
+                tcx.mk_re_late_bound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind })
             };
             let mut folder = RegionFolder {
                 tcx,
@@ -2390,7 +2439,9 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             };
             let new_value = value.clone().skip_binder().fold_with(&mut folder);
             let region_map = folder.region_map;
-            start_or_continue(&mut self, "", "> ");
+            if !trim_path {
+                start_or_continue(&mut self, "", "> ");
+            }
             (new_value, region_map)
         };
 
@@ -2401,7 +2452,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
 
     pub fn pretty_in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, fmt::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         let old_region_index = self.region_index;
         let (new, new_value, _) = self.name_all_regions(value)?;
@@ -2417,7 +2468,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         f: C,
     ) -> Result<Self, fmt::Error>
     where
-        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
+        T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<TyCtxt<'tcx>>,
     {
         let old_region_index = self.region_index;
         let (new, new_value, _) = self.name_all_regions(value)?;
@@ -2429,7 +2480,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
 
     fn prepare_region_info<T>(&mut self, value: &ty::Binder<'tcx, T>)
     where
-        T: TypeVisitable<'tcx>,
+        T: TypeVisitable<TyCtxt<'tcx>>,
     {
         struct RegionNameCollector<'tcx> {
             used_region_names: FxHashSet<Symbol>,
@@ -2445,7 +2496,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             }
         }
 
-        impl<'tcx> ty::visit::TypeVisitor<'tcx> for RegionNameCollector<'tcx> {
+        impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for RegionNameCollector<'tcx> {
             type BreakTy = ();
 
             fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
@@ -2482,7 +2533,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
 
 impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::Binder<'tcx, T>
 where
-    T: Print<'tcx, P, Output = P, Error = P::Error> + TypeFoldable<'tcx>,
+    T: Print<'tcx, P, Output = P, Error = P::Error> + TypeFoldable<TyCtxt<'tcx>>,
 {
     type Output = P;
     type Error = P::Error;
@@ -2648,7 +2699,7 @@ define_print_and_forward_display! {
 
     ty::ExistentialTraitRef<'tcx> {
         // Use a type that can't appear in defaults of type parameters.
-        let dummy_self = cx.tcx().mk_ty_infer(ty::FreshTy(0));
+        let dummy_self = cx.tcx().mk_fresh_ty(0);
         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
         p!(print(trait_ref.print_only_trait_path()))
     }
@@ -2774,15 +2825,18 @@ define_print_and_forward_display! {
             ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => p!(print(predicate)),
             ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => p!(print(predicate)),
             ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => p!(print(predicate)),
+            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(ct, ty)) => {
+                p!("the constant `", print(ct), "` has type `", print(ty), "`")
+            },
             ty::PredicateKind::WellFormed(arg) => p!(print(arg), " well-formed"),
             ty::PredicateKind::ObjectSafe(trait_def_id) => {
                 p!("the trait `", print_def_path(trait_def_id, &[]), "` is object-safe")
             }
-            ty::PredicateKind::ClosureKind(closure_def_id, _closure_substs, kind) => {
-                p!("the closure `",
+            ty::PredicateKind::ClosureKind(closure_def_id, _closure_substs, kind) => p!(
+                "the closure `",
                 print_value_path(closure_def_id, &[]),
-                write("` implements the trait `{}`", kind))
-            }
+                write("` implements the trait `{}`", kind)
+            ),
             ty::PredicateKind::ConstEvaluatable(ct) => {
                 p!("the constant `", print(ct), "` can be evaluated")
             }
@@ -2793,6 +2847,7 @@ define_print_and_forward_display! {
                 p!("the type `", print(ty), "` is found in the environment")
             }
             ty::PredicateKind::Ambiguous => p!("ambiguous"),
+            ty::PredicateKind::AliasEq(t1, t2) => p!(print(t1), " == ", print(t2)),
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/query.rs b/compiler/rustc_middle/src/ty/query.rs
index 9d4ee22a7..2bc51baf8 100644
--- a/compiler/rustc_middle/src/ty/query.rs
+++ b/compiler/rustc_middle/src/ty/query.rs
@@ -1,3 +1,5 @@
+#![allow(unused_parens)]
+
 use crate::dep_graph;
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
@@ -6,7 +8,7 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
 use crate::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use crate::middle::lib_features::LibFeatures;
 use crate::middle::privacy::EffectiveVisibilities;
-use crate::middle::resolve_lifetime::{ObjectLifetimeDefault, Region, ResolveLifetimes};
+use crate::middle::resolve_bound_vars::{ObjectLifetimeDefault, ResolveBoundVars, ResolvedArg};
 use crate::middle::stability::{self, DeprecationEntry};
 use crate::mir;
 use crate::mir::interpret::GlobalId;
@@ -30,11 +32,12 @@ use crate::traits::specialization_graph;
 use crate::traits::{self, ImplSource};
 use crate::ty::context::TyCtxtFeed;
 use crate::ty::fast_reject::SimplifiedType;
-use crate::ty::layout::TyAndLayout;
+use crate::ty::layout::ValidityRequirement;
 use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::GeneratorDiagnosticData;
 use crate::ty::{self, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt, UnusedGenericParams};
+use rustc_arena::TypedArena;
 use rustc_ast as ast;
 use rustc_ast::expand::allocator::AllocatorKind;
 use rustc_attr as attr;
@@ -42,10 +45,11 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
+use rustc_data_structures::sync::WorkerLocal;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
-use rustc_hir::def::DefKind;
+use rustc_hir::def::{DefKind, DocLinkResMap};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId};
 use rustc_hir::hir_id::OwnerId;
 use rustc_hir::lang_items::{LangItem, LanguageItems};
@@ -60,6 +64,7 @@ use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi;
 use rustc_target::spec::PanicStrategy;
+use std::mem;
 use std::ops::Deref;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -67,6 +72,12 @@ use std::sync::Arc;
 pub(crate) use rustc_query_system::query::QueryJobId;
 use rustc_query_system::query::*;
 
+#[derive(Default)]
+pub struct QuerySystem<'tcx> {
+    pub arenas: QueryArenas<'tcx>,
+    pub caches: QueryCaches<'tcx>,
+}
+
 #[derive(Copy, Clone)]
 pub struct TyCtxtAt<'tcx> {
     pub tcx: TyCtxt<'tcx>,
@@ -106,30 +117,21 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-/// Helper for `TyCtxtEnsure` to avoid a closure.
-#[inline(always)]
-fn noop<T>(_: &T) {}
-
-/// Helper to ensure that queries only return `Copy` types.
-#[inline(always)]
-fn copy<T: Copy>(x: &T) -> T {
-    *x
-}
-
 macro_rules! query_helper_param_ty {
     (DefId) => { impl IntoQueryParam<DefId> };
+    (LocalDefId) => { impl IntoQueryParam<LocalDefId> };
     ($K:ty) => { $K };
 }
 
-macro_rules! query_storage {
-    ([][$K:ty, $V:ty]) => {
-        <<$K as Key>::CacheSelector as CacheSelector<'tcx, $V>>::Cache
+macro_rules! query_if_arena {
+    ([] $arena:tt $no_arena:tt) => {
+        $no_arena
     };
-    ([(arena_cache) $($rest:tt)*][$K:ty, $V:ty]) => {
-        <<$K as Key>::CacheSelector as CacheSelector<'tcx, $V>>::ArenaCache
+    ([(arena_cache) $($rest:tt)*] $arena:tt $no_arena:tt) => {
+        $arena
     };
-    ([$other:tt $($modifiers:tt)*][$($args:tt)*]) => {
-        query_storage!([$($modifiers)*][$($args)*])
+    ([$other:tt $($modifiers:tt)*]$($args:tt)*) => {
+        query_if_arena!([$($modifiers)*]$($args)*)
     };
 }
 
@@ -141,7 +143,7 @@ macro_rules! separate_provide_extern_decl {
         for<'tcx> fn(
             TyCtxt<'tcx>,
             query_keys::$name<'tcx>,
-        ) -> query_values::$name<'tcx>
+        ) -> query_provided::$name<'tcx>
     };
     ([$other:tt $($modifiers:tt)*][$($args:tt)*]) => {
         separate_provide_extern_decl!([$($modifiers)*][$($args)*])
@@ -199,17 +201,71 @@ macro_rules! define_callbacks {
 
             $(pub type $name<'tcx> = $V;)*
         }
+
+        /// This module specifies the type returned from query providers and the type used for
+        /// decoding. For regular queries this is the declared returned type `V`, but
+        /// `arena_cache` will use `<V as Deref>::Target` instead.
         #[allow(nonstandard_style, unused_lifetimes)]
-        pub mod query_storage {
+        pub mod query_provided {
             use super::*;
 
-            $(pub type $name<'tcx> = query_storage!([$($modifiers)*][$($K)*, $V]);)*
+            $(
+                pub type $name<'tcx> = query_if_arena!([$($modifiers)*] (<$V as Deref>::Target) ($V));
+            )*
         }
+
+        /// This module has a function per query which takes a `query_provided` value and coverts
+        /// it to a regular `V` value by allocating it on an arena if the query has the
+        /// `arena_cache` modifier. This will happen when computing the query using a provider or
+        /// decoding a stored result.
         #[allow(nonstandard_style, unused_lifetimes)]
-        pub mod query_stored {
+        pub mod query_provided_to_value {
             use super::*;
 
-            $(pub type $name<'tcx> = <query_storage::$name<'tcx> as QueryStorage>::Stored;)*
+            $(
+                #[inline(always)]
+                pub fn $name<'tcx>(
+                    _tcx: TyCtxt<'tcx>,
+                    value: query_provided::$name<'tcx>,
+                ) -> query_values::$name<'tcx> {
+                    query_if_arena!([$($modifiers)*]
+                        {
+                            if mem::needs_drop::<query_provided::$name<'tcx>>() {
+                                &*_tcx.query_system.arenas.$name.alloc(value)
+                            } else {
+                                &*_tcx.arena.dropless.alloc(value)
+                            }
+                        }
+                        (value)
+                    )
+                }
+            )*
+        }
+        #[allow(nonstandard_style, unused_lifetimes)]
+        pub mod query_storage {
+            use super::*;
+
+            $(
+                pub type $name<'tcx> = <<$($K)* as Key>::CacheSelector as CacheSelector<'tcx, $V>>::Cache;
+            )*
+        }
+
+        pub struct QueryArenas<'tcx> {
+            $($(#[$attr])* pub $name: query_if_arena!([$($modifiers)*]
+                (WorkerLocal<TypedArena<<$V as Deref>::Target>>)
+                ()
+            ),)*
+        }
+
+        impl Default for QueryArenas<'_> {
+            fn default() -> Self {
+                Self {
+                    $($name: query_if_arena!([$($modifiers)*]
+                        (WorkerLocal::new(|_| Default::default()))
+                        ()
+                    ),)*
+                }
+            }
         }
 
         #[derive(Default)]
@@ -224,14 +280,10 @@ macro_rules! define_callbacks {
                 let key = key.into_query_param();
                 opt_remap_env_constness!([$($modifiers)*][key]);
 
-                let cached = try_get_cached(self.tcx, &self.tcx.query_caches.$name, &key, noop);
-
-                match cached {
-                    Ok(()) => return,
-                    Err(()) => (),
-                }
-
-                self.tcx.queries.$name(self.tcx, DUMMY_SP, key, QueryMode::Ensure);
+                match try_get_cached(self.tcx, &self.tcx.query_system.caches.$name, &key) {
+                    Some(_) => return,
+                    None => self.tcx.queries.$name(self.tcx, DUMMY_SP, key, QueryMode::Ensure),
+                };
             })*
         }
 
@@ -239,7 +291,7 @@ macro_rules! define_callbacks {
             $($(#[$attr])*
             #[inline(always)]
             #[must_use]
-            pub fn $name(self, key: query_helper_param_ty!($($K)*)) -> query_stored::$name<'tcx>
+            pub fn $name(self, key: query_helper_param_ty!($($K)*)) -> $V
             {
                 self.at(DUMMY_SP).$name(key)
             })*
@@ -248,19 +300,15 @@ macro_rules! define_callbacks {
         impl<'tcx> TyCtxtAt<'tcx> {
             $($(#[$attr])*
             #[inline(always)]
-            pub fn $name(self, key: query_helper_param_ty!($($K)*)) -> query_stored::$name<'tcx>
+            pub fn $name(self, key: query_helper_param_ty!($($K)*)) -> $V
             {
                 let key = key.into_query_param();
                 opt_remap_env_constness!([$($modifiers)*][key]);
 
