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-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs52
-rw-r--r--compiler/rustc_ast_lowering/src/index.rs9
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs20
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs29
-rw-r--r--compiler/rustc_codegen_cranelift/build_system/tests.rs7
-rw-r--r--compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs11
-rw-r--r--compiler/rustc_codegen_cranelift/patches/0001-portable-simd-Enable-the-exposed_provenance-feature.patch22
-rw-r--r--compiler/rustc_codegen_cranelift/patches/stdlib-lock.toml55
-rw-r--r--compiler/rustc_codegen_cranelift/rust-toolchain2
-rwxr-xr-xcompiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh1
-rw-r--r--compiler/rustc_codegen_cranelift/src/base.rs16
-rw-r--r--compiler/rustc_codegen_cranelift/src/common.rs14
-rw-r--r--compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs20
-rw-r--r--compiler/rustc_codegen_cranelift/src/unsize.rs114
-rw-r--r--compiler/rustc_codegen_cranelift/src/value_and_place.rs59
-rw-r--r--compiler/rustc_codegen_cranelift/y.cmd9
-rw-r--r--compiler/rustc_codegen_cranelift/y.ps112
-rw-r--r--compiler/rustc_codegen_ssa/src/assert_module_sources.rs4
-rw-r--r--compiler/rustc_hir/src/def.rs4
-rw-r--r--compiler/rustc_hir/src/definitions.rs4
-rw-r--r--compiler/rustc_hir/src/diagnostic_items.rs7
-rw-r--r--compiler/rustc_hir/src/hir.rs9
-rw-r--r--compiler/rustc_hir/src/pat_util.rs7
-rw-r--r--compiler/rustc_hir_analysis/src/astconv/generics.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/check/entry.rs49
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsic.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs51
-rw-r--r--compiler/rustc_hir_typeck/src/callee.rs59
-rw-r--r--compiler/rustc_hir_typeck/src/check.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/closure.rs7
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs29
-rw-r--r--compiler/rustc_index/src/bit_set.rs48
-rw-r--r--compiler/rustc_index/src/lib.rs1
-rw-r--r--compiler/rustc_infer/src/infer/error_reporting/mod.rs5
-rw-r--r--compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs12
-rw-r--r--compiler/rustc_infer/src/infer/outlives/for_liveness.rs1
-rw-r--r--compiler/rustc_infer/src/infer/outlives/mod.rs2
-rw-r--r--compiler/rustc_infer/src/infer/outlives/test_type_match.rs23
-rw-r--r--compiler/rustc_infer/src/infer/outlives/verify.rs22
-rw-r--r--compiler/rustc_infer/src/infer/relate/combine.rs2
-rw-r--r--compiler/rustc_infer/src/infer/relate/equate.rs8
-rw-r--r--compiler/rustc_infer/src/infer/relate/generalize.rs4
-rw-r--r--compiler/rustc_infer/src/infer/relate/glb.rs8
-rw-r--r--compiler/rustc_infer/src/infer/relate/lub.rs8
-rw-r--r--compiler/rustc_infer/src/infer/relate/nll.rs8
-rw-r--r--compiler/rustc_infer/src/infer/relate/sub.rs8
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp3
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder.rs4
-rw-r--r--compiler/rustc_middle/src/query/mod.rs4
-rw-r--r--compiler/rustc_middle/src/traits/select.rs2
-rw-r--r--compiler/rustc_middle/src/traits/solve.rs21
-rw-r--r--compiler/rustc_middle/src/traits/solve/inspect.rs6
-rw-r--r--compiler/rustc_middle/src/traits/solve/inspect/format.rs8
-rw-r--r--compiler/rustc_middle/src/ty/_match.rs9
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs2
-rw-r--r--compiler/rustc_middle/src/ty/relate.rs12
-rw-r--r--compiler/rustc_mir_build/src/build/matches/mod.rs94
-rw-r--r--compiler/rustc_mir_build/src/build/matches/test.rs42
-rw-r--r--compiler/rustc_mir_build/src/errors.rs4
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/check_match.rs60
-rw-r--r--compiler/rustc_parse/src/parser/diagnostics.rs36
-rw-r--r--compiler/rustc_passes/src/diagnostic_items.rs3
-rw-r--r--compiler/rustc_pattern_analysis/Cargo.toml47
-rw-r--r--compiler/rustc_pattern_analysis/src/constructor.rs159
-rw-r--r--compiler/rustc_pattern_analysis/src/errors.rs8
-rw-r--r--compiler/rustc_pattern_analysis/src/lib.rs113
-rw-r--r--compiler/rustc_pattern_analysis/src/lints.rs86
-rw-r--r--compiler/rustc_pattern_analysis/src/pat.rs162
-rw-r--r--compiler/rustc_pattern_analysis/src/rustc.rs (renamed from compiler/rustc_pattern_analysis/src/cx.rs)256
-rw-r--r--compiler/rustc_pattern_analysis/src/usefulness.rs241
-rw-r--r--compiler/rustc_resolve/src/lib.rs4
-rw-r--r--compiler/rustc_smir/src/rustc_smir/convert/mir.rs1
-rw-r--r--compiler/rustc_target/src/spec/mod.rs1
-rw-r--r--compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs19
-rw-r--r--compiler/rustc_trait_selection/src/solve/alias_relate.rs16
-rw-r--r--compiler/rustc_trait_selection/src/solve/assembly/mod.rs23
-rw-r--r--compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs14
-rw-r--r--compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs91
-rw-r--r--compiler/rustc_trait_selection/src/solve/inspect/analyse.rs2
-rw-r--r--compiler/rustc_trait_selection/src/solve/inspect/build.rs16
-rw-r--r--compiler/rustc_trait_selection/src/solve/mod.rs22
-rw-r--r--compiler/rustc_trait_selection/src/solve/normalizes_to/inherent.rs10
-rw-r--r--compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs21
-rw-r--r--compiler/rustc_trait_selection/src/solve/normalizes_to/weak_types.rs5
-rw-r--r--compiler/rustc_trait_selection/src/solve/project_goals.rs7
-rw-r--r--compiler/rustc_trait_selection/src/solve/search_graph.rs10
-rw-r--r--compiler/rustc_trait_selection/src/solve/trait_goals.rs66
-rw-r--r--compiler/rustc_trait_selection/src/traits/project.rs39
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs20
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/confirmation.rs11
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs15
-rw-r--r--compiler/rustc_trait_selection/src/traits/structural_normalize.rs61
-rw-r--r--compiler/rustc_trait_selection/src/traits/util.rs15
-rw-r--r--compiler/stable_mir/src/mir/body.rs6
-rw-r--r--compiler/stable_mir/src/mir/visit.rs4
96 files changed, 1649 insertions, 1084 deletions
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 11b5131b8d7..704f124dbcb 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -917,12 +917,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let poll_expr = {
             let awaitee = self.expr_ident(span, awaitee_ident, awaitee_pat_hid);
             let ref_mut_awaitee = self.expr_mut_addr_of(span, awaitee);
-            let task_context = if let Some(task_context_hid) = self.task_context {
-                self.expr_ident_mut(span, task_context_ident, task_context_hid)
-            } else {
-                // Use of `await` outside of an async context, we cannot use `task_context` here.
-                self.expr_err(span, self.tcx.sess.span_delayed_bug(span, "no task_context hir id"))
+
+            let Some(task_context_hid) = self.task_context else {
+                unreachable!("use of `await` outside of an async context.");
             };
+
+            let task_context = self.expr_ident_mut(span, task_context_ident, task_context_hid);
+
             let new_unchecked = self.expr_call_lang_item_fn_mut(
                 span,
                 hir::LangItem::PinNewUnchecked,
@@ -991,16 +992,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
             );
             let yield_expr = self.arena.alloc(yield_expr);
 
-            if let Some(task_context_hid) = self.task_context {
-                let lhs = self.expr_ident(span, task_context_ident, task_context_hid);
-                let assign =
-                    self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)));
-                self.stmt_expr(span, assign)
-            } else {
-                // Use of `await` outside of an async context. Return `yield_expr` so that we can
-                // proceed with type checking.
-                self.stmt(span, hir::StmtKind::Semi(yield_expr))
-            }
+            let Some(task_context_hid) = self.task_context else {
+                unreachable!("use of `await` outside of an async context.");
+            };
+
+            let lhs = self.expr_ident(span, task_context_ident, task_context_hid);
+            let assign =
+                self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)));
+            self.stmt_expr(span, assign)
         };
 
         let loop_block = self.block_all(span, arena_vec![self; inner_match_stmt, yield_stmt], None);
@@ -1635,19 +1634,32 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
         };
 
-        let mut yielded =
+        let yielded =
             opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span));
 
         if is_async_gen {
-            // yield async_gen_ready($expr);
-            yielded = self.expr_call_lang_item_fn(
+            // `yield $expr` is transformed into `task_context = yield async_gen_ready($expr)`.
+            // This ensures that we store our resumed `ResumeContext` correctly, and also that
+            // the apparent value of the `yield` expression is `()`.
+            let wrapped_yielded = self.expr_call_lang_item_fn(
                 span,
                 hir::LangItem::AsyncGenReady,
                 std::slice::from_ref(yielded),
             );
-        }
+            let yield_expr = self.arena.alloc(
+                self.expr(span, hir::ExprKind::Yield(wrapped_yielded, hir::YieldSource::Yield)),
+            );
 
-        hir::ExprKind::Yield(yielded, hir::YieldSource::Yield)
+            let Some(task_context_hid) = self.task_context else {
+                unreachable!("use of `await` outside of an async context.");
+            };
+            let task_context_ident = Ident::with_dummy_span(sym::_task_context);
+            let lhs = self.expr_ident(span, task_context_ident, task_context_hid);
+
+            hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span))
+        } else {
+            hir::ExprKind::Yield(yielded, hir::YieldSource::Yield)
+        }
     }
 
     /// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into:
diff --git a/compiler/rustc_ast_lowering/src/index.rs b/compiler/rustc_ast_lowering/src/index.rs
index f042f46e59c..993ddf00eb5 100644
--- a/compiler/rustc_ast_lowering/src/index.rs
+++ b/compiler/rustc_ast_lowering/src/index.rs
@@ -1,7 +1,6 @@
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_hir as hir;
-use rustc_hir::def_id::LocalDefId;
+use rustc_hir::def_id::{LocalDefId, LocalDefIdMap};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::*;
 use rustc_index::{Idx, IndexVec};
@@ -17,7 +16,7 @@ struct NodeCollector<'a, 'hir> {
 
     /// Outputs
     nodes: IndexVec<ItemLocalId, Option<ParentedNode<'hir>>>,
-    parenting: FxHashMap<LocalDefId, ItemLocalId>,
+    parenting: LocalDefIdMap<ItemLocalId>,
 
     /// The parent of this node
     parent_node: hir::ItemLocalId,
@@ -30,7 +29,7 @@ pub(super) fn index_hir<'hir>(
     tcx: TyCtxt<'hir>,
     item: hir::OwnerNode<'hir>,
     bodies: &SortedMap<ItemLocalId, &'hir Body<'hir>>,
-) -> (IndexVec<ItemLocalId, Option<ParentedNode<'hir>>>, FxHashMap<LocalDefId, ItemLocalId>) {
+) -> (IndexVec<ItemLocalId, Option<ParentedNode<'hir>>>, LocalDefIdMap<ItemLocalId>) {
     let mut nodes = IndexVec::new();
     // This node's parent should never be accessed: the owner's parent is computed by the
     // hir_owner_parent query. Make it invalid (= ItemLocalId::MAX) to force an ICE whenever it is
@@ -42,7 +41,7 @@ pub(super) fn index_hir<'hir>(
         parent_node: ItemLocalId::new(0),
         nodes,
         bodies,
-        parenting: FxHashMap::default(),
+        parenting: Default::default(),
     };
 
     match item {
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 96ed3eee02e..e29ecf55e2f 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -44,20 +44,20 @@ extern crate tracing;
 
 use crate::errors::{AssocTyParentheses, AssocTyParenthesesSub, MisplacedImplTrait};
 
+use rustc_ast::node_id::NodeMap;
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{DiagnosticArgFromDisplay, StashKey};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
-use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
-use rustc_hir::{ConstArg, GenericArg, ItemLocalId, ParamName, TraitCandidate};
+use rustc_hir::def_id::{LocalDefId, LocalDefIdMap, CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_hir::{ConstArg, GenericArg, ItemLocalMap, ParamName, TraitCandidate};
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt, Visibility};
@@ -119,13 +119,13 @@ struct LoweringContext<'a, 'hir> {
 
     current_hir_id_owner: hir::OwnerId,
     item_local_id_counter: hir::ItemLocalId,
-    trait_map: FxHashMap<ItemLocalId, Box<[TraitCandidate]>>,
+    trait_map: ItemLocalMap<Box<[TraitCandidate]>>,
 
     impl_trait_defs: Vec<hir::GenericParam<'hir>>,
     impl_trait_bounds: Vec<hir::WherePredicate<'hir>>,
 
     /// NodeIds that are lowered inside the current HIR owner.
-    node_id_to_local_id: FxHashMap<NodeId, hir::ItemLocalId>,
+    node_id_to_local_id: NodeMap<hir::ItemLocalId>,
 
     allow_try_trait: Lrc<[Symbol]>,
     allow_gen_future: Lrc<[Symbol]>,
@@ -135,7 +135,7 @@ struct LoweringContext<'a, 'hir> {
     /// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic
     /// defined on the TAIT, so we have type Foo<'a1> = ... and we establish a mapping in this
     /// field from the original parameter 'a to the new parameter 'a1.
-    generics_def_id_map: Vec<FxHashMap<LocalDefId, LocalDefId>>,
+    generics_def_id_map: Vec<LocalDefIdMap<LocalDefId>>,
 
     host_param_id: Option<LocalDefId>,
 }
@@ -380,7 +380,7 @@ enum AstOwner<'a> {
 }
 
 fn index_crate<'a>(
-    node_id_to_def_id: &FxHashMap<NodeId, LocalDefId>,
+    node_id_to_def_id: &NodeMap<LocalDefId>,
     krate: &'a Crate,
 ) -> IndexVec<LocalDefId, AstOwner<'a>> {
     let mut indexer = Indexer { node_id_to_def_id, index: IndexVec::new() };
@@ -390,7 +390,7 @@ fn index_crate<'a>(
     return indexer.index;
 
     struct Indexer<'s, 'a> {
-        node_id_to_def_id: &'s FxHashMap<NodeId, LocalDefId>,
+        node_id_to_def_id: &'s NodeMap<LocalDefId>,
         index: IndexVec<LocalDefId, AstOwner<'a>>,
     }
 
@@ -642,7 +642,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// `'a` declared on the TAIT, instead of the function.
     fn with_remapping<R>(
         &mut self,
-        remap: FxHashMap<LocalDefId, LocalDefId>,
+        remap: LocalDefIdMap<LocalDefId>,
         f: impl FnOnce(&mut Self) -> R,
     ) -> R {
         self.generics_def_id_map.push(remap);
@@ -1657,7 +1657,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         // Map from captured (old) lifetime to synthetic (new) lifetime.
         // Used to resolve lifetimes in the bounds of the opaque.
-        let mut captured_to_synthesized_mapping = FxHashMap::default();
+        let mut captured_to_synthesized_mapping = LocalDefIdMap::default();
         // List of (early-bound) synthetic lifetimes that are owned by the opaque.
         // This is used to create the `hir::Generics` owned by the opaque.
         let mut synthesized_lifetime_definitions = vec![];
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index b308cd82e54..948221e9407 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -674,13 +674,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // eagerly.
         let mut outlives_requirements = infcx.tcx.is_typeck_child(mir_def_id).then(Vec::new);
 
-        self.check_type_tests(
-            infcx,
-            param_env,
-            body,
-            outlives_requirements.as_mut(),
-            &mut errors_buffer,
-        );
+        self.check_type_tests(infcx, body, outlives_requirements.as_mut(), &mut errors_buffer);
 
         debug!(?errors_buffer);
         debug!(?outlives_requirements);
@@ -938,7 +932,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn check_type_tests(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         body: &Body<'tcx>,
         mut propagated_outlives_requirements: Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut RegionErrors<'tcx>,
@@ -956,7 +949,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             let generic_ty = type_test.generic_kind.to_ty(tcx);
             if self.eval_verify_bound(
                 infcx,
-                param_env,
                 generic_ty,
                 type_test.lower_bound,
                 &type_test.verify_bound,
@@ -967,7 +959,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             if let Some(propagated_outlives_requirements) = &mut propagated_outlives_requirements {
                 if self.try_promote_type_test(
                     infcx,
-                    param_env,
                     body,
                     type_test,
                     propagated_outlives_requirements,
@@ -1025,7 +1016,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn try_promote_type_test(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         body: &Body<'tcx>,
         type_test: &TypeTest<'tcx>,
         propagated_outlives_requirements: &mut Vec<ClosureOutlivesRequirement<'tcx>>,
@@ -1087,7 +1077,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // where `ur` is a local bound -- we are sometimes in a
             // position to prove things that our caller cannot. See
             // #53570 for an example.
-            if self.eval_verify_bound(infcx, param_env, generic_ty, ur, &type_test.verify_bound) {
+            if self.eval_verify_bound(infcx, generic_ty, ur, &type_test.verify_bound) {
                 continue;
             }
 
@@ -1270,7 +1260,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn eval_verify_bound(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         generic_ty: Ty<'tcx>,
         lower_bound: RegionVid,
         verify_bound: &VerifyBound<'tcx>,
@@ -1279,7 +1268,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         match verify_bound {
             VerifyBound::IfEq(verify_if_eq_b) => {
-                self.eval_if_eq(infcx, param_env, generic_ty, lower_bound, *verify_if_eq_b)
+                self.eval_if_eq(infcx, generic_ty, lower_bound, *verify_if_eq_b)
             }
 
             VerifyBound::IsEmpty => {
@@ -1293,11 +1282,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
 
             VerifyBound::AnyBound(verify_bounds) => verify_bounds.iter().any(|verify_bound| {
-                self.eval_verify_bound(infcx, param_env, generic_ty, lower_bound, verify_bound)
+                self.eval_verify_bound(infcx, generic_ty, lower_bound, verify_bound)
             }),
 
             VerifyBound::AllBounds(verify_bounds) => verify_bounds.iter().all(|verify_bound| {
-                self.eval_verify_bound(infcx, param_env, generic_ty, lower_bound, verify_bound)
+                self.eval_verify_bound(infcx, generic_ty, lower_bound, verify_bound)
             }),
         }
     }
@@ -1305,19 +1294,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn eval_if_eq(
         &self,
         infcx: &InferCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         generic_ty: Ty<'tcx>,
         lower_bound: RegionVid,
         verify_if_eq_b: ty::Binder<'tcx, VerifyIfEq<'tcx>>,
     ) -> bool {
         let generic_ty = self.normalize_to_scc_representatives(infcx.tcx, generic_ty);
         let verify_if_eq_b = self.normalize_to_scc_representatives(infcx.tcx, verify_if_eq_b);
-        match test_type_match::extract_verify_if_eq(
-            infcx.tcx,
-            param_env,
-            &verify_if_eq_b,
-            generic_ty,
-        ) {
+        match test_type_match::extract_verify_if_eq(infcx.tcx, &verify_if_eq_b, generic_ty) {
             Some(r) => {
                 let r_vid = self.to_region_vid(r);
                 self.eval_outlives(r_vid, lower_bound)
diff --git a/compiler/rustc_codegen_cranelift/build_system/tests.rs b/compiler/rustc_codegen_cranelift/build_system/tests.rs
index 1a38d5967f4..cb7b2454cd5 100644
--- a/compiler/rustc_codegen_cranelift/build_system/tests.rs
+++ b/compiler/rustc_codegen_cranelift/build_system/tests.rs
@@ -232,6 +232,13 @@ const EXTENDED_SYSROOT_SUITE: &[TestCase] = &[
         if runner.is_native {
             let mut test_cmd = PORTABLE_SIMD.test(&runner.target_compiler, &runner.dirs);
             test_cmd.arg("-q");
+            // FIXME remove after portable-simd update
+            test_cmd
+                .arg("--")
+                .arg("--skip")
+                .arg("core_simd::swizzle::simd_swizzle")
+                .arg("--skip")
+                .arg("core_simd::vector::Simd<T,N>::lanes");
             spawn_and_wait(test_cmd);
         }
     }),
diff --git a/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs b/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs
index afc51a47f14..1d51b499c8b 100644
--- a/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs
+++ b/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs
@@ -337,17 +337,6 @@ fn main() {
     static REF2: &u8 = REF1;
     assert_eq!(*REF1, *REF2);
 
-    extern "C" {
-        type A;
-    }
-
-    fn main() {
-        let x: &A = unsafe { &*(1usize as *const A) };
-
-        assert_eq!(unsafe { intrinsics::size_of_val(x) }, 0);
-        assert_eq!(unsafe { intrinsics::min_align_of_val(x) }, 1);
-    }
-
     #[repr(simd)]
     struct V([f64; 2]);
 
diff --git a/compiler/rustc_codegen_cranelift/patches/0001-portable-simd-Enable-the-exposed_provenance-feature.patch b/compiler/rustc_codegen_cranelift/patches/0001-portable-simd-Enable-the-exposed_provenance-feature.patch
new file mode 100644
index 00000000000..b8c0783f524
--- /dev/null
+++ b/compiler/rustc_codegen_cranelift/patches/0001-portable-simd-Enable-the-exposed_provenance-feature.patch
@@ -0,0 +1,22 @@
+From a101a43b795431ce617e7782afb451f4853afc00 Mon Sep 17 00:00:00 2001
+From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
+Date: Thu, 7 Dec 2023 14:51:35 +0000
+Subject: [PATCH] Enable the exposed_provenance feature
+
+---
+ crates/core_simd/tests/pointers.rs | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/crates/core_simd/tests/pointers.rs b/crates/core_simd/tests/pointers.rs
+index 0ae8f83..06620d6 100644
+--- a/crates/core_simd/tests/pointers.rs
++++ b/crates/core_simd/tests/pointers.rs
+@@ -1,4 +1,4 @@
+-#![feature(portable_simd, strict_provenance)]
++#![feature(exposed_provenance, portable_simd, strict_provenance)]
+ 
+ use core_simd::simd::{Simd, SimdConstPtr, SimdMutPtr};
+ 
+-- 
+2.34.1
+
diff --git a/compiler/rustc_codegen_cranelift/patches/stdlib-lock.toml b/compiler/rustc_codegen_cranelift/patches/stdlib-lock.toml
index 8a690bada0d..8e213f71c3f 100644
--- a/compiler/rustc_codegen_cranelift/patches/stdlib-lock.toml
+++ b/compiler/rustc_codegen_cranelift/patches/stdlib-lock.toml
@@ -36,15 +36,18 @@ dependencies = [
 
 [[package]]
 name = "allocator-api2"
-version = "0.2.15"
+version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "56fc6cf8dc8c4158eed8649f9b8b0ea1518eb62b544fe9490d66fa0b349eafe9"
+checksum = "0942ffc6dcaadf03badf6e6a2d0228460359d5e34b57ccdc720b7382dfbd5ec5"
 
 [[package]]
 name = "cc"
-version = "1.0.79"
+version = "1.0.83"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50d30906286121d95be3d479533b458f87493b30a4b5f79a607db8f5d11aa91f"
+checksum = "f1174fb0b6ec23863f8b971027804a42614e347eafb0a95bf0b12cdae21fc4d0"
+dependencies = [
+ "libc",
+]
 
 [[package]]
 name = "cfg-if"
@@ -58,9 +61,9 @@ dependencies = [
 
 [[package]]
 name = "compiler_builtins"
-version = "0.1.103"
+version = "0.1.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a3b73c3443a5fd2438d7ba4853c64e4c8efc2404a9e28a9234cc2d5eebc6c242"
+checksum = "99c3f9035afc33f4358773239573f7d121099856753e1bbd2a6a5207098fc741"
 dependencies = [
  "cc",
  "rustc-std-workspace-core",
@@ -124,9 +127,9 @@ dependencies = [
 
 [[package]]
 name = "gimli"
-version = "0.28.0"
+version = "0.28.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6fb8d784f27acf97159b40fc4db5ecd8aa23b9ad5ef69cdd136d3bc80665f0c0"
+checksum = "4271d37baee1b8c7e4b708028c57d816cf9d2434acb33a549475f78c181f6253"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-alloc",
@@ -135,9 +138,9 @@ dependencies = [
 
 [[package]]
 name = "hashbrown"
-version = "0.14.0"
+version = "0.14.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2c6201b9ff9fd90a5a3bac2e56a830d0caa509576f0e503818ee82c181b3437a"
+checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
 dependencies = [
  "allocator-api2",
  "compiler_builtins",
@@ -147,9 +150,9 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.3.2"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "443144c8cdadd93ebf52ddb4056d257f5b52c04d3c804e657d19eb73fc33668b"
+checksum = "d77f7ec81a6d05a3abb01ab6eb7590f6083d08449fe5a1c8b1e620283546ccb7"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-alloc",
@@ -167,9 +170,9 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.5.0"
+version = "2.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-core",
@@ -189,9 +192,9 @@ dependencies = [
 
 [[package]]
 name = "object"
-version = "0.32.0"
+version = "0.32.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77ac5bbd07aea88c60a577a1ce218075ffd59208b2d7ca97adf9bfc5aeb21ebe"
+checksum = "9cf5f9dd3933bd50a9e1f149ec995f39ae2c496d31fd772c1fd45ebc27e902b0"
 dependencies = [
  "compiler_builtins",
  "memchr",
@@ -241,9 +244,9 @@ dependencies = [
 
 [[package]]
 name = "r-efi"
-version = "4.2.0"
+version = "4.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "575fc2d9b3da54adbdfaddf6eca48fec256d977c8630a1750b8991347d1ac911"
+checksum = "0e244f96e03a3067f9e521d3167bd42657594cb8588c8d3a2db01545dc1af2e0"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-core",
@@ -402,9 +405,9 @@ dependencies = [
 
 [[package]]
 name = "unicode-width"
-version = "0.1.10"
+version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c0edd1e5b14653f783770bce4a4dabb4a5108a5370a5f5d8cfe8710c361f6c8b"
+checksum = "e51733f11c9c4f72aa0c160008246859e340b00807569a0da0e7a1079b27ba85"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-core",
@@ -419,6 +422,18 @@ dependencies = [
  "compiler_builtins",
  "core",
  "libc",
+ "unwinding",
+]
+
+[[package]]
+name = "unwinding"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37a19a21a537f635c16c7576f22d0f2f7d63353c1337ad4ce0d8001c7952a25b"
+dependencies = [
+ "compiler_builtins",
+ "gimli",
+ "rustc-std-workspace-core",
 ]
 
 [[package]]
diff --git a/compiler/rustc_codegen_cranelift/rust-toolchain b/compiler/rustc_codegen_cranelift/rust-toolchain
index 2997816d96c..4ba08f1af44 100644
--- a/compiler/rustc_codegen_cranelift/rust-toolchain
+++ b/compiler/rustc_codegen_cranelift/rust-toolchain
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2023-11-25"
+channel = "nightly-2023-12-19"
 components = ["rust-src", "rustc-dev", "llvm-tools"]
diff --git a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
index a299b6de6b1..7d7ffdadc7f 100755
--- a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
+++ b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
@@ -44,6 +44,7 @@ rm tests/ui/proc-macro/no-mangle-in-proc-macro-issue-111888.rs
 # vendor intrinsics
 rm tests/ui/sse2.rs # CodegenBackend::target_features not yet implemented
 rm tests/ui/simd/array-type.rs # "Index argument for `simd_insert` is not a constant"
+rm tests/ui/simd/masked-load-store.rs
 
 # exotic linkages
 rm tests/ui/issues/issue-33992.rs # unsupported linkages
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 8b0dc611075..df40a5eb475 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -353,7 +353,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             fx,
                             rustc_hir::LangItem::PanicBoundsCheck,
                             &[index, len, location],
-                            source_info.span,
+                            Some(source_info.span),
                         );
                     }
                     AssertKind::MisalignedPointerDereference { ref required, ref found } => {
@@ -365,7 +365,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             fx,
                             rustc_hir::LangItem::PanicMisalignedPointerDereference,
                             &[required, found, location],
-                            source_info.span,
+                            Some(source_info.span),
                         );
                     }
                     _ => {
@@ -945,19 +945,19 @@ pub(crate) fn codegen_panic<'tcx>(
     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
     let args = [msg_ptr, msg_len, location];
 
-    codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, source_info.span);
+    codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, Some(source_info.span));
 }
 
 pub(crate) fn codegen_panic_nounwind<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     msg_str: &str,
-    source_info: mir::SourceInfo,
+    span: Option<Span>,
 ) {
     let msg_ptr = fx.anonymous_str(msg_str);
     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
     let args = [msg_ptr, msg_len];
 
-    codegen_panic_inner(fx, rustc_hir::LangItem::PanicNounwind, &args, source_info.span);
+    codegen_panic_inner(fx, rustc_hir::LangItem::PanicNounwind, &args, span);
 }
 
 pub(crate) fn codegen_unwind_terminate<'tcx>(
@@ -967,16 +967,16 @@ pub(crate) fn codegen_unwind_terminate<'tcx>(
 ) {
     let args = [];
 
-    codegen_panic_inner(fx, reason.lang_item(), &args, source_info.span);
+    codegen_panic_inner(fx, reason.lang_item(), &args, Some(source_info.span));
 }
 
 fn codegen_panic_inner<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     lang_item: rustc_hir::LangItem,
     args: &[Value],
-    span: Span,
+    span: Option<Span>,
 ) {
-    let def_id = fx.tcx.require_lang_item(lang_item, Some(span));
+    let def_id = fx.tcx.require_lang_item(lang_item, span);
 
     let instance = Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
     let symbol_name = fx.tcx.symbol_name(instance).name;
diff --git a/compiler/rustc_codegen_cranelift/src/common.rs b/compiler/rustc_codegen_cranelift/src/common.rs
index 63562d33508..bd19a7ed059 100644
--- a/compiler/rustc_codegen_cranelift/src/common.rs
+++ b/compiler/rustc_codegen_cranelift/src/common.rs
@@ -98,11 +98,15 @@ fn clif_pair_type_from_ty<'tcx>(
 
 /// Is a pointer to this type a fat ptr?
 pub(crate) fn has_ptr_meta<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
-    let ptr_ty = Ty::new_ptr(tcx, TypeAndMut { ty, mutbl: rustc_hir::Mutability::Not });
-    match &tcx.layout_of(ParamEnv::reveal_all().and(ptr_ty)).unwrap().abi {
-        Abi::Scalar(_) => false,
-        Abi::ScalarPair(_, _) => true,
-        abi => unreachable!("Abi of ptr to {:?} is {:?}???", ty, abi),
+    if ty.is_sized(tcx, ParamEnv::reveal_all()) {
+        return false;
+    }
+
+    let tail = tcx.struct_tail_erasing_lifetimes(ty, ParamEnv::reveal_all());
+    match tail.kind() {
+        ty::Foreign(..) => false,
+        ty::Str | ty::Slice(..) | ty::Dynamic(..) => true,
+        _ => bug!("unexpected unsized tail: {:?}", tail),
     }
 }
 
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
index bfeeb117ff5..68126f12424 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
@@ -487,13 +487,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
-            let size = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
-                let (_ptr, info) = ptr.load_scalar_pair(fx);
-                let (size, _align) = crate::unsize::size_and_align_of_dst(fx, layout, info);
-                size
+            let meta = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
+                Some(ptr.load_scalar_pair(fx).1)
             } else {
-                fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64)
+                None
             };
+            let (size, _align) = crate::unsize::size_and_align_of(fx, layout, meta);
             ret.write_cvalue(fx, CValue::by_val(size, usize_layout));
         }
         sym::min_align_of_val => {
@@ -502,13 +501,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
-            let align = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
-                let (_ptr, info) = ptr.load_scalar_pair(fx);
-                let (_size, align) = crate::unsize::size_and_align_of_dst(fx, layout, info);
-                align
+            let meta = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
+                Some(ptr.load_scalar_pair(fx).1)
             } else {
-                fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64)
+                None
             };
+            let (_size, align) = crate::unsize::size_and_align_of(fx, layout, meta);
             ret.write_cvalue(fx, CValue::by_val(align, usize_layout));
         }
 
