Merging upstream version 1.70.0+dfsg1.

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

75 files changed, 2554 insertions, 1355 deletions

diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index a2b78cc29..5b2ec9029 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -26,8 +26,8 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_query_system = { path = "../rustc_query_system" }
-rustc-rayon-core = { version = "0.4.0", optional = true }
-rustc-rayon = { version = "0.4.0", optional = true }
+rustc-rayon-core = { version = "0.5.0", optional = true }
+rustc-rayon = { version = "0.5.0", optional = true }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_middle/locales/en-US.ftl b/compiler/rustc_middle/messages.ftl
index 4f4e5c6a2..bd9d89dee 100644
--- a/compiler/rustc_middle/locales/en-US.ftl
+++ b/compiler/rustc_middle/messages.ftl
@@ -16,6 +16,10 @@ middle_limit_invalid =
     `limit` must be a non-negative integer
     .label = {$error_str}
 
+middle_recursion_limit_reached =
+    reached the recursion limit finding the struct tail for `{$ty}`
+    .help = consider increasing the recursion limit by adding a `#![recursion_limit = "{$suggested_limit}"]`
+
 middle_const_eval_non_int =
     constant evaluation of enum discriminant resulted in non-integer
 
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index 62e44b629..dd1e254f4 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -36,7 +36,7 @@ macro_rules! arena_types {
             )>,
             [] 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>,
+            [] crate_for_resolver: rustc_data_structures::steal::Steal<(rustc_ast::Crate, rustc_ast::AttrVec)>,
             [] resolutions: rustc_middle::ty::ResolverGlobalCtxt,
             [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult,
             [decode] code_region: rustc_middle::mir::coverage::CodeRegion,
@@ -94,7 +94,8 @@ macro_rules! arena_types {
             [] object_safety_violations: rustc_middle::traits::ObjectSafetyViolation,
             [] codegen_unit: rustc_middle::mir::mono::CodegenUnit<'tcx>,
             [decode] attribute: rustc_ast::Attribute,
-            [] name_set: rustc_data_structures::fx::FxHashSet<rustc_span::symbol::Symbol>,
+            [] name_set: rustc_data_structures::unord::UnordSet<rustc_span::symbol::Symbol>,
+            [] ordered_name_set: rustc_data_structures::fx::FxIndexSet<rustc_span::symbol::Symbol>,
             [] hir_id_set: rustc_hir::HirIdSet,
 
             // Interned types
@@ -107,6 +108,7 @@ 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] registered_tools: rustc_middle::ty::RegisteredTools,
             [decode] is_late_bound_map: rustc_data_structures::fx::FxIndexSet<rustc_hir::ItemLocalId>,
             [decode] impl_source: rustc_middle::traits::ImplSource<'tcx, ()>,
 
@@ -117,6 +119,7 @@ macro_rules! arena_types {
             [] 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>),
+            [] mod_child: rustc_middle::metadata::ModChild,
         ]);
     )
 }
diff --git a/compiler/rustc_middle/src/dep_graph/mod.rs b/compiler/rustc_middle/src/dep_graph/mod.rs
index 84510fe21..0ddbe7d1c 100644
--- a/compiler/rustc_middle/src/dep_graph/mod.rs
+++ b/compiler/rustc_middle/src/dep_graph/mod.rs
@@ -94,7 +94,7 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
     }
 
     #[inline]
-    fn dep_kind_info(&self, dep_kind: DepKind) -> &DepKindStruct<'tcx> {
-        &self.query_kinds[dep_kind as usize]
+    fn dep_kind_info(&self, dk: DepKind) -> &DepKindStruct<'tcx> {
+        &self.query_kinds[dk as usize]
     }
 }
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index 5e94da8cb..dc4aa1864 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -50,6 +50,14 @@ pub struct LimitInvalid<'a> {
 }
 
 #[derive(Diagnostic)]
+#[diag(middle_recursion_limit_reached)]
+#[help]
+pub struct RecursionLimitReached<'tcx> {
+    pub ty: Ty<'tcx>,
+    pub suggested_limit: rustc_session::Limit,
+}
+
+#[derive(Diagnostic)]
 #[diag(middle_const_eval_non_int)]
 pub struct ConstEvalNonIntError {
     #[primary_span]
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 4b5bacac8..e551c76f8 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -1,13 +1,14 @@
 use crate::hir::{ModuleItems, Owner};
-use crate::ty::{DefIdTree, TyCtxt};
+use crate::query::LocalCrate;
+use crate::ty::TyCtxt;
 use rustc_ast as ast;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
-use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_hir::definitions::{DefKey, DefPath, DefPathData, DefPathHash};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::*;
 use rustc_index::vec::Idx;
@@ -73,18 +74,17 @@ impl<'hir> Iterator for ParentHirIterator<'hir> {
         if self.current_id == CRATE_HIR_ID {
             return None;
         }
-        loop {
-            // There are nodes that do not have entries, so we need to skip them.
-            let parent_id = self.map.parent_id(self.current_id);
 
-            if parent_id == self.current_id {
-                self.current_id = CRATE_HIR_ID;
-                return None;
-            }
+        // There are nodes that do not have entries, so we need to skip them.
+        let parent_id = self.map.parent_id(self.current_id);
 
-            self.current_id = parent_id;
-            return Some(parent_id);
+        if parent_id == self.current_id {
+            self.current_id = CRATE_HIR_ID;
+            return None;
         }
+
+        self.current_id = parent_id;
+        return Some(parent_id);
     }
 }
 
@@ -179,7 +179,19 @@ impl<'hir> Map<'hir> {
     /// Do not call this function directly. The query should be called.
     pub(super) fn opt_def_kind(self, local_def_id: LocalDefId) -> Option<DefKind> {
         let hir_id = self.local_def_id_to_hir_id(local_def_id);
-        let def_kind = match self.find(hir_id)? {
+        let node = match self.find(hir_id) {
+            Some(node) => node,
+            None => match self.def_key(local_def_id).disambiguated_data.data {
+                // FIXME: Some anonymous constants do not have corresponding HIR nodes,
+                // so many local queries will panic on their def ids. `None` is currently
+                // returned here instead of `DefKind::{Anon,Inline}Const` to avoid such panics.
+                // Ideally all def ids should have `DefKind`s, we need to create the missing
+                // HIR nodes or feed relevant query results to achieve that.
+                DefPathData::AnonConst => return None,
+                _ => bug!("no HIR node for def id {local_def_id:?}"),
+            },
+        };
+        let def_kind = match node {
             Node::Item(item) => match item.kind {
                 ItemKind::Static(_, mt, _) => DefKind::Static(mt),
                 ItemKind::Const(..) => DefKind::Const,
@@ -187,7 +199,7 @@ impl<'hir> Map<'hir> {
                 ItemKind::Macro(_, macro_kind) => DefKind::Macro(macro_kind),
                 ItemKind::Mod(..) => DefKind::Mod,
                 ItemKind::OpaqueTy(ref opaque) => {
-                    if opaque.in_trait {
+                    if opaque.in_trait && !self.tcx.lower_impl_trait_in_trait_to_assoc_ty() {
                         DefKind::ImplTraitPlaceholder
                     } else {
                         DefKind::OpaqueTy
@@ -266,7 +278,10 @@ impl<'hir> Map<'hir> {
             | Node::Param(_)
             | Node::Arm(_)
             | Node::Lifetime(_)
-            | Node::Block(_) => return None,
+            | Node::Block(_) => span_bug!(
+                self.span(hir_id),
+                "unexpected node with def id {local_def_id:?}: {node:?}"
+            ),
         };
         Some(def_kind)
     }
@@ -316,7 +331,7 @@ impl<'hir> Map<'hir> {
     /// Retrieves the `Node` corresponding to `id`, returning `None` if cannot be found.
     #[inline]
     pub fn find_by_def_id(self, id: LocalDefId) -> Option<Node<'hir>> {
-        self.find(self.local_def_id_to_hir_id(id))
+        self.find(self.tcx.opt_local_def_id_to_hir_id(id)?)
     }
 
     /// Retrieves the `Node` corresponding to `id`, panicking if it cannot be found.
@@ -333,7 +348,7 @@ impl<'hir> Map<'hir> {
     }
 
     pub fn get_if_local(self, id: DefId) -> Option<Node<'hir>> {
-        id.as_local().and_then(|id| self.find(self.local_def_id_to_hir_id(id)))
+        id.as_local().and_then(|id| self.find(self.tcx.opt_local_def_id_to_hir_id(id)?))
     }
 
     pub fn get_generics(self, id: LocalDefId) -> Option<&'hir Generics<'hir>> {
@@ -1131,10 +1146,9 @@ impl<'hir> intravisit::Map<'hir> for Map<'hir> {
     }
 }
 
-pub(super) fn crate_hash(tcx: TyCtxt<'_>, crate_num: CrateNum) -> Svh {
-    debug_assert_eq!(crate_num, LOCAL_CRATE);
+pub(super) fn crate_hash(tcx: TyCtxt<'_>, _: LocalCrate) -> Svh {
     let krate = tcx.hir_crate(());
-    let hir_body_hash = krate.hir_hash;
+    let hir_body_hash = krate.opt_hir_hash.expect("HIR hash missing while computing crate hash");
 
     let upstream_crates = upstream_crates(tcx);
 
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index c9da711e5..7770a5e47 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -7,8 +7,7 @@ pub mod nested_filter;
 pub mod place;
 
 use crate::ty::query::Providers;
-use crate::ty::{DefIdTree, ImplSubject, TyCtxt};
-use rustc_data_structures::fingerprint::Fingerprint;
+use crate::ty::{EarlyBinder, ImplSubject, TyCtxt};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -24,14 +23,15 @@ use rustc_span::{ExpnId, DUMMY_SP};
 #[derive(Copy, Clone, Debug)]
 pub struct Owner<'tcx> {
     node: OwnerNode<'tcx>,
-    hash_without_bodies: Fingerprint,
 }
 
 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Owner<'tcx> {
     #[inline]
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        let Owner { node: _, hash_without_bodies } = self;
-        hash_without_bodies.hash_stable(hcx, hasher)
+        // Perform a shallow hash instead using the deep hash saved in `OwnerNodes`. This lets us
+        // differentiate queries that depend on the full HIR tree from those that only depend on
+        // the item signature.
+        hcx.without_hir_bodies(|hcx| self.node.hash_stable(hcx, hasher));
     }
 }
 
@@ -104,11 +104,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.parent_module_from_def_id(id.owner.def_id)
     }
 
-    pub fn impl_subject(self, def_id: DefId) -> ImplSubject<'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).subst_identity()))
+    pub fn impl_subject(self, def_id: DefId) -> EarlyBinder<ImplSubject<'tcx>> {
+        match self.impl_trait_ref(def_id) {
+            Some(t) => t.map_bound(ImplSubject::Trait),
+            None => self.type_of(def_id).map_bound(ImplSubject::Inherent),
+        }
     }
 }
 
@@ -123,7 +123,7 @@ pub fn provide(providers: &mut Providers) {
     providers.hir_owner = |tcx, id| {
         let owner = tcx.hir_crate(()).owners.get(id.def_id)?.as_owner()?;
         let node = owner.node();
-        Some(Owner { node, hash_without_bodies: owner.nodes.hash_without_bodies })
+        Some(Owner { node })
     };
     providers.opt_local_def_id_to_hir_id = |tcx, id| {
         let owner = tcx.hir_crate(()).owners[id].map(|_| ());
@@ -147,18 +147,18 @@ pub fn provide(providers: &mut Providers) {
         tcx.hir_crate(()).owners[id.def_id].as_owner().map_or(AttributeMap::EMPTY, |o| &o.attrs)
     };
     providers.def_span = |tcx, def_id| {
-        let def_id = def_id.expect_local();
+        let def_id = def_id;
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         tcx.hir().opt_span(hir_id).unwrap_or(DUMMY_SP)
     };
     providers.def_ident_span = |tcx, def_id| {
-        let def_id = def_id.expect_local();
+        let def_id = def_id;
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         tcx.hir().opt_ident_span(hir_id)
     };
     providers.fn_arg_names = |tcx, id| {
         let hir = tcx.hir();
-        let def_id = id.expect_local();
+        let def_id = id;
         let hir_id = hir.local_def_id_to_hir_id(def_id);
         if let Some(body_id) = hir.maybe_body_owned_by(def_id) {
             tcx.arena.alloc_from_iter(hir.body_param_names(body_id))
@@ -176,13 +176,10 @@ pub fn provide(providers: &mut Providers) {
             span_bug!(hir.span(hir_id), "fn_arg_names: unexpected item {:?}", id);
         }
     };
-    providers.opt_def_kind = |tcx, def_id| tcx.hir().opt_def_kind(def_id.expect_local());
-    providers.opt_rpitit_info = |_, _| None;
+    providers.opt_def_kind = |tcx, def_id| tcx.hir().opt_def_kind(def_id);
     providers.all_local_trait_impls = |tcx, ()| &tcx.resolutions(()).trait_impls;
-    providers.expn_that_defined = |tcx, id| {
-        let id = id.expect_local();
-        tcx.resolutions(()).expn_that_defined.get(&id).copied().unwrap_or(ExpnId::root())
-    };
+    providers.expn_that_defined =
+        |tcx, id| tcx.resolutions(()).expn_that_defined.get(&id).copied().unwrap_or(ExpnId::root());
     providers.in_scope_traits_map = |tcx, id| {
         tcx.hir_crate(()).owners[id.def_id].as_owner().map(|owner_info| &owner_info.trait_map)
     };
diff --git a/compiler/rustc_middle/src/hir/place.rs b/compiler/rustc_middle/src/hir/place.rs
index 83d3b0100..80b4c964c 100644
--- a/compiler/rustc_middle/src/hir/place.rs
+++ b/compiler/rustc_middle/src/hir/place.rs
@@ -2,7 +2,7 @@ use crate::ty;
 use crate::ty::Ty;
 
 use rustc_hir::HirId;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
 #[derive(TypeFoldable, TypeVisitable)]
@@ -27,7 +27,7 @@ pub enum ProjectionKind {
     /// the field. The field is identified by which variant
     /// it appears in along with a field index. The variant
     /// is used for enums.
-    Field(u32, VariantIdx),
+    Field(FieldIdx, VariantIdx),
 
     /// Some index like `B[x]`, where `B` is the base
     /// expression. We don't preserve the index `x` because
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 7f8fc1774..b5b712c36 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -35,9 +35,9 @@ use std::ops::Index;
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct Canonical<'tcx, V> {
+    pub value: V,
     pub max_universe: ty::UniverseIndex,
     pub variables: CanonicalVarInfos<'tcx>,
-    pub value: V,
 }
 
 pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo<'tcx>>;
@@ -80,6 +80,18 @@ impl CanonicalVarValues<'_> {
             }
         })
     }
+
+    pub fn is_identity_modulo_regions(&self) -> bool {
+        self.var_values.iter().enumerate().all(|(bv, arg)| match arg.unpack() {
+            ty::GenericArgKind::Lifetime(_) => true,
+            ty::GenericArgKind::Type(ty) => {
+                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.as_usize() == bv)
+            }
+        })
+    }
 }
 
 /// When we canonicalize a value to form a query, we wind up replacing
@@ -149,15 +161,15 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
         }
     }
 
-    pub fn expect_anon_placeholder(self) -> u32 {
+    pub fn expect_placeholder_index(self) -> usize {
         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(),
+            CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.bound.var.as_usize(),
+            CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.bound.var.as_usize(),
+            CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.bound.as_usize(),
         }
     }
 }
@@ -411,7 +423,7 @@ impl<'tcx> CanonicalVarValues<'tcx> {
                         CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
                             let br = ty::BoundRegion {
                                 var: ty::BoundVar::from_usize(i),
-                                kind: ty::BrAnon(i as u32, None),
+                                kind: ty::BrAnon(None),
                             };
                             tcx.mk_re_late_bound(ty::INNERMOST, br).into()
                         }
diff --git a/compiler/rustc_middle/src/infer/unify_key.rs b/compiler/rustc_middle/src/infer/unify_key.rs
index 41d8c7ffd..a873854f0 100644
--- a/compiler/rustc_middle/src/infer/unify_key.rs
+++ b/compiler/rustc_middle/src/infer/unify_key.rs
@@ -1,4 +1,4 @@
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{self, Region, Ty, TyCtxt};
 use rustc_data_structures::unify::{NoError, UnifyKey, UnifyValue};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::Symbol;
@@ -11,7 +11,20 @@ pub trait ToType {
 }
 
 #[derive(PartialEq, Copy, Clone, Debug)]
-pub struct UnifiedRegion<'tcx>(pub Option<ty::Region<'tcx>>);
+pub struct UnifiedRegion<'tcx> {
+    value: Option<ty::Region<'tcx>>,
+}
+
+impl<'tcx> UnifiedRegion<'tcx> {
+    pub fn new(value: Option<Region<'tcx>>) -> Self {
+        Self { value }
+    }
+
+    /// The caller is responsible for checking universe compatibility before using this value.
+    pub fn get_value_ignoring_universes(self) -> Option<Region<'tcx>> {
+        self.value
+    }
+}
 
 #[derive(PartialEq, Copy, Clone, Debug)]
 pub struct RegionVidKey<'tcx> {
@@ -44,11 +57,27 @@ impl<'tcx> UnifyValue for UnifiedRegion<'tcx> {
     type Error = NoError;
 
     fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
-        Ok(match (value1.0, value2.0) {
+        // We pick the value of the least universe because it is compatible with more variables.
+        // This is *not* necessary for soundness, but it allows more region variables to be
+        // resolved to the said value.
+        #[cold]
+        fn min_universe<'tcx>(r1: Region<'tcx>, r2: Region<'tcx>) -> Region<'tcx> {
+            cmp::min_by_key(r1, r2, |r| match r.kind() {
+                ty::ReStatic
+                | ty::ReErased
+                | ty::ReFree(..)
+                | ty::ReEarlyBound(..)
+                | ty::ReError(_) => ty::UniverseIndex::ROOT,
+                ty::RePlaceholder(placeholder) => placeholder.universe,
+                ty::ReVar(..) | ty::ReLateBound(..) => bug!("not a universal region"),
+            })
+        }
+
+        Ok(match (value1.value, value2.value) {
             // Here we can just pick one value, because the full constraints graph
             // will be handled later. Ideally, we might want a `MultipleValues`
             // variant or something. For now though, this is fine.
-            (Some(_), Some(_)) => *value1,
+            (Some(val1), Some(val2)) => Self { value: Some(min_universe(val1, val2)) },
 
             (Some(_), _) => *value1,
             (_, Some(_)) => *value2,
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index c33b9d84e..b4edb02f6 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -33,13 +33,13 @@
 #![feature(generators)]
 #![feature(get_mut_unchecked)]
 #![feature(if_let_guard)]
+#![feature(inline_const)]
 #![feature(iter_from_generator)]
 #![feature(local_key_cell_methods)]
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(extern_types)]
 #![feature(new_uninit)]
-#![feature(once_cell)]
 #![feature(let_chains)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
@@ -109,4 +109,4 @@ 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" }
+fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_middle/src/macros.rs b/compiler/rustc_middle/src/macros.rs
index a8d71ce03..89014f62d 100644
--- a/compiler/rustc_middle/src/macros.rs
+++ b/compiler/rustc_middle/src/macros.rs
@@ -1,6 +1,6 @@
 /// A macro for triggering an ICE.
 /// Calling `bug` instead of panicking will result in a nicer error message and should
-/// therefore be prefered over `panic`/`unreachable` or others.
+/// therefore be preferred over `panic`/`unreachable` or others.
 ///
 /// If you have a span available, you should use [`span_bug`] instead.
 ///
diff --git a/compiler/rustc_middle/src/metadata.rs b/compiler/rustc_middle/src/metadata.rs
index 5ff014c78..f3170e0ec 100644
--- a/compiler/rustc_middle/src/metadata.rs
+++ b/compiler/rustc_middle/src/metadata.rs
@@ -5,13 +5,34 @@ use rustc_macros::HashStable;
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
+use smallvec::SmallVec;
+
+/// A simplified version of `ImportKind` from resolve.
+/// `DefId`s here correspond to `use` and `extern crate` items themselves, not their targets.
+#[derive(Clone, Copy, Debug, TyEncodable, TyDecodable, HashStable)]
+pub enum Reexport {
+    Single(DefId),
+    Glob(DefId),
+    ExternCrate(DefId),
+    MacroUse,
+    MacroExport,
+}
+
+impl Reexport {
+    pub fn id(self) -> Option<DefId> {
+        match self {
+            Reexport::Single(id) | Reexport::Glob(id) | Reexport::ExternCrate(id) => Some(id),
+            Reexport::MacroUse | Reexport::MacroExport => None,
+        }
+    }
+}
 
 /// This structure is supposed to keep enough data to re-create `NameBinding`s for other crates
 /// during name resolution. Right now the bindings are not recreated entirely precisely so we may
 /// need to add more data in the future to correctly support macros 2.0, for example.
 /// Module child can be either a proper item or a reexport (including private imports).
 /// In case of reexport all the fields describe the reexport item itself, not what it refers to.
-#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ModChild {
     /// Name of the item.
     pub ident: Ident,
@@ -22,6 +43,7 @@ pub struct ModChild {
     pub vis: ty::Visibility<DefId>,
     /// Span of the item.
     pub span: Span,
-    /// A proper `macro_rules` item (not a reexport).
-    pub macro_rules: bool,
+    /// Reexport chain linking this module child to its original reexported item.
+    /// Empty if the module child is a proper item.
+    pub reexport_chain: SmallVec<[Reexport; 2]>,
 }
diff --git a/compiler/rustc_middle/src/middle/exported_symbols.rs b/compiler/rustc_middle/src/middle/exported_symbols.rs
index 631fd09ec..c0c0fd07b 100644
--- a/compiler/rustc_middle/src/middle/exported_symbols.rs
+++ b/compiler/rustc_middle/src/middle/exported_symbols.rs
@@ -43,6 +43,7 @@ pub enum ExportedSymbol<'tcx> {
     NonGeneric(DefId),
     Generic(DefId, SubstsRef<'tcx>),
     DropGlue(Ty<'tcx>),
+    ThreadLocalShim(DefId),
     NoDefId(ty::SymbolName<'tcx>),
 }
 
@@ -58,6 +59,10 @@ impl<'tcx> ExportedSymbol<'tcx> {
             ExportedSymbol::DropGlue(ty) => {
                 tcx.symbol_name(ty::Instance::resolve_drop_in_place(tcx, ty))
             }
+            ExportedSymbol::ThreadLocalShim(def_id) => tcx.symbol_name(ty::Instance {
+                def: ty::InstanceDef::ThreadLocalShim(def_id),
+                substs: ty::InternalSubsts::empty(),
+            }),
             ExportedSymbol::NoDefId(symbol_name) => symbol_name,
         }
     }
diff --git a/compiler/rustc_middle/src/middle/mod.rs b/compiler/rustc_middle/src/middle/mod.rs
index 0b6774f1b..9c25f3009 100644
--- a/compiler/rustc_middle/src/middle/mod.rs
+++ b/compiler/rustc_middle/src/middle/mod.rs
@@ -19,7 +19,7 @@ pub mod lib_features {
                 .stable
                 .iter()
                 .map(|(f, (s, _))| (*f, Some(*s)))
-                .chain(self.unstable.iter().map(|(f, _)| (*f, None)))
+                .chain(self.unstable.keys().map(|f| (*f, None)))
                 .collect();
             all_features.sort_unstable_by(|a, b| a.0.as_str().partial_cmp(b.0.as_str()).unwrap());
             all_features
diff --git a/compiler/rustc_middle/src/middle/privacy.rs b/compiler/rustc_middle/src/middle/privacy.rs
index 893bf54b8..967fed687 100644
--- a/compiler/rustc_middle/src/middle/privacy.rs
+++ b/compiler/rustc_middle/src/middle/privacy.rs
@@ -1,12 +1,12 @@
 //! A pass that checks to make sure private fields and methods aren't used
 //! outside their scopes. This pass will also generate a set of exported items
 //! which are available for use externally when compiled as a library.
-use crate::ty::{DefIdTree, TyCtxt, Visibility};
+use crate::ty::{TyCtxt, Visibility};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
-use rustc_span::def_id::LocalDefId;
+use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
 use std::hash::Hash;
 
 /// Represents the levels of effective visibility an item can have.
@@ -107,12 +107,16 @@ impl EffectiveVisibilities {
         })
     }
 
+    pub fn update_root(&mut self) {
+        self.map.insert(CRATE_DEF_ID, EffectiveVisibility::from_vis(Visibility::Public));
+    }
+
     // FIXME: Share code with `fn update`.
     pub fn update_eff_vis(
         &mut self,
         def_id: LocalDefId,
         eff_vis: &EffectiveVisibility,
-        tree: impl DefIdTree,
+        tcx: TyCtxt<'_>,
     ) {
         use std::collections::hash_map::Entry;
         match self.map.entry(def_id) {
@@ -122,7 +126,7 @@ impl EffectiveVisibilities {
                     let vis_at_level = eff_vis.at_level(l);
                     let old_vis_at_level = old_eff_vis.at_level_mut(l);
                     if vis_at_level != old_vis_at_level
-                        && vis_at_level.is_at_least(*old_vis_at_level, tree)
+                        && vis_at_level.is_at_least(*old_vis_at_level, tcx)
                     {
                         *old_vis_at_level = *vis_at_level
                     }
@@ -219,7 +223,7 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
         lazy_private_vis: impl FnOnce() -> Visibility,
         inherited_effective_vis: EffectiveVisibility,
         level: Level,
-        tree: impl DefIdTree,
+        tcx: TyCtxt<'_>,
     ) -> bool {
         let mut changed = false;
         let mut current_effective_vis = self
@@ -240,7 +244,7 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
                     && level != l)
                 {
                     calculated_effective_vis =
-                        if nominal_vis.is_at_least(inherited_effective_vis_at_level, tree) {
+                        if nominal_vis.is_at_least(inherited_effective_vis_at_level, tcx) {
                             inherited_effective_vis_at_level
                         } else {
                             nominal_vis
@@ -249,7 +253,7 @@ impl<Id: Eq + Hash> EffectiveVisibilities<Id> {
                 // effective visibility can't be decreased at next update call for the
                 // same id
                 if *current_effective_vis_at_level != calculated_effective_vis
-                    && calculated_effective_vis.is_at_least(*current_effective_vis_at_level, tree)
+                    && calculated_effective_vis.is_at_least(*current_effective_vis_at_level, tcx)
                 {
                     changed = true;
                     *current_effective_vis_at_level = calculated_effective_vis;
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 354c84e22..b61f7806b 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -3,7 +3,7 @@
 
 pub use self::StabilityLevel::*;
 
-use crate::ty::{self, DefIdTree, TyCtxt};
+use crate::ty::{self, TyCtxt};
 use rustc_ast::NodeId;
 use rustc_attr::{self as attr, ConstStability, DefaultBodyStability, Deprecation, Stability};
 use rustc_data_structures::fx::FxHashMap;
diff --git a/compiler/rustc_middle/src/mir/basic_blocks.rs b/compiler/rustc_middle/src/mir/basic_blocks.rs
index b93871769..3fb468379 100644
--- a/compiler/rustc_middle/src/mir/basic_blocks.rs
+++ b/compiler/rustc_middle/src/mir/basic_blocks.rs
@@ -6,7 +6,7 @@ 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_index::vec::{IndexSlice, IndexVec};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use smallvec::SmallVec;
 
@@ -124,10 +124,10 @@ impl<'tcx> BasicBlocks<'tcx> {
 }
 
 impl<'tcx> std::ops::Deref for BasicBlocks<'tcx> {
-    type Target = IndexVec<BasicBlock, BasicBlockData<'tcx>>;
+    type Target = IndexSlice<BasicBlock, BasicBlockData<'tcx>>;
 
     #[inline]
-    fn deref(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
+    fn deref(&self) -> &IndexSlice<BasicBlock, BasicBlockData<'tcx>> {
         &self.basic_blocks
     }
 }
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 48375ed30..1a8e48264 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -2,8 +2,6 @@
 
 mod init_mask;
 mod provenance_map;
-#[cfg(test)]
-mod tests;
 
 use std::borrow::Cow;
 use std::fmt;
@@ -111,26 +109,34 @@ const MAX_HASHED_BUFFER_LEN: usize = 2 * MAX_BYTES_TO_HASH;
 // large.
 impl hash::Hash for Allocation {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        let Self {
+            bytes,
+            provenance,
+            init_mask,
+            align,
+            mutability,
+            extra: (), // don't bother hashing ()
+        } = self;
+
         // Partially hash the `bytes` buffer when it is large. To limit collisions with common
         // prefixes and suffixes, we hash the length and some slices of the buffer.
-        let byte_count = self.bytes.len();
+        let byte_count = bytes.len();
         if byte_count > MAX_HASHED_BUFFER_LEN {
             // Hash the buffer's length.
             byte_count.hash(state);
 
             // And its head and tail.
-            self.bytes[..MAX_BYTES_TO_HASH].hash(state);
-            self.bytes[byte_count - MAX_BYTES_TO_HASH..].hash(state);
+            bytes[..MAX_BYTES_TO_HASH].hash(state);
+            bytes[byte_count - MAX_BYTES_TO_HASH..].hash(state);
         } else {
-            self.bytes.hash(state);
+            bytes.hash(state);
         }
 
         // Hash the other fields as usual.
-        self.provenance.hash(state);
-        self.init_mask.hash(state);
-        self.align.hash(state);
-        self.mutability.hash(state);
-        self.extra.hash(state);
+        provenance.hash(state);
+        init_mask.hash(state);
+        align.hash(state);
+        mutability.hash(state);
     }
 }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
index 82e9a961a..dcb56a175 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
@@ -1,3 +1,6 @@
+#[cfg(test)]
+mod tests;
+
 use std::hash;
 use std::iter;
 use std::ops::Range;
@@ -10,20 +13,185 @@ type Block = u64;
 
 /// A bitmask where each bit refers to the byte with the same index. If the bit is `true`, the byte
 /// is initialized. If it is `false` the byte is uninitialized.
-// Note: for performance reasons when interning, some of the `InitMask` fields can be partially
-// hashed. (see the `Hash` impl below for more details), so the impl is not derived.
-#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable)]
-#[derive(HashStable)]
+/// The actual bits are only materialized when needed, and we try to keep this data lazy as long as
+/// possible. Currently, if all the blocks have the same value, then the mask represents either a
+/// fully initialized or fully uninitialized const allocation, so we can only store that single
+/// value.
+#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
 pub struct InitMask {
-    blocks: Vec<Block>,
+    blocks: InitMaskBlocks,
     len: Size,
 }
 
+#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+enum InitMaskBlocks {
+    Lazy {
+        /// Whether the lazy init mask is fully initialized or uninitialized.
+        state: bool,
+    },
+    Materialized(InitMaskMaterialized),
+}
+
+impl InitMask {
+    pub fn new(size: Size, state: bool) -> Self {
+        // Blocks start lazily allocated, until we have to materialize them.
+        let blocks = InitMaskBlocks::Lazy { state };
+        InitMask { len: size, blocks }
+    }
+
+    /// Checks whether the `range` is entirely initialized.
+    ///
+    /// Returns `Ok(())` if it's initialized. Otherwise returns a range of byte
+    /// indexes for the first contiguous span of the uninitialized access.
+    #[inline]
+    pub fn is_range_initialized(&self, range: AllocRange) -> Result<(), AllocRange> {
+        let end = range.end();
+        if end > self.len {
+            return Err(AllocRange::from(self.len..end));
+        }
+
+        match self.blocks {
+            InitMaskBlocks::Lazy { state } => {
+                // Lazily allocated blocks represent the full mask, and cover the requested range by
+                // definition.
+                if state { Ok(()) } else { Err(range) }
+            }
+            InitMaskBlocks::Materialized(ref blocks) => {
+                blocks.is_range_initialized(range.start, end)
+            }
+        }
+    }
+
+    /// Sets a specified range to a value. If the range is out-of-bounds, the mask will grow to
+    /// accommodate it entirely.
+    pub fn set_range(&mut self, range: AllocRange, new_state: bool) {
+        let start = range.start;
+        let end = range.end();
+
+        let is_full_overwrite = start == Size::ZERO && end >= self.len;
+
+        // Optimize the cases of a full init/uninit state, while handling growth if needed.
+        match self.blocks {
+            InitMaskBlocks::Lazy { ref mut state } if is_full_overwrite => {
+                // This is fully overwriting the mask, and we'll still have a single initialization
+                // state: the blocks can stay lazy.
+                *state = new_state;
+                self.len = end;
+            }
+            InitMaskBlocks::Materialized(_) if is_full_overwrite => {
+                // This is also fully overwriting materialized blocks with a single initialization
+                // state: we'll have no need for these blocks anymore and can make them lazy.
+                self.blocks = InitMaskBlocks::Lazy { state: new_state };
+                self.len = end;
+            }
+            InitMaskBlocks::Lazy { state } if state == new_state => {
+                // Here we're partially overwriting the mask but the initialization state doesn't
+                // change: the blocks can stay lazy.
+                if end > self.len {
+                    self.len = end;
+                }
+            }
+            _ => {
+                // Otherwise, we have a partial overwrite that can result in a mix of initialization
+                // states, so we'll need materialized blocks.
+                let len = self.len;
+                let blocks = self.materialize_blocks();
+
+                // There are 3 cases of interest here, if we have:
+                //
+                //         [--------]
+                //         ^        ^
+                //         0        len
+                //
+                // 1) the range to set can be in-bounds:
+                //
+                //            xxxx = [start, end]
+                //         [--------]
+                //         ^        ^
+                //         0        len
+                //
+                // Here, we'll simply set the single `start` to `end` range.
+                //
+                // 2) the range to set can be partially out-of-bounds:
+                //
+                //                xxxx = [start, end]
+                //         [--------]
+                //         ^        ^
+                //         0        len
+                //
+                // We have 2 subranges to handle:
+                // - we'll set the existing `start` to `len` range.
+                // - we'll grow and set the `len` to `end` range.
+                //
+                // 3) the range to set can be fully out-of-bounds:
+                //
+                //                   ---xxxx = [start, end]
+                //         [--------]
+                //         ^        ^
+                //         0        len
+                //
+                // Since we're growing the mask to a single `new_state` value, we consider the gap
+                // from `len` to `start` to be part of the range, and have a single subrange to
+                // handle: we'll grow and set the `len` to `end` range.
+                //
+                // Note that we have to materialize, set blocks, and grow the mask. We could
+                // therefore slightly optimize things in situations where these writes overlap.
+                // However, as of writing this, growing the mask doesn't happen in practice yet, so
+                // we don't do this micro-optimization.
+
+                if end <= len {
+                    // Handle case 1.
+                    blocks.set_range_inbounds(start, end, new_state);
+                } else {
+                    if start < len {
+                        // Handle the first subrange of case 2.
+                        blocks.set_range_inbounds(start, len, new_state);
+                    }
+
+                    // Handle the second subrange of case 2, and case 3.
+                    blocks.grow(len, end - len, new_state); // `Size` operation
+                    self.len = end;
+                }
+            }
+        }
+    }
+
+    /// Materializes this mask's blocks when the mask is lazy.
+    #[inline]
+    fn materialize_blocks(&mut self) -> &mut InitMaskMaterialized {
+        if let InitMaskBlocks::Lazy { state } = self.blocks {
+            self.blocks = InitMaskBlocks::Materialized(InitMaskMaterialized::new(self.len, state));
+        }
+
+        let InitMaskBlocks::Materialized(ref mut blocks) = self.blocks else {
+            bug!("initmask blocks must be materialized here")
+        };
+        blocks
+    }
+
+    /// Returns the initialization state at the specified in-bounds index.
+    #[inline]
+    pub fn get(&self, idx: Size) -> bool {
+        match self.blocks {
+            InitMaskBlocks::Lazy { state } => state,
+            InitMaskBlocks::Materialized(ref blocks) => blocks.get(idx),
+        }
+    }
+}
+
+/// The actual materialized blocks of the bitmask, when we can't keep the `InitMask` lazy.
+// Note: for performance reasons when interning, some of the fields can be partially
+// hashed. (see the `Hash` impl below for more details), so the impl is not derived.
+#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, HashStable)]
+struct InitMaskMaterialized {
+    blocks: Vec<Block>,
+}
+
 // Const allocations are only hashed for interning. However, they can be large, making the hashing
 // expensive especially since it uses `FxHash`: it's better suited to short keys, not potentially
 // big buffers like the allocation's init mask. We can partially hash some fields when they're
 // large.
-impl hash::Hash for InitMask {
+impl hash::Hash for InitMaskMaterialized {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
         const MAX_BLOCKS_TO_HASH: usize = super::MAX_BYTES_TO_HASH / std::mem::size_of::<Block>();
         const MAX_BLOCKS_LEN: usize = super::MAX_HASHED_BUFFER_LEN / std::mem::size_of::<Block>();
@@ -41,18 +209,15 @@ impl hash::Hash for InitMask {
         } else {
             self.blocks.hash(state);
         }
-
-        // Hash the other fields as usual.
-        self.len.hash(state);
     }
 }
 
