Merging upstream version 1.70.0+dfsg1.

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

37 files changed, 466 insertions, 567 deletions

diff --git a/compiler/rustc_borrowck/locales/en-US.ftl b/compiler/rustc_borrowck/messages.ftl
index a3b6b5e81..a3b6b5e81 100644
--- a/compiler/rustc_borrowck/locales/en-US.ftl
+++ b/compiler/rustc_borrowck/messages.ftl
diff --git a/compiler/rustc_borrowck/src/borrow_set.rs b/compiler/rustc_borrowck/src/borrow_set.rs
index 5bb92a358..4824f6346 100644
--- a/compiler/rustc_borrowck/src/borrow_set.rs
+++ b/compiler/rustc_borrowck/src/borrow_set.rs
@@ -1,10 +1,9 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use crate::nll::ToRegionVid;
 use crate::path_utils::allow_two_phase_borrow;
 use crate::place_ext::PlaceExt;
 use crate::BorrowIndex;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::traversal;
 use rustc_middle::mir::visit::{MutatingUseContext, NonUseContext, PlaceContext, Visitor};
@@ -26,10 +25,10 @@ pub struct BorrowSet<'tcx> {
     /// NOTE: a given location may activate more than one borrow in the future
     /// when more general two-phase borrow support is introduced, but for now we
     /// only need to store one borrow index.
-    pub activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
+    pub activation_map: FxIndexMap<Location, Vec<BorrowIndex>>,
 
     /// Map from local to all the borrows on that local.
-    pub local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
+    pub local_map: FxIndexMap<mir::Local, FxIndexSet<BorrowIndex>>,
 
     pub(crate) locals_state_at_exit: LocalsStateAtExit,
 }
@@ -175,8 +174,8 @@ struct GatherBorrows<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'a Body<'tcx>,
     location_map: FxIndexMap<Location, BorrowData<'tcx>>,
-    activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
-    local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
+    activation_map: FxIndexMap<Location, Vec<BorrowIndex>>,
+    local_map: FxIndexMap<mir::Local, FxIndexSet<BorrowIndex>>,
 
     /// When we encounter a 2-phase borrow statement, it will always
     /// be assigning into a temporary TEMP:
@@ -186,7 +185,7 @@ struct GatherBorrows<'a, 'tcx> {
     /// We add TEMP into this map with `b`, where `b` is the index of
     /// the borrow. When we find a later use of this activation, we
     /// remove from the map (and add to the "tombstone" set below).
-    pending_activations: FxHashMap<mir::Local, BorrowIndex>,
+    pending_activations: FxIndexMap<mir::Local, BorrowIndex>,
 
     locals_state_at_exit: LocalsStateAtExit,
 }
@@ -204,7 +203,7 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'tcx> {
                 return;
             }
 
-            let region = region.to_region_vid();
+            let region = region.as_var();
 
             let borrow = BorrowData {
                 kind,
@@ -279,7 +278,7 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'tcx> {
             let borrow_data = &self.location_map[&location];
             assert_eq!(borrow_data.reserve_location, location);
             assert_eq!(borrow_data.kind, kind);
-            assert_eq!(borrow_data.region, region.to_region_vid());
+            assert_eq!(borrow_data.region, region.as_var());
             assert_eq!(borrow_data.borrowed_place, place);
         }
 
diff --git a/compiler/rustc_borrowck/src/constraint_generation.rs b/compiler/rustc_borrowck/src/constraint_generation.rs
index 1427f5cb3..2aa09a3f2 100644
--- a/compiler/rustc_borrowck/src/constraint_generation.rs
+++ b/compiler/rustc_borrowck/src/constraint_generation.rs
@@ -12,8 +12,8 @@ use rustc_middle::ty::visit::TypeVisitable;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt};
 
 use crate::{
-    borrow_set::BorrowSet, facts::AllFacts, location::LocationTable, nll::ToRegionVid,
-    places_conflict, region_infer::values::LivenessValues,
+    borrow_set::BorrowSet, facts::AllFacts, location::LocationTable, places_conflict,
+    region_infer::values::LivenessValues,
 };
 
 pub(super) fn generate_constraints<'tcx>(
@@ -170,7 +170,7 @@ impl<'cx, 'tcx> ConstraintGeneration<'cx, 'tcx> {
         debug!("add_regular_live_constraint(live_ty={:?}, location={:?})", live_ty, location);
 
         self.infcx.tcx.for_each_free_region(&live_ty, |live_region| {
-            let vid = live_region.to_region_vid();
+            let vid = live_region.as_var();
             self.liveness_constraints.add_element(vid, location);
         });
     }
diff --git a/compiler/rustc_borrowck/src/constraints/graph.rs b/compiler/rustc_borrowck/src/constraints/graph.rs
index c780d0479..f5a34cb05 100644
--- a/compiler/rustc_borrowck/src/constraints/graph.rs
+++ b/compiler/rustc_borrowck/src/constraints/graph.rs
@@ -13,7 +13,7 @@ use crate::{
 /// The construct graph organizes the constraints by their end-points.
 /// It can be used to view a `R1: R2` constraint as either an edge `R1
 /// -> R2` or `R2 -> R1` depending on the direction type `D`.
-pub(crate) struct ConstraintGraph<D: ConstraintGraphDirecton> {
+pub(crate) struct ConstraintGraph<D: ConstraintGraphDirection> {
     _direction: D,
     first_constraints: IndexVec<RegionVid, Option<OutlivesConstraintIndex>>,
     next_constraints: IndexVec<OutlivesConstraintIndex, Option<OutlivesConstraintIndex>>,
@@ -25,7 +25,7 @@ pub(crate) type ReverseConstraintGraph = ConstraintGraph<Reverse>;
 
 /// Marker trait that controls whether a `R1: R2` constraint
 /// represents an edge `R1 -> R2` or `R2 -> R1`.
-pub(crate) trait ConstraintGraphDirecton: Copy + 'static {
+pub(crate) trait ConstraintGraphDirection: Copy + 'static {
     fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid;
     fn end_region(c: &OutlivesConstraint<'_>) -> RegionVid;
     fn is_normal() -> bool;
@@ -38,7 +38,7 @@ pub(crate) trait ConstraintGraphDirecton: Copy + 'static {
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct Normal;
 
-impl ConstraintGraphDirecton for Normal {
+impl ConstraintGraphDirection for Normal {
     fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid {
         c.sup
     }
@@ -59,7 +59,7 @@ impl ConstraintGraphDirecton for Normal {
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct Reverse;
 
-impl ConstraintGraphDirecton for Reverse {
+impl ConstraintGraphDirection for Reverse {
     fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid {
         c.sub
     }
@@ -73,7 +73,7 @@ impl ConstraintGraphDirecton for Reverse {
     }
 }
 
-impl<D: ConstraintGraphDirecton> ConstraintGraph<D> {
+impl<D: ConstraintGraphDirection> ConstraintGraph<D> {
     /// Creates a "dependency graph" where each region constraint `R1:
     /// R2` is treated as an edge `R1 -> R2`. We use this graph to
     /// construct SCCs for region inference but also for error
@@ -133,7 +133,7 @@ impl<D: ConstraintGraphDirecton> ConstraintGraph<D> {
     }
 }
 
-pub(crate) struct Edges<'s, 'tcx, D: ConstraintGraphDirecton> {
+pub(crate) struct Edges<'s, 'tcx, D: ConstraintGraphDirection> {
     graph: &'s ConstraintGraph<D>,
     constraints: &'s OutlivesConstraintSet<'tcx>,
     pointer: Option<OutlivesConstraintIndex>,
@@ -141,7 +141,7 @@ pub(crate) struct Edges<'s, 'tcx, D: ConstraintGraphDirecton> {
     static_region: RegionVid,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> Iterator for Edges<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> Iterator for Edges<'s, 'tcx, D> {
     type Item = OutlivesConstraint<'tcx>;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -174,13 +174,13 @@ impl<'s, 'tcx, D: ConstraintGraphDirecton> Iterator for Edges<'s, 'tcx, D> {
 /// This struct brings together a constraint set and a (normal, not
 /// reverse) constraint graph. It implements the graph traits and is
 /// usd for doing the SCC computation.
-pub(crate) struct RegionGraph<'s, 'tcx, D: ConstraintGraphDirecton> {
+pub(crate) struct RegionGraph<'s, 'tcx, D: ConstraintGraphDirection> {
     set: &'s OutlivesConstraintSet<'tcx>,
     constraint_graph: &'s ConstraintGraph<D>,
     static_region: RegionVid,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> RegionGraph<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> RegionGraph<'s, 'tcx, D> {
     /// Creates a "dependency graph" where each region constraint `R1:
     /// R2` is treated as an edge `R1 -> R2`. We use this graph to
     /// construct SCCs for region inference but also for error
@@ -202,11 +202,11 @@ impl<'s, 'tcx, D: ConstraintGraphDirecton> RegionGraph<'s, 'tcx, D> {
     }
 }
 
-pub(crate) struct Successors<'s, 'tcx, D: ConstraintGraphDirecton> {
+pub(crate) struct Successors<'s, 'tcx, D: ConstraintGraphDirection> {
     edges: Edges<'s, 'tcx, D>,
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> Iterator for Successors<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> Iterator for Successors<'s, 'tcx, D> {
     type Item = RegionVid;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -214,23 +214,25 @@ impl<'s, 'tcx, D: ConstraintGraphDirecton> Iterator for Successors<'s, 'tcx, D>
     }
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> graph::DirectedGraph for RegionGraph<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> graph::DirectedGraph for RegionGraph<'s, 'tcx, D> {
     type Node = RegionVid;
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> graph::WithNumNodes for RegionGraph<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> graph::WithNumNodes for RegionGraph<'s, 'tcx, D> {
     fn num_nodes(&self) -> usize {
         self.constraint_graph.first_constraints.len()
     }
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> graph::WithSuccessors for RegionGraph<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> graph::WithSuccessors for RegionGraph<'s, 'tcx, D> {
     fn successors(&self, node: Self::Node) -> <Self as graph::GraphSuccessors<'_>>::Iter {
         self.outgoing_regions(node)
     }
 }
 
-impl<'s, 'tcx, D: ConstraintGraphDirecton> graph::GraphSuccessors<'_> for RegionGraph<'s, 'tcx, D> {
+impl<'s, 'tcx, D: ConstraintGraphDirection> graph::GraphSuccessors<'_>
+    for RegionGraph<'s, 'tcx, D>
+{
     type Item = RegionVid;
     type Iter = Successors<'s, 'tcx, D>;
 }
diff --git a/compiler/rustc_borrowck/src/constraints/mod.rs b/compiler/rustc_borrowck/src/constraints/mod.rs
index f370c0216..d2d9779db 100644
--- a/compiler/rustc_borrowck/src/constraints/mod.rs
+++ b/compiler/rustc_borrowck/src/constraints/mod.rs
@@ -2,7 +2,7 @@
 #![deny(rustc::diagnostic_outside_of_impl)]
 
 use rustc_data_structures::graph::scc::Sccs;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::{RegionVid, VarianceDiagInfo};
 use rustc_span::Span;
@@ -60,7 +60,9 @@ impl<'tcx> OutlivesConstraintSet<'tcx> {
         Sccs::new(region_graph)
     }
 
-    pub(crate) fn outlives(&self) -> &IndexVec<OutlivesConstraintIndex, OutlivesConstraint<'tcx>> {
+    pub(crate) fn outlives(
+        &self,
+    ) -> &IndexSlice<OutlivesConstraintIndex, OutlivesConstraint<'tcx>> {
         &self.outlives
     }
 }
diff --git a/compiler/rustc_borrowck/src/consumers.rs b/compiler/rustc_borrowck/src/consumers.rs
index 055b281bc..cb1a65222 100644
--- a/compiler/rustc_borrowck/src/consumers.rs
+++ b/compiler/rustc_borrowck/src/consumers.rs
@@ -3,7 +3,7 @@
 //! This file provides API for compiler consumers.
 
 use rustc_hir::def_id::LocalDefId;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::IndexSlice;
 use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
 use rustc_middle::mir::Body;
 use rustc_middle::ty::{self, TyCtxt};
@@ -35,6 +35,6 @@ pub fn get_body_with_borrowck_facts(
     let (input_body, promoted) = tcx.mir_promoted(def);
     let infcx = tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bind(def.did)).build();
     let input_body: &Body<'_> = &input_body.borrow();
-    let promoted: &IndexVec<_, _> = &promoted.borrow();
+    let promoted: &IndexSlice<_, _> = &promoted.borrow();
     *super::do_mir_borrowck(&infcx, input_body, promoted, true).1.unwrap()
 }
diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index 2821677c5..94939c7e4 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -1,6 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::{self, BasicBlock, Body, Location, Place};
 use rustc_middle::ty::RegionVid;
@@ -11,9 +11,7 @@ use rustc_mir_dataflow::{self, fmt::DebugWithContext, CallReturnPlaces, GenKill}
 use rustc_mir_dataflow::{Analysis, Direction, Results};
 use std::fmt;
 
-use crate::{
-    places_conflict, BorrowSet, PlaceConflictBias, PlaceExt, RegionInferenceContext, ToRegionVid,
-};
+use crate::{places_conflict, BorrowSet, PlaceConflictBias, PlaceExt, RegionInferenceContext};
 
 /// A tuple with named fields that can hold either the results or the transient state of the
 /// dataflow analyses used by the borrow checker.
@@ -124,7 +122,7 @@ pub struct Borrows<'a, 'tcx> {
     body: &'a Body<'tcx>,
 
     borrow_set: &'a BorrowSet<'tcx>,
-    borrows_out_of_scope_at_location: FxHashMap<Location, Vec<BorrowIndex>>,
+    borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
 struct StackEntry {
@@ -138,7 +136,7 @@ struct OutOfScopePrecomputer<'a, 'tcx> {
     visit_stack: Vec<StackEntry>,
     body: &'a Body<'tcx>,
     regioncx: &'a RegionInferenceContext<'tcx>,
-    borrows_out_of_scope_at_location: FxHashMap<Location, Vec<BorrowIndex>>,
+    borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
 impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
@@ -148,7 +146,7 @@ impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
             visit_stack: vec![],
             body,
             regioncx,
-            borrows_out_of_scope_at_location: FxHashMap::default(),
+            borrows_out_of_scope_at_location: FxIndexMap::default(),
         }
     }
 }
@@ -242,7 +240,7 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
     ) -> Self {
         let mut prec = OutOfScopePrecomputer::new(body, nonlexical_regioncx);
         for (borrow_index, borrow_data) in borrow_set.iter_enumerated() {
-            let borrow_region = borrow_data.region.to_region_vid();
+            let borrow_region = borrow_data.region;
             let location = borrow_data.reserve_location;
 
             prec.precompute_borrows_out_of_scope(borrow_index, borrow_region, location);
@@ -306,7 +304,7 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
         }
 