@@ -688,7 +686,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                             }
                         })
                     });
-                    crate::base::codegen_panic_nounwind(fx, &msg_str, source_info);
+                    crate::base::codegen_panic_nounwind(fx, &msg_str, Some(source_info.span));
                     return;
                 }
             }
diff --git a/compiler/rustc_codegen_cranelift/src/unsize.rs b/compiler/rustc_codegen_cranelift/src/unsize.rs
index c6133f2b35c..f777e11371f 100644
--- a/compiler/rustc_codegen_cranelift/src/unsize.rs
+++ b/compiler/rustc_codegen_cranelift/src/unsize.rs
@@ -2,6 +2,9 @@
 //!
 //! [`PointerCoercion::Unsize`]: `rustc_middle::ty::adjustment::PointerCoercion::Unsize`
 
+use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
+
+use crate::base::codegen_panic_nounwind;
 use crate::prelude::*;
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/base.rs#L159-L307
@@ -187,63 +190,113 @@ pub(crate) fn coerce_dyn_star<'tcx>(
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
 
-pub(crate) fn size_and_align_of_dst<'tcx>(
+pub(crate) fn size_and_align_of<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     layout: TyAndLayout<'tcx>,
-    info: Value,
+    info: Option<Value>,
 ) -> (Value, Value) {
-    assert!(layout.is_unsized() || layout.abi == Abi::Uninhabited);
-    match layout.ty.kind() {
+    if layout.is_sized() {
+        return (
+            fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64),
+            fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64),
+        );
+    }
+
+    let ty = layout.ty;
+    match ty.kind() {
         ty::Dynamic(..) => {
             // load size/align from vtable
-            (crate::vtable::size_of_obj(fx, info), crate::vtable::min_align_of_obj(fx, info))
+            (
+                crate::vtable::size_of_obj(fx, info.unwrap()),
+                crate::vtable::min_align_of_obj(fx, info.unwrap()),
+            )
         }
         ty::Slice(_) | ty::Str => {
             let unit = layout.field(fx, 0);
             // The info in this case is the length of the str, so the size is that
             // times the unit size.
             (
-                fx.bcx.ins().imul_imm(info, unit.size.bytes() as i64),
+                fx.bcx.ins().imul_imm(info.unwrap(), unit.size.bytes() as i64),
                 fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
             )
         }
-        _ => {
+        ty::Foreign(_) => {
+            let trap_block = fx.bcx.create_block();
+            let true_ = fx.bcx.ins().iconst(types::I8, 1);
+            let next_block = fx.bcx.create_block();
+            fx.bcx.ins().brif(true_, trap_block, &[], next_block, &[]);
+            fx.bcx.seal_block(trap_block);
+            fx.bcx.seal_block(next_block);
+            fx.bcx.switch_to_block(trap_block);
+
+            // `extern` type. We cannot compute the size, so panic.
+            let msg_str = with_no_visible_paths!({
+                with_no_trimmed_paths!({
+                    format!("attempted to compute the size or alignment of extern type `{ty}`")
+                })
+            });
+
+            codegen_panic_nounwind(fx, &msg_str, None);
+
+            fx.bcx.switch_to_block(next_block);
+
+            // This function does not return so we can now return whatever we want.
+            let size = fx.bcx.ins().iconst(fx.pointer_type, 42);
+            let align = fx.bcx.ins().iconst(fx.pointer_type, 42);
+            (size, align)
+        }
+        ty::Adt(..) | ty::Tuple(..) => {
             // First get the size of all statically known fields.
             // Don't use size_of because it also rounds up to alignment, which we
             // want to avoid, as the unsized field's alignment could be smaller.
             assert!(!layout.ty.is_simd());
 
             let i = layout.fields.count() - 1;
-            let sized_size = layout.fields.offset(i).bytes();
+            let unsized_offset_unadjusted = layout.fields.offset(i).bytes();
+            let unsized_offset_unadjusted =
+                fx.bcx.ins().iconst(fx.pointer_type, unsized_offset_unadjusted as i64);
             let sized_align = layout.align.abi.bytes();
             let sized_align = fx.bcx.ins().iconst(fx.pointer_type, sized_align as i64);
 
             // Recurse to get the size of the dynamically sized field (must be
             // the last field).
             let field_layout = layout.field(fx, i);
-            let (unsized_size, mut unsized_align) = size_and_align_of_dst(fx, field_layout, info);
-
-            // FIXME (#26403, #27023): We should be adding padding
-            // to `sized_size` (to accommodate the `unsized_align`
-            // required of the unsized field that follows) before
-            // summing it with `sized_size`. (Note that since #26403
-            // is unfixed, we do not yet add the necessary padding
-            // here. But this is where the add would go.)
-
-            // Return the sum of sizes and max of aligns.
-            let size = fx.bcx.ins().iadd_imm(unsized_size, sized_size as i64);
-
-            // Packed types ignore the alignment of their fields.
-            if let ty::Adt(def, _) = layout.ty.kind() {
-                if def.repr().packed() {
-                    unsized_align = sized_align;
+            let (unsized_size, mut unsized_align) = size_and_align_of(fx, field_layout, info);
+
+            // # First compute the dynamic alignment
+
+            // For packed types, we need to cap the alignment.
+            if let ty::Adt(def, _) = ty.kind() {
+                if let Some(packed) = def.repr().pack {
+                    if packed.bytes() == 1 {
+                        // We know this will be capped to 1.
+                        unsized_align = fx.bcx.ins().iconst(fx.pointer_type, 1);
+                    } else {
+                        // We have to dynamically compute `min(unsized_align, packed)`.
+                        let packed = fx.bcx.ins().iconst(fx.pointer_type, packed.bytes() as i64);
+                        let cmp = fx.bcx.ins().icmp(IntCC::UnsignedLessThan, unsized_align, packed);
+                        unsized_align = fx.bcx.ins().select(cmp, unsized_align, packed);
+                    }
                 }
             }
 
             // Choose max of two known alignments (combined value must
             // be aligned according to more restrictive of the two).
             let cmp = fx.bcx.ins().icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
-            let align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
+            let full_align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
+
+            // # Then compute the dynamic size
+
+            // The full formula for the size would be:
+            // let unsized_offset_adjusted = unsized_offset_unadjusted.align_to(unsized_align);
+            // let full_size = (unsized_offset_adjusted + unsized_size).align_to(full_align);
+            // However, `unsized_size` is a multiple of `unsized_align`.
+            // Therefore, we can equivalently do the `align_to(unsized_align)` *after* adding `unsized_size`:
+            // let full_size = (unsized_offset_unadjusted + unsized_size).align_to(unsized_align).align_to(full_align);
+            // Furthermore, `align >= unsized_align`, and therefore we only need to do:
+            // let full_size = (unsized_offset_unadjusted + unsized_size).align_to(full_align);
+
+            let full_size = fx.bcx.ins().iadd(unsized_offset_unadjusted, unsized_size);
 
             // Issue #27023: must add any necessary padding to `size`
             // (to make it a multiple of `align`) before returning it.
@@ -255,12 +308,13 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
             // emulated via the semi-standard fast bit trick:
             //
             //   `(size + (align-1)) & -align`
-            let addend = fx.bcx.ins().iadd_imm(align, -1);
-            let add = fx.bcx.ins().iadd(size, addend);
-            let neg = fx.bcx.ins().ineg(align);
-            let size = fx.bcx.ins().band(add, neg);
+            let addend = fx.bcx.ins().iadd_imm(full_align, -1);
+            let add = fx.bcx.ins().iadd(full_size, addend);
+            let neg = fx.bcx.ins().ineg(full_align);
+            let full_size = fx.bcx.ins().band(add, neg);
 
-            (size, align)
+            (full_size, full_align)
         }
+        _ => bug!("size_and_align_of_dst: {ty} not supported"),
     }
 }
diff --git a/compiler/rustc_codegen_cranelift/src/value_and_place.rs b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
index f52f59716a8..567a5669d49 100644
--- a/compiler/rustc_codegen_cranelift/src/value_and_place.rs
+++ b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
@@ -20,34 +20,36 @@ fn codegen_field<'tcx>(
         (base.offset_i64(fx, i64::try_from(field_offset.bytes()).unwrap()), field_layout)
     };
 
-    if let Some(extra) = extra {
-        if field_layout.is_sized() {
-            return simple(fx);
-        }
-        match field_layout.ty.kind() {
-            ty::Slice(..) | ty::Str | ty::Foreign(..) => simple(fx),
-            ty::Adt(def, _) if def.repr().packed() => {
-                assert_eq!(layout.align.abi.bytes(), 1);
-                simple(fx)
-            }
-            _ => {
-                // We have to align the offset for DST's
-                let unaligned_offset = field_offset.bytes();
-                let (_, unsized_align) =
-                    crate::unsize::size_and_align_of_dst(fx, field_layout, extra);
+    if field_layout.is_sized() {
+        return simple(fx);
+    }
+    match field_layout.ty.kind() {
+        ty::Slice(..) | ty::Str => simple(fx),
+        _ => {
+            let unaligned_offset = field_offset.bytes();
 
-                let one = fx.bcx.ins().iconst(fx.pointer_type, 1);
-                let align_sub_1 = fx.bcx.ins().isub(unsized_align, one);
-                let and_lhs = fx.bcx.ins().iadd_imm(align_sub_1, unaligned_offset as i64);
-                let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
-                let and_rhs = fx.bcx.ins().isub(zero, unsized_align);
-                let offset = fx.bcx.ins().band(and_lhs, and_rhs);
+            // Get the alignment of the field
+            let (_, mut unsized_align) = crate::unsize::size_and_align_of(fx, field_layout, extra);
 
-                (base.offset_value(fx, offset), field_layout)
+            // For packed types, we need to cap alignment.
+            if let ty::Adt(def, _) = layout.ty.kind() {
+                if let Some(packed) = def.repr().pack {
+                    let packed = fx.bcx.ins().iconst(fx.pointer_type, packed.bytes() as i64);
+                    let cmp = fx.bcx.ins().icmp(IntCC::UnsignedLessThan, unsized_align, packed);
+                    unsized_align = fx.bcx.ins().select(cmp, unsized_align, packed);
+                }
             }
+
+            // Bump the unaligned offset up to the appropriate alignment
+            let one = fx.bcx.ins().iconst(fx.pointer_type, 1);
+            let align_sub_1 = fx.bcx.ins().isub(unsized_align, one);
+            let and_lhs = fx.bcx.ins().iadd_imm(align_sub_1, unaligned_offset as i64);
+            let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
+            let and_rhs = fx.bcx.ins().isub(zero, unsized_align);
+            let offset = fx.bcx.ins().band(and_lhs, and_rhs);
+
+            (base.offset_value(fx, offset), field_layout)
         }
-    } else {
-        simple(fx)
     }
 }
 
@@ -731,13 +733,8 @@ impl<'tcx> CPlace<'tcx> {
         };
 
         let (field_ptr, field_layout) = codegen_field(fx, base, extra, layout, field);
-        if field_layout.is_unsized() {
-            if let ty::Foreign(_) = field_layout.ty.kind() {
-                assert!(extra.is_none());
-                CPlace::for_ptr(field_ptr, field_layout)
-            } else {
-                CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
-            }
+        if has_ptr_meta(fx.tcx, field_layout.ty) {
+            CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
         } else {
             CPlace::for_ptr(field_ptr, field_layout)
         }
diff --git a/compiler/rustc_codegen_cranelift/y.cmd b/compiler/rustc_codegen_cranelift/y.cmd
new file mode 100644
index 00000000000..e9b688645a4
--- /dev/null
+++ b/compiler/rustc_codegen_cranelift/y.cmd
@@ -0,0 +1,9 @@
+@echo off
+echo [BUILD] build system >&2
+mkdir build 2>nul
+rustc build_system/main.rs -o build\y.exe -Cdebuginfo=1 --edition 2021 || goto :error
+build\y.exe %* || goto :error
+goto :EOF
+
+:error
+exit /b
diff --git a/compiler/rustc_codegen_cranelift/y.ps1 b/compiler/rustc_codegen_cranelift/y.ps1
new file mode 100644
index 00000000000..02ef0fcbd50
--- /dev/null
+++ b/compiler/rustc_codegen_cranelift/y.ps1
@@ -0,0 +1,12 @@
+$ErrorActionPreference = "Stop"
+
+$host.ui.WriteErrorLine("[BUILD] build system")
+New-Item -ItemType Directory -Force -Path build | Out-Null
+& rustc build_system/main.rs -o build\y.exe -Cdebuginfo=1 --edition 2021
+if ($LASTEXITCODE -ne 0) {
+    exit $LASTEXITCODE
+}
+& build\y.exe $args
+if ($LASTEXITCODE -ne 0) {
+    exit $LASTEXITCODE
+}
diff --git a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
index 01d1b1059b9..a5bd10ecb34 100644
--- a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
+++ b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
@@ -278,13 +278,13 @@ impl CguReuseTracker {
 
                     if error {
                         let at_least = if at_least { 1 } else { 0 };
-                        errors::IncorrectCguReuseType {
+                        sess.emit_err(errors::IncorrectCguReuseType {
                             span: *error_span,
                             cgu_user_name,
                             actual_reuse,
                             expected_reuse,
                             at_least,
-                        };
+                        });
                     }
                 } else {
                     sess.emit_fatal(errors::CguNotRecorded { cgu_user_name, cgu_name });
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 258d6710bc5..e2bccf1ffa5 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -3,8 +3,8 @@ use crate::hir;
 
 use rustc_ast as ast;
 use rustc_ast::NodeId;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::ToStableHashKey;
+use rustc_data_structures::unord::UnordMap;
 use rustc_macros::HashStable_Generic;
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::hygiene::MacroKind;
@@ -806,4 +806,4 @@ pub enum LifetimeRes {
     ElidedAnchor { start: NodeId, end: NodeId },
 }
 
-pub type DocLinkResMap = FxHashMap<(Symbol, Namespace), Option<Res<NodeId>>>;
+pub type DocLinkResMap = UnordMap<(Symbol, Namespace), Option<Res<NodeId>>>;
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index d222325475d..2ab9a6ef32c 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -8,8 +8,8 @@ pub use crate::def_id::DefPathHash;
 use crate::def_id::{CrateNum, DefIndex, LocalDefId, StableCrateId, CRATE_DEF_INDEX, LOCAL_CRATE};
 use crate::def_path_hash_map::DefPathHashMap;
 
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{Hash64, StableHasher};
+use rustc_data_structures::unord::UnordMap;
 use rustc_index::IndexVec;
 use rustc_span::symbol::{kw, sym, Symbol};
 
@@ -95,7 +95,7 @@ impl DefPathTable {
 #[derive(Debug)]
 pub struct Definitions {
     table: DefPathTable,
-    next_disambiguator: FxHashMap<(LocalDefId, DefPathData), u32>,
+    next_disambiguator: UnordMap<(LocalDefId, DefPathData), u32>,
 
     /// The [StableCrateId] of the local crate.
     stable_crate_id: StableCrateId,
diff --git a/compiler/rustc_hir/src/diagnostic_items.rs b/compiler/rustc_hir/src/diagnostic_items.rs
index 243014b0027..d4d09f9a4e0 100644
--- a/compiler/rustc_hir/src/diagnostic_items.rs
+++ b/compiler/rustc_hir/src/diagnostic_items.rs
@@ -1,12 +1,13 @@
 use crate::def_id::DefId;
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_span::def_id::DefIdMap;
 use rustc_span::Symbol;
 
 #[derive(Debug, Default)]
 pub struct DiagnosticItems {
-    pub id_to_name: FxHashMap<DefId, Symbol>,
-    pub name_to_id: FxHashMap<Symbol, DefId>,
+    pub id_to_name: DefIdMap<Symbol>,
+    pub name_to_id: FxIndexMap<Symbol, DefId>,
 }
 
 impl<CTX: crate::HashStableContext> HashStable<CTX> for DiagnosticItems {
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 760945554f0..d148137091c 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1,6 +1,6 @@
 use crate::def::{CtorKind, DefKind, Res};
-use crate::def_id::DefId;
-pub(crate) use crate::hir_id::{HirId, ItemLocalId, OwnerId};
+use crate::def_id::{DefId, LocalDefIdMap};
+pub(crate) use crate::hir_id::{HirId, ItemLocalId, ItemLocalMap, OwnerId};
 use crate::intravisit::FnKind;
 use crate::LangItem;
 
@@ -11,7 +11,6 @@ pub use rustc_ast::{BinOp, BinOpKind, BindingAnnotation, BorrowKind, ByRef, Capt
 pub use rustc_ast::{ImplPolarity, IsAuto, Movability, Mutability, UnOp};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_index::IndexVec;
 use rustc_macros::HashStable_Generic;
@@ -874,12 +873,12 @@ pub struct OwnerInfo<'hir> {
     /// Contents of the HIR.
     pub nodes: OwnerNodes<'hir>,
     /// Map from each nested owner to its parent's local id.
-    pub parenting: FxHashMap<LocalDefId, ItemLocalId>,
+    pub parenting: LocalDefIdMap<ItemLocalId>,
     /// Collected attributes of the HIR nodes.
     pub attrs: AttributeMap<'hir>,
     /// Map indicating what traits are in scope for places where this
     /// is relevant; generated by resolve.
-    pub trait_map: FxHashMap<ItemLocalId, Box<[TraitCandidate]>>,
+    pub trait_map: ItemLocalMap<Box<[TraitCandidate]>>,
 }
 
 impl<'tcx> OwnerInfo<'tcx> {
diff --git a/compiler/rustc_hir/src/pat_util.rs b/compiler/rustc_hir/src/pat_util.rs
index 838c123f83c..e6050327186 100644
--- a/compiler/rustc_hir/src/pat_util.rs
+++ b/compiler/rustc_hir/src/pat_util.rs
@@ -1,7 +1,6 @@
 use crate::def::{CtorOf, DefKind, Res};
-use crate::def_id::DefId;
+use crate::def_id::{DefId, DefIdSet};
 use crate::hir::{self, BindingAnnotation, ByRef, HirId, PatKind};
-use rustc_data_structures::fx::FxHashSet;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 
@@ -114,9 +113,9 @@ impl hir::Pat<'_> {
             }
             _ => true,
         });
-        // We remove duplicates by inserting into a `FxHashSet` to avoid re-ordering
+        // We remove duplicates by inserting into a hash set to avoid re-ordering
         // the bounds
-        let mut duplicates = FxHashSet::default();
+        let mut duplicates = DefIdSet::default();
         variants.retain(|def_id| duplicates.insert(*def_id));
         variants
     }
diff --git a/compiler/rustc_hir_analysis/src/astconv/generics.rs b/compiler/rustc_hir_analysis/src/astconv/generics.rs
index be73c027fdc..b495b00ec70 100644
--- a/compiler/rustc_hir_analysis/src/astconv/generics.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/generics.rs
@@ -262,7 +262,7 @@ pub fn create_args_for_parent_generic_args<'tcx, 'a>(
                             // impl const PartialEq for () {}
                             // ```
                             //
-                            // Since this is a const impl, we need to insert `<false>` at the end of
+                            // Since this is a const impl, we need to insert a host arg at the end of
                             // `PartialEq`'s generics, but this errors since `Rhs` isn't specified.
                             // To work around this, we infer all arguments until we reach the host param.
                             args.push(ctx.inferred_kind(Some(&args), param, infer_args));
diff --git a/compiler/rustc_hir_analysis/src/check/entry.rs b/compiler/rustc_hir_analysis/src/check/entry.rs
index 8f194ae88ab..1d737e17e82 100644
--- a/compiler/rustc_hir_analysis/src/check/entry.rs
+++ b/compiler/rustc_hir_analysis/src/check/entry.rs
@@ -92,24 +92,6 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
 
     let mut error = false;
     let main_diagnostics_def_id = main_fn_diagnostics_def_id(tcx, main_def_id, main_span);
-    let main_fn_generics = tcx.generics_of(main_def_id);
-    let main_fn_predicates = tcx.predicates_of(main_def_id);
-    if main_fn_generics.count() != 0 || !main_fnsig.bound_vars().is_empty() {
-        let generics_param_span = main_fn_generics_params_span(tcx, main_def_id);
-        tcx.sess.emit_err(errors::MainFunctionGenericParameters {
-            span: generics_param_span.unwrap_or(main_span),
-            label_span: generics_param_span,
-        });
-        error = true;
-    } else if !main_fn_predicates.predicates.is_empty() {
-        // generics may bring in implicit predicates, so we skip this check if generics is present.
-        let generics_where_clauses_span = main_fn_where_clauses_span(tcx, main_def_id);
-        tcx.sess.emit_err(errors::WhereClauseOnMain {
-            span: generics_where_clauses_span.unwrap_or(main_span),
-            generics_span: generics_where_clauses_span,
-        });
-        error = true;
-    }
 
     let main_asyncness = tcx.asyncness(main_def_id);
     if main_asyncness.is_async() {
@@ -142,10 +124,6 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
     if let Some(term_did) = tcx.lang_items().termination() {
         let return_ty = main_fnsig.output();
         let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);
-        if !return_ty.bound_vars().is_empty() {
-            tcx.sess.emit_err(errors::MainFunctionReturnTypeGeneric { span: return_ty_span });
-            error = true;
-        }
         let return_ty = return_ty.skip_binder();
         let infcx = tcx.infer_ctxt().build();
         let cause = traits::ObligationCause::new(
@@ -180,7 +158,7 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
         Abi::Rust,
     ));
 
-    check_function_signature(
+    if check_function_signature(
         tcx,
         ObligationCause::new(
             main_span,
@@ -189,7 +167,28 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
         ),
         main_def_id,
         expected_sig,
-    );
+    )
+    .is_err()
+    {
+        return;
+    }
+
+    let main_fn_generics = tcx.generics_of(main_def_id);
+    let main_fn_predicates = tcx.predicates_of(main_def_id);
+    if main_fn_generics.count() != 0 || !main_fnsig.bound_vars().is_empty() {
+        let generics_param_span = main_fn_generics_params_span(tcx, main_def_id);
+        tcx.sess.emit_err(errors::MainFunctionGenericParameters {
+            span: generics_param_span.unwrap_or(main_span),
+            label_span: generics_param_span,
+        });
+    } else if !main_fn_predicates.predicates.is_empty() {
+        // generics may bring in implicit predicates, so we skip this check if generics is present.
+        let generics_where_clauses_span = main_fn_where_clauses_span(tcx, main_def_id);
+        tcx.sess.emit_err(errors::WhereClauseOnMain {
+            span: generics_where_clauses_span.unwrap_or(main_span),
+            generics_span: generics_where_clauses_span,
+        });
+    }
 }
 
 fn check_start_fn_ty(tcx: TyCtxt<'_>, start_def_id: DefId) {
@@ -255,7 +254,7 @@ fn check_start_fn_ty(tcx: TyCtxt<'_>, start_def_id: DefId) {
                 Abi::Rust,
             ));
 
-            check_function_signature(
+            let _ = check_function_signature(
                 tcx,
                 ObligationCause::new(
                     start_span,
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 33337190562..126bab68ae3 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -55,7 +55,7 @@ fn equate_intrinsic_type<'tcx>(
         && gen_count_ok(own_counts.consts, n_cts, "const")
     {
         let it_def_id = it.owner_id.def_id;
-        check_function_signature(
+        let _ = check_function_signature(
             tcx,
             ObligationCause::new(it.span, it_def_id, ObligationCauseCode::IntrinsicType),
             it_def_id.into(),
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index df17879a967..e4904a0437b 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -77,6 +77,7 @@ use std::num::NonZeroU32;
 
 use check::check_mod_item_types;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_errors::ErrorGuaranteed;
 use rustc_errors::{pluralize, struct_span_err, Diagnostic, DiagnosticBuilder};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::Visitor;
@@ -570,7 +571,26 @@ pub fn check_function_signature<'tcx>(
     mut cause: ObligationCause<'tcx>,
     fn_id: DefId,
     expected_sig: ty::PolyFnSig<'tcx>,
-) {
+) -> Result<(), ErrorGuaranteed> {
+    fn extract_span_for_error_reporting<'tcx>(
+        tcx: TyCtxt<'tcx>,
+        err: TypeError<'_>,
+        cause: &ObligationCause<'tcx>,
+        fn_id: LocalDefId,
+    ) -> rustc_span::Span {
+        let mut args = {
+            let node = tcx.hir().expect_owner(fn_id);
+            let decl = node.fn_decl().unwrap_or_else(|| bug!("expected fn decl, found {:?}", node));
+            decl.inputs.iter().map(|t| t.span).chain(std::iter::once(decl.output.span()))
+        };
+
+        match err {
+            TypeError::ArgumentMutability(i)
+            | TypeError::ArgumentSorts(ExpectedFound { .. }, i) => args.nth(i).unwrap(),
+            _ => cause.span(),
+        }
+    }
+
     let local_id = fn_id.as_local().unwrap_or(CRATE_DEF_ID);
 
     let param_env = ty::ParamEnv::empty();
@@ -587,8 +607,7 @@ pub fn check_function_signature<'tcx>(
         Ok(()) => {
             let errors = ocx.select_all_or_error();
             if !errors.is_empty() {
-                infcx.err_ctxt().report_fulfillment_errors(errors);
-                return;
+                return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
             }
         }
         Err(err) => {
@@ -610,30 +629,14 @@ pub fn check_function_signature<'tcx>(
                 false,
                 false,
             );
-            diag.emit();
-            return;
+            return Err(diag.emit());
         }
     }
 
     let outlives_env = OutlivesEnvironment::new(param_env);
-    let _ = ocx.resolve_regions_and_report_errors(local_id, &outlives_env);
-
-    fn extract_span_for_error_reporting<'tcx>(
-        tcx: TyCtxt<'tcx>,
-        err: TypeError<'_>,
-        cause: &ObligationCause<'tcx>,
-        fn_id: LocalDefId,
-    ) -> rustc_span::Span {
-        let mut args = {
-            let node = tcx.hir().expect_owner(fn_id);
-            let decl = node.fn_decl().unwrap_or_else(|| bug!("expected fn decl, found {:?}", node));
-            decl.inputs.iter().map(|t| t.span).chain(std::iter::once(decl.output.span()))
-        };
-
-        match err {
-            TypeError::ArgumentMutability(i)
-            | TypeError::ArgumentSorts(ExpectedFound { .. }, i) => args.nth(i).unwrap(),
-            _ => cause.span(),
-        }
+    if let Err(e) = ocx.resolve_regions_and_report_errors(local_id, &outlives_env) {
+        return Err(e);
     }
+
+    Ok(())
 }
diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index 51f38240033..5e6b54950b3 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -471,6 +471,65 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
+        if let Some(def_id) = def_id
+            && self.tcx.def_kind(def_id) == hir::def::DefKind::Fn
+            && self.tcx.is_intrinsic(def_id)
+            && self.tcx.item_name(def_id) == sym::const_eval_select
+        {
+            let fn_sig = self.resolve_vars_if_possible(fn_sig);
+            for idx in 0..=1 {
+                let arg_ty = fn_sig.inputs()[idx + 1];
+                let span = arg_exprs.get(idx + 1).map_or(call_expr.span, |arg| arg.span);
+                // Check that second and third argument of `const_eval_select` must be `FnDef`, and additionally that
+                // the second argument must be `const fn`. The first argument must be a tuple, but this is already expressed
+                // in the function signature (`F: FnOnce<ARG>`), so I did not bother to add another check here.
+                //
+                // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
+                if let ty::FnDef(def_id, _args) = *arg_ty.kind() {
+                    let fn_once_def_id =
+                        self.tcx.require_lang_item(hir::LangItem::FnOnce, Some(span));
+                    let fn_once_output_def_id =
+                        self.tcx.require_lang_item(hir::LangItem::FnOnceOutput, Some(span));
+                    if self.tcx.generics_of(fn_once_def_id).host_effect_index.is_none() {
+                        if idx == 0 && !self.tcx.is_const_fn_raw(def_id) {
+                            self.tcx.sess.emit_err(errors::ConstSelectMustBeConst { span });
+                        }
+                    } else {
+                        let const_param: ty::GenericArg<'tcx> =
+                            ([self.tcx.consts.false_, self.tcx.consts.true_])[idx].into();
+                        self.register_predicate(traits::Obligation::new(
+                            self.tcx,
+                            self.misc(span),
+                            self.param_env,
+                            ty::TraitRef::new(
+                                self.tcx,
+                                fn_once_def_id,
+                                [arg_ty.into(), fn_sig.inputs()[0].into(), const_param],
+                            ),
+                        ));
+
+                        self.register_predicate(traits::Obligation::new(
+                            self.tcx,
+                            self.misc(span),
+                            self.param_env,
+                            ty::ProjectionPredicate {
+                                projection_ty: ty::AliasTy::new(
+                                    self.tcx,
+                                    fn_once_output_def_id,
+                                    [arg_ty.into(), fn_sig.inputs()[0].into(), const_param],
+                                ),
+                                term: fn_sig.output().into(),
+                            },
+                        ));
+
+                        self.select_obligations_where_possible(|_| {});
+                    }
+                } else {
+                    self.tcx.sess.emit_err(errors::ConstSelectMustBeFn { span, ty: arg_ty });
+                }
+            }
+        }
+
         fn_sig.output()
     }
 
diff --git a/compiler/rustc_hir_typeck/src/check.rs b/compiler/rustc_hir_typeck/src/check.rs
index 7facf8a4016..2855cea80b2 100644
--- a/compiler/rustc_hir_typeck/src/check.rs
+++ b/compiler/rustc_hir_typeck/src/check.rs
@@ -261,7 +261,7 @@ fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>
         bounds,
     );
 
-    check_function_signature(
+    let _ = check_function_signature(
         tcx,
         ObligationCause::new(
             tcx.def_span(fn_id),
@@ -300,7 +300,7 @@ fn check_lang_start_fn<'tcx>(tcx: TyCtxt<'tcx>, fn_sig: ty::FnSig<'tcx>, def_id:
         Abi::Rust,
     ));
 
-    check_function_signature(
+    let _ = check_function_signature(
         tcx,
         ObligationCause::new(
             tcx.def_span(def_id),
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 7e43d67587b..d19d304128a 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -650,9 +650,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         },
                     )
                 }
-                // For a `gen {}` block created as a `gen fn` body, we need the return type to be
-                // ().
-                Some(hir::CoroutineKind::Gen(hir::CoroutineSource::Fn)) => self.tcx.types.unit,
+                // All `gen {}` and `async gen {}` must return unit.
+                Some(hir::CoroutineKind::Gen(_) | hir::CoroutineKind::AsyncGen(_)) => {
+                    self.tcx.types.unit
+                }
 
                 _ => astconv.ty_infer(None, decl.output.span()),
             },
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 24b577fd3c5..4bc237c2383 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -1498,7 +1498,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let ty = self.resolve_vars_with_obligations(ty);
 
         if self.next_trait_solver()
-            && let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _) = ty.kind()
+            && let ty::Alias(..) = ty.kind()
         {
             match self
                 .at(&self.misc(sp), self.param_env)
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 17022f1fd37..4caa0df58b6 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -230,11 +230,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let minimum_input_count = expected_input_tys.len();
         let provided_arg_count = provided_args.len();
 
-        let is_const_eval_select = matches!(fn_def_id, Some(def_id) if
-            self.tcx.def_kind(def_id) == hir::def::DefKind::Fn
-            && self.tcx.is_intrinsic(def_id)
-            && self.tcx.item_name(def_id) == sym::const_eval_select);
-
         // We introduce a helper function to demand that a given argument satisfy a given input
         // This is more complicated than just checking type equality, as arguments could be coerced
         // This version writes those types back so further type checking uses the narrowed types
@@ -269,30 +264,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 return Compatibility::Incompatible(coerce_error);
             }
 