-impl InitMask {
+impl InitMaskMaterialized {
     pub const BLOCK_SIZE: u64 = 64;
 
-    pub fn new(size: Size, state: bool) -> Self {
-        let mut m = InitMask { blocks: vec![], len: Size::ZERO };
-        m.grow(size, state);
+    fn new(size: Size, state: bool) -> Self {
+        let mut m = InitMaskMaterialized { blocks: vec![] };
+        m.grow(Size::ZERO, size, state);
         m
     }
 
@@ -62,8 +227,8 @@ impl InitMask {
         // Each bit in a `Block` represents the initialization state of one byte of an allocation,
         // so we use `.bytes()` here.
         let bits = bits.bytes();
-        let a = bits / InitMask::BLOCK_SIZE;
-        let b = bits % InitMask::BLOCK_SIZE;
+        let a = bits / Self::BLOCK_SIZE;
+        let b = bits % Self::BLOCK_SIZE;
         (usize::try_from(a).unwrap(), usize::try_from(b).unwrap())
     }
 
@@ -71,7 +236,7 @@ impl InitMask {
     fn size_from_bit_index(block: impl TryInto<u64>, bit: impl TryInto<u64>) -> Size {
         let block = block.try_into().ok().unwrap();
         let bit = bit.try_into().ok().unwrap();
-        Size::from_bytes(block * InitMask::BLOCK_SIZE + bit)
+        Size::from_bytes(block * Self::BLOCK_SIZE + bit)
     }
 
     /// Checks whether the `range` is entirely initialized.
@@ -79,13 +244,8 @@ impl InitMask {
     /// Returns `Ok(())` if it's initialized. Otherwise returns a range of byte
     /// indexes for the first contiguous span of the uninitialized access.
     #[inline]
-    pub fn is_range_initialized(&self, range: AllocRange) -> Result<(), AllocRange> {
-        let end = range.end();
-        if end > self.len {
-            return Err(AllocRange::from(self.len..end));
-        }
-
-        let uninit_start = self.find_bit(range.start, end, false);
+    fn is_range_initialized(&self, start: Size, end: Size) -> Result<(), AllocRange> {
+        let uninit_start = self.find_bit(start, end, false);
 
         match uninit_start {
             Some(uninit_start) => {
@@ -96,81 +256,80 @@ impl InitMask {
         }
     }
 
-    pub fn set_range(&mut self, range: AllocRange, new_state: bool) {
-        let end = range.end();
-        let len = self.len;
-        if end > len {
-            self.grow(end - len, new_state);
-        }
-        self.set_range_inbounds(range.start, end, new_state);
-    }
-
     fn set_range_inbounds(&mut self, start: Size, end: Size, new_state: bool) {
-        let (blocka, bita) = Self::bit_index(start);
-        let (blockb, bitb) = Self::bit_index(end);
-        if blocka == blockb {
-            // First set all bits except the first `bita`,
-            // then unset the last `64 - bitb` bits.
-            let range = if bitb == 0 {
-                u64::MAX << bita
+        let (block_a, bit_a) = Self::bit_index(start);
+        let (block_b, bit_b) = Self::bit_index(end);
+        if block_a == block_b {
+            // First set all bits except the first `bit_a`,
+            // then unset the last `64 - bit_b` bits.
+            let range = if bit_b == 0 {
+                u64::MAX << bit_a
             } else {
-                (u64::MAX << bita) & (u64::MAX >> (64 - bitb))
+                (u64::MAX << bit_a) & (u64::MAX >> (64 - bit_b))
             };
             if new_state {
-                self.blocks[blocka] |= range;
+                self.blocks[block_a] |= range;
             } else {
-                self.blocks[blocka] &= !range;
+                self.blocks[block_a] &= !range;
             }
             return;
         }
         // across block boundaries
         if new_state {
-            // Set `bita..64` to `1`.
-            self.blocks[blocka] |= u64::MAX << bita;
-            // Set `0..bitb` to `1`.
-            if bitb != 0 {
-                self.blocks[blockb] |= u64::MAX >> (64 - bitb);
+            // Set `bit_a..64` to `1`.
+            self.blocks[block_a] |= u64::MAX << bit_a;
+            // Set `0..bit_b` to `1`.
+            if bit_b != 0 {
+                self.blocks[block_b] |= u64::MAX >> (64 - bit_b);
             }
             // Fill in all the other blocks (much faster than one bit at a time).
-            for block in (blocka + 1)..blockb {
+            for block in (block_a + 1)..block_b {
                 self.blocks[block] = u64::MAX;
             }
         } else {
-            // Set `bita..64` to `0`.
-            self.blocks[blocka] &= !(u64::MAX << bita);
-            // Set `0..bitb` to `0`.
-            if bitb != 0 {
-                self.blocks[blockb] &= !(u64::MAX >> (64 - bitb));
+            // Set `bit_a..64` to `0`.
+            self.blocks[block_a] &= !(u64::MAX << bit_a);
+            // Set `0..bit_b` to `0`.
+            if bit_b != 0 {
+                self.blocks[block_b] &= !(u64::MAX >> (64 - bit_b));
             }
             // Fill in all the other blocks (much faster than one bit at a time).
-            for block in (blocka + 1)..blockb {
+            for block in (block_a + 1)..block_b {
                 self.blocks[block] = 0;
             }
         }
     }
 
     #[inline]
-    pub fn get(&self, i: Size) -> bool {
+    fn get(&self, i: Size) -> bool {
         let (block, bit) = Self::bit_index(i);
         (self.blocks[block] & (1 << bit)) != 0
     }
 
-    fn grow(&mut self, amount: Size, new_state: bool) {
+    fn grow(&mut self, len: Size, amount: Size, new_state: bool) {
         if amount.bytes() == 0 {
             return;
         }
         let unused_trailing_bits =
-            u64::try_from(self.blocks.len()).unwrap() * Self::BLOCK_SIZE - self.len.bytes();
+            u64::try_from(self.blocks.len()).unwrap() * Self::BLOCK_SIZE - len.bytes();
+
+        // If there's not enough capacity in the currently allocated blocks, allocate some more.
         if amount.bytes() > unused_trailing_bits {
             let additional_blocks = amount.bytes() / Self::BLOCK_SIZE + 1;
-            self.blocks.extend(
-                // FIXME(oli-obk): optimize this by repeating `new_state as Block`.
-                iter::repeat(0).take(usize::try_from(additional_blocks).unwrap()),
-            );
+
+            // We allocate the blocks to the correct value for the requested init state, so we won't
+            // have to manually set them with another write.
+            let block = if new_state { u64::MAX } else { 0 };
+            self.blocks
+                .extend(iter::repeat(block).take(usize::try_from(additional_blocks).unwrap()));
+        }
+
+        // New blocks have already been set here, so we only need to set the unused trailing bits,
+        // if any.
+        if unused_trailing_bits > 0 {
+            let in_bounds_tail = Size::from_bytes(unused_trailing_bits);
+            self.set_range_inbounds(len, len + in_bounds_tail, new_state); // `Size` operation
         }
-        let start = self.len;
-        self.len += amount;
-        self.set_range_inbounds(start, start + amount, new_state); // `Size` operation
     }
 
     /// Returns the index of the first bit in `start..end` (end-exclusive) that is equal to is_init.
@@ -188,7 +347,7 @@ impl InitMask {
         /// ```
         /// Also, if not stated, assume that `is_init = true`, that is, we are searching for the first 1 bit.
         fn find_bit_fast(
-            init_mask: &InitMask,
+            init_mask: &InitMaskMaterialized,
             start: Size,
             end: Size,
             is_init: bool,
@@ -223,7 +382,7 @@ impl InitMask {
                     None
                 } else {
                     let bit = bits.trailing_zeros();
-                    Some(InitMask::size_from_bit_index(block, bit))
+                    Some(InitMaskMaterialized::size_from_bit_index(block, bit))
                 }
             }
 
@@ -253,9 +412,9 @@ impl InitMask {
             // This provides the desired behavior of searching blocks 0 and 1 for (a),
             // and searching only block 0 for (b).
             // There is no concern of overflows since we checked for `start >= end` above.
-            let (start_block, start_bit) = InitMask::bit_index(start);
+            let (start_block, start_bit) = InitMaskMaterialized::bit_index(start);
             let end_inclusive = Size::from_bytes(end.bytes() - 1);
-            let (end_block_inclusive, _) = InitMask::bit_index(end_inclusive);
+            let (end_block_inclusive, _) = InitMaskMaterialized::bit_index(end_inclusive);
 
             // Handle first block: need to skip `start_bit` bits.
             //
@@ -340,7 +499,7 @@ impl InitMask {
 
         #[cfg_attr(not(debug_assertions), allow(dead_code))]
         fn find_bit_slow(
-            init_mask: &InitMask,
+            init_mask: &InitMaskMaterialized,
             start: Size,
             end: Size,
             is_init: bool,
@@ -436,10 +595,19 @@ impl<'a> Iterator for InitChunkIter<'a> {
             return None;
         }
 
-        let end_of_chunk =
-            self.init_mask.find_bit(self.start, self.end, !self.is_init).unwrap_or(self.end);
+        let end_of_chunk = match self.init_mask.blocks {
+            InitMaskBlocks::Lazy { .. } => {
+                // If we're iterating over the chunks of lazy blocks, we just emit a single
+                // full-size chunk.
+                self.end
+            }
+            InitMaskBlocks::Materialized(ref blocks) => {
+                let end_of_chunk =
+                    blocks.find_bit(self.start, self.end, !self.is_init).unwrap_or(self.end);
+                end_of_chunk
+            }
+        };
         let range = self.start..end_of_chunk;
-
         let ret =
             Some(if self.is_init { InitChunk::Init(range) } else { InitChunk::Uninit(range) });
 
@@ -504,17 +672,19 @@ impl InitMask {
 
     /// Applies multiple instances of the run-length encoding to the initialization mask.
     pub fn apply_copy(&mut self, defined: InitCopy, range: AllocRange, repeat: u64) {
-        // An optimization where we can just overwrite an entire range of initialization
-        // bits if they are going to be uniformly `1` or `0`.
+        // An optimization where we can just overwrite an entire range of initialization bits if
+        // they are going to be uniformly `1` or `0`. If this happens to be a full-range overwrite,
+        // we won't need materialized blocks either.
         if defined.ranges.len() <= 1 {
-            self.set_range_inbounds(
-                range.start,
-                range.start + range.size * repeat, // `Size` operations
-                defined.initial,
-            );
+            let start = range.start;
+            let end = range.start + range.size * repeat; // `Size` operations
+            self.set_range(AllocRange::from(start..end), defined.initial);
             return;
         }
 
+        // We're about to do one or more partial writes, so we ensure the blocks are materialized.
+        let blocks = self.materialize_blocks();
+
         for mut j in 0..repeat {
             j *= range.size.bytes();
             j += range.start.bytes();
@@ -522,7 +692,7 @@ impl InitMask {
             for range in &defined.ranges {
                 let old_j = j;
                 j += range;
-                self.set_range_inbounds(Size::from_bytes(old_j), Size::from_bytes(j), cur);
+                blocks.set_range_inbounds(Size::from_bytes(old_j), Size::from_bytes(j), cur);
                 cur = !cur;
             }
         }
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask/tests.rs b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask/tests.rs
new file mode 100644
index 000000000..1a7934bc2
--- /dev/null
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask/tests.rs
@@ -0,0 +1,195 @@
+use super::*;
+use crate::mir::interpret::alloc_range;
+
+#[test]
+fn uninit_mask() {
+    let mut mask = InitMask::new(Size::from_bytes(500), false);
+    assert!(!mask.get(Size::from_bytes(499)));
+    mask.set_range(alloc_range(Size::from_bytes(499), Size::from_bytes(1)), true);
+    assert!(mask.get(Size::from_bytes(499)));
+    mask.set_range((100..256).into(), true);
+    for i in 0..100 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+    for i in 100..256 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+    for i in 256..499 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+}
+
+/// Returns the number of materialized blocks for this mask.
+fn materialized_block_count(mask: &InitMask) -> usize {
+    match mask.blocks {
+        InitMaskBlocks::Lazy { .. } => 0,
+        InitMaskBlocks::Materialized(ref blocks) => blocks.blocks.len(),
+    }
+}
+
+#[test]
+fn materialize_mask_within_range() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), false);
+    assert_eq!(materialized_block_count(&mask), 0);
+
+    // Forces materialization, but doesn't require growth. This is case #1 documented in the
+    // `set_range` method.
+    mask.set_range((8..16).into(), true);
+    assert_eq!(materialized_block_count(&mask), 1);
+
+    for i in 0..8 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+    for i in 8..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+}
+
+#[test]
+fn grow_within_unused_bits_with_full_overwrite() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    for i in 0..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    // Grow without requiring an additional block. Full overwrite.
+    // This can be fully handled without materialization.
+    let range = (0..32).into();
+    mask.set_range(range, true);
+
+    for i in 0..32 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    assert_eq!(materialized_block_count(&mask), 0);
+}
+
+// This test checks that an initmask's spare capacity is correctly used when growing within block
+// capacity. This can be fully handled without materialization.
+#[test]
+fn grow_same_state_within_unused_bits() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    for i in 0..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    // Grow without requiring an additional block. The gap between the current length and the
+    // range's beginning should be set to the same value as the range.
+    let range = (24..32).into();
+    mask.set_range(range, true);
+
+    // We want to make sure the unused bits in the first block are correct
+    for i in 16..24 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    for i in 24..32 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    assert_eq!(1, mask.range_as_init_chunks((0..32).into()).count());
+    assert_eq!(materialized_block_count(&mask), 0);
+}
+
+// This is the same test as `grow_same_state_within_unused_bits` but with both init and uninit
+// states: this forces materialization; otherwise the mask could stay lazy even when needing to
+// grow.
+#[test]
+fn grow_mixed_state_within_unused_bits() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    for i in 0..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    // Grow without requiring an additional block. The gap between the current length and the
+    // range's beginning should be set to the same value as the range. Note: since this is fully
+    // out-of-bounds of the current mask, this is case #3 described in the `set_range` method.
+    let range = (24..32).into();
+    mask.set_range(range, false);
+
+    // We want to make sure the unused bits in the first block are correct
+    for i in 16..24 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+
+    for i in 24..32 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+
+    assert_eq!(1, mask.range_as_init_chunks((0..16).into()).count());
+    assert_eq!(2, mask.range_as_init_chunks((0..32).into()).count());
+    assert_eq!(materialized_block_count(&mask), 1);
+}
+
+// This is similar to `grow_mixed_state_within_unused_bits` to force materialization, but the range
+// to set partially overlaps the mask, so this requires a different growth + write pattern in the
+// mask.
+#[test]
+fn grow_within_unused_bits_with_overlap() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    for i in 0..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+
+    // Grow without requiring an additional block, but leave no gap after the current len. Note:
+    // since this is partially out-of-bounds of the current mask, this is case #2 described in the
+    // `set_range` method.
+    let range = (8..24).into();
+    mask.set_range(range, false);
+
+    // We want to make sure the unused bits in the first block are correct
+    for i in 8..24 {
+        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
+    }
+
+    assert_eq!(1, mask.range_as_init_chunks((0..8).into()).count());
+    assert_eq!(2, mask.range_as_init_chunks((0..24).into()).count());
+    assert_eq!(materialized_block_count(&mask), 1);
+}
+
+// Force materialization before a full overwrite: the mask can now become lazy.
+#[test]
+fn grow_mixed_state_within_unused_bits_and_full_overwrite() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    let range = (0..16).into();
+    assert!(mask.is_range_initialized(range).is_ok());
+
+    // Force materialization.
+    let range = (8..24).into();
+    mask.set_range(range, false);
+    assert!(mask.is_range_initialized(range).is_err());
+    assert_eq!(materialized_block_count(&mask), 1);
+
+    // Full overwrite, lazy blocks would be enough from now on.
+    let range = (0..32).into();
+    mask.set_range(range, true);
+    assert!(mask.is_range_initialized(range).is_ok());
+
+    assert_eq!(1, mask.range_as_init_chunks((0..32).into()).count());
+    assert_eq!(materialized_block_count(&mask), 0);
+}
+
+// Check that growth outside the current capacity can still be lazy: if the init state doesn't
+// change, we don't need materialized blocks.
+#[test]
+fn grow_same_state_outside_capacity() {
+    // To have spare bits, we use a mask size smaller than its block size of 64.
+    let mut mask = InitMask::new(Size::from_bytes(16), true);
+    for i in 0..16 {
+        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
+    }
+    assert_eq!(materialized_block_count(&mask), 0);
+
+    // Grow to 10 blocks with the same init state.
+    let range = (24..640).into();
+    mask.set_range(range, true);
+
+    assert_eq!(1, mask.range_as_init_chunks((0..640).into()).count());
+    assert_eq!(materialized_block_count(&mask), 0);
+}
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
index ddd3f3943..318f93e12 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
@@ -14,7 +14,7 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 #[derive(HashStable)]
 pub struct ProvenanceMap<Prov = AllocId> {
     /// Provenance in this map applies from the given offset for an entire pointer-size worth of
-    /// bytes. Two entires in this map are always at least a pointer size apart.
+    /// bytes. Two entries in this map are always at least a pointer size apart.
     ptrs: SortedMap<Size, Prov>,
     /// Provenance in this map only applies to the given single byte.
     /// This map is disjoint from the previous. It will always be empty when
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/tests.rs b/compiler/rustc_middle/src/mir/interpret/allocation/tests.rs
deleted file mode 100644
index c9c3c50c5..000000000
--- a/compiler/rustc_middle/src/mir/interpret/allocation/tests.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-use super::*;
-
-#[test]
-fn uninit_mask() {
-    let mut mask = InitMask::new(Size::from_bytes(500), false);
-    assert!(!mask.get(Size::from_bytes(499)));
-    mask.set_range(alloc_range(Size::from_bytes(499), Size::from_bytes(1)), true);
-    assert!(mask.get(Size::from_bytes(499)));
-    mask.set_range((100..256).into(), true);
-    for i in 0..100 {
-        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
-    }
-    for i in 100..256 {
-        assert!(mask.get(Size::from_bytes(i)), "{i} should be set");
-    }
-    for i in 256..499 {
-        assert!(!mask.get(Size::from_bytes(i)), "{i} should not be set");
-    }
-}
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index 1766d7a66..1f8b650e3 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -263,7 +263,8 @@ impl AllocDecodingState {
     }
 
     pub fn new(data_offsets: Vec<u32>) -> Self {
-        let decoding_state = vec![Lock::new(State::Empty); data_offsets.len()];
+        let decoding_state =
+            std::iter::repeat_with(|| Lock::new(State::Empty)).take(data_offsets.len()).collect();
 
         Self { decoding_state, data_offsets }
     }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 99cdb769d..2ea8602af 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -10,7 +10,7 @@ use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor};
-use crate::ty::{self, DefIdTree, List, Ty, TyCtxt};
+use crate::ty::{self, List, Ty, TyCtxt};
 use crate::ty::{AdtDef, InstanceDef, ScalarInt, UserTypeAnnotationIndex};
 use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
 
@@ -21,13 +21,13 @@ use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_hir::{self, GeneratorKind, ImplicitSelfKind};
 use rustc_hir::{self as hir, HirId};
 use rustc_session::Session;
-use rustc_target::abi::{Size, VariantIdx};
+use rustc_target::abi::{FieldIdx, Size, VariantIdx};
 
 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::vec::{Idx, IndexVec};
+use rustc_index::vec::{Idx, IndexSlice, IndexVec};
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
@@ -70,12 +70,19 @@ pub use self::pretty::{
 };
 
 /// Types for locals
-pub type LocalDecls<'tcx> = IndexVec<Local, LocalDecl<'tcx>>;
+pub type LocalDecls<'tcx> = IndexSlice<Local, LocalDecl<'tcx>>;
 
 pub trait HasLocalDecls<'tcx> {
     fn local_decls(&self) -> &LocalDecls<'tcx>;
 }
 
+impl<'tcx> HasLocalDecls<'tcx> for IndexVec<Local, LocalDecl<'tcx>> {
+    #[inline]
+    fn local_decls(&self) -> &LocalDecls<'tcx> {
+        self
+    }
+}
+
 impl<'tcx> HasLocalDecls<'tcx> for LocalDecls<'tcx> {
     #[inline]
     fn local_decls(&self) -> &LocalDecls<'tcx> {
@@ -250,7 +257,7 @@ pub struct Body<'tcx> {
     /// The first local is the return value pointer, followed by `arg_count`
     /// locals for the function arguments, followed by any user-declared
     /// variables and temporaries.
-    pub local_decls: LocalDecls<'tcx>,
+    pub local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 
     /// User type annotations.
     pub user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
@@ -311,7 +318,7 @@ impl<'tcx> Body<'tcx> {
         source: MirSource<'tcx>,
         basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
         source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
-        local_decls: LocalDecls<'tcx>,
+        local_decls: IndexVec<Local, LocalDecl<'tcx>>,
         user_type_annotations: ty::CanonicalUserTypeAnnotations<'tcx>,
         arg_count: usize,
         var_debug_info: Vec<VarDebugInfo<'tcx>>,
@@ -401,8 +408,6 @@ impl<'tcx> Body<'tcx> {
             LocalKind::ReturnPointer
         } else if index < self.arg_count + 1 {
             LocalKind::Arg
-        } else if self.local_decls[local].is_user_variable() {
-            LocalKind::Var
         } else {
             LocalKind::Temp
         }
@@ -572,6 +577,13 @@ impl<T> ClearCrossCrate<T> {
         }
     }
 
+    pub fn as_mut(&mut self) -> ClearCrossCrate<&mut T> {
+        match self {
+            ClearCrossCrate::Clear => ClearCrossCrate::Clear,
+            ClearCrossCrate::Set(v) => ClearCrossCrate::Set(v),
+        }
+    }
+
     pub fn assert_crate_local(self) -> T {
         match self {
             ClearCrossCrate::Clear => bug!("unwrapping cross-crate data"),
@@ -661,9 +673,7 @@ impl Atom for Local {
 /// Classifies locals into categories. See `Body::local_kind`.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable)]
 pub enum LocalKind {
-    /// User-declared variable binding.
-    Var,
-    /// Compiler-introduced temporary.
+    /// User-declared variable binding or compiler-introduced temporary.
     Temp,
     /// Function argument.
     Arg,
@@ -760,7 +770,7 @@ pub struct LocalDecl<'tcx> {
     pub mutability: Mutability,
 
     // FIXME(matthewjasper) Don't store in this in `Body`
-    pub local_info: Option<Box<LocalInfo<'tcx>>>,
+    pub local_info: ClearCrossCrate<Box<LocalInfo<'tcx>>>,
 
     /// `true` if this is an internal local.
     ///
@@ -778,13 +788,6 @@ pub struct LocalDecl<'tcx> {
     /// generator.
     pub internal: bool,
 
-    /// If this local is a temporary and `is_block_tail` is `Some`,
-    /// then it is a temporary created for evaluation of some
-    /// subexpression of some block's tail expression (with no
-    /// intervening statement context).
-    // FIXME(matthewjasper) Don't store in this in `Body`
-    pub is_block_tail: Option<BlockTailInfo>,
-
     /// The type of this local.
     pub ty: Ty<'tcx>,
 
@@ -890,7 +893,7 @@ pub enum LocalInfo<'tcx> {
     /// The `BindingForm` is solely used for local diagnostics when generating
     /// warnings/errors when compiling the current crate, and therefore it need
     /// not be visible across crates.
-    User(ClearCrossCrate<BindingForm<'tcx>>),
+    User(BindingForm<'tcx>),
     /// A temporary created that references the static with the given `DefId`.
     StaticRef { def_id: DefId, is_thread_local: bool },
     /// A temporary created that references the const with the given `DefId`
@@ -898,13 +901,23 @@ pub enum LocalInfo<'tcx> {
     /// A temporary created during the creation of an aggregate
     /// (e.g. a temporary for `foo` in `MyStruct { my_field: foo }`)
     AggregateTemp,
+    /// A temporary created for evaluation of some subexpression of some block's tail expression
+    /// (with no intervening statement context).
+    // FIXME(matthewjasper) Don't store in this in `Body`
+    BlockTailTemp(BlockTailInfo),
     /// A temporary created during the pass `Derefer` to avoid it's retagging
     DerefTemp,
     /// A temporary created for borrow checking.
     FakeBorrow,
+    /// A local without anything interesting about it.
+    Boring,
 }
 
 impl<'tcx> LocalDecl<'tcx> {
+    pub fn local_info(&self) -> &LocalInfo<'tcx> {
+        &self.local_info.as_ref().assert_crate_local()
+    }
+
     /// Returns `true` only if local is a binding that can itself be
     /// made mutable via the addition of the `mut` keyword, namely
     /// something like the occurrences of `x` in:
@@ -913,15 +926,15 @@ impl<'tcx> LocalDecl<'tcx> {
     /// - or `match ... { C(x) => ... }`
     pub fn can_be_made_mutable(&self) -> bool {
         matches!(
-            self.local_info,
-            Some(box LocalInfo::User(ClearCrossCrate::Set(
+            self.local_info(),
+            LocalInfo::User(
                 BindingForm::Var(VarBindingForm {
                     binding_mode: ty::BindingMode::BindByValue(_),
                     opt_ty_info: _,
                     opt_match_place: _,
                     pat_span: _,
                 }) | BindingForm::ImplicitSelf(ImplicitSelfKind::Imm),
-            )))
+            )
         )
     }
 
@@ -930,15 +943,15 @@ impl<'tcx> LocalDecl<'tcx> {
     /// mutable bindings, but the inverse does not necessarily hold).
     pub fn is_nonref_binding(&self) -> bool {
         matches!(
-            self.local_info,
-            Some(box LocalInfo::User(ClearCrossCrate::Set(
+            self.local_info(),
+            LocalInfo::User(
                 BindingForm::Var(VarBindingForm {
                     binding_mode: ty::BindingMode::BindByValue(_),
                     opt_ty_info: _,
                     opt_match_place: _,
                     pat_span: _,
                 }) | BindingForm::ImplicitSelf(_),
-            )))
+            )
         )
     }
 
@@ -946,38 +959,35 @@ impl<'tcx> LocalDecl<'tcx> {
     /// parameter declared by the user.
     #[inline]
     pub fn is_user_variable(&self) -> bool {
-        matches!(self.local_info, Some(box LocalInfo::User(_)))
+        matches!(self.local_info(), LocalInfo::User(_))
     }
 
     /// Returns `true` if this is a reference to a variable bound in a `match`
     /// expression that is used to access said variable for the guard of the
     /// match arm.
     pub fn is_ref_for_guard(&self) -> bool {
-        matches!(
-            self.local_info,
-            Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::RefForGuard)))
-        )
+        matches!(self.local_info(), LocalInfo::User(BindingForm::RefForGuard))
     }
 
     /// Returns `Some` if this is a reference to a static item that is used to
     /// access that static.
     pub fn is_ref_to_static(&self) -> bool {
-        matches!(self.local_info, Some(box LocalInfo::StaticRef { .. }))
+        matches!(self.local_info(), LocalInfo::StaticRef { .. })
     }
 
     /// Returns `Some` if this is a reference to a thread-local static item that is used to
     /// access that static.
     pub fn is_ref_to_thread_local(&self) -> bool {
-        match self.local_info {
-            Some(box LocalInfo::StaticRef { is_thread_local, .. }) => is_thread_local,
+        match self.local_info() {
+            LocalInfo::StaticRef { is_thread_local, .. } => *is_thread_local,
             _ => false,
         }
     }
 
     /// Returns `true` if this is a DerefTemp
     pub fn is_deref_temp(&self) -> bool {
-        match self.local_info {
-            Some(box LocalInfo::DerefTemp) => return true,
+        match self.local_info() {
+            LocalInfo::DerefTemp => return true,
             _ => (),
         }
         return false;
@@ -1001,9 +1011,8 @@ impl<'tcx> LocalDecl<'tcx> {
     pub fn with_source_info(ty: Ty<'tcx>, source_info: SourceInfo) -> Self {
         LocalDecl {
             mutability: Mutability::Mut,
-            local_info: None,
+            local_info: ClearCrossCrate::Set(Box::new(LocalInfo::Boring)),
             internal: false,
-            is_block_tail: None,
             ty,
             user_ty: None,
             source_info,
@@ -1023,20 +1032,11 @@ impl<'tcx> LocalDecl<'tcx> {
         self.mutability = Mutability::Not;
         self
     }
-
-    /// Converts `self` into same `LocalDecl` except tagged as internal temporary.
-    #[inline]
-    pub fn block_tail(mut self, info: BlockTailInfo) -> Self {
-        assert!(self.is_block_tail.is_none());
-        self.is_block_tail = Some(info);
-        self
-    }
 }
 
 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum VarDebugInfoContents<'tcx> {
-    /// NOTE(eddyb) There's an unenforced invariant that this `Place` is
-    /// based on a `Local`, not a `Static`, and contains no indexing.
+    /// This `Place` only contains projection which satisfy `can_use_in_debuginfo`.
     Place(Place<'tcx>),
     Const(Constant<'tcx>),
     /// The user variable's data is split across several fragments,
@@ -1046,6 +1046,7 @@ pub enum VarDebugInfoContents<'tcx> {
     /// the underlying debuginfo feature this relies on.
     Composite {
         /// Type of the original user variable.
+        /// This cannot contain a union or an enum.
         ty: Ty<'tcx>,
         /// All the parts of the original user variable, which ended
         /// up in disjoint places, due to optimizations.
@@ -1074,17 +1075,16 @@ pub struct VarDebugInfoFragment<'tcx> {
     /// Where in the composite user variable this fragment is,
     /// represented as a "projection" into the composite variable.
     /// At lower levels, this corresponds to a byte/bit range.
-    // NOTE(eddyb) there's an unenforced invariant that this contains
-    // only `Field`s, and not into `enum` variants or `union`s.
-    // FIXME(eddyb) support this for `enum`s by either using DWARF's
+    ///
+    /// This can only contain `PlaceElem::Field`.
+    // FIXME support this for `enum`s by either using DWARF's
     // more advanced control-flow features (unsupported by LLVM?)
     // to match on the discriminant, or by using custom type debuginfo
     // with non-overlapping variants for the composite variable.
     pub projection: Vec<PlaceElem<'tcx>>,
 
     /// Where the data for this fragment can be found.
-    // NOTE(eddyb) There's an unenforced invariant that this `Place` is
-    // contains no indexing (with a non-constant index).
+    /// This `Place` only contains projection which satisfy `can_use_in_debuginfo`.
     pub contents: Place<'tcx>,
 }
 
@@ -1115,6 +1115,11 @@ pub struct VarDebugInfo<'tcx> {
 
     /// Where the data for this user variable is to be found.
     pub value: VarDebugInfoContents<'tcx>,
+
+    /// When present, indicates what argument number this variable is in the function that it
+    /// originated from (starting from 1). Note, if MIR inlining is enabled, then this is the
+    /// argument number in the original function before it was inlined.
+    pub argument_index: Option<u16>,
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -1274,9 +1279,16 @@ impl<'tcx> BasicBlockData<'tcx> {
 }
 
 impl<O> AssertKind<O> {
+    /// Returns true if this an overflow checking assertion controlled by -C overflow-checks.
+    pub fn is_optional_overflow_check(&self) -> bool {
+        use AssertKind::*;
+        use BinOp::*;
+        matches!(self, OverflowNeg(..) | Overflow(Add | Sub | Mul | Shl | Shr, ..))
+    }
+
     /// Getting a description does not require `O` to be printable, and does not
     /// require allocation.
-    /// The caller is expected to handle `BoundsCheck` separately.
+    /// The caller is expected to handle `BoundsCheck` and `MisalignedPointerDereference` separately.
     pub fn description(&self) -> &'static str {
         use AssertKind::*;
         match self {
@@ -1295,7 +1307,9 @@ impl<O> AssertKind<O> {
             ResumedAfterReturn(GeneratorKind::Async(_)) => "`async fn` resumed after completion",
             ResumedAfterPanic(GeneratorKind::Gen) => "generator resumed after panicking",
             ResumedAfterPanic(GeneratorKind::Async(_)) => "`async fn` resumed after panicking",
-            BoundsCheck { .. } => bug!("Unexpected AssertKind"),
+            BoundsCheck { .. } | MisalignedPointerDereference { .. } => {
+                bug!("Unexpected AssertKind")
+            }
         }
     }
 
@@ -1352,6 +1366,13 @@ impl<O> AssertKind<O> {
             Overflow(BinOp::Shl, _, r) => {
                 write!(f, "\"attempt to shift left by `{{}}`, which would overflow\", {:?}", r)
             }
+            MisalignedPointerDereference { required, found } => {
+                write!(
+                    f,
+                    "\"misaligned pointer dereference: address must be a multiple of {{}} but is {{}}\", {:?}, {:?}",
+                    required, found
+                )
+            }
             _ => write!(f, "\"{}\"", self.description()),
         }
     }
@@ -1396,6 +1417,13 @@ impl<O: fmt::Debug> fmt::Debug for AssertKind<O> {
             Overflow(BinOp::Shl, _, r) => {
                 write!(f, "attempt to shift left by `{:#?}`, which would overflow", r)
             }
+            MisalignedPointerDereference { required, found } => {
+                write!(
+                    f,
+                    "misaligned pointer dereference: address must be a multiple of {:?} but is {:?}",
+                    required, found
+                )
+            }
             _ => write!(f, "{}", self.description()),
         }
     }
@@ -1453,6 +1481,9 @@ impl Debug for Statement<'_> {
                 write!(fmt, "discriminant({:?}) = {:?}", place, variant_index)
             }
             Deinit(ref place) => write!(fmt, "Deinit({:?})", place),
+            PlaceMention(ref place) => {
+                write!(fmt, "PlaceMention({:?})", place)
+            }
             AscribeUserType(box (ref place, ref c_ty), ref variance) => {
                 write!(fmt, "AscribeUserType({:?}, {:?}, {:?})", place, variance, c_ty)
             }
@@ -1508,31 +1539,26 @@ impl<V, T> ProjectionElem<V, T> {
     }
 
     /// Returns `true` if this is a `Field` projection with the given index.
-    pub fn is_field_to(&self, f: Field) -> bool {
+    pub fn is_field_to(&self, f: FieldIdx) -> bool {
         matches!(*self, Self::Field(x, _) if x == f)
     }
+
+    /// Returns `true` if this is accepted inside `VarDebugInfoContents::Place`.
+    pub fn can_use_in_debuginfo(&self) -> bool {
+        match self {
+            Self::Deref | Self::Downcast(_, _) | Self::Field(_, _) => true,
+            Self::ConstantIndex { .. }
+            | Self::Index(_)
+            | Self::OpaqueCast(_)
+            | Self::Subslice { .. } => false,
+        }
+    }
 }
 
 /// Alias for projections as they appear in `UserTypeProjection`, where we
 /// need neither the `V` parameter for `Index` nor the `T` for `Field`.
 pub type ProjectionKind = ProjectionElem<(), ()>;
 