         // By passing `PlaceConflictBias::NoOverlap`, we conservatively assume that any given
-        // pair of array indices are unequal, so that when `places_conflict` returns true, we
+        // pair of array indices are not equal, so that when `places_conflict` returns true, we
         // will be assured that two places being compared definitely denotes the same sets of
         // locations.
         let definitely_conflicting_borrows = other_borrows_of_local.filter(|&i| {
@@ -390,6 +388,7 @@ impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
             | mir::StatementKind::Deinit(..)
             | mir::StatementKind::StorageLive(..)
             | mir::StatementKind::Retag { .. }
+            | mir::StatementKind::PlaceMention(..)
             | mir::StatementKind::AscribeUserType(..)
             | mir::StatementKind::Coverage(..)
             | mir::StatementKind::Intrinsic(..)
diff --git a/compiler/rustc_borrowck/src/def_use.rs b/compiler/rustc_borrowck/src/def_use.rs
index 8e62a0198..6deb4e361 100644
--- a/compiler/rustc_borrowck/src/def_use.rs
+++ b/compiler/rustc_borrowck/src/def_use.rs
@@ -50,7 +50,6 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
         PlaceContext::MutatingUse(MutatingUseContext::Borrow) |
         PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow) |
         PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow) |
-        PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow) |
 
         PlaceContext::MutatingUse(MutatingUseContext::AddressOf) |
         PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |
@@ -72,6 +71,8 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
         PlaceContext::MutatingUse(MutatingUseContext::Drop) =>
             Some(DefUse::Drop),
 
+        // This statement exists to help unsafeck. It does not require the place to be live.
+        PlaceContext::NonUse(NonUseContext::PlaceMention) => None,
         // Debug info is neither def nor use.
         PlaceContext::NonUse(NonUseContext::VarDebugInfo) => None,
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index 68205fa45..84f75caa6 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -181,8 +181,8 @@ trait TypeOpInfo<'tcx> {
         };
 
         let placeholder_region = tcx.mk_re_placeholder(ty::Placeholder {
-            name: placeholder.name,
             universe: adjusted_universe.into(),
+            bound: placeholder.bound,
         });
 
         let error_region =
@@ -191,8 +191,8 @@ trait TypeOpInfo<'tcx> {
                     error_placeholder.universe.as_u32().checked_sub(base_universe.as_u32());
                 adjusted_universe.map(|adjusted| {
                     tcx.mk_re_placeholder(ty::Placeholder {
-                        name: error_placeholder.name,
                         universe: adjusted.into(),
+                        bound: error_placeholder.bound,
                     })
                 })
             } else {
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index cb97699d7..75a3dd0c0 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -1,7 +1,7 @@
 use either::Either;
 use rustc_const_eval::util::CallKind;
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{
     struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
 };
@@ -24,6 +24,7 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::{kw, sym};
 use rustc_span::{BytePos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::ObligationCtxt;
 
 use crate::borrow_set::TwoPhaseActivation;
 use crate::borrowck_errors;
@@ -173,7 +174,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
             let mut is_loop_move = false;
             let mut in_pattern = false;
-            let mut seen_spans = FxHashSet::default();
+            let mut seen_spans = FxIndexSet::default();
 
             for move_site in &move_site_vec {
                 let move_out = self.move_data.moves[(*move_site).moi];
@@ -760,20 +761,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         else { return; };
         // Try to find predicates on *generic params* that would allow copying `ty`
         let infcx = tcx.infer_ctxt().build();
-        let copy_did = infcx.tcx.require_lang_item(LangItem::Copy, Some(span));
-        let cause = ObligationCause::new(
-            span,
-            self.mir_def_id(),
-            rustc_infer::traits::ObligationCauseCode::MiscObligation,
-        );
-        let errors = rustc_trait_selection::traits::fully_solve_bound(
-            &infcx,
-            cause,
-            self.param_env,
-            // Erase any region vids from the type, which may not be resolved
-            infcx.tcx.erase_regions(ty),
-            copy_did,
-        );
+        let ocx = ObligationCtxt::new(&infcx);
+        let copy_did = tcx.require_lang_item(LangItem::Copy, Some(span));
+        let cause = ObligationCause::misc(span, self.mir_def_id());
+
+        ocx.register_bound(cause, self.param_env, infcx.tcx.erase_regions(ty), copy_did);
+        let errors = ocx.select_all_or_error();
 
         // Only emit suggestion if all required predicates are on generic
         let predicates: Result<Vec<_>, _> = errors
@@ -1467,6 +1460,32 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     /// Reports StorageDeadOrDrop of `place` conflicts with `borrow`.
     ///
+    /// Depending on the origin of the StorageDeadOrDrop, this may be
+    /// reported as either a drop or an illegal mutation of a borrowed value.
+    /// The latter is preferred when the this is a drop triggered by a
+    /// reassignment, as it's more user friendly to report a problem with the
+    /// explicit assignment than the implicit drop.
+    #[instrument(level = "debug", skip(self))]
+    pub(crate) fn report_storage_dead_or_drop_of_borrowed(
+        &mut self,
+        location: Location,
+        place_span: (Place<'tcx>, Span),
+        borrow: &BorrowData<'tcx>,
+    ) {
+        // It's sufficient to check the last desugaring as Replace is the last
+        // one to be applied.
+        if let Some(DesugaringKind::Replace) = place_span.1.desugaring_kind() {
+            self.report_illegal_mutation_of_borrowed(location, place_span, borrow)
+        } else {
+            self.report_borrowed_value_does_not_live_long_enough(
+                location,
+                borrow,
+                place_span,
+                Some(WriteKind::StorageDeadOrDrop),
+            )
+        }
+    }
+
     /// This means that some data referenced by `borrow` needs to live
     /// past the point where the StorageDeadOrDrop of `place` occurs.
     /// This is usually interpreted as meaning that `place` has too
@@ -1959,16 +1978,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let (place_desc, note) = if let Some(place_desc) = opt_place_desc {
             let local_kind = if let Some(local) = borrow.borrowed_place.as_local() {
                 match self.body.local_kind(local) {
-                    LocalKind::ReturnPointer | LocalKind::Temp => {
-                        bug!("temporary or return pointer with a name")
+                    LocalKind::Temp if self.body.local_decls[local].is_user_variable() => {
+                        "local variable "
                     }
-                    LocalKind::Var => "local variable ",
                     LocalKind::Arg
                         if !self.upvars.is_empty() && local == ty::CAPTURE_STRUCT_LOCAL =>
                     {
                         "variable captured by `move` "
                     }
                     LocalKind::Arg => "function parameter ",
+                    LocalKind::ReturnPointer | LocalKind::Temp => {
+                        bug!("temporary or return pointer with a name")
+                    }
                 }
             } else {
                 "local data "
@@ -1982,16 +2003,16 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 self.prefixes(borrow.borrowed_place.as_ref(), PrefixSet::All).last().unwrap();
             let local = root_place.local;
             match self.body.local_kind(local) {
-                LocalKind::ReturnPointer | LocalKind::Temp => {
-                    ("temporary value".to_string(), "temporary value created here".to_string())
-                }
                 LocalKind::Arg => (
                     "function parameter".to_string(),
                     "function parameter borrowed here".to_string(),
                 ),
-                LocalKind::Var => {
+                LocalKind::Temp if self.body.local_decls[local].is_user_variable() => {
                     ("local binding".to_string(), "local binding introduced here".to_string())
                 }
+                LocalKind::ReturnPointer | LocalKind::Temp => {
+                    ("temporary value".to_string(), "temporary value created here".to_string())
+                }
             }
         };
 
@@ -2197,8 +2218,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
         }
 
-        let mut visited = FxHashSet::default();
-        let mut move_locations = FxHashSet::default();
+        let mut visited = FxIndexSet::default();
+        let mut move_locations = FxIndexSet::default();
         let mut reinits = vec![];
         let mut result = vec![];
 
@@ -2325,7 +2346,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let reinits_reachable = reinits
             .into_iter()
             .filter(|reinit| {
-                let mut visited = FxHashSet::default();
+                let mut visited = FxIndexSet::default();
                 let mut stack = vec![*reinit];
                 while let Some(location) = stack.pop() {
                     if !visited.insert(location) {
@@ -2456,15 +2477,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let (place_description, assigned_span) = match local_decl {
             Some(LocalDecl {
                 local_info:
-                    Some(box LocalInfo::User(
-                        ClearCrossCrate::Clear
-                        | ClearCrossCrate::Set(BindingForm::Var(VarBindingForm {
+                    ClearCrossCrate::Set(
+                        box LocalInfo::User(BindingForm::Var(VarBindingForm {
                             opt_match_place: None,
                             ..
-                        })),
-                    ))
-                    | Some(box LocalInfo::StaticRef { .. })
-                    | None,
+                        }))
+                        | box LocalInfo::StaticRef { .. }
+                        | box LocalInfo::Boring,
+                    ),
                 ..
             })
             | None => (self.describe_any_place(place.as_ref()), assigned_span),
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 19855075c..8860395e7 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -3,11 +3,11 @@
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::IndexSlice;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::{
-    Body, CastKind, ConstraintCategory, FakeReadCause, Local, Location, Operand, Place, Rvalue,
-    Statement, StatementKind, TerminatorKind,
+    Body, CastKind, ConstraintCategory, FakeReadCause, Local, LocalInfo, Location, Operand, Place,
+    Rvalue, Statement, StatementKind, TerminatorKind,
 };
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::{self, RegionVid, TyCtxt};
@@ -60,7 +60,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
-        local_names: &IndexVec<Local, Option<Symbol>>,
+        local_names: &IndexSlice<Local, Option<Symbol>>,
         err: &mut Diagnostic,
         borrow_desc: &str,
         borrow_span: Option<Span>,
@@ -220,7 +220,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
                         );
                         err.span_label(body.source_info(drop_loc).span, message);
 
-                        if let Some(info) = &local_decl.is_block_tail {
+                        if let LocalInfo::BlockTailTemp(info) = local_decl.local_info() {
                             if info.tail_result_is_ignored {
                                 // #85581: If the first mutable borrow's scope contains
                                 // the second borrow, this suggestion isn't helpful.
diff --git a/compiler/rustc_borrowck/src/diagnostics/find_use.rs b/compiler/rustc_borrowck/src/diagnostics/find_use.rs
index 15f42e26c..2495613fe 100644
--- a/compiler/rustc_borrowck/src/diagnostics/find_use.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/find_use.rs
@@ -6,12 +6,11 @@ use std::rc::Rc;
 
 use crate::{
     def_use::{self, DefUse},
-    nll::ToRegionVid,
     region_infer::{Cause, RegionInferenceContext},
 };
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_middle::mir::visit::{MirVisitable, PlaceContext, Visitor};
-use rustc_middle::mir::{Body, Local, Location};
+use rustc_middle::mir::{self, Body, Local, Location};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 
 pub(crate) fn find<'tcx>(
@@ -37,7 +36,7 @@ struct UseFinder<'cx, 'tcx> {
 impl<'cx, 'tcx> UseFinder<'cx, 'tcx> {
     fn find(&mut self) -> Option<Cause> {
         let mut queue = VecDeque::new();
-        let mut visited = FxHashSet::default();
+        let mut visited = FxIndexSet::default();
 
         queue.push_back(self.start_point);
         while let Some(p) = queue.pop_front() {
@@ -70,7 +69,10 @@ impl<'cx, 'tcx> UseFinder<'cx, 'tcx> {
                             block_data
                                 .terminator()
                                 .successors()
-                                .filter(|&bb| Some(&Some(bb)) != block_data.terminator().unwind())
+                                .filter(|&bb| {
+                                    Some(&mir::UnwindAction::Cleanup(bb))
+                                        != block_data.terminator().unwind()
+                                })
                                 .map(|bb| Location { statement_index: 0, block: bb }),
                         );
                     }
@@ -114,7 +116,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for DefUseVisitor<'cx, 'tcx> {
 
         let mut found_it = false;
         self.tcx.for_each_free_region(&local_ty, |r| {
-            if r.to_region_vid() == self.region_vid {
+            if r.as_var() == self.region_vid {
                 found_it = true;
             }
         });
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index a99fd594a..110354a20 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -6,18 +6,19 @@ use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::GeneratorKind;
+use rustc_index::vec::IndexSlice;
 use rustc_infer::infer::{LateBoundRegionConversionTime, TyCtxtInferExt};
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
-    AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
-    Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
+    AggregateKind, Constant, FakeReadCause, Local, LocalInfo, LocalKind, Location, Operand, Place,
+    PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
 };
 use rustc_middle::ty::print::Print;
-use rustc_middle::ty::{self, DefIdTree, Instance, Ty, TyCtxt};
+use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{
     type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause,
@@ -196,10 +197,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         if self.body.local_decls[local].is_ref_for_guard() {
                             continue;
                         }
-                        if let Some(box LocalInfo::StaticRef { def_id, .. }) =
-                            &self.body.local_decls[local].local_info
+                        if let LocalInfo::StaticRef { def_id, .. } =
+                            *self.body.local_decls[local].local_info()
                         {
-                            buf.push_str(self.infcx.tcx.item_name(*def_id).as_str());
+                            buf.push_str(self.infcx.tcx.item_name(def_id).as_str());
                             ok = Ok(());
                             continue;
                         }
@@ -302,7 +303,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn describe_field(
         &self,
         place: PlaceRef<'tcx>,
-        field: Field,
+        field: FieldIdx,
         including_tuple_field: IncludingTupleField,
     ) -> Option<String> {
         let place_ty = match place {
@@ -331,7 +332,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn describe_field_from_ty(
         &self,
         ty: Ty<'_>,
-        field: Field,
+        field: FieldIdx,
         variant_index: Option<VariantIdx>,
         including_tuple_field: IncludingTupleField,
     ) -> Option<String> {
@@ -350,7 +351,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if !including_tuple_field.0 && variant.ctor_kind() == Some(CtorKind::Fn) {
                         return None;
                     }
-                    Some(variant.fields[field.index()].name.to_string())
+                    Some(variant.fields[field].name.to_string())
                 }
                 ty::Tuple(_) => Some(field.index().to_string()),
                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
@@ -466,9 +467,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         if let ty::Ref(region, ..) = ty.kind() {
             match **region {
                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
-                | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
-                    printer.region_highlight_mode.highlighting_bound_region(br, counter)
-                }
+                | ty::RePlaceholder(ty::PlaceholderRegion {
+                    bound: ty::BoundRegion { kind: br, .. },
+                    ..
+                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
         }
@@ -484,9 +486,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let region = if let ty::Ref(region, ..) = ty.kind() {
             match **region {
                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
-                | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
-                    printer.region_highlight_mode.highlighting_bound_region(br, counter)
-                }
+                | ty::RePlaceholder(ty::PlaceholderRegion {
+                    bound: ty::BoundRegion { kind: br, .. },
+                    ..
+                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
             region
@@ -825,7 +828,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     debug!("move_spans: def_id={:?} place={:?}", closure_def_id, place);
                     let places = &[Operand::Move(place)];
                     if let Some((args_span, generator_kind, capture_kind_span, path_span)) =
-                        self.closure_span(closure_def_id, moved_place, places)
+                        self.closure_span(closure_def_id, moved_place, IndexSlice::from_raw(places))
                     {
                         return ClosureUse {
                             generator_kind,
@@ -925,7 +928,20 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             return OtherUse(use_span);
         }
 