-                let cached = try_get_cached(self.tcx, &self.tcx.query_caches.$name, &key, copy);
-
-                match cached {
-                    Ok(value) => return value,
-                    Err(()) => (),
+                match try_get_cached(self.tcx, &self.tcx.query_system.caches.$name, &key) {
+                    Some(value) => value,
+                    None => self.tcx.queries.$name(self.tcx, self.span, key, QueryMode::Get).unwrap(),
                 }
-
-                self.tcx.queries.$name(self.tcx, self.span, key, QueryMode::Get).unwrap()
             })*
         }
 
@@ -268,7 +316,7 @@ macro_rules! define_callbacks {
             $(pub $name: for<'tcx> fn(
                 TyCtxt<'tcx>,
                 query_keys::$name<'tcx>,
-            ) -> query_values::$name<'tcx>,)*
+            ) -> query_provided::$name<'tcx>,)*
         }
 
         pub struct ExternProviders {
@@ -281,8 +329,9 @@ macro_rules! define_callbacks {
 
                 Providers {
                     $($name: |_, key| bug!(
-                        "`tcx.{}({:?})` is not supported for {} crate;\n
-                        hint: Queries can be either made to the local crate, or the external crate. This error means you tried to use it for one that's not supported.\n
+                        "`tcx.{}({:?})` is not supported for {} crate;\n\
+                        hint: Queries can be either made to the local crate, or the external crate. \
+                        This error means you tried to use it for one that's not supported.\n\
                         If that's not the case, {} was likely never assigned to a provider function.\n",
                         stringify!($name),
                         key,
@@ -323,7 +372,7 @@ macro_rules! define_callbacks {
                 span: Span,
                 key: query_keys::$name<'tcx>,
                 mode: QueryMode,
-            ) -> Option<query_stored::$name<'tcx>>;)*
+            ) -> Option<$V>;)*
         }
     };
 }
@@ -345,34 +394,34 @@ macro_rules! define_feedable {
         $(impl<'tcx, K: IntoQueryParam<$($K)*> + Copy> TyCtxtFeed<'tcx, K> {
             $(#[$attr])*
             #[inline(always)]
-            pub fn $name(self, value: $V) -> query_stored::$name<'tcx> {
+            pub fn $name(self, value: query_provided::$name<'tcx>) -> $V {
                 let key = self.key().into_query_param();
                 opt_remap_env_constness!([$($modifiers)*][key]);
 
                 let tcx = self.tcx;
-                let cache = &tcx.query_caches.$name;
-
-                let cached = try_get_cached(tcx, cache, &key, copy);
+                let value = query_provided_to_value::$name(tcx, value);
+                let cache = &tcx.query_system.caches.$name;
 
-                match cached {
-                    Ok(old) => {
+                match try_get_cached(tcx, cache, &key) {
+                    Some(old) => {
                         bug!(
                             "Trying to feed an already recorded value for query {} key={key:?}:\nold value: {old:?}\nnew value: {value:?}",
                             stringify!($name),
+                        )
+                    }
+                    None => {
+                        let dep_node = dep_graph::DepNode::construct(tcx, dep_graph::DepKind::$name, &key);
+                        let dep_node_index = tcx.dep_graph.with_feed_task(
+                            dep_node,
+                            tcx,
+                            key,
+                            &value,
+                            hash_result!([$($modifiers)*]),
                         );
+                        cache.complete(key, value, dep_node_index);
+                        value
                     }
-                    Err(()) => (),
                 }
-
-                let dep_node = dep_graph::DepNode::construct(tcx, dep_graph::DepKind::$name, &key);
-                let dep_node_index = tcx.dep_graph.with_feed_task(
-                    dep_node,
-                    tcx,
-                    key,
-                    &value,
-                    hash_result!([$($modifiers)*]),
-                );
-                cache.complete(key, value, dep_node_index)
             }
         })*
     }
@@ -418,6 +467,13 @@ mod sealed {
         }
     }
 
+    impl IntoQueryParam<LocalDefId> for OwnerId {
+        #[inline(always)]
+        fn into_query_param(self) -> LocalDefId {
+            self.def_id
+        }
+    }
+
     impl IntoQueryParam<DefId> for LocalDefId {
         #[inline(always)]
         fn into_query_param(self) -> DefId {
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 65fd8d975..3fc5f5bed 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -9,7 +9,6 @@ use crate::ty::{self, Expr, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldabl
 use crate::ty::{GenericArg, GenericArgKind, SubstsRef};
 use rustc_hir as ast;
 use rustc_hir::def_id::DefId;
-use rustc_span::DUMMY_SP;
 use rustc_target::spec::abi;
 use std::iter;
 
@@ -106,7 +105,7 @@ pub trait TypeRelation<'tcx>: Sized {
         T: Relate<'tcx>;
 }
 
-pub trait Relate<'tcx>: TypeFoldable<'tcx> + PartialEq + Copy {
+pub trait Relate<'tcx>: TypeFoldable<TyCtxt<'tcx>> + PartialEq + Copy {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
         a: Self,
@@ -145,7 +144,7 @@ pub fn relate_substs<'tcx, R: TypeRelation<'tcx>>(
     a_subst: SubstsRef<'tcx>,
     b_subst: SubstsRef<'tcx>,
 ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
-    relation.tcx().mk_substs(iter::zip(a_subst, b_subst).map(|(a, b)| {
+    relation.tcx().mk_substs_from_iter(iter::zip(a_subst, b_subst).map(|(a, b)| {
         relation.relate_with_variance(ty::Invariant, ty::VarianceDiagInfo::default(), a, b)
     }))
 }
@@ -164,8 +163,7 @@ pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>(
     let params = iter::zip(a_subst, b_subst).enumerate().map(|(i, (a, b))| {
         let variance = variances[i];
         let variance_info = if variance == ty::Invariant && fetch_ty_for_diag {
-            let ty =
-                *cached_ty.get_or_insert_with(|| tcx.bound_type_of(ty_def_id).subst(tcx, a_subst));
+            let ty = *cached_ty.get_or_insert_with(|| tcx.type_of(ty_def_id).subst(tcx, a_subst));
             ty::VarianceDiagInfo::Invariant { ty, param_index: i.try_into().unwrap() }
         } else {
             ty::VarianceDiagInfo::default()
@@ -173,7 +171,7 @@ pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>(
         relation.relate_with_variance(variance, variance_info, a, b)
     });
 
-    tcx.mk_substs(params)
+    tcx.mk_substs_from_iter(params)
 }
 
 impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
@@ -224,7 +222,7 @@ impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
                 r => r,
             });
         Ok(ty::FnSig {
-            inputs_and_output: tcx.mk_type_list(inputs_and_output)?,
+            inputs_and_output: tcx.mk_type_list_from_iter(inputs_and_output)?,
             c_variadic: a.c_variadic,
             unsafety,
             abi,
@@ -354,7 +352,8 @@ impl<'tcx> Relate<'tcx> for GeneratorWitness<'tcx> {
     ) -> RelateResult<'tcx, GeneratorWitness<'tcx>> {
         assert_eq!(a.0.len(), b.0.len());
         let tcx = relation.tcx();
-        let types = tcx.mk_type_list(iter::zip(a.0, b.0).map(|(a, b)| relation.relate(a, b)))?;
+        let types =
+            tcx.mk_type_list_from_iter(iter::zip(a.0, b.0).map(|(a, b)| relation.relate(a, b)))?;
         Ok(GeneratorWitness(types))
     }
 }
@@ -414,7 +413,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             bug!("bound types encountered in super_relate_tys")
         }
 
-        (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error_with_guaranteed(guar)),
+        (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error(guar)),
 
         (&ty::Never, _)
         | (&ty::Char, _)
@@ -443,12 +442,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             if a_repr == b_repr =>
         {
             let region_bound = relation.with_cause(Cause::ExistentialRegionBound, |relation| {
-                relation.relate_with_variance(
-                    ty::Contravariant,
-                    ty::VarianceDiagInfo::default(),
-                    a_region,
-                    b_region,
-                )
+                relation.relate(a_region, b_region)
             })?;
             Ok(tcx.mk_dynamic(relation.relate(a_obj, b_obj)?, region_bound, a_repr))
         }
@@ -473,6 +467,16 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(tcx.mk_generator_witness(types))
         }
 
+        (&ty::GeneratorWitnessMIR(a_id, a_substs), &ty::GeneratorWitnessMIR(b_id, b_substs))
+            if a_id == b_id =>
+        {
+            // All GeneratorWitness types with the same id represent
+            // the (anonymous) type of the same generator expression. So
+            // all of their regions should be equated.
+            let substs = relation.relate(a_substs, b_substs)?;
+            Ok(tcx.mk_generator_witness_mir(a_id, substs))
+        }
+
         (&ty::Closure(a_id, a_substs), &ty::Closure(b_id, b_substs)) if a_id == b_id => {
             // All Closure types with the same id represent
             // the (anonymous) type of the same closure expression. So
@@ -487,12 +491,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
         }
 
         (&ty::Ref(a_r, a_ty, a_mutbl), &ty::Ref(b_r, b_ty, b_mutbl)) => {
-            let r = relation.relate_with_variance(
-                ty::Contravariant,
-                ty::VarianceDiagInfo::default(),
-                a_r,
-                b_r,
-            )?;
+            let r = relation.relate(a_r, b_r)?;
             let a_mt = ty::TypeAndMut { ty: a_ty, mutbl: a_mutbl };
             let b_mt = ty::TypeAndMut { ty: b_ty, mutbl: b_mutbl };
             let mt = relate_type_and_mut(relation, a_mt, b_mt, a)?;
@@ -502,7 +501,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
         (&ty::Array(a_t, sz_a), &ty::Array(b_t, sz_b)) => {
             let t = relation.relate(a_t, b_t)?;
             match relation.relate(sz_a, sz_b) {
-                Ok(sz) => Ok(tcx.mk_ty(ty::Array(t, sz))),
+                Ok(sz) => Ok(tcx.mk_array_with_const_len(t, sz)),
                 Err(err) => {
                     // Check whether the lengths are both concrete/known values,
                     // but are unequal, for better diagnostics.
@@ -511,8 +510,8 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
                     // we however cannot end up with errors in `Relate` during both
                     // `type_of` and `predicates_of`. This means that evaluating the
                     // constants should not cause cycle errors here.
-                    let sz_a = sz_a.try_eval_usize(tcx, relation.param_env());
-                    let sz_b = sz_b.try_eval_usize(tcx, relation.param_env());
+                    let sz_a = sz_a.try_eval_target_usize(tcx, relation.param_env());
+                    let sz_b = sz_b.try_eval_target_usize(tcx, relation.param_env());
                     match (sz_a, sz_b) {
                         (Some(sz_a_val), Some(sz_b_val)) if sz_a_val != sz_b_val => Err(
                             TypeError::FixedArraySize(expected_found(relation, sz_a_val, sz_b_val)),
@@ -530,7 +529,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
 
         (&ty::Tuple(as_), &ty::Tuple(bs)) => {
             if as_.len() == bs.len() {
-                Ok(tcx.mk_tup(iter::zip(as_, bs).map(|(a, b)| relation.relate(a, b)))?)
+                Ok(tcx.mk_tup_from_iter(iter::zip(as_, bs).map(|(a, b)| relation.relate(a, b)))?)
             } else if !(as_.is_empty() || bs.is_empty()) {
                 Err(TypeError::TupleSize(expected_found(relation, as_.len(), bs.len())))
             } else {
@@ -594,25 +593,6 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
     debug!("{}.super_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b);
     let tcx = relation.tcx();
 
-    let a_ty;
-    let b_ty;
-    if relation.tcx().features().adt_const_params {
-        a_ty = tcx.normalize_erasing_regions(relation.param_env(), a.ty());
-        b_ty = tcx.normalize_erasing_regions(relation.param_env(), b.ty());
-    } else {
-        a_ty = tcx.erase_regions(a.ty());
-        b_ty = tcx.erase_regions(b.ty());
-    }
-    if a_ty != b_ty {
-        relation.tcx().sess.delay_span_bug(
-            DUMMY_SP,
-            &format!(
-                "cannot relate constants ({:?}, {:?}) of different types: {} != {}",
-                a, b, a_ty, b_ty
-            ),
-        );
-    }
-
     // HACK(const_generics): We still need to eagerly evaluate consts when
     // relating them because during `normalize_param_env_or_error`,
     // we may relate an evaluated constant in a obligation against
@@ -629,6 +609,8 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
         b = tcx.expand_abstract_consts(b);
     }
 
+    debug!("{}.super_relate_consts(normed_a = {:?}, normed_b = {:?})", relation.tag(), a, b);
+
     // Currently, the values that can be unified are primitive types,
     // and those that derive both `PartialEq` and `Eq`, corresponding
     // to structural-match types.
@@ -665,36 +647,34 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
 