-rustc_index::newtype_index! {
-    /// A [newtype'd][wrapper] index type in the MIR [control-flow graph][CFG]
-    ///
-    /// A field (e.g., `f` in `_1.f`) is one variant of [`ProjectionElem`]. Conceptually,
-    /// rustc can identify that a field projection refers to either two different regions of memory
-    /// or the same one between the base and the 'projection element'.
-    /// Read more about projections in the [rustc-dev-guide][mir-datatypes]
-    ///
-    /// [wrapper]: https://rustc-dev-guide.rust-lang.org/appendix/glossary.html#newtype
-    /// [CFG]: https://rustc-dev-guide.rust-lang.org/appendix/background.html#cfg
-    /// [mir-datatypes]: https://rustc-dev-guide.rust-lang.org/mir/index.html#mir-data-types
-    #[derive(HashStable)]
-    #[debug_format = "field[{}]"]
-    pub struct Field {}
-}
-
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct PlaceRef<'tcx> {
     pub local: Local,
@@ -1775,7 +1801,7 @@ impl SourceScope {
     /// from the function that was inlined instead of the function call site.
     pub fn lint_root(
         self,
-        source_scopes: &IndexVec<SourceScope, SourceScopeData<'_>>,
+        source_scopes: &IndexSlice<SourceScope, SourceScopeData<'_>>,
     ) -> Option<HirId> {
         let mut data = &source_scopes[self];
         // FIXME(oli-obk): we should be able to just walk the `inlined_parent_scope`, but it
@@ -1795,7 +1821,7 @@ impl SourceScope {
     #[inline]
     pub fn inlined_instance<'tcx>(
         self,
-        source_scopes: &IndexVec<SourceScope, SourceScopeData<'tcx>>,
+        source_scopes: &IndexSlice<SourceScope, SourceScopeData<'tcx>>,
     ) -> Option<ty::Instance<'tcx>> {
         let scope_data = &source_scopes[self];
         if let Some((inlined_instance, _)) = scope_data.inlined {
@@ -1963,7 +1989,8 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::PtrToPtr
                 | CastKind::Pointer(_)
                 | CastKind::PointerFromExposedAddress
-                | CastKind::DynStar,
+                | CastKind::DynStar
+                | CastKind::Transmute,
                 _,
                 _,
             )
@@ -1979,6 +2006,13 @@ impl<'tcx> Rvalue<'tcx> {
 }
 
 impl BorrowKind {
+    pub fn mutability(&self) -> Mutability {
+        match *self {
+            BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => Mutability::Not,
+            BorrowKind::Mut { .. } => Mutability::Mut,
+        }
+    }
+
     pub fn allows_two_phase_borrow(&self) -> bool {
         match *self {
             BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
@@ -1995,13 +2029,6 @@ impl BorrowKind {
     }
 }
 
-impl BinOp {
-    pub fn is_checkable(self) -> bool {
-        use self::BinOp::*;
-        matches!(self, Add | Sub | Mul | Shl | Shr)
-    }
-}
-
 impl<'tcx> Debug for Rvalue<'tcx> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         use self::Rvalue::*;
@@ -2528,7 +2555,7 @@ impl<'tcx> ConstantKind<'tcx> {
         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())
+            InternalSubsts::identity_for_item(tcx, parent_did)
         } else {
             List::empty()
         };
@@ -2557,7 +2584,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 Self::Unevaluated(
                     UnevaluatedConst {
                         def: def.to_global(),
-                        substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
+                        substs: InternalSubsts::identity_for_item(tcx, def.did),
                         promoted: None,
                     },
                     ty,
@@ -2687,12 +2714,17 @@ impl<'tcx> UserTypeProjections {
         self.map_projections(|pat_ty_proj| pat_ty_proj.deref())
     }
 
-    pub fn leaf(self, field: Field) -> Self {
+    pub fn leaf(self, field: FieldIdx) -> Self {
         self.map_projections(|pat_ty_proj| pat_ty_proj.leaf(field))
     }
 
-    pub fn variant(self, adt_def: AdtDef<'tcx>, variant_index: VariantIdx, field: Field) -> Self {
-        self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field))
+    pub fn variant(
+        self,
+        adt_def: AdtDef<'tcx>,
+        variant_index: VariantIdx,
+        field_index: FieldIdx,
+    ) -> Self {
+        self.map_projections(|pat_ty_proj| pat_ty_proj.variant(adt_def, variant_index, field_index))
     }
 }
 
@@ -2735,7 +2767,7 @@ impl UserTypeProjection {
         self
     }
 
-    pub(crate) fn leaf(mut self, field: Field) -> Self {
+    pub(crate) fn leaf(mut self, field: FieldIdx) -> Self {
         self.projs.push(ProjectionElem::Field(field, ()));
         self
     }
@@ -2744,13 +2776,13 @@ impl UserTypeProjection {
         mut self,
         adt_def: AdtDef<'_>,
         variant_index: VariantIdx,
-        field: Field,
+        field_index: FieldIdx,
     ) -> Self {
         self.projs.push(ProjectionElem::Downcast(
             Some(adt_def.variant(variant_index).name),
             variant_index,
         ));
-        self.projs.push(ProjectionElem::Field(field, ()));
+        self.projs.push(ProjectionElem::Field(field_index, ()));
         self
     }
 }
@@ -3085,7 +3117,7 @@ mod size_asserts {
     use rustc_data_structures::static_assert_size;
     // tidy-alphabetical-start
     static_assert_size!(BasicBlockData<'_>, 144);
-    static_assert_size!(LocalDecl<'_>, 56);
+    static_assert_size!(LocalDecl<'_>, 40);
     static_assert_size!(Statement<'_>, 32);
     static_assert_size!(StatementKind<'_>, 16);
     static_assert_size!(Terminator<'_>, 112);
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 7a05ee2ff..f592f1515 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -381,7 +381,9 @@ impl<'tcx> CodegenUnit<'tcx> {
                             | InstanceDef::Virtual(..)
                             | InstanceDef::ClosureOnceShim { .. }
                             | InstanceDef::DropGlue(..)
-                            | InstanceDef::CloneShim(..) => None,
+                            | InstanceDef::CloneShim(..)
+                            | InstanceDef::ThreadLocalShim(..)
+                            | InstanceDef::FnPtrAddrShim(..) => None,
                         }
                     }
                     MonoItem::Static(def_id) => def_id.as_local().map(Idx::index),
diff --git a/compiler/rustc_middle/src/mir/patch.rs b/compiler/rustc_middle/src/mir/patch.rs
index 24fe3b472..f62853c3e 100644
--- a/compiler/rustc_middle/src/mir/patch.rs
+++ b/compiler/rustc_middle/src/mir/patch.rs
@@ -12,6 +12,9 @@ pub struct MirPatch<'tcx> {
     new_statements: Vec<(Location, StatementKind<'tcx>)>,
     new_locals: Vec<LocalDecl<'tcx>>,
     resume_block: Option<BasicBlock>,
+    // Only for unreachable in cleanup path.
+    unreachable_cleanup_block: Option<BasicBlock>,
+    terminate_block: Option<BasicBlock>,
     body_span: Span,
     next_local: usize,
 }
@@ -25,14 +28,31 @@ impl<'tcx> MirPatch<'tcx> {
             new_locals: vec![],
             next_local: body.local_decls.len(),
             resume_block: None,
+            unreachable_cleanup_block: None,
+            terminate_block: None,
             body_span: body.span,
         };
 
-        // Check if we already have a resume block
         for (bb, block) in body.basic_blocks.iter_enumerated() {
+            // Check if we already have a resume block
             if let TerminatorKind::Resume = block.terminator().kind && block.statements.is_empty() {
                 result.resume_block = Some(bb);
-                break;
+                continue;
+            }
+
+            // Check if we already have an unreachable block
+            if let TerminatorKind::Unreachable = block.terminator().kind
+                && block.statements.is_empty()
+                && block.is_cleanup
+            {
+                result.unreachable_cleanup_block = Some(bb);
+                continue;
+            }
+
+            // Check if we already have a terminate block
+            if let TerminatorKind::Terminate = block.terminator().kind && block.statements.is_empty() {
+                result.terminate_block = Some(bb);
+                continue;
             }
         }
 
@@ -56,6 +76,40 @@ impl<'tcx> MirPatch<'tcx> {
         bb
     }
 
+    pub fn unreachable_cleanup_block(&mut self) -> BasicBlock {
+        if let Some(bb) = self.unreachable_cleanup_block {
+            return bb;
+        }
+
+        let bb = self.new_block(BasicBlockData {
+            statements: vec![],
+            terminator: Some(Terminator {
+                source_info: SourceInfo::outermost(self.body_span),
+                kind: TerminatorKind::Unreachable,
+            }),
+            is_cleanup: true,
+        });
+        self.unreachable_cleanup_block = Some(bb);
+        bb
+    }
+
+    pub fn terminate_block(&mut self) -> BasicBlock {
+        if let Some(bb) = self.terminate_block {
+            return bb;
+        }
+
+        let bb = self.new_block(BasicBlockData {
+            statements: vec![],
+            terminator: Some(Terminator {
+                source_info: SourceInfo::outermost(self.body_span),
+                kind: TerminatorKind::Terminate,
+            }),
+            is_cleanup: true,
+        });
+        self.terminate_block = Some(bb);
+        bb
+    }
+
     pub fn is_patched(&self, bb: BasicBlock) -> bool {
         self.patch_map[bb].is_some()
     }
@@ -72,28 +126,28 @@ impl<'tcx> MirPatch<'tcx> {
         &mut self,
         ty: Ty<'tcx>,
         span: Span,
-        local_info: Option<Box<LocalInfo<'tcx>>>,
+        local_info: LocalInfo<'tcx>,
     ) -> Local {
         let index = self.next_local;
         self.next_local += 1;
         let mut new_decl = LocalDecl::new(ty, span).internal();
-        new_decl.local_info = local_info;
+        **new_decl.local_info.as_mut().assert_crate_local() = local_info;
         self.new_locals.push(new_decl);
-        Local::new(index as usize)
+        Local::new(index)
     }
 
     pub fn new_temp(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
         let index = self.next_local;
         self.next_local += 1;
         self.new_locals.push(LocalDecl::new(ty, span));
-        Local::new(index as usize)
+        Local::new(index)
     }
 
     pub fn new_internal(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
         let index = self.next_local;
         self.next_local += 1;
         self.new_locals.push(LocalDecl::new(ty, span).internal());
-        Local::new(index as usize)
+        Local::new(index)
     }
 
     pub fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index d8829e3e7..7e5195359 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -123,6 +123,7 @@ fn dump_matched_mir_node<'tcx, F>(
         // see notes on #41697 above
         let def_path =
             ty::print::with_forced_impl_filename_line!(tcx.def_path_str(body.source.def_id()));
+        // ignore-tidy-odd-backticks the literal below is fine
         write!(file, "// MIR for `{}", def_path)?;
         match body.source.promoted {
             None => write!(file, "`")?,
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index b964c1852..cfdf1dcf5 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -2,20 +2,20 @@
 
 use crate::mir::{Body, ConstantKind, Promoted};
 use crate::ty::{self, OpaqueHiddenType, Ty, TyCtxt};
-use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::vec_map::VecMap;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::unord::UnordSet;
 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::{Idx, IndexVec};
 use rustc_span::Span;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 use smallvec::SmallVec;
 use std::cell::Cell;
 use std::fmt::{self, Debug};
 
-use super::{Field, SourceInfo};
+use super::SourceInfo;
 
 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub enum UnsafetyViolationKind {
@@ -123,7 +123,7 @@ pub struct UnsafetyCheckResult {
     pub violations: Vec<UnsafetyViolation>,
 
     /// Used `unsafe` blocks in this function. This is used for the "unused_unsafe" lint.
-    pub used_unsafe_blocks: FxHashSet<hir::HirId>,
+    pub used_unsafe_blocks: UnordSet<hir::HirId>,
 
     /// This is `Some` iff the item is not a closure.
     pub unused_unsafes: Option<Vec<(hir::HirId, UnusedUnsafe)>>,
@@ -152,7 +152,7 @@ pub struct GeneratorLayout<'tcx> {
 
     /// Which of the above fields are in each variant. Note that one field may
     /// be stored in multiple variants.
-    pub variant_fields: IndexVec<VariantIdx, IndexVec<Field, GeneratorSavedLocal>>,
+    pub variant_fields: IndexVec<VariantIdx, IndexVec<FieldIdx, GeneratorSavedLocal>>,
 
     /// The source that led to each variant being created (usually, a yield or
     /// await).
@@ -227,9 +227,9 @@ pub struct BorrowCheckResult<'tcx> {
     /// All the opaque types that are restricted to concrete types
     /// by this function. Unlike the value in `TypeckResults`, this has
     /// unerased regions.
-    pub concrete_opaque_types: VecMap<LocalDefId, OpaqueHiddenType<'tcx>>,
+    pub concrete_opaque_types: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
-    pub used_mut_upvars: SmallVec<[Field; 8]>,
+    pub used_mut_upvars: SmallVec<[FieldIdx; 8]>,
     pub tainted_by_errors: Option<ErrorGuaranteed>,
 }
 
@@ -353,7 +353,7 @@ pub enum ConstraintCategory<'tcx> {
     /// like `Foo { field: my_val }`)
     Usage,
     OpaqueType,
-    ClosureUpvar(Field),
+    ClosureUpvar(FieldIdx),
 
     /// A constraint from a user-written predicate
     /// with the provided span, written on the item
@@ -375,7 +375,7 @@ pub enum ConstraintCategory<'tcx> {
 #[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
 pub enum ReturnConstraint {
     Normal,
-    ClosureUpvar(Field),
+    ClosureUpvar(FieldIdx),
 }
 
 /// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
@@ -411,10 +411,8 @@ impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
     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),
-                };
+                let br =
+                    ty::BoundRegion { var: ty::BoundVar::new(vid.index()), kind: ty::BrAnon(None) };
                 tcx.mk_re_late_bound(depth, br)
             }
             _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
diff --git a/compiler/rustc_middle/src/mir/spanview.rs b/compiler/rustc_middle/src/mir/spanview.rs
index 28a3b51b7..2165403da 100644
--- a/compiler/rustc_middle/src/mir/spanview.rs
+++ b/compiler/rustc_middle/src/mir/spanview.rs
@@ -247,6 +247,7 @@ pub fn statement_kind_name(statement: &Statement<'_>) -> &'static str {
         StorageLive(..) => "StorageLive",
         StorageDead(..) => "StorageDead",
         Retag(..) => "Retag",
+        PlaceMention(..) => "PlaceMention",
         AscribeUserType(..) => "AscribeUserType",
         Coverage(..) => "Coverage",
         Intrinsic(..) => "Intrinsic",
@@ -261,11 +262,10 @@ pub fn terminator_kind_name(term: &Terminator<'_>) -> &'static str {
         Goto { .. } => "Goto",
         SwitchInt { .. } => "SwitchInt",
         Resume => "Resume",
-        Abort => "Abort",
+        Terminate => "Terminate",
         Return => "Return",
         Unreachable => "Unreachable",
         Drop { .. } => "Drop",
-        DropAndReplace { .. } => "DropAndReplace",
         Call { .. } => "Call",
         Assert { .. } => "Assert",
         Yield { .. } => "Yield",
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index ae09562a8..93800d484 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -3,7 +3,7 @@
 //! This is in a dedicated file so that changes to this file can be reviewed more carefully.
 //! The intention is that this file only contains datatype declarations, no code.
 
-use super::{BasicBlock, Constant, Field, Local, SwitchTargets, UserTypeProjection};
+use super::{BasicBlock, Constant, Local, SwitchTargets, UserTypeProjection};
 
 use crate::mir::coverage::{CodeRegion, CoverageKind};
 use crate::traits::Reveal;
@@ -16,7 +16,8 @@ use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir};
 use rustc_hir::{self, GeneratorKind};
-use rustc_target::abi::VariantIdx;
+use rustc_index::vec::IndexVec;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 
 use rustc_ast::Mutability;
 use rustc_span::def_id::LocalDefId;
@@ -78,7 +79,8 @@ pub enum MirPhase {
     ///    MIR, this is UB.
     ///  - Retags: If `-Zmir-emit-retag` is enabled, analysis MIR has "implicit" retags in the same way
     ///    that Rust itself has them. Where exactly these are is generally subject to change, and so we
-    ///    don't document this here. Runtime MIR has all retags explicit.
+    ///    don't document this here. Runtime MIR has most retags explicit (though implicit retags
+    ///    can still occur at `Rvalue::{Ref,AddrOf}`).
     ///  - Generator bodies: In analysis MIR, locals may actually be behind a pointer that user code has
     ///    access to. This occurs in generator bodies. Such locals do not behave like other locals,
     ///    because they eg may be aliased in surprising ways. Runtime MIR has no such special locals -
@@ -133,7 +135,6 @@ pub enum AnalysisPhase {
 pub enum RuntimePhase {
     /// In addition to the semantic changes, beginning with this phase, the following variants are
     /// disallowed:
-    /// * [`TerminatorKind::DropAndReplace`]
     /// * [`TerminatorKind::Yield`]
     /// * [`TerminatorKind::GeneratorDrop`]
     /// * [`Rvalue::Aggregate`] for any `AggregateKind` except `Array`
@@ -219,6 +220,11 @@ pub enum BorrowKind {
     /// immutable, but not aliasable. This solves the problem. For
     /// simplicity, we don't give users the way to express this
     /// borrow, it's just used when translating closures.
+    ///
+    // FIXME(#112072): This is wrong. Unique borrows are mutable borrows except
+    // that they do not require their pointee to be marked as a mutable.
+    // They should still be treated as mutable borrows in every other way,
+    // e.g. for variance or overlap checking.
     Unique,
 
     /// Data is mutable and not aliasable.
@@ -326,6 +332,15 @@ pub enum StatementKind<'tcx> {
     /// Only `RetagKind::Default` and `RetagKind::FnEntry` are permitted.
     Retag(RetagKind, Box<Place<'tcx>>),
 
+    /// This statement exists to preserve a trace of a scrutinee matched against a wildcard binding.
+    /// This is especially useful for `let _ = PLACE;` bindings that desugar to a single
+    /// `PlaceMention(PLACE)`.
+    ///
+    /// When executed at runtime this is a nop.
+    ///
+    /// Disallowed after drop elaboration.
+    PlaceMention(Box<Place<'tcx>>),
+
     /// Encodes a user's type ascription. These need to be preserved
     /// intact so that NLL can respect them. For example:
     /// ```ignore (illustrative)
@@ -505,15 +520,15 @@ pub struct CopyNonOverlapping<'tcx> {
 ///
 /// A note on unwinding: Panics may occur during the execution of some terminators. Depending on the
 /// `-C panic` flag, this may either cause the program to abort or the call stack to unwind. Such
-/// terminators have a `cleanup: Option<BasicBlock>` field on them. If stack unwinding occurs, then
-/// once the current function is reached, execution continues at the given basic block, if any. If
-/// `cleanup` is `None` then no cleanup is performed, and the stack continues unwinding. This is
-/// equivalent to the execution of a `Resume` terminator.
+/// terminators have a `unwind: UnwindAction` field on them. If stack unwinding occurs, then
+/// once the current function is reached, an action will be taken based on the `unwind` field.
+/// If the action is `Cleanup`, then the execution continues at the given basic block. If the
+/// action is `Continue` then no cleanup is performed, and the stack continues unwinding.
 ///
-/// The basic block pointed to by a `cleanup` field must have its `cleanup` flag set. `cleanup`
-/// basic blocks have a couple restrictions:
-///  1. All `cleanup` fields in them must be `None`.
-///  2. `Return` terminators are not allowed in them. `Abort` and `Unwind` terminators are.
+/// The basic block pointed to by a `Cleanup` unwind action must have its `cleanup` flag set.
+/// `cleanup` basic blocks have a couple restrictions:
+///  1. All `unwind` fields in them must be `UnwindAction::Terminate` or `UnwindAction::Unreachable`.
+///  2. `Return` terminators are not allowed in them. `Terminate` and `Resume` terminators are.
 ///  3. All other basic blocks (in the current body) that are reachable from `cleanup` basic blocks
 ///     must also be `cleanup`. This is a part of the type system and checked statically, so it is
 ///     still an error to have such an edge in the CFG even if it's known that it won't be taken at
@@ -555,11 +570,11 @@ pub enum TerminatorKind<'tcx> {
     /// deaggregation runs.
     Resume,
 
-    /// Indicates that the landing pad is finished and that the process should abort.
+    /// Indicates that the landing pad is finished and that the process should terminate.
     ///
     /// Used to prevent unwinding for foreign items or with `-C unwind=abort`. Only permitted in
     /// cleanup blocks.
-    Abort,
+    Terminate,
 
     /// Returns from the function.
     ///
@@ -594,44 +609,7 @@ pub enum TerminatorKind<'tcx> {
     /// > The drop glue is executed if, among all statements executed within this `Body`, an assignment to
     /// > the place or one of its "parents" occurred more recently than a move out of it. This does not
     /// > consider indirect assignments.
-    Drop { place: Place<'tcx>, target: BasicBlock, unwind: Option<BasicBlock> },
-
-    /// Drops the place and assigns a new value to it.
-    ///
-    /// This first performs the exact same operation as the pre drop-elaboration `Drop` terminator;
-    /// it then additionally assigns the `value` to the `place` as if by an assignment statement.
-    /// This assignment occurs both in the unwind and the regular code paths. The semantics are best
-    /// explained by the elaboration:
-    ///
-    /// ```ignore (MIR)
-    /// BB0 {
-    ///   DropAndReplace(P <- V, goto BB1, unwind BB2)
-    /// }
-    /// ```
-    ///
-    /// becomes
-    ///
-    /// ```ignore (MIR)
-    /// BB0 {
-    ///   Drop(P, goto BB1, unwind BB2)
-    /// }
-    /// BB1 {
-    ///   // P is now uninitialized
-    ///   P <- V
-    /// }
-    /// BB2 {
-    ///   // P is now uninitialized -- its dtor panicked
-    ///   P <- V
-    /// }
-    /// ```
-    ///
-    /// Disallowed after drop elaboration.
-    DropAndReplace {
-        place: Place<'tcx>,
-        value: Operand<'tcx>,
-        target: BasicBlock,
-        unwind: Option<BasicBlock>,
-    },
+    Drop { place: Place<'tcx>, target: BasicBlock, unwind: UnwindAction },
 
     /// Roughly speaking, evaluates the `func` operand and the arguments, and starts execution of
     /// the referred to function. The operand types must match the argument types of the function.
@@ -655,8 +633,8 @@ pub enum TerminatorKind<'tcx> {
         destination: Place<'tcx>,
         /// Where to go after this call returns. If none, the call necessarily diverges.
         target: Option<BasicBlock>,
-        /// Cleanups to be done if the call unwinds.
-        cleanup: Option<BasicBlock>,
+        /// Action to be taken if the call unwinds.
+        unwind: UnwindAction,
         /// `true` if this is from a call in HIR rather than from an overloaded
         /// operator. True for overloaded function call.
         from_hir_call: bool,
@@ -675,14 +653,13 @@ pub enum TerminatorKind<'tcx> {
     /// 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).
+    /// - `Overflow(op, ..)` if op is add, sub, mul, shl, shr, but NOT div or rem.
     Assert {
         cond: Operand<'tcx>,
         expected: bool,
         msg: AssertMessage<'tcx>,
         target: BasicBlock,
-        cleanup: Option<BasicBlock>,
+        unwind: UnwindAction,
     },
 
     /// Marks a suspend point.
@@ -748,9 +725,8 @@ pub enum TerminatorKind<'tcx> {
         /// in practice, but in order to avoid fragility we want to always
         /// consider it in borrowck. We don't want to accept programs which
         /// pass borrowck only when `panic=abort` or some assertions are disabled
-        /// due to release vs. debug mode builds. This needs to be an `Option` because
-        /// of the `remove_noop_landing_pads` and `abort_unwinding_calls` passes.
-        unwind: Option<BasicBlock>,
+        /// due to release vs. debug mode builds.
+        unwind: UnwindAction,
     },
 
     /// Block ends with an inline assembly block. This is a terminator since
@@ -773,12 +749,31 @@ pub enum TerminatorKind<'tcx> {
         /// diverging (InlineAsmOptions::NORETURN).
         destination: Option<BasicBlock>,
 
-        /// Cleanup to be done if the inline assembly unwinds. This is present
+        /// Action to be taken if the inline assembly unwinds. This is present
         /// if and only if InlineAsmOptions::MAY_UNWIND is set.
-        cleanup: Option<BasicBlock>,
+        unwind: UnwindAction,
     },
 }
 
+/// Action to be taken when a stack unwind happens.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(TypeFoldable, TypeVisitable)]
+pub enum UnwindAction {
+    /// No action is to be taken. Continue unwinding.
+    ///
+    /// This is similar to `Cleanup(bb)` where `bb` does nothing but `Resume`, but they are not
+    /// equivalent, as presence of `Cleanup(_)` will make a frame non-POF.
+    Continue,
+    /// Triggers undefined behavior if unwind happens.
+    Unreachable,
+    /// Terminates the execution if unwind happens.
+    ///
+    /// Depending on the platform and situation this may cause a non-unwindable panic or abort.
+    Terminate,
+    /// Cleanups to be done.
+    Cleanup(BasicBlock),
+}
+
 /// Information about an assertion failure.
 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, TypeFoldable, TypeVisitable)]
 pub enum AssertKind<O> {
@@ -789,6 +784,7 @@ pub enum AssertKind<O> {
     RemainderByZero(O),
     ResumedAfterReturn(GeneratorKind),
     ResumedAfterPanic(GeneratorKind),
+    MisalignedPointerDereference { required: O, found: O },
 }
 
 #[derive(Clone, Debug, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
@@ -917,7 +913,15 @@ pub struct Place<'tcx> {
 #[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub enum ProjectionElem<V, T> {
     Deref,
-    Field(Field, T),
+
+    /// A field (e.g., `f` in `_1.f`) is one variant of [`ProjectionElem`]. Conceptually,
+    /// rustc can identify that a field projection refers to either two different regions of memory
+    /// or the same one between the base and the 'projection element'.
+    /// Read more about projections in the [rustc-dev-guide][mir-datatypes]
+    ///
+    /// [mir-datatypes]: https://rustc-dev-guide.rust-lang.org/mir/index.html#mir-data-types
+    Field(FieldIdx, T),
+
     /// Index into a slice/array.
     ///
     /// Note that this does not also dereference, and so it does not exactly correspond to slice
@@ -1110,11 +1114,7 @@ pub enum Rvalue<'tcx> {
     /// Same as `BinaryOp`, but yields `(T, bool)` with a `bool` indicating an error condition.
     ///
     /// For addition, subtraction, and multiplication on integers the error condition is set when
-    /// the infinite precision result would be unequal to the actual result.
-    ///
-    /// For shift operations on integers the error condition is set when the value of right-hand
-    /// side is greater than or equal to the number of bits in the type of the left-hand side, or
-    /// when the value of right-hand side is negative.
+    /// the infinite precision result would not be equal to the actual result.
     ///
     /// Other combinations of types and operators are unsupported.
     CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
@@ -1149,7 +1149,7 @@ pub enum Rvalue<'tcx> {
     ///
     /// Disallowed after deaggregation for all aggregate kinds except `Array` and `Generator`. After
     /// generator lowering, `Generator` aggregate kinds are disallowed too.
-    Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
+    Aggregate(Box<AggregateKind<'tcx>>, IndexVec<FieldIdx, Operand<'tcx>>),
 
     /// Transmutes a `*mut u8` into shallow-initialized `Box<T>`.
     ///
@@ -1189,6 +1189,13 @@ pub enum CastKind {
     IntToFloat,
     PtrToPtr,
     FnPtrToPtr,
+    /// Reinterpret the bits of the input as a different type.
+    ///
+    /// MIR is well-formed if the input and output types have different sizes,
+    /// but running a transmute between differently-sized types is UB.
+    ///
+    /// Allowed only in [`MirPhase::Runtime`]; Earlier it's a [`TerminatorKind::Call`].
+    Transmute,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
@@ -1199,11 +1206,11 @@ pub enum AggregateKind<'tcx> {
     Tuple,
 
     /// The second field is the variant index. It's equal to 0 for struct
-    /// and union expressions. The fourth field is
+    /// and union expressions. The last field is the
     /// active field number and is present only for union expressions
     /// -- e.g., for a union expression `SomeUnion { c: .. }`, the
     /// active field index would identity the field `c`
-    Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<usize>),
+    Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<FieldIdx>),
 
     Closure(DefId, SubstsRef<'tcx>),
     Generator(DefId, SubstsRef<'tcx>, hir::Movability),
@@ -1280,7 +1287,7 @@ pub enum BinOp {
 mod size_asserts {
     use super::*;
     // tidy-alphabetical-start
-    static_assert_size!(AggregateKind<'_>, 40);
+    static_assert_size!(AggregateKind<'_>, 32);
     static_assert_size!(Operand<'_>, 24);
     static_assert_size!(Place<'_>, 16);
     static_assert_size!(PlaceElem<'_>, 24);
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 0aa2c500f..4f00abf7f 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -6,7 +6,7 @@
 use crate::mir::*;
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir as hir;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 
 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
 pub struct PlaceTy<'tcx> {
@@ -33,7 +33,7 @@ impl<'tcx> PlaceTy<'tcx> {
     ///
     /// Note that the resulting type has not been normalized.
     #[instrument(level = "debug", skip(tcx), ret)]
-    pub fn field_ty(self, tcx: TyCtxt<'tcx>, f: Field) -> Ty<'tcx> {
+    pub fn field_ty(self, tcx: TyCtxt<'tcx>, f: FieldIdx) -> Ty<'tcx> {
         match self.ty.kind() {
             ty::Adt(adt_def, substs) => {
                 let variant_def = match self.variant_index {
@@ -43,7 +43,7 @@ impl<'tcx> PlaceTy<'tcx> {
                         &adt_def.variant(variant_index)
                     }
                 };
-                let field_def = &variant_def.fields[f.index()];
+                let field_def = &variant_def.fields[f];
                 field_def.ty(tcx, substs)
             }
             ty::Tuple(tys) => tys[f.index()],
@@ -61,14 +61,14 @@ impl<'tcx> PlaceTy<'tcx> {
     /// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
     /// projects `place_ty` onto `elem`, returning the appropriate
     /// `Ty` or downcast variant corresponding to that projection.
-    /// The `handle_field` callback must map a `Field` to its `Ty`,
+    /// The `handle_field` callback must map a `FieldIdx` to its `Ty`,
     /// (which should be trivial when `T` = `Ty`).
     pub fn projection_ty_core<V, T>(
         self,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         elem: &ProjectionElem<V, T>,
-        mut handle_field: impl FnMut(&Self, Field, T) -> Ty<'tcx>,
+        mut handle_field: impl FnMut(&Self, FieldIdx, T) -> Ty<'tcx>,
         mut handle_opaque_cast: impl FnMut(&Self, T) -> Ty<'tcx>,
     ) -> PlaceTy<'tcx>
     where
@@ -98,7 +98,7 @@ impl<'tcx> PlaceTy<'tcx> {
                     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_target_usize(tcx, param_env);
-                        let len = size - (from as u64) - (to as u64);
+                        let len = size - from - to;
                         tcx.mk_array(*inner, len)
                     }
                     _ => bug!("cannot subslice non-array type: `{:?}`", self),
@@ -116,7 +116,7 @@ impl<'tcx> PlaceTy<'tcx> {
 }
 
 impl<'tcx> Place<'tcx> {
-    pub fn ty_from<D>(
+    pub fn ty_from<D: ?Sized>(
         local: Local,
         projection: &[PlaceElem<'tcx>],
         local_decls: &D,
@@ -132,7 +132,7 @@ impl<'tcx> Place<'tcx> {
             })
     }
 
-    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
+    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
     where
         D: HasLocalDecls<'tcx>,
     {
@@ -141,7 +141,7 @@ impl<'tcx> Place<'tcx> {
 }
 
 impl<'tcx> PlaceRef<'tcx> {
-    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
+    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
     where
         D: HasLocalDecls<'tcx>,
     {
@@ -155,7 +155,7 @@ pub enum RvalueInitializationState {
 }
 
 impl<'tcx> Rvalue<'tcx> {
-    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
+    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
     where
         D: HasLocalDecls<'tcx>,
     {
@@ -164,17 +164,7 @@ impl<'tcx> Rvalue<'tcx> {
             Rvalue::Repeat(ref operand, count) => {
                 tcx.mk_array_with_const_len(operand.ty(local_decls, tcx), count)
             }
-            Rvalue::ThreadLocalRef(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) {
-                    tcx.mk_imm_ptr(static_ty)
-                } else {
-                    // FIXME: These things don't *really* have 'static lifetime.
-                    tcx.mk_imm_ref(tcx.lifetimes.re_static, static_ty)
-                }
-            }
+            Rvalue::ThreadLocalRef(did) => tcx.thread_local_ptr_ty(did),
             Rvalue::Ref(reg, bk, ref place) => {
                 let place_ty = place.ty(local_decls, tcx).ty;
                 tcx.mk_ref(reg, ty::TypeAndMut { ty: place_ty, mutbl: bk.to_mutbl_lossy() })
@@ -227,7 +217,7 @@ impl<'tcx> Rvalue<'tcx> {
 }
 
 impl<'tcx> Operand<'tcx> {
-    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
+    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
     where
         D: HasLocalDecls<'tcx>,
     {
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index 6e905224c..2c6126cdd 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -1,6 +1,6 @@
 use smallvec::SmallVec;
 
-use super::{BasicBlock, InlineAsmOperand, Operand, SourceInfo, TerminatorKind};
+use super::{BasicBlock, InlineAsmOperand, Operand, SourceInfo, TerminatorKind, UnwindAction};
 use rustc_ast::InlineAsmTemplatePiece;
 pub use rustc_ast::Mutability;
 use rustc_macros::HashStable;
@@ -118,11 +118,11 @@ impl<'tcx> Terminator<'tcx> {
         self.kind.successors_mut()
     }
 
-    pub fn unwind(&self) -> Option<&Option<BasicBlock>> {
+    pub fn unwind(&self) -> Option<&UnwindAction> {
         self.kind.unwind()
     }
 