-        for stmt in &self.body[location.block].statements[location.statement_index + 1..] {
+        // drop and replace might have moved the assignment to the next block
+        let maybe_additional_statement =
+            if let TerminatorKind::Drop { target: drop_target, .. } =
+                self.body[location.block].terminator().kind
+            {
+                self.body[drop_target].statements.first()
+            } else {
+                None
+            };
+
+        let statements =
+            self.body[location.block].statements[location.statement_index + 1..].iter();
+
+        for stmt in statements.chain(maybe_additional_statement) {
             if let StatementKind::Assign(box (_, Rvalue::Aggregate(kind, places))) = &stmt.kind {
                 let (&def_id, is_generator) = match kind {
                     box AggregateKind::Closure(def_id, _) => (def_id, false),
@@ -962,7 +978,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         def_id: LocalDefId,
         target_place: PlaceRef<'tcx>,
-        places: &[Operand<'tcx>],
+        places: &IndexSlice<FieldIdx, Operand<'tcx>>,
     ) -> Option<(Span, Option<GeneratorKind>, Span, Span)> {
         debug!(
             "closure_span: def_id={:?} target_place={:?} places={:?}",
@@ -1065,7 +1081,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                     self.param_env,
                                     tcx.mk_imm_ref(tcx.lifetimes.re_erased, tcx.erase_regions(ty)),
                                     def_id,
-                                    DUMMY_SP,
                                 )
                             }
                             _ => false,
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index 5e4c7292e..3662bec0c 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -102,14 +102,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         //
                         // opt_match_place is None for let [mut] x = ... statements,
                         // whether or not the right-hand side is a place expression
-                        if let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
-                            VarBindingForm {
-                                opt_match_place: Some((opt_match_place, match_span)),
-                                binding_mode: _,
-                                opt_ty_info: _,
-                                pat_span: _,
-                            },
-                        )))) = local_decl.local_info
+                        if let LocalInfo::User(BindingForm::Var(VarBindingForm {
+                            opt_match_place: Some((opt_match_place, match_span)),
+                            binding_mode: _,
+                            opt_ty_info: _,
+                            pat_span: _,
+                        })) = *local_decl.local_info()
                         {
                             let stmt_source_info = self.body.source_info(location);
                             self.append_binding_error(
@@ -478,9 +476,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         let mut suggestions: Vec<(Span, String, String)> = Vec::new();
         for local in binds_to {
             let bind_to = &self.body.local_decls[*local];
-            if let Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
-                VarBindingForm { pat_span, .. },
-            )))) = bind_to.local_info
+            if let LocalInfo::User(BindingForm::Var(VarBindingForm { pat_span, .. })) =
+                *bind_to.local_info()
             {
                 let Ok(pat_snippet) =
                     self.infcx.tcx.sess.source_map().span_to_snippet(pat_span) else { continue; };
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 328ac880d..9d9040096 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -7,11 +7,12 @@ use rustc_middle::mir::{Mutability, Place, PlaceRef, ProjectionElem};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{
     hir::place::PlaceBase,
-    mir::{self, BindingForm, ClearCrossCrate, Local, LocalDecl, LocalInfo, LocalKind, Location},
+    mir::{self, BindingForm, Local, LocalDecl, LocalInfo, LocalKind, Location},
 };
 use rustc_span::source_map::DesugaringKind;
 use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, BytePos, Span};
+use rustc_target::abi::FieldIdx;
 
 use crate::diagnostics::BorrowedContentSource;
 use crate::MirBorrowckCtxt;
@@ -105,8 +106,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     reason = String::new();
                 } else {
                     item_msg = access_place_desc;
-                    let local_info = &self.body.local_decls[local].local_info;
-                    if let Some(box LocalInfo::StaticRef { def_id, .. }) = *local_info {
+                    let local_info = self.body.local_decls[local].local_info();
+                    if let LocalInfo::StaticRef { def_id, .. } = *local_info {
                         let static_name = &self.infcx.tcx.item_name(def_id);
                         reason = format!(", as `{static_name}` is an immutable static item");
                     } else {
@@ -120,9 +121,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     && !self.upvars.is_empty()
                 {
                     item_msg = access_place_desc;
-                    debug_assert!(
-                        self.body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty.is_region_ptr()
-                    );
+                    debug_assert!(self.body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty.is_ref());
                     debug_assert!(is_closure_or_generator(
                         Place::ty_from(
                             the_place_err.local,
@@ -305,15 +304,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     ..
                 }) = &self.body[location.block].statements.get(location.statement_index)
                 {
-                    match decl.local_info {
-                        Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::Var(
-                            mir::VarBindingForm {
-                                binding_mode: ty::BindingMode::BindByValue(Mutability::Not),
-                                opt_ty_info: Some(sp),
-                                opt_match_place: _,
-                                pat_span: _,
-                            },
-                        )))) => {
+                    match *decl.local_info() {
+                        LocalInfo::User(BindingForm::Var(mir::VarBindingForm {
+                            binding_mode: ty::BindingMode::BindByValue(Mutability::Not),
+                            opt_ty_info: Some(sp),
+                            opt_match_place: _,
+                            pat_span: _,
+                        })) => {
                             if suggest {
                                 err.span_note(sp, "the binding is already a mutable borrow");
                             }
@@ -346,10 +343,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     }
                 } else if decl.mutability.is_not() {
                     if matches!(
-                        decl.local_info,
-                        Some(box LocalInfo::User(ClearCrossCrate::Set(BindingForm::ImplicitSelf(
-                            hir::ImplicitSelfKind::MutRef
-                        ),)))
+                        decl.local_info(),
+                        LocalInfo::User(BindingForm::ImplicitSelf(hir::ImplicitSelfKind::MutRef))
                     ) {
                         err.note(
                             "as `Self` may be unsized, this call attempts to take `&mut &mut self`",
@@ -474,30 +469,23 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             {
                 let local_decl = &self.body.local_decls[local];
 
-                let (pointer_sigil, pointer_desc) = if local_decl.ty.is_region_ptr() {
-                    ("&", "reference")
-                } else {
-                    ("*const", "pointer")
-                };
+                let (pointer_sigil, pointer_desc) =
+                    if local_decl.ty.is_ref() { ("&", "reference") } else { ("*const", "pointer") };
 
                 match self.local_names[local] {
                     Some(name) if !local_decl.from_compiler_desugaring() => {
-                        let label = match local_decl.local_info.as_deref().unwrap() {
-                            LocalInfo::User(ClearCrossCrate::Set(
-                                mir::BindingForm::ImplicitSelf(_),
-                            )) => {
+                        let label = match *local_decl.local_info() {
+                            LocalInfo::User(mir::BindingForm::ImplicitSelf(_)) => {
                                 let (span, suggestion) =
                                     suggest_ampmut_self(self.infcx.tcx, local_decl);
                                 Some((true, span, suggestion))
                             }
 
-                            LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
-                                mir::VarBindingForm {
-                                    binding_mode: ty::BindingMode::BindByValue(_),
-                                    opt_ty_info,
-                                    ..
-                                },
-                            ))) => {
+                            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+                                binding_mode: ty::BindingMode::BindByValue(_),
+                                opt_ty_info,
+                                ..
+                            })) => {
                                 // check if the RHS is from desugaring
                                 let opt_assignment_rhs_span =
                                     self.body.find_assignments(local).first().map(|&location| {
@@ -534,16 +522,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                                 self.infcx.tcx,
                                                 local_decl,
                                                 opt_assignment_rhs_span,
-                                                *opt_ty_info,
+                                                opt_ty_info,
                                             )
                                         } else {
-                                            match local_decl.local_info.as_deref() {
-                                                Some(LocalInfo::User(ClearCrossCrate::Set(
-                                                    mir::BindingForm::Var(mir::VarBindingForm {
-                                                        opt_ty_info: None,
-                                                        ..
-                                                    }),
-                                                ))) => {
+                                            match local_decl.local_info() {
+                                                LocalInfo::User(mir::BindingForm::Var(
+                                                    mir::VarBindingForm {
+                                                        opt_ty_info: None, ..
+                                                    },
+                                                )) => {
                                                     let (span, sugg) = suggest_ampmut_self(
                                                         self.infcx.tcx,
                                                         local_decl,
@@ -555,7 +542,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                                     self.infcx.tcx,
                                                     local_decl,
                                                     opt_assignment_rhs_span,
-                                                    *opt_ty_info,
+                                                    opt_ty_info,
                                                 ),
                                             }
                                         };
@@ -564,21 +551,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                 }
                             }
 
-                            LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
-                                mir::VarBindingForm {
-                                    binding_mode: ty::BindingMode::BindByReference(_),
-                                    ..
-                                },
-                            ))) => {
+                            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+                                binding_mode: ty::BindingMode::BindByReference(_),
+                                ..
+                            })) => {
                                 let pattern_span = local_decl.source_info.span;
                                 suggest_ref_mut(self.infcx.tcx, pattern_span)
                                     .map(|replacement| (true, pattern_span, replacement))
                             }
 
-                            LocalInfo::User(ClearCrossCrate::Clear) => {
-                                bug!("saw cleared local state")
-                            }
-
                             _ => unreachable!(),
                         };
 
@@ -828,7 +809,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             let Some(hir::Node::Item(item)) = node else { return; };
             let hir::ItemKind::Fn(.., body_id) = item.kind else { return; };
             let body = self.infcx.tcx.hir().body(body_id);
-            let mut v = V { assign_span: span, err, ty, suggested: false };
+            let mut assign_span = span;
+            // Drop desugaring is done at MIR build so it's not in the HIR
+            if let Some(DesugaringKind::Replace) = span.desugaring_kind() {
+                assign_span.remove_mark();
+            }
+
+            let mut v = V { assign_span, err, ty, suggested: false };
             v.visit_body(body);
             if !v.suggested {
                 err.help(&format!(
@@ -1145,20 +1132,19 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 pub fn mut_borrow_of_mutable_ref(local_decl: &LocalDecl<'_>, local_name: Option<Symbol>) -> bool {
     debug!("local_info: {:?}, ty.kind(): {:?}", local_decl.local_info, local_decl.ty.kind());
 
-    match local_decl.local_info.as_deref() {
+    match *local_decl.local_info() {
         // Check if mutably borrowing a mutable reference.
-        Some(LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::Var(
-            mir::VarBindingForm {
-                binding_mode: ty::BindingMode::BindByValue(Mutability::Not), ..
-            },
-        )))) => matches!(local_decl.ty.kind(), ty::Ref(_, _, hir::Mutability::Mut)),
-        Some(LocalInfo::User(ClearCrossCrate::Set(mir::BindingForm::ImplicitSelf(kind)))) => {
+        LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+            binding_mode: ty::BindingMode::BindByValue(Mutability::Not),
+            ..
+        })) => matches!(local_decl.ty.kind(), ty::Ref(_, _, hir::Mutability::Mut)),
+        LocalInfo::User(mir::BindingForm::ImplicitSelf(kind)) => {
             // Check if the user variable is a `&mut self` and we can therefore
             // suggest removing the `&mut`.
             //
             // Deliberately fall into this case for all implicit self types,
             // so that we don't fall in to the next case with them.
-            *kind == hir::ImplicitSelfKind::MutRef
+            kind == hir::ImplicitSelfKind::MutRef
         }
         _ if Some(kw::SelfLower) == local_name => {
             // Otherwise, check if the name is the `self` keyword - in which case
@@ -1268,7 +1254,7 @@ fn suggest_ampmut<'tcx>(
     (
         suggestability,
         highlight_span,
-        if local_decl.ty.is_region_ptr() {
+        if local_decl.ty.is_ref() {
             format!("&mut {}", ty_mut.ty)
         } else {
             format!("*mut {}", ty_mut.ty)
@@ -1290,7 +1276,7 @@ fn is_closure_or_generator(ty: Ty<'_>) -> bool {
 fn get_mut_span_in_struct_field<'tcx>(
     tcx: TyCtxt<'tcx>,
     ty: Ty<'tcx>,
-    field: mir::Field,
+    field: FieldIdx,
 ) -> Option<Span> {
     // Expect our local to be a reference to a struct of some kind.
     if let ty::Ref(_, ty, _) = ty.kind()
diff --git a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
index 1eaf0a2f1..d5ece5743 100644
--- a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
@@ -1,7 +1,7 @@
 //! Contains utilities for generating suggestions for borrowck errors related to unsatisfied
 //! outlives constraints.
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::Diagnostic;
 use rustc_middle::ty::RegionVid;
 use smallvec::SmallVec;
@@ -87,7 +87,7 @@ impl OutlivesSuggestionBuilder {
 
         // Keep track of variables that we have already suggested unifying so that we don't print
         // out silly duplicate messages.
-        let mut unified_already = FxHashSet::default();
+        let mut unified_already = FxIndexSet::default();
 
         for (fr, outlived) in &self.constraints_to_add {
             let Some(fr_name) = self.region_vid_to_name(mbcx, *fr) else {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index ffe82b46c..9fcebeb0a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -207,7 +207,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             .regioncx
             .placeholders_contained_in(lower_bound)
             .map(|placeholder| {
-                if let Some(id) = placeholder.name.get_id()
+                if let Some(id) = placeholder.bound.kind.get_id()
                     && let Some(placeholder_id) = id.as_local()
                     && let gat_hir_id = hir.local_def_id_to_hir_id(placeholder_id)
                     && let Some(generics_impl) = hir.get_parent(gat_hir_id).generics()
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index f6881a2e5..f69c4829a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -6,11 +6,11 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::print::RegionHighlightMode;
 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
-use rustc_middle::ty::{self, DefIdTree, RegionVid, Ty};
+use rustc_middle::ty::{self, RegionVid, Ty};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
-use crate::{nll::ToRegionVid, universal_regions::DefiningTy, MirBorrowckCtxt};
+use crate::{universal_regions::DefiningTy, MirBorrowckCtxt};
 
