Merging upstream version 1.70.0+dfsg1.

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

32 files changed, 862 insertions, 547 deletions

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)
     }