             // FIXME(generic_const_exprs): is it possible to relate two consts which are not identical
             // exprs? Should we care about that?
+            // FIXME(generic_const_exprs): relating the `ty()`s is a little weird since it is supposed to
+            // ICE If they mismatch. Unfortunately `ConstKind::Expr` is a little special and can be thought
+            // of as being generic over the argument types, however this is implicit so these types don't get
+            // related when we relate the substs of the item this const arg is for.
             let expr = match (ae, be) {
-                (Expr::Binop(a_op, al, ar), Expr::Binop(b_op, bl, br))
-                    if a_op == b_op && al.ty() == bl.ty() && ar.ty() == br.ty() =>
-                {
+                (Expr::Binop(a_op, al, ar), Expr::Binop(b_op, bl, br)) if a_op == b_op => {
+                    r.relate(al.ty(), bl.ty())?;
+                    r.relate(ar.ty(), br.ty())?;
                     Expr::Binop(a_op, r.consts(al, bl)?, r.consts(ar, br)?)
                 }
-                (Expr::UnOp(a_op, av), Expr::UnOp(b_op, bv))
-                    if a_op == b_op && av.ty() == bv.ty() =>
-                {
+                (Expr::UnOp(a_op, av), Expr::UnOp(b_op, bv)) if a_op == b_op => {
+                    r.relate(av.ty(), bv.ty())?;
                     Expr::UnOp(a_op, r.consts(av, bv)?)
                 }
-                (Expr::Cast(ak, av, at), Expr::Cast(bk, bv, bt))
-                    if ak == bk && av.ty() == bv.ty() =>
-                {
+                (Expr::Cast(ak, av, at), Expr::Cast(bk, bv, bt)) if ak == bk => {
+                    r.relate(av.ty(), bv.ty())?;
                     Expr::Cast(ak, r.consts(av, bv)?, r.tys(at, bt)?)
                 }
                 (Expr::FunctionCall(af, aa), Expr::FunctionCall(bf, ba))
-                    if aa.len() == ba.len()
-                        && af.ty() == bf.ty()
-                        && aa
-                            .iter()
-                            .zip(ba.iter())
-                            .all(|(a_arg, b_arg)| a_arg.ty() == b_arg.ty()) =>
+                    if aa.len() == ba.len() =>
                 {
+                    r.relate(af.ty(), bf.ty())?;
                     let func = r.consts(af, bf)?;
                     let mut related_args = Vec::with_capacity(aa.len());
                     for (a_arg, b_arg) in aa.iter().zip(ba.iter()) {
                         related_args.push(r.consts(a_arg, b_arg)?);
                     }
-                    let related_args = tcx.mk_const_list(related_args.iter());
+                    let related_args = tcx.mk_const_list(&related_args);
                     Expr::FunctionCall(func, related_args)
                 }
                 _ => return Err(TypeError::ConstMismatch(expected_found(r, a, b))),
@@ -741,7 +721,7 @@ impl<'tcx> Relate<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
                 _ => Err(TypeError::ExistentialMismatch(expected_found(relation, a, b))),
             }
         });
-        tcx.mk_poly_existential_predicates(v)
+        tcx.mk_poly_existential_predicates_from_iter(v)
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 7d4d35b7f..ef643531b 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -1,6 +1,7 @@
-//! This module contains implements of the `Lift` and `TypeFoldable`
-//! traits for various types in the Rust compiler. Most are written by
-//! hand, though we've recently added some macros and proc-macros to help with the tedium.
+//! This module contains implementations of the `Lift`, `TypeFoldable` and
+//! `TypeVisitable` traits for various types in the Rust compiler. Most are
+//! written by hand, though we've recently added some macros and proc-macros
+//! to help with the tedium.
 
 use crate::mir::interpret;
 use crate::mir::{Field, ProjectionKind};
@@ -8,12 +9,11 @@ use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use crate::ty::{self, AliasTy, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
-use rustc_data_structures::functor::IdFunctor;
 use rustc_hir::def::Namespace;
 use rustc_index::vec::{Idx, IndexVec};
+use rustc_target::abi::TyAndLayout;
 
 use std::fmt;
-use std::mem::ManuallyDrop;
 use std::ops::ControlFlow;
 use std::rc::Rc;
 use std::sync::Arc;
@@ -147,6 +147,7 @@ impl<'tcx> fmt::Debug for ty::Predicate<'tcx> {
 impl<'tcx> fmt::Debug for ty::Clause<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
+            ty::Clause::ConstArgHasType(ct, ty) => write!(f, "ConstArgHasType({ct:?}, {ty:?})"),
             ty::Clause::Trait(ref a) => a.fmt(f),
             ty::Clause::RegionOutlives(ref pair) => pair.fmt(f),
             ty::Clause::TypeOutlives(ref pair) => pair.fmt(f),
@@ -176,6 +177,7 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
             }
             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
+            ty::PredicateKind::AliasEq(t1, t2) => write!(f, "AliasEq({t1:?}, {t2:?})"),
         }
     }
 }
@@ -193,16 +195,27 @@ impl<'tcx> fmt::Debug for AliasTy<'tcx> {
 // Atomic structs
 //
 // For things that don't carry any arena-allocated data (and are
-// copy...), just add them to this list.
+// copy...), just add them to one of these lists as appropriat.
 
-TrivialTypeTraversalAndLiftImpls! {
+// For things for which the type library provides traversal implementations
+// for all Interners, we only need to provide a Lift implementation:
+CloneLiftImpls! {
     (),
     bool,
     usize,
-    ::rustc_target::abi::VariantIdx,
+    u16,
     u32,
     u64,
     String,
+    rustc_type_ir::DebruijnIndex,
+}
+
+// For things about which the type library does not know, or does not
+// provide any traversal implementations, we need to provide both a Lift
+// implementation and traversal implementations (the latter only for
+// TyCtxt<'_> interners).
+TrivialTypeTraversalAndLiftImpls! {
+    ::rustc_target::abi::VariantIdx,
     crate::middle::region::Scope,
     crate::ty::FloatTy,
     ::rustc_ast::InlineAsmOptions,
@@ -238,6 +251,7 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::AssocKind,
     crate::ty::AliasKind,
     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
+    crate::ty::Placeholder<crate::ty::BoundTyKind>,
     crate::ty::ClosureKind,
     crate::ty::FreeRegion,
     crate::ty::InferTy,
@@ -249,11 +263,11 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::UniverseIndex,
     crate::ty::Variance,
     ::rustc_span::Span,
+    ::rustc_span::symbol::Ident,
     ::rustc_errors::ErrorGuaranteed,
     Field,
     interpret::Scalar,
     rustc_target::abi::Size,
-    rustc_type_ir::DebruijnIndex,
     ty::BoundVar,
     ty::Placeholder<ty::BoundVar>,
 }
@@ -356,281 +370,106 @@ impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 }
 
 ///////////////////////////////////////////////////////////////////////////
-// TypeFoldable implementations.
+// Traversal implementations.
 
 /// AdtDefs are basically the same as a DefId.
-impl<'tcx> TypeFoldable<'tcx> for ty::AdtDef<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::AdtDef<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        _folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for ty::AdtDef<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::AdtDef<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        _visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         ControlFlow::Continue(())
     }
 }
 
-impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> TypeFoldable<TyCtxt<'tcx>> for ty::Binder<'tcx, T> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
-    ) -> Result<(T, U), F::Error> {
-        Ok((self.0.try_fold_with(folder)?, self.1.try_fold_with(folder)?))
+    ) -> Result<Self, F::Error> {
+        folder.try_fold_binder(self)
     }
 }
 
-impl<'tcx, T: TypeVisitable<'tcx>, U: TypeVisitable<'tcx>> TypeVisitable<'tcx> for (T, U) {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.0.visit_with(visitor)?;
-        self.1.visit_with(visitor)
+impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitable<TyCtxt<'tcx>> for ty::Binder<'tcx, T> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        visitor.visit_binder(self)
     }
 }
 
-impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
-    for (A, B, C)
-{
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Binder<'tcx, T> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
-    ) -> Result<(A, B, C), F::Error> {
-        Ok((
-            self.0.try_fold_with(folder)?,
-            self.1.try_fold_with(folder)?,
-            self.2.try_fold_with(folder)?,
-        ))
+    ) -> Result<Self, F::Error> {
+        self.try_map_bound(|ty| ty.try_fold_with(folder))
     }
 }
 
-impl<'tcx, A: TypeVisitable<'tcx>, B: TypeVisitable<'tcx>, C: TypeVisitable<'tcx>>
-    TypeVisitable<'tcx> for (A, B, C)
+impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeSuperVisitable<TyCtxt<'tcx>>
+    for ty::Binder<'tcx, T>
 {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.0.visit_with(visitor)?;
-        self.1.visit_with(visitor)?;
-        self.2.visit_with(visitor)
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
+        self.as_ref().skip_binder().visit_with(visitor)
     }
 }
 
-EnumTypeTraversalImpl! {
-    impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
-        (Some)(a),
-        (None),
-    } where T: TypeFoldable<'tcx>
-}
-EnumTypeTraversalImpl! {
-    impl<'tcx, T> TypeVisitable<'tcx> for Option<T> {
-        (Some)(a),
-        (None),
-    } where T: TypeVisitable<'tcx>
-}
-
-EnumTypeTraversalImpl! {
-    impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
-        (Ok)(a),
-        (Err)(a),
-    } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
-}
-EnumTypeTraversalImpl! {
-    impl<'tcx, T, E> TypeVisitable<'tcx> for Result<T, E> {
-        (Ok)(a),
-        (Err)(a),
-    } where T: TypeVisitable<'tcx>, E: TypeVisitable<'tcx>,
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
-        mut self,
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        // We merely want to replace the contained `T`, if at all possible,
-        // so that we don't needlessly allocate a new `Rc` or indeed clone
-        // the contained type.
-        unsafe {
-            // First step is to ensure that we have a unique reference to
-            // the contained type, which `Rc::make_mut` will accomplish (by
-            // allocating a new `Rc` and cloning the `T` only if required).
-            // This is done *before* casting to `Rc<ManuallyDrop<T>>` so that
-            // panicking during `make_mut` does not leak the `T`.
-            Rc::make_mut(&mut self);
-
-            // Casting to `Rc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
-            // is `repr(transparent)`.
-            let ptr = Rc::into_raw(self).cast::<ManuallyDrop<T>>();
-            let mut unique = Rc::from_raw(ptr);
-
-            // Call to `Rc::make_mut` above guarantees that `unique` is the
-            // sole reference to the contained value, so we can avoid doing
-            // a checked `get_mut` here.
-            let slot = Rc::get_mut_unchecked(&mut unique);
-
-            // Semantically move the contained type out from `unique`, fold
-            // it, then move the folded value back into `unique`. Should
-            // folding fail, `ManuallyDrop` ensures that the "moved-out"
-            // value is not re-dropped.
-            let owned = ManuallyDrop::take(slot);
-            let folded = owned.try_fold_with(folder)?;
-            *slot = ManuallyDrop::new(folded);
-
-            // Cast back to `Rc<T>`.
-            Ok(Rc::from_raw(Rc::into_raw(unique).cast()))
-        }
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_poly_existential_predicates(v))
     }
 }
 
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Rc<T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        (**self).visit_with(visitor)
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
-        mut self,
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::Const<'tcx>> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        // We merely want to replace the contained `T`, if at all possible,
-        // so that we don't needlessly allocate a new `Arc` or indeed clone
-        // the contained type.
-        unsafe {
-            // First step is to ensure that we have a unique reference to
-            // the contained type, which `Arc::make_mut` will accomplish (by
-            // allocating a new `Arc` and cloning the `T` only if required).
-            // This is done *before* casting to `Arc<ManuallyDrop<T>>` so that
-            // panicking during `make_mut` does not leak the `T`.
-            Arc::make_mut(&mut self);
-
-            // Casting to `Arc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
-            // is `repr(transparent)`.
-            let ptr = Arc::into_raw(self).cast::<ManuallyDrop<T>>();
-            let mut unique = Arc::from_raw(ptr);
-
-            // Call to `Arc::make_mut` above guarantees that `unique` is the
-            // sole reference to the contained value, so we can avoid doing
-            // a checked `get_mut` here.
-            let slot = Arc::get_mut_unchecked(&mut unique);
-
-            // Semantically move the contained type out from `unique`, fold
-            // it, then move the folded value back into `unique`. Should
-            // folding fail, `ManuallyDrop` ensures that the "moved-out"
-            // value is not re-dropped.
-            let owned = ManuallyDrop::take(slot);
-            let folded = owned.try_fold_with(folder)?;
-            *slot = ManuallyDrop::new(folded);
-
-            // Cast back to `Arc<T>`.
-            Ok(Arc::from_raw(Arc::into_raw(unique).cast()))
-        }
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Arc<T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        (**self).visit_with(visitor)
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        self.try_map_id(|value| value.try_fold_with(folder))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        (**self).visit_with(visitor)
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        self.try_map_id(|t| t.try_fold_with(folder))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Vec<T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.iter().try_for_each(|t| t.visit_with(visitor))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &[T] {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.iter().try_for_each(|t| t.visit_with(visitor))
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        self.try_map_id(|t| t.try_fold_with(folder))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<[T]> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.iter().try_for_each(|t| t.visit_with(visitor))
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_const_list(v))
     }
 }
 
-impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        folder.try_fold_binder(self)
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for ty::Binder<'tcx, T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        visitor.visit_binder(self)
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>> TypeSuperFoldable<'tcx> for ty::Binder<'tcx, T> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ProjectionKind> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        self.try_map_bound(|ty| ty.try_fold_with(folder))
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_projs(v))
     }
 }
 
-impl<'tcx, T: TypeVisitable<'tcx>> TypeSuperVisitable<'tcx> for ty::Binder<'tcx, T> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.as_ref().skip_binder().visit_with(visitor)
-    }
-}
-
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_poly_existential_predicates(v))
-    }
-}
-
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Const<'tcx>> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_const_list(v.iter()))
-    }
-}
-
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_projs(v))
-    }
-}
-
-impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Ty<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         folder.try_fold_ty(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for Ty<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Ty<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         visitor.visit_ty(*self)
     }
 }
 
-impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for Ty<'tcx> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -654,6 +493,9 @@ impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
                 ty::Generator(did, substs.try_fold_with(folder)?, movability)
             }
             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.try_fold_with(folder)?),
+            ty::GeneratorWitnessMIR(did, substs) => {
+                ty::GeneratorWitnessMIR(did, substs.try_fold_with(folder)?)
+            }
             ty::Closure(did, substs) => ty::Closure(did, substs.try_fold_with(folder)?),
             ty::Alias(kind, data) => ty::Alias(kind, data.try_fold_with(folder)?),
 
@@ -672,12 +514,15 @@ impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
             | ty::Foreign(..) => return Ok(self),
         };
 
-        Ok(if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) })
+        Ok(if *self.kind() == kind { self } else { folder.interner().mk_ty_from_kind(kind) })
     }
 }
 
-impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for Ty<'tcx> {
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         match self.kind() {
             ty::RawPtr(ref tm) => tm.visit_with(visitor),
             ty::Array(typ, sz) => {
@@ -699,6 +544,7 @@ impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
             }
             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
+            ty::GeneratorWitnessMIR(_did, ref substs) => substs.visit_with(visitor),
             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
             ty::Alias(_, ref data) => data.visit_with(visitor),
 
@@ -719,20 +565,23 @@ impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Region<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         folder.try_fold_region(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for ty::Region<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Region<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         visitor.visit_region(*self)
     }
 }
 
-impl<'tcx> TypeSuperFoldable<'tcx> for ty::Region<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Region<'tcx> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         _folder: &mut F,
     ) -> Result<Self, F::Error> {
@@ -740,116 +589,127 @@ impl<'tcx> TypeSuperFoldable<'tcx> for ty::Region<'tcx> {
     }
 }
 
-impl<'tcx> TypeSuperVisitable<'tcx> for ty::Region<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Region<'tcx> {
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        _visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         ControlFlow::Continue(())
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         folder.try_fold_predicate(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for ty::Predicate<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         visitor.visit_predicate(*self)
     }
-
-    #[inline]
-    fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
-        self.outer_exclusive_binder() > binder
-    }
-
-    #[inline]
-    fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
-        self.flags().intersects(flags)
-    }
 }
 
-impl<'tcx> TypeSuperFoldable<'tcx> for ty::Predicate<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
         let new = self.kind().try_fold_with(folder)?;
-        Ok(folder.tcx().reuse_or_mk_predicate(self, new))
+        Ok(folder.interner().reuse_or_mk_predicate(self, new))
     }
 }
 
-impl<'tcx> TypeSuperVisitable<'tcx> for ty::Predicate<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         self.kind().visit_with(visitor)
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_predicates(v))
-    }
-}
-
-impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        self.try_map_id(|x| x.try_fold_with(folder))
-    }
-}
-
-impl<'tcx, T: TypeVisitable<'tcx>, I: Idx> TypeVisitable<'tcx> for IndexVec<I, T> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.iter().try_for_each(|t| t.visit_with(visitor))
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::Predicate<'tcx>> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_predicates(v))
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ty::Const<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         folder.try_fold_const(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for ty::Const<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Const<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         visitor.visit_const(*self)
     }
 }
 
-impl<'tcx> TypeSuperFoldable<'tcx> for ty::Const<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
+impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
         let ty = self.ty().try_fold_with(folder)?;
         let kind = self.kind().try_fold_with(folder)?;
         if ty != self.ty() || kind != self.kind() {
-            Ok(folder.tcx().mk_const(kind, ty))
+            Ok(folder.interner().mk_const(kind, ty))
         } else {
             Ok(self)
         }
     }
 }
 
-impl<'tcx> TypeSuperVisitable<'tcx> for ty::Const<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Const<'tcx> {
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         self.ty().visit_with(visitor)?;
         self.kind().visit_with(visitor)
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for InferConst<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        _folder: &mut F,
+    ) -> Result<Self, F::Error> {
         Ok(self)
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for InferConst<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for InferConst<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        _visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         ControlFlow::Continue(())
     }
 }
 
-impl<'tcx> TypeSuperVisitable<'tcx> for ty::UnevaluatedConst<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::UnevaluatedConst<'tcx> {
+    fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(
+        &self,
+        visitor: &mut V,
+    ) -> ControlFlow<V::BreakTy> {
         self.substs.visit_with(visitor)
     }
 }
+
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for TyAndLayout<'tcx, Ty<'tcx>> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        visitor.visit_ty(self.ty)
+    }
+}
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 91a7d5d38..e6a73e8bb 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -8,7 +8,7 @@ use crate::ty::visit::ValidateBoundVars;
 use crate::ty::InferTy::*;
 use crate::ty::{
     self, AdtDef, DefIdTree, Discr, FallibleTypeFolder, Term, Ty, TyCtxt, TypeFlags, TypeFoldable,
-    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
 };
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
@@ -107,6 +107,15 @@ impl BoundRegionKind {
             _ => None,
         }
     }
+
+    pub fn expect_anon(&self) -> u32 {
+        match *self {
+            BoundRegionKind::BrNamed(_, _) | BoundRegionKind::BrEnv => {
+                bug!("expected anon region: {self:?}")
+            }
+            BoundRegionKind::BrAnon(idx, _) => idx,
+        }
+    }
 }
 
 pub trait Article {
@@ -250,7 +259,7 @@ impl<'tcx> ClosureSubsts<'tcx> {
         parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
     ) -> ClosureSubsts<'tcx> {
         ClosureSubsts {
-            substs: tcx.mk_substs(
+            substs: tcx.mk_substs_from_iter(
                 parts.parent_substs.iter().copied().chain(
                     [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
                         .iter()
@@ -377,7 +386,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
     ) -> GeneratorSubsts<'tcx> {
         GeneratorSubsts {
-            substs: tcx.mk_substs(
+            substs: tcx.mk_substs_from_iter(
                 parts.parent_substs.iter().copied().chain(
                     [
                         parts.resume_ty,
@@ -568,12 +577,12 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         self,
         def_id: DefId,
         tcx: TyCtxt<'tcx>,
-    ) -> impl Iterator<Item = impl Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
+    ) -> impl Iterator<Item: Iterator<Item = Ty<'tcx>> + Captures<'tcx>> {
         let layout = tcx.generator_layout(def_id).unwrap();
         layout.variant_fields.iter().map(move |variant| {
-            variant
-                .iter()
-                .map(move |field| ty::EarlyBinder(layout.field_tys[*field]).subst(tcx, self.substs))
+            variant.iter().map(move |field| {
+                ty::EarlyBinder(layout.field_tys[*field].ty).subst(tcx, self.substs)
+            })
         })
     }
 
@@ -655,7 +664,7 @@ impl<'tcx> InlineConstSubsts<'tcx> {
         parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>,
     ) -> InlineConstSubsts<'tcx> {
         InlineConstSubsts {
-            substs: tcx.mk_substs(
+            substs: tcx.mk_substs_from_iter(
                 parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())),
             ),
         }
@@ -853,7 +862,7 @@ impl<'tcx> TraitRef<'tcx> {
         substs: SubstsRef<'tcx>,
     ) -> ty::TraitRef<'tcx> {
         let defs = tcx.generics_of(trait_id);
-        tcx.mk_trait_ref(trait_id, tcx.intern_substs(&substs[..defs.params.len()]))
+        tcx.mk_trait_ref(trait_id, tcx.mk_substs(&substs[..defs.params.len()]))
     }
 }
 
@@ -899,7 +908,7 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
 
         ty::ExistentialTraitRef {
             def_id: trait_ref.def_id,
-            substs: tcx.intern_substs(&trait_ref.substs[1..]),
+            substs: tcx.mk_substs(&trait_ref.substs[1..]),
         }
     }
 
@@ -983,7 +992,7 @@ pub struct Binder<'tcx, T>(T, &'tcx List<BoundVariableKind>);
 
 impl<'tcx, T> Binder<'tcx, T>
 where
-    T: TypeVisitable<'tcx>,
+    T: TypeVisitable<TyCtxt<'tcx>>,
 {
     /// Wraps `value` in a binder, asserting that `value` does not
     /// contain any bound vars that would be bound by the
@@ -1051,14 +1060,14 @@ impl<'tcx, T> Binder<'tcx, T> {
         Binder(value, self.1)
     }
 
-    pub fn map_bound_ref<F, U: TypeVisitable<'tcx>>(&self, f: F) -> Binder<'tcx, U>
+    pub fn map_bound_ref<F, U: TypeVisitable<TyCtxt<'tcx>>>(&self, f: F) -> Binder<'tcx, U>
     where
         F: FnOnce(&T) -> U,
     {
         self.as_ref().map_bound(f)
     }
 
-    pub fn map_bound<F, U: TypeVisitable<'tcx>>(self, f: F) -> Binder<'tcx, U>
+    pub fn map_bound<F, U: TypeVisitable<TyCtxt<'tcx>>>(self, f: F) -> Binder<'tcx, U>
     where
         F: FnOnce(T) -> U,
     {
@@ -1070,7 +1079,10 @@ impl<'tcx, T> Binder<'tcx, T> {
         Binder(value, self.1)
     }
 
-    pub fn try_map_bound<F, U: TypeVisitable<'tcx>, E>(self, f: F) -> Result<Binder<'tcx, U>, E>
+    pub fn try_map_bound<F, U: TypeVisitable<TyCtxt<'tcx>>, E>(
+        self,
+        f: F,
+    ) -> Result<Binder<'tcx, U>, E>
     where
         F: FnOnce(T) -> Result<U, E>,
     {
@@ -1093,7 +1105,7 @@ impl<'tcx, T> Binder<'tcx, T> {
     /// in `bind`. This may be (debug) asserted in the future.
     pub fn rebind<U>(&self, value: U) -> Binder<'tcx, U>
     where
-        U: TypeVisitable<'tcx>,
+        U: TypeVisitable<TyCtxt<'tcx>>,
     {
         if cfg!(debug_assertions) {
             let mut validator = ValidateBoundVars::new(self.bound_vars());
@@ -1114,7 +1126,7 @@ impl<'tcx, T> Binder<'tcx, T> {
     /// would not be that useful.)
     pub fn no_bound_vars(self) -> Option<T>
     where
-        T: TypeVisitable<'tcx>,
+        T: TypeVisitable<TyCtxt<'tcx>>,
     {
         if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
     }
@@ -1153,16 +1165,16 @@ struct SkipBindersAt<'tcx> {
     index: ty::DebruijnIndex,
 }
 
-impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
+impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for SkipBindersAt<'tcx> {
     type Error = ();
 
-    fn tcx(&self) -> TyCtxt<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
     fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error>
     where
-        T: ty::TypeFoldable<'tcx>,
+        T: ty::TypeFoldable<TyCtxt<'tcx>>,
     {
         self.index.shift_in(1);
         let value = t.try_map_bound(|t| t.try_fold_with(self));
@@ -1177,7 +1189,7 @@ impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
             if index == self.index {
                 Err(())
             } else {
-                Ok(self.tcx().mk_ty(ty::Bound(index.shifted_out(1), bv)))
+                Ok(self.interner().mk_bound(index.shifted_out(1), bv))
             }
         } else {
             ty.try_super_fold_with(self)
@@ -1191,7 +1203,7 @@ impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
             if index == self.index {
                 Err(())
             } else {
-                Ok(self.tcx().mk_region(ty::ReLateBound(index.shifted_out(1), bv)))
+                Ok(self.interner().mk_re_late_bound(index.shifted_out(1), bv))
             }
         } else {
             r.try_super_fold_with(self)
@@ -1205,7 +1217,7 @@ impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
             if index == self.index {
                 Err(())
             } else {
-                Ok(self.tcx().mk_const(
+                Ok(self.interner().mk_const(
                     ty::ConstKind::Bound(index.shifted_out(1), bv),
                     ct.ty().try_fold_with(self)?,
                 ))
@@ -1266,7 +1278,7 @@ impl<'tcx> AliasTy<'tcx> {
     }
 
     pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
-        tcx.mk_ty(ty::Alias(self.kind(tcx), self))
+        tcx.mk_alias(self.kind(tcx), self)
     }
 }
 