 /// A name for a particular region used in emitting diagnostics. This name could be a generated
 /// name like `'1`, a name used by the user like `'a`, or a name like `'static`.
@@ -497,7 +497,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 //     &
                 //     - let's call the lifetime of this reference `'1`
                 (ty::Ref(region, referent_ty, _), hir::TyKind::Ref(_lifetime, referent_hir_ty)) => {
-                    if region.to_region_vid() == needle_fr {
+                    if region.as_var() == needle_fr {
                         // Just grab the first character, the `&`.
                         let source_map = self.infcx.tcx.sess.source_map();
                         let ampersand_span = source_map.start_point(hir_ty.span);
@@ -598,7 +598,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         for (kind, hir_arg) in iter::zip(substs, args.args) {
             match (kind.unpack(), hir_arg) {
                 (GenericArgKind::Lifetime(r), hir::GenericArg::Lifetime(lt)) => {
-                    if r.to_region_vid() == needle_fr {
+                    if r.as_var() == needle_fr {
                         return Some(lt);
                     }
                 }
@@ -666,7 +666,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         let return_ty = self.regioncx.universal_regions().unnormalized_output_ty;
         debug!("give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", return_ty);
-        if !tcx.any_free_region_meets(&return_ty, |r| r.to_region_vid() == fr) {
+        if !tcx.any_free_region_meets(&return_ty, |r| r.as_var() == fr) {
             return None;
         }
 
@@ -803,7 +803,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         let tcx = self.infcx.tcx;
 
-        if !tcx.any_free_region_meets(&yield_ty, |r| r.to_region_vid() == fr) {
+        if !tcx.any_free_region_meets(&yield_ty, |r| r.as_var() == fr) {
             return None;
         }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/var_name.rs b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
index ada3310d8..376415e3d 100644
--- a/compiler/rustc_borrowck/src/diagnostics/var_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
@@ -1,9 +1,9 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 
+use crate::region_infer::RegionInferenceContext;
 use crate::Upvar;
-use crate::{nll::ToRegionVid, region_infer::RegionInferenceContext};
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::vec::{Idx, IndexSlice};
 use rustc_middle::mir::{Body, Local};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_span::source_map::Span;
@@ -14,7 +14,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
-        local_names: &IndexVec<Local, Option<Symbol>>,
+        local_names: &IndexSlice<Local, Option<Symbol>>,
         upvars: &[Upvar<'tcx>],
         fr: RegionVid,
     ) -> Option<(Option<Symbol>, Span)> {
@@ -46,7 +46,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             self.universal_regions().defining_ty.upvar_tys().position(|upvar_ty| {
                 debug!("get_upvar_index_for_region: upvar_ty={upvar_ty:?}");
                 tcx.any_free_region_meets(&upvar_ty, |r| {
-                    let r = r.to_region_vid();
+                    let r = r.as_var();
                     debug!("get_upvar_index_for_region: r={r:?} fr={fr:?}");
                     r == fr
                 })
@@ -96,7 +96,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             self.universal_regions().unnormalized_input_tys.iter().skip(implicit_inputs).position(
                 |arg_ty| {
                     debug!("get_argument_index_for_region: arg_ty = {arg_ty:?}");
-                    tcx.any_free_region_meets(arg_ty, |r| r.to_region_vid() == fr)
+                    tcx.any_free_region_meets(arg_ty, |r| r.as_var() == fr)
                 },
             )?;
 
@@ -113,7 +113,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn get_argument_name_and_span_for_region(
         &self,
         body: &Body<'tcx>,
-        local_names: &IndexVec<Local, Option<Symbol>>,
+        local_names: &IndexSlice<Local, Option<Symbol>>,
         argument_index: usize,
     ) -> (Option<Symbol>, Span) {
         let implicit_inputs = self.universal_regions().defining_ty.implicit_inputs();
diff --git a/compiler/rustc_borrowck/src/invalidation.rs b/compiler/rustc_borrowck/src/invalidation.rs
index 6217676d5..498d254da 100644
--- a/compiler/rustc_borrowck/src/invalidation.rs
+++ b/compiler/rustc_borrowck/src/invalidation.rs
@@ -79,6 +79,8 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
             }
             // Only relevant for mir typeck
             StatementKind::AscribeUserType(..)
+            // Only relevant for unsafeck
+            | StatementKind::PlaceMention(..)
             // Doesn't have any language semantics
             | StatementKind::Coverage(..)
             // Does not actually affect borrowck
@@ -118,21 +120,12 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                     LocalMutationIsAllowed::Yes,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(location, *drop_place, Deep);
-                self.consume_operand(location, new_value);
-            }
             TerminatorKind::Call {
                 func,
                 args,
                 destination,
                 target: _,
-                cleanup: _,
+                unwind: _,
                 from_hir_call: _,
                 fn_span: _,
             } => {
@@ -142,7 +135,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                 }
                 self.mutate_place(location, *destination, Deep);
             }
-            TerminatorKind::Assert { cond, expected: _, msg, target: _, cleanup: _ } => {
+            TerminatorKind::Assert { cond, expected: _, msg, target: _, unwind: _ } => {
                 self.consume_operand(location, cond);
                 use rustc_middle::mir::AssertKind;
                 if let AssertKind::BoundsCheck { len, index } = msg {
@@ -180,7 +173,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                 options: _,
                 line_spans: _,
                 destination: _,
-                cleanup: _,
+                unwind: _,
             } => {
                 for op in operands {
                     match op {
@@ -205,7 +198,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                 }
             }
             TerminatorKind::Goto { target: _ }
-            | TerminatorKind::Abort
+            | TerminatorKind::Terminate
             | TerminatorKind::Unreachable
             | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ }
             | TerminatorKind::FalseUnwind { real_target: _, unwind: _ } => {
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 0f591460e..a4b285a34 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -1,12 +1,11 @@
 //! This query borrow-checks the MIR to (further) ensure it is not broken.
 
-#![allow(rustc::potential_query_instability)]
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
 #![feature(min_specialization)]
 #![feature(never_type)]
-#![feature(once_cell)]
+#![feature(lazy_cell)]
 #![feature(rustc_attrs)]
 #![feature(stmt_expr_attributes)]
 #![feature(trusted_step)]
@@ -18,14 +17,13 @@ extern crate rustc_middle;
 #[macro_use]
 extern crate tracing;
 
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::dominators::Dominators;
-use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::{Diagnostic, DiagnosticBuilder, DiagnosticMessage, SubdiagnosticMessage};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_index::bit_set::ChunkedBitSet;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_infer::infer::{
     DefiningAnchor, InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin, TyCtxtInferExt,
 };
@@ -35,12 +33,13 @@ use rustc_middle::mir::{
     Place, PlaceElem, PlaceRef, VarDebugInfoContents,
 };
 use rustc_middle::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
-use rustc_middle::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
 use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
+use rustc_middle::mir::{ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
 use rustc_session::lint::builtin::UNUSED_MUT;
 use rustc_span::{Span, Symbol};
+use rustc_target::abi::FieldIdx;
 
 use either::Either;
 use smallvec::SmallVec;
@@ -95,13 +94,13 @@ pub mod consumers;
 
 use borrow_set::{BorrowData, BorrowSet};
 use dataflow::{BorrowIndex, BorrowckFlowState as Flows, BorrowckResults, Borrows};
-use nll::{PoloniusOutput, ToRegionVid};
+use nll::PoloniusOutput;
 use place_ext::PlaceExt;
 use places_conflict::{places_conflict, PlaceConflictBias};
 use region_infer::RegionInferenceContext;
 use renumber::RegionCtxt;
 
-fluent_messages! { "../locales/en-US.ftl" }
+fluent_messages! { "../messages.ftl" }
 
 // FIXME(eddyb) perhaps move this somewhere more centrally.
 #[derive(Debug)]
@@ -142,7 +141,7 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> &Bor
         debug!("Skipping borrowck because of injected body");
         // Let's make up a borrowck result! Fun times!
         let result = BorrowCheckResult {
-            concrete_opaque_types: VecMap::new(),
+            concrete_opaque_types: FxIndexMap::default(),
             closure_requirements: None,
             used_mut_upvars: SmallVec::new(),
             tainted_by_errors: None,
@@ -155,7 +154,7 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> &Bor
     let infcx =
         tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id)).build();
     let input_body: &Body<'_> = &input_body.borrow();
-    let promoted: &IndexVec<_, _> = &promoted.borrow();
+    let promoted: &IndexSlice<_, _> = &promoted.borrow();
     let opt_closure_req = do_mir_borrowck(&infcx, input_body, promoted, false).0;
     debug!("mir_borrowck done");
 
@@ -171,7 +170,7 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> &Bor
 fn do_mir_borrowck<'tcx>(
     infcx: &InferCtxt<'tcx>,
     input_body: &Body<'tcx>,
-    input_promoted: &IndexVec<Promoted, Body<'tcx>>,
+    input_promoted: &IndexSlice<Promoted, Body<'tcx>>,
     return_body_with_facts: bool,
 ) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
     let def = input_body.source.with_opt_param().as_local().unwrap();
@@ -224,7 +223,7 @@ fn do_mir_borrowck<'tcx>(
     // be modified (in place) to contain non-lexical lifetimes. It
     // will have a lifetime tied to the inference context.
     let mut body_owned = input_body.clone();
-    let mut promoted = input_promoted.clone();
+    let mut promoted = input_promoted.to_owned();
     let free_regions =
         nll::replace_regions_in_mir(&infcx, param_env, &mut body_owned, &mut promoted);
     let body = &body_owned; // no further changes
@@ -404,7 +403,7 @@ fn do_mir_borrowck<'tcx>(
     // Note that this set is expected to be small - only upvars from closures
     // would have a chance of erroneously adding non-user-defined mutable vars
     // to the set.
-    let temporary_used_locals: FxHashSet<Local> = mbcx
+    let temporary_used_locals: FxIndexSet<Local> = mbcx
         .used_mut
         .iter()
         .filter(|&local| !mbcx.body.local_decls[*local].is_user_variable())
@@ -491,7 +490,7 @@ pub struct BodyWithBorrowckFacts<'tcx> {
 
 pub struct BorrowckInferCtxt<'cx, 'tcx> {
     pub(crate) infcx: &'cx InferCtxt<'tcx>,
-    pub(crate) reg_var_to_origin: RefCell<FxHashMap<ty::RegionVid, RegionCtxt>>,
+    pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
 }
 
 impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
@@ -508,20 +507,13 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
         F: Fn() -> RegionCtxt,
     {
         let next_region = self.infcx.next_region_var(origin);
-        let vid = next_region
-            .as_var()
-            .unwrap_or_else(|| bug!("expected RegionKind::RegionVar on {:?}", next_region));
+        let vid = next_region.as_var();
 
-        if cfg!(debug_assertions) {
+        if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
             debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
             let ctxt = get_ctxt_fn();
             let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
-            let prev = var_to_origin.insert(vid, ctxt);
-
-            // This only makes sense if not called in a canonicalization context. If this
-            // ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
-            // or modify how we track nll region vars for that map.
-            assert!(matches!(prev, None));
+            var_to_origin.insert(vid, ctxt);
         }
 
         next_region
@@ -537,20 +529,13 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
         F: Fn() -> RegionCtxt,
     {
         let next_region = self.infcx.next_nll_region_var(origin.clone());
-        let vid = next_region
-            .as_var()
-            .unwrap_or_else(|| bug!("expected RegionKind::RegionVar on {:?}", next_region));
+        let vid = next_region.as_var();
 
-        if cfg!(debug_assertions) {
+        if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
             debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
             let ctxt = get_ctxt_fn();
             let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
-            let prev = var_to_origin.insert(vid, ctxt);
-
-            // This only makes sense if not called in a canonicalization context. If this
-            // ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
-            // or modify how we track nll region vars for that map.
-            assert!(matches!(prev, None));
+            var_to_origin.insert(vid, ctxt);
         }
 
         next_region
@@ -588,7 +573,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     /// borrow errors that is handled by the `reservation_error_reported` field as the inclusion
     /// of the `Span` type (while required to mute some errors) stops the muting of the reservation
     /// errors.
-    access_place_error_reported: FxHashSet<(Place<'tcx>, Span)>,
+    access_place_error_reported: FxIndexSet<(Place<'tcx>, Span)>,
     /// This field keeps track of when borrow conflict errors are reported
     /// for reservations, so that we don't report seemingly duplicate
     /// errors for corresponding activations.
@@ -596,20 +581,20 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     // FIXME: ideally this would be a set of `BorrowIndex`, not `Place`s,
     // but it is currently inconvenient to track down the `BorrowIndex`
     // at the time we detect and report a reservation error.
-    reservation_error_reported: FxHashSet<Place<'tcx>>,
+    reservation_error_reported: FxIndexSet<Place<'tcx>>,
     /// This fields keeps track of the `Span`s that we have
     /// used to report extra information for `FnSelfUse`, to avoid
     /// unnecessarily verbose errors.
-    fn_self_span_reported: FxHashSet<Span>,
+    fn_self_span_reported: FxIndexSet<Span>,
     /// This field keeps track of errors reported in the checking of uninitialized variables,
     /// so that we don't report seemingly duplicate errors.
-    uninitialized_error_reported: FxHashSet<PlaceRef<'tcx>>,
+    uninitialized_error_reported: FxIndexSet<PlaceRef<'tcx>>,
     /// This field keeps track of all the local variables that are declared mut and are mutated.
     /// Used for the warning issued by an unused mutable local variable.
-    used_mut: FxHashSet<Local>,
+    used_mut: FxIndexSet<Local>,
     /// If the function we're checking is a closure, then we'll need to report back the list of
     /// mutable upvars that have been used. This field keeps track of them.
-    used_mut_upvars: SmallVec<[Field; 8]>,
+    used_mut_upvars: SmallVec<[FieldIdx; 8]>,
     /// Region inference context. This contains the results from region inference and lets us e.g.
     /// find out which CFG points are contained in each borrow region.
     regioncx: Rc<RegionInferenceContext<'tcx>>,
@@ -628,7 +613,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
 
     /// Record the region names generated for each region in the given
     /// MIR def so that we can reuse them later in help/error messages.
-    region_names: RefCell<FxHashMap<RegionVid, RegionName>>,
+    region_names: RefCell<FxIndexMap<RegionVid, RegionName>>,
 