-    pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> {
+    pub fn unwind_mut(&mut self) -> Option<&mut UnwindAction> {
         self.kind.unwind_mut()
     }
 }
@@ -135,35 +135,33 @@ impl<'tcx> TerminatorKind<'tcx> {
     pub fn successors(&self) -> Successors<'_> {
         use self::TerminatorKind::*;
         match *self {
-            Resume
-            | Abort
-            | GeneratorDrop
-            | Return
-            | Unreachable
-            | Call { target: None, cleanup: None, .. }
-            | InlineAsm { destination: None, cleanup: None, .. } => {
-                None.into_iter().chain((&[]).into_iter().copied())
+            Call { target: Some(t), unwind: UnwindAction::Cleanup(ref u), .. }
+            | Yield { resume: t, drop: Some(ref u), .. }
+            | Drop { target: t, unwind: UnwindAction::Cleanup(ref u), .. }
+            | Assert { target: t, unwind: UnwindAction::Cleanup(ref u), .. }
+            | FalseUnwind { real_target: t, unwind: UnwindAction::Cleanup(ref u) }
+            | InlineAsm { destination: Some(t), unwind: UnwindAction::Cleanup(ref u), .. } => {
+                Some(t).into_iter().chain(slice::from_ref(u).into_iter().copied())
             }
             Goto { target: t }
-            | Call { target: None, cleanup: Some(t), .. }
-            | Call { target: Some(t), cleanup: None, .. }
+            | Call { target: None, unwind: UnwindAction::Cleanup(t), .. }
+            | Call { target: Some(t), unwind: _, .. }
             | Yield { resume: t, drop: None, .. }
-            | DropAndReplace { target: t, unwind: None, .. }
-            | Drop { target: t, unwind: None, .. }
-            | Assert { target: t, cleanup: None, .. }
-            | FalseUnwind { real_target: t, unwind: None }
-            | InlineAsm { destination: Some(t), cleanup: None, .. }
-            | InlineAsm { destination: None, cleanup: Some(t), .. } => {
+            | Drop { target: t, unwind: _, .. }
+            | Assert { target: t, unwind: _, .. }
+            | FalseUnwind { real_target: t, unwind: _ }
+            | InlineAsm { destination: None, unwind: UnwindAction::Cleanup(t), .. }
+            | InlineAsm { destination: Some(t), unwind: _, .. } => {
                 Some(t).into_iter().chain((&[]).into_iter().copied())
             }
-            Call { target: Some(t), cleanup: Some(ref u), .. }
-            | Yield { resume: t, drop: Some(ref u), .. }
-            | DropAndReplace { target: t, unwind: Some(ref u), .. }
-            | Drop { target: t, unwind: Some(ref u), .. }
-            | Assert { target: t, cleanup: Some(ref u), .. }
-            | FalseUnwind { real_target: t, unwind: Some(ref u) }
-            | InlineAsm { destination: Some(t), cleanup: Some(ref u), .. } => {
-                Some(t).into_iter().chain(slice::from_ref(u).into_iter().copied())
+            Resume
+            | Terminate
+            | GeneratorDrop
+            | Return
+            | Unreachable
+            | Call { target: None, unwind: _, .. }
+            | InlineAsm { destination: None, unwind: _, .. } => {
+                None.into_iter().chain((&[]).into_iter().copied())
             }
             SwitchInt { ref targets, .. } => {
                 None.into_iter().chain(targets.targets.iter().copied())
@@ -177,34 +175,34 @@ impl<'tcx> TerminatorKind<'tcx> {
     pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
         use self::TerminatorKind::*;
         match *self {
-            Resume
-            | Abort
-            | GeneratorDrop
-            | Return
-            | Unreachable
-            | Call { target: None, cleanup: None, .. }
-            | InlineAsm { destination: None, cleanup: None, .. } => None.into_iter().chain(&mut []),
+            Call { target: Some(ref mut t), unwind: UnwindAction::Cleanup(ref mut u), .. }
+            | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
+            | Drop { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
+            | Assert { target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u), .. }
+            | FalseUnwind { real_target: ref mut t, unwind: UnwindAction::Cleanup(ref mut u) }
+            | InlineAsm {
+                destination: Some(ref mut t),
+                unwind: UnwindAction::Cleanup(ref mut u),
+                ..
+            } => Some(t).into_iter().chain(slice::from_mut(u)),
             Goto { target: ref mut t }
-            | Call { target: None, cleanup: Some(ref mut t), .. }
-            | Call { target: Some(ref mut t), cleanup: None, .. }
+            | Call { target: None, unwind: UnwindAction::Cleanup(ref mut t), .. }
+            | Call { target: Some(ref mut t), unwind: _, .. }
             | Yield { resume: ref mut t, drop: None, .. }
-            | DropAndReplace { target: ref mut t, unwind: None, .. }
-            | Drop { target: ref mut t, unwind: None, .. }
-            | Assert { target: ref mut t, cleanup: None, .. }
-            | FalseUnwind { real_target: ref mut t, unwind: None }
-            | InlineAsm { destination: Some(ref mut t), cleanup: None, .. }
-            | InlineAsm { destination: None, cleanup: Some(ref mut t), .. } => {
+            | Drop { target: ref mut t, unwind: _, .. }
+            | Assert { target: ref mut t, unwind: _, .. }
+            | FalseUnwind { real_target: ref mut t, unwind: _ }
+            | InlineAsm { destination: None, unwind: UnwindAction::Cleanup(ref mut t), .. }
+            | InlineAsm { destination: Some(ref mut t), unwind: _, .. } => {
                 Some(t).into_iter().chain(&mut [])
             }
-            Call { target: Some(ref mut t), cleanup: Some(ref mut u), .. }
-            | Yield { resume: ref mut t, drop: Some(ref mut u), .. }
-            | DropAndReplace { target: ref mut t, unwind: Some(ref mut u), .. }
-            | Drop { target: ref mut t, unwind: Some(ref mut u), .. }
-            | Assert { target: ref mut t, cleanup: Some(ref mut u), .. }
-            | FalseUnwind { real_target: ref mut t, unwind: Some(ref mut u) }
-            | InlineAsm { destination: Some(ref mut t), cleanup: Some(ref mut u), .. } => {
-                Some(t).into_iter().chain(slice::from_mut(u))
-            }
+            Resume
+            | Terminate
+            | GeneratorDrop
+            | Return
+            | Unreachable
+            | Call { target: None, unwind: _, .. }
+            | InlineAsm { destination: None, unwind: _, .. } => None.into_iter().chain(&mut []),
             SwitchInt { ref mut targets, .. } => None.into_iter().chain(&mut targets.targets),
             FalseEdge { ref mut real_target, ref mut imaginary_target } => {
                 Some(real_target).into_iter().chain(slice::from_mut(imaginary_target))
@@ -212,43 +210,41 @@ impl<'tcx> TerminatorKind<'tcx> {
         }
     }
 
-    pub fn unwind(&self) -> Option<&Option<BasicBlock>> {
+    pub fn unwind(&self) -> Option<&UnwindAction> {
         match *self {
             TerminatorKind::Goto { .. }
             | TerminatorKind::Resume
-            | TerminatorKind::Abort
+            | TerminatorKind::Terminate
             | TerminatorKind::Return
             | TerminatorKind::Unreachable
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::Yield { .. }
             | TerminatorKind::SwitchInt { .. }
             | TerminatorKind::FalseEdge { .. } => None,
-            TerminatorKind::Call { cleanup: ref unwind, .. }
-            | TerminatorKind::Assert { cleanup: ref unwind, .. }
-            | TerminatorKind::DropAndReplace { ref unwind, .. }
+            TerminatorKind::Call { ref unwind, .. }
+            | TerminatorKind::Assert { ref unwind, .. }
             | TerminatorKind::Drop { ref unwind, .. }
             | TerminatorKind::FalseUnwind { ref unwind, .. }
-            | TerminatorKind::InlineAsm { cleanup: ref unwind, .. } => Some(unwind),
+            | TerminatorKind::InlineAsm { ref unwind, .. } => Some(unwind),
         }
     }
 
-    pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> {
+    pub fn unwind_mut(&mut self) -> Option<&mut UnwindAction> {
         match *self {
             TerminatorKind::Goto { .. }
             | TerminatorKind::Resume
-            | TerminatorKind::Abort
+            | TerminatorKind::Terminate
             | TerminatorKind::Return
             | TerminatorKind::Unreachable
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::Yield { .. }
             | TerminatorKind::SwitchInt { .. }
             | TerminatorKind::FalseEdge { .. } => None,
-            TerminatorKind::Call { cleanup: ref mut unwind, .. }
-            | TerminatorKind::Assert { cleanup: ref mut unwind, .. }
-            | TerminatorKind::DropAndReplace { ref mut unwind, .. }
+            TerminatorKind::Call { ref mut unwind, .. }
+            | TerminatorKind::Assert { ref mut unwind, .. }
             | TerminatorKind::Drop { ref mut unwind, .. }
             | TerminatorKind::FalseUnwind { ref mut unwind, .. }
-            | TerminatorKind::InlineAsm { cleanup: ref mut unwind, .. } => Some(unwind),
+            | TerminatorKind::InlineAsm { ref mut unwind, .. } => Some(unwind),
         }
     }
 
@@ -274,11 +270,17 @@ impl<'tcx> Debug for TerminatorKind<'tcx> {
         let labels = self.fmt_successor_labels();
         assert_eq!(successor_count, labels.len());
 
-        match successor_count {
-            0 => Ok(()),
-
-            1 => write!(fmt, " -> {:?}", self.successors().next().unwrap()),
-
+        let unwind = match self.unwind() {
+            // Not needed or included in successors
+            None | Some(UnwindAction::Continue) | Some(UnwindAction::Cleanup(_)) => None,
+            Some(UnwindAction::Unreachable) => Some("unwind unreachable"),
+            Some(UnwindAction::Terminate) => Some("unwind terminate"),
+        };
+
+        match (successor_count, unwind) {
+            (0, None) => Ok(()),
+            (0, Some(unwind)) => write!(fmt, " -> {}", unwind),
+            (1, None) => write!(fmt, " -> {:?}", self.successors().next().unwrap()),
             _ => {
                 write!(fmt, " -> [")?;
                 for (i, target) in self.successors().enumerate() {
@@ -287,6 +289,9 @@ impl<'tcx> Debug for TerminatorKind<'tcx> {
                     }
                     write!(fmt, "{}: {:?}", labels[i], target)?;
                 }
+                if let Some(unwind) = unwind {
+                    write!(fmt, ", {unwind}")?;
+                }
                 write!(fmt, "]")
             }
         }
@@ -305,13 +310,10 @@ impl<'tcx> TerminatorKind<'tcx> {
             Return => write!(fmt, "return"),
             GeneratorDrop => write!(fmt, "generator_drop"),
             Resume => write!(fmt, "resume"),
-            Abort => write!(fmt, "abort"),
+            Terminate => write!(fmt, "abort"),
             Yield { value, resume_arg, .. } => write!(fmt, "{:?} = yield({:?})", resume_arg, value),
             Unreachable => write!(fmt, "unreachable"),
             Drop { place, .. } => write!(fmt, "drop({:?})", place),
-            DropAndReplace { place, value, .. } => {
-                write!(fmt, "replace({:?} <- {:?})", place, value)
-            }
             Call { func, args, destination, .. } => {
                 write!(fmt, "{:?} = ", destination)?;
                 write!(fmt, "{:?}(", func)?;
@@ -387,7 +389,7 @@ impl<'tcx> TerminatorKind<'tcx> {
     pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> {
         use self::TerminatorKind::*;
         match *self {
-            Return | Resume | Abort | Unreachable | GeneratorDrop => vec![],
+            Return | Resume | Terminate | Unreachable | GeneratorDrop => vec![],
             Goto { .. } => vec!["".into()],
             SwitchInt { ref targets, .. } => targets
                 .values
@@ -395,31 +397,35 @@ impl<'tcx> TerminatorKind<'tcx> {
                 .map(|&u| Cow::Owned(u.to_string()))
                 .chain(iter::once("otherwise".into()))
                 .collect(),
-            Call { target: Some(_), cleanup: Some(_), .. } => {
+            Call { target: Some(_), unwind: UnwindAction::Cleanup(_), .. } => {
                 vec!["return".into(), "unwind".into()]
             }
-            Call { target: Some(_), cleanup: None, .. } => vec!["return".into()],
-            Call { target: None, cleanup: Some(_), .. } => vec!["unwind".into()],
-            Call { target: None, cleanup: None, .. } => vec![],
+            Call { target: Some(_), unwind: _, .. } => vec!["return".into()],
+            Call { target: None, unwind: UnwindAction::Cleanup(_), .. } => vec!["unwind".into()],
+            Call { target: None, unwind: _, .. } => vec![],
             Yield { drop: Some(_), .. } => vec!["resume".into(), "drop".into()],
             Yield { drop: None, .. } => vec!["resume".into()],
-            DropAndReplace { unwind: None, .. } | Drop { unwind: None, .. } => {
-                vec!["return".into()]
-            }
-            DropAndReplace { unwind: Some(_), .. } | Drop { unwind: Some(_), .. } => {
-                vec!["return".into(), "unwind".into()]
+            Drop { unwind: UnwindAction::Cleanup(_), .. } => vec!["return".into(), "unwind".into()],
+            Drop { unwind: _, .. } => vec!["return".into()],
+            Assert { unwind: UnwindAction::Cleanup(_), .. } => {
+                vec!["success".into(), "unwind".into()]
             }
-            Assert { cleanup: None, .. } => vec!["".into()],
-            Assert { .. } => vec!["success".into(), "unwind".into()],
+            Assert { unwind: _, .. } => vec!["success".into()],
             FalseEdge { .. } => vec!["real".into(), "imaginary".into()],
-            FalseUnwind { unwind: Some(_), .. } => vec!["real".into(), "cleanup".into()],
-            FalseUnwind { unwind: None, .. } => vec!["real".into()],
-            InlineAsm { destination: Some(_), cleanup: Some(_), .. } => {
+            FalseUnwind { unwind: UnwindAction::Cleanup(_), .. } => {
+                vec!["real".into(), "unwind".into()]
+            }
+            FalseUnwind { unwind: _, .. } => vec!["real".into()],
+            InlineAsm { destination: Some(_), unwind: UnwindAction::Cleanup(_), .. } => {
                 vec!["return".into(), "unwind".into()]
             }
-            InlineAsm { destination: Some(_), cleanup: None, .. } => vec!["return".into()],
-            InlineAsm { destination: None, cleanup: Some(_), .. } => vec!["unwind".into()],
-            InlineAsm { destination: None, cleanup: None, .. } => vec![],
+            InlineAsm { destination: Some(_), unwind: _, .. } => {
+                vec!["return".into()]
+            }
+            InlineAsm { destination: None, unwind: UnwindAction::Cleanup(_), .. } => {
+                vec!["unwind".into()]
+            }
+            InlineAsm { destination: None, unwind: _, .. } => vec![],
         }
     }
 }
diff --git a/compiler/rustc_middle/src/mir/traversal.rs b/compiler/rustc_middle/src/mir/traversal.rs
index f37222cb2..7d247eeb6 100644
--- a/compiler/rustc_middle/src/mir/traversal.rs
+++ b/compiler/rustc_middle/src/mir/traversal.rs
@@ -101,7 +101,7 @@ impl<'a, 'tcx> Iterator for Preorder<'a, 'tcx> {
 ///
 /// A Postorder traversal of this graph is `D B C A` or `D C B A`
 pub struct Postorder<'a, 'tcx> {
-    basic_blocks: &'a IndexVec<BasicBlock, BasicBlockData<'tcx>>,
+    basic_blocks: &'a IndexSlice<BasicBlock, BasicBlockData<'tcx>>,
     visited: BitSet<BasicBlock>,
     visit_stack: Vec<(BasicBlock, Successors<'a>)>,
     root_is_start_block: bool,
@@ -109,7 +109,7 @@ pub struct Postorder<'a, 'tcx> {
 
 impl<'a, 'tcx> Postorder<'a, 'tcx> {
     pub fn new(
-        basic_blocks: &'a IndexVec<BasicBlock, BasicBlockData<'tcx>>,
+        basic_blocks: &'a IndexSlice<BasicBlock, BasicBlockData<'tcx>>,
         root: BasicBlock,
     ) -> Postorder<'a, 'tcx> {
         let mut po = Postorder {
@@ -178,17 +178,7 @@ impl<'a, 'tcx> Postorder<'a, 'tcx> {
         // When we yield `B` and call `traverse_successor`, we push `C` to the stack, but
         // since we've already visited `E`, that child isn't added to the stack. The last
         // two iterations yield `C` and finally `A` for a final traversal of [E, D, B, C, A]
-        loop {
-            let bb = if let Some(&mut (_, ref mut iter)) = self.visit_stack.last_mut() {
-                if let Some(bb) = iter.next() {
-                    bb
-                } else {
-                    break;
-                }
-            } else {
-                break;
-            };
-
+        while let Some(&mut (_, ref mut iter)) = self.visit_stack.last_mut() && let Some(bb) = iter.next() {
             if self.visited.insert(bb) {
                 if let Some(term) = &self.basic_blocks[bb].terminator {
                     self.visit_stack.push((bb, term.successors()));
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 5c056b299..caa5edc32 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -335,12 +335,14 @@ macro_rules! make_mir_visitor {
                         ty::InstanceDef::VTableShim(_def_id) |
                         ty::InstanceDef::ReifyShim(_def_id) |
                         ty::InstanceDef::Virtual(_def_id, _) |
+                        ty::InstanceDef::ThreadLocalShim(_def_id) |
                         ty::InstanceDef::ClosureOnceShim { call_once: _def_id, track_caller: _ } |
                         ty::InstanceDef::DropGlue(_def_id, None) => {}
 
                         ty::InstanceDef::FnPtrShim(_def_id, ty) |
                         ty::InstanceDef::DropGlue(_def_id, Some(ty)) |
-                        ty::InstanceDef::CloneShim(_def_id, ty) => {
+                        ty::InstanceDef::CloneShim(_def_id, ty) |
+                        ty::InstanceDef::FnPtrAddrShim(_def_id, ty) => {
                             // FIXME(eddyb) use a better `TyContext` here.
                             self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));
                         }
@@ -405,6 +407,13 @@ macro_rules! make_mir_visitor {
                     StatementKind::Retag(kind, place) => {
                         self.visit_retag($(& $mutability)? *kind, place, location);
                     }
+                    StatementKind::PlaceMention(place) => {
+                        self.visit_place(
+                            place,
+                            PlaceContext::NonUse(NonUseContext::PlaceMention),
+                            location
+                        );
+                    }
                     StatementKind::AscribeUserType(
                         box (place, user_ty),
                         variance
@@ -453,7 +462,7 @@ macro_rules! make_mir_visitor {
                 match kind {
                     TerminatorKind::Goto { .. } |
                     TerminatorKind::Resume |
-                    TerminatorKind::Abort |
+                    TerminatorKind::Terminate |
                     TerminatorKind::GeneratorDrop |
                     TerminatorKind::Unreachable |
                     TerminatorKind::FalseEdge { .. } |
@@ -495,26 +504,12 @@ macro_rules! make_mir_visitor {
                         );
                     }
 
-                    TerminatorKind::DropAndReplace {
-                        place,
-                        value,
-                        target: _,
-                        unwind: _,
-                    } => {
-                        self.visit_place(
-                            place,
-                            PlaceContext::MutatingUse(MutatingUseContext::Drop),
-                            location
-                        );
-                        self.visit_operand(value, location);
-                    }
-
                     TerminatorKind::Call {
                         func,
                         args,
                         destination,
                         target: _,
-                        cleanup: _,
+                        unwind: _,
                         from_hir_call: _,
                         fn_span: _
                     } => {
@@ -534,7 +529,7 @@ macro_rules! make_mir_visitor {
                         expected: _,
                         msg,
                         target: _,
-                        cleanup: _,
+                        unwind: _,
                     } => {
                         self.visit_operand(cond, location);
                         self.visit_assert_message(msg, location);
@@ -560,7 +555,7 @@ macro_rules! make_mir_visitor {
                         options: _,
                         line_spans: _,
                         destination: _,
-                        cleanup: _,
+                        unwind: _,
                     } => {
                         for op in operands {
                             match op {
@@ -615,6 +610,10 @@ macro_rules! make_mir_visitor {
                     ResumedAfterReturn(_) | ResumedAfterPanic(_) => {
                         // Nothing to visit
                     }
+                    MisalignedPointerDereference { required, found } => {
+                        self.visit_operand(required, location);
+                        self.visit_operand(found, location);
+                    }
                 }
             }
 
@@ -641,8 +640,8 @@ macro_rules! make_mir_visitor {
                             BorrowKind::Shallow => PlaceContext::NonMutatingUse(
                                 NonMutatingUseContext::ShallowBorrow
                             ),
-                            BorrowKind::Unique => PlaceContext::NonMutatingUse(
-                                NonMutatingUseContext::UniqueBorrow
+                            BorrowKind::Unique => PlaceContext::MutatingUse(
+                                MutatingUseContext::Borrow
                             ),
                             BorrowKind::Mut { .. } =>
                                 PlaceContext::MutatingUse(MutatingUseContext::Borrow),
@@ -811,7 +810,6 @@ macro_rules! make_mir_visitor {
                     source_info,
                     internal: _,
                     local_info: _,
-                    is_block_tail: _,
                 } = local_decl;
 
                 self.visit_ty($(& $mutability)? *ty, TyContext::LocalDecl {
@@ -834,6 +832,7 @@ macro_rules! make_mir_visitor {
                     name: _,
                     source_info,
                     value,
+                    argument_index: _,
                 } = var_debug_info;
 
                 self.visit_source_info(source_info);
@@ -1248,8 +1247,6 @@ pub enum NonMutatingUseContext {
     SharedBorrow,
     /// Shallow borrow.
     ShallowBorrow,
-    /// Unique borrow.
-    UniqueBorrow,
     /// AddressOf for *const pointer.
     AddressOf,
     /// Used as base for another place, e.g., `x` in `x.y`. Will not mutate the place.
@@ -1302,6 +1299,8 @@ pub enum NonUseContext {
     AscribeUserTy,
     /// The data of a user variable, for debug info.
     VarDebugInfo,
+    /// PlaceMention statement.
+    PlaceMention,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -1323,9 +1322,7 @@ impl PlaceContext {
         matches!(
             self,
             PlaceContext::NonMutatingUse(
-                NonMutatingUseContext::SharedBorrow
-                    | NonMutatingUseContext::ShallowBorrow
-                    | NonMutatingUseContext::UniqueBorrow
+                NonMutatingUseContext::SharedBorrow | NonMutatingUseContext::ShallowBorrow
             ) | PlaceContext::MutatingUse(MutatingUseContext::Borrow)
         )
     }
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
new file mode 100644
index 000000000..7d9aea022
--- /dev/null
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -0,0 +1,336 @@
+use crate::mir;
+use crate::traits;
+use crate::ty::{self, Ty};
+use std::mem::{size_of, transmute_copy, MaybeUninit};
+
+#[derive(Copy, Clone)]
+pub struct Erased<T: Copy> {
+    // We use `MaybeUninit` here so we can store any value
+    // in `data` since we aren't actually storing a `T`.
+    data: MaybeUninit<T>,
+}
+
+pub trait EraseType: Copy {
+    type Result: Copy;
+}
+
+// Allow `type_alias_bounds` since compilation will fail without `EraseType`.
+#[allow(type_alias_bounds)]
+pub type Erase<T: EraseType> = Erased<impl Copy>;
+
+#[inline(always)]
+pub fn erase<T: EraseType>(src: T) -> Erase<T> {
+    // Ensure the sizes match
+    const {
+        if std::mem::size_of::<T>() != std::mem::size_of::<T::Result>() {
+            panic!("size of T must match erased type T::Result")
+        }
+    };
+
+    Erased::<<T as EraseType>::Result> {
+        // SAFETY: Is it safe to transmute to MaybeUninit for types with the same sizes.
+        data: unsafe { transmute_copy(&src) },
+    }
+}
+
+/// Restores an erased value.
+#[inline(always)]
+pub fn restore<T: EraseType>(value: Erase<T>) -> T {
+    let value: Erased<<T as EraseType>::Result> = value;
+    // SAFETY: Due to the use of impl Trait in `Erase` the only way to safely create an instance
+    // of `Erase` is to call `erase`, so we know that `value.data` is a valid instance of `T` of
+    // the right size.
+    unsafe { transmute_copy(&value.data) }
+}
+
+impl<T> EraseType for &'_ T {
+    type Result = [u8; size_of::<*const ()>()];
+}
+
+impl<T> EraseType for &'_ [T] {
+    type Result = [u8; size_of::<*const [()]>()];
+}
+
+impl<T> EraseType for &'_ ty::List<T> {
+    type Result = [u8; size_of::<*const ()>()];
+}
+
+impl<T> EraseType for Result<&'_ T, traits::query::NoSolution> {
+    type Result = [u8; size_of::<Result<&'static (), traits::query::NoSolution>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, rustc_errors::ErrorGuaranteed> {
+    type Result = [u8; size_of::<Result<&'static (), rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, traits::CodegenObligationError> {
+    type Result = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, ty::layout::FnAbiError<'_>> {
+    type Result = [u8; size_of::<Result<&'static (), ty::layout::FnAbiError<'static>>>()];
+}
+
+impl<T> EraseType for Result<(&'_ T, rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed> {
+    type Result = [u8; size_of::<
+        Result<(&'static (), rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed>,
+    >()];
+}
+
+impl EraseType for Result<Option<ty::Instance<'_>>, rustc_errors::ErrorGuaranteed> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::Instance<'static>>, rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl EraseType for Result<Option<ty::Const<'_>>, rustc_errors::ErrorGuaranteed> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::Const<'static>>, rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl EraseType for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
+    type Result = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
+}
+
+impl EraseType for Result<bool, ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<Result<bool, ty::layout::LayoutError<'static>>>()];
+}
+
+impl EraseType for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<
+        Result<
+            rustc_target::abi::TyAndLayout<'static, Ty<'static>>,
+            ty::layout::LayoutError<'static>,
+        >,
+    >()];
+}
+
+impl EraseType for Result<ty::Const<'_>, mir::interpret::LitToConstError> {
+    type Result = [u8; size_of::<Result<ty::Const<'static>, mir::interpret::LitToConstError>>()];
+}
+
+impl EraseType for Result<mir::ConstantKind<'_>, mir::interpret::LitToConstError> {
+    type Result =
+        [u8; size_of::<Result<mir::ConstantKind<'static>, mir::interpret::LitToConstError>>()];
+}
+
+impl EraseType for Result<mir::interpret::ConstAlloc<'_>, mir::interpret::ErrorHandled> {
+    type Result = [u8; size_of::<
+        Result<mir::interpret::ConstAlloc<'static>, mir::interpret::ErrorHandled>,
+    >()];
+}
+
+impl EraseType for Result<mir::interpret::ConstValue<'_>, mir::interpret::ErrorHandled> {
+    type Result = [u8; size_of::<
+        Result<mir::interpret::ConstValue<'static>, mir::interpret::ErrorHandled>,
+    >()];
+}
+
+impl EraseType for Result<Option<ty::ValTree<'_>>, mir::interpret::ErrorHandled> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::ValTree<'static>>, mir::interpret::ErrorHandled>>()];
+}
+
+impl EraseType for Result<&'_ ty::List<Ty<'_>>, ty::util::AlwaysRequiresDrop> {
+    type Result =
+        [u8; size_of::<Result<&'static ty::List<Ty<'static>>, ty::util::AlwaysRequiresDrop>>()];
+}
+
+impl<T> EraseType for Option<&'_ T> {
+    type Result = [u8; size_of::<Option<&'static ()>>()];
+}
+
+impl<T> EraseType for Option<&'_ [T]> {
+    type Result = [u8; size_of::<Option<&'static [()]>>()];
+}
+
+impl EraseType for Option<rustc_middle::hir::Owner<'_>> {
+    type Result = [u8; size_of::<Option<rustc_middle::hir::Owner<'static>>>()];
+}
+
+impl EraseType for Option<mir::DestructuredConstant<'_>> {
+    type Result = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
+}
+
+impl EraseType for Option<ty::EarlyBinder<ty::TraitRef<'_>>> {
+    type Result = [u8; size_of::<Option<ty::EarlyBinder<ty::TraitRef<'static>>>>()];
+}
+
+impl EraseType for Option<ty::EarlyBinder<Ty<'_>>> {
+    type Result = [u8; size_of::<Option<ty::EarlyBinder<Ty<'static>>>>()];
+}
+
+impl<T> EraseType for rustc_hir::MaybeOwner<&'_ T> {
+    type Result = [u8; size_of::<rustc_hir::MaybeOwner<&'static ()>>()];
+}
+
+impl<T: EraseType> EraseType for ty::EarlyBinder<T> {
+    type Result = T::Result;
+}
+
+impl EraseType for ty::Binder<'_, ty::FnSig<'_>> {
+    type Result = [u8; size_of::<ty::Binder<'static, ty::FnSig<'static>>>()];
+}
+
+impl<T0, T1> EraseType for (&'_ T0, &'_ T1) {
+    type Result = [u8; size_of::<(&'static (), &'static ())>()];
+}
+
+impl<T0, T1> EraseType for (&'_ T0, &'_ [T1]) {
+    type Result = [u8; size_of::<(&'static (), &'static [()])>()];
+}
+
+macro_rules! trivial {
+    ($($ty:ty),+ $(,)?) => {
+        $(
+            impl EraseType for $ty {
+                type Result = [u8; size_of::<$ty>()];
+            }
+        )*
+    }
+}
+
+trivial! {
+    (),
+    bool,
+    Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
+    Option<rustc_ast::expand::allocator::AllocatorKind>,
+    Option<rustc_attr::ConstStability>,
+    Option<rustc_attr::DefaultBodyStability>,
+    Option<rustc_attr::Stability>,
+    Option<rustc_data_structures::svh::Svh>,
+    Option<rustc_hir::def::DefKind>,
+    Option<rustc_hir::GeneratorKind>,
+    Option<rustc_hir::HirId>,
+    Option<rustc_middle::middle::stability::DeprecationEntry>,
+    Option<rustc_middle::ty::Destructor>,
+    Option<rustc_middle::ty::ImplTraitInTraitData>,
+    Option<rustc_span::def_id::CrateNum>,
+    Option<rustc_span::def_id::DefId>,
+    Option<rustc_span::def_id::LocalDefId>,
+    Option<rustc_span::Span>,
+    Option<rustc_target::spec::PanicStrategy>,
+    Option<usize>,
+    Result<(), rustc_errors::ErrorGuaranteed>,
+    Result<(), rustc_middle::traits::query::NoSolution>,
+    Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
+    rustc_ast::expand::allocator::AllocatorKind,
+    rustc_attr::ConstStability,
+    rustc_attr::DefaultBodyStability,
+    rustc_attr::Deprecation,
+    rustc_attr::Stability,
+    rustc_data_structures::svh::Svh,
+    rustc_errors::ErrorGuaranteed,
+    rustc_hir::Constness,
+    rustc_hir::def_id::DefId,
+    rustc_hir::def_id::DefIndex,
+    rustc_hir::def_id::LocalDefId,
+    rustc_hir::def::DefKind,
+    rustc_hir::Defaultness,
+    rustc_hir::definitions::DefKey,
+    rustc_hir::GeneratorKind,
+    rustc_hir::HirId,
+    rustc_hir::IsAsync,
+    rustc_hir::ItemLocalId,
+    rustc_hir::LangItem,
+    rustc_hir::OwnerId,
+    rustc_hir::Upvar,
+    rustc_index::bit_set::FiniteBitSet<u32>,
+    rustc_middle::middle::dependency_format::Linkage,
+    rustc_middle::middle::exported_symbols::SymbolExportInfo,
+    rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault,
+    rustc_middle::middle::resolve_bound_vars::ResolvedArg,
+    rustc_middle::middle::stability::DeprecationEntry,
+    rustc_middle::mir::ConstQualifs,
+    rustc_middle::mir::interpret::AllocId,
+    rustc_middle::mir::interpret::ErrorHandled,
+    rustc_middle::mir::interpret::LitToConstError,
+    rustc_middle::thir::ExprId,
+    rustc_middle::traits::CodegenObligationError,
+    rustc_middle::traits::EvaluationResult,
+    rustc_middle::traits::OverflowError,
+    rustc_middle::traits::query::NoSolution,
+    rustc_middle::traits::WellFormedLoc,
+    rustc_middle::ty::adjustment::CoerceUnsizedInfo,
+    rustc_middle::ty::AssocItem,
+    rustc_middle::ty::AssocItemContainer,
+    rustc_middle::ty::BoundVariableKind,
+    rustc_middle::ty::DeducedParamAttrs,
+    rustc_middle::ty::Destructor,
+    rustc_middle::ty::fast_reject::SimplifiedType,
+    rustc_middle::ty::ImplPolarity,
+    rustc_middle::ty::Representability,
+    rustc_middle::ty::ReprOptions,
+    rustc_middle::ty::UnusedGenericParams,
+    rustc_middle::ty::util::AlwaysRequiresDrop,
+    rustc_middle::ty::Visibility<rustc_span::def_id::DefId>,
+    rustc_session::config::CrateType,
+    rustc_session::config::EntryFnType,
+    rustc_session::config::OptLevel,
+    rustc_session::config::SymbolManglingVersion,
+    rustc_session::cstore::CrateDepKind,
+    rustc_session::cstore::ExternCrate,
+    rustc_session::cstore::LinkagePreference,
+    rustc_session::Limits,
+    rustc_session::lint::LintExpectationId,
+    rustc_span::def_id::CrateNum,
+    rustc_span::def_id::DefPathHash,
+    rustc_span::ExpnHash,
+    rustc_span::ExpnId,
+    rustc_span::Span,
+    rustc_span::Symbol,
+    rustc_span::symbol::Ident,
+    rustc_target::spec::PanicStrategy,
+    rustc_type_ir::Variance,
+    u32,
+    usize,
+}
+
+macro_rules! tcx_lifetime {
+    ($($($fake_path:ident)::+),+ $(,)?) => {
+        $(
+            impl<'tcx> EraseType for $($fake_path)::+<'tcx> {
+                type Result = [u8; size_of::<$($fake_path)::+<'static>>()];
+            }
+        )*
+    }
+}
+
+tcx_lifetime! {
+    rustc_middle::hir::Owner,
+    rustc_middle::middle::exported_symbols::ExportedSymbol,
+    rustc_middle::mir::ConstantKind,
+    rustc_middle::mir::DestructuredConstant,
+    rustc_middle::mir::interpret::ConstAlloc,
+    rustc_middle::mir::interpret::ConstValue,
+    rustc_middle::mir::interpret::GlobalId,
+    rustc_middle::mir::interpret::LitToConstInput,
+    rustc_middle::traits::ChalkEnvironmentAndGoal,
+    rustc_middle::traits::query::MethodAutoderefStepsResult,
+    rustc_middle::traits::query::type_op::AscribeUserType,
+    rustc_middle::traits::query::type_op::Eq,
+    rustc_middle::traits::query::type_op::ProvePredicate,
+    rustc_middle::traits::query::type_op::Subtype,
+    rustc_middle::ty::AdtDef,
+    rustc_middle::ty::AliasTy,
+    rustc_middle::ty::Clause,
+    rustc_middle::ty::ClosureTypeInfo,
+    rustc_middle::ty::Const,
+    rustc_middle::ty::DestructuredConst,
+    rustc_middle::ty::ExistentialTraitRef,
+    rustc_middle::ty::FnSig,
+    rustc_middle::ty::GenericArg,
+    rustc_middle::ty::GenericPredicates,
+    rustc_middle::ty::inhabitedness::InhabitedPredicate,
+    rustc_middle::ty::Instance,
+    rustc_middle::ty::InstanceDef,
+    rustc_middle::ty::layout::FnAbiError,
+    rustc_middle::ty::layout::LayoutError,
+    rustc_middle::ty::ParamEnv,
+    rustc_middle::ty::Predicate,
+    rustc_middle::ty::SymbolName,
+    rustc_middle::ty::TraitRef,
+    rustc_middle::ty::Ty,
+    rustc_middle::ty::UnevaluatedConst,
+    rustc_middle::ty::ValTree,
+    rustc_middle::ty::VtblEntry,
+}
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index 78ee8a6a8..23b28ac5c 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -12,6 +12,11 @@ use rustc_hir::hir_id::{HirId, OwnerId};
 use rustc_query_system::query::{DefaultCacheSelector, SingleCacheSelector, VecCacheSelector};
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
+use rustc_target::abi::FieldIdx;
+
+/// Placeholder for `CrateNum`'s "local" counterpart
+#[derive(Copy, Clone, Debug)]
+pub struct LocalCrate;
 
 /// The `Key` trait controls what types can legally be used as the key
 /// for a query.
@@ -21,15 +26,11 @@ pub trait Key: Sized {
     //
     //      ...But r-a doesn't support them yet and using a default here causes r-a to not infer
     //      return types of queries which is very annoying. Thus, until r-a support associated
-    //      type defaults, plese restrain from using them here <3
+    //      type defaults, please restrain from using them here <3
     //
     //      r-a issue: <https://github.com/rust-lang/rust-analyzer/issues/13693>
     type CacheSelector;
 
-    /// Given an instance of this key, what crate is it referring to?
-    /// This is used to find the provider.
-    fn query_crate_is_local(&self) -> bool;
-
     /// In the event that a cycle occurs, if no explicit span has been
     /// given for a query with key `self`, what span should we use?
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span;
@@ -45,14 +46,17 @@ pub trait Key: Sized {
     }
 }
 