-            // Check that second and third argument of `const_eval_select` must be `FnDef`, and additionally that
-            // the second argument must be `const fn`. The first argument must be a tuple, but this is already expressed
-            // in the function signature (`F: FnOnce<ARG>`), so I did not bother to add another check here.
-            //
-            // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
-            if is_const_eval_select && (1..=2).contains(&idx) {
-                if let ty::FnDef(def_id, args) = *checked_ty.kind() {
-                    if idx == 1 {
-                        if !self.tcx.is_const_fn_raw(def_id) {
-                            self.tcx.sess.emit_err(errors::ConstSelectMustBeConst {
-                                span: provided_arg.span,
-                            });
-                        } else {
-                            self.enforce_context_effects(provided_arg.span, def_id, args)
-                        }
-                    }
-                } else {
-                    self.tcx.sess.emit_err(errors::ConstSelectMustBeFn {
-                        span: provided_arg.span,
-                        ty: checked_ty,
-                    });
-                }
-            }
-
             // 3. Check if the formal type is a supertype of the checked one
             //    and register any such obligations for future type checks
             let supertype_error = self.at(&self.misc(provided_arg.span), self.param_env).sup(
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index d0b4889b45f..3ea1a52ae28 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -9,6 +9,7 @@ use std::slice;
 use arrayvec::ArrayVec;
 use smallvec::{smallvec, SmallVec};
 
+#[cfg(feature = "nightly")]
 use rustc_macros::{Decodable, Encodable};
 
 use crate::{Idx, IndexVec};
@@ -111,7 +112,8 @@ macro_rules! bit_relations_inherent_impls {
 /// to or greater than the domain size. All operations that involve two bitsets
 /// will panic if the bitsets have differing domain sizes.
 ///
-#[derive(Eq, PartialEq, Hash, Decodable, Encodable)]
+#[cfg_attr(feature = "nightly", derive(Decodable, Encodable))]
+#[derive(Eq, PartialEq, Hash)]
 pub struct BitSet<T> {
     domain_size: usize,
     words: SmallVec<[Word; 2]>,
@@ -491,10 +493,21 @@ impl<T: Idx> ChunkedBitSet<T> {
         match *chunk {
             Zeros(chunk_domain_size) => {
                 if chunk_domain_size > 1 {
-                    // We take some effort to avoid copying the words.
-                    let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed();
-                    // SAFETY: `words` can safely be all zeroes.
-                    let mut words = unsafe { words.assume_init() };
+                    #[cfg(feature = "nightly")]
+                    let mut words = {
+                        // We take some effort to avoid copying the words.
+                        let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed();
+                        // SAFETY: `words` can safely be all zeroes.
+                        unsafe { words.assume_init() }
+                    };
+                    #[cfg(not(feature = "nightly"))]
+                    let mut words = {
+                        let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
+                        // SAFETY: `words` can safely be all zeroes.
+                        let words = unsafe { words.assume_init() };
+                        // Unfortunate possibly-large copy
+                        Rc::new(words)
+                    };
                     let words_ref = Rc::get_mut(&mut words).unwrap();
 
                     let (word_index, mask) = chunk_word_index_and_mask(elem);
@@ -545,10 +558,21 @@ impl<T: Idx> ChunkedBitSet<T> {
             Zeros(_) => false,
             Ones(chunk_domain_size) => {
                 if chunk_domain_size > 1 {
-                    // We take some effort to avoid copying the words.
-                    let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed();
-                    // SAFETY: `words` can safely be all zeroes.
-                    let mut words = unsafe { words.assume_init() };
+                    #[cfg(feature = "nightly")]
+                    let mut words = {
+                        // We take some effort to avoid copying the words.
+                        let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed();
+                        // SAFETY: `words` can safely be all zeroes.
+                        unsafe { words.assume_init() }
+                    };
+                    #[cfg(not(feature = "nightly"))]
+                    let mut words = {
+                        let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
+                        // SAFETY: `words` can safely be all zeroes.
+                        let words = unsafe { words.assume_init() };
+                        // Unfortunate possibly-large copy
+                        Rc::new(words)
+                    };
                     let words_ref = Rc::get_mut(&mut words).unwrap();
 
                     // Set only the bits in use.
@@ -1564,7 +1588,8 @@ impl<T: Idx> From<BitSet<T>> for GrowableBitSet<T> {
 ///
 /// All operations that involve a row and/or column index will panic if the
 /// index exceeds the relevant bound.
-#[derive(Clone, Eq, PartialEq, Hash, Decodable, Encodable)]
+#[cfg_attr(feature = "nightly", derive(Decodable, Encodable))]
+#[derive(Clone, Eq, PartialEq, Hash)]
 pub struct BitMatrix<R: Idx, C: Idx> {
     num_rows: usize,
     num_columns: usize,
@@ -1993,7 +2018,8 @@ impl std::fmt::Debug for FiniteBitSet<u32> {
 
 /// A fixed-sized bitset type represented by an integer type. Indices outwith than the range
 /// representable by `T` are considered set.
-#[derive(Copy, Clone, Eq, PartialEq, Decodable, Encodable)]
+#[cfg_attr(feature = "nightly", derive(Decodable, Encodable))]
+#[derive(Copy, Clone, Eq, PartialEq)]
 pub struct FiniteBitSet<T: FiniteBitSetTy>(pub T);
 
 impl<T: FiniteBitSetTy> FiniteBitSet<T> {
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index c5602392c53..185e0c7d698 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -14,7 +14,6 @@
 )]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
 
-#[cfg(feature = "nightly")]
 pub mod bit_set;
 #[cfg(feature = "nightly")]
 pub mod interval;
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index c118c405c20..d396c41007b 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2653,11 +2653,6 @@ impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
         self.0.tcx
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        // Unused, only for consts which we treat as always equal
-        ty::ParamEnv::empty()
-    }
-
     fn tag(&self) -> &'static str {
         "SameTypeModuloInfer"
     }
diff --git a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
index b6e86e2b676..0fbc4a0ce50 100644
--- a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
+++ b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
@@ -31,13 +31,12 @@ use super::outlives::test_type_match;
 /// all the variables as well as a set of errors that must be reported.
 #[instrument(level = "debug", skip(region_rels, var_infos, data))]
 pub(crate) fn resolve<'tcx>(
-    param_env: ty::ParamEnv<'tcx>,
     region_rels: &RegionRelations<'_, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,
 ) -> (LexicalRegionResolutions<'tcx>, Vec<RegionResolutionError<'tcx>>) {
     let mut errors = vec![];
-    let mut resolver = LexicalResolver { param_env, region_rels, var_infos, data };
+    let mut resolver = LexicalResolver { region_rels, var_infos, data };
     let values = resolver.infer_variable_values(&mut errors);
     (values, errors)
 }
@@ -120,7 +119,6 @@ struct RegionAndOrigin<'tcx> {
 type RegionGraph<'tcx> = Graph<(), Constraint<'tcx>>;
 
 struct LexicalResolver<'cx, 'tcx> {
-    param_env: ty::ParamEnv<'tcx>,
     region_rels: &'cx RegionRelations<'cx, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,
@@ -914,12 +912,8 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         match bound {
             VerifyBound::IfEq(verify_if_eq_b) => {
                 let verify_if_eq_b = var_values.normalize(self.region_rels.tcx, *verify_if_eq_b);
-                match test_type_match::extract_verify_if_eq(
-                    self.tcx(),
-                    self.param_env,
-                    &verify_if_eq_b,
-                    generic_ty,
-                ) {
+                match test_type_match::extract_verify_if_eq(self.tcx(), &verify_if_eq_b, generic_ty)
+                {
                     Some(r) => {
                         self.bound_is_met(&VerifyBound::OutlivedBy(r), var_values, generic_ty, min)
                     }
diff --git a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
index 52cc107ae52..42e3d6cad5a 100644
--- a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
+++ b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
@@ -84,7 +84,6 @@ where
                         } else {
                             test_type_match::extract_verify_if_eq(
                                 tcx,
-                                param_env,
                                 &outlives.map_bound(|ty::OutlivesPredicate(ty, bound)| {
                                     VerifyIfEq { ty, bound }
                                 }),
diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs
index f7129a5ad89..6379f84aa25 100644
--- a/compiler/rustc_infer/src/infer/outlives/mod.rs
+++ b/compiler/rustc_infer/src/infer/outlives/mod.rs
@@ -67,7 +67,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map());
 
         let (lexical_region_resolutions, errors) =
-            lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data);
+            lexical_region_resolve::resolve(region_rels, var_infos, data);
 
         let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
         assert!(old_value.is_none());
diff --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
index 959b34aa145..236dc4ec384 100644
--- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
+++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
@@ -36,15 +36,14 @@ use crate::infer::region_constraints::VerifyIfEq;
 /// like are used. This is a particular challenge since this function is invoked
 /// very late in inference and hence cannot make use of the normal inference
 /// machinery.
-#[instrument(level = "debug", skip(tcx, param_env))]
+#[instrument(level = "debug", skip(tcx))]
 pub fn extract_verify_if_eq<'tcx>(
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     verify_if_eq_b: &ty::Binder<'tcx, VerifyIfEq<'tcx>>,
     test_ty: Ty<'tcx>,
 ) -> Option<ty::Region<'tcx>> {
     assert!(!verify_if_eq_b.has_escaping_bound_vars());
-    let mut m = MatchAgainstHigherRankedOutlives::new(tcx, param_env);
+    let mut m = MatchAgainstHigherRankedOutlives::new(tcx);
     let verify_if_eq = verify_if_eq_b.skip_binder();
     m.relate(verify_if_eq.ty, test_ty).ok()?;
 
@@ -73,10 +72,9 @@ pub fn extract_verify_if_eq<'tcx>(
 }
 
 /// True if a (potentially higher-ranked) outlives
-#[instrument(level = "debug", skip(tcx, param_env))]
+#[instrument(level = "debug", skip(tcx))]
 pub(super) fn can_match_erased_ty<'tcx>(
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     outlives_predicate: ty::Binder<'tcx, ty::TypeOutlivesPredicate<'tcx>>,
     erased_ty: Ty<'tcx>,
 ) -> bool {
@@ -87,25 +85,20 @@ pub(super) fn can_match_erased_ty<'tcx>(
         // pointless micro-optimization
         true
     } else {
-        MatchAgainstHigherRankedOutlives::new(tcx, param_env).relate(outlives_ty, erased_ty).is_ok()
+        MatchAgainstHigherRankedOutlives::new(tcx).relate(outlives_ty, erased_ty).is_ok()
     }
 }
 
 struct MatchAgainstHigherRankedOutlives<'tcx> {
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     pattern_depth: ty::DebruijnIndex,
     map: FxHashMap<ty::BoundRegion, ty::Region<'tcx>>,
 }
 
 impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> {
-    fn new(
-        tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> MatchAgainstHigherRankedOutlives<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>) -> MatchAgainstHigherRankedOutlives<'tcx> {
         MatchAgainstHigherRankedOutlives {
             tcx,
-            param_env,
             pattern_depth: ty::INNERMOST,
             map: FxHashMap::default(),
         }
@@ -144,15 +137,13 @@ impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> {
 
 impl<'tcx> TypeRelation<'tcx> for MatchAgainstHigherRankedOutlives<'tcx> {
     fn tag(&self) -> &'static str {
-        "Match"
+        "MatchAgainstHigherRankedOutlives"
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.param_env
-    }
+
     fn a_is_expected(&self) -> bool {
         true
     } // irrelevant
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index bb578a482e4..90282f58e94 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -1,7 +1,7 @@
 use crate::infer::outlives::components::{compute_alias_components_recursive, Component};
 use crate::infer::outlives::env::RegionBoundPairs;
 use crate::infer::region_constraints::VerifyIfEq;
-use crate::infer::VerifyBound;
+use crate::infer::{GenericKind, VerifyBound};
 use rustc_data_structures::sso::SsoHashSet;
 use rustc_middle::ty::GenericArg;
 use rustc_middle::ty::{self, OutlivesPredicate, Ty, TyCtxt};
@@ -240,10 +240,20 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
                     "declared_generic_bounds_from_env_for_erased_ty: region_bound_pair = {:?}",
                     (r, p)
                 );
+                // Fast path for the common case.
+                match (&p, erased_ty.kind()) {
+                    // In outlive routines, all types are expected to be fully normalized.
+                    // And therefore we can safely use structural equality for alias types.
+                    (GenericKind::Param(p1), ty::Param(p2)) if p1 == p2 => {}
+                    (GenericKind::Placeholder(p1), ty::Placeholder(p2)) if p1 == p2 => {}
+                    (GenericKind::Alias(a1), ty::Alias(_, a2)) if a1.def_id == a2.def_id => {}
+                    _ => return None,
+                }
+
                 let p_ty = p.to_ty(tcx);
                 let erased_p_ty = self.tcx.erase_regions(p_ty);
                 (erased_p_ty == erased_ty)
-                    .then_some(ty::Binder::dummy(ty::OutlivesPredicate(p.to_ty(tcx), r)))
+                    .then_some(ty::Binder::dummy(ty::OutlivesPredicate(p_ty, r)))
             });
 
         param_bounds
@@ -312,14 +322,8 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
     ) -> impl Iterator<Item = ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>>
     {
         let tcx = self.tcx;
-        let param_env = self.param_env;
         clauses.filter_map(|p| p.as_type_outlives_clause()).filter(move |outlives_predicate| {
-            super::test_type_match::can_match_erased_ty(
-                tcx,
-                param_env,
-                *outlives_predicate,
-                erased_ty,
-            )
+            super::test_type_match::can_match_erased_ty(tcx, *outlives_predicate, erased_ty)
         })
     }
 }
diff --git a/compiler/rustc_infer/src/infer/relate/combine.rs b/compiler/rustc_infer/src/infer/relate/combine.rs
index dfaca3458d6..ee911c43284 100644
--- a/compiler/rustc_infer/src/infer/relate/combine.rs
+++ b/compiler/rustc_infer/src/infer/relate/combine.rs
@@ -563,6 +563,8 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
 }
 
 pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> {
+    fn param_env(&self) -> ty::ParamEnv<'tcx>;
+
     /// Register obligations that must hold in order for this relation to hold
     fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>);
 
diff --git a/compiler/rustc_infer/src/infer/relate/equate.rs b/compiler/rustc_infer/src/infer/relate/equate.rs
index 9943c638a91..cb62f258373 100644
--- a/compiler/rustc_infer/src/infer/relate/equate.rs
+++ b/compiler/rustc_infer/src/infer/relate/equate.rs
@@ -33,10 +33,6 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
         self.fields.tcx()
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.fields.param_env
-    }
-
     fn a_is_expected(&self) -> bool {
         self.a_is_expected
     }
@@ -174,6 +170,10 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Equate<'_, '_, 'tcx> {
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.fields.param_env
+    }
+
     fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index 66f7b08ee12..665af7381dc 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -182,10 +182,6 @@ where
         self.infcx.tcx
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.delegate.param_env()
-    }
-
     fn tag(&self) -> &'static str {
         "Generalizer"
     }
diff --git a/compiler/rustc_infer/src/infer/relate/glb.rs b/compiler/rustc_infer/src/infer/relate/glb.rs
index 6a3413879c4..aa89124301e 100644
--- a/compiler/rustc_infer/src/infer/relate/glb.rs
+++ b/compiler/rustc_infer/src/infer/relate/glb.rs
@@ -32,10 +32,6 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
         self.fields.tcx()
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.fields.param_env
-    }
-
     fn a_is_expected(&self) -> bool {
         self.a_is_expected
     }
@@ -138,6 +134,10 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Glb<'combine, 'infcx,
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.fields.param_env
+    }
+
     fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
diff --git a/compiler/rustc_infer/src/infer/relate/lub.rs b/compiler/rustc_infer/src/infer/relate/lub.rs
index 41cd98ed0cf..87d777530c8 100644
--- a/compiler/rustc_infer/src/infer/relate/lub.rs
+++ b/compiler/rustc_infer/src/infer/relate/lub.rs
@@ -32,10 +32,6 @@ impl<'tcx> TypeRelation<'tcx> for Lub<'_, '_, 'tcx> {
         self.fields.tcx()
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.fields.param_env
-    }
-
     fn a_is_expected(&self) -> bool {
         self.a_is_expected
     }
@@ -138,6 +134,10 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Lub<'combine, 'infcx,
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Lub<'_, '_, 'tcx> {
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.fields.param_env
+    }
+
     fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
diff --git a/compiler/rustc_infer/src/infer/relate/nll.rs b/compiler/rustc_infer/src/infer/relate/nll.rs
index afc2a8b2f62..1ef865cfc5f 100644
--- a/compiler/rustc_infer/src/infer/relate/nll.rs
+++ b/compiler/rustc_infer/src/infer/relate/nll.rs
@@ -431,10 +431,6 @@ where
         self.infcx.tcx
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.delegate.param_env()
-    }
-
     fn tag(&self) -> &'static str {
         "nll::subtype"
     }
@@ -670,6 +666,10 @@ impl<'tcx, D> ObligationEmittingRelation<'tcx> for TypeRelating<'_, 'tcx, D>
 where
     D: TypeRelatingDelegate<'tcx>,
 {
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.delegate.param_env()
+    }
+
     fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.delegate.register_obligations(
             obligations
diff --git a/compiler/rustc_infer/src/infer/relate/sub.rs b/compiler/rustc_infer/src/infer/relate/sub.rs
index 5a623e48c93..36876acd7c0 100644
--- a/compiler/rustc_infer/src/infer/relate/sub.rs
+++ b/compiler/rustc_infer/src/infer/relate/sub.rs
@@ -39,10 +39,6 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> {
         self.fields.infcx.tcx
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.fields.param_env
-    }
-
     fn a_is_expected(&self) -> bool {
         self.a_is_expected
     }
@@ -203,6 +199,10 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> {
 }
 
 impl<'tcx> ObligationEmittingRelation<'tcx> for Sub<'_, '_, 'tcx> {
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.fields.param_env
+    }
+
     fn register_predicates(&mut self, obligations: impl IntoIterator<Item: ty::ToPredicate<'tcx>>) {
         self.fields.register_predicates(obligations);
     }
diff --git a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
index d61ec0b641c..373bc5cc581 100644
--- a/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
@@ -139,6 +139,9 @@ extern "C" void LLVMRustCoverageWriteMappingToBuffer(
            RustMappingRegions, NumMappingRegions)) {
     MappingRegions.emplace_back(
         fromRust(Region.Count), fromRust(Region.FalseCount),
+#if LLVM_VERSION_GE(18, 0)
+        coverage::CounterMappingRegion::MCDCParameters{},
+#endif
         Region.FileID, Region.ExpandedFileID,
         Region.LineStart, Region.ColumnStart, Region.LineEnd, Region.ColumnEnd,
         fromRust(Region.Kind));
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 24ab4f94d5c..281a0eafee1 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -12,7 +12,7 @@ use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};
 use rustc_hir::def::Res;
-use rustc_hir::def_id::{CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefIdMap, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefPath, DefPathData};
 use rustc_hir::diagnostic_items::DiagnosticItems;
 use rustc_index::Idx;
@@ -1200,7 +1200,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
 
     /// Iterates over the diagnostic items in the given crate.
     fn get_diagnostic_items(self) -> DiagnosticItems {
-        let mut id_to_name = FxHashMap::default();
+        let mut id_to_name = DefIdMap::default();
         let name_to_id = self
             .root
             .diagnostic_items
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index a69bff6ed8c..3a54f5f6b3d 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -69,7 +69,7 @@ use rustc_hir::def_id::{
     CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId, LocalDefIdMap, LocalDefIdSet, LocalModDefId,
 };
 use rustc_hir::lang_items::{LangItem, LanguageItems};
-use rustc_hir::{Crate, ItemLocalId, TraitCandidate};
+use rustc_hir::{Crate, ItemLocalId, ItemLocalMap, TraitCandidate};
 use rustc_index::IndexVec;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_query_system::query::{try_get_cached, CacheSelector, QueryCache, QueryMode, QueryState};
@@ -1490,7 +1490,7 @@ rustc_queries! {
         desc { "computing whether impls specialize one another" }
     }
     query in_scope_traits_map(_: hir::OwnerId)
-        -> Option<&'tcx FxHashMap<ItemLocalId, Box<[TraitCandidate]>>> {
+        -> Option<&'tcx ItemLocalMap<Box<[TraitCandidate]>>> {
         desc { "getting traits in scope at a block" }
     }
 
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index c52103eb247..734c2b61c07 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -153,7 +153,7 @@ pub enum SelectionCandidate<'tcx> {
     /// Implementation of a `Fn`-family trait by one of the anonymous
     /// types generated for a fn pointer type (e.g., `fn(int) -> int`)
     FnPointerCandidate {
-        is_const: bool,
+        fn_host_effect: ty::Const<'tcx>,
     },
 
     TraitAliasCandidate,
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
index 27a1e64a78b..048df367bd6 100644
--- a/compiler/rustc_middle/src/traits/solve.rs
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -233,6 +233,27 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for PredefinedOpaques<'tcx> {
     }
 }
 
+/// Why a specific goal has to be proven.
+///
+/// This is necessary as we treat nested goals different depending on
+/// their source.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum GoalSource {
+    Misc,
+    /// We're proving a where-bound of an impl.
+    ///
+    /// FIXME(-Znext-solver=coinductive): Explain how and why this
+    /// changes whether cycles are coinductive.
+    ///
+    /// This also impacts whether we erase constraints on overflow.
+    /// Erasing constraints is generally very useful for perf and also
+    /// results in better error messages by avoiding spurious errors.
+    /// We do not erase overflow constraints in `normalizes-to` goals unless
+    /// they are from an impl where-clause. This is necessary due to
+    /// backwards compatability, cc trait-system-refactor-initiatitive#70.
+    ImplWhereBound,
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)]
 pub enum IsNormalizesToHack {
     Yes,
diff --git a/compiler/rustc_middle/src/traits/solve/inspect.rs b/compiler/rustc_middle/src/traits/solve/inspect.rs
index 7883cd338be..77d112d0afc 100644
--- a/compiler/rustc_middle/src/traits/solve/inspect.rs
+++ b/compiler/rustc_middle/src/traits/solve/inspect.rs
@@ -19,8 +19,8 @@
 //! [canonicalized]: https://rustc-dev-guide.rust-lang.org/solve/canonicalization.html
 
 use super::{
-    CandidateSource, Canonical, CanonicalInput, Certainty, Goal, IsNormalizesToHack, NoSolution,
-    QueryInput, QueryResult,
+    CandidateSource, Canonical, CanonicalInput, Certainty, Goal, GoalSource, IsNormalizesToHack,
+    NoSolution, QueryInput, QueryResult,
 };
 use crate::{infer::canonical::CanonicalVarValues, ty};
 use format::ProofTreeFormatter;
@@ -115,7 +115,7 @@ impl Debug for Probe<'_> {
 pub enum ProbeStep<'tcx> {
     /// We added a goal to the `EvalCtxt` which will get proven
     /// the next time `EvalCtxt::try_evaluate_added_goals` is called.
-    AddGoal(CanonicalState<'tcx, Goal<'tcx, ty::Predicate<'tcx>>>),
+    AddGoal(GoalSource, CanonicalState<'tcx, Goal<'tcx, ty::Predicate<'tcx>>>),
     /// The inside of a `EvalCtxt::try_evaluate_added_goals` call.
     EvaluateGoals(AddedGoalsEvaluation<'tcx>),
     /// A call to `probe` while proving the current goal. This is
diff --git a/compiler/rustc_middle/src/traits/solve/inspect/format.rs b/compiler/rustc_middle/src/traits/solve/inspect/format.rs
index ab9e0283918..4e2207ed523 100644
--- a/compiler/rustc_middle/src/traits/solve/inspect/format.rs
+++ b/compiler/rustc_middle/src/traits/solve/inspect/format.rs
@@ -123,7 +123,13 @@ impl<'a, 'b> ProofTreeFormatter<'a, 'b> {
         self.nested(|this| {
             for step in &probe.steps {
                 match step {
-                    ProbeStep::AddGoal(goal) => writeln!(this.f, "ADDED GOAL: {goal:?}")?,
+                    ProbeStep::AddGoal(source, goal) => {
+                        let source = match source {
+                            GoalSource::Misc => "misc",
+                            GoalSource::ImplWhereBound => "impl where-bound",
+                        };
+                        writeln!(this.f, "ADDED GOAL ({source}): {goal:?}")?
+                    }
                     ProbeStep::EvaluateGoals(eval) => this.format_added_goals_evaluation(eval)?,
                     ProbeStep::NestedProbe(probe) => this.format_probe(probe)?,
                     ProbeStep::CommitIfOkStart => writeln!(this.f, "COMMIT_IF_OK START")?,
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index 85181720d17..a2794a100f1 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -20,12 +20,11 @@ use crate::ty::{self, InferConst, Ty, TyCtxt};
 /// affects any type variables or unification state.
 pub struct MatchAgainstFreshVars<'tcx> {
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
 }
 
 impl<'tcx> MatchAgainstFreshVars<'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> MatchAgainstFreshVars<'tcx> {
-        MatchAgainstFreshVars { tcx, param_env }
+    pub fn new(tcx: TyCtxt<'tcx>) -> MatchAgainstFreshVars<'tcx> {
+        MatchAgainstFreshVars { tcx }
     }
 }
 
@@ -33,13 +32,11 @@ impl<'tcx> TypeRelation<'tcx> for MatchAgainstFreshVars<'tcx> {
     fn tag(&self) -> &'static str {
         "MatchAgainstFreshVars"
     }
+
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx> {
-        self.param_env
-    }
     fn a_is_expected(&self) -> bool {
         true
     } // irrelevant
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 96de9c447b6..35c135830c3 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -192,7 +192,7 @@ pub struct ResolverAstLowering {
 
     pub next_node_id: ast::NodeId,
 
-    pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
+    pub node_id_to_def_id: NodeMap<LocalDefId>,
     pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
 
     pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index d7d9afc30e7..9d92f81db0b 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -23,8 +23,6 @@ pub enum Cause {
 pub trait TypeRelation<'tcx>: Sized {
     fn tcx(&self) -> TyCtxt<'tcx>;
 
-    fn param_env(&self) -> ty::ParamEnv<'tcx>;
-
     /// Returns a static string we can use for printouts.
     fn tag(&self) -> &'static str;
 
@@ -505,13 +503,9 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
                 Err(err) => {
                     // Check whether the lengths are both concrete/known values,
                     // but are unequal, for better diagnostics.
-                    //
-                    // It might seem dubious to eagerly evaluate these constants here,
-                    // we however cannot end up with errors in `Relate` during both
-                    // `type_of` and `predicates_of`. This means that evaluating the
-                    // constants should not cause cycle errors here.
-                    let sz_a = sz_a.try_eval_target_usize(tcx, relation.param_env());
-                    let sz_b = sz_b.try_eval_target_usize(tcx, relation.param_env());
+                    let sz_a = sz_a.try_to_target_usize(tcx);
+                    let sz_b = sz_b.try_to_target_usize(tcx);
+
                     match (sz_a, sz_b) {
                         (Some(sz_a_val), Some(sz_b_val)) if sz_a_val != sz_b_val => Err(
                             TypeError::FixedArraySize(expected_found(relation, sz_a_val, sz_b_val)),
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index 541b87af797..487b1f44b5e 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -1699,59 +1699,51 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         debug!("tested_candidates: {}", total_candidate_count - candidates.len());
         debug!("untested_candidates: {}", candidates.len());
 
-        // HACK(matthewjasper) This is a closure so that we can let the test
-        // create its blocks before the rest of the match. This currently
-        // improves the speed of llvm when optimizing long string literal
-        // matches
-        let make_target_blocks = move |this: &mut Self| -> Vec<BasicBlock> {
-            // The block that we should branch to if none of the
-            // `target_candidates` match. This is either the block where we
-            // start matching the untested candidates if there are any,
-            // otherwise it's the `otherwise_block`.
-            let remainder_start = &mut None;
-            let remainder_start =
-                if candidates.is_empty() { &mut *otherwise_block } else { remainder_start };
-
-            // For each outcome of test, process the candidates that still
-            // apply. Collect a list of blocks where control flow will
-            // branch if one of the `target_candidate` sets is not
-            // exhaustive.
-            let target_blocks: Vec<_> = target_candidates
-                .into_iter()
-                .map(|mut candidates| {
-                    if !candidates.is_empty() {
-                        let candidate_start = this.cfg.start_new_block();
-                        this.match_candidates(
-                            span,
-                            scrutinee_span,
-                            candidate_start,
-                            remainder_start,
-                            &mut *candidates,
-                            fake_borrows,
-                        );
-                        candidate_start
-                    } else {
-                        *remainder_start.get_or_insert_with(|| this.cfg.start_new_block())
-                    }
-                })
-                .collect();
-
-            if !candidates.is_empty() {
-                let remainder_start = remainder_start.unwrap_or_else(|| this.cfg.start_new_block());
-                this.match_candidates(
-                    span,
-                    scrutinee_span,
-                    remainder_start,
-                    otherwise_block,
-                    candidates,
-                    fake_borrows,
-                );
-            };
+        // The block that we should branch to if none of the
+        // `target_candidates` match. This is either the block where we
+        // start matching the untested candidates if there are any,
+        // otherwise it's the `otherwise_block`.
+        let remainder_start = &mut None;
+        let remainder_start =
+            if candidates.is_empty() { &mut *otherwise_block } else { remainder_start };
+
+        // For each outcome of test, process the candidates that still
+        // apply. Collect a list of blocks where control flow will
+        // branch if one of the `target_candidate` sets is not
+        // exhaustive.
+        let target_blocks: Vec<_> = target_candidates
+            .into_iter()
+            .map(|mut candidates| {
+                if !candidates.is_empty() {
+                    let candidate_start = self.cfg.start_new_block();
+                    self.match_candidates(
+                        span,
+                        scrutinee_span,
+                        candidate_start,
+                        remainder_start,
+                        &mut *candidates,
+                        fake_borrows,
+                    );
+                    candidate_start
+                } else {
+                    *remainder_start.get_or_insert_with(|| self.cfg.start_new_block())
+                }
+            })
+            .collect();
 
-            target_blocks
-        };
+        if !candidates.is_empty() {
+            let remainder_start = remainder_start.unwrap_or_else(|| self.cfg.start_new_block());
+            self.match_candidates(
+                span,
+                scrutinee_span,
+                remainder_start,
+                otherwise_block,
+                candidates,
+                fake_borrows,
+            );
+        }
 
-        self.perform_test(span, scrutinee_span, block, &match_place, &test, make_target_blocks);
+        self.perform_test(span, scrutinee_span, block, &match_place, &test, target_blocks);
     }
 
     /// Determine the fake borrows that are needed from a set of places that
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index d1952704da3..53e5d70f946 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -147,7 +147,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
     }
 
-    #[instrument(skip(self, make_target_blocks, place_builder), level = "debug")]
+    #[instrument(skip(self, target_blocks, place_builder), level = "debug")]
     pub(super) fn perform_test(
         &mut self,
         match_start_span: Span,
@@ -155,7 +155,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         block: BasicBlock,
         place_builder: &PlaceBuilder<'tcx>,
         test: &Test<'tcx>,
-        make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
+        target_blocks: Vec<BasicBlock>,
     ) {
         let place = place_builder.to_place(self);
         let place_ty = place.ty(&self.local_decls, self.tcx);
@@ -164,7 +164,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let source_info = self.source_info(test.span);
         match test.kind {
             TestKind::Switch { adt_def, ref variants } => {
-                let target_blocks = make_target_blocks(self);
                 // Variants is a BitVec of indexes into adt_def.variants.
                 let num_enum_variants = adt_def.variants().len();
                 debug_assert_eq!(target_blocks.len(), num_enum_variants + 1);
@@ -210,7 +209,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
 