@@ -1510,13 +1522,22 @@ pub struct BoundTy {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum BoundTyKind {
-    Anon,
-    Param(Symbol),
+    Anon(u32),
+    Param(DefId, Symbol),
+}
+
+impl BoundTyKind {
+    pub fn expect_anon(self) -> u32 {
+        match self {
+            BoundTyKind::Anon(i) => i,
+            _ => bug!(),
+        }
+    }
 }
 
 impl From<BoundVar> for BoundTy {
     fn from(var: BoundVar) -> Self {
-        BoundTy { var, kind: BoundTyKind::Anon }
+        BoundTy { var, kind: BoundTyKind::Anon(var.as_u32()) }
     }
 }
 
@@ -1539,7 +1560,7 @@ impl<'tcx> ExistentialProjection<'tcx> {
     pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
         let def_id = tcx.parent(self.def_id);
         let subst_count = tcx.generics_of(def_id).count() - 1;
-        let substs = tcx.intern_substs(&self.substs[..subst_count]);
+        let substs = tcx.mk_substs(&self.substs[..subst_count]);
         ty::ExistentialTraitRef { def_id, substs }
     }
 
@@ -1567,7 +1588,7 @@ impl<'tcx> ExistentialProjection<'tcx> {
 
         Self {
             def_id: projection_predicate.projection_ty.def_id,
-            substs: tcx.intern_substs(&projection_predicate.projection_ty.substs[1..]),
+            substs: tcx.mk_substs(&projection_predicate.projection_ty.substs[1..]),
             term: projection_predicate.term,
         }
     }
@@ -1620,10 +1641,16 @@ impl<'tcx> Region<'tcx> {
             ty::ReVar(..) => false,
             ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
             ty::ReErased => false,
+            ty::ReError(_) => false,
         }
     }
 
     #[inline]
+    pub fn is_error(self) -> bool {
+        matches!(*self, ty::ReError(_))
+    }
+
+    #[inline]
     pub fn is_static(self) -> bool {
         matches!(*self, ty::ReStatic)
     }
@@ -1683,6 +1710,7 @@ impl<'tcx> Region<'tcx> {
             ty::ReErased => {
                 flags = flags | TypeFlags::HAS_RE_ERASED;
             }
+            ty::ReError(_) => {}
         }
 
         debug!("type_flags({:?}) = {:?}", self, flags);
@@ -1733,6 +1761,13 @@ impl<'tcx> Region<'tcx> {
     pub fn is_var(self) -> bool {
         matches!(self.kind(), ty::ReVar(_))
     }
+
+    pub fn as_var(self) -> Option<RegionVid> {
+        match self.kind() {
+            ty::ReVar(vid) => Some(vid),
+            _ => None,
+        }
+    }
 }
 
 /// Type utilities
@@ -1867,7 +1902,7 @@ impl<'tcx> Ty<'tcx> {
                         // The way we evaluate the `N` in `[T; N]` here only works since we use
                         // `simd_size_and_type` post-monomorphization. It will probably start to ICE
                         // if we use it in generic code. See the `simd-array-trait` ui test.
-                        (f0_len.eval_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty)
+                        (f0_len.eval_target_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty)
                     }
                     // Otherwise, the fields of this Adt are the SIMD components (and we assume they
                     // all have the same type).
@@ -2028,7 +2063,7 @@ impl<'tcx> Ty<'tcx> {
     pub fn contains(self, other: Ty<'tcx>) -> bool {
         struct ContainsTyVisitor<'tcx>(Ty<'tcx>);
 
-        impl<'tcx> TypeVisitor<'tcx> for ContainsTyVisitor<'tcx> {
+        impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsTyVisitor<'tcx> {
             type BreakTy = ();
 
             fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
@@ -2040,6 +2075,28 @@ impl<'tcx> Ty<'tcx> {
         cf.is_break()
     }
 
+    /// Checks whether a type recursively contains any closure
+    ///
+    /// Example: `Option<[closure@file.rs:4:20]>` returns true
+    pub fn contains_closure(self) -> bool {
+        struct ContainsClosureVisitor;
+
+        impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsClosureVisitor {
+            type BreakTy = ();
+
+            fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
+                if let ty::Closure(_, _) = t.kind() {
+                    ControlFlow::Break(())
+                } else {
+                    t.super_visit_with(self)
+                }
+            }
+        }
+
+        let cf = self.visit_with(&mut ContainsClosureVisitor);
+        cf.is_break()
+    }
+
     /// Returns the type and mutability of `*ty`.
     ///
     /// The parameter `explicit` indicates if this is an *explicit* dereference.
@@ -2065,7 +2122,7 @@ impl<'tcx> Ty<'tcx> {
 
     pub fn fn_sig(self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
         match self.kind() {
-            FnDef(def_id, substs) => tcx.bound_fn_sig(*def_id).subst(tcx, substs),
+            FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
             FnPtr(f) => *f,
             Error(_) => {
                 // ignore errors (#54954)
@@ -2161,7 +2218,7 @@ impl<'tcx> Ty<'tcx> {
                 let assoc_items = tcx.associated_item_def_ids(
                     tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
                 );
-                tcx.mk_projection(assoc_items[0], tcx.intern_substs(&[self.into()]))
+                tcx.mk_projection(assoc_items[0], tcx.mk_substs(&[self.into()]))
             }
 
             ty::Bool
@@ -2181,6 +2238,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Dynamic(..)
             | ty::Closure(..)
             | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Never
             | ty::Tuple(_)
             | ty::Error(_)
@@ -2216,6 +2274,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Ref(..)
             | ty::Generator(..)
             | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Array(..)
             | ty::Closure(..)
             | ty::Never
@@ -2232,7 +2291,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Str | ty::Slice(_) => (tcx.types.usize, false),
             ty::Dynamic(..) => {
                 let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
-                (tcx.bound_type_of(dyn_metadata).subst(tcx, &[tail.into()]), false)
+                (tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()]), false)
             },
 
             // type parameters only have unit metadata if they're sized, so return true
@@ -2302,6 +2361,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Ref(..)
             | ty::Generator(..)
             | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Array(..)
             | ty::Closure(..)
             | ty::Never
@@ -2366,7 +2426,7 @@ impl<'tcx> Ty<'tcx> {
             // anything with custom metadata it might be more complicated.
             ty::Ref(_, _, hir::Mutability::Not) | ty::RawPtr(..) => false,
 
-            ty::Generator(..) | ty::GeneratorWitness(..) => false,
+            ty::Generator(..) | ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => false,
 
             // Might be, but not "trivial" so just giving the safe answer.
             ty::Adt(..) | ty::Closure(..) => false,
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index a07582fc8..b090bd9d8 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -3,7 +3,7 @@
 use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
 use crate::ty::sty::{ClosureSubsts, GeneratorSubsts, InlineConstSubsts};
-use crate::ty::visit::{TypeVisitable, TypeVisitor};
+use crate::ty::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor};
 use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
 
 use rustc_data_structures::intern::Interned;
@@ -71,7 +71,7 @@ impl<'tcx> List<Ty<'tcx>> {
     /// Allows to freely switch between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
     ///
     /// As lists are interned, `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>` have
-    /// be interned together, see `intern_type_list` for more details.
+    /// be interned together, see `mk_type_list` for more details.
     #[inline]
     pub fn as_substs(&'tcx self) -> SubstsRef<'tcx> {
         assert_eq!(TYPE_TAG, 0);
@@ -227,8 +227,11 @@ impl<'a, 'tcx> Lift<'tcx> for GenericArg<'a> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for GenericArg<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for GenericArg<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         match self.unpack() {
             GenericArgKind::Lifetime(lt) => lt.try_fold_with(folder).map(Into::into),
             GenericArgKind::Type(ty) => ty.try_fold_with(folder).map(Into::into),
@@ -237,8 +240,8 @@ impl<'tcx> TypeFoldable<'tcx> for GenericArg<'tcx> {
     }
 }
 
-impl<'tcx> TypeVisitable<'tcx> for GenericArg<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for GenericArg<'tcx> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         match self.unpack() {
             GenericArgKind::Lifetime(lt) => lt.visit_with(visitor),
             GenericArgKind::Type(ty) => ty.visit_with(visitor),
@@ -267,13 +270,11 @@ pub type SubstsRef<'tcx> = &'tcx InternalSubsts<'tcx>;
 impl<'tcx> InternalSubsts<'tcx> {
     /// Checks whether all elements of this list are types, if so, transmute.
     pub fn try_as_type_list(&'tcx self) -> Option<&'tcx List<Ty<'tcx>>> {
-        if self.iter().all(|arg| matches!(arg.unpack(), GenericArgKind::Type(_))) {
+        self.iter().all(|arg| matches!(arg.unpack(), GenericArgKind::Type(_))).then(|| {
             assert_eq!(TYPE_TAG, 0);
             // SAFETY: All elements are types, see `List<Ty<'tcx>>::as_substs`.
-            Some(unsafe { &*(self as *const List<GenericArg<'tcx>> as *const List<Ty<'tcx>>) })
-        } else {
-            None
-        }
+            unsafe { &*(self as *const List<GenericArg<'tcx>> as *const List<Ty<'tcx>>) }
+        })
     }
 
     /// Interpret these substitutions as the substitutions of a closure type.
@@ -318,7 +319,7 @@ impl<'tcx> InternalSubsts<'tcx> {
         let count = defs.count();
         let mut substs = SmallVec::with_capacity(count);
         Self::fill_item(&mut substs, tcx, defs, &mut mk_kind);
-        tcx.intern_substs(&substs)
+        tcx.mk_substs(&substs)
     }
 
     pub fn extend_to<F>(&self, tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> SubstsRef<'tcx>
@@ -467,26 +468,33 @@ impl<'tcx> InternalSubsts<'tcx> {
         target_substs: SubstsRef<'tcx>,
     ) -> SubstsRef<'tcx> {
         let defs = tcx.generics_of(source_ancestor);
-        tcx.mk_substs(target_substs.iter().chain(self.iter().skip(defs.params.len())))
+        tcx.mk_substs_from_iter(target_substs.iter().chain(self.iter().skip(defs.params.len())))
     }
 
     pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> SubstsRef<'tcx> {
-        tcx.mk_substs(self.iter().take(generics.count()))
+        tcx.mk_substs_from_iter(self.iter().take(generics.count()))
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for SubstsRef<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for SubstsRef<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         // This code is hot enough that it's worth specializing for the most
         // common length lists, to avoid the overhead of `SmallVec` creation.
         // The match arms are in order of frequency. The 1, 2, and 0 cases are
         // typically hit in 90--99.99% of cases. When folding doesn't change
         // the substs, it's faster to reuse the existing substs rather than
-        // calling `intern_substs`.
+        // calling `mk_substs`.
         match self.len() {
             1 => {
                 let param0 = self[0].try_fold_with(folder)?;
-                if param0 == self[0] { Ok(self) } else { Ok(folder.tcx().intern_substs(&[param0])) }
+                if param0 == self[0] {
+                    Ok(self)
+                } else {
+                    Ok(folder.interner().mk_substs(&[param0]))
+                }
             }
             2 => {
                 let param0 = self[0].try_fold_with(folder)?;
@@ -494,17 +502,20 @@ impl<'tcx> TypeFoldable<'tcx> for SubstsRef<'tcx> {
                 if param0 == self[0] && param1 == self[1] {
                     Ok(self)
                 } else {
-                    Ok(folder.tcx().intern_substs(&[param0, param1]))
+                    Ok(folder.interner().mk_substs(&[param0, param1]))
                 }
             }
             0 => Ok(self),
-            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.intern_substs(v)),
+            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_substs(v)),
         }
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<Ty<'tcx>> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
         // This code is fairly hot, though not as hot as `SubstsRef`.
         //
         // When compiling stage 2, I get the following results:
@@ -527,17 +538,17 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
                 if param0 == self[0] && param1 == self[1] {
                     Ok(self)
                 } else {
-                    Ok(folder.tcx().intern_type_list(&[param0, param1]))
+                    Ok(folder.interner().mk_type_list(&[param0, param1]))
                 }
             }
-            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.intern_type_list(v)),
+            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_type_list(v)),
         }
     }
 }
 
-impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &'tcx ty::List<T> {
+impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitable<TyCtxt<'tcx>> for &'tcx ty::List<T> {
     #[inline]
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         self.iter().try_for_each(|t| t.visit_with(visitor))
     }
 }
@@ -553,8 +564,8 @@ impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &'tcx ty::List<T> {
 pub struct EarlyBinder<T>(pub T);
 
 /// For early binders, you should first call `subst` before using any visitors.
-impl<'tcx, T> !TypeFoldable<'tcx> for ty::EarlyBinder<T> {}
-impl<'tcx, T> !TypeVisitable<'tcx> for ty::EarlyBinder<T> {}
+impl<'tcx, T> !TypeFoldable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
+impl<'tcx, T> !TypeVisitable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
 
 impl<T> EarlyBinder<T> {
     pub fn as_ref(&self) -> EarlyBinder<&T> {
@@ -615,7 +626,7 @@ impl<T, U> EarlyBinder<(T, U)> {
 
 impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
 where
-    I::Item: TypeFoldable<'tcx>,
+    I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     pub fn subst_iter(
         self,
@@ -634,7 +645,7 @@ pub struct SubstIter<'s, 'tcx, I: IntoIterator> {
 
 impl<'tcx, I: IntoIterator> Iterator for SubstIter<'_, 'tcx, I>
 where
-    I::Item: TypeFoldable<'tcx>,
+    I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     type Item = I::Item;
 
@@ -650,7 +661,7 @@ where
 impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIter<'_, 'tcx, I>
 where
     I::IntoIter: DoubleEndedIterator,
-    I::Item: TypeFoldable<'tcx>,
+    I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         Some(EarlyBinder(self.it.next_back()?).subst(self.tcx, self.substs))
@@ -660,14 +671,14 @@ where
 impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIter<'_, 'tcx, I>
 where
     I::IntoIter: ExactSizeIterator,
-    I::Item: TypeFoldable<'tcx>,
+    I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
 }
 
 impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
 where
     I::Item: Deref,
-    <I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
+    <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
     pub fn subst_iter_copied(
         self,
@@ -687,7 +698,7 @@ pub struct SubstIterCopied<'a, 'tcx, I: IntoIterator> {
 impl<'tcx, I: IntoIterator> Iterator for SubstIterCopied<'_, 'tcx, I>
 where
     I::Item: Deref,
-    <I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
+    <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
     type Item = <I::Item as Deref>::Target;
 
@@ -704,7 +715,7 @@ impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIterCopied<'_, 'tcx, I>
 where
     I::IntoIter: DoubleEndedIterator,
     I::Item: Deref,
-    <I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
+    <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         Some(EarlyBinder(*self.it.next_back()?).subst(self.tcx, self.substs))
@@ -715,7 +726,7 @@ impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIterCopied<'_, 'tcx, I>
 where
     I::IntoIter: ExactSizeIterator,
     I::Item: Deref,
-    <I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
+    <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
 }
 
@@ -741,7 +752,7 @@ impl<T: Iterator> Iterator for EarlyBinderIter<T> {
     }
 }
 
-impl<'tcx, T: TypeFoldable<'tcx>> ty::EarlyBinder<T> {
+impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> {
     pub fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> T {
         let mut folder = SubstFolder { tcx, substs, binders_passed: 0 };
         self.0.fold_with(&mut folder)
@@ -758,6 +769,11 @@ impl<'tcx, T: TypeFoldable<'tcx>> ty::EarlyBinder<T> {
     pub fn subst_identity(self) -> T {
         self.0
     }
+
+    /// Returns the inner value, but only if it contains no bound vars.
+    pub fn no_bound_vars(self) -> Option<T> {
+        if !self.0.needs_subst() { Some(self.0) } else { None }
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -771,13 +787,13 @@ struct SubstFolder<'a, 'tcx> {
     binders_passed: u32,
 }
 
-impl<'a, 'tcx> TypeFolder<'tcx> for SubstFolder<'a, 'tcx> {
+impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for SubstFolder<'a, 'tcx> {
     #[inline]
-    fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn fold_binder<T: TypeFoldable<'tcx>>(
+    fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>(
         &mut self,
         t: ty::Binder<'tcx, T>,
     ) -> ty::Binder<'tcx, T> {
@@ -970,7 +986,7 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
     /// As indicated in the diagram, here the same type `&'a i32` is substituted once, but in the
     /// first case we do not increase the De Bruijn index and in the second case we do. The reason
     /// is that only in the second case have we passed through a fn binder.
-    fn shift_vars_through_binders<T: TypeFoldable<'tcx>>(&self, val: T) -> T {
+    fn shift_vars_through_binders<T: TypeFoldable<TyCtxt<'tcx>>>(&self, val: T) -> T {
         debug!(
             "shift_vars(val={:?}, binders_passed={:?}, has_escaping_bound_vars={:?})",
             val,
@@ -982,7 +998,7 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
             return val;
         }
 
-        let result = ty::fold::shift_vars(TypeFolder::tcx(self), val, self.binders_passed);
+        let result = ty::fold::shift_vars(TypeFolder::interner(self), val, self.binders_passed);
         debug!("shift_vars: shifted result = {:?}", result);
 
         result
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index b38a5fbf2..233c0df2d 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -1,6 +1,6 @@
 use crate::traits::specialization_graph;
 use crate::ty::fast_reject::{self, SimplifiedType, TreatParams};
-use crate::ty::visit::TypeVisitable;
+use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{Ident, Ty, TyCtxt};
 use hir::def_id::LOCAL_CRATE;
 use rustc_hir as hir;
@@ -31,6 +31,15 @@ pub struct TraitDef {
     /// and thus `impl`s of it are allowed to overlap.
     pub is_marker: bool,
 
+    /// If `true`, then this trait has to `#[rustc_coinductive]` attribute or
+    /// is an auto trait. This indicates that trait solver cycles involving an
+    /// `X: ThisTrait` goal are accepted.
+    ///
+    /// In the future all traits should be coinductive, but we need a better
+    /// formal understanding of what exactly that means and should probably
+    /// also have already switched to the new trait solver.
+    pub is_coinductive: bool,
+
     /// If `true`, then this trait has the `#[rustc_skip_array_during_method_dispatch]`
     /// attribute, indicating that editions before 2021 should not consider this trait
     /// during method dispatch if the receiver is an array.
@@ -81,28 +90,6 @@ impl TraitImpls {
 }
 
 impl<'tcx> TraitDef {
-    pub fn new(
-        def_id: DefId,
-        unsafety: hir::Unsafety,
-        paren_sugar: bool,
-        has_auto_impl: bool,
-        is_marker: bool,
-        skip_array_during_method_dispatch: bool,
-        specialization_kind: TraitSpecializationKind,
-        must_implement_one_of: Option<Box<[Ident]>>,
-    ) -> TraitDef {
-        TraitDef {
-            def_id,
-            unsafety,
-            paren_sugar,
-            has_auto_impl,
-            is_marker,
-            skip_array_during_method_dispatch,
-            specialization_kind,
-            must_implement_one_of,
-        }
-    }
-
     pub fn ancestors(
         &self,
         tcx: TyCtxt<'tcx>,
@@ -238,7 +225,7 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
     for &impl_def_id in tcx.hir().trait_impls(trait_id) {
         let impl_def_id = impl_def_id.to_def_id();
 
-        let impl_self_ty = tcx.type_of(impl_def_id);
+        let impl_self_ty = tcx.type_of(impl_def_id).subst_identity();
         if impl_self_ty.references_error() {
             continue;
         }
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 2902c6dc5..586958247 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -1,6 +1,7 @@
 use crate::{
     hir::place::Place as HirPlace,
     infer::canonical::Canonical,
+    traits::ObligationCause,
     ty::{
         self, tls, BindingMode, BoundVar, CanonicalPolyFnSig, ClosureSizeProfileData,
         GenericArgKind, InternalSubsts, SubstsRef, Ty, UserSubsts,
@@ -193,6 +194,11 @@ pub struct TypeckResults<'tcx> {
     /// that are live across the yield of this generator (if a generator).
     pub generator_interior_types: ty::Binder<'tcx, Vec<GeneratorInteriorTypeCause<'tcx>>>,
 
+    /// Stores the predicates that apply on generator witness types.
+    /// formatting modified file tests/ui/generator/retain-resume-ref.rs
+    pub generator_interior_predicates:
+        FxHashMap<LocalDefId, Vec<(ty::Predicate<'tcx>, ObligationCause<'tcx>)>>,
+
     /// We sometimes treat byte string literals (which are of type `&[u8; N]`)
     /// as `&[u8]`, depending on the pattern in which they are used.
     /// This hashset records all instances where we behave
@@ -271,6 +277,7 @@ impl<'tcx> TypeckResults<'tcx> {
             closure_fake_reads: Default::default(),
             rvalue_scopes: Default::default(),
             generator_interior_types: ty::Binder::dummy(Default::default()),
+            generator_interior_predicates: Default::default(),
             treat_byte_string_as_slice: Default::default(),
             closure_size_eval: Default::default(),
         }
@@ -365,7 +372,7 @@ impl<'tcx> TypeckResults<'tcx> {
 
     pub fn node_type(&self, id: hir::HirId) -> Ty<'tcx> {
         self.node_type_opt(id).unwrap_or_else(|| {
-            bug!("node_type: no type for node `{}`", tls::with(|tcx| tcx.hir().node_to_string(id)))
+            bug!("node_type: no type for node {}", tls::with(|tcx| tcx.hir().node_to_string(id)))
         })
     }
 
@@ -544,9 +551,8 @@ fn validate_hir_id_for_typeck_results(hir_owner: OwnerId, hir_id: hir::HirId) {
 fn invalid_hir_id_for_typeck_results(hir_owner: OwnerId, hir_id: hir::HirId) {
     ty::tls::with(|tcx| {
         bug!(
-            "node {} with HirId::owner {:?} cannot be placed in TypeckResults with hir_owner {:?}",
+            "node {} cannot be placed in TypeckResults with hir_owner {:?}",
             tcx.hir().node_to_string(hir_id),
-            hir_id.owner,
             hir_owner
         )
     });
@@ -563,7 +569,7 @@ impl<'a, V> LocalTableInContext<'a, V> {
         self.data.contains_key(&id.local_id)
     }
 
-    pub fn get(&self, id: hir::HirId) -> Option<&V> {
+    pub fn get(&self, id: hir::HirId) -> Option<&'a V> {
         validate_hir_id_for_typeck_results(self.hir_owner, id);
         self.data.get(&id.local_id)
     }
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index d0d1dcc58..90270e0ee 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -3,10 +3,9 @@
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::mir;
 use crate::ty::layout::IntegerExt;
-use crate::ty::query::TyCtxtAt;
 use crate::ty::{
-    self, DefIdTree, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitable,
+    self, DefIdTree, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder,
+    TypeSuperFoldable, TypeVisitableExt,
 };
 use crate::ty::{GenericArgKind, SubstsRef};
 use rustc_apfloat::Float as _;
@@ -168,7 +167,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 | DefKind::Fn
                 | DefKind::AssocFn
                 | DefKind::AssocConst
-                | DefKind::Impl,
+                | DefKind::Impl { .. },
                 def_id,
             ) => Some(def_id),
             Res::Err => None,
@@ -363,7 +362,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let drop_trait = self.lang_items().drop_trait()?;
         self.ensure().coherent_trait(drop_trait);
 
-        let ty = self.type_of(adt_did);
+        let ty = self.type_of(adt_did).subst_identity();
         let (did, constness) = self.find_map_relevant_impl(drop_trait, ty, |impl_did| {
             if let Some(item_id) = self.associated_item_def_ids(impl_did).first() {
                 if validate(self, impl_did).is_ok() {
@@ -416,12 +415,12 @@ impl<'tcx> TyCtxt<'tcx> {
         // <P1, P2, P0>, and then look up which of the impl substs refer to
         // parameters marked as pure.
 