+pub trait AsLocalKey: Key {
+    type LocalKey;
+
+    /// Given an instance of this key, what crate is it referring to?
+    /// This is used to find the provider.
+    fn as_local_key(&self) -> Option<Self::LocalKey>;
+}
+
 impl Key for () {
     type CacheSelector = SingleCacheSelector;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -61,23 +65,22 @@ impl Key for () {
 impl<'tcx> Key for ty::InstanceDef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
     }
 }
 
-impl<'tcx> Key for ty::Instance<'tcx> {
-    type CacheSelector = DefaultCacheSelector<Self>;
+impl<'tcx> AsLocalKey for ty::InstanceDef<'tcx> {
+    type LocalKey = Self;
 
     #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        self.def_id().is_local().then(|| *self)
     }
+}
+
+impl<'tcx> Key for ty::Instance<'tcx> {
+    type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
@@ -87,11 +90,6 @@ impl<'tcx> Key for ty::Instance<'tcx> {
 impl<'tcx> Key for mir::interpret::GlobalId<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.instance.default_span(tcx)
     }
@@ -100,11 +98,6 @@ impl<'tcx> Key for mir::interpret::GlobalId<'tcx> {
 impl<'tcx> Key for (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -113,11 +106,6 @@ impl<'tcx> Key for (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>) {
 impl<'tcx> Key for mir::interpret::LitToConstInput<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -126,25 +114,27 @@ impl<'tcx> Key for mir::interpret::LitToConstInput<'tcx> {
 impl Key for CrateNum {
     type CacheSelector = VecCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        *self == LOCAL_CRATE
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
 }
 
-impl Key for OwnerId {
-    type CacheSelector = VecCacheSelector<Self>;
+impl AsLocalKey for CrateNum {
+    type LocalKey = LocalCrate;
 
     #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        (*self == LOCAL_CRATE).then_some(LocalCrate)
     }
+}
+
+impl Key for OwnerId {
+    type CacheSelector = VecCacheSelector<Self>;
+
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.to_def_id().default_span(tcx)
     }
+
     fn key_as_def_id(&self) -> Option<DefId> {
         Some(self.to_def_id())
     }
@@ -153,13 +143,10 @@ impl Key for OwnerId {
 impl Key for LocalDefId {
     type CacheSelector = VecCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.to_def_id().default_span(tcx)
     }
+
     fn key_as_def_id(&self) -> Option<DefId> {
         Some(self.to_def_id())
     }
@@ -168,26 +155,28 @@ impl Key for LocalDefId {
 impl Key for DefId {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(*self)
     }
+
     #[inline(always)]
     fn key_as_def_id(&self) -> Option<DefId> {
         Some(*self)
     }
 }
 
-impl Key for ty::WithOptConstParam<LocalDefId> {
-    type CacheSelector = DefaultCacheSelector<Self>;
+impl AsLocalKey for DefId {
+    type LocalKey = LocalDefId;
 
     #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        self.as_local()
     }
+}
+
+impl Key for ty::WithOptConstParam<LocalDefId> {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.did.default_span(tcx)
     }
@@ -196,10 +185,6 @@ impl Key for ty::WithOptConstParam<LocalDefId> {
 impl Key for SimplifiedType {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -208,10 +193,6 @@ impl Key for SimplifiedType {
 impl Key for (DefId, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
     }
@@ -220,10 +201,6 @@ impl Key for (DefId, DefId) {
 impl<'tcx> Key for (ty::Instance<'tcx>, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -232,10 +209,6 @@ impl<'tcx> Key for (ty::Instance<'tcx>, LocalDefId) {
 impl Key for (DefId, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
     }
@@ -244,10 +217,6 @@ impl Key for (DefId, LocalDefId) {
 impl Key for (LocalDefId, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -256,38 +225,27 @@ impl Key for (LocalDefId, DefId) {
 impl Key for (LocalDefId, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
 }
 
-impl Key for (DefId, Option<Ident>) {
+impl Key for (DefId, Ident) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.0)
     }
+
     #[inline(always)]
     fn key_as_def_id(&self) -> Option<DefId> {
         Some(self.0)
     }
 }
 
-impl Key for (DefId, LocalDefId, Ident) {
+impl Key for (LocalDefId, LocalDefId, Ident) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
     }
@@ -296,34 +254,40 @@ impl Key for (DefId, LocalDefId, Ident) {
 impl Key for (CrateNum, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0 == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
     }
 }
 
-impl Key for (CrateNum, SimplifiedType) {
-    type CacheSelector = DefaultCacheSelector<Self>;
+impl AsLocalKey for (CrateNum, DefId) {
+    type LocalKey = DefId;
 
     #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0 == LOCAL_CRATE
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        (self.0 == LOCAL_CRATE).then(|| self.1)
     }
+}
+
+impl Key for (CrateNum, SimplifiedType) {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
 }
 
-impl Key for (DefId, SimplifiedType) {
-    type CacheSelector = DefaultCacheSelector<Self>;
+impl AsLocalKey for (CrateNum, SimplifiedType) {
+    type LocalKey = SimplifiedType;
 
     #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        (self.0 == LOCAL_CRATE).then(|| self.1)
     }
+}
+
+impl Key for (DefId, SimplifiedType) {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -332,10 +296,6 @@ impl Key for (DefId, SimplifiedType) {
 impl<'tcx> Key for SubstsRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -344,10 +304,6 @@ impl<'tcx> Key for SubstsRef<'tcx> {
 impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -356,10 +312,6 @@ impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
 impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        (self.0).def.did.krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         (self.0).def.did.default_span(tcx)
     }
@@ -368,10 +320,6 @@ impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
 impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -380,22 +328,14 @@ impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
 impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.1.def_id().krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.1.def_id())
     }
 }
 
-impl<'tcx> Key for (ty::Const<'tcx>, mir::Field) {
+impl<'tcx> Key for (ty::Const<'tcx>, FieldIdx) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -404,10 +344,6 @@ impl<'tcx> Key for (ty::Const<'tcx>, mir::Field) {
 impl<'tcx> Key for mir::interpret::ConstAlloc<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -416,10 +352,6 @@ impl<'tcx> Key for mir::interpret::ConstAlloc<'tcx> {
 impl<'tcx> Key for ty::PolyTraitRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.def_id().krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
     }
@@ -428,10 +360,6 @@ impl<'tcx> Key for ty::PolyTraitRef<'tcx> {
 impl<'tcx> Key for ty::PolyExistentialTraitRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.def_id().krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
     }
@@ -440,10 +368,6 @@ impl<'tcx> Key for ty::PolyExistentialTraitRef<'tcx> {
 impl<'tcx> Key for (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.0.def_id().krate == LOCAL_CRATE
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.0.def_id())
     }
@@ -452,10 +376,6 @@ impl<'tcx> Key for (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>) {
 impl<'tcx> Key for GenericArg<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -464,10 +384,6 @@ impl<'tcx> Key for GenericArg<'tcx> {
 impl<'tcx> Key for mir::ConstantKind<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -476,10 +392,6 @@ impl<'tcx> Key for mir::ConstantKind<'tcx> {
 impl<'tcx> Key for ty::Const<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -488,13 +400,10 @@ impl<'tcx> Key for ty::Const<'tcx> {
 impl<'tcx> Key for Ty<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[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.kind() {
             ty::Adt(adt, _) => Some(adt.did()),
@@ -506,10 +415,6 @@ impl<'tcx> Key for Ty<'tcx> {
 impl<'tcx> Key for TyAndLayout<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -518,10 +423,6 @@ impl<'tcx> Key for TyAndLayout<'tcx> {
 impl<'tcx> Key for (Ty<'tcx>, Ty<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -530,10 +431,6 @@ impl<'tcx> Key for (Ty<'tcx>, Ty<'tcx>) {
 impl<'tcx> Key for &'tcx ty::List<ty::Predicate<'tcx>> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -542,10 +439,6 @@ impl<'tcx> Key for &'tcx ty::List<ty::Predicate<'tcx>> {
 impl<'tcx> Key for ty::ParamEnv<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -554,10 +447,6 @@ impl<'tcx> Key for ty::ParamEnv<'tcx> {
 impl<'tcx, T: Key> Key for ty::ParamEnvAnd<'tcx, T> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        self.value.query_crate_is_local()
-    }
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.value.default_span(tcx)
     }
@@ -566,10 +455,6 @@ impl<'tcx, T: Key> Key for ty::ParamEnvAnd<'tcx, T> {
 impl Key for Symbol {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -578,10 +463,6 @@ impl Key for Symbol {
 impl Key for Option<Symbol> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -589,14 +470,9 @@ impl Key for Option<Symbol> {
 
 /// Canonical query goals correspond to abstract trait operations that
 /// are not tied to any crate in particular.
-impl<'tcx, T> Key for Canonical<'tcx, T> {
+impl<'tcx, T: Clone> Key for Canonical<'tcx, T> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -605,11 +481,6 @@ impl<'tcx, T> Key for Canonical<'tcx, T> {
 impl Key for (Symbol, u32, u32) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -618,11 +489,6 @@ impl Key for (Symbol, u32, u32) {
 impl<'tcx> Key for (DefId, Ty<'tcx>, SubstsRef<'tcx>, ty::ParamEnv<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -631,11 +497,6 @@ impl<'tcx> Key for (DefId, Ty<'tcx>, SubstsRef<'tcx>, ty::ParamEnv<'tcx>) {
 impl<'tcx> Key for (ty::Predicate<'tcx>, traits::WellFormedLoc) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -644,11 +505,6 @@ impl<'tcx> Key for (ty::Predicate<'tcx>, traits::WellFormedLoc) {
 impl<'tcx> Key for (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -657,11 +513,6 @@ impl<'tcx> Key for (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
 impl<'tcx> Key for (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
     }
@@ -670,11 +521,6 @@ impl<'tcx> Key for (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
 impl<'tcx> Key for (Ty<'tcx>, ty::ValTree<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
@@ -683,11 +529,6 @@ impl<'tcx> Key for (Ty<'tcx>, ty::ValTree<'tcx>) {
 impl Key for HirId {
     type CacheSelector = DefaultCacheSelector<Self>;
 
-    #[inline(always)]
-    fn query_crate_is_local(&self) -> bool {
-        true
-    }
-
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.hir().span(*self)
     }
@@ -702,10 +543,6 @@ 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
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 5133da342..7a5a16035 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -7,8 +7,9 @@
 use crate::ty::{self, print::describe_as_module, TyCtxt};
 use rustc_span::def_id::LOCAL_CRATE;
 
+pub mod erase;
 mod keys;
-pub use keys::Key;
+pub use keys::{AsLocalKey, Key, LocalCrate};
 
 // Each of these queries corresponds to a function pointer field in the
 // `Providers` struct for requesting a value of that type, and a method
@@ -26,6 +27,15 @@ rustc_queries! {
         desc { "triggering a delay span bug" }
     }
 
+    query registered_tools(_: ()) -> &'tcx ty::RegisteredTools {
+        arena_cache
+        desc { "compute registered tools for crate" }
+    }
+
+    query early_lint_checks(_: ()) -> () {
+        desc { "perform lints prior to macro expansion" }
+    }
+
     query resolutions(_: ()) -> &'tcx ty::ResolverGlobalCtxt {
         feedable
         no_hash
@@ -87,7 +97,7 @@ rustc_queries! {
 
     /// Gives access to the HIR ID for the given `LocalDefId` owner `key` if any.
     ///
-    /// Definitions that were generated with no HIR, would be feeded to return `None`.
+    /// Definitions that were generated with no HIR, would be fed 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
@@ -182,6 +192,7 @@ rustc_queries! {
     {
         desc { "determine whether the opaque is a type-alias impl trait" }
         separate_provide_extern
+        feedable
     }
 
     query unsizing_params_for_adt(key: DefId) -> &'tcx rustc_index::bit_set::BitSet<u32>
@@ -616,20 +627,26 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    query implied_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
+        desc { |tcx| "computing the implied predicates of `{}`", tcx.def_path_str(key) }
+        cache_on_disk_if { key.is_local() }
+        separate_provide_extern
+    }
+
     /// The `Option<Ident>` is the name of an associated type. If it is `None`, then this query
     /// returns the full set of predicates. If `Some<Ident>`, then the query returns only the
     /// subset of super-predicates that reference traits that define the given associated type.
     /// This is used to avoid cycles in resolving types like `T::Item`.
-    query super_predicates_that_define_assoc_type(key: (DefId, Option<rustc_span::symbol::Ident>)) -> ty::GenericPredicates<'tcx> {
-        desc { |tcx| "computing the super traits of `{}`{}",
+    query super_predicates_that_define_assoc_type(key: (DefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
+        desc { |tcx| "computing the super traits of `{}` with associated type name `{}`",
             tcx.def_path_str(key.0),
-            if let Some(assoc_name) = key.1 { format!(" with associated type name `{}`", assoc_name) } else { "".to_string() },
+            key.1
         }
     }
 
     /// To avoid cycles within the predicates of a single item we compute
     /// per-type-parameter predicates for resolving `T::AssocTy`.
-    query type_param_predicates(key: (DefId, LocalDefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
+    query type_param_predicates(key: (LocalDefId, LocalDefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing the bounds for type parameter `{}`", tcx.hir().ty_param_name(key.1) }
     }
 
@@ -764,7 +781,7 @@ 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) -> &'tcx FxHashMap<DefId, DefId> {
+    query impl_item_implementor_ids(impl_id: DefId) -> &'tcx DefIdMap<DefId> {
         arena_cache
         desc { |tcx| "comparing impl items against trait for `{}`", tcx.def_path_str(impl_id) }
     }
@@ -775,7 +792,7 @@ rustc_queries! {
     /// 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] {
+    query associated_types_for_impl_traits_in_associated_fn(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
@@ -783,10 +800,9 @@ rustc_queries! {
 
     /// 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 {
+    query associated_type_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.
@@ -906,8 +922,8 @@ 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(_: ()) -> &'tcx (
-        FxHashSet<LocalDefId>,
-        FxHashMap<LocalDefId, Vec<(DefId, DefId)>>
+        LocalDefIdSet,
+        LocalDefIdMap<Vec<(DefId, DefId)>>
     ) {
         arena_cache
         desc { "finding live symbols in crate" }
@@ -1105,9 +1121,9 @@ rustc_queries! {
         desc { "converting literal to mir constant" }
     }
 
-    query check_match(key: DefId) {
-        desc { |tcx| "match-checking `{}`", tcx.def_path_str(key) }
-        cache_on_disk_if { key.is_local() }
+    query check_match(key: LocalDefId) {
+        desc { |tcx| "match-checking `{}`", tcx.def_path_str(key.to_def_id()) }
+        cache_on_disk_if { true }
     }
 
     /// Performs part of the privacy check and computes effective visibilities.
@@ -1120,7 +1136,7 @@ rustc_queries! {
         desc { "checking for private elements in public interfaces" }
     }
 
-    query reachable_set(_: ()) -> &'tcx FxHashSet<LocalDefId> {
+    query reachable_set(_: ()) -> &'tcx LocalDefIdSet {
         arena_cache
         desc { "reachability" }
     }
@@ -1152,14 +1168,6 @@ rustc_queries! {
         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.
     query def_span(def_id: DefId) -> Span {
         desc { |tcx| "looking up span for `{}`", tcx.def_path_str(def_id) }
@@ -1229,7 +1237,7 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query asm_target_features(def_id: DefId) -> &'tcx FxHashSet<Symbol> {
+    query asm_target_features(def_id: DefId) -> &'tcx FxIndexSet<Symbol> {
         desc { |tcx| "computing target features for inline asm of `{}`", tcx.def_path_str(def_id) }
     }
 
@@ -1324,6 +1332,7 @@ rustc_queries! {
     /// might want to use `reveal_all()` method to change modes.
     query param_env(def_id: DefId) -> ty::ParamEnv<'tcx> {
         desc { |tcx| "computing normalized predicates of `{}`", tcx.def_path_str(def_id) }
+        feedable
     }
 
     /// Like `param_env`, but returns the `ParamEnv` in `Reveal::All` mode.
@@ -1507,10 +1516,6 @@ rustc_queries! {
         desc { "getting traits in scope at a block" }
     }
 
-    query module_reexports(def_id: LocalDefId) -> Option<&'tcx [ModChild]> {
-        desc { |tcx| "looking up reexports of module `{}`", tcx.def_path_str(def_id.to_def_id()) }
-    }
-
     query impl_defaultness(def_id: DefId) -> hir::Defaultness {
         desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
@@ -1845,7 +1850,7 @@ rustc_queries! {
     query maybe_unused_trait_imports(_: ()) -> &'tcx FxIndexSet<LocalDefId> {
         desc { "fetching potentially unused trait imports" }
     }
-    query names_imported_by_glob_use(def_id: LocalDefId) -> &'tcx FxHashSet<Symbol> {
+    query names_imported_by_glob_use(def_id: LocalDefId) -> &'tcx UnordSet<Symbol> {
         desc { |tcx| "finding names imported by glob use for `{}`", tcx.def_path_str(def_id.to_def_id()) }
     }
 
@@ -2114,7 +2119,7 @@ rustc_queries! {
         desc { "raw operations for metadata file access" }
     }
 
-    query crate_for_resolver((): ()) -> &'tcx Steal<rustc_ast::ast::Crate> {
+    query crate_for_resolver((): ()) -> &'tcx Steal<(rustc_ast::Crate, rustc_ast::AttrVec)> {
         feedable
         no_hash
         desc { "the ast before macro expansion and name resolution" }
@@ -2213,7 +2218,7 @@ rustc_queries! {
     }
 
     /// 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
+    /// equal to eachother. This might return `Ok` even if the types are not equal, 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 3b11fab8c..7d79a13d3 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -17,14 +17,14 @@ use rustc_index::newtype_index;
 use rustc_index::vec::IndexVec;
 use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::AllocId;
-use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Field, Mutability, UnOp};
+use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::subst::SubstsRef;
 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};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use std::fmt;
 use std::ops::Index;
@@ -227,6 +227,9 @@ pub enum StmtKind<'tcx> {
 
         /// The lint level for this `let` statement.
         lint_level: LintLevel,
+
+        /// Span of the `let <PAT> = <INIT>` part.
+        span: Span,
     },
 }
 
@@ -366,7 +369,7 @@ pub enum ExprKind<'tcx> {
         /// Variant containing the field.
         variant_index: VariantIdx,
         /// This can be a named (`.foo`) or unnamed (`.0`) field.
-        name: Field,
+        name: FieldIdx,
     },
     /// A *non-overloaded* indexing operation.
     Index {
@@ -491,7 +494,7 @@ pub enum ExprKind<'tcx> {
 /// This is used in struct constructors.
 #[derive(Clone, Debug, HashStable)]
 pub struct FieldExpr {
-    pub name: Field,
+    pub name: FieldIdx,
     pub expr: ExprId,
 }
 
@@ -570,7 +573,7 @@ pub enum BindingMode {
 
 #[derive(Clone, Debug, HashStable)]
 pub struct FieldPat<'tcx> {
-    pub field: Field,
+    pub field: FieldIdx,
     pub pattern: Box<Pat<'tcx>>,
 }
 
@@ -594,6 +597,55 @@ impl<'tcx> Pat<'tcx> {
             _ => None,
         }
     }
+
+    /// Call `f` on every "binding" in a pattern, e.g., on `a` in
+    /// `match foo() { Some(a) => (), None => () }`
+    pub fn each_binding(&self, mut f: impl FnMut(Symbol, BindingMode, Ty<'tcx>, Span)) {
+        self.walk_always(|p| {
+            if let PatKind::Binding { name, mode, ty, .. } = p.kind {
+                f(name, mode, ty, p.span);
+            }
+        });
+    }
+
+    /// Walk the pattern in left-to-right order.
+    ///
+    /// If `it(pat)` returns `false`, the children are not visited.
+    pub fn walk(&self, mut it: impl FnMut(&Pat<'tcx>) -> bool) {
+        self.walk_(&mut it)
+    }
+
+    fn walk_(&self, it: &mut impl FnMut(&Pat<'tcx>) -> bool) {
+        if !it(self) {
+            return;
+        }
+
+        use PatKind::*;
+        match &self.kind {
+            Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } => {}
+            AscribeUserType { subpattern, .. }
+            | Binding { subpattern: Some(subpattern), .. }
+            | Deref { subpattern } => subpattern.walk_(it),
+            Leaf { subpatterns } | Variant { subpatterns, .. } => {
+                subpatterns.iter().for_each(|field| field.pattern.walk_(it))
+            }
+            Or { pats } => pats.iter().for_each(|p| p.walk_(it)),
+            Array { box ref prefix, ref slice, box ref suffix }
+            | Slice { box ref prefix, ref slice, box ref suffix } => {
+                prefix.iter().chain(slice.iter()).chain(suffix.iter()).for_each(|p| p.walk_(it))
+            }
+        }
+    }
+
+    /// Walk the pattern in left-to-right order.
+    ///
+    /// If you always want to recurse, prefer this method over `walk`.
+    pub fn walk_always(&self, mut it: impl FnMut(&Pat<'tcx>)) {
+        self.walk(|p| {
+            it(p);
+            true
+        })
+    }
 }
 
 impl<'tcx> IntoDiagnosticArg for Pat<'tcx> {
@@ -784,7 +836,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
                             if let PatKind::Wild = p.pattern.kind {
                                 continue;
                             }
-                            let name = variant.fields[p.field.index()].name;
+                            let name = variant.fields[p.field].name;
                             write!(f, "{}{}: {}", start_or_comma(), name, p.pattern)?;
                             printed += 1;
                         }
@@ -879,7 +931,7 @@ mod size_asserts {
     static_assert_size!(ExprKind<'_>, 40);
     static_assert_size!(Pat<'_>, 72);
     static_assert_size!(PatKind<'_>, 56);
-    static_assert_size!(Stmt<'_>, 48);
-    static_assert_size!(StmtKind<'_>, 40);
+    static_assert_size!(Stmt<'_>, 56);
+    static_assert_size!(StmtKind<'_>, 48);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index 79a0e75aa..5614528c4 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -175,6 +175,7 @@ pub fn walk_stmt<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, stmt: &Stm
             ref pattern,
             lint_level: _,
             else_block,
+            span: _,
         } => {
             if let Some(init) = initializer {
                 visitor.visit_expr(&visitor.thir()[*init]);
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 6231dd9b6..91f07389f 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -305,8 +305,6 @@ pub enum ObligationCauseCode<'tcx> {
     SizedReturnType,
     /// Yield type must be `Sized`.
     SizedYieldType,
-    /// Box expression result type must be `Sized`.
-    SizedBoxType,
     /// Inline asm operand type must be `Sized`.
     InlineAsmSized,
     /// `[expr; N]` requires `type_of(expr): Copy`.
@@ -699,9 +697,9 @@ impl<'tcx, N> ImplSource<'tcx, N> {
     }
 
     pub fn borrow_nested_obligations(&self) -> &[N] {
-        match &self {
-            ImplSource::UserDefined(i) => &i.nested[..],
-            ImplSource::Param(n, _) => &n,
+        match self {
+            ImplSource::UserDefined(i) => &i.nested,
+            ImplSource::Param(n, _) => n,
             ImplSource::Builtin(i) => &i.nested,
             ImplSource::AutoImpl(d) => &d.nested,
             ImplSource::Closure(c) => &c.nested,
@@ -715,6 +713,23 @@ impl<'tcx, N> ImplSource<'tcx, N> {
         }
     }
 
+    pub fn borrow_nested_obligations_mut(&mut self) -> &mut [N] {
+        match self {
+            ImplSource::UserDefined(i) => &mut i.nested,
+            ImplSource::Param(n, _) => n,
+            ImplSource::Builtin(i) => &mut i.nested,
+            ImplSource::AutoImpl(d) => &mut d.nested,
+            ImplSource::Closure(c) => &mut c.nested,
+            ImplSource::Generator(c) => &mut c.nested,
+            ImplSource::Future(c) => &mut c.nested,
+            ImplSource::Object(d) => &mut d.nested,
+            ImplSource::FnPointer(d) => &mut d.nested,
+            ImplSource::TraitAlias(d) => &mut d.nested,
+            ImplSource::TraitUpcasting(d) => &mut d.nested,
+            ImplSource::ConstDestruct(i) => &mut i.nested,
+        }
+    }
+
     pub fn map<M, F>(self, f: F) -> ImplSource<'tcx, M>
     where
         F: FnMut(N) -> M,
@@ -899,6 +914,9 @@ pub enum ObjectSafetyViolation {
     /// (e.g., `trait Foo : Bar<Self>`).
     SupertraitSelf(SmallVec<[Span; 1]>),
 
+    // Supertrait has a non-lifetime `for<T>` binder.
+    SupertraitNonLifetimeBinder(SmallVec<[Span; 1]>),
+
     /// Method has something illegal.
     Method(Symbol, MethodViolationCode, Span),
 
@@ -921,6 +939,9 @@ impl ObjectSafetyViolation {
                         .into()
                 }
             }
+            ObjectSafetyViolation::SupertraitNonLifetimeBinder(_) => {
+                "where clause cannot reference non-lifetime `for<...>` variables".into()
+            }
             ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => {
                 format!("associated function `{}` has no `self` parameter", name).into()
             }
@@ -971,7 +992,9 @@ impl ObjectSafetyViolation {
 
     pub fn solution(&self, err: &mut Diagnostic) {
         match self {
-            ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {}
+            ObjectSafetyViolation::SizedSelf(_)
+            | ObjectSafetyViolation::SupertraitSelf(_)
+            | ObjectSafetyViolation::SupertraitNonLifetimeBinder(..) => {}
             ObjectSafetyViolation::Method(
                 name,
                 MethodViolationCode::StaticMethod(Some((add_self_sugg, make_sized_sugg))),
@@ -1025,7 +1048,8 @@ impl ObjectSafetyViolation {
         // diagnostics use a `note` instead of a `span_label`.
         match self {
             ObjectSafetyViolation::SupertraitSelf(spans)
-            | ObjectSafetyViolation::SizedSelf(spans) => spans.clone(),
+            | ObjectSafetyViolation::SizedSelf(spans)
+            | ObjectSafetyViolation::SupertraitNonLifetimeBinder(spans) => spans.clone(),
             ObjectSafetyViolation::AssocConst(_, span)
             | ObjectSafetyViolation::GAT(_, span)
             | ObjectSafetyViolation::Method(_, _, span)
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
index bd43867a3..fef2be133 100644
--- a/compiler/rustc_middle/src/traits/solve.rs
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -1,12 +1,113 @@
 use std::ops::ControlFlow;
 
 use rustc_data_structures::intern::Interned;
+use rustc_query_system::cache::Cache;
 
-use crate::infer::canonical::QueryRegionConstraints;
+use crate::infer::canonical::{CanonicalVarValues, QueryRegionConstraints};
+use crate::traits::query::NoSolution;
+use crate::traits::Canonical;
 use crate::ty::{
-    FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
+    self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable,
+    TypeVisitor,
 };
 
+pub type EvaluationCache<'tcx> = Cache<CanonicalGoal<'tcx>, QueryResult<'tcx>>;
+
+/// A goal is a statement, i.e. `predicate`, we want to prove
+/// given some assumptions, i.e. `param_env`.
+///
+/// Most of the time the `param_env` contains the `where`-bounds of the function
+/// we're currently typechecking while the `predicate` is some trait bound.
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+pub struct Goal<'tcx, P> {
+    pub predicate: P,
+    pub param_env: ty::ParamEnv<'tcx>,
+}
+
+impl<'tcx, P> Goal<'tcx, P> {
+    pub fn new(
+        tcx: TyCtxt<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        predicate: impl ToPredicate<'tcx, P>,
+    ) -> Goal<'tcx, P> {
+        Goal { param_env, predicate: predicate.to_predicate(tcx) }
+    }
+
+    /// Updates the goal to one with a different `predicate` but the same `param_env`.
+    pub fn with<Q>(self, tcx: TyCtxt<'tcx>, predicate: impl ToPredicate<'tcx, Q>) -> Goal<'tcx, Q> {
+        Goal { param_env: self.param_env, predicate: predicate.to_predicate(tcx) }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+pub struct Response<'tcx> {
+    pub certainty: Certainty,
+    pub var_values: CanonicalVarValues<'tcx>,
+    /// Additional constraints returned by this query.
+    pub external_constraints: ExternalConstraints<'tcx>,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+pub enum Certainty {
+    Yes,
+    Maybe(MaybeCause),
+}
+
+impl Certainty {
+    pub const AMBIGUOUS: Certainty = Certainty::Maybe(MaybeCause::Ambiguity);
+
+    /// Use this function to merge the certainty of multiple nested subgoals.
+    ///
+    /// Given an impl like `impl<T: Foo + Bar> Baz for T {}`, we have 2 nested
+    /// subgoals whenever we use the impl as a candidate: `T: Foo` and `T: Bar`.
+    /// If evaluating `T: Foo` results in ambiguity and `T: Bar` results in
+    /// success, we merge these two responses. This results in ambiguity.
+    ///
+    /// If we unify ambiguity with overflow, we return overflow. This doesn't matter
+    /// inside of the solver as we distinguish ambiguity from overflow. It does
+    /// however matter for diagnostics. If `T: Foo` resulted in overflow and `T: Bar`
+    /// in ambiguity without changing the inference state, we still want to tell the
+    /// user that `T: Baz` results in overflow.
+    pub fn unify_with(self, other: Certainty) -> Certainty {
+        match (self, other) {
+            (Certainty::Yes, Certainty::Yes) => Certainty::Yes,
+            (Certainty::Yes, Certainty::Maybe(_)) => other,
+            (Certainty::Maybe(_), Certainty::Yes) => self,
+            (Certainty::Maybe(MaybeCause::Ambiguity), Certainty::Maybe(MaybeCause::Ambiguity)) => {
+                Certainty::Maybe(MaybeCause::Ambiguity)
+            }
+            (Certainty::Maybe(MaybeCause::Ambiguity), Certainty::Maybe(MaybeCause::Overflow))
+            | (Certainty::Maybe(MaybeCause::Overflow), Certainty::Maybe(MaybeCause::Ambiguity))
+            | (Certainty::Maybe(MaybeCause::Overflow), Certainty::Maybe(MaybeCause::Overflow)) => {
+                Certainty::Maybe(MaybeCause::Overflow)
+            }
+        }
+    }
+}
+
+/// Why we failed to evaluate a goal.
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+pub enum MaybeCause {
+    /// We failed due to ambiguity. This ambiguity can either
+    /// be a true ambiguity, i.e. there are multiple different answers,
+    /// or we hit a case where we just don't bother, e.g. `?x: Trait` goals.
+    Ambiguity,
+    /// We gave up due to an overflow, most often by hitting the recursion limit.
+    Overflow,
+}
+
+pub type CanonicalGoal<'tcx, T = ty::Predicate<'tcx>> = Canonical<'tcx, Goal<'tcx, T>>;
+
+pub type CanonicalResponse<'tcx> = Canonical<'tcx, Response<'tcx>>;
+
+/// The result of evaluating a canonical query.
+///
+/// FIXME: We use a different type than the existing canonical queries. This is because
+/// we need to add a `Certainty` for `overflow` and may want to restructure this code without
+/// having to worry about changes to currently used code. Once we've made progress on this
+/// solver, merge the two responses again.
+pub type QueryResult<'tcx> = Result<CanonicalResponse<'tcx>, NoSolution>;
+
 #[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
 pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
 
@@ -14,7 +115,7 @@ impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
     type Target = ExternalConstraintsData<'tcx>;
 
     fn deref(&self) -> &Self::Target {
-        &*self.0
+        &self.0
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index df9aa765d..468c2c818 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -37,10 +37,6 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
         self.tcx
     }
 
-    fn intercrate(&self) -> bool {
-        false
-    }
-
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
         self.param_env
     }
@@ -48,10 +44,6 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
         true
     } // irrelevant
 
-    fn mark_ambiguous(&mut self) {
-        bug!()
-    }
-
     fn relate_with_variance<T: Relate<'tcx>>(
         &mut self,
         _: ty::Variance,
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index 8ce06404d..cd0f7e8da 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -3,6 +3,7 @@ use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
 use rustc_macros::HashStable;
 use rustc_span::Span;
+use rustc_target::abi::FieldIdx;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 pub enum PointerCast {
@@ -208,5 +209,5 @@ pub struct CoerceUnsizedInfo {
 #[derive(Clone, Copy, TyEncodable, TyDecodable, Debug, HashStable)]
 pub enum CustomCoerceUnsized {
     /// Records the index of the field being coerced.
-    Struct(usize),
+    Struct(FieldIdx),
 }
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index ec21030b3..3a03c0901 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -10,11 +10,11 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::DataTypeKind;
 use rustc_span::symbol::sym;
-use rustc_target::abi::{ReprOptions, VariantIdx};
+use rustc_target::abi::{ReprOptions, VariantIdx, FIRST_VARIANT};
 
 use std::cell::RefCell;
 use std::cmp::Ordering;
@@ -168,7 +168,7 @@ impl<'tcx> AdtDef<'tcx> {
     }
 
     #[inline]
-    pub fn variants(self) -> &'tcx IndexVec<VariantIdx, VariantDef> {
+    pub fn variants(self) -> &'tcx IndexSlice<VariantIdx, VariantDef> {
         &self.0.0.variants
     }
 
@@ -228,7 +228,7 @@ impl AdtDefData {
             AdtKind::Struct => AdtFlags::IS_STRUCT,
         };
 
-        if kind == AdtKind::Struct && variants[VariantIdx::new(0)].ctor.is_some() {
+        if kind == AdtKind::Struct && variants[FIRST_VARIANT].ctor.is_some() {
             flags |= AdtFlags::HAS_CTOR;
         }
 
@@ -357,7 +357,7 @@ impl<'tcx> AdtDef<'tcx> {
     /// Asserts this is a struct or union and returns its unique variant.
     pub fn non_enum_variant(self) -> &'tcx VariantDef {
         assert!(self.is_struct() || self.is_union());
-        &self.variant(VariantIdx::new(0))
+        &self.variant(FIRST_VARIANT)
     }
 
     #[inline]
@@ -493,7 +493,7 @@ impl<'tcx> AdtDef<'tcx> {
 
     #[inline]
     pub fn variant_range(self) -> Range<VariantIdx> {
-        VariantIdx::new(0)..VariantIdx::new(self.variants().len())
+        FIRST_VARIANT..self.variants().next_index()
     }
 
     /// Computes the discriminant value used by a specific variant.
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index f1a9e50a4..090b76932 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -1,6 +1,6 @@
 pub use self::AssocItemContainer::*;
 
-use crate::ty::{self, DefIdTree};
+use crate::ty;
 use rustc_data_structures::sorted_map::SortedIndexMultiMap;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace};
@@ -30,6 +30,11 @@ pub struct AssocItem {
     /// Whether this is a method with an explicit self
     /// as its first parameter, allowing method calls.
     pub fn_has_self_parameter: bool,
+
+    /// `Some` if the associated item (an associated type) comes from the
+    /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
+    /// provides additional information about its source.
+    pub opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
 }
 
 impl AssocItem {
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index dc2bd54b7..f29bf92b0 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -158,12 +158,12 @@ impl<'tcx> CapturedPlace<'tcx> {
         for proj in self.place.projections.iter() {
             match proj.kind {
                 HirProjectionKind::Field(idx, variant) => match ty.kind() {
-                    ty::Tuple(_) => write!(&mut symbol, "__{}", idx).unwrap(),
+                    ty::Tuple(_) => write!(&mut symbol, "__{}", idx.index()).unwrap(),
                     ty::Adt(def, ..) => {
                         write!(
                             &mut symbol,
                             "__{}",
-                            def.variant(variant).fields[idx as usize].name.as_str(),
+                            def.variant(variant).fields[idx].name.as_str(),
                         )
                         .unwrap();
                     }
@@ -356,11 +356,11 @@ pub fn place_to_string_for_capture<'tcx>(tcx: TyCtxt<'tcx>, place: &HirPlace<'tc
                     curr_string = format!(
                         "{}.{}",
                         curr_string,
-                        def.variant(variant).fields[idx as usize].name.as_str()
+                        def.variant(variant).fields[idx].name.as_str()
                     );
                 }
                 ty::Tuple(_) => {
-                    curr_string = format!("{}.{}", curr_string, idx);
+                    curr_string = format!("{}.{}", curr_string, idx.index());
                 }
                 _ => {
                     bug!(
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 3ce80e06a..8ef4a46a7 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -511,8 +511,6 @@ macro_rules! implement_ty_decoder {
                     read_isize -> isize;
 
                     read_bool -> bool;
-                    read_f64 -> f64;
-                    read_f32 -> f32;
                     read_char -> char;
                     read_str -> &str;
                 }
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 527ec9f6e..bcedae233 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -1,10 +1,10 @@
 use crate::middle::resolve_bound_vars as rbv;
 use crate::mir::interpret::LitToConstInput;
-use crate::ty::{self, DefIdTree, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt};
+use crate::ty::{self, 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_hir::def_id::LocalDefId;
 use rustc_macros::HashStable;
 use std::fmt;
 