             TestKind::SwitchInt { switch_ty, ref options } => {
-                let target_blocks = make_target_blocks(self);
                 let terminator = if *switch_ty.kind() == ty::Bool {
                     assert!(!options.is_empty() && options.len() <= 2);
                     let [first_bb, second_bb] = *target_blocks else {
@@ -240,6 +238,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
             TestKind::Eq { value, ty } => {
                 let tcx = self.tcx;
+                let [success_block, fail_block] = *target_blocks else {
+                    bug!("`TestKind::Eq` should have two target blocks")
+                };
                 if let ty::Adt(def, _) = ty.kind()
                     && Some(def.did()) == tcx.lang_items().string()
                 {
@@ -280,38 +281,43 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     );
                     self.non_scalar_compare(
                         eq_block,
-                        make_target_blocks,
+                        success_block,
+                        fail_block,
                         source_info,
                         value,
                         ref_str,
                         ref_str_ty,
                     );
-                    return;
-                }
-                if !ty.is_scalar() {
+                } else if !ty.is_scalar() {
                     // Use `PartialEq::eq` instead of `BinOp::Eq`
                     // (the binop can only handle primitives)
                     self.non_scalar_compare(
                         block,
-                        make_target_blocks,
+                        success_block,
+                        fail_block,
                         source_info,
                         value,
                         place,
                         ty,
                     );
-                } else if let [success, fail] = *make_target_blocks(self) {
+                } else {
                     assert_eq!(value.ty(), ty);
                     let expect = self.literal_operand(test.span, value);
                     let val = Operand::Copy(place);
-                    self.compare(block, success, fail, source_info, BinOp::Eq, expect, val);
-                } else {
-                    bug!("`TestKind::Eq` should have two target blocks");
+                    self.compare(
+                        block,
+                        success_block,
+                        fail_block,
+                        source_info,
+                        BinOp::Eq,
+                        expect,
+                        val,
+                    );
                 }
             }
 
             TestKind::Range(ref range) => {
                 let lower_bound_success = self.cfg.start_new_block();
-                let target_blocks = make_target_blocks(self);
 
                 // Test `val` by computing `lo <= val && val <= hi`, using primitive comparisons.
                 // FIXME: skip useless comparison when the range is half-open.
@@ -341,8 +347,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
 
             TestKind::Len { len, op } => {
-                let target_blocks = make_target_blocks(self);
-
                 let usize_ty = self.tcx.types.usize;
                 let actual = self.temp(usize_ty, test.span);
 
@@ -406,7 +410,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn non_scalar_compare(
         &mut self,
         block: BasicBlock,
-        make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
+        success_block: BasicBlock,
+        fail_block: BasicBlock,
         source_info: SourceInfo,
         value: Const<'tcx>,
         mut val: Place<'tcx>,
@@ -531,9 +536,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         );
         self.diverge_from(block);
 
-        let [success_block, fail_block] = *make_target_blocks(self) else {
-            bug!("`TestKind::Eq` should have two target blocks")
-        };
         // check the result
         self.cfg.terminate(
             eq_block,
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index db2624cac02..c66687330dc 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -6,7 +6,7 @@ use rustc_errors::{
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
-use rustc_pattern_analysis::{cx::MatchCheckCtxt, errors::Uncovered};
+use rustc_pattern_analysis::{errors::Uncovered, rustc::RustcMatchCheckCtxt};
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 
@@ -454,7 +454,7 @@ pub enum UnusedUnsafeEnclosing {
 }
 
 pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'p, 'tcx, 'm> {
-    pub cx: &'m MatchCheckCtxt<'p, 'tcx>,
+    pub cx: &'m RustcMatchCheckCtxt<'p, 'tcx>,
     pub expr_span: Span,
     pub span: Span,
     pub ty: Ty<'tcx>,
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 792a443c908..c435f4023af 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -1,13 +1,13 @@
-use rustc_pattern_analysis::constructor::Constructor;
-use rustc_pattern_analysis::cx::MatchCheckCtxt;
 use rustc_pattern_analysis::errors::Uncovered;
-use rustc_pattern_analysis::pat::{DeconstructedPat, WitnessPat};
-use rustc_pattern_analysis::usefulness::{Usefulness, UsefulnessReport};
+use rustc_pattern_analysis::rustc::{
+    Constructor, DeconstructedPat, RustcMatchCheckCtxt as MatchCheckCtxt, Usefulness,
+    UsefulnessReport, WitnessPat,
+};
 use rustc_pattern_analysis::{analyze_match, MatchArm};
 
 use crate::errors::*;
 
-use rustc_arena::TypedArena;
+use rustc_arena::{DroplessArena, TypedArena};
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::stack::ensure_sufficient_stack;
@@ -31,6 +31,7 @@ pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), Err
     let (thir, expr) = tcx.thir_body(def_id)?;
     let thir = thir.borrow();
     let pattern_arena = TypedArena::default();
+    let dropless_arena = DroplessArena::default();
     let mut visitor = MatchVisitor {
         tcx,
         thir: &*thir,
@@ -38,6 +39,7 @@ pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), Err
         lint_level: tcx.local_def_id_to_hir_id(def_id),
         let_source: LetSource::None,
         pattern_arena: &pattern_arena,
+        dropless_arena: &dropless_arena,
         error: Ok(()),
     };
     visitor.visit_expr(&thir[expr]);
@@ -82,6 +84,7 @@ struct MatchVisitor<'thir, 'p, 'tcx> {
     lint_level: HirId,
     let_source: LetSource,
     pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
+    dropless_arena: &'p DroplessArena,
     /// Tracks if we encountered an error while checking this body. That the first function to
     /// report it stores it here. Some functions return `Result` to allow callers to short-circuit
     /// on error, but callers don't need to store it here again.
@@ -382,6 +385,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
             param_env: self.param_env,
             module: self.tcx.parent_module(self.lint_level).to_def_id(),
             pattern_arena: self.pattern_arena,
+            dropless_arena: self.dropless_arena,
             match_lint_level: self.lint_level,
             whole_match_span,
             scrut_span,
@@ -425,7 +429,8 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
             let arm = &self.thir.arms[arm];
             let got_error = self.with_lint_level(arm.lint_level, |this| {
                 let Ok(pat) = this.lower_pattern(&cx, &arm.pattern) else { return true };
-                let arm = MatchArm { pat, hir_id: this.lint_level, has_guard: arm.guard.is_some() };
+                let arm =
+                    MatchArm { pat, arm_data: this.lint_level, has_guard: arm.guard.is_some() };
                 tarms.push(arm);
                 false
             });
@@ -548,7 +553,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
     ) -> Result<(MatchCheckCtxt<'p, 'tcx>, UsefulnessReport<'p, 'tcx>), ErrorGuaranteed> {
         let cx = self.new_cx(refutability, None, scrut, pat.span);
         let pat = self.lower_pattern(&cx, pat)?;
-        let arms = [MatchArm { pat, hir_id: self.lint_level, has_guard: false }];
+        let arms = [MatchArm { pat, arm_data: self.lint_level, has_guard: false }];
         let report = analyze_match(&cx, &arms, pat.ty());
         Ok((cx, report))
     }
@@ -847,34 +852,34 @@ fn report_arm_reachability<'p, 'tcx>(
         );
     };
 
-    use Usefulness::*;
     let mut catchall = None;
     for (arm, is_useful) in report.arm_usefulness.iter() {
         match is_useful {
-            Redundant => report_unreachable_pattern(arm.pat.span(), arm.hir_id, catchall),
-            Useful(redundant_spans) if redundant_spans.is_empty() => {}
+            Usefulness::Redundant => {
+                report_unreachable_pattern(*arm.pat.data(), arm.arm_data, catchall)
+            }
+            Usefulness::Useful(redundant_subpats) if redundant_subpats.is_empty() => {}
             // The arm is reachable, but contains redundant subpatterns (from or-patterns).
-            Useful(redundant_spans) => {
-                let mut redundant_spans = redundant_spans.clone();
+            Usefulness::Useful(redundant_subpats) => {
+                let mut redundant_subpats = redundant_subpats.clone();
                 // Emit lints in the order in which they occur in the file.
-                redundant_spans.sort_unstable();
-                for span in redundant_spans {
-                    report_unreachable_pattern(span, arm.hir_id, None);
+                redundant_subpats.sort_unstable_by_key(|pat| pat.data());
+                for pat in redundant_subpats {
+                    report_unreachable_pattern(*pat.data(), arm.arm_data, None);
                 }
             }
         }
         if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
-            catchall = Some(arm.pat.span());
+            catchall = Some(*arm.pat.data());
         }
     }
 }
 
 /// Checks for common cases of "catchall" patterns that may not be intended as such.
 fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
-    use Constructor::*;
     match pat.ctor() {
-        Wildcard => true,
-        Single => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
+        Constructor::Wildcard => true,
+        Constructor::Struct | Constructor::Ref => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
         _ => false,
     }
 }
@@ -885,7 +890,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
     thir: &Thir<'tcx>,
     scrut_ty: Ty<'tcx>,
     sp: Span,
-    witnesses: Vec<WitnessPat<'tcx>>,
+    witnesses: Vec<WitnessPat<'p, 'tcx>>,
     arms: &[ArmId],
     expr_span: Span,
 ) -> ErrorGuaranteed {
@@ -1082,10 +1087,10 @@ fn report_non_exhaustive_match<'p, 'tcx>(
 
 fn joined_uncovered_patterns<'p, 'tcx>(
     cx: &MatchCheckCtxt<'p, 'tcx>,
-    witnesses: &[WitnessPat<'tcx>],
+    witnesses: &[WitnessPat<'p, 'tcx>],
 ) -> String {
     const LIMIT: usize = 3;
-    let pat_to_str = |pat: &WitnessPat<'tcx>| cx.hoist_witness_pat(pat).to_string();
+    let pat_to_str = |pat: &WitnessPat<'p, 'tcx>| cx.hoist_witness_pat(pat).to_string();
     match witnesses {
         [] => bug!(),
         [witness] => format!("`{}`", cx.hoist_witness_pat(witness)),
@@ -1103,7 +1108,7 @@ fn joined_uncovered_patterns<'p, 'tcx>(
 
 fn collect_non_exhaustive_tys<'tcx>(
     cx: &MatchCheckCtxt<'_, 'tcx>,
-    pat: &WitnessPat<'tcx>,
+    pat: &WitnessPat<'_, 'tcx>,
     non_exhaustive_tys: &mut FxIndexSet<Ty<'tcx>>,
 ) {
     if matches!(pat.ctor(), Constructor::NonExhaustive) {
@@ -1122,7 +1127,7 @@ fn collect_non_exhaustive_tys<'tcx>(
 fn report_adt_defined_here<'tcx>(
     tcx: TyCtxt<'tcx>,
     ty: Ty<'tcx>,
-    witnesses: &[WitnessPat<'tcx>],
+    witnesses: &[WitnessPat<'_, 'tcx>],
     point_at_non_local_ty: bool,
 ) -> Option<AdtDefinedHere<'tcx>> {
     let ty = ty.peel_refs();
@@ -1144,15 +1149,14 @@ fn report_adt_defined_here<'tcx>(
     Some(AdtDefinedHere { adt_def_span, ty, variants })
 }
 
-fn maybe_point_at_variant<'a, 'tcx: 'a>(
+fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'p>(
     tcx: TyCtxt<'tcx>,
     def: AdtDef<'tcx>,
-    patterns: impl Iterator<Item = &'a WitnessPat<'tcx>>,
+    patterns: impl Iterator<Item = &'a WitnessPat<'p, 'tcx>>,
 ) -> Vec<Span> {
-    use Constructor::*;
     let mut covered = vec![];
     for pattern in patterns {
-        if let Variant(variant_index) = pattern.ctor() {
+        if let Constructor::Variant(variant_index) = pattern.ctor() {
             if let ty::Adt(this_def, _) = pattern.ty().kind()
                 && this_def.did() != def.did()
             {
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 9e3637ea9f3..c077e0a83a1 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -10,13 +10,13 @@ use crate::errors::{
     ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
     DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
     GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
-    HelpIdentifierStartsWithNumber, InInTypo, IncorrectAwait, IncorrectSemicolon,
-    IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType, QuestionMarkInTypeSugg,
-    SelfParamNotFirst, StructLiteralBodyWithoutPath, StructLiteralBodyWithoutPathSugg,
-    StructLiteralNeedingParens, StructLiteralNeedingParensSugg, SuggAddMissingLetStmt,
-    SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator, UnexpectedConstInGenericParam,
-    UnexpectedConstParamDeclaration, UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets,
-    UseEqInstead, WrapType,
+    HelpIdentifierStartsWithNumber, HelpUseLatestEdition, InInTypo, IncorrectAwait,
+    IncorrectSemicolon, IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType,
+    QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
+    StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens, StructLiteralNeedingParensSugg,
+    SuggAddMissingLetStmt, SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator,
+    UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
+    UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead, WrapType,
 };
 use crate::fluent_generated as fluent;
 use crate::parser;
@@ -640,6 +640,28 @@ impl<'a> Parser<'a> {
             }
         }
 
+        // Try to detect an intended c-string literal while using a pre-2021 edition. The heuristic
+        // here is to identify a cooked, uninterpolated `c` id immediately followed by a string, or
+        // a cooked, uninterpolated `cr` id immediately followed by a string or a `#`, in an edition
+        // where c-string literals are not allowed. There is the very slight possibility of a false
+        // positive for a `cr#` that wasn't intended to start a c-string literal, but identifying
+        // that in the parser requires unbounded lookahead, so we only add a hint to the existing
+        // error rather than replacing it entirely.
+        if ((self.prev_token.kind == TokenKind::Ident(sym::c, false)
+            && matches!(&self.token.kind, TokenKind::Literal(token::Lit { kind: token::Str, .. })))
+            || (self.prev_token.kind == TokenKind::Ident(sym::cr, false)
+                && matches!(
+                    &self.token.kind,
+                    TokenKind::Literal(token::Lit { kind: token::Str, .. }) | token::Pound
+                )))
+            && self.prev_token.span.hi() == self.token.span.lo()
+            && !self.token.span.at_least_rust_2021()
+        {
+            err.note("you may be trying to write a c-string literal");
+            err.note("c-string literals require Rust 2021 or later");
+            HelpUseLatestEdition::new().add_to_diagnostic(&mut err);
+        }
+
         // `pub` may be used for an item or `pub(crate)`
         if self.prev_token.is_ident_named(sym::public)
             && (self.token.can_begin_item()
diff --git a/compiler/rustc_passes/src/diagnostic_items.rs b/compiler/rustc_passes/src/diagnostic_items.rs
index 5f767c9acaa..d8b9f4fae87 100644
--- a/compiler/rustc_passes/src/diagnostic_items.rs
+++ b/compiler/rustc_passes/src/diagnostic_items.rs
@@ -83,9 +83,6 @@ fn all_diagnostic_items(tcx: TyCtxt<'_>, (): ()) -> DiagnosticItems {
 
     // Collect diagnostic items in other crates.
     for &cnum in tcx.crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)) {
-        // We are collecting many DiagnosticItems hash maps into one
-        // DiagnosticItems hash map. The iteration order does not matter.
-        #[allow(rustc::potential_query_instability)]
         for (&name, &def_id) in &tcx.diagnostic_items(cnum).name_to_id {
             collect_item(tcx, &mut items, name, def_id);
         }
diff --git a/compiler/rustc_pattern_analysis/Cargo.toml b/compiler/rustc_pattern_analysis/Cargo.toml
index 0639944a45c..908d00cf105 100644
--- a/compiler/rustc_pattern_analysis/Cargo.toml
+++ b/compiler/rustc_pattern_analysis/Cargo.toml
@@ -6,17 +6,40 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 rustc_apfloat = "0.2.0"
-rustc_arena = { path = "../rustc_arena" }
-rustc_data_structures = { path = "../rustc_data_structures" }
-rustc_errors = { path = "../rustc_errors" }
-rustc_fluent_macro = { path = "../rustc_fluent_macro" }
-rustc_hir = { path = "../rustc_hir" }
-rustc_index = { path = "../rustc_index" }
-rustc_macros = { path = "../rustc_macros" }
-rustc_middle = { path = "../rustc_middle" }
-rustc_session = { path = "../rustc_session" }
-rustc_span = { path = "../rustc_span" }
-rustc_target = { path = "../rustc_target" }
-smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
+rustc_arena = { path = "../rustc_arena", optional = true }
+rustc_data_structures = { path = "../rustc_data_structures", optional = true }
+rustc_errors = { path = "../rustc_errors", optional = true }
+rustc_fluent_macro = { path = "../rustc_fluent_macro", optional = true }
+rustc_hir = { path = "../rustc_hir", optional = true }
+rustc_index = { path = "../rustc_index", default-features = false }
+rustc_macros = { path = "../rustc_macros", optional = true }
+rustc_middle = { path = "../rustc_middle", optional = true }
+rustc_session = { path = "../rustc_session", optional = true }
+rustc_span = { path = "../rustc_span", optional = true }
+rustc_target = { path = "../rustc_target", optional = true }
+smallvec = { version = "1.8.1", features = ["union"] }
 tracing = "0.1"
+typed-arena = { version = "2.0.2", optional = true }
 # tidy-alphabetical-end
+
+[features]
+default = ["rustc"]
+# It's not possible to only enable the `typed_arena` dependency when the `rustc` feature is off, so
+# we use another feature instead. The crate won't compile if one of these isn't enabled.
+rustc = [
+    "dep:rustc_arena",
+    "dep:rustc_data_structures",
+    "dep:rustc_errors",
+    "dep:rustc_fluent_macro",
+    "dep:rustc_hir",
+    "dep:rustc_macros",
+    "dep:rustc_middle",
+    "dep:rustc_session",
+    "dep:rustc_span",
+    "dep:rustc_target",
+    "smallvec/may_dangle",
+    "rustc_index/nightly",
+]
+stable = [
+    "dep:typed-arena",
+]
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index 6486ad8b483..af0a7497a34 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -40,7 +40,7 @@
 //! - That have no non-trivial intersection with any of the constructors in the column (i.e. they're
 //!     each either disjoint with or covered by any given column constructor).
 //!
-//! We compute this in two steps: first [`crate::cx::MatchCheckCtxt::ctors_for_ty`] determines the
+//! We compute this in two steps: first [`TypeCx::ctors_for_ty`] determines the
 //! set of all possible constructors for the type. Then [`ConstructorSet::split`] looks at the
 //! column of constructors and splits the set into groups accordingly. The precise invariants of
 //! [`ConstructorSet::split`] is described in [`SplitConstructorSet`].
@@ -136,7 +136,7 @@
 //! the algorithm can't distinguish them from a nonempty constructor. The only known case where this
 //! could happen is the `[..]` pattern on `[!; N]` with `N > 0` so we must take care to not emit it.
 //!
-//! This is all handled by [`crate::cx::MatchCheckCtxt::ctors_for_ty`] and
+//! This is all handled by [`TypeCx::ctors_for_ty`] and
 //! [`ConstructorSet::split`]. The invariants of [`SplitConstructorSet`] are also of interest.
 //!
 //!
@@ -155,17 +155,15 @@ use std::iter::once;
 use smallvec::SmallVec;
 
 use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS};
-use rustc_data_structures::fx::FxHashSet;
-use rustc_hir::RangeEnd;
+use rustc_index::bit_set::{BitSet, GrowableBitSet};
 use rustc_index::IndexVec;
-use rustc_middle::mir::Const;
-use rustc_target::abi::VariantIdx;
 
 use self::Constructor::*;
 use self::MaybeInfiniteInt::*;
 use self::SliceKind::*;
 
-use crate::usefulness::PatCtxt;
+use crate::usefulness::PlaceCtxt;
+use crate::TypeCx;
 
 /// Whether we have seen a constructor in the column or not.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
@@ -174,6 +172,21 @@ enum Presence {
     Seen,
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum RangeEnd {
+    Included,
+    Excluded,
+}
+
+impl fmt::Display for RangeEnd {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match self {
+            RangeEnd::Included => "..=",
+            RangeEnd::Excluded => "..",
+        })
+    }
+}
+
 /// A possibly infinite integer. Values are encoded such that the ordering on `u128` matches the
 /// natural order on the original type. For example, `-128i8` is encoded as `0` and `127i8` as
 /// `255`. See `signed_bias` for details.
@@ -221,7 +234,7 @@ impl MaybeInfiniteInt {
         match self {
             Finite(n) => match n.checked_sub(1) {
                 Some(m) => Finite(m),
-                None => bug!(),
+                None => panic!("Called `MaybeInfiniteInt::minus_one` on 0"),
             },
             JustAfterMax => Finite(u128::MAX),
             x => x,
@@ -234,7 +247,7 @@ impl MaybeInfiniteInt {
                 Some(m) => Finite(m),
                 None => JustAfterMax,
             },
-            JustAfterMax => bug!(),
+            JustAfterMax => panic!("Called `MaybeInfiniteInt::plus_one` on u128::MAX+1"),
             x => x,
         }
     }
@@ -253,7 +266,7 @@ pub struct IntRange {
 
 impl IntRange {
     /// Best effort; will not know that e.g. `255u8..` is a singleton.
-    pub(crate) fn is_singleton(&self) -> bool {
+    pub fn is_singleton(&self) -> bool {
         // Since `lo` and `hi` can't be the same `Infinity` and `plus_one` never changes from finite
         // to infinite, this correctly only detects ranges that contain exacly one `Finite(x)`.
         self.lo.plus_one() == self.hi
@@ -271,7 +284,7 @@ impl IntRange {
         }
         if lo >= hi {
             // This should have been caught earlier by E0030.
-            bug!("malformed range pattern: {lo:?}..{hi:?}");
+            panic!("malformed range pattern: {lo:?}..{hi:?}");
         }
         IntRange { lo, hi }
     }
@@ -432,7 +445,7 @@ impl Slice {
         let kind = match (array_len, kind) {
             // If the middle `..` has length 0, we effectively have a fixed-length pattern.
             (Some(len), VarLen(prefix, suffix)) if prefix + suffix == len => FixedLen(len),
-            (Some(len), VarLen(prefix, suffix)) if prefix + suffix > len => bug!(
+            (Some(len), VarLen(prefix, suffix)) if prefix + suffix > len => panic!(
                 "Slice pattern of length {} longer than its array length {len}",
                 prefix + suffix
             ),
@@ -532,7 +545,7 @@ impl Slice {
         // therefore `Presence::Seen` in the column.
         let mut min_var_len = usize::MAX;
         // Tracks the fixed-length slices we've seen, to mark them as `Presence::Seen`.
-        let mut seen_fixed_lens = FxHashSet::default();
+        let mut seen_fixed_lens = GrowableBitSet::new_empty();
         match &mut max_slice {
             VarLen(max_prefix_len, max_suffix_len) => {
                 // A length larger than any fixed-length slice encountered.
@@ -600,7 +613,7 @@ impl Slice {
 
         smaller_lengths.map(FixedLen).chain(once(max_slice)).map(move |kind| {
             let arity = kind.arity();
-            let seen = if min_var_len <= arity || seen_fixed_lens.contains(&arity) {
+            let seen = if min_var_len <= arity || seen_fixed_lens.contains(arity) {
                 Presence::Seen
             } else {
                 Presence::Unseen
@@ -630,12 +643,17 @@ impl OpaqueId {
 /// constructor. `Constructor::apply` reconstructs the pattern from a pair of `Constructor` and
 /// `Fields`.
 #[derive(Clone, Debug, PartialEq)]
-pub enum Constructor<'tcx> {
-    /// The constructor for patterns that have a single constructor, like tuples, struct patterns,
-    /// and references. Fixed-length arrays are treated separately with `Slice`.
-    Single,
+pub enum Constructor<Cx: TypeCx> {
+    /// Tuples and structs.
+    Struct,
     /// Enum variants.
-    Variant(VariantIdx),
+    Variant(Cx::VariantIdx),
+    /// References
+    Ref,
+    /// Array and slice patterns.
+    Slice(Slice),
+    /// Union field accesses.
+    UnionField,
     /// Booleans
     Bool(bool),
     /// Ranges of integer literal values (`2`, `2..=5` or `2..5`).
@@ -644,9 +662,7 @@ pub enum Constructor<'tcx> {
     F32Range(IeeeFloat<SingleS>, IeeeFloat<SingleS>, RangeEnd),
     F64Range(IeeeFloat<DoubleS>, IeeeFloat<DoubleS>, RangeEnd),
     /// String literals. Strings are not quite the same as `&[u8]` so we treat them separately.
-    Str(Const<'tcx>),
-    /// Array and slice patterns.
-    Slice(Slice),
+    Str(Cx::StrLit),
     /// Constants that must not be matched structurally. They are treated as black boxes for the
     /// purposes of exhaustiveness: we must not inspect them, and they don't count towards making a
     /// match exhaustive.
@@ -669,12 +685,12 @@ pub enum Constructor<'tcx> {
     Missing,
 }
 
-impl<'tcx> Constructor<'tcx> {
+impl<Cx: TypeCx> Constructor<Cx> {
     pub(crate) fn is_non_exhaustive(&self) -> bool {
         matches!(self, NonExhaustive)
     }
 
-    pub(crate) fn as_variant(&self) -> Option<VariantIdx> {
+    pub(crate) fn as_variant(&self) -> Option<Cx::VariantIdx> {
         match self {
             Variant(i) => Some(*i),
             _ => None,
@@ -701,8 +717,8 @@ impl<'tcx> Constructor<'tcx> {
 
     /// The number of fields for this constructor. This must be kept in sync with
     /// `Fields::wildcards`.
-    pub(crate) fn arity(&self, pcx: &PatCtxt<'_, '_, 'tcx>) -> usize {
-        pcx.cx.ctor_arity(self, pcx.ty)
+    pub(crate) fn arity(&self, pcx: &PlaceCtxt<'_, '_, Cx>) -> usize {
+        pcx.ctor_arity(self)
     }
 
     /// Returns whether `self` is covered by `other`, i.e. whether `self` is a subset of `other`.
@@ -710,20 +726,20 @@ impl<'tcx> Constructor<'tcx> {
     /// this checks for inclusion.
     // We inline because this has a single call site in `Matrix::specialize_constructor`.
     #[inline]
-    pub(crate) fn is_covered_by<'p>(&self, pcx: &PatCtxt<'_, 'p, 'tcx>, other: &Self) -> bool {
+    pub(crate) fn is_covered_by<'p>(&self, pcx: &PlaceCtxt<'_, 'p, Cx>, other: &Self) -> bool {
         match (self, other) {
-            (Wildcard, _) => {
-                span_bug!(
-                    pcx.cx.scrut_span,
-                    "Constructor splitting should not have returned `Wildcard`"
-                )
-            }
+            (Wildcard, _) => pcx
+                .mcx
+                .tycx
+                .bug(format_args!("Constructor splitting should not have returned `Wildcard`")),
             // Wildcards cover anything
             (_, Wildcard) => true,
             // Only a wildcard pattern can match these special constructors.
             (Missing { .. } | NonExhaustive | Hidden, _) => false,
 
-            (Single, Single) => true,
+            (Struct, Struct) => true,
+            (Ref, Ref) => true,
+            (UnionField, UnionField) => true,
             (Variant(self_id), Variant(other_id)) => self_id == other_id,
             (Bool(self_b), Bool(other_b)) => self_b == other_b,
 
@@ -756,12 +772,9 @@ impl<'tcx> Constructor<'tcx> {
             (Opaque(self_id), Opaque(other_id)) => self_id == other_id,
             (Opaque(..), _) | (_, Opaque(..)) => false,
 
-            _ => span_bug!(
-                pcx.cx.scrut_span,
-                "trying to compare incompatible constructors {:?} and {:?}",
-                self,
-                other
-            ),
+            _ => pcx.mcx.tycx.bug(format_args!(
+                "trying to compare incompatible constructors {self:?} and {other:?}"
+            )),
         }
     }
 }
@@ -785,13 +798,16 @@ pub enum VariantVisibility {
 /// In terms of division of responsibility, [`ConstructorSet::split`] handles all of the
 /// `exhaustive_patterns` feature.
 #[derive(Debug)]
-pub enum ConstructorSet {
-    /// The type has a single constructor, e.g. `&T` or a struct. `empty` tracks whether the
-    /// constructor is empty.
-    Single { empty: bool },
+pub enum ConstructorSet<Cx: TypeCx> {
+    /// The type is a tuple or struct. `empty` tracks whether the type is empty.
+    Struct { empty: bool },
     /// This type has the following list of constructors. If `variants` is empty and
     /// `non_exhaustive` is false, don't use this; use `NoConstructors` instead.
-    Variants { variants: IndexVec<VariantIdx, VariantVisibility>, non_exhaustive: bool },
+    Variants { variants: IndexVec<Cx::VariantIdx, VariantVisibility>, non_exhaustive: bool },
+    /// The type is `&T`.
+    Ref,
+    /// The type is a union.
+    Union,
     /// Booleans.
     Bool,
     /// The type is spanned by integer values. The range or ranges give the set of allowed values.
@@ -830,25 +846,25 @@ pub enum ConstructorSet {
 /// of the `ConstructorSet` for the type, yet if we forgot to include them in `present` we would be
 /// ignoring any row with `Opaque`s in the algorithm. Hence the importance of point 4.
 #[derive(Debug)]
-pub(crate) struct SplitConstructorSet<'tcx> {
-    pub(crate) present: SmallVec<[Constructor<'tcx>; 1]>,
-    pub(crate) missing: Vec<Constructor<'tcx>>,
-    pub(crate) missing_empty: Vec<Constructor<'tcx>>,
+pub(crate) struct SplitConstructorSet<Cx: TypeCx> {
+    pub(crate) present: SmallVec<[Constructor<Cx>; 1]>,
+    pub(crate) missing: Vec<Constructor<Cx>>,
+    pub(crate) missing_empty: Vec<Constructor<Cx>>,
 }
 
-impl ConstructorSet {
+impl<Cx: TypeCx> ConstructorSet<Cx> {
     /// This analyzes a column of constructors to 1/ determine which constructors of the type (if
     /// any) are missing; 2/ split constructors to handle non-trivial intersections e.g. on ranges
     /// or slices. This can get subtle; see [`SplitConstructorSet`] for details of this operation
     /// and its invariants.
     #[instrument(level = "debug", skip(self, pcx, ctors), ret)]
-    pub(crate) fn split<'a, 'tcx>(
+    pub(crate) fn split<'a>(
         &self,
-        pcx: &PatCtxt<'_, '_, 'tcx>,
-        ctors: impl Iterator<Item = &'a Constructor<'tcx>> + Clone,
-    ) -> SplitConstructorSet<'tcx>
+        pcx: &PlaceCtxt<'_, '_, Cx>,
+        ctors: impl Iterator<Item = &'a Constructor<Cx>> + Clone,
+    ) -> SplitConstructorSet<Cx>
     where
-        'tcx: 'a,
+        Cx: 'a,
     {
         let mut present: SmallVec<[_; 1]> = SmallVec::new();
         // Empty constructors found missing.
@@ -866,22 +882,39 @@ impl ConstructorSet {
         }
 
         match self {
-            ConstructorSet::Single { empty } => {
+            ConstructorSet::Struct { empty } => {
                 if !seen.is_empty() {
-                    present.push(Single);
+                    present.push(Struct);
                 } else if *empty {
-                    missing_empty.push(Single);
+                    missing_empty.push(Struct);
+                } else {
+                    missing.push(Struct);
+                }
+            }
+            ConstructorSet::Ref => {
+                if !seen.is_empty() {
+                    present.push(Ref);
                 } else {
-                    missing.push(Single);
+                    missing.push(Ref);
+                }
+            }
+            ConstructorSet::Union => {
+                if !seen.is_empty() {
+                    present.push(UnionField);
+                } else {
+                    missing.push(UnionField);
                 }
             }
             ConstructorSet::Variants { variants, non_exhaustive } => {
-                let seen_set: FxHashSet<_> = seen.iter().map(|c| c.as_variant().unwrap()).collect();
+                let mut seen_set: BitSet<_> = BitSet::new_empty(variants.len());
+                for idx in seen.iter().map(|c| c.as_variant().unwrap()) {
+                    seen_set.insert(idx);
+                }
                 let mut skipped_a_hidden_variant = false;
 
                 for (idx, visibility) in variants.iter_enumerated() {
                     let ctor = Variant(idx);
-                    if seen_set.contains(&idx) {
+                    if seen_set.contains(idx) {
                         present.push(ctor);
                     } else {
                         // We only put visible variants directly into `missing`.
@@ -975,8 +1008,8 @@ impl ConstructorSet {
         // We have now grouped all the constructors into 3 buckets: present, missing, missing_empty.
         // In the absence of the `exhaustive_patterns` feature however, we don't count nested empty
         // types as empty. Only non-nested `!` or `enum Foo {}` are considered empty.
-        if !pcx.cx.tcx.features().exhaustive_patterns
-            && !(pcx.is_top_level && matches!(self, Self::NoConstructors))
+        if !pcx.mcx.tycx.is_exhaustive_patterns_feature_on()
+            && !(pcx.is_scrutinee && matches!(self, Self::NoConstructors))
         {
             // Treat all missing constructors as nonempty.
             // This clears `missing_empty`.
diff --git a/compiler/rustc_pattern_analysis/src/errors.rs b/compiler/rustc_pattern_analysis/src/errors.rs
index 0efa8a0ec08..88770b0c43b 100644
--- a/compiler/rustc_pattern_analysis/src/errors.rs
+++ b/compiler/rustc_pattern_analysis/src/errors.rs
@@ -1,11 +1,11 @@
-use crate::{cx::MatchCheckCtxt, pat::WitnessPat};
-
 use rustc_errors::{AddToDiagnostic, Diagnostic, SubdiagnosticMessage};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::thir::Pat;
 use rustc_middle::ty::Ty;
 use rustc_span::Span;
 