-        let impl_substs = match *self.type_of(impl_def_id).kind() {
+        let impl_substs = match *self.type_of(impl_def_id).subst_identity().kind() {
             ty::Adt(def_, substs) if def_ == def => substs,
             _ => bug!(),
         };
 
-        let item_substs = match *self.type_of(def.did()).kind() {
+        let item_substs = match *self.type_of(def.did()).subst_identity().kind() {
             ty::Adt(def_, substs) if def_ == def => substs,
             _ => bug!(),
         };
@@ -565,14 +564,14 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         closure_def_id: DefId,
         closure_substs: SubstsRef<'tcx>,
-        env_region: ty::RegionKind<'tcx>,
+        env_region: ty::Region<'tcx>,
     ) -> Option<Ty<'tcx>> {
         let closure_ty = self.mk_closure(closure_def_id, closure_substs);
         let closure_kind_ty = closure_substs.as_closure().kind_ty();
         let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
         let env_ty = match closure_kind {
-            ty::ClosureKind::Fn => self.mk_imm_ref(self.mk_region(env_region), closure_ty),
-            ty::ClosureKind::FnMut => self.mk_mut_ref(self.mk_region(env_region), closure_ty),
+            ty::ClosureKind::Fn => self.mk_imm_ref(env_region, closure_ty),
+            ty::ClosureKind::FnMut => self.mk_mut_ref(env_region, closure_ty),
             ty::ClosureKind::FnOnce => closure_ty,
         };
         Some(env_ty)
@@ -603,7 +602,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Get the type of the pointer to the static that we use in MIR.
     pub fn static_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
         // Make sure that any constants in the static's type are evaluated.
-        let static_ty = self.normalize_erasing_regions(ty::ParamEnv::empty(), self.type_of(def_id));
+        let static_ty = self.normalize_erasing_regions(
+            ty::ParamEnv::empty(),
+            self.type_of(def_id).subst_identity(),
+        );
 
         // Make sure that accesses to unsafe statics end up using raw pointers.
         // For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
@@ -616,6 +618,36 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    /// Return the set of types that should be taken into accound when checking
+    /// trait bounds on a generator's internal state.
+    pub fn generator_hidden_types(
+        self,
+        def_id: DefId,
+    ) -> impl Iterator<Item = ty::EarlyBinder<Ty<'tcx>>> {
+        let generator_layout = &self.mir_generator_witnesses(def_id);
+        generator_layout
+            .field_tys
+            .iter()
+            .filter(|decl| !decl.ignore_for_traits)
+            .map(|decl| ty::EarlyBinder(decl.ty))
+    }
+
+    /// Normalizes all opaque types in the given value, replacing them
+    /// with their underlying types.
+    pub fn expand_opaque_types(self, val: Ty<'tcx>) -> Ty<'tcx> {
+        let mut visitor = OpaqueTypeExpander {
+            seen_opaque_tys: FxHashSet::default(),
+            expanded_cache: FxHashMap::default(),
+            primary_def_id: None,
+            found_recursion: false,
+            found_any_recursion: false,
+            check_recursion: false,
+            expand_generators: false,
+            tcx: self,
+        };
+        val.fold_with(&mut visitor)
+    }
+
     /// Expands the given impl trait type, stopping if the type is recursive.
     #[instrument(skip(self), level = "debug", ret)]
     pub fn try_expand_impl_trait_type(
@@ -630,6 +662,7 @@ impl<'tcx> TyCtxt<'tcx> {
             found_recursion: false,
             found_any_recursion: false,
             check_recursion: true,
+            expand_generators: true,
             tcx: self,
         };
 
@@ -637,10 +670,6 @@ impl<'tcx> TyCtxt<'tcx> {
         if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
     }
 
-    pub fn bound_type_of(self, def_id: DefId) -> ty::EarlyBinder<Ty<'tcx>> {
-        ty::EarlyBinder(self.type_of(def_id))
-    }
-
     pub fn bound_return_position_impl_trait_in_trait_tys(
         self,
         def_id: DefId,
@@ -648,10 +677,6 @@ impl<'tcx> TyCtxt<'tcx> {
         ty::EarlyBinder(self.collect_return_position_impl_trait_in_trait_tys(def_id))
     }
 
-    pub fn bound_fn_sig(self, def_id: DefId) -> ty::EarlyBinder<ty::PolyFnSig<'tcx>> {
-        ty::EarlyBinder(self.fn_sig(def_id))
-    }
-
     pub fn bound_explicit_item_bounds(
         self,
         def_id: DefId,
@@ -736,11 +761,39 @@ impl<'tcx> TyCtxt<'tcx> {
         }
         (generator_layout, generator_saved_local_names)
     }
-}
 
-impl<'tcx> TyCtxtAt<'tcx> {
-    pub fn bound_type_of(self, def_id: DefId) -> ty::EarlyBinder<Ty<'tcx>> {
-        ty::EarlyBinder(self.type_of(def_id))
+    /// Query and get an English description for the item's kind.
+    pub fn def_descr(self, def_id: DefId) -> &'static str {
+        self.def_kind_descr(self.def_kind(def_id), def_id)
+    }
+
+    /// Get an English description for the item's kind.
+    pub fn def_kind_descr(self, def_kind: DefKind, def_id: DefId) -> &'static str {
+        match def_kind {
+            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "method",
+            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
+                rustc_hir::GeneratorKind::Async(..) => "async closure",
+                rustc_hir::GeneratorKind::Gen => "generator",
+            },
+            _ => def_kind.descr(def_id),
+        }
+    }
+
+    /// Gets an English article for the [`TyCtxt::def_descr`].
+    pub fn def_descr_article(self, def_id: DefId) -> &'static str {
+        self.def_kind_descr_article(self.def_kind(def_id), def_id)
+    }
+
+    /// Gets an English article for the [`TyCtxt::def_kind_descr`].
+    pub fn def_kind_descr_article(self, def_kind: DefKind, def_id: DefId) -> &'static str {
+        match def_kind {
+            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "a",
+            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
+                rustc_hir::GeneratorKind::Async(..) => "an",
+                rustc_hir::GeneratorKind::Gen => "a",
+            },
+            _ => def_kind.article(),
+        }
     }
 }
 
@@ -756,6 +809,7 @@ struct OpaqueTypeExpander<'tcx> {
     primary_def_id: Option<DefId>,
     found_recursion: bool,
     found_any_recursion: bool,
+    expand_generators: bool,
     /// Whether or not to check for recursive opaque types.
     /// This is `true` when we're explicitly checking for opaque type
     /// recursion, and 'false' otherwise to avoid unnecessary work.
@@ -773,7 +827,7 @@ impl<'tcx> OpaqueTypeExpander<'tcx> {
             let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
                 Some(expanded_ty) => *expanded_ty,
                 None => {
-                    let generic_ty = self.tcx.bound_type_of(def_id);
+                    let generic_ty = self.tcx.type_of(def_id);
                     let concrete_ty = generic_ty.subst(self.tcx, substs);
                     let expanded_ty = self.fold_ty(concrete_ty);
                     self.expanded_cache.insert((def_id, substs), expanded_ty);
@@ -792,20 +846,77 @@ impl<'tcx> OpaqueTypeExpander<'tcx> {
             None
         }
     }
+
+    fn expand_generator(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
+        if self.found_any_recursion {
+            return None;
+        }
+        let substs = substs.fold_with(self);
+        if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
+            let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
+                Some(expanded_ty) => *expanded_ty,
+                None => {
+                    for bty in self.tcx.generator_hidden_types(def_id) {
+                        let hidden_ty = bty.subst(self.tcx, substs);
+                        self.fold_ty(hidden_ty);
+                    }
+                    let expanded_ty = self.tcx.mk_generator_witness_mir(def_id, substs);
+                    self.expanded_cache.insert((def_id, substs), expanded_ty);
+                    expanded_ty
+                }
+            };
+            if self.check_recursion {
+                self.seen_opaque_tys.remove(&def_id);
+            }
+            Some(expanded_ty)
+        } else {
+            // If another opaque type that we contain is recursive, then it
+            // will report the error, so we don't have to.
+            self.found_any_recursion = true;
+            self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
+            None
+        }
+    }
 }
 
-impl<'tcx> TypeFolder<'tcx> for OpaqueTypeExpander<'tcx> {
-    fn tcx(&self) -> TyCtxt<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) = *t.kind() {
+        let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) = *t.kind() {
             self.expand_opaque_ty(def_id, substs).unwrap_or(t)
-        } else if t.has_opaque_types() {
+        } else if t.has_opaque_types() || t.has_generators() {
             t.super_fold_with(self)
         } else {
             t
+        };
+        if self.expand_generators {
+            if let ty::GeneratorWitnessMIR(def_id, substs) = *t.kind() {
+                t = self.expand_generator(def_id, substs).unwrap_or(t);
+            }
+        }
+        t
+    }
+
+    fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+        if let ty::PredicateKind::Clause(clause) = p.kind().skip_binder()
+            && let ty::Clause::Projection(projection_pred) = clause
+        {
+            p.kind()
+                .rebind(ty::ProjectionPredicate {
+                    projection_ty: projection_pred.projection_ty.fold_with(self),
+                    // Don't fold the term on the RHS of the projection predicate.
+                    // This is because for default trait methods with RPITITs, we
+                    // install a `NormalizesTo(Projection(RPITIT) -> Opaque(RPITIT))`
+                    // predicate, which would trivially cause a cycle when we do
+                    // anything that requires `ParamEnv::with_reveal_all_normalized`.
+                    term: projection_pred.term,
+                })
+                .to_predicate(self.tcx)
+        } else {
+            p.super_fold_with(self)
         }
     }
 }
@@ -911,6 +1022,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Foreign(_)
             | ty::Generator(..)
             | ty::GeneratorWitness(_)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Infer(_)
             | ty::Alias(..)
             | ty::Param(_)
@@ -950,6 +1062,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Foreign(_)
             | ty::Generator(..)
             | ty::GeneratorWitness(_)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Infer(_)
             | ty::Alias(..)
             | ty::Param(_)
@@ -1077,7 +1190,10 @@ impl<'tcx> Ty<'tcx> {
                 false
             }
 
-            ty::Foreign(_) | ty::GeneratorWitness(..) | ty::Error(_) => false,
+            ty::Foreign(_)
+            | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
+            | ty::Error(_) => false,
         }
     }
 
@@ -1173,6 +1289,7 @@ pub fn needs_drop_components<'tcx>(
         | ty::FnPtr(_)
         | ty::Char
         | ty::GeneratorWitness(..)
+        | ty::GeneratorWitnessMIR(..)
         | ty::RawPtr(_)
         | ty::Ref(..)
         | ty::Str => Ok(SmallVec::new()),
@@ -1243,7 +1360,11 @@ pub fn is_trivially_const_drop(ty: Ty<'_>) -> bool {
 
         // Not trivial because they have components, and instead of looking inside,
         // we'll just perform trait selection.
-        ty::Closure(..) | ty::Generator(..) | ty::GeneratorWitness(_) | ty::Adt(..) => false,
+        ty::Closure(..)
+        | ty::Generator(..)
+        | ty::GeneratorWitness(_)
+        | ty::GeneratorWitnessMIR(..)
+        | ty::Adt(..) => false,
 
         ty::Array(ty, _) | ty::Slice(ty) => is_trivially_const_drop(ty),
 
@@ -1262,8 +1383,8 @@ pub fn fold_list<'tcx, F, T>(
     intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
 ) -> Result<&'tcx ty::List<T>, F::Error>
 where
-    F: FallibleTypeFolder<'tcx>,
-    T: TypeFoldable<'tcx> + PartialEq + Copy,
+    F: FallibleTypeFolder<TyCtxt<'tcx>>,
+    T: TypeFoldable<TyCtxt<'tcx>> + PartialEq + Copy,
 {
     let mut iter = list.iter();
     // Look for the first element that changed
@@ -1279,7 +1400,7 @@ where
             for t in iter {
                 new_list.push(t.try_fold_with(folder)?)
             }
-            Ok(intern(folder.tcx(), &new_list))
+            Ok(intern(folder.interner(), &new_list))
         }
         Some((_, Err(err))) => {
             return Err(err);
@@ -1304,13 +1425,15 @@ pub fn reveal_opaque_types_in_bounds<'tcx>(
         found_recursion: false,
         found_any_recursion: false,
         check_recursion: false,
+        expand_generators: false,
         tcx,
     };
     val.fold_with(&mut visitor)
 }
 
 /// Determines whether an item is annotated with `doc(hidden)`.
-pub fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
+fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
+    assert!(def_id.is_local());
     tcx.get_attrs(def_id, sym::doc)
         .filter_map(|attr| attr.meta_item_list())
         .any(|items| items.iter().any(|item| item.has_name(sym::hidden)))
@@ -1325,7 +1448,7 @@ pub fn is_doc_notable_trait(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
 