     /// The counter for generating new region names.
     next_region_name: RefCell<usize>,
@@ -691,6 +676,8 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
             }
             // Only relevant for mir typeck
             StatementKind::AscribeUserType(..)
+            // Only relevant for unsafeck
+            | StatementKind::PlaceMention(..)
             // Doesn't have any language semantics
             | StatementKind::Coverage(..)
             // These do not actually affect borrowck
@@ -744,21 +731,12 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
                     flow_state,
                 );
             }
-            TerminatorKind::DropAndReplace {
-                place: drop_place,
-                value: new_value,
-                target: _,
-                unwind: _,
-            } => {
-                self.mutate_place(loc, (*drop_place, span), Deep, flow_state);
-                self.consume_operand(loc, (new_value, span), flow_state);
-            }
             TerminatorKind::Call {
                 func,
                 args,
                 destination,
                 target: _,
-                cleanup: _,
+                unwind: _,
                 from_hir_call: _,
                 fn_span: _,
             } => {
@@ -768,7 +746,7 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
                 }
                 self.mutate_place(loc, (*destination, span), Deep, flow_state);
             }
-            TerminatorKind::Assert { cond, expected: _, msg, target: _, cleanup: _ } => {
+            TerminatorKind::Assert { cond, expected: _, msg, target: _, unwind: _ } => {
                 self.consume_operand(loc, (cond, span), flow_state);
                 use rustc_middle::mir::AssertKind;
                 if let AssertKind::BoundsCheck { len, index } = msg {
@@ -788,7 +766,7 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
                 options: _,
                 line_spans: _,
                 destination: _,
-                cleanup: _,
+                unwind: _,
             } => {
                 for op in operands {
                     match op {
@@ -819,7 +797,7 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
             }
 
             TerminatorKind::Goto { target: _ }
-            | TerminatorKind::Abort
+            | TerminatorKind::Terminate
             | TerminatorKind::Unreachable
             | TerminatorKind::Resume
             | TerminatorKind::Return
@@ -863,11 +841,10 @@ impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtx
                 }
             }
 
-            TerminatorKind::Abort
+            TerminatorKind::Terminate
             | TerminatorKind::Assert { .. }
             | TerminatorKind::Call { .. }
             | TerminatorKind::Drop { .. }
-            | TerminatorKind::DropAndReplace { .. }
             | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ }
             | TerminatorKind::FalseUnwind { real_target: _, unwind: _ }
             | TerminatorKind::Goto { .. }
@@ -1185,12 +1162,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             this.buffer_error(err);
                         }
                         WriteKind::StorageDeadOrDrop => this
-                            .report_borrowed_value_does_not_live_long_enough(
-                                location,
-                                borrow,
-                                place_span,
-                                Some(kind),
-                            ),
+                            .report_storage_dead_or_drop_of_borrowed(location, place_span, borrow),
                         WriteKind::Mutate => {
                             this.report_illegal_mutation_of_borrowed(location, place_span, borrow)
                         }
@@ -1367,7 +1339,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             self.infcx.tcx.mir_borrowck(def_id);
                         debug!("{:?} used_mut_upvars={:?}", def_id, used_mut_upvars);
                         for field in used_mut_upvars {
-                            self.propagate_closure_used_mut_upvar(&operands[field.index()]);
+                            self.propagate_closure_used_mut_upvar(&operands[*field]);
                         }
                     }
                     AggregateKind::Adt(..)
@@ -2302,7 +2274,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     /// then returns the index of the field being projected. Note that this closure will always
     /// be `self` in the current MIR, because that is the only time we directly access the fields
     /// of a closure type.
-    fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<Field> {
+    fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<FieldIdx> {
         path_utils::is_upvar_field_projection(self.infcx.tcx, &self.upvars, place_ref, self.body())
     }
 
@@ -2334,7 +2306,7 @@ mod error {
         /// same primary span come out in a consistent order.
         buffered_move_errors:
             BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>)>,
-        buffered_mut_errors: FxHashMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
+        buffered_mut_errors: FxIndexMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
         /// Diagnostics to be reported buffer.
         buffered: Vec<Diagnostic>,
         /// Set to Some if we emit an error during borrowck
diff --git a/compiler/rustc_borrowck/src/member_constraints.rs b/compiler/rustc_borrowck/src/member_constraints.rs
index 4af324f74..f637e6a95 100644
--- a/compiler/rustc_borrowck/src/member_constraints.rs
+++ b/compiler/rustc_borrowck/src/member_constraints.rs
@@ -1,8 +1,8 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 use rustc_data_structures::captures::Captures;
-use rustc_data_structures::fx::FxHashMap;
-use rustc_index::vec::IndexVec;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_middle::infer::MemberConstraint;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
@@ -18,7 +18,7 @@ where
 {
     /// Stores the first "member" constraint for a given `R0`. This is an
     /// index into the `constraints` vector below.
-    first_constraints: FxHashMap<R, NllMemberConstraintIndex>,
+    first_constraints: FxIndexMap<R, NllMemberConstraintIndex>,
 
     /// Stores the data about each `R0 member of [R1..Rn]` constraint.
     /// These are organized into a linked list, so each constraint
@@ -132,7 +132,7 @@ where
 
         let MemberConstraintSet { first_constraints, mut constraints, choice_regions } = self;
 
-        let mut first_constraints2 = FxHashMap::default();
+        let mut first_constraints2 = FxIndexMap::default();
         first_constraints2.reserve(first_constraints.len());
 
         for (r1, start1) in first_constraints {
@@ -215,7 +215,7 @@ where
 /// target_list: A -> B -> C -> D -> E -> F -> (None)
 /// ```
 fn append_list(
-    constraints: &mut IndexVec<NllMemberConstraintIndex, NllMemberConstraint<'_>>,
+    constraints: &mut IndexSlice<NllMemberConstraintIndex, NllMemberConstraint<'_>>,
     target_list: NllMemberConstraintIndex,
     source_list: NllMemberConstraintIndex,
 ) {
diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index 96228338a..59a3ab318 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -2,15 +2,15 @@
 #![deny(rustc::diagnostic_outside_of_impl)]
 //! The entry point of the NLL borrow checker.
 
-use rustc_data_structures::vec_map::VecMap;
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir::def_id::LocalDefId;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::IndexSlice;
 use rustc_middle::mir::{create_dump_file, dump_enabled, dump_mir, PassWhere};
 use rustc_middle::mir::{
     BasicBlock, Body, ClosureOutlivesSubject, ClosureRegionRequirements, LocalKind, Location,
     Promoted,
 };
-use rustc_middle::ty::{self, OpaqueHiddenType, Region, RegionVid, TyCtxt};
+use rustc_middle::ty::{self, OpaqueHiddenType, TyCtxt};
 use rustc_span::symbol::sym;
 use std::env;
 use std::io;
@@ -44,7 +44,7 @@ pub type PoloniusOutput = Output<RustcFacts>;
 /// closure requirements to propagate, and any generated errors.
 pub(crate) struct NllOutput<'tcx> {
     pub regioncx: RegionInferenceContext<'tcx>,
-    pub opaque_type_values: VecMap<LocalDefId, OpaqueHiddenType<'tcx>>,
+    pub opaque_type_values: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
     pub polonius_input: Option<Box<AllFacts>>,
     pub polonius_output: Option<Rc<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
@@ -59,7 +59,7 @@ pub(crate) fn replace_regions_in_mir<'tcx>(
     infcx: &BorrowckInferCtxt<'_, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body: &mut Body<'tcx>,
-    promoted: &mut IndexVec<Promoted, Body<'tcx>>,
+    promoted: &mut IndexSlice<Promoted, Body<'tcx>>,
 ) -> UniversalRegions<'tcx> {
     let def = body.source.with_opt_param().as_local().unwrap();
 
@@ -158,7 +158,7 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
     infcx: &BorrowckInferCtxt<'_, 'tcx>,
     universal_regions: UniversalRegions<'tcx>,
     body: &Body<'tcx>,
-    promoted: &IndexVec<Promoted, Body<'tcx>>,
+    promoted: &IndexSlice<Promoted, Body<'tcx>>,
     location_table: &LocationTable,
     param_env: ty::ParamEnv<'tcx>,
     flow_inits: &mut ResultsCursor<'cx, 'tcx, MaybeInitializedPlaces<'cx, 'tcx>>,
@@ -377,7 +377,7 @@ pub(super) fn dump_annotation<'tcx>(
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
-    opaque_type_values: &VecMap<LocalDefId, OpaqueHiddenType<'tcx>>,
+    opaque_type_values: &FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
     errors: &mut crate::error::BorrowckErrors<'tcx>,
 ) {
     let tcx = infcx.tcx;
@@ -444,27 +444,6 @@ fn for_each_region_constraint<'tcx>(
     Ok(())
 }
 
-/// Right now, we piggy back on the `ReVar` to store our NLL inference
-/// regions. These are indexed with `RegionVid`. This method will
-/// assert that the region is a `ReVar` and extract its internal index.
-/// This is reasonable because in our MIR we replace all universal regions
-/// with inference variables.
-pub trait ToRegionVid {
-    fn to_region_vid(self) -> RegionVid;
-}
-
-impl<'tcx> ToRegionVid for Region<'tcx> {
-    fn to_region_vid(self) -> RegionVid {
-        if let ty::ReVar(vid) = *self { vid } else { bug!("region is not an ReVar: {:?}", self) }
-    }
-}
-
-impl ToRegionVid for RegionVid {
-    fn to_region_vid(self) -> RegionVid {
-        self
-    }
-}
-
 pub(crate) trait ConstraintDescription {
     fn description(&self) -> &'static str;
 }
diff --git a/compiler/rustc_borrowck/src/path_utils.rs b/compiler/rustc_borrowck/src/path_utils.rs
index f8a99a269..ea9f8683c 100644
--- a/compiler/rustc_borrowck/src/path_utils.rs
+++ b/compiler/rustc_borrowck/src/path_utils.rs
@@ -7,8 +7,9 @@ use crate::BorrowIndex;
 use crate::Upvar;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_middle::mir::BorrowKind;
-use rustc_middle::mir::{BasicBlock, Body, Field, Location, Place, PlaceRef, ProjectionElem};
+use rustc_middle::mir::{BasicBlock, Body, Location, Place, PlaceRef, ProjectionElem};
 use rustc_middle::ty::TyCtxt;
+use rustc_target::abi::FieldIdx;
 
 /// Returns `true` if the borrow represented by `kind` is
 /// allowed to be split into separate Reservation and
@@ -148,7 +149,7 @@ pub(crate) fn is_upvar_field_projection<'tcx>(
     upvars: &[Upvar<'tcx>],
     place_ref: PlaceRef<'tcx>,
     body: &Body<'tcx>,
-) -> Option<Field> {
+) -> Option<FieldIdx> {
     let mut place_ref = place_ref;
     let mut by_ref = false;
 
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index e6195de40..729f3dbff 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -3,11 +3,11 @@ use std::rc::Rc;
 
 use rustc_data_structures::binary_search_util;
 use rustc_data_structures::frozen::Frozen;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::scc::Sccs;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::CRATE_DEF_ID;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_infer::infer::outlives::test_type_match;
 use rustc_infer::infer::region_constraints::{GenericKind, VarInfos, VerifyBound, VerifyIfEq};
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin};
@@ -27,7 +27,7 @@ use crate::{
     },
     diagnostics::{RegionErrorKind, RegionErrors, UniverseInfo},
     member_constraints::{MemberConstraintSet, NllMemberConstraintIndex},
-    nll::{PoloniusOutput, ToRegionVid},
+    nll::PoloniusOutput,
     region_infer::reverse_sccs::ReverseSccGraph,
     region_infer::values::{
         LivenessValues, PlaceholderIndices, RegionElement, RegionValueElements, RegionValues,
@@ -88,7 +88,7 @@ pub struct RegionInferenceContext<'tcx> {
     member_constraints_applied: Vec<AppliedMemberConstraint>,
 
     /// Map universe indexes to information on why we created it.
-    universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+    universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
     /// Contains the minimum universe of any variable within the same
     /// SCC. We will ensure that no SCC contains values that are not
@@ -255,15 +255,16 @@ fn sccs_info<'cx, 'tcx>(
     let var_to_origin = infcx.reg_var_to_origin.borrow();
 
     let mut var_to_origin_sorted = var_to_origin.clone().into_iter().collect::<Vec<_>>();
-    var_to_origin_sorted.sort_by(|a, b| a.0.cmp(&b.0));
-    let mut debug_str = "region variables to origins:\n".to_string();
+    var_to_origin_sorted.sort_by_key(|vto| vto.0);
+
+    let mut reg_vars_to_origins_str = "region variables to origins:\n".to_string();
     for (reg_var, origin) in var_to_origin_sorted.into_iter() {
-        debug_str.push_str(&format!("{:?}: {:?}\n", reg_var, origin));
+        reg_vars_to_origins_str.push_str(&format!("{:?}: {:?}\n", reg_var, origin));
     }
-    debug!(debug_str);
+    debug!("{}", reg_vars_to_origins_str);
 
     let num_components = sccs.scc_data().ranges().len();
-    let mut components = vec![FxHashSet::default(); num_components];
+    let mut components = vec![FxIndexSet::default(); num_components];
 
     for (reg_var_idx, scc_idx) in sccs.scc_indices().iter().enumerate() {
         let reg_var = ty::RegionVid::from_usize(reg_var_idx);
@@ -275,12 +276,12 @@ fn sccs_info<'cx, 'tcx>(
     for (scc_idx, reg_vars_origins) in components.iter().enumerate() {
         let regions_info = reg_vars_origins.clone().into_iter().collect::<Vec<_>>();
         components_str.push_str(&format!(
-            "{:?}: {:?})",
+            "{:?}: {:?},\n)",
             ConstraintSccIndex::from_usize(scc_idx),
             regions_info,
         ))
     }
-    debug!(components_str);
+    debug!("{}", components_str);
 
     // calculate the best representative for each component
     let components_representatives = components
@@ -295,9 +296,9 @@ fn sccs_info<'cx, 'tcx>(
 
             (ConstraintSccIndex::from_usize(scc_idx), repr)
         })
-        .collect::<FxHashMap<_, _>>();
+        .collect::<FxIndexMap<_, _>>();
 