+use crate::rustc::{RustcMatchCheckCtxt, WitnessPat};
+
 #[derive(Subdiagnostic)]
 #[label(pattern_analysis_uncovered)]
 pub struct Uncovered<'tcx> {
@@ -21,8 +21,8 @@ pub struct Uncovered<'tcx> {
 impl<'tcx> Uncovered<'tcx> {
     pub fn new<'p>(
         span: Span,
-        cx: &MatchCheckCtxt<'p, 'tcx>,
-        witnesses: Vec<WitnessPat<'tcx>>,
+        cx: &RustcMatchCheckCtxt<'p, 'tcx>,
+        witnesses: Vec<WitnessPat<'p, 'tcx>>,
     ) -> Self {
         let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap());
         Self {
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index 07730aa49d3..785a60e9978 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -1,54 +1,133 @@
 //! Analysis of patterns, notably match exhaustiveness checking.
 
 pub mod constructor;
-pub mod cx;
+#[cfg(feature = "rustc")]
 pub mod errors;
+#[cfg(feature = "rustc")]
 pub(crate) mod lints;
 pub mod pat;
+#[cfg(feature = "rustc")]
+pub mod rustc;
 pub mod usefulness;
 
 #[macro_use]
 extern crate tracing;
+#[cfg(feature = "rustc")]
 #[macro_use]
 extern crate rustc_middle;
 
+#[cfg(feature = "rustc")]
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
-use lints::PatternColumn;
-use rustc_hir::HirId;
+use std::fmt;
+
+use rustc_index::Idx;
+#[cfg(feature = "rustc")]
 use rustc_middle::ty::Ty;
-use usefulness::{compute_match_usefulness, UsefulnessReport};
 
-use crate::cx::MatchCheckCtxt;
-use crate::lints::{lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints};
+use crate::constructor::{Constructor, ConstructorSet};
+#[cfg(feature = "rustc")]
+use crate::lints::{
+    lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints, PatternColumn,
+};
 use crate::pat::DeconstructedPat;
+#[cfg(feature = "rustc")]
+use crate::rustc::RustcMatchCheckCtxt;
+#[cfg(feature = "rustc")]
+use crate::usefulness::{compute_match_usefulness, ValidityConstraint};
+
+// It's not possible to only enable the `typed_arena` dependency when the `rustc` feature is off, so
+// we use another feature instead. The crate won't compile if one of these isn't enabled.
+#[cfg(feature = "rustc")]
+pub(crate) use rustc_arena::TypedArena;
+#[cfg(feature = "stable")]
+pub(crate) use typed_arena::Arena as TypedArena;
+
+pub trait Captures<'a> {}
+impl<'a, T: ?Sized> Captures<'a> for T {}
+
+/// Context that provides type information about constructors.
+///
+/// Most of the crate is parameterized on a type that implements this trait.
+pub trait TypeCx: Sized + Clone + fmt::Debug {
+    /// The type of a pattern.
+    type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
+    /// The index of an enum variant.
+    type VariantIdx: Clone + Idx;
+    /// A string literal
+    type StrLit: Clone + PartialEq + fmt::Debug;
+    /// Extra data to store in a match arm.
+    type ArmData: Copy + Clone + fmt::Debug;
+    /// Extra data to store in a pattern. `Default` needed when we create fictitious wildcard
+    /// patterns during analysis.
+    type PatData: Clone + Default;
+
+    fn is_opaque_ty(ty: Self::Ty) -> bool;
+    fn is_exhaustive_patterns_feature_on(&self) -> bool;
+
+    /// The number of fields for this constructor.
+    fn ctor_arity(&self, ctor: &Constructor<Self>, ty: Self::Ty) -> usize;
+
+    /// The types of the fields for this constructor. The result must have a length of
+    /// `ctor_arity()`.
+    fn ctor_sub_tys(&self, ctor: &Constructor<Self>, ty: Self::Ty) -> &[Self::Ty];
+
+    /// The set of all the constructors for `ty`.
+    ///
+    /// This must follow the invariants of `ConstructorSet`
+    fn ctors_for_ty(&self, ty: Self::Ty) -> ConstructorSet<Self>;
+
+    /// Best-effort `Debug` implementation.
+    fn debug_pat(f: &mut fmt::Formatter<'_>, pat: &DeconstructedPat<'_, Self>) -> fmt::Result;
+
+    /// Raise a bug.
+    fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
+}
+
+/// Context that provides information global to a match.
+#[derive(Clone)]
+pub struct MatchCtxt<'a, 'p, Cx: TypeCx> {
+    /// The context for type information.
+    pub tycx: &'a Cx,
+    /// An arena to store the wildcards we produce during analysis.
+    pub wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
+}
+
+impl<'a, 'p, Cx: TypeCx> Copy for MatchCtxt<'a, 'p, Cx> {}
 
 /// The arm of a match expression.
-#[derive(Clone, Copy, Debug)]
-pub struct MatchArm<'p, 'tcx> {
-    /// The pattern must have been lowered through `check_match::MatchVisitor::lower_pattern`.
-    pub pat: &'p DeconstructedPat<'p, 'tcx>,
-    pub hir_id: HirId,
+#[derive(Clone, Debug)]
+pub struct MatchArm<'p, Cx: TypeCx> {
+    pub pat: &'p DeconstructedPat<'p, Cx>,
     pub has_guard: bool,
+    pub arm_data: Cx::ArmData,
 }
 
+impl<'p, Cx: TypeCx> Copy for MatchArm<'p, Cx> {}
+
 /// The entrypoint for this crate. Computes whether a match is exhaustive and which of its arms are
 /// useful, and runs some lints.
+#[cfg(feature = "rustc")]
 pub fn analyze_match<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
-    arms: &[MatchArm<'p, 'tcx>],
+    tycx: &RustcMatchCheckCtxt<'p, 'tcx>,
+    arms: &[rustc::MatchArm<'p, 'tcx>],
     scrut_ty: Ty<'tcx>,
-) -> UsefulnessReport<'p, 'tcx> {
-    let pat_column = PatternColumn::new(arms);
+) -> rustc::UsefulnessReport<'p, 'tcx> {
+    // Arena to store the extra wildcards we construct during analysis.
+    let wildcard_arena = tycx.pattern_arena;
+    let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
+    let cx = MatchCtxt { tycx, wildcard_arena };
 
-    let report = compute_match_usefulness(cx, arms, scrut_ty);
+    let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity);
+
+    let pat_column = PatternColumn::new(arms);
 
     // Lint on ranges that overlap on their endpoints, which is likely a mistake.
     lint_overlapping_range_endpoints(cx, &pat_column);
 
     // Run the non_exhaustive_omitted_patterns lint. Only run on refutable patterns to avoid hitting
     // `if let`s. Only run if the match is exhaustive otherwise the error is redundant.
-    if cx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
+    if tycx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
         lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty)
     }
 
diff --git a/compiler/rustc_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index 8ab559c9e7a..072ef4836a8 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -6,15 +6,16 @@ use rustc_session::lint;
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::Span;
 
-use crate::constructor::{Constructor, IntRange, MaybeInfiniteInt, SplitConstructorSet};
-use crate::cx::MatchCheckCtxt;
+use crate::constructor::{IntRange, MaybeInfiniteInt};
 use crate::errors::{
     NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Overlap,
     OverlappingRangeEndpoints, Uncovered,
 };
-use crate::pat::{DeconstructedPat, WitnessPat};
-use crate::usefulness::PatCtxt;
-use crate::MatchArm;
+use crate::rustc::{
+    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RustcMatchCheckCtxt,
+    SplitConstructorSet, WitnessPat,
+};
+use crate::TypeCx;
 
 /// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
 /// inspect the same subvalue/place".
@@ -27,11 +28,11 @@ use crate::MatchArm;
 ///
 /// This is not used in the main algorithm; only in lints.
 #[derive(Debug)]
-pub(crate) struct PatternColumn<'p, 'tcx> {
-    patterns: Vec<&'p DeconstructedPat<'p, 'tcx>>,
+pub(crate) struct PatternColumn<'a, 'p, 'tcx> {
+    patterns: Vec<&'a DeconstructedPat<'p, 'tcx>>,
 }
 
-impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
+impl<'a, 'p, 'tcx> PatternColumn<'a, 'p, 'tcx> {
     pub(crate) fn new(arms: &[MatchArm<'p, 'tcx>]) -> Self {
         let mut patterns = Vec::with_capacity(arms.len());
         for arm in arms {
@@ -53,12 +54,11 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
         }
         // If the type is opaque and it is revealed anywhere in the column, we take the revealed
         // version. Otherwise we could encounter constructors for the revealed type and crash.
-        let is_opaque = |ty: Ty<'tcx>| matches!(ty.kind(), ty::Alias(ty::Opaque, ..));
         let first_ty = self.patterns[0].ty();
-        if is_opaque(first_ty) {
+        if RustcMatchCheckCtxt::is_opaque_ty(first_ty) {
             for pat in &self.patterns {
                 let ty = pat.ty();
-                if !is_opaque(ty) {
+                if !RustcMatchCheckCtxt::is_opaque_ty(ty) {
                     return Some(ty);
                 }
             }
@@ -67,12 +67,12 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     }
 
     /// Do constructor splitting on the constructors of the column.
-    fn analyze_ctors(&self, pcx: &PatCtxt<'_, 'p, 'tcx>) -> SplitConstructorSet<'tcx> {
+    fn analyze_ctors(&self, pcx: &PlaceCtxt<'_, 'p, 'tcx>) -> SplitConstructorSet<'p, 'tcx> {
         let column_ctors = self.patterns.iter().map(|p| p.ctor());
-        pcx.cx.ctors_for_ty(pcx.ty).split(pcx, column_ctors)
+        pcx.ctors_for_ty().split(pcx, column_ctors)
     }
 
-    fn iter<'a>(&'a self) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> {
+    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>> + Captures<'b> {
         self.patterns.iter().copied()
     }
 
@@ -81,7 +81,11 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     /// This returns one column per field of the constructor. They usually all have the same length
     /// (the number of patterns in `self` that matched `ctor`), except that we expand or-patterns
     /// which may change the lengths.
-    fn specialize(&self, pcx: &PatCtxt<'_, 'p, 'tcx>, ctor: &Constructor<'tcx>) -> Vec<Self> {
+    fn specialize(
+        &self,
+        pcx: &PlaceCtxt<'a, 'p, 'tcx>,
+        ctor: &Constructor<'p, 'tcx>,
+    ) -> Vec<PatternColumn<'a, 'p, 'tcx>> {
         let arity = ctor.arity(pcx);
         if arity == 0 {
             return Vec::new();
@@ -117,14 +121,14 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
 /// Traverse the patterns to collect any variants of a non_exhaustive enum that fail to be mentioned
 /// in a given column.
 #[instrument(level = "debug", skip(cx), ret)]
-fn collect_nonexhaustive_missing_variants<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
-    column: &PatternColumn<'p, 'tcx>,
-) -> Vec<WitnessPat<'tcx>> {
+fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
+    cx: MatchCtxt<'a, 'p, 'tcx>,
+    column: &PatternColumn<'a, 'p, 'tcx>,
+) -> Vec<WitnessPat<'p, 'tcx>> {
     let Some(ty) = column.head_ty() else {
         return Vec::new();
     };
-    let pcx = &PatCtxt::new_dummy(cx, ty);
+    let pcx = &PlaceCtxt::new_dummy(cx, ty);
 
     let set = column.analyze_ctors(pcx);
     if set.present.is_empty() {
@@ -135,7 +139,7 @@ fn collect_nonexhaustive_missing_variants<'p, 'tcx>(
     }
 
     let mut witnesses = Vec::new();
-    if cx.is_foreign_non_exhaustive_enum(ty) {
+    if cx.tycx.is_foreign_non_exhaustive_enum(ty) {
         witnesses.extend(
             set.missing
                 .into_iter()
@@ -164,14 +168,15 @@ fn collect_nonexhaustive_missing_variants<'p, 'tcx>(
     witnesses
 }
 
-pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
+pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
+    cx: MatchCtxt<'a, 'p, 'tcx>,
     arms: &[MatchArm<'p, 'tcx>],
-    pat_column: &PatternColumn<'p, 'tcx>,
+    pat_column: &PatternColumn<'a, 'p, 'tcx>,
     scrut_ty: Ty<'tcx>,
 ) {
+    let rcx: &RustcMatchCheckCtxt<'_, '_> = cx.tycx;
     if !matches!(
-        cx.tcx.lint_level_at_node(NON_EXHAUSTIVE_OMITTED_PATTERNS, cx.match_lint_level).0,
+        rcx.tcx.lint_level_at_node(NON_EXHAUSTIVE_OMITTED_PATTERNS, rcx.match_lint_level).0,
         rustc_session::lint::Level::Allow
     ) {
         let witnesses = collect_nonexhaustive_missing_variants(cx, pat_column);
@@ -180,13 +185,13 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
             // is not exhaustive enough.
             //
             // NB: The partner lint for structs lives in `compiler/rustc_hir_analysis/src/check/pat.rs`.
-            cx.tcx.emit_spanned_lint(
+            rcx.tcx.emit_spanned_lint(
                 NON_EXHAUSTIVE_OMITTED_PATTERNS,
-                cx.match_lint_level,
-                cx.scrut_span,
+                rcx.match_lint_level,
+                rcx.scrut_span,
                 NonExhaustiveOmittedPattern {
                     scrut_ty,
-                    uncovered: Uncovered::new(cx.scrut_span, cx, witnesses),
+                    uncovered: Uncovered::new(rcx.scrut_span, rcx, witnesses),
                 },
             );
         }
@@ -196,17 +201,17 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
         // usage of the lint.
         for arm in arms {
             let (lint_level, lint_level_source) =
-                cx.tcx.lint_level_at_node(NON_EXHAUSTIVE_OMITTED_PATTERNS, arm.hir_id);
+                rcx.tcx.lint_level_at_node(NON_EXHAUSTIVE_OMITTED_PATTERNS, arm.arm_data);
             if !matches!(lint_level, rustc_session::lint::Level::Allow) {
                 let decorator = NonExhaustiveOmittedPatternLintOnArm {
                     lint_span: lint_level_source.span(),
-                    suggest_lint_on_match: cx.whole_match_span.map(|span| span.shrink_to_lo()),
+                    suggest_lint_on_match: rcx.whole_match_span.map(|span| span.shrink_to_lo()),
                     lint_level: lint_level.as_str(),
                     lint_name: "non_exhaustive_omitted_patterns",
                 };
 
                 use rustc_errors::DecorateLint;
-                let mut err = cx.tcx.sess.struct_span_warn(arm.pat.span(), "");
+                let mut err = rcx.tcx.sess.struct_span_warn(*arm.pat.data(), "");
                 err.set_primary_message(decorator.msg());
                 decorator.decorate_lint(&mut err);
                 err.emit();
@@ -217,28 +222,29 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
 
 /// Traverse the patterns to warn the user about ranges that overlap on their endpoints.
 #[instrument(level = "debug", skip(cx))]
-pub(crate) fn lint_overlapping_range_endpoints<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
-    column: &PatternColumn<'p, 'tcx>,
+pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
+    cx: MatchCtxt<'a, 'p, 'tcx>,
+    column: &PatternColumn<'a, 'p, 'tcx>,
 ) {
     let Some(ty) = column.head_ty() else {
         return;
     };
-    let pcx = &PatCtxt::new_dummy(cx, ty);
+    let pcx = &PlaceCtxt::new_dummy(cx, ty);
+    let rcx: &RustcMatchCheckCtxt<'_, '_> = cx.tycx;
 
     let set = column.analyze_ctors(pcx);
 
     if matches!(ty.kind(), ty::Char | ty::Int(_) | ty::Uint(_)) {
         let emit_lint = |overlap: &IntRange, this_span: Span, overlapped_spans: &[Span]| {
-            let overlap_as_pat = cx.hoist_pat_range(overlap, ty);
+            let overlap_as_pat = rcx.hoist_pat_range(overlap, ty);
             let overlaps: Vec<_> = overlapped_spans
                 .iter()
                 .copied()
                 .map(|span| Overlap { range: overlap_as_pat.clone(), span })
                 .collect();
-            cx.tcx.emit_spanned_lint(
+            rcx.tcx.emit_spanned_lint(
                 lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
-                cx.match_lint_level,
+                rcx.match_lint_level,
                 this_span,
                 OverlappingRangeEndpoints { overlap: overlaps, range: this_span },
             );
@@ -255,7 +261,7 @@ pub(crate) fn lint_overlapping_range_endpoints<'p, 'tcx>(
                 let mut suffixes: SmallVec<[_; 1]> = Default::default();
                 // Iterate on patterns that contained `overlap`.
                 for pat in column.iter() {
-                    let this_span = pat.span();
+                    let this_span = *pat.data();
                     let Constructor::IntRange(this_range) = pat.ctor() else { continue };
                     if this_range.is_singleton() {
                         // Don't lint when one of the ranges is a singleton.
diff --git a/compiler/rustc_pattern_analysis/src/pat.rs b/compiler/rustc_pattern_analysis/src/pat.rs
index 404651124ad..0cc8477b7cd 100644
--- a/compiler/rustc_pattern_analysis/src/pat.rs
+++ b/compiler/rustc_pattern_analysis/src/pat.rs
@@ -5,16 +5,11 @@ use std::fmt;
 
 use smallvec::{smallvec, SmallVec};
 
-use rustc_data_structures::captures::Captures;
-use rustc_middle::ty::{self, Ty};
-use rustc_span::{Span, DUMMY_SP};
+use crate::constructor::{Constructor, Slice, SliceKind};
+use crate::usefulness::PlaceCtxt;
+use crate::{Captures, TypeCx};
 
 use self::Constructor::*;
-use self::SliceKind::*;
-
-use crate::constructor::{Constructor, SliceKind};
-use crate::cx::MatchCheckCtxt;
-use crate::usefulness::PatCtxt;
 
 /// Values and patterns can be represented as a constructor applied to some fields. This represents
 /// a pattern in this form.
@@ -27,34 +22,34 @@ use crate::usefulness::PatCtxt;
 /// This happens if a private or `non_exhaustive` field is uninhabited, because the code mustn't
 /// observe that it is uninhabited. In that case that field is not included in `fields`. Care must
 /// be taken when converting to/from `thir::Pat`.
-pub struct DeconstructedPat<'p, 'tcx> {
-    ctor: Constructor<'tcx>,
-    fields: &'p [DeconstructedPat<'p, 'tcx>],
-    ty: Ty<'tcx>,
-    span: Span,
+pub struct DeconstructedPat<'p, Cx: TypeCx> {
+    ctor: Constructor<Cx>,
+    fields: &'p [DeconstructedPat<'p, Cx>],
+    ty: Cx::Ty,
+    data: Cx::PatData,
     /// Whether removing this arm would change the behavior of the match expression.
     useful: Cell<bool>,
 }
 
-impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
-    pub fn wildcard(ty: Ty<'tcx>, span: Span) -> Self {
-        Self::new(Wildcard, &[], ty, span)
+impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
+    pub fn wildcard(ty: Cx::Ty, data: Cx::PatData) -> Self {
+        Self::new(Wildcard, &[], ty, data)
     }
 
     pub fn new(
-        ctor: Constructor<'tcx>,
-        fields: &'p [DeconstructedPat<'p, 'tcx>],
-        ty: Ty<'tcx>,
-        span: Span,
+        ctor: Constructor<Cx>,
+        fields: &'p [DeconstructedPat<'p, Cx>],
+        ty: Cx::Ty,
+        data: Cx::PatData,
     ) -> Self {
-        DeconstructedPat { ctor, fields, ty, span, useful: Cell::new(false) }
+        DeconstructedPat { ctor, fields, ty, data, useful: Cell::new(false) }
     }
 
     pub(crate) fn is_or_pat(&self) -> bool {
         matches!(self.ctor, Or)
     }
     /// Expand this (possibly-nested) or-pattern into its alternatives.
-    pub(crate) fn flatten_or_pat(&'p self) -> SmallVec<[&'p Self; 1]> {
+    pub(crate) fn flatten_or_pat(&self) -> SmallVec<[&Self; 1]> {
         if self.is_or_pat() {
             self.iter_fields().flat_map(|p| p.flatten_or_pat()).collect()
         } else {
@@ -62,66 +57,64 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
         }
     }
 
-    pub fn ctor(&self) -> &Constructor<'tcx> {
+    pub fn ctor(&self) -> &Constructor<Cx> {
         &self.ctor
     }
-    pub fn ty(&self) -> Ty<'tcx> {
+    pub fn ty(&self) -> Cx::Ty {
         self.ty
     }
-    pub fn span(&self) -> Span {
-        self.span
+    pub fn data(&self) -> &Cx::PatData {
+        &self.data
     }
 
     pub fn iter_fields<'a>(
         &'a self,
-    ) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Captures<'a> {
+    ) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'a> {
         self.fields.iter()
     }
 
     /// Specialize this pattern with a constructor.
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
     pub(crate) fn specialize<'a>(
-        &'a self,
-        pcx: &PatCtxt<'_, 'p, 'tcx>,
-        other_ctor: &Constructor<'tcx>,
-    ) -> SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]> {
+        &self,
+        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        other_ctor: &Constructor<Cx>,
+    ) -> SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]> {
+        let wildcard_sub_tys = || {
+            let tys = pcx.ctor_sub_tys(other_ctor);
+            tys.iter()
+                .map(|ty| DeconstructedPat::wildcard(*ty, Cx::PatData::default()))
+                .map(|pat| pcx.mcx.wildcard_arena.alloc(pat) as &_)
+                .collect()
+        };
         match (&self.ctor, other_ctor) {
-            (Wildcard, _) => {
-                // We return a wildcard for each field of `other_ctor`.
-                pcx.cx.ctor_wildcard_fields(other_ctor, pcx.ty).iter().collect()
-            }
-            (Slice(self_slice), Slice(other_slice))
-                if self_slice.arity() != other_slice.arity() =>
-            {
-                // The only tricky case: two slices of different arity. Since `self_slice` covers
-                // `other_slice`, `self_slice` must be `VarLen`, i.e. of the form
-                // `[prefix, .., suffix]`. Moreover `other_slice` is guaranteed to have a larger
-                // arity. So we fill the middle part with enough wildcards to reach the length of
-                // the new, larger slice.
-                match self_slice.kind {
-                    FixedLen(_) => bug!("{:?} doesn't cover {:?}", self_slice, other_slice),
-                    VarLen(prefix, suffix) => {
-                        let (ty::Slice(inner_ty) | ty::Array(inner_ty, _)) = *self.ty.kind() else {
-                            bug!("bad slice pattern {:?} {:?}", self.ctor, self.ty);
-                        };
-                        let prefix = &self.fields[..prefix];
-                        let suffix = &self.fields[self_slice.arity() - suffix..];
-                        let wildcard: &_ = pcx
-                            .cx
-                            .pattern_arena
-                            .alloc(DeconstructedPat::wildcard(inner_ty, DUMMY_SP));
-                        let extra_wildcards = other_slice.arity() - self_slice.arity();
-                        let extra_wildcards = (0..extra_wildcards).map(|_| wildcard);
-                        prefix.iter().chain(extra_wildcards).chain(suffix).collect()
-                    }
+            // Return a wildcard for each field of `other_ctor`.
+            (Wildcard, _) => wildcard_sub_tys(),
+            // The only non-trivial case: two slices of different arity. `other_slice` is
+            // guaranteed to have a larger arity, so we fill the middle part with enough
+            // wildcards to reach the length of the new, larger slice.
+            (
+                &Slice(self_slice @ Slice { kind: SliceKind::VarLen(prefix, suffix), .. }),
+                &Slice(other_slice),
+            ) if self_slice.arity() != other_slice.arity() => {
+                // Start with a slice of wildcards of the appropriate length.
+                let mut fields: SmallVec<[_; 2]> = wildcard_sub_tys();
+                // Fill in the fields from both ends.
+                let new_arity = fields.len();
+                for i in 0..prefix {
+                    fields[i] = &self.fields[i];
+                }
+                for i in 0..suffix {
+                    fields[new_arity - 1 - i] = &self.fields[self.fields.len() - 1 - i];
                 }
+                fields
             }
             _ => self.fields.iter().collect(),
         }
     }
 
-    /// We keep track for each pattern if it was ever useful during the analysis. This is used
-    /// with `redundant_spans` to report redundant subpatterns arising from or patterns.
+    /// We keep track for each pattern if it was ever useful during the analysis. This is used with
+    /// `redundant_subpatterns` to report redundant subpatterns arising from or patterns.
     pub(crate) fn set_useful(&self) {
         self.useful.set(true)
     }
@@ -139,19 +132,19 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
         }
     }
 
-    /// Report the spans of subpatterns that were not useful, if any.
-    pub(crate) fn redundant_spans(&self) -> Vec<Span> {
-        let mut spans = Vec::new();
-        self.collect_redundant_spans(&mut spans);
-        spans
+    /// Report the subpatterns that were not useful, if any.
+    pub(crate) fn redundant_subpatterns(&self) -> Vec<&Self> {
+        let mut subpats = Vec::new();
+        self.collect_redundant_subpatterns(&mut subpats);
+        subpats
     }
-    fn collect_redundant_spans(&self, spans: &mut Vec<Span>) {
+    fn collect_redundant_subpatterns<'a>(&'a self, subpats: &mut Vec<&'a Self>) {
         // We don't look at subpatterns if we already reported the whole pattern as redundant.
         if !self.is_useful() {
-            spans.push(self.span);
+            subpats.push(self);
         } else {
             for p in self.iter_fields() {
-                p.collect_redundant_spans(spans);
+                p.collect_redundant_subpatterns(subpats);
             }
         }
     }
@@ -159,47 +152,46 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
 
 /// This is mostly copied from the `Pat` impl. This is best effort and not good enough for a
 /// `Display` impl.
-impl<'p, 'tcx> fmt::Debug for DeconstructedPat<'p, 'tcx> {
+impl<'p, Cx: TypeCx> fmt::Debug for DeconstructedPat<'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        MatchCheckCtxt::debug_pat(f, self)
+        Cx::debug_pat(f, self)
     }
 }
 
 /// Same idea as `DeconstructedPat`, except this is a fictitious pattern built up for diagnostics
 /// purposes. As such they don't use interning and can be cloned.
 #[derive(Debug, Clone)]
-pub struct WitnessPat<'tcx> {
-    ctor: Constructor<'tcx>,
-    pub(crate) fields: Vec<WitnessPat<'tcx>>,
-    ty: Ty<'tcx>,
+pub struct WitnessPat<Cx: TypeCx> {
+    ctor: Constructor<Cx>,
+    pub(crate) fields: Vec<WitnessPat<Cx>>,
+    ty: Cx::Ty,
 }
 
-impl<'tcx> WitnessPat<'tcx> {
-    pub(crate) fn new(ctor: Constructor<'tcx>, fields: Vec<Self>, ty: Ty<'tcx>) -> Self {
+impl<Cx: TypeCx> WitnessPat<Cx> {
+    pub(crate) fn new(ctor: Constructor<Cx>, fields: Vec<Self>, ty: Cx::Ty) -> Self {
         Self { ctor, fields, ty }
     }
-    pub(crate) fn wildcard(ty: Ty<'tcx>) -> Self {
+    pub(crate) fn wildcard(ty: Cx::Ty) -> Self {
         Self::new(Wildcard, Vec::new(), ty)
     }
 
     /// Construct a pattern that matches everything that starts with this constructor.
     /// For example, if `ctor` is a `Constructor::Variant` for `Option::Some`, we get the pattern
     /// `Some(_)`.
-    pub(crate) fn wild_from_ctor(pcx: &PatCtxt<'_, '_, 'tcx>, ctor: Constructor<'tcx>) -> Self {
-        let field_tys =
-            pcx.cx.ctor_wildcard_fields(&ctor, pcx.ty).iter().map(|deco_pat| deco_pat.ty());
-        let fields = field_tys.map(|ty| Self::wildcard(ty)).collect();
+    pub(crate) fn wild_from_ctor(pcx: &PlaceCtxt<'_, '_, Cx>, ctor: Constructor<Cx>) -> Self {
+        let field_tys = pcx.ctor_sub_tys(&ctor);
+        let fields = field_tys.iter().map(|ty| Self::wildcard(*ty)).collect();
         Self::new(ctor, fields, pcx.ty)
     }
 
-    pub fn ctor(&self) -> &Constructor<'tcx> {
+    pub fn ctor(&self) -> &Constructor<Cx> {
         &self.ctor
     }
-    pub fn ty(&self) -> Ty<'tcx> {
+    pub fn ty(&self) -> Cx::Ty {
         self.ty
     }
 
-    pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<'tcx>> {
+    pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a WitnessPat<Cx>> {
         self.fields.iter()
     }
 }
diff --git a/compiler/rustc_pattern_analysis/src/cx.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index 8a4f39a1f4a..65c90aa9f1d 100644
--- a/compiler/rustc_pattern_analysis/src/cx.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -1,15 +1,15 @@
 use std::fmt;
 use std::iter::once;
 
-use rustc_arena::TypedArena;
+use rustc_arena::{DroplessArena, TypedArena};
 use rustc_data_structures::captures::Captures;
 use rustc_hir::def_id::DefId;
-use rustc_hir::{HirId, RangeEnd};
+use rustc_hir::HirId;
 use rustc_index::Idx;
 use rustc_index::IndexVec;
 use rustc_middle::middle::stability::EvalResult;
-use rustc_middle::mir;
 use rustc_middle::mir::interpret::Scalar;
+use rustc_middle::mir::{self, Const};
 use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange, PatRangeBoundary};
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
@@ -18,14 +18,31 @@ use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
 use smallvec::SmallVec;
 
 use crate::constructor::{
-    Constructor, ConstructorSet, IntRange, MaybeInfiniteInt, OpaqueId, Slice, SliceKind,
-    VariantVisibility,
+    IntRange, MaybeInfiniteInt, OpaqueId, RangeEnd, Slice, SliceKind, VariantVisibility,
 };
-use crate::pat::{DeconstructedPat, WitnessPat};
+use crate::TypeCx;
 
-use Constructor::*;
+use crate::constructor::Constructor::*;
 