@@ -83,7 +83,7 @@ impl<'tcx> Const<'tcx> {
             None => tcx.mk_const(
                 ty::UnevaluatedConst {
                     def: def.to_global(),
-                    substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
+                    substs: InternalSubsts::identity_for_item(tcx, def.did),
                 },
                 ty,
             ),
@@ -135,6 +135,9 @@ impl<'tcx> Const<'tcx> {
                 _,
                 &hir::Path { res: Res::Def(DefKind::ConstParam, def_id), .. },
             )) => {
+                // Use the type from the param's definition, since we can resolve it,
+                // not the expected parameter type from WithOptConstParam.
+                let param_ty = tcx.type_of(def_id).subst_identity();
                 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
@@ -143,14 +146,14 @@ impl<'tcx> Const<'tcx> {
                         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(tcx.mk_const(ty::ParamConst::new(index, name), param_ty))
                     }
                     Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => Some(tcx.mk_const(
                         ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
-                        ty,
+                        param_ty,
                     )),
                     Some(rbv::ResolvedArg::Error(guar)) => {
-                        Some(tcx.const_error_with_guaranteed(ty, guar))
+                        Some(tcx.const_error_with_guaranteed(param_ty, guar))
                     }
                     arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
                 }
@@ -262,8 +265,8 @@ impl<'tcx> Const<'tcx> {
     }
 }
 
-pub fn const_param_default(tcx: TyCtxt<'_>, def_id: DefId) -> ty::EarlyBinder<Const<'_>> {
-    let default_def_id = match tcx.hir().get_by_def_id(def_id.expect_local()) {
+pub fn const_param_default(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Const<'_>> {
+    let default_def_id = match tcx.hir().get_by_def_id(def_id) {
         hir::Node::GenericParam(hir::GenericParam {
             kind: hir::GenericParamKind::Const { default: Some(ac), .. },
             ..
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index eecd78ab6..c0e557d48 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -237,7 +237,7 @@ impl ScalarInt {
     }
 
     /// Tries to convert the `ScalarInt` to an unsigned integer of the given size.
-    /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the
+    /// Fails if the size of the `ScalarInt` is not equal to `size` and returns the
     /// `ScalarInt`s size in that case.
     #[inline]
     pub fn try_to_uint(self, size: Size) -> Result<u128, Size> {
@@ -297,7 +297,7 @@ impl ScalarInt {
     }
 
     /// Tries to convert the `ScalarInt` to a signed integer of the given size.
-    /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the
+    /// Fails if the size of the `ScalarInt` is not equal to `size` and returns the
     /// `ScalarInt`s size in that case.
     #[inline]
     pub fn try_to_int(self, size: Size) -> Result<i128, Size> {
@@ -306,38 +306,38 @@ impl ScalarInt {
     }
 
     /// Tries to convert the `ScalarInt` to i8.
-    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 1 }`
+    /// Fails if the size of the `ScalarInt` is not equal to `Size { raw: 1 }`
     /// and returns the `ScalarInt`s size in that case.
     pub fn try_to_i8(self) -> Result<i8, Size> {
         self.try_to_int(Size::from_bits(8)).map(|v| i8::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to i16.
-    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 2 }`
+    /// Fails if the size of the `ScalarInt` is not equal to `Size { raw: 2 }`
     /// and returns the `ScalarInt`s size in that case.
     pub fn try_to_i16(self) -> Result<i16, Size> {
         self.try_to_int(Size::from_bits(16)).map(|v| i16::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to i32.
-    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 4 }`
+    /// Fails if the size of the `ScalarInt` is not equal to `Size { raw: 4 }`
     /// and returns the `ScalarInt`s size in that case.
     pub fn try_to_i32(self) -> Result<i32, Size> {
         self.try_to_int(Size::from_bits(32)).map(|v| i32::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to i64.
-    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 8 }`
+    /// Fails if the size of the `ScalarInt` is not equal to `Size { raw: 8 }`
     /// and returns the `ScalarInt`s size in that case.
     pub fn try_to_i64(self) -> Result<i64, Size> {
         self.try_to_int(Size::from_bits(64)).map(|v| i64::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to i128.
-    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 16 }`
+    /// Fails if the size of the `ScalarInt` is not equal to `Size { raw: 16 }`
     /// and returns the `ScalarInt`s size in that case.
     pub fn try_to_i128(self) -> Result<i128, Size> {
-        self.try_to_int(Size::from_bits(128)).map(|v| i128::try_from(v).unwrap())
+        self.try_to_int(Size::from_bits(128))
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/consts/valtree.rs b/compiler/rustc_middle/src/ty/consts/valtree.rs
index 5ed4af2e9..8b96864dd 100644
--- a/compiler/rustc_middle/src/ty/consts/valtree.rs
+++ b/compiler/rustc_middle/src/ty/consts/valtree.rs
@@ -79,7 +79,7 @@ impl<'tcx> ValTree<'tcx> {
     }
 
     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()
+        self.try_to_scalar_int().and_then(|s| s.try_to_target_usize(tcx).ok())
     }
 
     /// 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 d9af2fd74..63f7cc2ee 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -8,26 +8,26 @@ use crate::arena::Arena;
 use crate::dep_graph::{DepGraph, DepKindStruct};
 use crate::infer::canonical::CanonicalVarInfo;
 use crate::lint::struct_lint_level;
+use crate::metadata::ModChild;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
 use crate::middle::resolve_bound_vars;
 use crate::middle::stability;
 use crate::mir::interpret::{self, Allocation, ConstAllocation};
-use crate::mir::{
-    Body, BorrowCheckResult, Field, Local, Place, PlaceElem, ProjectionKind, Promoted,
-};
+use crate::mir::{Body, BorrowCheckResult, Local, Place, PlaceElem, ProjectionKind, Promoted};
+use crate::query::LocalCrate;
 use crate::thir::Thir;
 use crate::traits;
+use crate::traits::solve;
 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,
-    FloatVid, GenericParamDefKind, ImplPolarity, InferTy, IntTy, IntVar, IntVid, List, ParamConst,
-    ParamTy, PolyExistentialPredicate, PolyFnSig, Predicate, PredicateKind, Region, RegionKind,
-    ReprOptions, TraitObjectVisitor, Ty, TyKind, TyVar, TyVid, TypeAndMut, TypeckResults, UintTy,
-    Visibility,
+    self, AdtDef, AdtDefData, AdtKind, Binder, Const, ConstData, FloatTy, FloatVar, FloatVid,
+    GenericParamDefKind, ImplPolarity, InferTy, IntTy, IntVar, IntVid, List, ParamConst, ParamTy,
+    PolyExistentialPredicate, PolyFnSig, Predicate, PredicateKind, Region, RegionKind, ReprOptions,
+    TraitObjectVisitor, Ty, TyKind, TyVar, TyVid, TypeAndMut, TypeckResults, UintTy, Visibility,
 };
 use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
-use rustc_ast as ast;
+use rustc_ast::{self as ast, attr};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::intern::Interned;
@@ -37,6 +37,7 @@ 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, MappedReadGuard, ReadGuard, WorkerLocal};
+use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{
     DecorateLint, DiagnosticBuilder, DiagnosticMessage, ErrorGuaranteed, MultiSpan,
 };
@@ -63,13 +64,14 @@ use rustc_span::def_id::{DefPathHash, StableCrateId};
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::{Layout, LayoutS, TargetDataLayout, VariantIdx};
+use rustc_target::abi::{FieldIdx, Layout, LayoutS, TargetDataLayout, VariantIdx};
 use rustc_target::spec::abi;
 use rustc_type_ir::sty::TyKind::*;
 use rustc_type_ir::WithCachedTypeInfo;
 use rustc_type_ir::{CollectAndApply, DynKind, Interner, TypeFlags};
 
 use std::any::Any;
+use std::assert_matches::debug_assert_matches;
 use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::fmt;
@@ -310,7 +312,7 @@ pub struct CommonLifetimes<'tcx> {
     pub re_vars: Vec<Region<'tcx>>,
 
     /// Pre-interned values of the form:
-    /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(v, None) })`
+    /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(None) })`
     /// for small values of `i` and `v`.
     pub re_late_bounds: Vec<Vec<Region<'tcx>>>,
 }
@@ -385,10 +387,7 @@ impl<'tcx> CommonLifetimes<'tcx> {
                     .map(|v| {
                         mk(ty::ReLateBound(
                             ty::DebruijnIndex::from(i),
-                            ty::BoundRegion {
-                                var: ty::BoundVar::from(v),
-                                kind: ty::BrAnon(v, None),
-                            },
+                            ty::BoundRegion { var: ty::BoundVar::from(v), kind: ty::BrAnon(None) },
                         ))
                     })
                     .collect()
@@ -537,6 +536,9 @@ pub struct GlobalCtxt<'tcx> {
     /// Merge this with `selection_cache`?
     pub evaluation_cache: traits::EvaluationCache<'tcx>,
 
+    /// Caches the results of goal evaluation in the new solver.
+    pub new_solver_evaluation_cache: solve::EvaluationCache<'tcx>,
+
     /// Data layout specification for the current target.
     pub data_layout: TargetDataLayout,
 
@@ -712,6 +714,7 @@ impl<'tcx> TyCtxt<'tcx> {
             pred_rcache: Default::default(),
             selection_cache: Default::default(),
             evaluation_cache: Default::default(),
+            new_solver_evaluation_cache: Default::default(),
             data_layout,
             alloc_map: Lock::new(interpret::AllocMap::new()),
         }
@@ -922,7 +925,7 @@ impl<'tcx> TyCtxt<'tcx> {
             crate_name,
             // Don't print the whole stable crate id. That's just
             // annoying in debug output.
-            stable_crate_id.to_u64() >> 8 * 6,
+            stable_crate_id.to_u64() >> (8 * 6),
             self.def_path(def_id).to_string_no_crate_verbose()
         )
     }
@@ -2044,6 +2047,12 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_alias(self, kind: ty::AliasKind, alias_ty: ty::AliasTy<'tcx>) -> Ty<'tcx> {
+        debug_assert_matches!(
+            (kind, self.def_kind(alias_ty.def_id)),
+            (ty::Opaque, DefKind::OpaqueTy)
+                | (ty::Projection, DefKind::AssocTy)
+                | (ty::Opaque | ty::Projection, DefKind::ImplTraitPlaceholder)
+        );
         self.mk_ty_from_kind(Alias(kind, alias_ty))
     }
 
@@ -2064,10 +2073,9 @@ impl<'tcx> TyCtxt<'tcx> {
         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
+        if let ty::BoundRegion { var, kind: ty::BrAnon(None) } = bound_region
             && let Some(inner) = self.lifetimes.re_late_bounds.get(debruijn.as_usize())
-            && let Some(re) = inner.get(v as usize).copied()
+            && let Some(re) = inner.get(var.as_usize()).copied()
         {
             re
         } else {
@@ -2112,7 +2120,7 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    pub fn mk_place_field(self, place: Place<'tcx>, f: Field, ty: Ty<'tcx>) -> Place<'tcx> {
+    pub fn mk_place_field(self, place: Place<'tcx>, f: FieldIdx, ty: Ty<'tcx>) -> Place<'tcx> {
         self.mk_place_elem(place, PlaceElem::Field(f, ty))
     }
 
@@ -2372,7 +2380,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn in_scope_traits(self, id: HirId) -> Option<&'tcx [TraitCandidate]> {
         let map = self.in_scope_traits_map(id.owner)?;
         let candidates = map.get(&id.local_id)?;
-        Some(&*candidates)
+        Some(candidates)
     }
 
     pub fn named_bound_var(self, id: HirId) -> Option<resolve_bound_vars::ResolvedArg> {
@@ -2440,6 +2448,40 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn trait_solver_next(self) -> bool {
         self.sess.opts.unstable_opts.trait_solver == rustc_session::config::TraitSolver::Next
     }
+
+    pub fn lower_impl_trait_in_trait_to_assoc_ty(self) -> bool {
+        self.sess.opts.unstable_opts.lower_impl_trait_in_trait_to_assoc_ty
+    }
+
+    pub fn is_impl_trait_in_trait(self, def_id: DefId) -> bool {
+        if self.lower_impl_trait_in_trait_to_assoc_ty() {
+            self.opt_rpitit_info(def_id).is_some()
+        } else {
+            self.def_kind(def_id) == DefKind::ImplTraitPlaceholder
+        }
+    }
+
+    /// Named module children from all items except `use` and `extern crate` imports.
+    ///
+    /// In addition to regular items this list also includes struct or variant constructors, and
+    /// items inside `extern {}` blocks because all of them introduce names into parent module.
+    /// For non-reexported children every such name is associated with a separate `DefId`.
+    ///
+    /// Module here is understood in name resolution sense - it can be a `mod` item,
+    /// or a crate root, or an enum, or a trait.
+    pub fn module_children_non_reexports(self, def_id: LocalDefId) -> &'tcx [LocalDefId] {
+        self.resolutions(()).module_children_non_reexports.get(&def_id).map_or(&[], |v| &v[..])
+    }
+
+    /// Named module children from `use` and `extern crate` imports.
+    ///
+    /// Reexported names are not associated with individual `DefId`s,
+    /// e.g. a glob import can introduce a lot of names, all with the same `DefId`.
+    /// That's why the list needs to contain `ModChild` structures describing all the names
+    /// individually instead of `DefId`s.
+    pub fn module_children_reexports(self, def_id: LocalDefId) -> &'tcx [ModChild] {
+        self.resolutions(()).module_children_reexports.get(&def_id).map_or(&[], |v| &v[..])
+    }
 }
 
 impl<'tcx> TyCtxtAt<'tcx> {
@@ -2482,26 +2524,21 @@ pub struct DeducedParamAttrs {
 }
 
 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.names_imported_by_glob_use = |tcx, id| {
-        tcx.arena.alloc(tcx.resolutions(()).glob_map.get(&id).cloned().unwrap_or_default())
+        tcx.arena.alloc(UnordSet::from(
+            tcx.resolutions(()).glob_map.get(&id).cloned().unwrap_or_default(),
+        ))
     };
 
     providers.extern_mod_stmt_cnum =
         |tcx, id| tcx.resolutions(()).extern_crate_map.get(&id).cloned();
-    providers.is_panic_runtime = |tcx, cnum| {
-        assert_eq!(cnum, LOCAL_CRATE);
-        tcx.sess.contains_name(tcx.hir().krate_attrs(), sym::panic_runtime)
-    };
-    providers.is_compiler_builtins = |tcx, cnum| {
-        assert_eq!(cnum, LOCAL_CRATE);
-        tcx.sess.contains_name(tcx.hir().krate_attrs(), sym::compiler_builtins)
-    };
-    providers.has_panic_handler = |tcx, cnum| {
-        assert_eq!(cnum, LOCAL_CRATE);
+    providers.is_panic_runtime =
+        |tcx, LocalCrate| attr::contains_name(tcx.hir().krate_attrs(), sym::panic_runtime);
+    providers.is_compiler_builtins =
+        |tcx, LocalCrate| attr::contains_name(tcx.hir().krate_attrs(), sym::compiler_builtins);
+    providers.has_panic_handler = |tcx, LocalCrate| {
         // 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())
     };
diff --git a/compiler/rustc_middle/src/ty/context/tls.rs b/compiler/rustc_middle/src/ty/context/tls.rs
index 5426ac8d7..fb0d90930 100644
--- a/compiler/rustc_middle/src/ty/context/tls.rs
+++ b/compiler/rustc_middle/src/ty/context/tls.rs
@@ -4,6 +4,8 @@ use crate::dep_graph::TaskDepsRef;
 use crate::ty::query;
 use rustc_data_structures::sync::{self, Lock};
 use rustc_errors::Diagnostic;
+#[cfg(not(parallel_compiler))]
+use std::cell::Cell;
 use std::mem;
 use std::ptr;
 use thin_vec::ThinVec;
@@ -47,52 +49,15 @@ impl<'a, 'tcx> ImplicitCtxt<'a, 'tcx> {
     }
 }
 
+// Import the thread-local variable from Rayon, which is preserved for Rayon jobs.
 #[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)
-    }
-}
+use rayon_core::tlv::TLV;
 
+// Otherwise define our own
 #[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()
-    }
+thread_local! {
+    /// A thread local variable that stores a pointer to the current `ImplicitCtxt`.
+    static TLV: Cell<*const ()> = const { Cell::new(ptr::null()) };
 }
 
 #[inline]
@@ -111,7 +76,11 @@ pub fn enter_context<'a, 'tcx, F, R>(context: &ImplicitCtxt<'a, 'tcx>, f: F) ->
 where
     F: FnOnce() -> R,
 {
-    tlv::with_tlv(erase(context), f)
+    TLV.with(|tlv| {
+        let old = tlv.replace(erase(context));
+        let _reset = rustc_data_structures::OnDrop(move || tlv.set(old));
+        f()
+    })
 }
 
 /// Allows access to the current `ImplicitCtxt` in a closure if one is available.
@@ -120,7 +89,7 @@ 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();
+    let context = TLV.get();
     if context.is_null() {
         f(None)
     } else {
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index e894e1aaf..ae0bb4949 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -3,9 +3,9 @@
 use std::ops::ControlFlow;
 
 use crate::ty::{
-    AliasTy, Const, ConstKind, DefIdTree, FallibleTypeFolder, InferConst, InferTy, Opaque,
-    PolyTraitPredicate, Projection, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
-    TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    AliasTy, Const, ConstKind, FallibleTypeFolder, InferConst, InferTy, Opaque, PolyTraitPredicate,
+    Projection, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeSuperVisitable, TypeVisitable,
+    TypeVisitor,
 };
 
 use rustc_data_structures::fx::FxHashMap;
@@ -117,7 +117,7 @@ pub fn suggest_arbitrary_trait_bound<'tcx>(
     }
 
     let param_name = trait_pred.skip_binder().self_ty().to_string();
-    let mut constraint = trait_pred.print_modifiers_and_trait_path().to_string();
+    let mut constraint = trait_pred.to_string();
 
     if let Some((name, term)) = associated_ty {
         // FIXME: this case overlaps with code in TyCtxt::note_and_explain_type_err.
@@ -144,7 +144,7 @@ pub fn suggest_arbitrary_trait_bound<'tcx>(
              this requirement",
             if generics.where_clause_span.is_empty() { "introducing a" } else { "extending the" },
         ),
-        format!("{} {}: {}", generics.add_where_or_trailing_comma(), param_name, constraint),
+        format!("{} {constraint}", generics.add_where_or_trailing_comma()),
         Applicability::MaybeIncorrect,
     );
     true
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 9c171a69d..aff6c77e0 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -151,12 +151,8 @@ impl<'tcx> TypeError<'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);
-                }
+                let expected = values.expected.sort_string(tcx);
+                let found = values.found.sort_string(tcx);
                 report_maybe_different(&expected, &found).into()
             }
             Traits(values) => {
diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index 59deade0a..31d00b65e 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, TypeVisitableExt};
+use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeVisitableExt};
 use rustc_hir::def_id::DefId;
 use std::fmt::Debug;
 use std::hash::Hash;
@@ -51,15 +51,36 @@ pub enum SimplifiedType {
 /// generic parameters as if they were inference variables in that case.
 #[derive(PartialEq, Eq, Debug, Clone, Copy)]
 pub enum TreatParams {
-    /// Treat parameters as placeholders in the given environment.
+    /// Treat parameters as infer vars. This is the correct mode for caching
+    /// an impl's type for lookup.
+    AsCandidateKey,
+    /// Treat parameters as placeholders in the given environment. This is the
+    /// correct mode for *lookup*, as during candidate selection.
     ///
-    /// Note that this also causes us to treat projections as if they were
-    /// placeholders. This is only correct if the given projection cannot
-    /// be normalized in the current context. Even if normalization fails,
-    /// it may still succeed later if the projection contains any inference
-    /// variables.
-    AsPlaceholder,
-    AsInfer,
+    /// This also treats projections with inference variables as infer vars
+    /// since they could be further normalized.
+    ForLookup,
+    /// Treat parameters as placeholders in the given environment. This is the
+    /// correct mode for *lookup*, as during candidate selection.
+    ///
+    /// N.B. during deep rejection, this acts identically to `ForLookup`.
+    NextSolverLookup,
+}
+
+/// During fast-rejection, we have the choice of treating projection types
+/// as either simplifyable or not, depending on whether we expect the projection
+/// to be normalized/rigid.
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+pub enum TreatProjections {
+    /// In the old solver we don't try to normalize projections
+    /// when looking up impls and only access them by using the
+    /// current self type. This means that if the self type is
+    /// a projection which could later be normalized, we must not
+    /// treat it as rigid.
+    ForLookup,
+    /// We can treat projections in the self type as opaque as
+    /// we separately look up impls for the normalized self type.
+    NextSolverLookup,
 }
 
 /// Tries to simplify a type by only returning the outermost injective¹ layer, if one exists.
@@ -115,19 +136,20 @@ pub fn simplify_type<'tcx>(
         ty::FnPtr(f) => Some(FunctionSimplifiedType(f.skip_binder().inputs().len())),
         ty::Placeholder(..) => Some(PlaceholderSimplifiedType),
         ty::Param(_) => match treat_params {
-            TreatParams::AsPlaceholder => Some(PlaceholderSimplifiedType),
-            TreatParams::AsInfer => None,
+            TreatParams::ForLookup | TreatParams::NextSolverLookup => {
+                Some(PlaceholderSimplifiedType)
+            }
+            TreatParams::AsCandidateKey => None,
         },
         ty::Alias(..) => match treat_params {
             // When treating `ty::Param` as a placeholder, projections also
             // don't unify with anything else as long as they are fully normalized.
             //
             // We will have to be careful with lazy normalization here.
-            TreatParams::AsPlaceholder if !ty.has_non_region_infer() => {
-                debug!("treating `{}` as a placeholder", ty);
-                Some(PlaceholderSimplifiedType)
-            }
-            TreatParams::AsPlaceholder | TreatParams::AsInfer => None,
+            // FIXME(lazy_normalization): This is probably not right...
+            TreatParams::ForLookup if !ty.has_non_region_infer() => Some(PlaceholderSimplifiedType),
+            TreatParams::NextSolverLookup => Some(PlaceholderSimplifiedType),
+            TreatParams::ForLookup | TreatParams::AsCandidateKey => None,
         },
         ty::Foreign(def_id) => Some(ForeignSimplifiedType(def_id)),
         ty::Bound(..) | ty::Infer(_) | ty::Error(_) => None,
@@ -166,22 +188,24 @@ pub struct DeepRejectCtxt {
 }
 
 impl DeepRejectCtxt {
-    pub fn generic_args_may_unify<'tcx>(
+    pub fn substs_refs_may_unify<'tcx>(
         self,
-        obligation_arg: ty::GenericArg<'tcx>,
-        impl_arg: ty::GenericArg<'tcx>,
+        obligation_substs: SubstsRef<'tcx>,
+        impl_substs: SubstsRef<'tcx>,
     ) -> bool {
-        match (obligation_arg.unpack(), impl_arg.unpack()) {
-            // We don't fast reject based on regions for now.
-            (GenericArgKind::Lifetime(_), GenericArgKind::Lifetime(_)) => true,
-            (GenericArgKind::Type(obl), GenericArgKind::Type(imp)) => {
-                self.types_may_unify(obl, imp)
-            }
-            (GenericArgKind::Const(obl), GenericArgKind::Const(imp)) => {
-                self.consts_may_unify(obl, imp)
+        iter::zip(obligation_substs, impl_substs).all(|(obl, imp)| {
+            match (obl.unpack(), imp.unpack()) {
+                // We don't fast reject based on regions for now.
+                (GenericArgKind::Lifetime(_), GenericArgKind::Lifetime(_)) => true,
+                (GenericArgKind::Type(obl), GenericArgKind::Type(imp)) => {
+                    self.types_may_unify(obl, imp)
+                }
+                (GenericArgKind::Const(obl), GenericArgKind::Const(imp)) => {
+                    self.consts_may_unify(obl, imp)
+                }
+                _ => bug!("kind mismatch: {obl} {imp}"),
             }
-            _ => bug!("kind mismatch: {obligation_arg} {impl_arg}"),
-        }
+        })
     }
 
     pub fn types_may_unify<'tcx>(self, obligation_ty: Ty<'tcx>, impl_ty: Ty<'tcx>) -> bool {
@@ -236,9 +260,7 @@ impl DeepRejectCtxt {
             },
             ty::Adt(obl_def, obl_substs) => match k {
                 &ty::Adt(impl_def, impl_substs) => {
-                    obl_def == impl_def
-                        && iter::zip(obl_substs, impl_substs)
-                            .all(|(obl, imp)| self.generic_args_may_unify(obl, imp))
+                    obl_def == impl_def && self.substs_refs_may_unify(obl_substs, impl_substs)
                 }
                 _ => false,
             },
@@ -290,15 +312,20 @@ impl DeepRejectCtxt {
             // Impls cannot contain these types as these cannot be named directly.
             ty::FnDef(..) | ty::Closure(..) | ty::Generator(..) => false,
 
+            // Placeholder types don't unify with anything on their own
             ty::Placeholder(..) | ty::Bound(..) => false,
 
             // Depending on the value of `treat_obligation_params`, we either
             // treat generic parameters like placeholders or like inference variables.
             ty::Param(_) => match self.treat_obligation_params {
-                TreatParams::AsPlaceholder => false,
-                TreatParams::AsInfer => true,
+                TreatParams::ForLookup | TreatParams::NextSolverLookup => false,
+                TreatParams::AsCandidateKey => true,
             },
 
+            ty::Infer(ty::IntVar(_)) => impl_ty.is_integral(),
+
+            ty::Infer(ty::FloatVar(_)) => impl_ty.is_floating_point(),
+
             ty::Infer(_) => true,
 
             // As we're walking the whole type, it may encounter projections
@@ -333,10 +360,13 @@ impl DeepRejectCtxt {
         let k = impl_ct.kind();
         match obligation_ct.kind() {
             ty::ConstKind::Param(_) => match self.treat_obligation_params {
-                TreatParams::AsPlaceholder => false,
-                TreatParams::AsInfer => true,
+                TreatParams::ForLookup | TreatParams::NextSolverLookup => false,
+                TreatParams::AsCandidateKey => true,
             },
 
+            // Placeholder consts don't unify with anything on their own
+            ty::ConstKind::Placeholder(_) => false,
+
             // As we don't necessarily eagerly evaluate constants,
             // they might unify with any value.
             ty::ConstKind::Expr(_) | ty::ConstKind::Unevaluated(_) | ty::ConstKind::Error(_) => {
@@ -349,7 +379,7 @@ impl DeepRejectCtxt {
 
             ty::ConstKind::Infer(_) => true,
 
-            ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
+            ty::ConstKind::Bound(..) => {
                 bug!("unexpected obl const: {:?}", obligation_ct)
             }
         }
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index 91241ff40..5a6ee1238 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -288,7 +288,7 @@ impl FlagComputation {
                 self.add_ty(ty);
             }
             ty::PredicateKind::Ambiguous => {}
-            ty::PredicateKind::AliasEq(t1, t2) => {
+            ty::PredicateKind::AliasRelate(t1, t2, _) => {
                 self.add_term(t1);
                 self.add_term(t2);
             }
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index d66f436f9..203e16bea 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -51,9 +51,7 @@ where
 // Region folder
 
 impl<'tcx> TyCtxt<'tcx> {
-    /// Folds the escaping and free regions in `value` using `f`, and
-    /// sets `skipped_regions` to true if any late-bound region was found
-    /// and skipped.
+    /// Folds the escaping and free regions in `value` using `f`.
     pub fn fold_regions<T>(
         self,
         value: T,
@@ -64,17 +62,6 @@ impl<'tcx> TyCtxt<'tcx> {
     {
         value.fold_with(&mut RegionFolder::new(self, &mut f))
     }
-
-    pub fn super_fold_regions<T>(
-        self,
-        value: T,
-        mut f: impl FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>,
-    ) -> T
-    where
-        T: TypeSuperFoldable<TyCtxt<'tcx>>,
-    {
-        value.super_fold_with(&mut RegionFolder::new(self, &mut f))
-    }
 }
 
 /// Folds over the substructure of a type, visiting its component
@@ -392,9 +379,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| {
-                        ty::BoundVariableKind::Region(ty::BrAnon(index as u32, None))
-                    })
+                    .or_insert_with(|| ty::BoundVariableKind::Region(ty::BrAnon(None)))
                     .expect_region();
                 let br = ty::BoundRegion { var, kind };
                 self.tcx.mk_re_late_bound(ty::INNERMOST, br)
@@ -404,9 +389,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| {
-                        ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon(index as u32))
-                    })
+                    .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon))
                     .expect_ty();
                 self.tcx.mk_bound(ty::INNERMOST, BoundTy { var, kind })
             }
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
index e268553f8..ac42d6e05 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
@@ -1,5 +1,5 @@
 use crate::ty::context::TyCtxt;
-use crate::ty::{self, DefId, DefIdTree, ParamEnv, Ty};
+use crate::ty::{self, DefId, ParamEnv, Ty};
 
 /// Represents whether some type is inhabited in a given context.
 /// Examples of uninhabited types are `!`, `enum Void {}`, or a struct
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index f4028a5a9..e73225f70 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -82,6 +82,11 @@ pub enum InstanceDef<'tcx> {
     /// The `DefId` is the ID of the `call_once` method in `FnOnce`.
     ClosureOnceShim { call_once: DefId, track_caller: bool },
 
+    /// Compiler-generated accessor for thread locals which returns a reference to the thread local
+    /// the `DefId` defines. This is used to export thread locals from dylibs on platforms lacking
+    /// native support.
+    ThreadLocalShim(DefId),
+
     /// `core::ptr::drop_in_place::<T>`.
     ///
     /// The `DefId` is for `core::ptr::drop_in_place`.
@@ -96,6 +101,13 @@ pub enum InstanceDef<'tcx> {
     ///
     /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
     CloneShim(DefId, Ty<'tcx>),
+
+    /// Compiler-generated `<T as FnPtr>::addr` implementation.
+    ///
+    /// Automatically generated for all potentially higher-ranked `fn(I) -> R` types.
+    ///
+    /// The `DefId` is for `FnPtr::addr`, the `Ty` is the type `T`.
+    FnPtrAddrShim(DefId, Ty<'tcx>),
 }
 
 impl<'tcx> Instance<'tcx> {
@@ -149,9 +161,11 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::FnPtrShim(def_id, _)
             | InstanceDef::Virtual(def_id, _)
             | InstanceDef::Intrinsic(def_id)
+            | InstanceDef::ThreadLocalShim(def_id)
             | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
             | InstanceDef::DropGlue(def_id, _)
-            | InstanceDef::CloneShim(def_id, _) => def_id,
+            | InstanceDef::CloneShim(def_id, _)
+            | InstanceDef::FnPtrAddrShim(def_id, _) => def_id,
         }
     }
 
@@ -159,7 +173,9 @@ impl<'tcx> InstanceDef<'tcx> {
     pub fn def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId> {
         match self {
             ty::InstanceDef::Item(def) => Some(def.did),
-            ty::InstanceDef::DropGlue(def_id, Some(_)) => Some(def_id),
+            ty::InstanceDef::DropGlue(def_id, Some(_)) | InstanceDef::ThreadLocalShim(def_id) => {
+                Some(def_id)
+            }
             InstanceDef::VTableShim(..)
             | InstanceDef::ReifyShim(..)
             | InstanceDef::FnPtrShim(..)
@@ -167,7 +183,8 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::Intrinsic(..)
             | InstanceDef::ClosureOnceShim { .. }
             | InstanceDef::DropGlue(..)
-            | InstanceDef::CloneShim(..) => None,
+            | InstanceDef::CloneShim(..)
+            | InstanceDef::FnPtrAddrShim(..) => None,
         }
     }
 
@@ -182,12 +199,18 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::Intrinsic(def_id)
             | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
             | InstanceDef::DropGlue(def_id, _)
-            | InstanceDef::CloneShim(def_id, _) => ty::WithOptConstParam::unknown(def_id),
+            | InstanceDef::CloneShim(def_id, _)
+            | InstanceDef::ThreadLocalShim(def_id)
+            | InstanceDef::FnPtrAddrShim(def_id, _) => ty::WithOptConstParam::unknown(def_id),
         }
     }
 
     #[inline]
-    pub fn get_attrs(&self, tcx: TyCtxt<'tcx>, attr: Symbol) -> ty::Attributes<'tcx> {
+    pub fn get_attrs(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        attr: Symbol,
+    ) -> impl Iterator<Item = &'tcx rustc_ast::Attribute> {
         tcx.get_attrs(self.def_id(), attr)
     }
 
@@ -201,6 +224,7 @@ impl<'tcx> InstanceDef<'tcx> {
         let def_id = match *self {
             ty::InstanceDef::Item(def) => def.did,
             ty::InstanceDef::DropGlue(_, Some(_)) => return false,
+            ty::InstanceDef::ThreadLocalShim(_) => return false,
             _ => return true,
         };
         matches!(
@@ -241,6 +265,9 @@ impl<'tcx> InstanceDef<'tcx> {
                 )
             });
         }
+        if let ty::InstanceDef::ThreadLocalShim(..) = *self {
+            return false;
+        }
         tcx.codegen_fn_attrs(self.def_id()).requests_inline()
     }
 
@@ -264,6 +291,8 @@ impl<'tcx> InstanceDef<'tcx> {
     pub fn has_polymorphic_mir_body(&self) -> bool {
         match *self {
             InstanceDef::CloneShim(..)
+            | InstanceDef::ThreadLocalShim(..)
+            | InstanceDef::FnPtrAddrShim(..)
             | InstanceDef::FnPtrShim(..)
             | InstanceDef::DropGlue(_, Some(_)) => false,
             InstanceDef::ClosureOnceShim { .. }
@@ -295,6 +324,7 @@ fn fmt_instance(
         InstanceDef::Item(_) => Ok(()),
         InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
         InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
+        InstanceDef::ThreadLocalShim(_) => write!(f, " - shim(tls)"),
         InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
         InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
         InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
@@ -302,6 +332,7 @@ fn fmt_instance(
         InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
         InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
         InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
+        InstanceDef::FnPtrAddrShim(_, ty) => write!(f, " - shim({})", ty),
     }
 }
 
@@ -781,6 +812,12 @@ fn needs_fn_once_adapter_shim(
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Decodable, Encodable, HashStable)]
 pub struct UnusedGenericParams(FiniteBitSet<u32>);
 
+impl Default for UnusedGenericParams {
+    fn default() -> Self {
+        UnusedGenericParams::new_all_used()
+    }
+}
+
 impl UnusedGenericParams {
     pub fn new_all_unused(amount: u32) -> Self {
         let mut bitset = FiniteBitSet::new_empty();
@@ -807,4 +844,12 @@ impl UnusedGenericParams {
     pub fn all_used(&self) -> bool {
         self.0.is_empty()
     }
+
+    pub fn bits(&self) -> u32 {
+        self.0.0
+    }
+
+    pub fn from_bits(bits: u32) -> UnusedGenericParams {
+        UnusedGenericParams(FiniteBitSet(bits))
+    }
 }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 254ffc33c..195d951f9 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -5,7 +5,7 @@ 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_index::vec::IndexVec;
 use rustc_session::config::OptLevel;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
@@ -281,6 +281,12 @@ pub enum SizeSkeleton<'tcx> {
     /// Any statically computable Layout.
     Known(Size),
 