 /// Determines whether an item is an intrinsic by Abi.
 pub fn is_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-    matches!(tcx.fn_sig(def_id).abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
+    matches!(tcx.fn_sig(def_id).skip_binder().abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
 }
 
 pub fn provide(providers: &mut ty::query::Providers) {
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index bee3cc4d7..6814cadb9 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -1,69 +1,13 @@
-//! A visiting traversal mechanism for complex data structures that contain type
-//! information.
-//!
-//! This is a read-only traversal of the data structure.
-//!
-//! This traversal has limited flexibility. Only a small number of "types of
-//! interest" within the complex data structures can receive custom
-//! visitation. These are the ones containing the most important type-related
-//! information, such as `Ty`, `Predicate`, `Region`, and `Const`.
-//!
-//! There are three groups of traits involved in each traversal.
-//! - `TypeVisitable`. This is implemented once for many types, including:
-//!   - Types of interest, for which the methods delegate to the visitor.
-//!   - All other types, including generic containers like `Vec` and `Option`.
-//!     It defines a "skeleton" of how they should be visited.
-//! - `TypeSuperVisitable`. This is implemented only for each type of interest,
-//!   and defines the visiting "skeleton" for these types.
-//! - `TypeVisitor`. This is implemented for each visitor. This defines how
-//!   types of interest are visited.
-//!
-//! This means each visit is a mixture of (a) generic visiting operations, and (b)
-//! custom visit operations that are specific to the visitor.
-//! - The `TypeVisitable` impls handle most of the traversal, and call into
-//!   `TypeVisitor` when they encounter a type of interest.
-//! - A `TypeVisitor` may call into another `TypeVisitable` impl, because some of
-//!   the types of interest are recursive and can contain other types of interest.
-//! - A `TypeVisitor` may also call into a `TypeSuperVisitable` impl, because each
-//!   visitor might provide custom handling only for some types of interest, or
-//!   only for some variants of each type of interest, and then use default
-//!   traversal for the remaining cases.
-//!
-//! For example, if you have `struct S(Ty, U)` where `S: TypeVisitable` and `U:
-//! TypeVisitable`, and an instance `s = S(ty, u)`, it would be visited like so:
-//! ```text
-//! s.visit_with(visitor) calls
-//! - ty.visit_with(visitor) calls
-//!   - visitor.visit_ty(ty) may call
-//!     - ty.super_visit_with(visitor)
-//! - u.visit_with(visitor)
-//! ```
 use crate::ty::{self, flags::FlagComputation, Binder, Ty, TyCtxt, TypeFlags};
 use rustc_errors::ErrorGuaranteed;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sso::SsoHashSet;
-use std::fmt;
 use std::ops::ControlFlow;
 
-/// This trait is implemented for every type that can be visited,
-/// providing the skeleton of the traversal.
-///
-/// To implement this conveniently, use the derive macro located in
-/// `rustc_macros`.
-pub trait TypeVisitable<'tcx>: fmt::Debug + Clone {
-    /// The entry point for visiting. To visit a value `t` with a visitor `v`
-    /// call: `t.visit_with(v)`.
-    ///
-    /// For most types, this just traverses the value, calling `visit_with` on
-    /// each field/element.
-    ///
-    /// For types of interest (such as `Ty`), the implementation of this method
-    /// that calls a visitor method specifically for that type (such as
-    /// `V::visit_ty`). This is where control transfers from `TypeFoldable` to
-    /// `TypeVisitor`.
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>;
+pub use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 
+pub trait TypeVisitableExt<'tcx>: TypeVisitable<TyCtxt<'tcx>> {
     /// Returns `true` if `self` has any late-bound regions that are either
     /// bound by `binder` or bound by some binder outside of `binder`.
     /// If `binder` is `ty::INNERMOST`, this indicates whether
@@ -100,6 +44,9 @@ pub trait TypeVisitable<'tcx>: fmt::Debug + Clone {
     fn has_opaque_types(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_OPAQUE)
     }
+    fn has_generators(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_TY_GENERATOR)
+    }
     fn references_error(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_ERROR)
     }
@@ -182,45 +129,7 @@ pub trait TypeVisitable<'tcx>: fmt::Debug + Clone {
     }
 }
 
-pub trait TypeSuperVisitable<'tcx>: TypeVisitable<'tcx> {
-    /// Provides a default visit for a type of interest. This should only be
-    /// called within `TypeVisitor` methods, when a non-custom traversal is
-    /// desired for the value of the type of interest passed to that method.
-    /// For example, in `MyVisitor::visit_ty(ty)`, it is valid to call
-    /// `ty.super_visit_with(self)`, but any other visiting should be done
-    /// with `xyz.visit_with(self)`.
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>;
-}
-
-/// This trait is implemented for every visiting traversal. There is a visit
-/// method defined for every type of interest. Each such method has a default
-/// that recurses into the type's fields in a non-custom fashion.
-pub trait TypeVisitor<'tcx>: Sized {
-    type BreakTy = !;
-
-    fn visit_binder<T: TypeVisitable<'tcx>>(
-        &mut self,
-        t: &Binder<'tcx, T>,
-    ) -> ControlFlow<Self::BreakTy> {
-        t.super_visit_with(self)
-    }
-
-    fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-        t.super_visit_with(self)
-    }
-
-    fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
-        r.super_visit_with(self)
-    }
-
-    fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
-        c.super_visit_with(self)
-    }
-
-    fn visit_predicate(&mut self, p: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
-        p.super_visit_with(self)
-    }
-}
+impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitableExt<'tcx> for T {}
 
 ///////////////////////////////////////////////////////////////////////////
 // Region folder
@@ -229,7 +138,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Invoke `callback` on every region appearing free in `value`.
     pub fn for_each_free_region(
         self,
-        value: &impl TypeVisitable<'tcx>,
+        value: &impl TypeVisitable<TyCtxt<'tcx>>,
         mut callback: impl FnMut(ty::Region<'tcx>),
     ) {
         self.any_free_region_meets(value, |r| {
@@ -241,7 +150,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Returns `true` if `callback` returns true for every region appearing free in `value`.
     pub fn all_free_regions_meet(
         self,
-        value: &impl TypeVisitable<'tcx>,
+        value: &impl TypeVisitable<TyCtxt<'tcx>>,
         mut callback: impl FnMut(ty::Region<'tcx>) -> bool,
     ) -> bool {
         !self.any_free_region_meets(value, |r| !callback(r))
@@ -250,7 +159,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Returns `true` if `callback` returns true for some region appearing free in `value`.
     pub fn any_free_region_meets(
         self,
-        value: &impl TypeVisitable<'tcx>,
+        value: &impl TypeVisitable<TyCtxt<'tcx>>,
         callback: impl FnMut(ty::Region<'tcx>) -> bool,
     ) -> bool {
         struct RegionVisitor<F> {
@@ -275,13 +184,13 @@ impl<'tcx> TyCtxt<'tcx> {
             callback: F,
         }
 
-        impl<'tcx, F> TypeVisitor<'tcx> for RegionVisitor<F>
+        impl<'tcx, F> TypeVisitor<TyCtxt<'tcx>> for RegionVisitor<F>
         where
             F: FnMut(ty::Region<'tcx>) -> bool,
         {
             type BreakTy = ();
 
-            fn visit_binder<T: TypeVisitable<'tcx>>(
+            fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
                 &mut self,
                 t: &Binder<'tcx, T>,
             ) -> ControlFlow<Self::BreakTy> {
@@ -328,7 +237,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: &Binder<'tcx, T>,
     ) -> FxHashSet<ty::BoundRegionKind>
     where
-        T: TypeVisitable<'tcx>,
+        T: TypeVisitable<TyCtxt<'tcx>>,
     {
         self.collect_late_bound_regions(value, true)
     }
@@ -339,7 +248,7 @@ impl<'tcx> TyCtxt<'tcx> {
         value: &Binder<'tcx, T>,
     ) -> FxHashSet<ty::BoundRegionKind>
     where
-        T: TypeVisitable<'tcx>,
+        T: TypeVisitable<TyCtxt<'tcx>>,
     {
         self.collect_late_bound_regions(value, false)
     }
@@ -350,7 +259,7 @@ impl<'tcx> TyCtxt<'tcx> {
         just_constraint: bool,
     ) -> FxHashSet<ty::BoundRegionKind>
     where
-        T: TypeVisitable<'tcx>,
+        T: TypeVisitable<TyCtxt<'tcx>>,
     {
         let mut collector = LateBoundRegionsCollector::new(just_constraint);
         let result = value.as_ref().skip_binder().visit_with(&mut collector);
@@ -377,10 +286,10 @@ impl<'tcx> ValidateBoundVars<'tcx> {
     }
 }
 
-impl<'tcx> TypeVisitor<'tcx> for ValidateBoundVars<'tcx> {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ValidateBoundVars<'tcx> {
     type BreakTy = ();
 
-    fn visit_binder<T: TypeVisitable<'tcx>>(
+    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
         &mut self,
         t: &Binder<'tcx, T>,
     ) -> ControlFlow<Self::BreakTy> {
@@ -489,10 +398,10 @@ struct HasEscapingVarsVisitor {
     outer_index: ty::DebruijnIndex,
 }
 
-impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for HasEscapingVarsVisitor {
     type BreakTy = FoundEscapingVars;
 
-    fn visit_binder<T: TypeVisitable<'tcx>>(
+    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
         &mut self,
         t: &Binder<'tcx, T>,
     ) -> ControlFlow<Self::BreakTy> {
@@ -566,7 +475,7 @@ impl std::fmt::Debug for HasTypeFlagsVisitor {
     }
 }
 
-impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for HasTypeFlagsVisitor {
     type BreakTy = FoundFlags;
 
     #[inline]
@@ -636,8 +545,8 @@ impl LateBoundRegionsCollector {
     }
 }
 
-impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector {
-    fn visit_binder<T: TypeVisitable<'tcx>>(
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for LateBoundRegionsCollector {
+    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
         &mut self,
         t: &Binder<'tcx, T>,
     ) -> ControlFlow<Self::BreakTy> {
@@ -698,7 +607,7 @@ impl MaxUniverse {
     }
 }
 
-impl<'tcx> TypeVisitor<'tcx> for MaxUniverse {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         if let ty::Placeholder(placeholder) = t.kind() {
             self.max_universe = ty::UniverseIndex::from_u32(
diff --git a/compiler/rustc_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs
index f77bd9f0c..b9b1cd73a 100644
--- a/compiler/rustc_middle/src/ty/vtable.rs
+++ b/compiler/rustc_middle/src/ty/vtable.rs
@@ -112,5 +112,5 @@ pub(super) fn vtable_allocation_provider<'tcx>(
     }
 
     vtable.mutability = Mutability::Not;
-    tcx.create_memory_alloc(tcx.intern_const_alloc(vtable))
+    tcx.create_memory_alloc(tcx.mk_const_alloc(vtable))
 }
diff --git a/compiler/rustc_middle/src/ty/walk.rs b/compiler/rustc_middle/src/ty/walk.rs
index 708a5e4d0..182945b9c 100644
--- a/compiler/rustc_middle/src/ty/walk.rs
+++ b/compiler/rustc_middle/src/ty/walk.rs
@@ -190,6 +190,7 @@ fn push_inner<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent: GenericArg<'tcx>)
             ty::Adt(_, substs)
             | ty::Closure(_, substs)
             | ty::Generator(_, substs, _)
+            | ty::GeneratorWitnessMIR(_, substs)
             | ty::FnDef(_, substs) => {
                 stack.extend(substs.iter().rev());
             }
diff --git a/compiler/rustc_middle/src/values.rs b/compiler/rustc_middle/src/values.rs
index 34e8a5597..c4f526dbd 100644
--- a/compiler/rustc_middle/src/values.rs
+++ b/compiler/rustc_middle/src/values.rs
@@ -2,7 +2,7 @@ use crate::dep_graph::DepKind;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
 use rustc_hir as hir;
-use rustc_hir::def::DefKind;
+use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::Representability;
 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
 use rustc_query_system::query::QueryInfo;
@@ -16,7 +16,7 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for Ty<'_> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, _: &[QueryInfo<DepKind>]) -> Self {
         // SAFETY: This is never called when `Self` is not `Ty<'tcx>`.
         // FIXME: Represent the above fact in the trait system somehow.
-        unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error()) }
+        unsafe { std::mem::transmute::<Ty<'tcx>, Ty<'_>>(tcx.ty_error_misc()) }
     }
 }
 
@@ -34,7 +34,7 @@ impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::SymbolName<'_> {
 
 impl<'tcx> Value<TyCtxt<'tcx>, DepKind> for ty::Binder<'_, ty::FnSig<'_>> {
     fn from_cycle_error(tcx: TyCtxt<'tcx>, stack: &[QueryInfo<DepKind>]) -> Self {
-        let err = tcx.ty_error();
+        let err = tcx.ty_error_misc();
 
         let arity = if let Some(frame) = stack.get(0)
             && frame.query.dep_kind == DepKind::fn_sig
@@ -199,7 +199,8 @@ fn find_item_ty_spans(
 ) {
     match ty.kind {
         hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
-            if let Some(def_id) = path.res.opt_def_id() {
+            if let Res::Def(kind, def_id) = path.res
+                && kind != DefKind::TyAlias {
                 let check_params = def_id.as_local().map_or(true, |def_id| {
                     if def_id == needle {
                         spans.push(ty.span);