-pub struct MatchCheckCtxt<'p, 'tcx> {
+// Re-export rustc-specific versions of all these types.
+pub type Constructor<'p, 'tcx> = crate::constructor::Constructor<RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type ConstructorSet<'p, 'tcx> =
+    crate::constructor::ConstructorSet<RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type DeconstructedPat<'p, 'tcx> =
+    crate::pat::DeconstructedPat<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type MatchArm<'p, 'tcx> = crate::MatchArm<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type MatchCtxt<'a, 'p, 'tcx> = crate::MatchCtxt<'a, 'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub(crate) type PlaceCtxt<'a, 'p, 'tcx> =
+    crate::usefulness::PlaceCtxt<'a, 'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub(crate) type SplitConstructorSet<'p, 'tcx> =
+    crate::constructor::SplitConstructorSet<RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type Usefulness<'p, 'tcx> = crate::usefulness::Usefulness<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type UsefulnessReport<'p, 'tcx> =
+    crate::usefulness::UsefulnessReport<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type WitnessPat<'p, 'tcx> = crate::pat::WitnessPat<RustcMatchCheckCtxt<'p, 'tcx>>;
+
+#[derive(Clone)]
+pub struct RustcMatchCheckCtxt<'p, 'tcx> {
     pub tcx: TyCtxt<'tcx>,
     /// The module in which the match occurs. This is necessary for
     /// checking inhabited-ness of types because whether a type is (visibly)
@@ -35,6 +52,7 @@ pub struct MatchCheckCtxt<'p, 'tcx> {
     pub module: DefId,
     pub param_env: ty::ParamEnv<'tcx>,
     pub pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
+    pub dropless_arena: &'p DroplessArena,
     /// Lint level at the match.
     pub match_lint_level: HirId,
     /// The span of the whole match, if applicable.
@@ -48,8 +66,14 @@ pub struct MatchCheckCtxt<'p, 'tcx> {
     pub known_valid_scrutinee: bool,
 }
 
-impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
-    pub(super) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
+impl<'p, 'tcx> fmt::Debug for RustcMatchCheckCtxt<'p, 'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("RustcMatchCheckCtxt").finish()
+    }
+}
+
+impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
+    pub(crate) fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
         !ty.is_inhabited_from(self.tcx, self.module, self.param_env)
     }
 
@@ -63,12 +87,18 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
         }
     }
 
-    pub(crate) fn alloc_wildcard_slice(
-        &self,
-        tys: impl IntoIterator<Item = Ty<'tcx>>,
-    ) -> &'p [DeconstructedPat<'p, 'tcx>] {
-        self.pattern_arena
-            .alloc_from_iter(tys.into_iter().map(|ty| DeconstructedPat::wildcard(ty, DUMMY_SP)))
+    /// Whether the range denotes the fictitious values before `isize::MIN` or after
+    /// `usize::MAX`/`isize::MAX` (see doc of [`IntRange::split`] for why these exist).
+    pub fn is_range_beyond_boundaries(&self, range: &IntRange, ty: Ty<'tcx>) -> bool {
+        ty.is_ptr_sized_integral() && {
+            // The two invalid ranges are `NegInfinity..isize::MIN` (represented as
+            // `NegInfinity..0`), and `{u,i}size::MAX+1..PosInfinity`. `hoist_pat_range_bdy`
+            // converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `range.lo`
+            // otherwise.
+            let lo = self.hoist_pat_range_bdy(range.lo, ty);
+            matches!(lo, PatRangeBoundary::PosInfinity)
+                || matches!(range.hi, MaybeInfiniteInt::Finite(0))
+        }
     }
 
     // In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide
@@ -100,12 +130,12 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
     }
 
     pub(crate) fn variant_index_for_adt(
-        ctor: &Constructor<'tcx>,
+        ctor: &Constructor<'p, 'tcx>,
         adt: ty::AdtDef<'tcx>,
     ) -> VariantIdx {
         match *ctor {
             Variant(idx) => idx,
-            Single => {
+            Struct | UnionField => {
                 assert!(!adt.is_enum());
                 FIRST_VARIANT
             }
@@ -113,37 +143,36 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
         }
     }
 
-    /// Creates a new list of wildcard fields for a given constructor. The result must have a length
-    /// of `ctor.arity()`.
+    /// Returns the types of the fields for a given constructor. The result must have a length of
+    /// `ctor.arity()`.
     #[instrument(level = "trace", skip(self))]
-    pub(crate) fn ctor_wildcard_fields(
-        &self,
-        ctor: &Constructor<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> &'p [DeconstructedPat<'p, 'tcx>] {
+    pub(crate) fn ctor_sub_tys(&self, ctor: &Constructor<'p, 'tcx>, ty: Ty<'tcx>) -> &[Ty<'tcx>] {
         let cx = self;
         match ctor {
-            Single | Variant(_) => match ty.kind() {
-                ty::Tuple(fs) => cx.alloc_wildcard_slice(fs.iter()),
-                ty::Ref(_, rty, _) => cx.alloc_wildcard_slice(once(*rty)),
+            Struct | Variant(_) | UnionField => match ty.kind() {
+                ty::Tuple(fs) => cx.dropless_arena.alloc_from_iter(fs.iter()),
                 ty::Adt(adt, args) => {
                     if adt.is_box() {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
                         // patterns. If we're here we can assume this is a box pattern.
-                        cx.alloc_wildcard_slice(once(args.type_at(0)))
+                        cx.dropless_arena.alloc_from_iter(once(args.type_at(0)))
                     } else {
                         let variant =
-                            &adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
+                            &adt.variant(RustcMatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
                         let tys = cx.list_variant_nonhidden_fields(ty, variant).map(|(_, ty)| ty);
-                        cx.alloc_wildcard_slice(tys)
+                        cx.dropless_arena.alloc_from_iter(tys)
                     }
                 }
-                _ => bug!("Unexpected type for `Single` constructor: {:?}", ty),
+                _ => bug!("Unexpected type for constructor `{ctor:?}`: {ty:?}"),
+            },
+            Ref => match ty.kind() {
+                ty::Ref(_, rty, _) => cx.dropless_arena.alloc_from_iter(once(*rty)),
+                _ => bug!("Unexpected type for `Ref` constructor: {ty:?}"),
             },
             Slice(slice) => match *ty.kind() {
                 ty::Slice(ty) | ty::Array(ty, _) => {
                     let arity = slice.arity();
-                    cx.alloc_wildcard_slice((0..arity).map(|_| ty))
+                    cx.dropless_arena.alloc_from_iter((0..arity).map(|_| ty))
                 }
                 _ => bug!("bad slice pattern {:?} {:?}", ctor, ty),
             },
@@ -163,13 +192,11 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
         }
     }
 
-    /// The number of fields for this constructor. This must be kept in sync with
-    /// `Fields::wildcards`.
-    pub(crate) fn ctor_arity(&self, ctor: &Constructor<'tcx>, ty: Ty<'tcx>) -> usize {
+    /// The number of fields for this constructor.
+    pub(crate) fn ctor_arity(&self, ctor: &Constructor<'p, 'tcx>, ty: Ty<'tcx>) -> usize {
         match ctor {
-            Single | Variant(_) => match ty.kind() {
+            Struct | Variant(_) | UnionField => match ty.kind() {
                 ty::Tuple(fs) => fs.len(),
-                ty::Ref(..) => 1,
                 ty::Adt(adt, ..) => {
                     if adt.is_box() {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
@@ -177,12 +204,13 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                         1
                     } else {
                         let variant =
-                            &adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
+                            &adt.variant(RustcMatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
                         self.list_variant_nonhidden_fields(ty, variant).count()
                     }
                 }
-                _ => bug!("Unexpected type for `Single` constructor: {:?}", ty),
+                _ => bug!("Unexpected type for constructor `{ctor:?}`: {ty:?}"),
             },
+            Ref => 1,
             Slice(slice) => slice.arity(),
             Bool(..)
             | IntRange(..)
@@ -202,7 +230,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
     ///
     /// See [`crate::constructor`] for considerations of emptiness.
     #[instrument(level = "debug", skip(self), ret)]
-    pub fn ctors_for_ty(&self, ty: Ty<'tcx>) -> ConstructorSet {
+    pub fn ctors_for_ty(&self, ty: Ty<'tcx>) -> ConstructorSet<'p, 'tcx> {
         let cx = self;
         let make_uint_range = |start, end| {
             IntRange::from_range(
@@ -298,9 +326,9 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                     ConstructorSet::Variants { variants, non_exhaustive: is_declared_nonexhaustive }
                 }
             }
-            ty::Adt(..) | ty::Tuple(..) | ty::Ref(..) => {
-                ConstructorSet::Single { empty: cx.is_uninhabited(ty) }
-            }
+            ty::Adt(def, _) if def.is_union() => ConstructorSet::Union,
+            ty::Adt(..) | ty::Tuple(..) => ConstructorSet::Struct { empty: cx.is_uninhabited(ty) },
+            ty::Ref(..) => ConstructorSet::Ref,
             ty::Never => ConstructorSet::NoConstructors,
             // This type is one for which we cannot list constructors, like `str` or `f64`.
             // FIXME(Nadrieril): which of these are actually allowed?
@@ -359,13 +387,18 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                 fields = &[];
             }
             PatKind::Deref { subpattern } => {
-                ctor = Single;
                 fields = singleton(self.lower_pat(subpattern));
+                ctor = match pat.ty.kind() {
+                    // This is a box pattern.
+                    ty::Adt(adt, ..) if adt.is_box() => Struct,
+                    ty::Ref(..) => Ref,
+                    _ => bug!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, pat.ty),
+                };
             }
             PatKind::Leaf { subpatterns } | PatKind::Variant { subpatterns, .. } => {
                 match pat.ty.kind() {
                     ty::Tuple(fs) => {
-                        ctor = Single;
+                        ctor = Struct;
                         let mut wilds: SmallVec<[_; 2]> =
                             fs.iter().map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
                         for pat in subpatterns {
@@ -380,7 +413,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                         // _)` or a box pattern. As a hack to avoid an ICE with the former, we
                         // ignore other fields than the first one. This will trigger an error later
                         // anyway.
-                        // See https://github.com/rust-lang/rust/issues/82772 ,
+                        // See https://github.com/rust-lang/rust/issues/82772,
                         // explanation: https://github.com/rust-lang/rust/pull/82789#issuecomment-796921977
                         // The problem is that we can't know from the type whether we'll match
                         // normally or through box-patterns. We'll have to figure out a proper
@@ -392,17 +425,18 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                         } else {
                             DeconstructedPat::wildcard(args.type_at(0), pat.span)
                         };
-                        ctor = Single;
+                        ctor = Struct;
                         fields = singleton(pat);
                     }
                     ty::Adt(adt, _) => {
                         ctor = match pat.kind {
-                            PatKind::Leaf { .. } => Single,
+                            PatKind::Leaf { .. } if adt.is_union() => UnionField,
+                            PatKind::Leaf { .. } => Struct,
                             PatKind::Variant { variant_index, .. } => Variant(variant_index),
                             _ => bug!(),
                         };
                         let variant =
-                            &adt.variant(MatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
+                            &adt.variant(RustcMatchCheckCtxt::variant_index_for_adt(&ctor, *adt));
                         // For each field in the variant, we store the relevant index into `self.fields` if any.
                         let mut field_id_to_id: Vec<Option<usize>> =
                             (0..variant.fields.len()).map(|_| None).collect();
@@ -477,11 +511,11 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                         // with other `Deref` patterns. This could have been done in `const_to_pat`,
                         // but that causes issues with the rest of the matching code.
                         // So here, the constructor for a `"foo"` pattern is `&` (represented by
-                        // `Single`), and has one field. That field has constructor `Str(value)` and no
-                        // fields.
+                        // `Ref`), and has one field. That field has constructor `Str(value)` and no
+                        // subfields.
                         // Note: `t` is `str`, not `&str`.
                         let subpattern = DeconstructedPat::new(Str(*value), &[], *t, pat.span);
-                        ctor = Single;
+                        ctor = Ref;
                         fields = singleton(subpattern)
                     }
                     // All constants that can be structurally matched have already been expanded
@@ -495,12 +529,16 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
             }
             PatKind::Range(patrange) => {
                 let PatRange { lo, hi, end, .. } = patrange.as_ref();
+                let end = match end {
+                    rustc_hir::RangeEnd::Included => RangeEnd::Included,
+                    rustc_hir::RangeEnd::Excluded => RangeEnd::Excluded,
+                };
                 let ty = pat.ty;
                 ctor = match ty.kind() {
                     ty::Char | ty::Int(_) | ty::Uint(_) => {
                         let lo = cx.lower_pat_range_bdy(*lo, ty);
                         let hi = cx.lower_pat_range_bdy(*hi, ty);
-                        IntRange(IntRange::from_range(lo, hi, *end))
+                        IntRange(IntRange::from_range(lo, hi, end))
                     }
                     ty::Float(fty) => {
                         use rustc_apfloat::Float;
@@ -511,13 +549,13 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                                 use rustc_apfloat::ieee::Single;
                                 let lo = lo.map(Single::from_bits).unwrap_or(-Single::INFINITY);
                                 let hi = hi.map(Single::from_bits).unwrap_or(Single::INFINITY);
-                                F32Range(lo, hi, *end)
+                                F32Range(lo, hi, end)
                             }
                             ty::FloatTy::F64 => {
                                 use rustc_apfloat::ieee::Double;
                                 let lo = lo.map(Double::from_bits).unwrap_or(-Double::INFINITY);
                                 let hi = hi.map(Double::from_bits).unwrap_or(Double::INFINITY);
-                                F64Range(lo, hi, *end)
+                                F64Range(lo, hi, end)
                             }
                         }
                     }
@@ -597,20 +635,6 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
         }
     }
 
-    /// Whether the range denotes the fictitious values before `isize::MIN` or after
-    /// `usize::MAX`/`isize::MAX` (see doc of [`IntRange::split`] for why these exist).
-    pub fn is_range_beyond_boundaries(&self, range: &IntRange, ty: Ty<'tcx>) -> bool {
-        ty.is_ptr_sized_integral() && {
-            // The two invalid ranges are `NegInfinity..isize::MIN` (represented as
-            // `NegInfinity..0`), and `{u,i}size::MAX+1..PosInfinity`. `hoist_pat_range_bdy`
-            // converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `range.lo`
-            // otherwise.
-            let lo = self.hoist_pat_range_bdy(range.lo, ty);
-            matches!(lo, PatRangeBoundary::PosInfinity)
-                || matches!(range.hi, MaybeInfiniteInt::Finite(0))
-        }
-    }
-
     /// Convert back to a `thir::Pat` for diagnostic purposes.
     pub(crate) fn hoist_pat_range(&self, range: &IntRange, ty: Ty<'tcx>) -> Pat<'tcx> {
         use MaybeInfiniteInt::*;
@@ -623,7 +647,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
             PatKind::Constant { value }
         } else {
             // We convert to an inclusive range for diagnostics.
-            let mut end = RangeEnd::Included;
+            let mut end = rustc_hir::RangeEnd::Included;
             let mut lo = cx.hoist_pat_range_bdy(range.lo, ty);
             if matches!(lo, PatRangeBoundary::PosInfinity) {
                 // The only reason to get `PosInfinity` here is the special case where
@@ -637,7 +661,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
             }
             let hi = if matches!(range.hi, Finite(0)) {
                 // The range encodes `..ty::MIN`, so we can't convert it to an inclusive range.
-                end = RangeEnd::Excluded;
+                end = rustc_hir::RangeEnd::Excluded;
                 range.hi
             } else {
                 range.hi.minus_one()
@@ -650,14 +674,14 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
     }
     /// Convert back to a `thir::Pat` for diagnostic purposes. This panics for patterns that don't
     /// appear in diagnostics, like float ranges.
-    pub fn hoist_witness_pat(&self, pat: &WitnessPat<'tcx>) -> Pat<'tcx> {
+    pub fn hoist_witness_pat(&self, pat: &WitnessPat<'p, 'tcx>) -> Pat<'tcx> {
         let cx = self;
         let is_wildcard = |pat: &Pat<'_>| matches!(pat.kind, PatKind::Wild);
         let mut subpatterns = pat.iter_fields().map(|p| Box::new(cx.hoist_witness_pat(p)));
         let kind = match pat.ctor() {
             Bool(b) => PatKind::Constant { value: mir::Const::from_bool(cx.tcx, *b) },
             IntRange(range) => return self.hoist_pat_range(range, pat.ty()),
-            Single | Variant(_) => match pat.ty().kind() {
+            Struct | Variant(_) | UnionField => match pat.ty().kind() {
                 ty::Tuple(..) => PatKind::Leaf {
                     subpatterns: subpatterns
                         .enumerate()
@@ -672,7 +696,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                 }
                 ty::Adt(adt_def, args) => {
                     let variant_index =
-                        MatchCheckCtxt::variant_index_for_adt(&pat.ctor(), *adt_def);
+                        RustcMatchCheckCtxt::variant_index_for_adt(&pat.ctor(), *adt_def);
                     let variant = &adt_def.variant(variant_index);
                     let subpatterns = cx
                         .list_variant_nonhidden_fields(pat.ty(), variant)
@@ -686,13 +710,13 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                         PatKind::Leaf { subpatterns }
                     }
                 }
-                // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
-                // be careful to reconstruct the correct constant pattern here. However a string
-                // literal pattern will never be reported as a non-exhaustiveness witness, so we
-                // ignore this issue.
-                ty::Ref(..) => PatKind::Deref { subpattern: subpatterns.next().unwrap() },
                 _ => bug!("unexpected ctor for type {:?} {:?}", pat.ctor(), pat.ty()),
             },
+            // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
+            // be careful to reconstruct the correct constant pattern here. However a string
+            // literal pattern will never be reported as a non-exhaustiveness witness, so we
+            // ignore this issue.
+            Ref => PatKind::Deref { subpattern: subpatterns.next().unwrap() },
             Slice(slice) => {
                 match slice.kind {
                     SliceKind::FixedLen(_) => PatKind::Slice {
@@ -744,7 +768,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
     /// Best-effort `Debug` implementation.
     pub(crate) fn debug_pat(
         f: &mut fmt::Formatter<'_>,
-        pat: &DeconstructedPat<'p, 'tcx>,
+        pat: &crate::pat::DeconstructedPat<'_, Self>,
     ) -> fmt::Result {
         let mut first = true;
         let mut start_or_continue = |s| {
@@ -758,7 +782,7 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
         let mut start_or_comma = || start_or_continue(", ");
 
         match pat.ctor() {
-            Single | Variant(_) => match pat.ty().kind() {
+            Struct | Variant(_) | UnionField => match pat.ty().kind() {
                 ty::Adt(def, _) if def.is_box() => {
                     // Without `box_patterns`, the only legal pattern of type `Box` is `_` (outside
                     // of `std`). So this branch is only reachable when the feature is enabled and
@@ -767,13 +791,14 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                     write!(f, "box {subpattern:?}")
                 }
                 ty::Adt(..) | ty::Tuple(..) => {
-                    let variant = match pat.ty().kind() {
-                        ty::Adt(adt, _) => Some(
-                            adt.variant(MatchCheckCtxt::variant_index_for_adt(pat.ctor(), *adt)),
-                        ),
-                        ty::Tuple(_) => None,
-                        _ => unreachable!(),
-                    };
+                    let variant =
+                        match pat.ty().kind() {
+                            ty::Adt(adt, _) => Some(adt.variant(
+                                RustcMatchCheckCtxt::variant_index_for_adt(pat.ctor(), *adt),
+                            )),
+                            ty::Tuple(_) => None,
+                            _ => unreachable!(),
+                        };
 
                     if let Some(variant) = variant {
                         write!(f, "{}", variant.name)?;
@@ -789,15 +814,15 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
                     }
                     write!(f, ")")
                 }
-                // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
-                // be careful to detect strings here. However a string literal pattern will never
-                // be reported as a non-exhaustiveness witness, so we can ignore this issue.
-                ty::Ref(_, _, mutbl) => {
-                    let subpattern = pat.iter_fields().next().unwrap();
-                    write!(f, "&{}{:?}", mutbl.prefix_str(), subpattern)
-                }
                 _ => write!(f, "_"),
             },
+            // Note: given the expansion of `&str` patterns done in `expand_pattern`, we should
+            // be careful to detect strings here. However a string literal pattern will never
+            // be reported as a non-exhaustiveness witness, so we can ignore this issue.
+            Ref => {
+                let subpattern = pat.iter_fields().next().unwrap();
+                write!(f, "&{:?}", subpattern)
+            }
             Slice(slice) => {
                 let mut subpatterns = pat.iter_fields();
                 write!(f, "[")?;
@@ -838,6 +863,45 @@ impl<'p, 'tcx> MatchCheckCtxt<'p, 'tcx> {
     }
 }
 
+impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
+    type Ty = Ty<'tcx>;
+    type VariantIdx = VariantIdx;
+    type StrLit = Const<'tcx>;
+    type ArmData = HirId;
+    type PatData = Span;
+
+    fn is_exhaustive_patterns_feature_on(&self) -> bool {
+        self.tcx.features().exhaustive_patterns
+    }
+    fn is_opaque_ty(ty: Self::Ty) -> bool {
+        matches!(ty.kind(), ty::Alias(ty::Opaque, ..))
+    }
+
+    fn ctor_arity(&self, ctor: &crate::constructor::Constructor<Self>, ty: Self::Ty) -> usize {
+        self.ctor_arity(ctor, ty)
+    }
+    fn ctor_sub_tys(
+        &self,
+        ctor: &crate::constructor::Constructor<Self>,
+        ty: Self::Ty,
+    ) -> &[Self::Ty] {
+        self.ctor_sub_tys(ctor, ty)
+    }
+    fn ctors_for_ty(&self, ty: Self::Ty) -> crate::constructor::ConstructorSet<Self> {
+        self.ctors_for_ty(ty)
+    }
+
+    fn debug_pat(
+        f: &mut fmt::Formatter<'_>,
+        pat: &crate::pat::DeconstructedPat<'_, Self>,
+    ) -> fmt::Result {
+        Self::debug_pat(f, pat)
+    }
+    fn bug(&self, fmt: fmt::Arguments<'_>) -> ! {
+        span_bug!(self.scrut_span, "{}", fmt)
+    }
+}
+
 /// Recursively expand this pattern into its subpatterns. Only useful for or-patterns.
 fn expand_or_pat<'p, 'tcx>(pat: &'p Pat<'tcx>) -> Vec<&'p Pat<'tcx>> {
     fn expand<'p, 'tcx>(pat: &'p Pat<'tcx>, vec: &mut Vec<&'p Pat<'tcx>>) {
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs
index f268a551547..6b1de807797 100644
--- a/compiler/rustc_pattern_analysis/src/usefulness.rs
+++ b/compiler/rustc_pattern_analysis/src/usefulness.rs
@@ -242,7 +242,7 @@
 //! Therefore `usefulness(tp_1, tp_2, tq)` returns the single witness-tuple `[Variant2(Some(true), 0)]`.
 //!
 //!
-//! Computing the set of constructors for a type is done in [`MatchCheckCtxt::ctors_for_ty`]. See
+//! Computing the set of constructors for a type is done in [`TypeCx::ctors_for_ty`]. See
 //! the following sections for more accurate versions of the algorithm and corresponding links.
 //!
 //!
@@ -555,37 +555,52 @@
 use smallvec::{smallvec, SmallVec};
 use std::fmt;
 
-use rustc_data_structures::{captures::Captures, stack::ensure_sufficient_stack};
-use rustc_middle::ty::{self, Ty};
-use rustc_span::{Span, DUMMY_SP};
-
 use crate::constructor::{Constructor, ConstructorSet};
-use crate::cx::MatchCheckCtxt;
 use crate::pat::{DeconstructedPat, WitnessPat};
-use crate::MatchArm;
+use crate::{Captures, MatchArm, MatchCtxt, TypeCx, TypedArena};
 
 use self::ValidityConstraint::*;
 
-#[derive(Copy, Clone)]
-pub(crate) struct PatCtxt<'a, 'p, 'tcx> {
-    pub(crate) cx: &'a MatchCheckCtxt<'p, 'tcx>,
-    /// Type of the current column under investigation.
-    pub(crate) ty: Ty<'tcx>,
-    /// Whether the current pattern is the whole pattern as found in a match arm, or if it's a
-    /// subpattern.
-    pub(crate) is_top_level: bool,
+#[cfg(feature = "rustc")]
+use rustc_data_structures::stack::ensure_sufficient_stack;
+#[cfg(not(feature = "rustc"))]
+pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
+    f()
 }
 
-impl<'a, 'p, 'tcx> PatCtxt<'a, 'p, 'tcx> {
-    /// A `PatCtxt` when code other than `is_useful` needs one.
-    pub(crate) fn new_dummy(cx: &'a MatchCheckCtxt<'p, 'tcx>, ty: Ty<'tcx>) -> Self {
-        PatCtxt { cx, ty, is_top_level: false }
+/// Context that provides information local to a place under investigation.
+#[derive(Clone)]
+pub(crate) struct PlaceCtxt<'a, 'p, Cx: TypeCx> {
+    pub(crate) mcx: MatchCtxt<'a, 'p, Cx>,
+    /// Type of the place under investigation.
+    pub(crate) ty: Cx::Ty,
+    /// Whether the place is the original scrutinee place, as opposed to a subplace of it.
+    pub(crate) is_scrutinee: bool,
+}
+
+impl<'a, 'p, Cx: TypeCx> PlaceCtxt<'a, 'p, Cx> {
+    /// A `PlaceCtxt` when code other than `is_useful` needs one.
+    #[cfg_attr(not(feature = "rustc"), allow(dead_code))]
+    pub(crate) fn new_dummy(mcx: MatchCtxt<'a, 'p, Cx>, ty: Cx::Ty) -> Self {
+        PlaceCtxt { mcx, ty, is_scrutinee: false }
+    }
+
+    pub(crate) fn ctor_arity(&self, ctor: &Constructor<Cx>) -> usize {
+        self.mcx.tycx.ctor_arity(ctor, self.ty)
+    }
+    pub(crate) fn ctor_sub_tys(&self, ctor: &Constructor<Cx>) -> &[Cx::Ty] {
+        self.mcx.tycx.ctor_sub_tys(ctor, self.ty)
+    }
+    pub(crate) fn ctors_for_ty(&self) -> ConstructorSet<Cx> {
+        self.mcx.tycx.ctors_for_ty(self.ty)
     }
 }
 
-impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> Copy for PlaceCtxt<'a, 'p, Cx> {}
+
+impl<'a, 'p, Cx: TypeCx> fmt::Debug for PlaceCtxt<'a, 'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("PatCtxt").field("ty", &self.ty).finish()
+        f.debug_struct("PlaceCtxt").field("ty", &self.ty).finish()
     }
 }
 
@@ -595,7 +610,7 @@ impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> {
 /// - in the matrix, track whether a given place (aka column) is known to contain a valid value or
 ///     not.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-enum ValidityConstraint {
+pub enum ValidityConstraint {
     ValidOnly,
     MaybeInvalid,
     /// Option for backwards compatibility: the place is not known to be valid but we allow omitting
@@ -604,7 +619,7 @@ enum ValidityConstraint {
 }
 
 impl ValidityConstraint {
-    fn from_bool(is_valid_only: bool) -> Self {
+    pub fn from_bool(is_valid_only: bool) -> Self {
         if is_valid_only { ValidOnly } else { MaybeInvalid }
     }
 
@@ -629,12 +644,9 @@ impl ValidityConstraint {
     ///
     /// Pending further opsem decisions, the current behavior is: validity is preserved, except
     /// inside `&` and union fields where validity is reset to `MaybeInvalid`.
-    fn specialize<'tcx>(self, pcx: &PatCtxt<'_, '_, 'tcx>, ctor: &Constructor<'tcx>) -> Self {
+    fn specialize<Cx: TypeCx>(self, ctor: &Constructor<Cx>) -> Self {
         // We preserve validity except when we go inside a reference or a union field.
-        if matches!(ctor, Constructor::Single)
-            && (matches!(pcx.ty.kind(), ty::Ref(..))
-                || matches!(pcx.ty.kind(), ty::Adt(def, ..) if def.is_union()))
-        {
+        if matches!(ctor, Constructor::Ref | Constructor::UnionField) {
             // Validity of `x: &T` does not imply validity of `*x: T`.
             MaybeInvalid
         } else {
@@ -654,14 +666,18 @@ impl fmt::Display for ValidityConstraint {
 }
 
 /// Represents a pattern-tuple under investigation.
+// The three lifetimes are:
+// - 'a allocated by us
+// - 'p coming from the input
+// - Cx global compilation context
 #[derive(Clone)]
-struct PatStack<'p, 'tcx> {
+struct PatStack<'a, 'p, Cx: TypeCx> {
     // Rows of len 1 are very common, which is why `SmallVec[_; 2]` works well.
-    pats: SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]>,
+    pats: SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]>,
 }
 
-impl<'p, 'tcx> PatStack<'p, 'tcx> {
-    fn from_pattern(pat: &'p DeconstructedPat<'p, 'tcx>) -> Self {
+impl<'a, 'p, Cx: TypeCx> PatStack<'a, 'p, Cx> {
+    fn from_pattern(pat: &'a DeconstructedPat<'p, Cx>) -> Self {
         PatStack { pats: smallvec![pat] }
     }
 
@@ -673,17 +689,17 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
         self.pats.len()
     }
 
-    fn head(&self) -> &'p DeconstructedPat<'p, 'tcx> {
+    fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
         self.pats[0]
     }
 
-    fn iter(&self) -> impl Iterator<Item = &DeconstructedPat<'p, 'tcx>> {
+    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
         self.pats.iter().copied()
     }
 
     // Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
     // an or-pattern. Panics if `self` is empty.
-    fn expand_or_pat<'a>(&'a self) -> impl Iterator<Item = PatStack<'p, 'tcx>> + Captures<'a> {
+    fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = PatStack<'a, 'p, Cx>> + Captures<'b> {
         self.head().flatten_or_pat().into_iter().map(move |pat| {
             let mut new = self.clone();
             new.pats[0] = pat;
@@ -695,9 +711,9 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PatCtxt<'_, 'p, 'tcx>,
-        ctor: &Constructor<'tcx>,
-    ) -> PatStack<'p, 'tcx> {
+        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        ctor: &Constructor<Cx>,
+    ) -> PatStack<'a, 'p, Cx> {
         // We pop the head pattern and push the new fields extracted from the arguments of
         // `self.head()`.
         let mut new_pats = self.head().specialize(pcx, ctor);
@@ -706,7 +722,7 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
     }
 }
 
-impl<'p, 'tcx> fmt::Debug for PatStack<'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> fmt::Debug for PatStack<'a, 'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // We pretty-print similarly to the `Debug` impl of `Matrix`.
         write!(f, "+")?;
@@ -719,9 +735,9 @@ impl<'p, 'tcx> fmt::Debug for PatStack<'p, 'tcx> {
 
 /// A row of the matrix.
 #[derive(Clone)]
-struct MatrixRow<'p, 'tcx> {
+struct MatrixRow<'a, 'p, Cx: TypeCx> {
     // The patterns in the row.
-    pats: PatStack<'p, 'tcx>,
+    pats: PatStack<'a, 'p, Cx>,
     /// Whether the original arm had a guard. This is inherited when specializing.
     is_under_guard: bool,
     /// When we specialize, we remember which row of the original matrix produced a given row of the
@@ -734,7 +750,7 @@ struct MatrixRow<'p, 'tcx> {
     useful: bool,
 }
 
-impl<'p, 'tcx> MatrixRow<'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> MatrixRow<'a, 'p, Cx> {
     fn is_empty(&self) -> bool {
         self.pats.is_empty()
     }
@@ -743,17 +759,17 @@ impl<'p, 'tcx> MatrixRow<'p, 'tcx> {
         self.pats.len()
     }
 
-    fn head(&self) -> &'p DeconstructedPat<'p, 'tcx> {
+    fn head(&self) -> &'a DeconstructedPat<'p, Cx> {
         self.pats.head()
     }
 