+    /// This is a generic const expression (i.e. N * 2), which may contain some parameters.
+    /// It must be of type usize, and represents the size of a type in bytes.
+    /// It is not required to be evaluatable to a concrete value, but can be used to check
+    /// that another SizeSkeleton is of equal size.
+    Generic(ty::Const<'tcx>),
+
     /// A potentially-fat pointer.
     Pointer {
         /// If true, this pointer is never null.
@@ -326,6 +332,37 @@ impl<'tcx> SizeSkeleton<'tcx> {
                     ),
                 }
             }
+            ty::Array(inner, len)
+                if len.ty() == tcx.types.usize && tcx.features().transmute_generic_consts =>
+            {
+                match SizeSkeleton::compute(inner, tcx, param_env)? {
+                    // This may succeed because the multiplication of two types may overflow
+                    // but a single size of a nested array will not.
+                    SizeSkeleton::Known(s) => {
+                        if let Some(c) = len.try_eval_target_usize(tcx, param_env) {
+                            let size = s
+                                .bytes()
+                                .checked_mul(c)
+                                .ok_or_else(|| LayoutError::SizeOverflow(ty))?;
+                            return Ok(SizeSkeleton::Known(Size::from_bytes(size)));
+                        }
+                        let len = tcx.expand_abstract_consts(len);
+                        let prev = ty::Const::from_target_usize(tcx, s.bytes());
+                        let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, prev) else {
+                            return Err(LayoutError::SizeOverflow(ty));
+                        };
+                        Ok(SizeSkeleton::Generic(gen_size))
+                    }
+                    SizeSkeleton::Pointer { .. } => Err(err),
+                    SizeSkeleton::Generic(g) => {
+                        let len = tcx.expand_abstract_consts(len);
+                        let Some(gen_size) = mul_sorted_consts(tcx, param_env, len, g) else {
+                            return Err(LayoutError::SizeOverflow(ty));
+                        };
+                        Ok(SizeSkeleton::Generic(gen_size))
+                    }
+                }
+            }
 
             ty::Adt(def, substs) => {
                 // Only newtypes and enums w/ nullable pointer optimization.
@@ -335,7 +372,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
 
                 // Get a zero-sized variant or a pointer newtype.
                 let zero_or_ptr_variant = |i| {
-                    let i = VariantIdx::new(i);
+                    let i = VariantIdx::from_usize(i);
                     let fields =
                         def.variant(i).fields.iter().map(|field| {
                             SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env)
@@ -355,6 +392,9 @@ impl<'tcx> SizeSkeleton<'tcx> {
                                 }
                                 ptr = Some(field);
                             }
+                            SizeSkeleton::Generic(_) => {
+                                return Err(err);
+                            }
                         }
                     }
                     Ok(ptr)
@@ -410,11 +450,66 @@ impl<'tcx> SizeSkeleton<'tcx> {
             (SizeSkeleton::Pointer { tail: a, .. }, SizeSkeleton::Pointer { tail: b, .. }) => {
                 a == b
             }
+            // constants are always pre-normalized into a canonical form so this
+            // only needs to check if their pointers are identical.
+            (SizeSkeleton::Generic(a), SizeSkeleton::Generic(b)) => a == b,
             _ => false,
         }
     }
 }
 
+/// When creating the layout for types with abstract conts in their size (i.e. [usize; 4 * N]),
+/// to ensure that they have a canonical order and can be compared directly we combine all
+/// constants, and sort the other terms. This allows comparison of expressions of sizes,
+/// allowing for things like transmutating between types that depend on generic consts.
+/// This returns `None` if multiplication of constants overflows.
+fn mul_sorted_consts<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    a: ty::Const<'tcx>,
+    b: ty::Const<'tcx>,
+) -> Option<ty::Const<'tcx>> {
+    use crate::mir::BinOp::Mul;
+    use ty::ConstKind::Expr;
+    use ty::Expr::Binop;
+
+    let mut work = vec![a, b];
+    let mut done = vec![];
+    while let Some(n) = work.pop() {
+        if let Expr(Binop(Mul, l, r)) = n.kind() {
+            work.push(l);
+            work.push(r)
+        } else {
+            done.push(n);
+        }
+    }
+    let mut k = 1;
+    let mut overflow = false;
+    done.retain(|c| {
+        let Some(c) = c.try_eval_target_usize(tcx, param_env) else {
+            return true;
+        };
+        let Some(next) = c.checked_mul(k) else {
+            overflow = true;
+            return false;
+        };
+        k = next;
+        false
+    });
+    if overflow {
+        return None;
+    }
+    if k != 1 {
+        done.push(ty::Const::from_target_usize(tcx, k));
+    } else if k == 0 {
+        return Some(ty::Const::from_target_usize(tcx, 0));
+    }
+    done.sort_unstable();
+
+    // create a single tree from the buffer
+    done.into_iter().reduce(|acc, n| tcx.mk_const(Expr(Binop(Mul, n, acc)), n.ty()))
+}
+
 pub trait HasTyCtxt<'tcx>: HasDataLayout {
     fn tcx(&self) -> TyCtxt<'tcx>;
 }
@@ -636,7 +731,7 @@ where
                     variants: Variants::Single { index: variant_index },
                     fields: match NonZeroUsize::new(fields) {
                         Some(fields) => FieldsShape::Union(fields),
-                        None => FieldsShape::Arbitrary { offsets: vec![], memory_index: vec![] },
+                        None => FieldsShape::Arbitrary { offsets: IndexVec::new(), memory_index: IndexVec::new() },
                     },
                     abi: Abi::Uninhabited,
                     largest_niche: None,
@@ -730,7 +825,11 @@ where
                         */
                     };
 
-                    let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type() {
+                    let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type()
+                        // Projection eagerly bails out when the pointee references errors,
+                        // fall back to structurally deducing metadata.
+                        && !pointee.references_error()
+                    {
                         let metadata = tcx.normalize_erasing_regions(
                             cx.param_env(),
                             tcx.mk_projection(metadata_def_id, [pointee]),
@@ -794,7 +893,8 @@ where
                 ty::Adt(def, substs) => {
                     match this.variants {
                         Variants::Single { index } => {
-                            TyMaybeWithLayout::Ty(def.variant(index).fields[i].ty(tcx, substs))
+                            let field = &def.variant(index).fields[FieldIdx::from_usize(i)];
+                            TyMaybeWithLayout::Ty(field.ty(tcx, substs))
                         }
 
                         // Discriminant field for enums (where applicable).
@@ -1126,10 +1226,11 @@ pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: SpecAbi) ->
         | AvrNonBlockingInterrupt
         | CCmseNonSecureCall
         | Wasm
-        | RustIntrinsic
         | PlatformIntrinsic
         | Unadjusted => false,
-        Rust | RustCall | RustCold => tcx.sess.panic_strategy() == PanicStrategy::Unwind,
+        Rust | RustCall | RustCold | RustIntrinsic => {
+            tcx.sess.panic_strategy() == PanicStrategy::Unwind
+        }
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index dce18a585..2e516f291 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -34,6 +34,7 @@ use rustc_attr as attr;
 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::steal::Steal;
 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
@@ -44,10 +45,12 @@ use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_serialize::{Decodable, Encodable};
+use rustc_session::lint::LintBuffer;
+pub use rustc_session::lint::RegisteredTools;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{ExpnId, ExpnKind, Span};
-use rustc_target::abi::{Align, Integer, IntegerType, VariantIdx};
+use rustc_target::abi::{Align, FieldIdx, Integer, IntegerType, VariantIdx};
 pub use rustc_target::abi::{ReprFlags, ReprOptions};
 use rustc_type_ir::WithCachedTypeInfo;
 pub use subst::*;
@@ -148,8 +151,6 @@ mod typeck_results;
 
 // Data types
 
-pub type RegisteredTools = FxHashSet<Ident>;
-
 pub struct ResolverOutputs {
     pub global_ctxt: ResolverGlobalCtxt,
     pub ast_lowering: ResolverAstLowering,
@@ -165,7 +166,8 @@ pub struct ResolverGlobalCtxt {
     pub effective_visibilities: EffectiveVisibilities,
     pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
-    pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
+    pub module_children_non_reexports: LocalDefIdMap<Vec<LocalDefId>>,
+    pub module_children_reexports: LocalDefIdMap<Vec<ModChild>>,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
     pub main_def: Option<MainDefinition>,
     pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
@@ -175,7 +177,6 @@ pub struct ResolverGlobalCtxt {
     /// Mapping from ident span to path span for paths that don't exist as written, but that
     /// 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>>,
@@ -209,6 +210,9 @@ pub struct ResolverAstLowering {
     pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
     /// List functions and methods for which lifetime elision was successful.
     pub lifetime_elision_allowed: FxHashSet<ast::NodeId>,
+
+    /// Lints that were emitted by the resolver and early lints.
+    pub lint_buffer: Steal<LintBuffer>,
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -325,12 +329,15 @@ pub struct ClosureSizeProfileData<'tcx> {
     pub after_feature_tys: Ty<'tcx>,
 }
 
-pub trait DefIdTree: Copy {
-    fn opt_parent(self, id: DefId) -> Option<DefId>;
+impl TyCtxt<'_> {
+    #[inline]
+    pub fn opt_parent(self, id: DefId) -> Option<DefId> {
+        self.def_key(id).parent.map(|index| DefId { index, ..id })
+    }
 
     #[inline]
     #[track_caller]
-    fn parent(self, id: DefId) -> DefId {
+    pub fn parent(self, id: DefId) -> DefId {
         match self.opt_parent(id) {
             Some(id) => id,
             // not `unwrap_or_else` to avoid breaking caller tracking
@@ -340,17 +347,17 @@ pub trait DefIdTree: Copy {
 
     #[inline]
     #[track_caller]
-    fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
+    pub fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
         self.opt_parent(id.to_def_id()).map(DefId::expect_local)
     }
 
     #[inline]
     #[track_caller]
-    fn local_parent(self, id: LocalDefId) -> LocalDefId {
+    pub fn local_parent(self, id: LocalDefId) -> LocalDefId {
         self.parent(id.to_def_id()).expect_local()
     }
 
-    fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
+    pub fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
         if descendant.krate != ancestor.krate {
             return false;
         }
@@ -365,13 +372,6 @@ pub trait DefIdTree: Copy {
     }
 }
 
-impl<'tcx> DefIdTree for TyCtxt<'tcx> {
-    #[inline]
-    fn opt_parent(self, id: DefId) -> Option<DefId> {
-        self.def_key(id).parent.map(|index| DefId { index, ..id })
-    }
-}
-
 impl<Id> Visibility<Id> {
     pub fn is_public(self) -> bool {
         matches!(self, Visibility::Public)
@@ -391,19 +391,19 @@ impl<Id: Into<DefId>> Visibility<Id> {
     }
 
     /// Returns `true` if an item with this visibility is accessible from the given module.
-    pub fn is_accessible_from(self, module: impl Into<DefId>, tree: impl DefIdTree) -> bool {
+    pub fn is_accessible_from(self, module: impl Into<DefId>, tcx: TyCtxt<'_>) -> bool {
         match self {
             // Public items are visible everywhere.
             Visibility::Public => true,
-            Visibility::Restricted(id) => tree.is_descendant_of(module.into(), id.into()),
+            Visibility::Restricted(id) => tcx.is_descendant_of(module.into(), id.into()),
         }
     }
 
     /// Returns `true` if this visibility is at least as accessible as the given visibility
-    pub fn is_at_least(self, vis: Visibility<impl Into<DefId>>, tree: impl DefIdTree) -> bool {
+    pub fn is_at_least(self, vis: Visibility<impl Into<DefId>>, tcx: TyCtxt<'_>) -> bool {
         match vis {
             Visibility::Public => self.is_public(),
-            Visibility::Restricted(id) => self.is_accessible_from(id, tree),
+            Visibility::Restricted(id) => self.is_accessible_from(id, tcx),
         }
     }
 }
@@ -544,7 +544,7 @@ impl<'tcx> Predicate<'tcx> {
             | PredicateKind::Clause(Clause::TypeOutlives(_))
             | PredicateKind::Clause(Clause::Projection(_))
             | PredicateKind::Clause(Clause::ConstArgHasType(..))
-            | PredicateKind::AliasEq(..)
+            | PredicateKind::AliasRelate(..)
             | PredicateKind::ObjectSafe(_)
             | PredicateKind::ClosureKind(_, _, _)
             | PredicateKind::Subtype(_)
@@ -641,7 +641,23 @@ pub enum PredicateKind<'tcx> {
     /// This predicate requires two terms to be equal to eachother.
     ///
     /// Only used for new solver
-    AliasEq(Term<'tcx>, Term<'tcx>),
+    AliasRelate(Term<'tcx>, Term<'tcx>, AliasRelationDirection),
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
+#[derive(HashStable, Debug)]
+pub enum AliasRelationDirection {
+    Equate,
+    Subtype,
+}
+
+impl std::fmt::Display for AliasRelationDirection {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            AliasRelationDirection::Equate => write!(f, "=="),
+            AliasRelationDirection::Subtype => write!(f, "<:"),
+        }
+    }
 }
 
 /// The crate outlives map is computed during typeck and contains the
@@ -977,11 +993,11 @@ impl<'tcx> Term<'tcx> {
         }
     }
 
-    /// This function returns `None` for `AliasKind::Opaque`.
+    /// This function returns the inner `AliasTy` if this term is a projection.
     ///
     /// 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>> {
+    pub fn to_projection_term(&self, tcx: TyCtxt<'tcx>) -> Option<AliasTy<'tcx>> {
         match self.unpack() {
             TermKind::Ty(ty) => match ty.kind() {
                 ty::Alias(kind, alias_ty) => match kind {
@@ -999,7 +1015,7 @@ impl<'tcx> Term<'tcx> {
 
     pub fn is_infer(&self) -> bool {
         match self.unpack() {
-            TermKind::Ty(ty) => ty.is_ty_or_numeric_infer(),
+            TermKind::Ty(ty) => ty.is_ty_var(),
             TermKind::Const(ct) => ct.is_ct_infer(),
         }
     }
@@ -1036,6 +1052,21 @@ impl<'tcx> TermKind<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum ParamTerm {
+    Ty(ParamTy),
+    Const(ParamConst),
+}
+
+impl ParamTerm {
+    pub fn index(self) -> usize {
+        match self {
+            ParamTerm::Ty(ty) => ty.index as usize,
+            ParamTerm::Const(ct) => ct.index as usize,
+        }
+    }
+}
+
 /// This kind of predicate has no *direct* correspondent in the
 /// syntax, but it roughly corresponds to the syntactic forms:
 ///
@@ -1129,6 +1160,13 @@ impl<'tcx, T> ToPredicate<'tcx, T> for T {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx> for PredicateKind<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(self).to_predicate(tcx)
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
@@ -1143,6 +1181,13 @@ impl<'tcx> ToPredicate<'tcx> for Clause<'tcx> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
+        ty::Binder::dummy(self).to_predicate(tcx)
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
@@ -1193,7 +1238,7 @@ impl<'tcx> Predicate<'tcx> {
             PredicateKind::Clause(Clause::Trait(t)) => Some(predicate.rebind(t)),
             PredicateKind::Clause(Clause::Projection(..))
             | PredicateKind::Clause(Clause::ConstArgHasType(..))
-            | PredicateKind::AliasEq(..)
+            | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1214,7 +1259,7 @@ impl<'tcx> Predicate<'tcx> {
             PredicateKind::Clause(Clause::Projection(t)) => Some(predicate.rebind(t)),
             PredicateKind::Clause(Clause::Trait(..))
             | PredicateKind::Clause(Clause::ConstArgHasType(..))
-            | PredicateKind::AliasEq(..)
+            | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1236,7 +1281,7 @@ impl<'tcx> Predicate<'tcx> {
             PredicateKind::Clause(Clause::Trait(..))
             | PredicateKind::Clause(Clause::ConstArgHasType(..))
             | PredicateKind::Clause(Clause::Projection(..))
-            | PredicateKind::AliasEq(..)
+            | PredicateKind::AliasRelate(..)
             | PredicateKind::Subtype(..)
             | PredicateKind::Coerce(..)
             | PredicateKind::Clause(Clause::RegionOutlives(..))
@@ -1386,7 +1431,7 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
         // lifetimes with 'static and remapping only those used in the
         // `impl Trait` return type, resulting in the parameters
         // shifting.
-        let id_substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
+        let id_substs = InternalSubsts::identity_for_item(tcx, def_id);
         debug!(?id_substs);
 
         // This zip may have several times the same lifetime in `substs` paired with a different
@@ -1410,12 +1455,12 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
 #[derive(HashStable, TyEncodable, TyDecodable)]
 pub struct Placeholder<T> {
     pub universe: UniverseIndex,
-    pub name: T,
+    pub bound: T,
 }
 
-pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
+pub type PlaceholderRegion = Placeholder<BoundRegion>;
 
-pub type PlaceholderType = Placeholder<BoundTyKind>;
+pub type PlaceholderType = Placeholder<BoundTy>;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
@@ -1847,7 +1892,7 @@ pub struct VariantDef {
     /// Discriminant of this variant.
     pub discr: VariantDiscr,
     /// Fields of this variant.
-    pub fields: Vec<FieldDef>,
+    pub fields: IndexVec<FieldIdx, FieldDef>,
     /// Flags of the variant (e.g. is field list non-exhaustive)?
     flags: VariantFlags,
 }
@@ -1874,7 +1919,7 @@ impl VariantDef {
         variant_did: Option<DefId>,
         ctor: Option<(CtorKind, DefId)>,
         discr: VariantDiscr,
-        fields: Vec<FieldDef>,
+        fields: IndexVec<FieldIdx, FieldDef>,
         adt_kind: AdtKind,
         parent_did: DefId,
         recovered: bool,
@@ -2028,7 +2073,6 @@ impl<'tcx> FieldDef {
     }
 }
 
-pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
 #[derive(Debug, PartialEq, Eq)]
 pub enum ImplOverlapKind {
     /// These impls are always allowed to overlap.
@@ -2071,7 +2115,9 @@ pub enum ImplOverlapKind {
     Issue33140,
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
+/// Useful source information about where a desugared associated type for an
+/// RPITIT originated from.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Encodable, Decodable, HashStable)]
 pub enum ImplTraitInTraitData {
     Trait { fn_def_id: DefId, opaque_def_id: DefId },
     Impl { fn_def_id: DefId },
@@ -2214,26 +2260,37 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
-        variant
-            .fields
-            .iter()
-            .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
+    /// If the def-id is an associated type that was desugared from a
+    /// return-position `impl Trait` from a trait, then provide the source info
+    /// about where that RPITIT came from.
+    pub fn opt_rpitit_info(self, def_id: DefId) -> Option<ImplTraitInTraitData> {
+        if let DefKind::AssocTy = self.def_kind(def_id) {
+            self.associated_item(def_id).opt_rpitit_info
+        } else {
+            None
+        }
+    }
+
+    pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<FieldIdx> {
+        variant.fields.iter_enumerated().find_map(|(i, field)| {
+            self.hygienic_eq(ident, field.ident(self), variant.def_id).then_some(i)
+        })
     }
 
     /// Returns `true` if the impls are the same polarity and the trait either
     /// has no items or is annotated `#[marker]` and prevents item overrides.
+    #[instrument(level = "debug", skip(self), ret)]
     pub fn impls_are_allowed_to_overlap(
         self,
         def_id1: DefId,
         def_id2: DefId,
     ) -> Option<ImplOverlapKind> {
+        let impl_trait_ref1 = self.impl_trait_ref(def_id1);
+        let impl_trait_ref2 = self.impl_trait_ref(def_id2);
         // If either trait impl references an error, they're allowed to overlap,
         // as one of them essentially doesn't exist.
-        if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.subst_identity().references_error())
-            || self
-                .impl_trait_ref(def_id2)
-                .map_or(false, |tr| tr.subst_identity().references_error())
+        if impl_trait_ref1.map_or(false, |tr| tr.subst_identity().references_error())
+            || impl_trait_ref2.map_or(false, |tr| tr.subst_identity().references_error())
         {
             return Some(ImplOverlapKind::Permitted { marker: false });
         }
@@ -2241,19 +2298,11 @@ impl<'tcx> TyCtxt<'tcx> {
         match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
             (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
                 // `#[rustc_reservation_impl]` impls don't overlap with anything
-                debug!(
-                    "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
-                    def_id1, def_id2
-                );
                 return Some(ImplOverlapKind::Permitted { marker: false });
             }
             (ImplPolarity::Positive, ImplPolarity::Negative)
             | (ImplPolarity::Negative, ImplPolarity::Positive) => {
                 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
-                debug!(
-                    "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
-                    def_id1, def_id2
-                );
                 return None;
             }
             (ImplPolarity::Positive, ImplPolarity::Positive)
@@ -2261,38 +2310,25 @@ impl<'tcx> TyCtxt<'tcx> {
         };
 
         let is_marker_overlap = {
-            let is_marker_impl = |def_id: DefId| -> bool {
-                let trait_ref = self.impl_trait_ref(def_id);
+            let is_marker_impl = |trait_ref: Option<EarlyBinder<TraitRef<'_>>>| -> bool {
                 trait_ref.map_or(false, |tr| self.trait_def(tr.skip_binder().def_id).is_marker)
             };
-            is_marker_impl(def_id1) && is_marker_impl(def_id2)
+            is_marker_impl(impl_trait_ref1) && is_marker_impl(impl_trait_ref2)
         };
 
         if is_marker_overlap {
-            debug!(
-                "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
-                def_id1, def_id2
-            );
             Some(ImplOverlapKind::Permitted { marker: true })
         } else {
             if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
                 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
                     if self_ty1 == self_ty2 {
-                        debug!(
-                            "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
-                            def_id1, def_id2
-                        );
                         return Some(ImplOverlapKind::Issue33140);
                     } else {
-                        debug!(
-                            "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
-                            def_id1, def_id2, self_ty1, self_ty2
-                        );
+                        debug!("found {self_ty1:?} != {self_ty2:?}");
                     }
                 }
             }
 
-            debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
             None
         }
     }
@@ -2349,7 +2385,9 @@ impl<'tcx> TyCtxt<'tcx> {
             | ty::InstanceDef::Virtual(..)
             | ty::InstanceDef::ClosureOnceShim { .. }
             | ty::InstanceDef::DropGlue(..)
-            | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
+            | ty::InstanceDef::CloneShim(..)
+            | ty::InstanceDef::ThreadLocalShim(..)
+            | ty::InstanceDef::FnPtrAddrShim(..) => self.mir_shims(instance),
         }
     }
 
@@ -2363,7 +2401,12 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Gets all attributes with the given name.
-    pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
+    pub fn get_attrs(
+        self,
+        did: impl Into<DefId>,
+        attr: Symbol,
+    ) -> impl Iterator<Item = &'tcx ast::Attribute> {
+        let did: DefId = did.into();
         let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
         if let Some(did) = did.as_local() {
             self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
@@ -2374,8 +2417,9 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
+    pub fn get_attr(self, did: impl Into<DefId>, attr: Symbol) -> Option<&'tcx ast::Attribute> {
         if cfg!(debug_assertions) && !rustc_feature::is_valid_for_get_attr(attr) {
+            let did: DefId = did.into();
             bug!("get_attr: unexpected called with DefId `{:?}`, attr `{:?}`", did, attr);
         } else {
             self.get_attrs(did, attr).next()
@@ -2383,7 +2427,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Determines whether an item is annotated with an attribute.
-    pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
+    pub fn has_attr(self, did: impl Into<DefId>, attr: Symbol) -> bool {
+        let did: DefId = did.into();
         if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
             bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
         } else {
@@ -2493,7 +2538,7 @@ impl<'tcx> TyCtxt<'tcx> {
         ident
     }
 
-    // FIXME(vincenzoapalzzo): move the HirId to a LocalDefId
+    // FIXME(vincenzopalazzo): move the HirId to a LocalDefId
     pub fn adjust_ident_and_get_scope(
         self,
         mut ident: Ident,
@@ -2540,12 +2585,18 @@ impl<'tcx> TyCtxt<'tcx> {
         matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
     }
 
-    pub fn impl_trait_in_trait_parent(self, mut def_id: DefId) -> DefId {
-        while let def_kind = self.def_kind(def_id) && def_kind != DefKind::AssocFn {
-            debug_assert_eq!(def_kind, DefKind::ImplTraitPlaceholder);
-            def_id = self.parent(def_id);
+    pub fn impl_trait_in_trait_parent_fn(self, mut def_id: DefId) -> DefId {
+        match self.opt_rpitit_info(def_id) {
+            Some(ImplTraitInTraitData::Trait { fn_def_id, .. })
+            | Some(ImplTraitInTraitData::Impl { fn_def_id, .. }) => fn_def_id,
+            None => {
+                while let def_kind = self.def_kind(def_id) && def_kind != DefKind::AssocFn {
+                    debug_assert_eq!(def_kind, DefKind::ImplTraitPlaceholder);
+                    def_id = self.parent(def_id);
+                }
+                def_id
+            }
         }
-        def_id
     }
 
     pub fn impl_method_has_trait_impl_trait_tys(self, def_id: DefId) -> bool {
@@ -2560,6 +2611,12 @@ impl<'tcx> TyCtxt<'tcx> {
 
         let Some(trait_item_def_id) = item.trait_item_def_id else { return false; };
 
+        if self.lower_impl_trait_in_trait_to_assoc_ty() {
+            return !self
+                .associated_types_for_impl_traits_in_associated_fn(trait_item_def_id)
+                .is_empty();
+        }
+
         // 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
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 8849e7eab..7534d06ae 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -63,6 +63,7 @@ trivially_parameterized_over_tcx! {
     ty::DeducedParamAttrs,
     ty::Generics,
     ty::ImplPolarity,
+    ty::ImplTraitInTraitData,
     ty::ReprOptions,
     ty::TraitDef,
     ty::UnusedGenericParams,
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 021c20b58..d947d9604 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -1,5 +1,5 @@
 use crate::ty::GenericArg;
-use crate::ty::{self, DefIdTree, Ty, TyCtxt};
+use crate::ty::{self, Ty, TyCtxt};
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sso::SsoHashSet;
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 6a053c368..72caadaf6 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1,6 +1,6 @@
 use crate::mir::interpret::{AllocRange, GlobalAlloc, Pointer, Provenance, Scalar};
 use crate::ty::{
-    self, ConstInt, DefIdTree, ParamConst, ScalarInt, Term, TermKind, Ty, TyCtxt, TypeFoldable,
+    self, ConstInt, ParamConst, ScalarInt, Term, TermKind, Ty, TyCtxt, TypeFoldable,
     TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
 use crate::ty::{GenericArg, GenericArgKind};
@@ -701,10 +701,12 @@ 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(bv) => {
-                    self.pretty_print_bound_var(debruijn, ty::BoundVar::from_u32(bv))?
-                }
-                ty::BoundTyKind::Param(_, s) => p!(write("{}", s)),
+                ty::BoundTyKind::Anon => self.pretty_print_bound_var(debruijn, bound_ty.var)?,
+                ty::BoundTyKind::Param(_, s) => match self.should_print_verbose() {
+                    true if debruijn == ty::INNERMOST => p!(write("^{}", s)),
+                    true => p!(write("^{}_{}", debruijn.index(), s)),
+                    false => p!(write("{}", s)),
+                },
             },
             ty::Adt(def, substs) => {
                 p!(print_def_path(def.did(), substs));
@@ -728,15 +730,15 @@ pub trait PrettyPrinter<'tcx>:
             }
             ty::Alias(ty::Projection, ref data) => {
                 if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
-                    && self.tcx().def_kind(data.def_id) == DefKind::ImplTraitPlaceholder
+                    && self.tcx().is_impl_trait_in_trait(data.def_id)
                 {
                     return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
                 } else {
                     p!(print(data))
                 }
             }
-            ty::Placeholder(placeholder) => match placeholder.name {
-                ty::BoundTyKind::Anon(_) => p!(write("Placeholder({:?})", placeholder)),
+            ty::Placeholder(placeholder) => match placeholder.bound.kind {
+                ty::BoundTyKind::Anon => p!(write("Placeholder({:?})", placeholder)),
                 ty::BoundTyKind::Param(_, name) => p!(write("{}", name)),
             },
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
@@ -1345,7 +1347,7 @@ pub trait PrettyPrinter<'tcx>:
                             p!(write("{}::{}", self.tcx().crate_name(def.did.krate), self.tcx().def_path(def.did).to_string_no_crate_verbose()))
                         }
                     }
-                    defkind => bug!("`{:?}` has unexpcted defkind {:?}", ct, defkind),
+                    defkind => bug!("`{:?}` has unexpected defkind {:?}", ct, defkind),
                 }
             }
             ty::ConstKind::Infer(infer_ct) => {
@@ -2100,7 +2102,9 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
-            | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
+            | ty::RePlaceholder(ty::Placeholder {
+                bound: ty::BoundRegion { kind: br, .. }, ..
+            }) => {
                 if br.is_named() {
                     return true;
                 }
@@ -2177,7 +2181,9 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             }
             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
-            | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
+            | ty::RePlaceholder(ty::Placeholder {
+                bound: ty::BoundRegion { kind: br, .. }, ..
+            }) => {
                 if let ty::BrNamed(_, name) = br && br.is_named() {
                     p!(write("{}", name));
                     return Ok(self);
@@ -2255,7 +2261,10 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
             ty::ReLateBound(db, br) if db >= self.current_index => {
                 *self.region_map.entry(br).or_insert_with(|| name(Some(db), self.current_index, br))
             }
-            ty::RePlaceholder(ty::PlaceholderRegion { name: kind, .. }) => {
+            ty::RePlaceholder(ty::PlaceholderRegion {
+                bound: ty::BoundRegion { kind, .. },
+                ..
+            }) => {
                 // If this is an anonymous placeholder, don't rename. Otherwise, in some
                 // async fns, we get a `for<'r> Send` bound
                 match kind {
@@ -2847,7 +2856,7 @@ 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)),
+            ty::PredicateKind::AliasRelate(t1, t2, dir) => p!(print(t1), write(" {} ", dir), print(t2)),
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/query.rs b/compiler/rustc_middle/src/ty/query.rs
index 2bc51baf8..fa9fea723 100644
--- a/compiler/rustc_middle/src/ty/query.rs
+++ b/compiler/rustc_middle/src/ty/query.rs
@@ -17,7 +17,8 @@ use crate::mir::interpret::{
 };
 use crate::mir::interpret::{LitToConstError, LitToConstInput};
 use crate::mir::mono::CodegenUnit;
-use crate::query::Key;
+use crate::query::erase::{erase, restore, Erase};
+use crate::query::{AsLocalKey, Key};
 use crate::thir;
 use crate::traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
@@ -41,7 +42,7 @@ use rustc_arena::TypedArena;
 use rustc_ast as ast;
 use rustc_ast::expand::allocator::AllocatorKind;
 use rustc_attr as attr;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
@@ -50,11 +51,15 @@ use rustc_data_structures::unord::UnordSet;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, DocLinkResMap};
-use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId};
+use rustc_hir::def_id::{
+    CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId, LocalDefIdMap, LocalDefIdSet,
+};
 use rustc_hir::hir_id::OwnerId;
 use rustc_hir::lang_items::{LangItem, LanguageItems};
 use rustc_hir::{Crate, ItemLocalId, TraitCandidate};
 use rustc_index::vec::IndexVec;
+pub(crate) use rustc_query_system::query::QueryJobId;
+use rustc_query_system::query::*;
 use rustc_session::config::{EntryFnType, OptLevel, OutputFilenames, SymbolManglingVersion};
 use rustc_session::cstore::{CrateDepKind, CrateSource};
 use rustc_session::cstore::{ExternCrate, ForeignModule, LinkagePreference, NativeLib};
@@ -64,18 +69,19 @@ use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi;
 use rustc_target::spec::PanicStrategy;
+
+use std::marker::PhantomData;
 use std::mem;
 use std::ops::Deref;
 use std::path::PathBuf;
 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>,
+    // Since we erase query value types we tell the typesystem about them with `PhantomData`.
+    _phantom_values: QueryPhantomValues<'tcx>,
 }
 
 #[derive(Copy, Clone)]
@@ -97,6 +103,11 @@ pub struct TyCtxtEnsure<'tcx> {
     pub tcx: TyCtxt<'tcx>,
 }
 
+#[derive(Copy, Clone)]
+pub struct TyCtxtEnsureWithValue<'tcx> {
+    pub tcx: TyCtxt<'tcx>,
+}
+
 impl<'tcx> TyCtxt<'tcx> {
     /// Returns a transparent wrapper for `TyCtxt`, which ensures queries
     /// are executed instead of just returning their results.
@@ -105,6 +116,15 @@ impl<'tcx> TyCtxt<'tcx> {
         TyCtxtEnsure { tcx: self }
     }
 
+    /// Returns a transparent wrapper for `TyCtxt`, which ensures queries
+    /// are executed instead of just returning their results.
+    ///
+    /// This version verifies that the computed result exists in the cache before returning.
+    #[inline(always)]
+    pub fn ensure_with_value(self) -> TyCtxtEnsureWithValue<'tcx> {
+        TyCtxtEnsureWithValue { tcx: self }
+    }
+
     /// Returns a transparent wrapper for `TyCtxt` which uses
     /// `span` as the location of queries performed through it.
     #[inline(always)]
@@ -135,6 +155,20 @@ macro_rules! query_if_arena {
     };
 }
 
+/// If `separate_provide_if_extern`, then the key can be projected to its
+/// local key via `<$K as AsLocalKey>::LocalKey`.
+macro_rules! local_key_if_separate_extern {
+    ([] $($K:tt)*) => {
+        $($K)*
+    };
+    ([(separate_provide_extern) $($rest:tt)*] $($K:tt)*) => {
+        <$($K)* as AsLocalKey>::LocalKey
+    };
+    ([$other:tt $($modifiers:tt)*] $($K:tt)*) => {
+        local_key_if_separate_extern!([$($modifiers)*] $($K)*)
+    };
+}
+
 macro_rules! separate_provide_extern_decl {
     ([][$name:ident]) => {
         ()
@@ -196,6 +230,12 @@ macro_rules! define_callbacks {
             $(pub type $name<'tcx> = $($K)*;)*
         }
         #[allow(nonstandard_style, unused_lifetimes)]
+        pub mod query_keys_local {
+            use super::*;
+
+            $(pub type $name<'tcx> = local_key_if_separate_extern!([$($modifiers)*] $($K)*);)*
+        }
+        #[allow(nonstandard_style, unused_lifetimes)]
         pub mod query_values {
             use super::*;
 
@@ -227,8 +267,8 @@ macro_rules! define_callbacks {
                 pub fn $name<'tcx>(
                     _tcx: TyCtxt<'tcx>,
                     value: query_provided::$name<'tcx>,
-                ) -> query_values::$name<'tcx> {
-                    query_if_arena!([$($modifiers)*]
+                ) -> Erase<query_values::$name<'tcx>> {
+                    erase(query_if_arena!([$($modifiers)*]
                         {
                             if mem::needs_drop::<query_provided::$name<'tcx>>() {
                                 &*_tcx.query_system.arenas.$name.alloc(value)
@@ -237,7 +277,7 @@ macro_rules! define_callbacks {
                             }
                         }
                         (value)
-                    )
+                    ))
                 }
             )*
         }
@@ -246,10 +286,40 @@ macro_rules! define_callbacks {
             use super::*;
 
             $(
-                pub type $name<'tcx> = <<$($K)* as Key>::CacheSelector as CacheSelector<'tcx, $V>>::Cache;
+                pub type $name<'tcx> = <<$($K)* as Key>::CacheSelector as CacheSelector<'tcx, Erase<$V>>>::Cache;
             )*
         }
 