-    let mut scc_node_to_edges = FxHashMap::default();
+    let mut scc_node_to_edges = FxIndexMap::default();
     for (scc_idx, repr) in components_representatives.iter() {
         let edges_range = sccs.scc_data().ranges()[*scc_idx].clone();
         let edges = &sccs.scc_data().all_successors()[edges_range];
@@ -325,7 +326,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
         outlives_constraints: OutlivesConstraintSet<'tcx>,
         member_constraints_in: MemberConstraintSet<'tcx, RegionVid>,
-        universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+        universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
         type_tests: Vec<TypeTest<'tcx>>,
         liveness_constraints: LivenessValues<RegionVid>,
         elements: &Rc<RegionValueElements>,
@@ -398,7 +399,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// the minimum, or narrowest, universe.
     fn compute_scc_universes(
         constraint_sccs: &Sccs<RegionVid, ConstraintSccIndex>,
-        definitions: &IndexVec<RegionVid, RegionDefinition<'tcx>>,
+        definitions: &IndexSlice<RegionVid, RegionDefinition<'tcx>>,
     ) -> IndexVec<ConstraintSccIndex, ty::UniverseIndex> {
         let num_sccs = constraint_sccs.num_sccs();
         let mut scc_universes = IndexVec::from_elem_n(ty::UniverseIndex::MAX, num_sccs);
@@ -485,7 +486,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// more details.
     fn compute_scc_representatives(
         constraints_scc: &Sccs<RegionVid, ConstraintSccIndex>,
-        definitions: &IndexVec<RegionVid, RegionDefinition<'tcx>>,
+        definitions: &IndexSlice<RegionVid, RegionDefinition<'tcx>>,
     ) -> IndexVec<ConstraintSccIndex, ty::RegionVid> {
         let num_sccs = constraints_scc.num_sccs();
         let next_region_vid = definitions.next_index();
@@ -522,6 +523,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// outlives `'a` and hence contains R0 and R1.
     fn init_free_and_bound_regions(&mut self) {
         // Update the names (if any)
+        // This iterator has unstable order but we collect it all into an IndexVec
         for (external_name, variable) in self.universal_regions.named_universal_regions() {
             debug!(
                 "init_universal_regions: region {:?} has external name {:?}",
@@ -591,14 +593,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// Returns `true` if the region `r` contains the point `p`.
     ///
     /// Panics if called before `solve()` executes,
-    pub(crate) fn region_contains(&self, r: impl ToRegionVid, p: impl ToElementIndex) -> bool {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+    pub(crate) fn region_contains(&self, r: RegionVid, p: impl ToElementIndex) -> bool {
+        let scc = self.constraint_sccs.scc(r);
         self.scc_values.contains(scc, p)
     }
 
     /// Returns access to the value of `r` for debugging purposes.
     pub(crate) fn region_value_str(&self, r: RegionVid) -> String {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+        let scc = self.constraint_sccs.scc(r);
         self.scc_values.region_value_str(scc)
     }
 
@@ -606,24 +608,21 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &'a self,
         r: RegionVid,
     ) -> impl Iterator<Item = ty::PlaceholderRegion> + 'a {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+        let scc = self.constraint_sccs.scc(r);
         self.scc_values.placeholders_contained_in(scc)
     }
 
     /// Returns access to the value of `r` for debugging purposes.
     pub(crate) fn region_universe(&self, r: RegionVid) -> ty::UniverseIndex {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+        let scc = self.constraint_sccs.scc(r);
         self.scc_universes[scc]
     }
 
     /// Once region solving has completed, this function will return
     /// the member constraints that were applied to the value of a given
     /// region `r`. See `AppliedMemberConstraint`.
-    pub(crate) fn applied_member_constraints(
-        &self,
-        r: impl ToRegionVid,
-    ) -> &[AppliedMemberConstraint] {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+    pub(crate) fn applied_member_constraints(&self, r: RegionVid) -> &[AppliedMemberConstraint] {
+        let scc = self.constraint_sccs.scc(r);
         binary_search_util::binary_search_slice(
             &self.member_constraints_applied,
             |applied| applied.member_region_scc,
@@ -918,7 +917,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // Sometimes we register equivalent type-tests that would
         // result in basically the exact same error being reported to
         // the user. Avoid that.
-        let mut deduplicate_errors = FxHashSet::default();
+        let mut deduplicate_errors = FxIndexSet::default();
 
         for type_test in &self.type_tests {
             debug!("check_type_test: {:?}", type_test);
@@ -1131,7 +1130,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             let r_vid = self.to_region_vid(r);
             let r_scc = self.constraint_sccs.scc(r_vid);
 
-            // The challenge if this. We have some region variable `r`
+            // The challenge is this. We have some region variable `r`
             // whose value is a set of CFG points and universal
             // regions. We want to find if that set is *equivalent* to
             // any of the named regions found in the closure.
@@ -1504,6 +1503,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // the outlives suggestions or the debug output from `#[rustc_regions]` would be
         // duplicated. The polonius subset errors are deduplicated here, while keeping the
         // CFG-location ordering.
+        // We can iterate the HashMap here because the result is sorted afterwards.
+        #[allow(rustc::potential_query_instability)]
         let mut subset_errors: Vec<_> = polonius_output
             .subset_errors
             .iter()
@@ -2213,7 +2214,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // is in the same SCC or something. In that case, find what
         // appears to be the most interesting point to report to the
         // user via an even more ad-hoc guess.
-        categorized_path.sort_by(|p0, p1| p0.category.cmp(&p1.category));
+        categorized_path.sort_by_key(|p| p.category);
         debug!("sorted_path={:#?}", categorized_path);
 
         (categorized_path.remove(0), extra_info)
@@ -2230,7 +2231,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         r: RegionVid,
         body: &Body<'_>,
     ) -> Option<Location> {
-        let scc = self.constraint_sccs.scc(r.to_region_vid());
+        let scc = self.constraint_sccs.scc(r);
         let locations = self.scc_values.locations_outlived_by(scc);
         for location in locations {
             let bb = &body[location.block];
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index c550e37c6..2b16655cf 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -1,5 +1,4 @@
-use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
-use rustc_data_structures::vec_map::VecMap;
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::OpaqueTyOrigin;
@@ -61,11 +60,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn infer_opaque_types(
         &self,
         infcx: &InferCtxt<'tcx>,
-        opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
-    ) -> VecMap<LocalDefId, OpaqueHiddenType<'tcx>> {
-        let mut result: VecMap<LocalDefId, OpaqueHiddenType<'tcx>> = VecMap::new();
+        opaque_ty_decls: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
+    ) -> FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>> {
+        let mut result: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>> = FxIndexMap::default();
 
-        let member_constraints: FxHashMap<_, _> = self
+        let member_constraints: FxIndexMap<_, _> = self
             .member_constraints
             .all_indices()
             .map(|ci| (self.member_constraints[ci].key, ci))
@@ -284,7 +283,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
         // hidden type is well formed even without those bounds.
         let predicate = ty::Binder::dummy(ty::PredicateKind::WellFormed(definition_ty.into()));
 
-        let id_substs = InternalSubsts::identity_for_item(self.tcx, def_id.to_def_id());
+        let id_substs = InternalSubsts::identity_for_item(self.tcx, def_id);
 
         // Require that the hidden type actually fulfills all the bounds of the opaque type, even without
         // the bounds that the function supplies.
@@ -325,7 +324,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
         if errors.is_empty() {
             definition_ty
         } else {
-            let reported = infcx.err_ctxt().report_fulfillment_errors(&errors, None);
+            let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
             self.tcx.ty_error(reported)
         }
     }
@@ -364,7 +363,7 @@ fn check_opaque_type_parameter_valid(
         OpaqueTyOrigin::TyAlias => {}
     }
     let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
-    let mut seen_params: FxHashMap<_, Vec<_>> = FxHashMap::default();
+    let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();
     for (i, arg) in opaque_type_key.substs.iter().enumerate() {
         let arg_is_param = match arg.unpack() {
             GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
diff --git a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
index 167f66460..23a59c128 100644
--- a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
+++ b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
@@ -3,7 +3,7 @@
 use crate::constraints::ConstraintSccIndex;
 use crate::RegionInferenceContext;
 use itertools::Itertools;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::vec_graph::VecGraph;
 use rustc_data_structures::graph::WithSuccessors;
 use rustc_middle::ty::RegionVid;
@@ -14,7 +14,7 @@ pub(crate) struct ReverseSccGraph {
     graph: VecGraph<ConstraintSccIndex>,
     /// For each SCC, the range of `universal_regions` that use that SCC as
     /// their value.
-    scc_regions: FxHashMap<ConstraintSccIndex, Range<usize>>,
+    scc_regions: FxIndexMap<ConstraintSccIndex, Range<usize>>,
     /// All of the universal regions, in grouped so that `scc_regions` can
     /// index into here.
     universal_regions: Vec<RegionVid>,
@@ -26,7 +26,7 @@ impl ReverseSccGraph {
         &'a self,
         scc0: ConstraintSccIndex,
     ) -> impl Iterator<Item = RegionVid> + 'a {
-        let mut duplicates = FxHashSet::default();
+        let mut duplicates = FxIndexSet::default();
         self.graph
             .depth_first_search(scc0)
             .flat_map(move |scc1| {
@@ -55,7 +55,7 @@ impl RegionInferenceContext<'_> {
         paired_scc_regions.sort();
         let universal_regions = paired_scc_regions.iter().map(|&(_, region)| region).collect();
 
-        let mut scc_regions = FxHashMap::default();
+        let mut scc_regions = FxIndexMap::default();
         let mut start = 0;
         for (scc, group) in &paired_scc_regions.into_iter().group_by(|(scc, _)| *scc) {
             let group_size = group.count();
diff --git a/compiler/rustc_borrowck/src/renumber.rs b/compiler/rustc_borrowck/src/renumber.rs
index 016f6f78d..94ce29dfe 100644
--- a/compiler/rustc_borrowck/src/renumber.rs
+++ b/compiler/rustc_borrowck/src/renumber.rs
@@ -1,7 +1,7 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 use crate::BorrowckInferCtxt;
-use rustc_index::vec::IndexVec;
+use rustc_index::vec::IndexSlice;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::visit::{MutVisitor, TyContext};
 use rustc_middle::mir::Constant;
@@ -16,35 +16,17 @@ use rustc_span::{Span, Symbol};
 pub fn renumber_mir<'tcx>(
     infcx: &BorrowckInferCtxt<'_, 'tcx>,
     body: &mut Body<'tcx>,
-    promoted: &mut IndexVec<Promoted, Body<'tcx>>,
+    promoted: &mut IndexSlice<Promoted, Body<'tcx>>,
 ) {
     debug!(?body.arg_count);
 
-    let mut visitor = NllVisitor { infcx };
+    let mut renumberer = RegionRenumberer { infcx };
 
     for body in promoted.iter_mut() {
-        visitor.visit_body(body);
+        renumberer.visit_body(body);
     }
 
-    visitor.visit_body(body);
-}
-
-/// Replaces all regions appearing in `value` with fresh inference
-/// variables.
-#[instrument(skip(infcx, get_ctxt_fn), level = "debug")]
-pub(crate) fn renumber_regions<'tcx, T, F>(
-    infcx: &BorrowckInferCtxt<'_, 'tcx>,
-    value: T,
-    get_ctxt_fn: F,
-) -> T
-where
-    T: TypeFoldable<TyCtxt<'tcx>>,
-    F: Fn() -> RegionCtxt,
-{
-    infcx.tcx.fold_regions(value, |_region, _depth| {
-        let origin = NllRegionVariableOrigin::Existential { from_forall: false };
-        infcx.next_nll_region_var(origin, || get_ctxt_fn())
-    })
+    renumberer.visit_body(body);
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
@@ -69,12 +51,10 @@ impl RegionCtxt {
     /// Used to determine the representative of a component in the strongly connected
     /// constraint graph
     pub(crate) fn preference_value(self) -> usize {
-        let _anon = Symbol::intern("anon");
-
         match self {
             RegionCtxt::Unknown => 1,
             RegionCtxt::Existential(None) => 2,
-            RegionCtxt::Existential(Some(_anon)) | RegionCtxt::Free(_anon) => 2,
+            RegionCtxt::Existential(Some(_)) | RegionCtxt::Free(_) => 2,
             RegionCtxt::Location(_) => 3,
             RegionCtxt::TyContext(_) => 4,
             _ => 5,
@@ -82,21 +62,26 @@ impl RegionCtxt {
     }
 }
 
-struct NllVisitor<'a, 'tcx> {
+struct RegionRenumberer<'a, 'tcx> {
     infcx: &'a BorrowckInferCtxt<'a, 'tcx>,
 }
 
-impl<'a, 'tcx> NllVisitor<'a, 'tcx> {
+impl<'a, 'tcx> RegionRenumberer<'a, 'tcx> {
+    /// Replaces all regions appearing in `value` with fresh inference
+    /// variables.
     fn renumber_regions<T, F>(&mut self, value: T, region_ctxt_fn: F) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
         F: Fn() -> RegionCtxt,
     {
-        renumber_regions(self.infcx, value, region_ctxt_fn)
+        let origin = NllRegionVariableOrigin::Existential { from_forall: false };
+        self.infcx.tcx.fold_regions(value, |_region, _depth| {
+            self.infcx.next_nll_region_var(origin, || region_ctxt_fn())
+        })
     }
 }
 
-impl<'a, 'tcx> MutVisitor<'tcx> for NllVisitor<'a, 'tcx> {
+impl<'a, 'tcx> MutVisitor<'tcx> for RegionRenumberer<'a, 'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.infcx.tcx
     }
@@ -124,9 +109,9 @@ impl<'a, 'tcx> MutVisitor<'tcx> for NllVisitor<'a, 'tcx> {
     }
 
     #[instrument(skip(self), level = "debug")]
-    fn visit_constant(&mut self, constant: &mut Constant<'tcx>, _location: Location) {
+    fn visit_constant(&mut self, constant: &mut Constant<'tcx>, location: Location) {
         let literal = constant.literal;
-        constant.literal = self.renumber_regions(literal, || RegionCtxt::Location(_location));
+        constant.literal = self.renumber_regions(literal, || RegionCtxt::Location(location));
         debug!("constant: {:#?}", constant);
     }
 }
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index a93561350..71eae7b27 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -12,7 +12,6 @@ use rustc_span::{Span, DUMMY_SP};
 
 use crate::{
     constraints::OutlivesConstraint,
-    nll::ToRegionVid,
     region_infer::TypeTest,
     type_check::{Locations, MirTypeckRegionConstraints},
     universal_regions::UniversalRegions,
@@ -198,7 +197,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
 
     fn to_region_vid(&mut self, r: ty::Region<'tcx>) -> ty::RegionVid {
         if let ty::RePlaceholder(placeholder) = *r {
-            self.constraints.placeholder_region(self.infcx, placeholder).to_region_vid()
+            self.constraints.placeholder_region(self.infcx, placeholder).as_var()
         } else {
             self.universal_regions.to_region_vid(r)
         }
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index 717020ea5..17e702eb8 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -19,7 +19,7 @@ use super::{Locations, TypeChecker};
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// Check explicit closure signature annotation,
-    /// e.g., `|x: FxHashMap<_, &'static u32>| ...`.
+    /// e.g., `|x: FxIndexMap<_, &'static u32>| ...`.
     #[instrument(skip(self, body), level = "debug")]
     pub(super) fn check_signature_annotation(&mut self, body: &Body<'tcx>) {
         let mir_def_id = body.source.def_id().expect_local();
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/local_use_map.rs b/compiler/rustc_borrowck/src/type_check/liveness/local_use_map.rs
index 8023ef60d..2c387edfe 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/local_use_map.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/local_use_map.rs
@@ -63,7 +63,7 @@ impl LocalUseMap {
         elements: &RegionValueElements,
         body: &Body<'_>,
     ) -> Self {
-        let nones = IndexVec::from_elem_n(None, body.local_decls.len());
+        let nones = IndexVec::from_elem(None, &body.local_decls);
         let mut local_use_map = LocalUseMap {
             first_def_at: nones.clone(),
             first_use_at: nones.clone(),
@@ -76,7 +76,7 @@ impl LocalUseMap {
         }
 
         let mut locals_with_use_data: IndexVec<Local, bool> =
-            IndexVec::from_elem_n(false, body.local_decls.len());
+            IndexVec::from_elem(false, &body.local_decls);
         live_locals.iter().for_each(|&local| locals_with_use_data[local] = true);
 