-    fn iter(&self) -> impl Iterator<Item = &DeconstructedPat<'p, 'tcx>> {
+    fn iter<'b>(&'b self) -> impl Iterator<Item = &'a DeconstructedPat<'p, Cx>> + Captures<'b> {
         self.pats.iter()
     }
 
     // Recursively expand the first or-pattern into its subpatterns. Only useful if the pattern is
     // an or-pattern. Panics if `self` is empty.
-    fn expand_or_pat<'a>(&'a self) -> impl Iterator<Item = MatrixRow<'p, 'tcx>> + Captures<'a> {
+    fn expand_or_pat<'b>(&'b self) -> impl Iterator<Item = MatrixRow<'a, 'p, Cx>> + Captures<'b> {
         self.pats.expand_or_pat().map(|patstack| MatrixRow {
             pats: patstack,
             parent_row: self.parent_row,
@@ -766,10 +782,10 @@ impl<'p, 'tcx> MatrixRow<'p, 'tcx> {
     /// Only call if `ctor.is_covered_by(self.head().ctor())` is true.
     fn pop_head_constructor(
         &self,
-        pcx: &PatCtxt<'_, 'p, 'tcx>,
-        ctor: &Constructor<'tcx>,
+        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        ctor: &Constructor<Cx>,
         parent_row: usize,
-    ) -> MatrixRow<'p, 'tcx> {
+    ) -> MatrixRow<'a, 'p, Cx> {
         MatrixRow {
             pats: self.pats.pop_head_constructor(pcx, ctor),
             parent_row,
@@ -779,7 +795,7 @@ impl<'p, 'tcx> MatrixRow<'p, 'tcx> {
     }
 }
 
-impl<'p, 'tcx> fmt::Debug for MatrixRow<'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> fmt::Debug for MatrixRow<'a, 'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.pats.fmt(f)
     }
@@ -796,22 +812,22 @@ impl<'p, 'tcx> fmt::Debug for MatrixRow<'p, 'tcx> {
 /// specializing `(,)` and `Some` on a pattern of type `(Option<u32>, bool)`, the first column of
 /// the matrix will correspond to `scrutinee.0.Some.0` and the second column to `scrutinee.1`.
 #[derive(Clone)]
-struct Matrix<'p, 'tcx> {
+struct Matrix<'a, 'p, Cx: TypeCx> {
     /// Vector of rows. The rows must form a rectangular 2D array. Moreover, all the patterns of
     /// each column must have the same type. Each column corresponds to a place within the
     /// scrutinee.
-    rows: Vec<MatrixRow<'p, 'tcx>>,
+    rows: Vec<MatrixRow<'a, 'p, Cx>>,
     /// Stores an extra fictitious row full of wildcards. Mostly used to keep track of the type of
     /// each column. This must obey the same invariants as the real rows.
-    wildcard_row: PatStack<'p, 'tcx>,
+    wildcard_row: PatStack<'a, 'p, Cx>,
     /// Track for each column/place whether it contains a known valid value.
     place_validity: SmallVec<[ValidityConstraint; 2]>,
 }
 
-impl<'p, 'tcx> Matrix<'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
     /// Pushes a new row to the matrix. If the row starts with an or-pattern, this recursively
     /// expands it. Internal method, prefer [`Matrix::new`].
-    fn expand_and_push(&mut self, row: MatrixRow<'p, 'tcx>) {
+    fn expand_and_push(&mut self, row: MatrixRow<'a, 'p, Cx>) {
         if !row.is_empty() && row.head().is_or_pat() {
             // Expand nested or-patterns.
             for new_row in row.expand_or_pat() {
@@ -823,16 +839,14 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
     }
 
     /// Build a new matrix from an iterator of `MatchArm`s.
-    fn new<'a>(
-        cx: &MatchCheckCtxt<'p, 'tcx>,
-        arms: &[MatchArm<'p, 'tcx>],
-        scrut_ty: Ty<'tcx>,
+    fn new(
+        wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
+        arms: &'a [MatchArm<'p, Cx>],
+        scrut_ty: Cx::Ty,
         scrut_validity: ValidityConstraint,
-    ) -> Self
-    where
-        'p: 'a,
-    {
-        let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty, DUMMY_SP));
+    ) -> Self {
+        let wild_pattern =
+            wildcard_arena.alloc(DeconstructedPat::wildcard(scrut_ty, Default::default()));
         let wildcard_row = PatStack::from_pattern(wild_pattern);
         let mut matrix = Matrix {
             rows: Vec::with_capacity(arms.len()),
@@ -851,7 +865,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
         matrix
     }
 
-    fn head_ty(&self) -> Option<Ty<'tcx>> {
+    fn head_ty(&self) -> Option<Cx::Ty> {
         if self.column_count() == 0 {
             return None;
         }
@@ -859,11 +873,10 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
         let mut ty = self.wildcard_row.head().ty();
         // If the type is opaque and it is revealed anywhere in the column, we take the revealed
         // version. Otherwise we could encounter constructors for the revealed type and crash.
-        let is_opaque = |ty: Ty<'tcx>| matches!(ty.kind(), ty::Alias(ty::Opaque, ..));
-        if is_opaque(ty) {
+        if Cx::is_opaque_ty(ty) {
             for pat in self.heads() {
                 let pat_ty = pat.ty();
-                if !is_opaque(pat_ty) {
+                if !Cx::is_opaque_ty(pat_ty) {
                     ty = pat_ty;
                     break;
                 }
@@ -875,34 +888,34 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
         self.wildcard_row.len()
     }
 
-    fn rows<'a>(
-        &'a self,
-    ) -> impl Iterator<Item = &'a MatrixRow<'p, 'tcx>> + Clone + DoubleEndedIterator + ExactSizeIterator
+    fn rows<'b>(
+        &'b self,
+    ) -> impl Iterator<Item = &'b MatrixRow<'a, 'p, Cx>> + Clone + DoubleEndedIterator + ExactSizeIterator
     {
         self.rows.iter()
     }
-    fn rows_mut<'a>(
-        &'a mut self,
-    ) -> impl Iterator<Item = &'a mut MatrixRow<'p, 'tcx>> + DoubleEndedIterator + ExactSizeIterator
+    fn rows_mut<'b>(
+        &'b mut self,
+    ) -> impl Iterator<Item = &'b mut MatrixRow<'a, 'p, Cx>> + DoubleEndedIterator + ExactSizeIterator
     {
         self.rows.iter_mut()
     }
 
     /// Iterate over the first pattern of each row.
-    fn heads<'a>(
-        &'a self,
-    ) -> impl Iterator<Item = &'p DeconstructedPat<'p, 'tcx>> + Clone + Captures<'a> {
+    fn heads<'b>(
+        &'b self,
+    ) -> impl Iterator<Item = &'b DeconstructedPat<'p, Cx>> + Clone + Captures<'a> {
         self.rows().map(|r| r.head())
     }
 
     /// This computes `specialize(ctor, self)`. See top of the file for explanations.
     fn specialize_constructor(
         &self,
-        pcx: &PatCtxt<'_, 'p, 'tcx>,
-        ctor: &Constructor<'tcx>,
-    ) -> Matrix<'p, 'tcx> {
+        pcx: &PlaceCtxt<'a, 'p, Cx>,
+        ctor: &Constructor<Cx>,
+    ) -> Matrix<'a, 'p, Cx> {
         let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor);
-        let new_validity = self.place_validity[0].specialize(pcx, ctor);
+        let new_validity = self.place_validity[0].specialize(ctor);
         let new_place_validity = std::iter::repeat(new_validity)
             .take(ctor.arity(pcx))
             .chain(self.place_validity[1..].iter().copied())
@@ -929,7 +942,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
 /// + _     + [_, _, tail @ ..] +
 /// | ✓     | ?                 | // column validity
 /// ```
-impl<'p, 'tcx> fmt::Debug for Matrix<'p, 'tcx> {
+impl<'a, 'p, Cx: TypeCx> fmt::Debug for Matrix<'a, 'p, Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "\n")?;
 
@@ -1020,17 +1033,17 @@ impl<'p, 'tcx> fmt::Debug for Matrix<'p, 'tcx> {
 ///
 /// See the top of the file for more detailed explanations and examples.
 #[derive(Debug, Clone)]
-struct WitnessStack<'tcx>(Vec<WitnessPat<'tcx>>);
+struct WitnessStack<Cx: TypeCx>(Vec<WitnessPat<Cx>>);
 
-impl<'tcx> WitnessStack<'tcx> {
+impl<Cx: TypeCx> WitnessStack<Cx> {
     /// Asserts that the witness contains a single pattern, and returns it.
-    fn single_pattern(self) -> WitnessPat<'tcx> {
+    fn single_pattern(self) -> WitnessPat<Cx> {
         assert_eq!(self.0.len(), 1);
         self.0.into_iter().next().unwrap()
     }
 
     /// Reverses specialization by the `Missing` constructor by pushing a whole new pattern.
-    fn push_pattern(&mut self, pat: WitnessPat<'tcx>) {
+    fn push_pattern(&mut self, pat: WitnessPat<Cx>) {
         self.0.push(pat);
     }
 
@@ -1048,7 +1061,7 @@ impl<'tcx> WitnessStack<'tcx> {
     /// pats: [(false, "foo"), _, true]
     /// result: [Enum::Variant { a: (false, "foo"), b: _ }, true]
     /// ```
-    fn apply_constructor(&mut self, pcx: &PatCtxt<'_, '_, 'tcx>, ctor: &Constructor<'tcx>) {
+    fn apply_constructor(&mut self, pcx: &PlaceCtxt<'_, '_, Cx>, ctor: &Constructor<Cx>) {
         let len = self.0.len();
         let arity = ctor.arity(pcx);
         let fields = self.0.drain((len - arity)..).rev().collect();
@@ -1067,9 +1080,9 @@ impl<'tcx> WitnessStack<'tcx> {
 /// Just as the `Matrix` starts with a single column, by the end of the algorithm, this has a single
 /// column, which contains the patterns that are missing for the match to be exhaustive.
 #[derive(Debug, Clone)]
-struct WitnessMatrix<'tcx>(Vec<WitnessStack<'tcx>>);
+struct WitnessMatrix<Cx: TypeCx>(Vec<WitnessStack<Cx>>);
 
-impl<'tcx> WitnessMatrix<'tcx> {
+impl<Cx: TypeCx> WitnessMatrix<Cx> {
     /// New matrix with no witnesses.
     fn empty() -> Self {
         WitnessMatrix(vec![])
@@ -1084,12 +1097,12 @@ impl<'tcx> WitnessMatrix<'tcx> {
         self.0.is_empty()
     }
     /// Asserts that there is a single column and returns the patterns in it.
-    fn single_column(self) -> Vec<WitnessPat<'tcx>> {
+    fn single_column(self) -> Vec<WitnessPat<Cx>> {
         self.0.into_iter().map(|w| w.single_pattern()).collect()
     }
 
     /// Reverses specialization by the `Missing` constructor by pushing a whole new pattern.
-    fn push_pattern(&mut self, pat: WitnessPat<'tcx>) {
+    fn push_pattern(&mut self, pat: WitnessPat<Cx>) {
         for witness in self.0.iter_mut() {
             witness.push_pattern(pat.clone())
         }
@@ -1098,9 +1111,9 @@ impl<'tcx> WitnessMatrix<'tcx> {
     /// Reverses specialization by `ctor`. See the section on `unspecialize` at the top of the file.
     fn apply_constructor(
         &mut self,
-        pcx: &PatCtxt<'_, '_, 'tcx>,
-        missing_ctors: &[Constructor<'tcx>],
-        ctor: &Constructor<'tcx>,
+        pcx: &PlaceCtxt<'_, '_, Cx>,
+        missing_ctors: &[Constructor<Cx>],
+        ctor: &Constructor<Cx>,
         report_individual_missing_ctors: bool,
     ) {
         if self.is_empty() {
@@ -1160,12 +1173,12 @@ impl<'tcx> WitnessMatrix<'tcx> {
 /// - unspecialization, where we lift the results from the previous step into results for this step
 ///     (using `apply_constructor` and by updating `row.useful` for each parent row).
 /// This is all explained at the top of the file.
-#[instrument(level = "debug", skip(cx, is_top_level), ret)]
-fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
-    matrix: &mut Matrix<'p, 'tcx>,
+#[instrument(level = "debug", skip(mcx, is_top_level), ret)]
+fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
+    mcx: MatchCtxt<'a, 'p, Cx>,
+    matrix: &mut Matrix<'a, 'p, Cx>,
     is_top_level: bool,
-) -> WitnessMatrix<'tcx> {
+) -> WitnessMatrix<Cx> {
     debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));
 
     let Some(ty) = matrix.head_ty() else {
@@ -1185,7 +1198,7 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
     };
 
     debug!("ty: {ty:?}");
-    let pcx = &PatCtxt { cx, ty, is_top_level };
+    let pcx = &PlaceCtxt { mcx, ty, is_scrutinee: is_top_level };
 
     // Whether the place/column we are inspecting is known to contain valid data.
     let place_validity = matrix.place_validity[0];
@@ -1194,7 +1207,7 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
 
     // Analyze the constructors present in this column.
     let ctors = matrix.heads().map(|p| p.ctor());
-    let ctors_for_ty = &cx.ctors_for_ty(ty);
+    let ctors_for_ty = pcx.ctors_for_ty();
     let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
     let split_set = ctors_for_ty.split(pcx, ctors);
     let all_missing = split_set.present.is_empty();
@@ -1228,7 +1241,7 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
         // Dig into rows that match `ctor`.
         let mut spec_matrix = matrix.specialize_constructor(pcx, &ctor);
         let mut witnesses = ensure_sufficient_stack(|| {
-            compute_exhaustiveness_and_usefulness(cx, &mut spec_matrix, false)
+            compute_exhaustiveness_and_usefulness(mcx, &mut spec_matrix, false)
         });
 
         let counts_for_exhaustiveness = match ctor {
@@ -1270,34 +1283,34 @@ fn compute_exhaustiveness_and_usefulness<'p, 'tcx>(
 
 /// Indicates whether or not a given arm is useful.
 #[derive(Clone, Debug)]
-pub enum Usefulness {
+pub enum Usefulness<'p, Cx: TypeCx> {
     /// The arm is useful. This additionally carries a set of or-pattern branches that have been
     /// found to be redundant despite the overall arm being useful. Used only in the presence of
     /// or-patterns, otherwise it stays empty.
-    Useful(Vec<Span>),
+    Useful(Vec<&'p DeconstructedPat<'p, Cx>>),
     /// The arm is redundant and can be removed without changing the behavior of the match
     /// expression.
     Redundant,
 }
 
 /// The output of checking a match for exhaustiveness and arm usefulness.
-pub struct UsefulnessReport<'p, 'tcx> {
+pub struct UsefulnessReport<'p, Cx: TypeCx> {
     /// For each arm of the input, whether that arm is useful after the arms above it.
-    pub arm_usefulness: Vec<(MatchArm<'p, 'tcx>, Usefulness)>,
+    pub arm_usefulness: Vec<(MatchArm<'p, Cx>, Usefulness<'p, Cx>)>,
     /// If the match is exhaustive, this is empty. If not, this contains witnesses for the lack of
     /// exhaustiveness.
-    pub non_exhaustiveness_witnesses: Vec<WitnessPat<'tcx>>,
+    pub non_exhaustiveness_witnesses: Vec<WitnessPat<Cx>>,
 }
 
 /// Computes whether a match is exhaustive and which of its arms are useful.
 #[instrument(skip(cx, arms), level = "debug")]
-pub(crate) fn compute_match_usefulness<'p, 'tcx>(
-    cx: &MatchCheckCtxt<'p, 'tcx>,
-    arms: &[MatchArm<'p, 'tcx>],
-    scrut_ty: Ty<'tcx>,
-) -> UsefulnessReport<'p, 'tcx> {
-    let scrut_validity = ValidityConstraint::from_bool(cx.known_valid_scrutinee);
-    let mut matrix = Matrix::new(cx, arms, scrut_ty, scrut_validity);
+pub fn compute_match_usefulness<'p, Cx: TypeCx>(
+    cx: MatchCtxt<'_, 'p, Cx>,
+    arms: &[MatchArm<'p, Cx>],
+    scrut_ty: Cx::Ty,
+    scrut_validity: ValidityConstraint,
+) -> UsefulnessReport<'p, Cx> {
+    let mut matrix = Matrix::new(cx.wildcard_arena, arms, scrut_ty, scrut_validity);
     let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(cx, &mut matrix, true);
 
     let non_exhaustiveness_witnesses: Vec<_> = non_exhaustiveness_witnesses.single_column();
@@ -1308,7 +1321,7 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>(
             debug!(?arm);
             // We warn when a pattern is not useful.
             let usefulness = if arm.pat.is_useful() {
-                Usefulness::Useful(arm.pat.redundant_spans())
+                Usefulness::Useful(arm.pat.redundant_subpatterns())
             } else {
                 Usefulness::Redundant
             };
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index ad637472b47..670fdcfb0d2 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1084,7 +1084,7 @@ pub struct Resolver<'a, 'tcx> {
 
     next_node_id: NodeId,
 
-    node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
+    node_id_to_def_id: NodeMap<LocalDefId>,
     def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
 
     /// Indices of unnamed struct or variant fields with unresolved attributes.
@@ -1296,7 +1296,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         let mut def_id_to_node_id = IndexVec::default();
         assert_eq!(def_id_to_node_id.push(CRATE_NODE_ID), CRATE_DEF_ID);
-        let mut node_id_to_def_id = FxHashMap::default();
+        let mut node_id_to_def_id = NodeMap::default();
         node_id_to_def_id.insert(CRATE_NODE_ID, CRATE_DEF_ID);
 
         let mut invocation_parents = FxHashMap::default();
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
index 41ab4007a67..49bf2192f82 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/mir.rs
@@ -37,6 +37,7 @@ impl<'tcx> Stable<'tcx> for mir::Body<'tcx> {
             self.arg_count,
             self.var_debug_info.iter().map(|info| info.stable(tables)).collect(),
             self.spread_arg.stable(tables),
+            self.span.stable(tables),
         )
     }
 }
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index a78df69f187..b688c97311a 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1578,6 +1578,7 @@ supported_targets! {
     ("armv7k-apple-watchos", armv7k_apple_watchos),
     ("arm64_32-apple-watchos", arm64_32_apple_watchos),
     ("x86_64-apple-watchos-sim", x86_64_apple_watchos_sim),
+    ("aarch64-apple-watchos", aarch64_apple_watchos),
     ("aarch64-apple-watchos-sim", aarch64_apple_watchos_sim),
 
     ("armebv7r-none-eabi", armebv7r_none_eabi),
diff --git a/compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs b/compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs
new file mode 100644
index 00000000000..b62666dcc7e
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs
@@ -0,0 +1,19 @@
+use crate::spec::base::apple::{opts, Arch};
+use crate::spec::{Target, TargetOptions};
+
+pub fn target() -> Target {
+    let base = opts("watchos", Arch::Arm64);
+    Target {
+        llvm_target: "aarch-apple-watchos".into(),
+        pointer_width: 64,
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        arch: "aarch64".into(),
+        options: TargetOptions {
+            features: "+v8a,+neon,+fp-armv8,+apple-a7".into(),
+            max_atomic_width: Some(128),
+            dynamic_linking: false,
+            position_independent_executables: true,
+            ..base
+        },
+    }
+}
diff --git a/compiler/rustc_trait_selection/src/solve/alias_relate.rs b/compiler/rustc_trait_selection/src/solve/alias_relate.rs
index 2e99854ddc6..626569fb40f 100644
--- a/compiler/rustc_trait_selection/src/solve/alias_relate.rs
+++ b/compiler/rustc_trait_selection/src/solve/alias_relate.rs
@@ -11,7 +11,7 @@
 //! * bidirectional-normalizes-to: If `A` and `B` are both projections, and both
 //!   may apply, then we can compute the "intersection" of both normalizes-to by
 //!   performing them together. This is used specifically to resolve ambiguities.
-use super::EvalCtxt;
+use super::{EvalCtxt, GoalSource};
 use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::traits::query::NoSolution;
 use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
@@ -89,11 +89,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             ty::TermKind::Const(_) => {
                 if let Some(alias) = term.to_alias_ty(self.tcx()) {
                     let term = self.next_term_infer_of_kind(term);
-                    self.add_goal(Goal::new(
-                        self.tcx(),
-                        param_env,
-                        ty::NormalizesTo { alias, term },
-                    ));
+                    self.add_goal(
+                        GoalSource::Misc,
+                        Goal::new(self.tcx(), param_env, ty::NormalizesTo { alias, term }),
+                    );
                     self.try_evaluate_added_goals()?;
                     Ok(Some(self.resolve_vars_if_possible(term)))
                 } else {
@@ -109,7 +108,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         opaque: ty::AliasTy<'tcx>,
         term: ty::Term<'tcx>,
     ) -> QueryResult<'tcx> {
-        self.add_goal(Goal::new(self.tcx(), param_env, ty::NormalizesTo { alias: opaque, term }));
+        self.add_goal(
+            GoalSource::Misc,
+            Goal::new(self.tcx(), param_env, ty::NormalizesTo { alias: opaque, term }),
+        );
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 62d62bdfd11..81a766f24b0 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -1,6 +1,7 @@
 //! Code shared by trait and projection goals for candidate assembly.
 
 use super::{EvalCtxt, SolverMode};
+use crate::solve::GoalSource;
 use crate::traits::coherence;
 use rustc_hir::def_id::DefId;
 use rustc_infer::traits::query::NoSolution;
@@ -62,7 +63,9 @@ pub(super) trait GoalKind<'tcx>:
         requirements: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
     ) -> QueryResult<'tcx> {
         Self::probe_and_match_goal_against_assumption(ecx, goal, assumption, |ecx| {
-            ecx.add_goals(requirements);
+            // FIXME(-Znext-solver=coinductive): check whether this should be
+            // `GoalSource::ImplWhereBound` for any caller.
+            ecx.add_goals(GoalSource::Misc, requirements);
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
     }
@@ -94,12 +97,16 @@ pub(super) trait GoalKind<'tcx>:
             let ty::Dynamic(bounds, _, _) = *goal.predicate.self_ty().kind() else {
                 bug!("expected object type in `consider_object_bound_candidate`");
             };
-            ecx.add_goals(structural_traits::predicates_for_object_candidate(
-                ecx,
-                goal.param_env,
-                goal.predicate.trait_ref(tcx),
-                bounds,
-            ));
+            // FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
+            ecx.add_goals(
+                GoalSource::Misc,
+                structural_traits::predicates_for_object_candidate(
+                    ecx,
+                    goal.param_env,
+                    goal.predicate.trait_ref(tcx),
+                    bounds,
+                ),
+            );
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
     }
@@ -364,7 +371,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 let normalized_ty = ecx.next_ty_infer();
                 let normalizes_to_goal =
                     goal.with(tcx, ty::NormalizesTo { alias, term: normalized_ty.into() });
-                ecx.add_goal(normalizes_to_goal);
+                ecx.add_goal(GoalSource::Misc, normalizes_to_goal);
                 if let Err(NoSolution) = ecx.try_evaluate_added_goals() {
                     debug!("self type normalization failed");
                     return vec![];
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
index 7457ba837f5..ecdae2521b9 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
@@ -94,20 +94,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         );
 
         let certainty = certainty.unify_with(goals_certainty);
-        if let Certainty::OVERFLOW = certainty {
-            // If we have overflow, it's probable that we're substituting a type
-            // into itself infinitely and any partial substitutions in the query
-            // response are probably not useful anyways, so just return an empty
-            // query response.
-            //
-            // This may prevent us from potentially useful inference, e.g.
-            // 2 candidates, one ambiguous and one overflow, which both
-            // have the same inference constraints.
-            //
-            // Changing this to retain some constraints in the future
-            // won't be a breaking change, so this is good enough for now.
-            return Ok(self.make_ambiguous_response_no_constraints(MaybeCause::Overflow));
-        }
 
         let var_values = self.var_values;
         let external_constraints = self.compute_external_query_constraints()?;
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
index cafb858794a..76c50a11102 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
@@ -23,14 +23,15 @@ use rustc_middle::ty::{
 use rustc_session::config::DumpSolverProofTree;
 use rustc_span::DUMMY_SP;
 use std::io::Write;
+use std::iter;
 use std::ops::ControlFlow;
 
 use crate::traits::vtable::{count_own_vtable_entries, prepare_vtable_segments, VtblSegment};
 
 use super::inspect::ProofTreeBuilder;
-use super::SolverMode;
 use super::{search_graph, GoalEvaluationKind};
 use super::{search_graph::SearchGraph, Goal};
+use super::{GoalSource, SolverMode};
 pub use select::InferCtxtSelectExt;
 
 mod canonical;
@@ -105,7 +106,7 @@ pub(super) struct NestedGoals<'tcx> {
     /// can be unsound with more powerful coinduction in the future.
     pub(super) normalizes_to_hack_goal: Option<Goal<'tcx, ty::NormalizesTo<'tcx>>>,
     /// The rest of the goals which have not yet processed or remain ambiguous.
-    pub(super) goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
+    pub(super) goals: Vec<(GoalSource, Goal<'tcx, ty::Predicate<'tcx>>)>,
 }
 
 impl<'tcx> NestedGoals<'tcx> {
@@ -156,7 +157,7 @@ impl<'tcx> InferCtxtEvalExt<'tcx> for InferCtxt<'tcx> {
         Option<inspect::GoalEvaluation<'tcx>>,
     ) {
         EvalCtxt::enter_root(self, generate_proof_tree, |ecx| {
-            ecx.evaluate_goal(GoalEvaluationKind::Root, goal)
+            ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal)
         })
     }
 }
@@ -334,6 +335,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
     fn evaluate_goal(
         &mut self,
         goal_evaluation_kind: GoalEvaluationKind,
+        source: GoalSource,
         goal: Goal<'tcx, ty::Predicate<'tcx>>,
     ) -> Result<(bool, Certainty, Vec<Goal<'tcx, ty::Predicate<'tcx>>>), NoSolution> {
         let (orig_values, canonical_goal) = self.canonicalize_goal(goal);
@@ -353,13 +355,13 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
             Ok(response) => response,
         };
 
-        let has_changed = !canonical_response.value.var_values.is_identity_modulo_regions()
-            || !canonical_response.value.external_constraints.opaque_types.is_empty();
-        let (certainty, nested_goals) = match self.instantiate_and_apply_query_response(
-            goal.param_env,
-            orig_values,
-            canonical_response,
-        ) {
+        let (certainty, has_changed, nested_goals) = match self
+            .instantiate_response_discarding_overflow(
+                goal.param_env,
+                source,
+                orig_values,
+                canonical_response,
+            ) {
             Err(e) => {
                 self.inspect.goal_evaluation(goal_evaluation);
                 return Err(e);
@@ -386,6 +388,44 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
         Ok((has_changed, certainty, nested_goals))
     }
 
+    fn instantiate_response_discarding_overflow(
+        &mut self,
+        param_env: ty::ParamEnv<'tcx>,
+        source: GoalSource,
+        original_values: Vec<ty::GenericArg<'tcx>>,
+        response: CanonicalResponse<'tcx>,
+    ) -> Result<(Certainty, bool, Vec<Goal<'tcx, ty::Predicate<'tcx>>>), NoSolution> {
+        // The old solver did not evaluate nested goals when normalizing.
+        // It returned the selection constraints allowing a `Projection`
+        // obligation to not hold in coherence while avoiding the fatal error
+        // from overflow.
+        //
+        // We match this behavior here by considering all constraints
+        // from nested goals which are not from where-bounds. We will already
+        // need to track which nested goals are required by impl where-bounds
+        // for coinductive cycles, so we simply reuse that here.
+        //
+        // While we could consider overflow constraints in more cases, this should
+        // not be necessary for backcompat and results in better perf. It also
+        // avoids a potential inconsistency which would otherwise require some
+        // tracking for root goals as well. See #119071 for an example.
+        let keep_overflow_constraints = || {
+            self.search_graph.current_goal_is_normalizes_to()
+                && source != GoalSource::ImplWhereBound
+        };
+
+        if response.value.certainty == Certainty::OVERFLOW && !keep_overflow_constraints() {
+            Ok((Certainty::OVERFLOW, false, Vec::new()))
+        } else {
+            let has_changed = !response.value.var_values.is_identity_modulo_regions()
+                || !response.value.external_constraints.opaque_types.is_empty();
+
+            let (certainty, nested_goals) =
+                self.instantiate_and_apply_query_response(param_env, original_values, response)?;
+            Ok((certainty, has_changed, nested_goals))
+        }
+    }
+
     fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult<'tcx> {
         let Goal { param_env, predicate } = goal;
         let kind = predicate.kind();
@@ -439,7 +479,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
         } else {
             let kind = self.infcx.instantiate_binder_with_placeholders(kind);
             let goal = goal.with(self.tcx(), ty::Binder::dummy(kind));
-            self.add_goal(goal);
+            self.add_goal(GoalSource::Misc, goal);
             self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         }
     }
@@ -488,6 +528,13 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
         let mut goals = core::mem::replace(&mut self.nested_goals, NestedGoals::new());
 
         self.inspect.evaluate_added_goals_loop_start();
+
+        fn with_misc_source<'tcx>(
+            it: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
+        ) -> impl Iterator<Item = (GoalSource, Goal<'tcx, ty::Predicate<'tcx>>)> {
+            iter::zip(iter::repeat(GoalSource::Misc), it)
+        }
+
         // If this loop did not result in any progress, what's our final certainty.
         let mut unchanged_certainty = Some(Certainty::Yes);
         if let Some(goal) = goals.normalizes_to_hack_goal.take() {
@@ -501,9 +548,10 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
 
             let (_, certainty, instantiate_goals) = self.evaluate_goal(
                 GoalEvaluationKind::Nested { is_normalizes_to_hack: IsNormalizesToHack::Yes },
+                GoalSource::Misc,
                 unconstrained_goal,
             )?;
-            self.nested_goals.goals.extend(instantiate_goals);
+            self.nested_goals.goals.extend(with_misc_source(instantiate_goals));
 
             // Finally, equate the goal's RHS with the unconstrained var.
             // We put the nested goals from this into goals instead of
@@ -512,7 +560,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
             // matters in practice, though.
             let eq_goals =
                 self.eq_and_get_goals(goal.param_env, goal.predicate.term, unconstrained_rhs)?;
-            goals.goals.extend(eq_goals);
+            goals.goals.extend(with_misc_source(eq_goals));
 
             // We only look at the `projection_ty` part here rather than
             // looking at the "has changed" return from evaluate_goal,
@@ -533,12 +581,13 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
             }
         }
 
-        for goal in goals.goals.drain(..) {
+        for (source, goal) in goals.goals.drain(..) {
             let (has_changed, certainty, instantiate_goals) = self.evaluate_goal(
                 GoalEvaluationKind::Nested { is_normalizes_to_hack: IsNormalizesToHack::No },
+                source,
                 goal,
             )?;
-            self.nested_goals.goals.extend(instantiate_goals);
+            self.nested_goals.goals.extend(with_misc_source(instantiate_goals));
             if has_changed {
                 unchanged_certainty = None;
             }
@@ -546,7 +595,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
             match certainty {
                 Certainty::Yes => {}
                 Certainty::Maybe(_) => {
-                    self.nested_goals.goals.push(goal);
+                    self.nested_goals.goals.push((source, goal));
                     unchanged_certainty = unchanged_certainty.map(|c| c.unify_with(certainty));
                 }
             }
@@ -670,7 +719,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             .at(&ObligationCause::dummy(), param_env)
             .eq(DefineOpaqueTypes::No, lhs, rhs)
             .map(|InferOk { value: (), obligations }| {
-                self.add_goals(obligations.into_iter().map(|o| o.into()));
+                self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
             })
             .map_err(|e| {
                 debug!(?e, "failed to equate");
@@ -689,7 +738,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             .at(&ObligationCause::dummy(), param_env)
             .sub(DefineOpaqueTypes::No, sub, sup)
             .map(|InferOk { value: (), obligations }| {
-                self.add_goals(obligations.into_iter().map(|o| o.into()));
+                self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
             })
             .map_err(|e| {
                 debug!(?e, "failed to subtype");
@@ -709,7 +758,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             .at(&ObligationCause::dummy(), param_env)
             .relate(DefineOpaqueTypes::No, lhs, variance, rhs)
             .map(|InferOk { value: (), obligations }| {
-                self.add_goals(obligations.into_iter().map(|o| o.into()));
+                self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
             })
             .map_err(|e| {
                 debug!(?e, "failed to relate");
@@ -842,7 +891,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             true,
             &mut obligations,
         )?;
-        self.add_goals(obligations.into_iter().map(|o| o.into()));
+        self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
         Ok(())
     }
 