+        $(
+            // Ensure that keys grow no larger than 64 bytes
+            #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+            const _: () = {
+                if mem::size_of::<query_keys::$name<'static>>() > 64 {
+                    panic!("{}", concat!(
+                        "the query `",
+                        stringify!($name),
+                        "` has a key type `",
+                        stringify!($($K)*),
+                        "` that is too large"
+                    ));
+                }
+            };
+
+            // Ensure that values grow no larger than 64 bytes
+            #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+            const _: () = {
+                if mem::size_of::<query_values::$name<'static>>() > 64 {
+                    panic!("{}", concat!(
+                        "the query `",
+                        stringify!($name),
+                        "` has a value type `",
+                        stringify!($V),
+                        "` that is too large"
+                    ));
+                }
+            };
+        )*
+
         pub struct QueryArenas<'tcx> {
             $($(#[$attr])* pub $name: query_if_arena!([$($modifiers)*]
                 (WorkerLocal<TypedArena<<$V as Deref>::Target>>)
@@ -269,6 +339,11 @@ macro_rules! define_callbacks {
         }
 
         #[derive(Default)]
+        pub struct QueryPhantomValues<'tcx> {
+            $($(#[$attr])* pub $name: PhantomData<query_values::$name<'tcx>>,)*
+        }
+
+        #[derive(Default)]
         pub struct QueryCaches<'tcx> {
             $($(#[$attr])* pub $name: query_storage::$name<'tcx>,)*
         }
@@ -282,7 +357,31 @@ macro_rules! define_callbacks {
 
                 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),
+                    None => self.tcx.queries.$name(
+                        self.tcx,
+                        DUMMY_SP,
+                        key,
+                        QueryMode::Ensure { check_cache: false },
+                    ),
+                };
+            })*
+        }
+
+        impl<'tcx> TyCtxtEnsureWithValue<'tcx> {
+            $($(#[$attr])*
+            #[inline(always)]
+            pub fn $name(self, key: query_helper_param_ty!($($K)*)) {
+                let key = key.into_query_param();
+                opt_remap_env_constness!([$($modifiers)*][key]);
+
+                match try_get_cached(self.tcx, &self.tcx.query_system.caches.$name, &key) {
+                    Some(_) => return,
+                    None => self.tcx.queries.$name(
+                        self.tcx,
+                        DUMMY_SP,
+                        key,
+                        QueryMode::Ensure { check_cache: true },
+                    ),
                 };
             })*
         }
@@ -305,17 +404,17 @@ macro_rules! define_callbacks {
                 let key = key.into_query_param();
                 opt_remap_env_constness!([$($modifiers)*][key]);
 
-                match try_get_cached(self.tcx, &self.tcx.query_system.caches.$name, &key) {
+                restore::<$V>(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(),
-                }
+                })
             })*
         }
 
         pub struct Providers {
             $(pub $name: for<'tcx> fn(
                 TyCtxt<'tcx>,
-                query_keys::$name<'tcx>,
+                query_keys_local::$name<'tcx>,
             ) -> query_provided::$name<'tcx>,)*
         }
 
@@ -325,17 +424,14 @@ macro_rules! define_callbacks {
 
         impl Default for Providers {
             fn default() -> Self {
-                use crate::query::Key;
-
                 Providers {
                     $($name: |_, key| bug!(
-                        "`tcx.{}({:?})` is not supported for {} crate;\n\
+                        "`tcx.{}({:?})` is not supported for this key;\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!($name),
                         key,
-                        if key.query_crate_is_local() { "local" } else { "external" },
                         stringify!($name),
                     ),)*
                 }
@@ -372,7 +468,7 @@ macro_rules! define_callbacks {
                 span: Span,
                 key: query_keys::$name<'tcx>,
                 mode: QueryMode,
-            ) -> Option<$V>;)*
+            ) -> Option<Erase<$V>>;)*
         }
     };
 }
@@ -399,11 +495,13 @@ macro_rules! define_feedable {
                 opt_remap_env_constness!([$($modifiers)*][key]);
 
                 let tcx = self.tcx;
-                let value = query_provided_to_value::$name(tcx, value);
+                let erased = query_provided_to_value::$name(tcx, value);
+                let value = restore::<$V>(erased);
                 let cache = &tcx.query_system.caches.$name;
 
                 match try_get_cached(tcx, cache, &key) {
                     Some(old) => {
+                        let old = restore::<$V>(old);
                         bug!(
                             "Trying to feed an already recorded value for query {} key={key:?}:\nold value: {old:?}\nnew value: {value:?}",
                             stringify!($name),
@@ -418,7 +516,7 @@ macro_rules! define_feedable {
                             &value,
                             hash_result!([$($modifiers)*]),
                         );
-                        cache.complete(key, value, dep_node_index);
+                        cache.complete(key, erased, dep_node_index);
                         value
                     }
                 }
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 3fc5f5bed..46c931d61 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -22,8 +22,6 @@ pub enum Cause {
 pub trait TypeRelation<'tcx>: Sized {
     fn tcx(&self) -> TyCtxt<'tcx>;
 
-    fn intercrate(&self) -> bool;
-
     fn param_env(&self) -> ty::ParamEnv<'tcx>;
 
     /// Returns a static string we can use for printouts.
@@ -33,9 +31,6 @@ pub trait TypeRelation<'tcx>: Sized {
     /// relation. Just affects error messages.
     fn a_is_expected(&self) -> bool;
 
-    /// Used during coherence. If called, must emit an always-ambiguous obligation.
-    fn mark_ambiguous(&mut self);
-
     fn with_cause<F, R>(&mut self, _cause: Cause, f: F) -> R
     where
         F: FnOnce(&mut Self) -> R,
@@ -559,23 +554,16 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, substs: a_substs, .. }),
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, substs: b_substs, .. }),
         ) if a_def_id == b_def_id => {
-            if relation.intercrate() {
-                // During coherence, opaque types should be treated as equal to each other, even if their generic params
-                // differ, as they could resolve to the same hidden type, even for different generic params.
-                relation.mark_ambiguous();
-                Ok(a)
-            } else {
-                let opt_variances = tcx.variances_of(a_def_id);
-                let substs = relate_substs_with_variances(
-                    relation,
-                    a_def_id,
-                    opt_variances,
-                    a_substs,
-                    b_substs,
-                    false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
-                )?;
-                Ok(tcx.mk_opaque(a_def_id, substs))
-            }
+            let opt_variances = tcx.variances_of(a_def_id);
+            let substs = relate_substs_with_variances(
+                relation,
+                a_def_id,
+                opt_variances,
+                a_substs,
+                b_substs,
+                false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
+            )?;
+            Ok(tcx.mk_opaque(a_def_id, substs))
         }
 
         _ => Err(TypeError::Sorts(expected_found(relation, a, b))),
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index ef643531b..5c604bb6d 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -4,7 +4,7 @@
 //! to help with the tedium.
 
 use crate::mir::interpret;
-use crate::mir::{Field, ProjectionKind};
+use crate::mir::ProjectionKind;
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
@@ -68,7 +68,7 @@ impl<'tcx> fmt::Debug for ty::adjustment::Adjustment<'tcx> {
 impl fmt::Debug for ty::BoundRegionKind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
-            ty::BrAnon(n, span) => write!(f, "BrAnon({n:?}, {span:?})"),
+            ty::BrAnon(span) => write!(f, "BrAnon({span:?})"),
             ty::BrNamed(did, name) => {
                 if did.is_crate_root() {
                     write!(f, "BrNamed({})", name)
@@ -177,7 +177,9 @@ 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:?})"),
+            ty::PredicateKind::AliasRelate(t1, t2, dir) => {
+                write!(f, "AliasRelate({t1:?}, {dir:?}, {t2:?})")
+            }
         }
     }
 }
@@ -215,6 +217,7 @@ CloneLiftImpls! {
 // implementation and traversal implementations (the latter only for
 // TyCtxt<'_> interners).
 TrivialTypeTraversalAndLiftImpls! {
+    ::rustc_target::abi::FieldIdx,
     ::rustc_target::abi::VariantIdx,
     crate::middle::region::Scope,
     crate::ty::FloatTy,
@@ -250,8 +253,9 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::AssocItem,
     crate::ty::AssocKind,
     crate::ty::AliasKind,
-    crate::ty::Placeholder<crate::ty::BoundRegionKind>,
-    crate::ty::Placeholder<crate::ty::BoundTyKind>,
+    crate::ty::AliasRelationDirection,
+    crate::ty::Placeholder<crate::ty::BoundRegion>,
+    crate::ty::Placeholder<crate::ty::BoundTy>,
     crate::ty::ClosureKind,
     crate::ty::FreeRegion,
     crate::ty::InferTy,
@@ -265,7 +269,6 @@ TrivialTypeTraversalAndLiftImpls! {
     ::rustc_span::Span,
     ::rustc_span::symbol::Ident,
     ::rustc_errors::ErrorGuaranteed,
-    Field,
     interpret::Scalar,
     rustc_target::abi::Size,
     ty::BoundVar,
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index e6a73e8bb..96c1577d5 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -7,14 +7,15 @@ use crate::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 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, TypeVisitableExt, TypeVisitor,
+    self, AdtDef, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor,
 };
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
 use polonius_engine::Atom;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::intern::Interned;
+use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
@@ -22,8 +23,8 @@ use rustc_index::vec::Idx;
 use rustc_macros::HashStable;
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
-use rustc_target::abi::VariantIdx;
-use rustc_target::spec::abi;
+use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
+use rustc_target::spec::abi::{self, Abi};
 use std::borrow::Cow;
 use std::cmp::Ordering;
 use std::fmt;
@@ -60,7 +61,7 @@ pub struct FreeRegion {
 #[derive(HashStable)]
 pub enum BoundRegionKind {
     /// An anonymous region parameter for a given fn (&T)
-    BrAnon(u32, Option<Span>),
+    BrAnon(Option<Span>),
 
     /// Named region parameters for functions (a in &'a T)
     ///
@@ -107,15 +108,6 @@ 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 {
@@ -136,10 +128,6 @@ impl<'tcx> Article for TyKind<'tcx> {
     }
 }
 
-// `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
-#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-static_assert_size!(TyKind<'_>, 32);
-
 /// A closure can be modeled as a struct that looks like:
 /// ```ignore (illustrative)
 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
@@ -517,8 +505,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
     #[inline]
     pub fn variant_range(&self, def_id: DefId, tcx: TyCtxt<'tcx>) -> Range<VariantIdx> {
         // FIXME requires optimized MIR
-        let num_variants = tcx.generator_layout(def_id).unwrap().variant_fields.len();
-        VariantIdx::new(0)..VariantIdx::new(num_variants)
+        FIRST_VARIANT..tcx.generator_layout(def_id).unwrap().variant_fields.next_index()
     }
 
     /// The discriminant for the given variant. Panics if the `variant_index` is
@@ -878,8 +865,8 @@ impl<'tcx> PolyTraitRef<'tcx> {
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for PolyTraitRef<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+impl<'tcx> IntoDiagnosticArg for TraitRef<'tcx> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         self.to_string().into_diagnostic_arg()
     }
 }
@@ -924,6 +911,12 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
     }
 }
 
+impl<'tcx> IntoDiagnosticArg for ExistentialTraitRef<'tcx> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        self.to_string().into_diagnostic_arg()
+    }
+}
+
 pub type PolyExistentialTraitRef<'tcx> = Binder<'tcx, ExistentialTraitRef<'tcx>>;
 
 impl<'tcx> PolyExistentialTraitRef<'tcx> {
@@ -940,12 +933,6 @@ impl<'tcx> PolyExistentialTraitRef<'tcx> {
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for PolyExistentialTraitRef<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
-        self.to_string().into_diagnostic_arg()
-    }
-}
-
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum BoundVariableKind {
@@ -1160,78 +1147,12 @@ impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
     }
 }
 
-struct SkipBindersAt<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    index: ty::DebruijnIndex,
-}
-
-impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for SkipBindersAt<'tcx> {
-    type Error = ();
-
-    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<TyCtxt<'tcx>>,
-    {
-        self.index.shift_in(1);
-        let value = t.try_map_bound(|t| t.try_fold_with(self));
-        self.index.shift_out(1);
-        value
-    }
-
-    fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        if !ty.has_escaping_bound_vars() {
-            Ok(ty)
-        } else if let ty::Bound(index, bv) = *ty.kind() {
-            if index == self.index {
-                Err(())
-            } else {
-                Ok(self.interner().mk_bound(index.shifted_out(1), bv))
-            }
-        } else {
-            ty.try_super_fold_with(self)
-        }
-    }
-
-    fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
-        if !r.has_escaping_bound_vars() {
-            Ok(r)
-        } else if let ty::ReLateBound(index, bv) = r.kind() {
-            if index == self.index {
-                Err(())
-            } else {
-                Ok(self.interner().mk_re_late_bound(index.shifted_out(1), bv))
-            }
-        } else {
-            r.try_super_fold_with(self)
-        }
-    }
-
-    fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
-        if !ct.has_escaping_bound_vars() {
-            Ok(ct)
-        } else if let ty::ConstKind::Bound(index, bv) = ct.kind() {
-            if index == self.index {
-                Err(())
-            } else {
-                Ok(self.interner().mk_const(
-                    ty::ConstKind::Bound(index.shifted_out(1), bv),
-                    ct.ty().try_fold_with(self)?,
-                ))
-            }
-        } else {
-            ct.try_super_fold_with(self)
-        }
-    }
-
-    fn try_fold_predicate(
-        &mut self,
-        p: ty::Predicate<'tcx>,
-    ) -> Result<ty::Predicate<'tcx>, Self::Error> {
-        if !p.has_escaping_bound_vars() { Ok(p) } else { p.try_super_fold_with(self) }
+impl<'tcx, T> IntoDiagnosticArg for Binder<'tcx, T>
+where
+    T: IntoDiagnosticArg,
+{
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        self.0.into_diagnostic_arg()
     }
 }
 
@@ -1288,7 +1209,7 @@ impl<'tcx> AliasTy<'tcx> {
         match tcx.def_kind(self.def_id) {
             DefKind::AssocTy | DefKind::AssocConst => tcx.parent(self.def_id),
             DefKind::ImplTraitPlaceholder => {
-                tcx.parent(tcx.impl_trait_in_trait_parent(self.def_id))
+                tcx.parent(tcx.impl_trait_in_trait_parent_fn(self.def_id))
             }
             kind => bug!("expected a projection AliasTy; found {kind:?}"),
         }
@@ -1376,6 +1297,12 @@ impl<'tcx> FnSig<'tcx> {
     }
 }
 
+impl<'tcx> IntoDiagnosticArg for FnSig<'tcx> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        self.to_string().into_diagnostic_arg()
+    }
+}
+
 pub type PolyFnSig<'tcx> = Binder<'tcx, FnSig<'tcx>>;
 
 impl<'tcx> PolyFnSig<'tcx> {
@@ -1403,6 +1330,18 @@ impl<'tcx> PolyFnSig<'tcx> {
     pub fn abi(&self) -> abi::Abi {
         self.skip_binder().abi
     }
+
+    pub fn is_fn_trait_compatible(&self) -> bool {
+        matches!(
+            self.skip_binder(),
+            ty::FnSig {
+                unsafety: rustc_hir::Unsafety::Normal,
+                abi: Abi::Rust,
+                c_variadic: false,
+                ..
+            }
+        )
+    }
 }
 
 pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<'tcx, FnSig<'tcx>>>;
@@ -1522,22 +1461,13 @@ pub struct BoundTy {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum BoundTyKind {
-    Anon(u32),
+    Anon,
     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(var.as_u32()) }
+        BoundTy { var, kind: BoundTyKind::Anon }
     }
 }
 
@@ -1616,19 +1546,24 @@ impl<'tcx> Region<'tcx> {
 
     pub fn get_name(self) -> Option<Symbol> {
         if self.has_name() {
-            let name = match *self {
+            match *self {
                 ty::ReEarlyBound(ebr) => Some(ebr.name),
                 ty::ReLateBound(_, br) => br.kind.get_name(),
                 ty::ReFree(fr) => fr.bound_region.get_name(),
                 ty::ReStatic => Some(kw::StaticLifetime),
-                ty::RePlaceholder(placeholder) => placeholder.name.get_name(),
+                ty::RePlaceholder(placeholder) => placeholder.bound.kind.get_name(),
                 _ => None,
-            };
-
-            return name;
+            }
+        } else {
+            None
         }
+    }
 
-        None
+    pub fn get_name_or_anon(self) -> Symbol {
+        match self.get_name() {
+            Some(name) => name,
+            None => sym::anon,
+        }
     }
 
     /// Is this region named by the user?
@@ -1639,7 +1574,7 @@ impl<'tcx> Region<'tcx> {
             ty::ReFree(fr) => fr.bound_region.is_named(),
             ty::ReStatic => true,
             ty::ReVar(..) => false,
-            ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
+            ty::RePlaceholder(placeholder) => placeholder.bound.kind.is_named(),
             ty::ReErased => false,
             ty::ReError(_) => false,
         }
@@ -1762,10 +1697,10 @@ impl<'tcx> Region<'tcx> {
         matches!(self.kind(), ty::ReVar(_))
     }
 
-    pub fn as_var(self) -> Option<RegionVid> {
+    pub fn as_var(self) -> RegionVid {
         match self.kind() {
-            ty::ReVar(vid) => Some(vid),
-            _ => None,
+            ty::ReVar(vid) => vid,
+            _ => bug!("expected region {:?} to be of kind ReVar", self),
         }
     }
 }
@@ -1892,7 +1827,7 @@ impl<'tcx> Ty<'tcx> {
             Adt(def, substs) => {
                 assert!(def.repr().simd(), "`simd_size_and_type` called on non-SIMD type");
                 let variant = def.non_enum_variant();
-                let f0_ty = variant.fields[0].ty(tcx, substs);
+                let f0_ty = variant.fields[FieldIdx::from_u32(0)].ty(tcx, substs);
 
                 match f0_ty.kind() {
                     // If the first field is an array, we assume it is the only field and its
@@ -1902,7 +1837,7 @@ 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_target_usize(tcx, ParamEnv::empty()) as u64, *f0_elem_ty)
+                        (f0_len.eval_target_usize(tcx, ParamEnv::empty()), *f0_elem_ty)
                     }
                     // Otherwise, the fields of this Adt are the SIMD components (and we assume they
                     // all have the same type).
@@ -1914,11 +1849,6 @@ impl<'tcx> Ty<'tcx> {
     }
 
     #[inline]
-    pub fn is_region_ptr(self) -> bool {
-        matches!(self.kind(), Ref(..))
-    }
-
-    #[inline]
     pub fn is_mutable_ptr(self) -> bool {
         matches!(
             self.kind(),
@@ -1944,7 +1874,7 @@ impl<'tcx> Ty<'tcx> {
     /// Tests if this is any kind of primitive pointer type (reference, raw pointer, fn pointer).
     #[inline]
     pub fn is_any_ptr(self) -> bool {
-        self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
+        self.is_ref() || self.is_unsafe_ptr() || self.is_fn_ptr()
     }
 
     #[inline]
@@ -2508,3 +2438,14 @@ impl<'tcx> VarianceDiagInfo<'tcx> {
         }
     }
 }
+
+// Some types are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+mod size_asserts {
+    use super::*;
+    use rustc_data_structures::static_assert_size;
+    // tidy-alphabetical-start
+    static_assert_size!(RegionKind<'_>, 28);
+    static_assert_size!(TyKind<'_>, 32);
+    // tidy-alphabetical-end
+}
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index b090bd9d8..f05b87343 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -302,8 +302,8 @@ impl<'tcx> InternalSubsts<'tcx> {
     }
 
     /// Creates an `InternalSubsts` that maps each generic parameter to itself.
-    pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: DefId) -> SubstsRef<'tcx> {
-        Self::for_item(tcx, def_id, |param, _| tcx.mk_param_from_def(param))
+    pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: impl Into<DefId>) -> SubstsRef<'tcx> {
+        Self::for_item(tcx, def_id.into(), |param, _| tcx.mk_param_from_def(param))
     }
 
     /// Creates an `InternalSubsts` for generic parameter definitions,
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index 233c0df2d..6747da7ab 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -1,5 +1,5 @@
 use crate::traits::specialization_graph;
-use crate::ty::fast_reject::{self, SimplifiedType, TreatParams};
+use crate::ty::fast_reject::{self, SimplifiedType, TreatParams, TreatProjections};
 use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{Ident, Ty, TyCtxt};
 use hir::def_id::LOCAL_CRATE;
@@ -100,8 +100,9 @@ impl<'tcx> TraitDef {
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    pub fn for_each_impl<F: FnMut(DefId)>(self, def_id: DefId, mut f: F) {
-        let impls = self.trait_impls_of(def_id);
+    /// `trait_def_id` MUST BE the `DefId` of a trait.
+    pub fn for_each_impl<F: FnMut(DefId)>(self, trait_def_id: DefId, mut f: F) {
+        let impls = self.trait_impls_of(trait_def_id);
 
         for &impl_def_id in impls.blanket_impls.iter() {
             f(impl_def_id);
@@ -114,27 +115,45 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    /// Iterate over every impl that could possibly match the
-    /// self type `self_ty`.
-    pub fn for_each_relevant_impl<F: FnMut(DefId)>(
+    /// Iterate over every impl that could possibly match the self type `self_ty`.
+    ///
+    /// `trait_def_id` MUST BE the `DefId` of a trait.
+    pub fn for_each_relevant_impl(
         self,
-        def_id: DefId,
+        trait_def_id: DefId,
         self_ty: Ty<'tcx>,
-        mut f: F,
+        f: impl FnMut(DefId),
     ) {
-        let _: Option<()> = self.find_map_relevant_impl(def_id, self_ty, |did| {
-            f(did);
-            None
-        });
+        self.for_each_relevant_impl_treating_projections(
+            trait_def_id,
+            self_ty,
+            TreatProjections::ForLookup,
+            f,
+        )
     }
 
+    pub fn for_each_relevant_impl_treating_projections(
+        self,
+        trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        treat_projections: TreatProjections,
+        mut f: impl FnMut(DefId),
+    ) {
+        let _: Option<()> =
+            self.find_map_relevant_impl(trait_def_id, self_ty, treat_projections, |did| {
+                f(did);
+                None
+            });
+    }
+
+    /// `trait_def_id` MUST BE the `DefId` of a trait.
     pub fn non_blanket_impls_for_ty(
         self,
-        def_id: DefId,
+        trait_def_id: DefId,
         self_ty: Ty<'tcx>,
     ) -> impl Iterator<Item = DefId> + 'tcx {
-        let impls = self.trait_impls_of(def_id);
-        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsInfer) {
+        let impls = self.trait_impls_of(trait_def_id);
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsCandidateKey) {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 return impls.iter().copied();
             }
@@ -145,18 +164,21 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Applies function to every impl that could possibly match the self type `self_ty` and returns
     /// the first non-none value.
-    pub fn find_map_relevant_impl<T, F: FnMut(DefId) -> Option<T>>(
+    ///
+    /// `trait_def_id` MUST BE the `DefId` of a trait.
+    pub fn find_map_relevant_impl<T>(
         self,
-        def_id: DefId,
+        trait_def_id: DefId,
         self_ty: Ty<'tcx>,
-        mut f: F,
+        treat_projections: TreatProjections,
+        mut f: impl FnMut(DefId) -> Option<T>,
     ) -> Option<T> {
         // FIXME: This depends on the set of all impls for the trait. That is
         // unfortunate wrt. incremental compilation.
         //
         // If we want to be faster, we could have separate queries for
         // blanket and non-blanket impls, and compare them separately.
-        let impls = self.trait_impls_of(def_id);
+        let impls = self.trait_impls_of(trait_def_id);
 
         for &impl_def_id in impls.blanket_impls.iter() {
             if let result @ Some(_) = f(impl_def_id) {
@@ -164,14 +186,17 @@ impl<'tcx> TyCtxt<'tcx> {
             }
         }
 
-        // Note that we're using `TreatParams::AsPlaceholder` to query `non_blanket_impls` while using
-        // `TreatParams::AsInfer` while actually adding them.
-        //
+        // Note that we're using `TreatParams::ForLookup` to query `non_blanket_impls` while using
+        // `TreatParams::AsCandidateKey` while actually adding them.
+        let treat_params = match treat_projections {
+            TreatProjections::NextSolverLookup => TreatParams::NextSolverLookup,
+            TreatProjections::ForLookup => TreatParams::ForLookup,
+        };
         // This way, when searching for some impl for `T: Trait`, we do not look at any impls
         // whose outer level is not a parameter or projection. Especially for things like
         // `T: Clone` this is incredibly useful as we would otherwise look at all the impls
         // of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
-        if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsPlaceholder) {
+        if let Some(simp) = fast_reject::simplify_type(self, self_ty, treat_params) {
             if let Some(impls) = impls.non_blanket_impls.get(&simp) {
                 for &impl_def_id in impls {
                     if let result @ Some(_) = f(impl_def_id) {
@@ -190,9 +215,11 @@ impl<'tcx> TyCtxt<'tcx> {
         None
     }
 
-    /// Returns an iterator containing all impls
-    pub fn all_impls(self, def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
-        let TraitImpls { blanket_impls, non_blanket_impls } = self.trait_impls_of(def_id);
+    /// Returns an iterator containing all impls for `trait_def_id`.
+    ///
+    /// `trait_def_id` MUST BE the `DefId` of a trait.
+    pub fn all_impls(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
+        let TraitImpls { blanket_impls, non_blanket_impls } = self.trait_impls_of(trait_def_id);
 
         blanket_impls.iter().chain(non_blanket_impls.iter().flat_map(|(_, v)| v)).cloned()
     }
@@ -231,7 +258,7 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
         }
 
         if let Some(simplified_self_ty) =
-            fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsInfer)
+            fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsCandidateKey)
         {
             impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
         } else {
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 586958247..47943b94c 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -8,10 +8,9 @@ use crate::{
     },
 };
 use rustc_data_structures::{
-    fx::FxHashMap,
+    fx::{FxHashMap, FxIndexMap},
     sync::Lrc,
     unord::{UnordItems, UnordSet},
-    vec_map::VecMap,
 };
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
@@ -26,6 +25,7 @@ use rustc_macros::HashStable;
 use rustc_middle::mir::FakeReadCause;
 use rustc_session::Session;
 use rustc_span::Span;
+use rustc_target::abi::FieldIdx;
 use std::{collections::hash_map::Entry, hash::Hash, iter};
 
 use super::RvalueScopes;
@@ -43,7 +43,7 @@ pub struct TypeckResults<'tcx> {
     /// or patterns (`S { field }`). The index is often useful by itself, but to learn more
     /// about the field you also need definition of the variant to which the field
     /// belongs, but it may not exist if it's a tuple field (`tuple.0`).
-    field_indices: ItemLocalMap<usize>,
+    field_indices: ItemLocalMap<FieldIdx>,
 
     /// Stores the types for various nodes in the AST. Note that this table
     /// is not guaranteed to be populated outside inference. See
@@ -155,7 +155,7 @@ pub struct TypeckResults<'tcx> {
     /// by this function. We also store the
     /// type here, so that mir-borrowck can use it as a hint for figuring out hidden types,
     /// even if they are only set in dead code (which doesn't show up in MIR).
-    pub concrete_opaque_types: VecMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
+    pub concrete_opaque_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
@@ -314,19 +314,19 @@ impl<'tcx> TypeckResults<'tcx> {
         LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.type_dependent_defs }
     }
 
-    pub fn field_indices(&self) -> LocalTableInContext<'_, usize> {
+    pub fn field_indices(&self) -> LocalTableInContext<'_, FieldIdx> {
         LocalTableInContext { hir_owner: self.hir_owner, data: &self.field_indices }
     }
 
-    pub fn field_indices_mut(&mut self) -> LocalTableInContextMut<'_, usize> {
+    pub fn field_indices_mut(&mut self) -> LocalTableInContextMut<'_, FieldIdx> {
         LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.field_indices }
     }
 
-    pub fn field_index(&self, id: hir::HirId) -> usize {
+    pub fn field_index(&self, id: hir::HirId) -> FieldIdx {
         self.field_indices().get(id).cloned().expect("no index for a field")
     }
 
-    pub fn opt_field_index(&self, id: hir::HirId) -> Option<usize> {
+    pub fn opt_field_index(&self, id: hir::HirId) -> Option<FieldIdx> {
         self.field_indices().get(id).cloned()
     }
 
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 90270e0ee..c8a78ec03 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -2,10 +2,11 @@
 
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::mir;
+use crate::ty::fast_reject::TreatProjections;
 use crate::ty::layout::IntegerExt;
 use crate::ty::{
-    self, DefIdTree, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder,
-    TypeSuperFoldable, TypeVisitableExt,
+    self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    TypeVisitableExt,
 };
 use crate::ty::{GenericArgKind, SubstsRef};
 use rustc_apfloat::Float as _;
@@ -14,11 +15,12 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::bit_set::GrowableBitSet;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_macros::HashStable;
-use rustc_span::{sym, DUMMY_SP};
+use rustc_session::Limit;
+use rustc_span::sym;
 use rustc_target::abi::{Integer, IntegerType, Size, TargetDataLayout};
 use rustc_target::spec::abi::Abi;
 use smallvec::SmallVec;
@@ -59,22 +61,13 @@ impl<'tcx> fmt::Display for Discr<'tcx> {
     }
 }
 
-fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
-    let (int, signed) = match *ty.kind() {
-        ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
-        ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
-        _ => bug!("non integer discriminant"),
-    };
-    (int.size(), signed)
-}
-
 impl<'tcx> Discr<'tcx> {
     /// Adds `1` to the value and wraps around if the maximum for the type is reached.
     pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
         self.checked_add(tcx, 1).0
     }
     pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
-        let (size, signed) = int_size_and_signed(tcx, self.ty);
+        let (size, signed) = self.ty.int_size_and_signed(tcx);
         let (val, oflo) = if signed {
             let min = size.signed_int_min();
             let max = size.signed_int_max();
@@ -233,17 +226,20 @@ impl<'tcx> TyCtxt<'tcx> {
         let recursion_limit = self.recursion_limit();
         for iteration in 0.. {
             if !recursion_limit.value_within_limit(iteration) {
-                return self.ty_error_with_message(
-                    DUMMY_SP,
-                    &format!("reached the recursion limit finding the struct tail for {}", ty),
-                );
+                let suggested_limit = match recursion_limit {
+                    Limit(0) => Limit(2),
+                    limit => limit * 2,
+                };
+                let reported =
+                    self.sess.emit_err(crate::error::RecursionLimitReached { ty, suggested_limit });
+                return self.ty_error(reported);
             }
             match *ty.kind() {
                 ty::Adt(def, substs) => {
                     if !def.is_struct() {
                         break;
                     }
-                    match def.non_enum_variant().fields.last() {
+                    match def.non_enum_variant().fields.raw.last() {
                         Some(field) => {
                             f();
                             ty = field.ty(self, substs);
@@ -317,7 +313,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
                     if a_def == b_def && a_def.is_struct() =>
                 {
-                    if let Some(f) = a_def.non_enum_variant().fields.last() {
+                    if let Some(f) = a_def.non_enum_variant().fields.raw.last() {
                         a = f.ty(self, a_substs);
                         b = f.ty(self, b_substs);
                     } else {
@@ -363,14 +359,20 @@ impl<'tcx> TyCtxt<'tcx> {
         self.ensure().coherent_trait(drop_trait);
 
         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() {
-                    return Some((*item_id, self.constness(impl_did)));
+        let (did, constness) = self.find_map_relevant_impl(
+            drop_trait,
+            ty,
+            // FIXME: This could also be some other mode, like "unexpected"
+            TreatProjections::ForLookup,
+            |impl_did| {
+                if let Some(item_id) = self.associated_item_def_ids(impl_did).first() {
+                    if validate(self, impl_did).is_ok() {
+                        return Some((*item_id, self.constness(impl_did)));
+                    }
                 }
-            }
-            None
-        })?;
+                None
+            },
+        )?;
 
         Some(ty::Destructor { did, constness })
     }
@@ -599,6 +601,28 @@ impl<'tcx> TyCtxt<'tcx> {
         self.static_mutability(def_id) == Some(hir::Mutability::Mut)
     }
 
+    /// Returns `true` if the item pointed to by `def_id` is a thread local which needs a
+    /// thread local shim generated.
+    #[inline]
+    pub fn needs_thread_local_shim(self, def_id: DefId) -> bool {
+        !self.sess.target.dll_tls_export
+            && self.is_thread_local_static(def_id)
+            && !self.is_foreign_item(def_id)
+    }
+
+    /// Returns the type a reference to the thread local takes in MIR.
+    pub fn thread_local_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
+        let static_ty = self.type_of(def_id).subst_identity();
+        if self.is_mutable_static(def_id) {
+            self.mk_mut_ptr(static_ty)
+        } else if self.is_foreign_item(def_id) {
+            self.mk_imm_ptr(static_ty)
+        } else {
+            // FIXME: These things don't *really* have 'static lifetime.
+            self.mk_imm_ref(self.lifetimes.re_static, static_ty)
+        }
+    }
+
     /// 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.
@@ -684,10 +708,6 @@ impl<'tcx> TyCtxt<'tcx> {
         ty::EarlyBinder(self.explicit_item_bounds(def_id))
     }
 
-    pub fn bound_impl_subject(self, def_id: DefId) -> ty::EarlyBinder<ty::ImplSubject<'tcx>> {
-        ty::EarlyBinder(self.impl_subject(def_id))
-    }
-
     /// Returns names of captured upvars for closures and generators.
     ///
     /// Here are some examples:
@@ -922,12 +942,21 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
 }
 
 impl<'tcx> Ty<'tcx> {
+    pub fn int_size_and_signed(self, tcx: TyCtxt<'tcx>) -> (Size, bool) {
+        let (int, signed) = match *self.kind() {
+            ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
+            ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
+            _ => bug!("non integer discriminant"),
+        };
+        (int.size(), signed)
+    }
+
     /// Returns the maximum value for the given numeric type (including `char`s)
     /// or returns `None` if the type is not numeric.
     pub fn numeric_max_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
         let val = match self.kind() {
             ty::Int(_) | ty::Uint(_) => {
-                let (size, signed) = int_size_and_signed(tcx, self);
+                let (size, signed) = self.int_size_and_signed(tcx);
                 let val =
                     if signed { size.signed_int_max() as u128 } else { size.unsigned_int_max() };
                 Some(val)
@@ -948,7 +977,7 @@ impl<'tcx> Ty<'tcx> {
     pub fn numeric_min_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
         let val = match self.kind() {
             ty::Int(_) | ty::Uint(_) => {
-                let (size, signed) = int_size_and_signed(tcx, self);
+                let (size, signed) = self.int_size_and_signed(tcx);
                 let val = if signed { size.truncate(size.signed_int_min() as u128) } else { 0 };
                 Some(val)
             }
@@ -1432,8 +1461,7 @@ pub fn reveal_opaque_types_in_bounds<'tcx>(
 }
 
 /// Determines whether an item is annotated with `doc(hidden)`.
-fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-    assert!(def_id.is_local());
+fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     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)))
@@ -1447,7 +1475,7 @@ 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 {
+pub fn is_intrinsic(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     matches!(tcx.fn_sig(def_id).skip_binder().abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
 }
 
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index 6814cadb9..08a62c900 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -83,6 +83,9 @@ pub trait TypeVisitableExt<'tcx>: TypeVisitable<TyCtxt<'tcx>> {
                 | TypeFlags::HAS_CT_PLACEHOLDER,
         )
     }
+    fn has_non_region_placeholders(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_TY_PLACEHOLDER | TypeFlags::HAS_CT_PLACEHOLDER)
+    }
     fn needs_subst(&self) -> bool {
         self.has_type_flags(TypeFlags::NEEDS_SUBST)
     }
diff --git a/compiler/rustc_middle/src/values.rs b/compiler/rustc_middle/src/values.rs
index c4f526dbd..55aa4fcff 100644
--- a/compiler/rustc_middle/src/values.rs
+++ b/compiler/rustc_middle/src/values.rs
@@ -4,7 +4,7 @@ use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::Representability;
-use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_query_system::query::QueryInfo;
 use rustc_query_system::Value;
 use rustc_span::def_id::LocalDefId;