         LocalUseMapBuild { local_use_map: &mut local_use_map, elements, locals_with_use_data }
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
index a411aec51..f1ad0ca55 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
@@ -11,7 +11,6 @@ use crate::{
     constraints::OutlivesConstraintSet,
     facts::{AllFacts, AllFactsExt},
     location::LocationTable,
-    nll::ToRegionVid,
     region_infer::values::RegionValueElements,
     universal_regions::UniversalRegions,
 };
@@ -80,9 +79,7 @@ fn compute_relevant_live_locals<'tcx>(
 ) -> (Vec<Local>, Vec<Local>) {
     let (boring_locals, relevant_live_locals): (Vec<_>, Vec<_>) =
         body.local_decls.iter_enumerated().partition_map(|(local, local_decl)| {
-            if tcx.all_free_regions_meet(&local_decl.ty, |r| {
-                free_regions.contains(&r.to_region_vid())
-            }) {
+            if tcx.all_free_regions_meet(&local_decl.ty, |r| free_regions.contains(&r.as_var())) {
                 Either::Left(local)
             } else {
                 Either::Right(local)
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index 473c05963..9731b10aa 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -1,4 +1,4 @@
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_index::bit_set::HybridBitSet;
 use rustc_index::interval::IntervalSet;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
@@ -56,7 +56,7 @@ pub(super) fn trace<'mir, 'tcx>(
         elements,
         local_use_map,
         move_data,
-        drop_data: FxHashMap::default(),
+        drop_data: FxIndexMap::default(),
     };
 
     let mut results = LivenessResults::new(cx);
@@ -85,7 +85,7 @@ struct LivenessContext<'me, 'typeck, 'flow, 'tcx> {
     move_data: &'me MoveData<'tcx>,
 
     /// Cache for the results of `dropck_outlives` query.
-    drop_data: FxHashMap<Ty<'tcx>, DropData<'tcx>>,
+    drop_data: FxIndexMap<Ty<'tcx>, DropData<'tcx>>,
 
     /// Results of dataflow tracking which variables (and paths) have been
     /// initialized.
@@ -185,7 +185,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
     fn add_extra_drop_facts(
         &mut self,
         drop_used: Vec<(Local, Location)>,
-        relevant_live_locals: FxHashSet<Local>,
+        relevant_live_locals: FxIndexSet<Local>,
     ) {
         let locations = IntervalSet::new(self.cx.elements.num_points());
 
@@ -435,8 +435,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
         //
         // What we *actually* generate is a store to a temporary
         // for the call (`TMP = call()...`) and then a
-        // `DropAndReplace` to swap that with `X`
-        // (`DropAndReplace` has very particular semantics).
+        // `Drop(X)` followed by `X = TMP`  to swap that with `X`.
     }
 }
 
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index a49da3da6..2f10e30be 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -9,13 +9,12 @@ use either::Either;
 
 use hir::OpaqueTyOrigin;
 use rustc_data_structures::frozen::Frozen;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::vec_map::VecMap;
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::lang_items::LangItem;
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::vec::{IndexSlice, IndexVec};
 use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::region_constraints::RegionConstraintData;
@@ -36,8 +35,9 @@ use rustc_middle::ty::{
     OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt, UserType, UserTypeAnnotationIndex,
 };
 use rustc_span::def_id::CRATE_DEF_ID;
+use rustc_span::symbol::sym;
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
 use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
 use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
@@ -56,7 +56,6 @@ use crate::{
     facts::AllFacts,
     location::LocationTable,
     member_constraints::MemberConstraintSet,
-    nll::ToRegionVid,
     path_utils,
     region_infer::values::{
         LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements,
@@ -126,7 +125,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
     infcx: &BorrowckInferCtxt<'_, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body: &Body<'tcx>,
-    promoted: &IndexVec<Promoted, Body<'tcx>>,
+    promoted: &IndexSlice<Promoted, Body<'tcx>>,
     universal_regions: &Rc<UniversalRegions<'tcx>>,
     location_table: &LocationTable,
     borrow_set: &BorrowSet<'tcx>,
@@ -145,7 +144,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
         outlives_constraints: OutlivesConstraintSet::default(),
         member_constraints: MemberConstraintSet::default(),
         type_tests: Vec::default(),
-        universe_causes: FxHashMap::default(),
+        universe_causes: FxIndexMap::default(),
     };
 
     let CreateResult {
@@ -293,7 +292,7 @@ enum FieldAccessError {
 /// is a problem.
 struct TypeVerifier<'a, 'b, 'tcx> {
     cx: &'a mut TypeChecker<'b, 'tcx>,
-    promoted: &'b IndexVec<Promoted, Body<'tcx>>,
+    promoted: &'b IndexSlice<Promoted, Body<'tcx>>,
     last_span: Span,
     errors_reported: bool,
 }
@@ -494,7 +493,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
 impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
     fn new(
         cx: &'a mut TypeChecker<'b, 'tcx>,
-        promoted: &'b IndexVec<Promoted, Body<'tcx>>,
+        promoted: &'b IndexSlice<Promoted, Body<'tcx>>,
     ) -> Self {
         TypeVerifier { promoted, last_span: cx.body.span, cx, errors_reported: false }
     }
@@ -772,11 +771,14 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
 
         match context {
             PlaceContext::MutatingUse(_) => ty::Invariant,
-            PlaceContext::NonUse(StorageDead | StorageLive | VarDebugInfo) => ty::Invariant,
+            PlaceContext::NonUse(StorageDead | StorageLive | PlaceMention | VarDebugInfo) => {
+                ty::Invariant
+            }
             PlaceContext::NonMutatingUse(
-                Inspect | Copy | Move | SharedBorrow | ShallowBorrow | UniqueBorrow | AddressOf
-                | Projection,
-            ) => ty::Covariant,
+                Inspect | Copy | Move | SharedBorrow | ShallowBorrow | AddressOf | Projection
+            ) => {
+                ty::Covariant
+            },
             PlaceContext::NonUse(AscribeUserTy) => ty::Covariant,
         }
     }
@@ -785,7 +787,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         &mut self,
         parent: &dyn fmt::Debug,
         base_ty: PlaceTy<'tcx>,
-        field: Field,
+        field: FieldIdx,
         location: Location,
     ) -> Result<Ty<'tcx>, FieldAccessError> {
         let tcx = self.tcx();
@@ -811,7 +813,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             },
             PlaceTy { ty, variant_index: None } => match *ty.kind() {
                 ty::Adt(adt_def, substs) if !adt_def.is_enum() => {
-                    (adt_def.variant(VariantIdx::new(0)), substs)
+                    (adt_def.variant(FIRST_VARIANT), substs)
                 }
                 ty::Closure(_, substs) => {
                     return match substs
@@ -853,7 +855,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             },
         };
 
-        if let Some(field) = variant.fields.get(field.index()) {
+        if let Some(field) = variant.fields.get(field) {
             Ok(self.cx.normalize(field.ty(tcx, substs), location))
         } else {
             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
@@ -875,7 +877,7 @@ struct TypeChecker<'a, 'tcx> {
     user_type_annotations: &'a CanonicalUserTypeAnnotations<'tcx>,
     region_bound_pairs: &'a RegionBoundPairs<'tcx>,
     implicit_region_bound: ty::Region<'tcx>,
-    reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
+    reported_errors: FxIndexSet<(Ty<'tcx>, Span)>,
     borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
 }
 
@@ -892,7 +894,7 @@ pub(crate) struct MirTypeckResults<'tcx> {
     pub(crate) constraints: MirTypeckRegionConstraints<'tcx>,
     pub(crate) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
     pub(crate) opaque_type_values:
-        VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
+        FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
 }
 
 /// A collection of region constraints that must be satisfied for the
@@ -925,7 +927,7 @@ pub(crate) struct MirTypeckRegionConstraints<'tcx> {
 
     pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>,
 
-    pub(crate) universe_causes: FxHashMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
+    pub(crate) universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
     pub(crate) type_tests: Vec<TypeTest<'tcx>>,
 }
@@ -1178,10 +1180,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     Some(l)
-                        if matches!(
-                            body.local_decls[l].local_info,
-                            Some(box LocalInfo::AggregateTemp)
-                        ) =>
+                        if matches!(body.local_decls[l].local_info(), LocalInfo::AggregateTemp) =>
                     {
                         ConstraintCategory::Usage
                     }
@@ -1282,6 +1281,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             | StatementKind::Retag { .. }
             | StatementKind::Coverage(..)
             | StatementKind::ConstEvalCounter
+            | StatementKind::PlaceMention(..)
             | StatementKind::Nop => {}
             StatementKind::Deinit(..) | StatementKind::SetDiscriminant { .. } => {
                 bug!("Statement not allowed in this MIR phase")
@@ -1301,7 +1301,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         match &term.kind {
             TerminatorKind::Goto { .. }
             | TerminatorKind::Resume
-            | TerminatorKind::Abort
+            | TerminatorKind::Terminate
             | TerminatorKind::Return
             | TerminatorKind::GeneratorDrop
             | TerminatorKind::Unreachable
@@ -1312,24 +1312,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // no checks needed for these
             }
 
-            TerminatorKind::DropAndReplace { place, value, target: _, unwind: _ } => {
-                let place_ty = place.ty(body, tcx).ty;
-                let rv_ty = value.ty(body, tcx);
-
-                let locations = term_location.to_locations();
-                if let Err(terr) =
-                    self.sub_types(rv_ty, place_ty, locations, ConstraintCategory::Assignment)
-                {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "bad DropAndReplace ({:?} = {:?}): {:?}",
-                        place_ty,
-                        rv_ty,
-                        terr
-                    );
-                }
-            }
             TerminatorKind::SwitchInt { discr, .. } => {
                 self.check_operand(discr, term_location);
 
@@ -1357,20 +1339,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 };
                 let (sig, map) = tcx.replace_late_bound_regions(sig, |br| {
                     use crate::renumber::{BoundRegionInfo, RegionCtxt};
-                    use rustc_span::Symbol;
 
                     let region_ctxt_fn = || {
                         let reg_info = match br.kind {
-                            ty::BoundRegionKind::BrAnon(_, Some(span)) => {
-                                BoundRegionInfo::Span(span)
-                            }
-                            ty::BoundRegionKind::BrAnon(..) => {
-                                BoundRegionInfo::Name(Symbol::intern("anon"))
-                            }
+                            ty::BoundRegionKind::BrAnon(Some(span)) => BoundRegionInfo::Span(span),
+                            ty::BoundRegionKind::BrAnon(..) => BoundRegionInfo::Name(sym::anon),
                             ty::BoundRegionKind::BrNamed(_, name) => BoundRegionInfo::Name(name),
-                            ty::BoundRegionKind::BrEnv => {
-                                BoundRegionInfo::Name(Symbol::intern("env"))
-                            }
+                            ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(sym::env),
                         };
 
                         RegionCtxt::LateBound(reg_info)
@@ -1603,7 +1578,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     span_mirbug!(self, block_data, "resume on non-cleanup block!")
                 }
             }
-            TerminatorKind::Abort => {
+            TerminatorKind::Terminate => {
                 if !is_cleanup {
                     span_mirbug!(self, block_data, "abort on non-cleanup block!")
                 }
@@ -1629,26 +1604,15 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
             TerminatorKind::Unreachable => {}
             TerminatorKind::Drop { target, unwind, .. }
-            | TerminatorKind::DropAndReplace { target, unwind, .. }
-            | TerminatorKind::Assert { target, cleanup: unwind, .. } => {
+            | TerminatorKind::Assert { target, unwind, .. } => {
                 self.assert_iscleanup(body, block_data, target, is_cleanup);
-                if let Some(unwind) = unwind {
-                    if is_cleanup {
-                        span_mirbug!(self, block_data, "unwind on cleanup block")
-                    }
-                    self.assert_iscleanup(body, block_data, unwind, true);
-                }
+                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
             }
-            TerminatorKind::Call { ref target, cleanup, .. } => {
+            TerminatorKind::Call { ref target, unwind, .. } => {
                 if let &Some(target) = target {
                     self.assert_iscleanup(body, block_data, target, is_cleanup);
                 }
-                if let Some(cleanup) = cleanup {
-                    if is_cleanup {
-                        span_mirbug!(self, block_data, "cleanup on cleanup block")
-                    }
-                    self.assert_iscleanup(body, block_data, cleanup, true);
-                }
+                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
             }
             TerminatorKind::FalseEdge { real_target, imaginary_target } => {
                 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
@@ -1656,23 +1620,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
             TerminatorKind::FalseUnwind { real_target, unwind } => {
                 self.assert_iscleanup(body, block_data, real_target, is_cleanup);
-                if let Some(unwind) = unwind {
-                    if is_cleanup {
-                        span_mirbug!(self, block_data, "cleanup in cleanup block via false unwind");
-                    }
-                    self.assert_iscleanup(body, block_data, unwind, true);
-                }
+                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
             }
-            TerminatorKind::InlineAsm { destination, cleanup, .. } => {
+            TerminatorKind::InlineAsm { destination, unwind, .. } => {
                 if let Some(target) = destination {
                     self.assert_iscleanup(body, block_data, target, is_cleanup);
                 }
-                if let Some(cleanup) = cleanup {
-                    if is_cleanup {
-                        span_mirbug!(self, block_data, "cleanup on cleanup block")
-                    }
-                    self.assert_iscleanup(body, block_data, cleanup, true);
-                }
+                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
             }
         }
     }
@@ -1689,6 +1643,29 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
+    fn assert_iscleanup_unwind(
+        &mut self,
+        body: &Body<'tcx>,
+        ctxt: &dyn fmt::Debug,
+        unwind: UnwindAction,
+        is_cleanup: bool,
+    ) {
+        match unwind {
+            UnwindAction::Cleanup(unwind) => {
+                if is_cleanup {
+                    span_mirbug!(self, ctxt, "unwind on cleanup block")
+                }
+                self.assert_iscleanup(body, ctxt, unwind, true);
+            }
+            UnwindAction::Continue => {
+                if is_cleanup {
+                    span_mirbug!(self, ctxt, "unwind on cleanup block")
+                }
+            }
+            UnwindAction::Unreachable | UnwindAction::Terminate => (),
+        }
+    }
+
     fn check_local(&mut self, body: &Body<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) {
         match body.local_kind(local) {
             LocalKind::ReturnPointer | LocalKind::Arg => {
@@ -1700,7 +1677,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // - maybe we should make that a warning.
                 return;
             }
-            LocalKind::Var | LocalKind::Temp => {}
+            LocalKind::Temp => {}
         }
 