@@ -862,7 +911,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             hidden_ty,
             &mut obligations,
         );
-        self.add_goals(obligations.into_iter().map(|o| o.into()));
+        self.add_goals(GoalSource::Misc, obligations.into_iter().map(|o| o.into()));
     }
 
     // Do something for each opaque/hidden pair defined with `def_id` in the
diff --git a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
index a287582dca7..6db53d6ddc4 100644
--- a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
+++ b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
@@ -119,7 +119,7 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
     ) {
         for step in &probe.steps {
             match step {
-                &inspect::ProbeStep::AddGoal(goal) => nested_goals.push(goal),
+                &inspect::ProbeStep::AddGoal(_source, goal) => nested_goals.push(goal),
                 inspect::ProbeStep::NestedProbe(ref probe) => {
                     // Nested probes have to prove goals added in their parent
                     // but do not leak them, so we truncate the added goals
diff --git a/compiler/rustc_trait_selection/src/solve/inspect/build.rs b/compiler/rustc_trait_selection/src/solve/inspect/build.rs
index c857aae572d..d8caef5b03f 100644
--- a/compiler/rustc_trait_selection/src/solve/inspect/build.rs
+++ b/compiler/rustc_trait_selection/src/solve/inspect/build.rs
@@ -7,7 +7,7 @@ use std::mem;
 
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{
-    CanonicalInput, Certainty, Goal, IsNormalizesToHack, QueryInput, QueryResult,
+    CanonicalInput, Certainty, Goal, GoalSource, IsNormalizesToHack, QueryInput, QueryResult,
 };
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::DumpSolverProofTree;
@@ -216,7 +216,7 @@ impl<'tcx> WipProbe<'tcx> {
 
 #[derive(Eq, PartialEq, Debug)]
 enum WipProbeStep<'tcx> {
-    AddGoal(inspect::CanonicalState<'tcx, Goal<'tcx, ty::Predicate<'tcx>>>),
+    AddGoal(GoalSource, inspect::CanonicalState<'tcx, Goal<'tcx, ty::Predicate<'tcx>>>),
     EvaluateGoals(WipAddedGoalsEvaluation<'tcx>),
     NestedProbe(WipProbe<'tcx>),
     CommitIfOkStart,
@@ -226,7 +226,7 @@ enum WipProbeStep<'tcx> {
 impl<'tcx> WipProbeStep<'tcx> {
     fn finalize(self) -> inspect::ProbeStep<'tcx> {
         match self {
-            WipProbeStep::AddGoal(goal) => inspect::ProbeStep::AddGoal(goal),
+            WipProbeStep::AddGoal(source, goal) => inspect::ProbeStep::AddGoal(source, goal),
             WipProbeStep::EvaluateGoals(eval) => inspect::ProbeStep::EvaluateGoals(eval.finalize()),
             WipProbeStep::NestedProbe(probe) => inspect::ProbeStep::NestedProbe(probe.finalize()),
             WipProbeStep::CommitIfOkStart => inspect::ProbeStep::CommitIfOkStart,
@@ -428,7 +428,11 @@ impl<'tcx> ProofTreeBuilder<'tcx> {
         }
     }
 
-    pub fn add_goal(ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, ty::Predicate<'tcx>>) {
+    pub fn add_goal(
+        ecx: &mut EvalCtxt<'_, 'tcx>,
+        source: GoalSource,
+        goal: Goal<'tcx, ty::Predicate<'tcx>>,
+    ) {
         // Can't use `if let Some(this) = ecx.inspect.as_mut()` here because
         // we have to immutably use the `EvalCtxt` for `make_canonical_state`.
         if ecx.inspect.is_noop() {
@@ -442,7 +446,9 @@ impl<'tcx> ProofTreeBuilder<'tcx> {
                 evaluation: WipProbe { steps, .. },
                 ..
             })
-            | DebugSolver::Probe(WipProbe { steps, .. }) => steps.push(WipProbeStep::AddGoal(goal)),
+            | DebugSolver::Probe(WipProbe { steps, .. }) => {
+                steps.push(WipProbeStep::AddGoal(source, goal))
+            }
             s => unreachable!("tried to add {goal:?} to {s:?}"),
         }
     }
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 1e58106e353..2f3111a2414 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -19,8 +19,8 @@ use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::traits::query::NoSolution;
 use rustc_middle::infer::canonical::CanonicalVarInfos;
 use rustc_middle::traits::solve::{
-    CanonicalResponse, Certainty, ExternalConstraintsData, Goal, IsNormalizesToHack, QueryResult,
-    Response,
+    CanonicalResponse, Certainty, ExternalConstraintsData, Goal, GoalSource, IsNormalizesToHack,
+    QueryResult, Response,
 };
 use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, UniverseIndex};
 use rustc_middle::ty::{
@@ -157,7 +157,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
     ) -> QueryResult<'tcx> {
         match self.well_formed_goals(goal.param_env, goal.predicate) {
             Some(goals) => {
-                self.add_goals(goals);
+                self.add_goals(GoalSource::Misc, goals);
                 self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
             }
             None => self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS),
@@ -223,15 +223,19 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self))]
-    fn add_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) {
-        inspect::ProofTreeBuilder::add_goal(self, goal);
-        self.nested_goals.goals.push(goal);
+    fn add_goal(&mut self, source: GoalSource, goal: Goal<'tcx, ty::Predicate<'tcx>>) {
+        inspect::ProofTreeBuilder::add_goal(self, source, goal);
+        self.nested_goals.goals.push((source, goal));
     }
 
     #[instrument(level = "debug", skip(self, goals))]
-    fn add_goals(&mut self, goals: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>) {
+    fn add_goals(
+        &mut self,
+        source: GoalSource,
+        goals: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
+    ) {
         for goal in goals {
-            self.add_goal(goal);
+            self.add_goal(source, goal);
         }
     }
 
@@ -335,7 +339,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 param_env,
                 ty::NormalizesTo { alias, term: normalized_ty.into() },
             );
-            this.add_goal(normalizes_to_goal);
+            this.add_goal(GoalSource::Misc, normalizes_to_goal);
             this.try_evaluate_added_goals()?;
             let ty = this.resolve_vars_if_possible(normalized_ty);
             Ok(this.try_normalize_ty_recur(param_env, define_opaque_types, depth + 1, ty))
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/inherent.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/inherent.rs
index c3b8ae9a943..b2dff9b48ff 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/inherent.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/inherent.rs
@@ -4,10 +4,10 @@
 //! 1. instantiate substs,
 //! 2. equate the self type, and
 //! 3. instantiate and register where clauses.
-use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
+use rustc_middle::traits::solve::{Certainty, Goal, GoalSource, QueryResult};
 use rustc_middle::ty;
 
-use super::EvalCtxt;
+use crate::solve::EvalCtxt;
 
 impl<'tcx> EvalCtxt<'_, 'tcx> {
     pub(super) fn normalize_inherent_associated_type(
@@ -38,7 +38,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         .expect("expected goal term to be fully unconstrained");
 
         // Check both where clauses on the impl and IAT
+        //
+        // FIXME(-Znext-solver=coinductive): I think this should be split
+        // and we tag the impl bounds with `GoalSource::ImplWhereBound`?
+        // Right not this includes both the impl and the assoc item where bounds,
+        // and I don't think the assoc item where-bounds are allowed to be coinductive.
         self.add_goals(
+            GoalSource::Misc,
             tcx.predicates_of(inherent.def_id)
                 .instantiate(tcx, inherent_substs)
                 .into_iter()
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
index 980ef862366..0e9656a1e18 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
@@ -1,7 +1,7 @@
 use crate::traits::{check_args_compatible, specialization_graph};
 
 use super::assembly::{self, structural_traits, Candidate};
-use super::EvalCtxt;
+use super::{EvalCtxt, GoalSource};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
@@ -128,6 +128,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
 
                     // Add GAT where clauses from the trait's definition
                     ecx.add_goals(
+                        GoalSource::Misc,
                         tcx.predicates_of(goal.predicate.def_id())
                             .instantiate_own(tcx, goal.predicate.alias.args)
                             .map(|(pred, _)| goal.with(tcx, pred)),
@@ -169,10 +170,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 .predicates
                 .into_iter()
                 .map(|pred| goal.with(tcx, pred));
-            ecx.add_goals(where_clause_bounds);
+            ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
 
             // Add GAT where clauses from the trait's definition
             ecx.add_goals(
+                GoalSource::Misc,
                 tcx.predicates_of(goal.predicate.def_id())
                     .instantiate_own(tcx, goal.predicate.alias.args)
                     .map(|(pred, _)| goal.with(tcx, pred)),
@@ -413,7 +415,8 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                         DUMMY_SP,
                         [ty::GenericArg::from(goal.predicate.self_ty())],
                     );
-                    ecx.add_goal(goal.with(tcx, sized_predicate));
+                    // FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
+                    ecx.add_goal(GoalSource::Misc, goal.with(tcx, sized_predicate));
                     tcx.types.unit
                 }
 
@@ -421,7 +424,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                     None => tcx.types.unit,
                     Some(field_def) => {
                         let self_ty = field_def.ty(tcx, args);
-                        ecx.add_goal(goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)));
+                        // FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
+                        ecx.add_goal(
+                            GoalSource::Misc,
+                            goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)),
+                        );
                         return ecx
                             .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
                     }
@@ -431,7 +438,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
                 ty::Tuple(elements) => match elements.last() {
                     None => tcx.types.unit,
                     Some(&self_ty) => {
-                        ecx.add_goal(goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)));
+                        // FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
+                        ecx.add_goal(
+                            GoalSource::Misc,
+                            goal.with(tcx, goal.predicate.with_self_ty(tcx, self_ty)),
+                        );
                         return ecx
                             .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
                     }
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/weak_types.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/weak_types.rs
index 8d2bbec6d8b..6d5728797d1 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/weak_types.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/weak_types.rs
@@ -3,10 +3,10 @@
 //!
 //! Since a weak alias is not ambiguous, this just computes the `type_of` of
 //! the alias and registers the where-clauses of the type alias.
-use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
+use rustc_middle::traits::solve::{Certainty, Goal, GoalSource, QueryResult};
 use rustc_middle::ty;
 
-use super::EvalCtxt;
+use crate::solve::EvalCtxt;
 
 impl<'tcx> EvalCtxt<'_, 'tcx> {
     pub(super) fn normalize_weak_type(
@@ -22,6 +22,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
         // Check where clauses
         self.add_goals(
+            GoalSource::Misc,
             tcx.predicates_of(weak_ty.def_id)
                 .instantiate(tcx, weak_ty.args)
                 .predicates
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index d0e92a54ceb..30ae385a8a0 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -1,3 +1,5 @@
+use crate::solve::GoalSource;
+
 use super::EvalCtxt;
 use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
 use rustc_middle::ty::{self, ProjectionPredicate};
@@ -22,14 +24,15 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             )
             .into(),
         };
-        self.add_goal(goal.with(
+        let goal = goal.with(
             tcx,
             ty::PredicateKind::AliasRelate(
                 projection_term,
                 goal.predicate.term,
                 ty::AliasRelationDirection::Equate,
             ),
-        ));
+        );
+        self.add_goal(GoalSource::Misc, goal);
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 }
diff --git a/compiler/rustc_trait_selection/src/solve/search_graph.rs b/compiler/rustc_trait_selection/src/solve/search_graph.rs
index 2a08b80e02a..2a161c2d956 100644
--- a/compiler/rustc_trait_selection/src/solve/search_graph.rs
+++ b/compiler/rustc_trait_selection/src/solve/search_graph.rs
@@ -8,6 +8,7 @@ use rustc_index::IndexVec;
 use rustc_middle::dep_graph::dep_kinds;
 use rustc_middle::traits::solve::CacheData;
 use rustc_middle::traits::solve::{CanonicalInput, Certainty, EvaluationCache, QueryResult};
+use rustc_middle::ty;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Limit;
 use std::collections::hash_map::Entry;
@@ -111,6 +112,15 @@ impl<'tcx> SearchGraph<'tcx> {
         self.stack.is_empty()
     }
 
+    pub(super) fn current_goal_is_normalizes_to(&self) -> bool {
+        self.stack.raw.last().map_or(false, |e| {
+            matches!(
+                e.input.value.goal.predicate.kind().skip_binder(),
+                ty::PredicateKind::NormalizesTo(..)
+            )
+        })
+    }
+
     /// Returns the remaining depth allowed for nested goals.
     ///
     /// This is generally simply one less than the current depth.
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index deb50e6aefd..ac3ffd2d6c2 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -1,7 +1,7 @@
 //! Dealing with trait goals, i.e. `T: Trait<'a, U>`.
 
 use super::assembly::{self, structural_traits, Candidate};
-use super::{EvalCtxt, SolverMode};
+use super::{EvalCtxt, GoalSource, SolverMode};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{LangItem, Movability};
 use rustc_infer::traits::query::NoSolution;
@@ -72,7 +72,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                 .predicates
                 .into_iter()
                 .map(|pred| goal.with(tcx, pred));
-            ecx.add_goals(where_clause_bounds);
+            ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
 
             ecx.evaluate_added_goals_and_make_canonical_response(maximal_certainty)
         })
@@ -172,7 +172,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             let nested_obligations = tcx
                 .predicates_of(goal.predicate.def_id())
                 .instantiate(tcx, goal.predicate.trait_ref.args);
-            ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)));
+            // FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
+            ecx.add_goals(
+                GoalSource::Misc,
+                nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)),
+            );
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
     }
@@ -512,17 +516,23 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
             // Check that the type implements all of the predicates of the trait object.
             // (i.e. the principal, all of the associated types match, and any auto traits)
-            ecx.add_goals(b_data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))));
+            ecx.add_goals(
+                GoalSource::ImplWhereBound,
+                b_data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
+            );
 
             // The type must be `Sized` to be unsized.
             if let Some(sized_def_id) = tcx.lang_items().sized_trait() {
-                ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])));
+                ecx.add_goal(
+                    GoalSource::ImplWhereBound,
+                    goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])),
+                );
             } else {
                 return Err(NoSolution);
             }
 
             // The type must outlive the lifetime of the `dyn` we're unsizing into.
-            ecx.add_goal(goal.with(tcx, ty::OutlivesPredicate(a_ty, b_region)));
+            ecx.add_goal(GoalSource::Misc, goal.with(tcx, ty::OutlivesPredicate(a_ty, b_region)));
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
     }
@@ -749,11 +759,14 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         }
 
         // Also require that a_ty's lifetime outlives b_ty's lifetime.
-        self.add_goal(Goal::new(
-            self.tcx(),
-            param_env,
-            ty::Binder::dummy(ty::OutlivesPredicate(a_region, b_region)),
-        ));
+        self.add_goal(
+            GoalSource::ImplWhereBound,
+            Goal::new(
+                self.tcx(),
+                param_env,
+                ty::Binder::dummy(ty::OutlivesPredicate(a_region, b_region)),
+            ),
+        );
 
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
@@ -826,14 +839,17 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         // Finally, we require that `TailA: Unsize<TailB>` for the tail field
         // types.
         self.eq(goal.param_env, unsized_a_ty, b_ty)?;
-        self.add_goal(goal.with(
-            tcx,
-            ty::TraitRef::new(
+        self.add_goal(
+            GoalSource::ImplWhereBound,
+            goal.with(
                 tcx,
-                tcx.lang_items().unsize_trait().unwrap(),
-                [a_tail_ty, b_tail_ty],
+                ty::TraitRef::new(
+                    tcx,
+                    tcx.lang_items().unsize_trait().unwrap(),
+                    [a_tail_ty, b_tail_ty],
+                ),
             ),
-        ));
+        );
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 
@@ -865,14 +881,17 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         self.eq(goal.param_env, unsized_a_ty, b_ty)?;
 
         // Similar to ADTs, require that we can unsize the tail.
-        self.add_goal(goal.with(
-            tcx,
-            ty::TraitRef::new(
+        self.add_goal(
+            GoalSource::ImplWhereBound,
+            goal.with(
                 tcx,
-                tcx.lang_items().unsize_trait().unwrap(),
-                [a_last_ty, b_last_ty],
+                ty::TraitRef::new(
+                    tcx,
+                    tcx.lang_items().unsize_trait().unwrap(),
+                    [a_last_ty, b_last_ty],
+                ),
             ),
-        ));
+        );
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 
@@ -981,6 +1000,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     ) -> QueryResult<'tcx> {
         self.probe_misc_candidate("constituent tys").enter(|ecx| {
             ecx.add_goals(
+                GoalSource::ImplWhereBound,
                 constituent_tys(ecx, goal.predicate.self_ty())?
                     .into_iter()
                     .map(|ty| goal.with(ecx.tcx(), goal.predicate.with_self_ty(ecx.tcx(), ty)))
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index d5635812c74..a1b0ada0e8a 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -2327,8 +2327,9 @@ fn confirm_fn_pointer_candidate<'cx, 'tcx>(
     obligation: &ProjectionTyObligation<'tcx>,
     nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
+    let tcx = selcx.tcx();
     let fn_type = selcx.infcx.shallow_resolve(obligation.predicate.self_ty());
-    let sig = fn_type.fn_sig(selcx.tcx());
+    let sig = fn_type.fn_sig(tcx);
     let Normalized { value: sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2337,9 +2338,24 @@ fn confirm_fn_pointer_candidate<'cx, 'tcx>(
         sig,
     );
 
-    confirm_callable_candidate(selcx, obligation, sig, util::TupleArgumentsFlag::Yes)
-        .with_addl_obligations(nested)
-        .with_addl_obligations(obligations)
+    let host_effect_param = match *fn_type.kind() {
+        ty::FnDef(def_id, args) => tcx
+            .generics_of(def_id)
+            .host_effect_index
+            .map_or(tcx.consts.true_, |idx| args.const_at(idx)),
+        ty::FnPtr(_) => tcx.consts.true_,
+        _ => unreachable!("only expected FnPtr or FnDef in `confirm_fn_pointer_candidate`"),
+    };
+
+    confirm_callable_candidate(
+        selcx,
+        obligation,
+        sig,
+        util::TupleArgumentsFlag::Yes,
+        host_effect_param,
+    )
+    .with_addl_obligations(nested)
+    .with_addl_obligations(obligations)
 }
 
 fn confirm_closure_candidate<'cx, 'tcx>(
@@ -2362,9 +2378,16 @@ fn confirm_closure_candidate<'cx, 'tcx>(
 
     debug!(?obligation, ?closure_sig, ?obligations, "confirm_closure_candidate");
 
-    confirm_callable_candidate(selcx, obligation, closure_sig, util::TupleArgumentsFlag::No)
-        .with_addl_obligations(nested)
-        .with_addl_obligations(obligations)
+    confirm_callable_candidate(
+        selcx,
+        obligation,
+        closure_sig,
+        util::TupleArgumentsFlag::No,
+        // FIXME(effects): This doesn't handle const closures correctly!
+        selcx.tcx().consts.true_,
+    )
+    .with_addl_obligations(nested)
+    .with_addl_obligations(obligations)
 }
 
 fn confirm_callable_candidate<'cx, 'tcx>(
@@ -2372,6 +2395,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
     obligation: &ProjectionTyObligation<'tcx>,
     fn_sig: ty::PolyFnSig<'tcx>,
     flag: util::TupleArgumentsFlag,
+    fn_host_effect: ty::Const<'tcx>,
 ) -> Progress<'tcx> {
     let tcx = selcx.tcx();
 
@@ -2386,6 +2410,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
         obligation.predicate.self_ty(),
         fn_sig,
         flag,
+        fn_host_effect,
     )
     .map_bound(|(trait_ref, ret_type)| ty::ProjectionPredicate {
         projection_ty: ty::AliasTy::new(tcx, fn_once_output_def_id, trait_ref.args),
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index cd7fd028a46..73e06b84085 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -355,17 +355,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // Provide an impl, but only for suitable `fn` pointers.
             ty::FnPtr(sig) => {
                 if sig.is_fn_trait_compatible() {
-                    candidates.vec.push(FnPointerCandidate { is_const: false });
+                    candidates
+                        .vec
+                        .push(FnPointerCandidate { fn_host_effect: self.tcx().consts.true_ });
                 }
             }
             // Provide an impl for suitable functions, rejecting `#[target_feature]` functions (RFC 2396).
-            ty::FnDef(def_id, _) => {
-                if self.tcx().fn_sig(def_id).skip_binder().is_fn_trait_compatible()
-                    && self.tcx().codegen_fn_attrs(def_id).target_features.is_empty()
+            ty::FnDef(def_id, args) => {
+                let tcx = self.tcx();
+                if tcx.fn_sig(def_id).skip_binder().is_fn_trait_compatible()
+                    && tcx.codegen_fn_attrs(def_id).target_features.is_empty()
                 {
-                    candidates
-                        .vec
-                        .push(FnPointerCandidate { is_const: self.tcx().is_const_fn(def_id) });
+                    candidates.vec.push(FnPointerCandidate {
+                        fn_host_effect: tcx
+                            .generics_of(def_id)
+                            .host_effect_index
+                            .map_or(tcx.consts.true_, |idx| args.const_at(idx)),
+                    });
                 }
             }
             _ => {}
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index bcaf6aff66b..ce3fc2185ba 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -103,8 +103,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 ImplSource::Builtin(BuiltinImplSource::Misc, vtable_iterator)
             }
 
-            FnPointerCandidate { is_const } => {
-                let data = self.confirm_fn_pointer_candidate(obligation, is_const)?;
+            FnPointerCandidate { fn_host_effect } => {
+                let data = self.confirm_fn_pointer_candidate(obligation, fn_host_effect)?;
                 ImplSource::Builtin(BuiltinImplSource::Misc, data)
             }
 
@@ -653,8 +653,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     fn confirm_fn_pointer_candidate(
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
-        // FIXME(effects)
-        _is_const: bool,
+        fn_host_effect: ty::Const<'tcx>,
     ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
         debug!(?obligation, "confirm_fn_pointer_candidate");
 
@@ -675,6 +674,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             self_ty,
             sig,
             util::TupleArgumentsFlag::Yes,
+            fn_host_effect,
         )
         .map_bound(|(trait_ref, _)| trait_ref);
 
@@ -860,7 +860,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             bug!("closure candidate for non-closure {:?}", obligation);
         };
 
-        let trait_ref = self.closure_trait_ref_unnormalized(obligation, args);
+        let trait_ref =
+            self.closure_trait_ref_unnormalized(obligation, args, self.tcx().consts.true_);
         let nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
 
         debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 9886e33ca3b..23f7bdd1584 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1226,11 +1226,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         if unbound_input_types
             && stack.iter().skip(1).any(|prev| {
                 stack.obligation.param_env == prev.obligation.param_env
-                    && self.match_fresh_trait_refs(
-                        stack.fresh_trait_pred,
-                        prev.fresh_trait_pred,
-                        prev.obligation.param_env,
-                    )
+                    && self.match_fresh_trait_refs(stack.fresh_trait_pred, prev.fresh_trait_pred)
             })
         {
             debug!("evaluate_stack --> unbound argument, recursive --> giving up",);
@@ -1865,7 +1861,9 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             }
 
             // Drop otherwise equivalent non-const fn pointer candidates
-            (FnPointerCandidate { .. }, FnPointerCandidate { is_const: false }) => DropVictim::Yes,
+            (FnPointerCandidate { .. }, FnPointerCandidate { fn_host_effect }) => {
+                DropVictim::drop_if(*fn_host_effect == self.tcx().consts.true_)
+            }
 
             (
                 ParamCandidate(ref other_cand),
@@ -2630,9 +2628,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         &self,
         previous: ty::PolyTraitPredicate<'tcx>,
         current: ty::PolyTraitPredicate<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
     ) -> bool {
-        let mut matcher = MatchAgainstFreshVars::new(self.tcx(), param_env);
+        let mut matcher = MatchAgainstFreshVars::new(self.tcx());
         matcher.relate(previous, current).is_ok()
     }
 
@@ -2660,6 +2657,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
         args: GenericArgsRef<'tcx>,
+        fn_host_effect: ty::Const<'tcx>,
     ) -> ty::PolyTraitRef<'tcx> {
         let closure_sig = args.as_closure().sig();
 
@@ -2680,6 +2678,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             self_ty,
             closure_sig,
             util::TupleArgumentsFlag::No,
+            fn_host_effect,
         )
         .map_bound(|(trait_ref, _)| trait_ref)
     }
diff --git a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
index b9ab26fe2fe..e0f9fdc3827 100644
--- a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
@@ -3,7 +3,7 @@ use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKi
 use rustc_infer::traits::{FulfillmentError, TraitEngine};
 use rustc_middle::ty::{self, Ty};
 
-use crate::traits::{query::evaluate_obligation::InferCtxtExt, NormalizeExt, Obligation};
+use crate::traits::{NormalizeExt, Obligation};
 
 pub trait StructurallyNormalizeExt<'tcx> {
     fn structurally_normalize(
@@ -16,42 +16,43 @@ pub trait StructurallyNormalizeExt<'tcx> {
 impl<'tcx> StructurallyNormalizeExt<'tcx> for At<'_, 'tcx> {
     fn structurally_normalize(
         &self,
-        mut ty: Ty<'tcx>,
+        ty: Ty<'tcx>,
         fulfill_cx: &mut dyn TraitEngine<'tcx>,
     ) -> Result<Ty<'tcx>, Vec<FulfillmentError<'tcx>>> {
         assert!(!ty.is_ty_var(), "should have resolved vars before calling");
 
         if self.infcx.next_trait_solver() {
-            // FIXME(-Znext-solver): correctly handle
-            // overflow here.
-            for _ in 0..256 {
-                let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, alias) = *ty.kind() else {
-                    break;
-                };
-
-                let new_infer_ty = self.infcx.next_ty_var(TypeVariableOrigin {
-                    kind: TypeVariableOriginKind::NormalizeProjectionType,
-                    span: self.cause.span,
-                });
-                let obligation = Obligation::new(
-                    self.infcx.tcx,
-                    self.cause.clone(),
-                    self.param_env,
-                    ty::NormalizesTo { alias, term: new_infer_ty.into() },
-                );
-                if self.infcx.predicate_may_hold(&obligation) {
-                    fulfill_cx.register_predicate_obligation(self.infcx, obligation);
-                    let errors = fulfill_cx.select_where_possible(self.infcx);
-                    if !errors.is_empty() {
-                        return Err(errors);
-                    }
-                    ty = self.infcx.resolve_vars_if_possible(new_infer_ty);
-                } else {
-                    break;
-                }
+            // FIXME(-Znext-solver): Should we resolve opaques here?
+            let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _) = *ty.kind() else {
+                return Ok(ty);
+            };
+
+            let new_infer_ty = self.infcx.next_ty_var(TypeVariableOrigin {
+                kind: TypeVariableOriginKind::NormalizeProjectionType,
+                span: self.cause.span,
+            });
+
+            // We simply emit an `alias-eq` goal here, since that will take care of
+            // normalizing the LHS of the projection until it is a rigid projection
+            // (or a not-yet-defined opaque in scope).
+            let obligation = Obligation::new(
+                self.infcx.tcx,
+                self.cause.clone(),
+                self.param_env,
+                ty::PredicateKind::AliasRelate(
+                    ty.into(),
+                    new_infer_ty.into(),
+                    ty::AliasRelationDirection::Equate,
+                ),
+            );
+
+            fulfill_cx.register_predicate_obligation(self.infcx, obligation);
+            let errors = fulfill_cx.select_where_possible(self.infcx);
+            if !errors.is_empty() {
+                return Err(errors);
             }
 
-            Ok(ty)
+            Ok(self.infcx.resolve_vars_if_possible(new_infer_ty))
         } else {
             Ok(self.normalize(ty).into_value_registering_obligations(self.infcx, fulfill_cx))
         }
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 575010ff46d..19eae93df9c 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -264,13 +264,26 @@ pub fn closure_trait_ref_and_return_type<'tcx>(
     self_ty: Ty<'tcx>,
     sig: ty::PolyFnSig<'tcx>,
     tuple_arguments: TupleArgumentsFlag,
+    fn_host_effect: ty::Const<'tcx>,
 ) -> ty::Binder<'tcx, (ty::TraitRef<'tcx>, Ty<'tcx>)> {
     assert!(!self_ty.has_escaping_bound_vars());
     let arguments_tuple = match tuple_arguments {
         TupleArgumentsFlag::No => sig.skip_binder().inputs()[0],
         TupleArgumentsFlag::Yes => Ty::new_tup(tcx, sig.skip_binder().inputs()),
     };
-    let trait_ref = ty::TraitRef::new(tcx, fn_trait_def_id, [self_ty, arguments_tuple]);
+    let trait_ref = if tcx.generics_of(fn_trait_def_id).host_effect_index.is_some() {
+        ty::TraitRef::new(
+            tcx,
+            fn_trait_def_id,
+            [
+                ty::GenericArg::from(self_ty),
+                ty::GenericArg::from(arguments_tuple),
+                ty::GenericArg::from(fn_host_effect),
+            ],
+        )
+    } else {
+        ty::TraitRef::new(tcx, fn_trait_def_id, [self_ty, arguments_tuple])
+    };
     sig.map_bound(|sig| (trait_ref, sig.output()))
 }
 
diff --git a/compiler/stable_mir/src/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
index 5023af9ab79..b8fd9370aa6 100644
--- a/compiler/stable_mir/src/mir/body.rs
+++ b/compiler/stable_mir/src/mir/body.rs
@@ -27,6 +27,9 @@ pub struct Body {
     ///
     /// This is used for the "rust-call" ABI such as closures.
     pub(super) spread_arg: Option<Local>,
+
+    /// The span that covers the entire function body.
+    pub span: Span,
 }
 
 pub type BasicBlockIdx = usize;
@@ -42,6 +45,7 @@ impl Body {
         arg_count: usize,
         var_debug_info: Vec<VarDebugInfo>,
         spread_arg: Option<Local>,
+        span: Span,
     ) -> Self {
         // If locals doesn't contain enough entries, it can lead to panics in
         // `ret_local`, `arg_locals`, and `inner_locals`.
@@ -49,7 +53,7 @@ impl Body {
             locals.len() > arg_count,
             "A Body must contain at least a local for the return value and each of the function's arguments"
         );
-        Self { blocks, locals, arg_count, var_debug_info, spread_arg }
+        Self { blocks, locals, arg_count, var_debug_info, spread_arg, span }
     }
 
     /// Return local that holds this function's return value.
diff --git a/compiler/stable_mir/src/mir/visit.rs b/compiler/stable_mir/src/mir/visit.rs
index 98336a72900..ab57ff0f8f5 100644
--- a/compiler/stable_mir/src/mir/visit.rs
+++ b/compiler/stable_mir/src/mir/visit.rs
@@ -133,7 +133,7 @@ pub trait MirVisitor {
     }
 
     fn super_body(&mut self, body: &Body) {
-        let Body { blocks, locals: _, arg_count, var_debug_info, spread_arg: _ } = body;
+        let Body { blocks, locals: _, arg_count, var_debug_info, spread_arg: _, span } = body;
 
         for bb in blocks {
             self.visit_basic_block(bb);
@@ -153,6 +153,8 @@ pub trait MirVisitor {
         for info in var_debug_info.iter() {
             self.visit_var_debug_info(info);
         }
+
+        self.visit_span(span)
     }
 
     fn super_basic_block(&mut self, bb: &BasicBlock) {