         // When `unsized_fn_params` or `unsized_locals` is enabled, only function calls
@@ -1736,7 +1713,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     fn aggregate_field_ty(
         &mut self,
         ak: &AggregateKind<'tcx>,
-        field_index: usize,
+        field_index: FieldIdx,
         location: Location,
     ) -> Result<Ty<'tcx>, FieldAccessError> {
         let tcx = self.tcx();
@@ -1753,7 +1730,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
             AggregateKind::Closure(_, substs) => {
-                match substs.as_closure().upvar_tys().nth(field_index) {
+                match substs.as_closure().upvar_tys().nth(field_index.as_usize()) {
                     Some(ty) => Ok(ty),
                     None => Err(FieldAccessError::OutOfRange {
                         field_count: substs.as_closure().upvar_tys().count(),
@@ -1764,7 +1741,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // It doesn't make sense to look at a field beyond the prefix;
                 // these require a variant index, and are not initialized in
                 // aggregate rvalues.
-                match substs.as_generator().prefix_tys().nth(field_index) {
+                match substs.as_generator().prefix_tys().nth(field_index.as_usize()) {
                     Some(ty) => Ok(ty),
                     None => Err(FieldAccessError::OutOfRange {
                         field_count: substs.as_generator().prefix_tys().count(),
@@ -2242,6 +2219,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             }
                         }
                     }
+                    CastKind::Transmute => {
+                        span_mirbug!(
+                            self,
+                            rvalue,
+                            "Unexpected CastKind::Transmute, which is not permitted in Analysis MIR",
+                        );
+                    }
                 }
             }
 
@@ -2362,7 +2346,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         body: &Body<'tcx>,
         rvalue: &Rvalue<'tcx>,
         aggregate_kind: &AggregateKind<'tcx>,
-        operands: &[Operand<'tcx>],
+        operands: &IndexSlice<FieldIdx, Operand<'tcx>>,
         location: Location,
     ) {
         let tcx = self.tcx();
@@ -2374,7 +2358,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return;
         }
 
-        for (i, operand) in operands.iter().enumerate() {
+        for (i, operand) in operands.iter_enumerated() {
             let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
                 Ok(field_ty) => field_ty,
                 Err(FieldAccessError::OutOfRange { field_count }) => {
@@ -2382,8 +2366,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         self,
                         rvalue,
                         "accessed field #{} but variant only has {}",
-                        i,
-                        field_count
+                        i.as_u32(),
+                        field_count,
                     );
                     continue;
                 }
@@ -2435,7 +2419,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         if let Some(all_facts) = all_facts {
             let _prof_timer = self.infcx.tcx.prof.generic_activity("polonius_fact_generation");
             if let Some(borrow_index) = borrow_set.get_index_of(&location) {
-                let region_vid = borrow_region.to_region_vid();
+                let region_vid = borrow_region.as_var();
                 all_facts.loan_issued_at.push((
                     region_vid,
                     borrow_index,
@@ -2481,8 +2465,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     match base_ty.kind() {
                         ty::Ref(ref_region, _, mutbl) => {
                             constraints.outlives_constraints.push(OutlivesConstraint {
-                                sup: ref_region.to_region_vid(),
-                                sub: borrow_region.to_region_vid(),
+                                sup: ref_region.as_var(),
+                                sub: borrow_region.as_var(),
                                 locations: location.to_locations(),
                                 span: location.to_locations().span(body),
                                 category,
@@ -2612,7 +2596,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self.implicit_region_bound,
                 self.param_env,
                 location.to_locations(),
-                DUMMY_SP,                   // irrelevant; will be overrided.
+                DUMMY_SP,                   // irrelevant; will be overridden.
                 ConstraintCategory::Boring, // same as above.
                 &mut self.borrowck_context.constraints,
             )
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index d96372fb9..7e6d17ec3 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -4,6 +4,7 @@ use rustc_infer::traits::PredicateObligations;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::{self, Ty};
+use rustc_span::symbol::sym;
 use rustc_span::{Span, Symbol};
 use rustc_trait_selection::traits::query::Fallible;
 
@@ -123,18 +124,17 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
             .constraints
             .placeholder_region(self.type_checker.infcx, placeholder);
 
-        let reg_info = match placeholder.name {
-            ty::BoundRegionKind::BrAnon(_, Some(span)) => BoundRegionInfo::Span(span),
-            ty::BoundRegionKind::BrAnon(..) => BoundRegionInfo::Name(Symbol::intern("anon")),
+        let reg_info = match placeholder.bound.kind {
+            ty::BoundRegionKind::BrAnon(Some(span)) => BoundRegionInfo::Span(span),
+            ty::BoundRegionKind::BrAnon(..) => BoundRegionInfo::Name(sym::anon),
             ty::BoundRegionKind::BrNamed(_, name) => BoundRegionInfo::Name(name),
-            ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(Symbol::intern("env")),
+            ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(sym::env),
         };
 
-        let reg_var =
-            reg.as_var().unwrap_or_else(|| bug!("expected region {:?} to be of kind ReVar", reg));
-        let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
-        let prev = var_to_origin.insert(reg_var, RegionCtxt::Placeholder(reg_info));
-        assert!(matches!(prev, None));
+        if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
+            let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
+            var_to_origin.insert(reg.as_var(), RegionCtxt::Placeholder(reg_info));
+        }
 
         reg
     }
@@ -146,17 +146,9 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
             universe,
         );
 
-        let reg_var =
-            reg.as_var().unwrap_or_else(|| bug!("expected region {:?} to be of kind ReVar", reg));
-
-        if cfg!(debug_assertions) {
+        if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
             let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
-            let prev = var_to_origin.insert(reg_var, RegionCtxt::Existential(None));
-
-            // It only makes sense to track region vars in non-canonicalization contexts. If this
-            // ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
-            // or modify how we track nll region vars for that map.
-            assert!(matches!(prev, None));
+            var_to_origin.insert(reg.as_var(), RegionCtxt::Existential(None));
         }
 
         reg
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index 15d7613a8..70fddb105 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -22,14 +22,12 @@ use rustc_hir::BodyOwnerKind;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{
-    self, DefIdTree, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt,
-};
+use rustc_middle::ty::{self, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt};
 use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_span::symbol::{kw, sym};
 use rustc_span::Symbol;
 use std::iter;
 
-use crate::nll::ToRegionVid;
 use crate::renumber::{BoundRegionInfo, RegionCtxt};
 use crate::BorrowckInferCtxt;
 
@@ -314,6 +312,9 @@ impl<'tcx> UniversalRegions<'tcx> {
     }
 
     /// Gets an iterator over all the early-bound regions that have names.
+    /// Iteration order may be unstable, so this should only be used when
+    /// iteration order doesn't affect anything
+    #[allow(rustc::potential_query_instability)]
     pub fn named_universal_regions<'s>(
         &'s self,
     ) -> impl Iterator<Item = (ty::Region<'tcx>, ty::RegionVid)> + 's {
@@ -403,10 +404,8 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         assert_eq!(FIRST_GLOBAL_INDEX, self.infcx.num_region_vars());
 
         // Create the "global" region that is always free in all contexts: 'static.
-        let fr_static = self
-            .infcx
-            .next_nll_region_var(FR, || RegionCtxt::Free(Symbol::intern("static")))
-            .to_region_vid();
+        let fr_static =
+            self.infcx.next_nll_region_var(FR, || RegionCtxt::Free(kw::Static)).as_var();
 
         // We've now added all the global regions. The next ones we
         // add will be external.
@@ -439,18 +438,14 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     debug!(?r);
                     if !indices.indices.contains_key(&r) {
                         let region_vid = {
-                            let name = match r.get_name() {
-                                Some(name) => name,
-                                _ => Symbol::intern("anon"),
-                            };
-
+                            let name = r.get_name_or_anon();
                             self.infcx.next_nll_region_var(FR, || {
                                 RegionCtxt::LateBound(BoundRegionInfo::Name(name))
                             })
                         };
 
                         debug!(?region_vid);
-                        indices.insert_late_bound_region(r, region_vid.to_region_vid());
+                        indices.insert_late_bound_region(r, region_vid.as_var());
                     }
                 },
             );
@@ -477,18 +472,14 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
             debug!(?r);
             if !indices.indices.contains_key(&r) {
                 let region_vid = {
-                    let name = match r.get_name() {
-                        Some(name) => name,
-                        _ => Symbol::intern("anon"),
-                    };
-
+                    let name = r.get_name_or_anon();
                     self.infcx.next_nll_region_var(FR, || {
                         RegionCtxt::LateBound(BoundRegionInfo::Name(name))
                     })
                 };
 
                 debug!(?region_vid);
-                indices.insert_late_bound_region(r, region_vid.to_region_vid());
+                indices.insert_late_bound_region(r, region_vid.as_var());
             }
         });
 
@@ -507,7 +498,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                 let reg_vid = self
                     .infcx
                     .next_nll_region_var(FR, || RegionCtxt::Free(Symbol::intern("c-variadic")))
-                    .to_region_vid();
+                    .as_var();
 
                 let region = self.infcx.tcx.mk_re_var(reg_vid);
                 let va_list_ty =
@@ -522,7 +513,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         let fr_fn_body = self
             .infcx
             .next_nll_region_var(FR, || RegionCtxt::Free(Symbol::intern("fn_body")))
-            .to_region_vid();
+            .as_var();
 
         let num_universals = self.infcx.num_region_vars();
 
@@ -643,7 +634,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
 
         let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
         let subst_mapping =
-            iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.to_region_vid()));
+            iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.as_var()));
 
         UniversalRegionIndices { indices: global_mapping.chain(subst_mapping).collect(), fr_static }
     }
@@ -767,15 +758,10 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
         self.infcx.tcx.fold_regions(value, |region, _depth| {
-            let name = match region.get_name() {
-                Some(name) => name,
-                _ => Symbol::intern("anon"),
-            };
+            let name = region.get_name_or_anon();
             debug!(?region, ?name);
 
-            let reg_var = self.next_nll_region_var(origin, || RegionCtxt::Free(name));
-
-            reg_var
+            self.next_nll_region_var(origin, || RegionCtxt::Free(name))
         })
     }
 
@@ -796,13 +782,13 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
             let region_vid = {
                 let name = match br.kind.get_name() {
                     Some(name) => name,
-                    _ => Symbol::intern("anon"),
+                    _ => sym::anon,
                 };
 
                 self.next_nll_region_var(origin, || RegionCtxt::Bound(BoundRegionInfo::Name(name)))
             };
 
-            indices.insert_late_bound_region(liberated_region, region_vid.to_region_vid());
+            indices.insert_late_bound_region(liberated_region, region_vid.as_var());
             debug!(?liberated_region, ?region_vid);
             region_vid
         });
@@ -828,18 +814,14 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
             debug!(?r);
             if !indices.indices.contains_key(&r) {
                 let region_vid = {
-                    let name = match r.get_name() {
-                        Some(name) => name,
-                        _ => Symbol::intern("anon"),
-                    };
-
+                    let name = r.get_name_or_anon();
                     self.next_nll_region_var(FR, || {
                         RegionCtxt::LateBound(BoundRegionInfo::Name(name))
                     })
                 };
 
                 debug!(?region_vid);
-                indices.insert_late_bound_region(r, region_vid.to_region_vid());
+                indices.insert_late_bound_region(r, region_vid.as_var());
             }
         });
     }
@@ -854,17 +836,13 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
             debug!(?r);
             if !indices.indices.contains_key(&r) {
                 let region_vid = {
-                    let name = match r.get_name() {
-                        Some(name) => name,
-                        _ => Symbol::intern("anon"),
-                    };
-
+                    let name = r.get_name_or_anon();
                     self.next_nll_region_var(FR, || {
                         RegionCtxt::LateBound(BoundRegionInfo::Name(name))
                     })
                 };
 
-                indices.insert_late_bound_region(r, region_vid.to_region_vid());
+                indices.insert_late_bound_region(r, region_vid.as_var());
             }
         });
     }
@@ -882,7 +860,7 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     }
 
     /// Converts `r` into a local inference variable: `r` can either
-    /// by a `ReVar` (i.e., already a reference to an inference
+    /// be a `ReVar` (i.e., already a reference to an inference
     /// variable) or it can be `'static` or some early-bound
     /// region. This is useful when taking the results from
     /// type-checking and trait-matching, which may sometimes
@@ -891,7 +869,7 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     /// fully initialized.
     pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
         if let ty::ReVar(..) = *r {
-            r.to_region_vid()
+            r.as_var()
         } else if r.is_error() {
             // We use the `'static` `RegionVid` because `ReError` doesn't actually exist in the
             // `UniversalRegionIndices`. This is fine because 1) it is a fallback only used if
diff --git a/compiler/rustc_borrowck/src/used_muts.rs b/compiler/rustc_borrowck/src/used_muts.rs
index e297b1230..c5991e0bc 100644
--- a/compiler/rustc_borrowck/src/used_muts.rs
+++ b/compiler/rustc_borrowck/src/used_muts.rs
@@ -1,6 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::{
     Local, Location, Place, Statement, StatementKind, Terminator, TerminatorKind,
@@ -26,8 +26,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     ///  See #55344 for context.
     pub(crate) fn gather_used_muts(
         &mut self,
-        temporary_used_locals: FxHashSet<Local>,
-        mut never_initialized_mut_locals: FxHashSet<Local>,
+        temporary_used_locals: FxIndexSet<Local>,
+        mut never_initialized_mut_locals: FxIndexSet<Local>,
     ) {
         {
             let mut visitor = GatherUsedMutsVisitor {
@@ -48,8 +48,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 /// MIR visitor for collecting used mutable variables.
 /// The 'visit lifetime represents the duration of the MIR walk.
 struct GatherUsedMutsVisitor<'visit, 'cx, 'tcx> {
-    temporary_used_locals: FxHashSet<Local>,
-    never_initialized_mut_locals: &'visit mut FxHashSet<Local>,
+    temporary_used_locals: FxIndexSet<Local>,
+    never_initialized_mut_locals: &'visit mut FxIndexSet<Local>,
     mbcx: &'visit mut MirBorrowckCtxt<'cx, 'tcx>,
 }
 
@@ -71,9 +71,6 @@ impl<'visit, 'cx, 'tcx> Visitor<'tcx> for GatherUsedMutsVisitor<'visit, 'cx, 'tc
             TerminatorKind::Call { destination, .. } => {
                 self.remove_never_initialized_mut_locals(*destination);
             }
-            TerminatorKind::DropAndReplace { place, .. } => {
-                self.remove_never_initialized_mut_locals(*place);
-            }
             _ => {}
         }