Auto merge of #2983 - rust-lang:rustup2023-07-16, r=oli-obk

Automatic sync from rustc

25 files changed, 233 insertions, 218 deletions

diff --git a/compiler/rustc_mir_transform/src/check_unsafety.rs b/compiler/rustc_mir_transform/src/check_unsafety.rs
index 70812761e88..58e9786ec1a 100644
--- a/compiler/rustc_mir_transform/src/check_unsafety.rs
+++ b/compiler/rustc_mir_transform/src/check_unsafety.rs
@@ -1,4 +1,4 @@
-use rustc_data_structures::unord::{UnordItems, UnordSet};
+use rustc_data_structures::unord::{ExtendUnord, UnordItems, UnordSet};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index f3ac679f97b..6437a227d47 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -14,7 +14,7 @@ use rustc_middle::mir::visit::{
 };
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::{def_id::DefId, Span, DUMMY_SP};
 use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout};
@@ -87,7 +87,7 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
             return;
         }
 
-        let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator();
+        let is_generator = tcx.type_of(def_id.to_def_id()).instantiate_identity().is_generator();
         // FIXME(welseywiser) const prop doesn't work on generators because of query cycles
         // computing their layout.
         if is_generator {
@@ -338,7 +338,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         tcx: TyCtxt<'tcx>,
     ) -> ConstPropagator<'mir, 'tcx> {
         let def_id = body.source.def_id();
-        let substs = &InternalSubsts::identity_for_item(tcx, def_id);
+        let args = &GenericArgs::identity_for_item(tcx, def_id);
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
 
         let can_const_prop = CanConstProp::check(tcx, param_env, body);
@@ -350,7 +350,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret_layout = ecx
-            .layout_of(body.bound_return_ty().subst(tcx, substs))
+            .layout_of(body.bound_return_ty().instantiate(tcx, args))
             .ok()
             // Don't bother allocating memory for large values.
             // I don't know how return types can seem to be unsized but this happens in the
@@ -366,7 +366,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             .into();
 
         ecx.push_stack_frame(
-            Instance::new(def_id, substs),
+            Instance::new(def_id, args),
             dummy_body,
             &ret,
             StackPopCleanup::Root { cleanup: false },
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index 759650fe4db..01b945afda6 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -16,7 +16,7 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{
     self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt,
 };
@@ -55,7 +55,7 @@ impl<'tcx> MirLint<'tcx> for ConstProp {
             return;
         }
 
-        let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator();
+        let is_generator = tcx.type_of(def_id.to_def_id()).instantiate_identity().is_generator();
         // FIXME(welseywiser) const prop doesn't work on generators because of query cycles
         // computing their layout.
         if is_generator {
@@ -171,7 +171,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         tcx: TyCtxt<'tcx>,
     ) -> ConstPropagator<'mir, 'tcx> {
         let def_id = body.source.def_id();
-        let substs = &InternalSubsts::identity_for_item(tcx, def_id);
+        let args = &GenericArgs::identity_for_item(tcx, def_id);
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
 
         let can_const_prop = CanConstProp::check(tcx, param_env, body);
@@ -183,7 +183,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret_layout = ecx
-            .layout_of(body.bound_return_ty().subst(tcx, substs))
+            .layout_of(body.bound_return_ty().instantiate(tcx, args))
             .ok()
             // Don't bother allocating memory for large values.
             // I don't know how return types can seem to be unsized but this happens in the
@@ -199,7 +199,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             .into();
 
         ecx.push_stack_frame(
-            Instance::new(def_id, substs),
+            Instance::new(def_id, args),
             dummy_body,
             &ret,
             StackPopCleanup::Root { cleanup: false },
diff --git a/compiler/rustc_mir_transform/src/copy_prop.rs b/compiler/rustc_mir_transform/src/copy_prop.rs
index 3df459dfa79..47d9f52bfb5 100644
--- a/compiler/rustc_mir_transform/src/copy_prop.rs
+++ b/compiler/rustc_mir_transform/src/copy_prop.rs
@@ -76,9 +76,11 @@ fn fully_moved_locals(ssa: &SsaLocals, body: &Body<'_>) -> BitSet<Local> {
     let mut fully_moved = BitSet::new_filled(body.local_decls.len());
 
     for (_, rvalue, _) in ssa.assignments(body) {
-        let (Rvalue::Use(Operand::Copy(place) | Operand::Move(place)) | Rvalue::CopyForDeref(place))
-            = rvalue
-        else { continue };
+        let (Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
+        | Rvalue::CopyForDeref(place)) = rvalue
+        else {
+            continue;
+        };
 
         let Some(rhs) = place.as_local() else { continue };
         if !ssa.is_ssa(rhs) {
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index 5b6cbb5577c..7d7588fcaec 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -281,7 +281,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
 
             let FlatSet::Elem(choice) = discr_value else {
                 // Do nothing if we don't know which branch will be taken.
-                return
+                return;
             };
 
             if target.value.map(|n| n == choice).unwrap_or(!handled) {
diff --git a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
index a133c9d4782..60ca3dfb2da 100644
--- a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
+++ b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
@@ -166,7 +166,7 @@ pub fn deduced_param_attrs<'tcx>(
 
     // Codegen won't use this information for anything if all the function parameters are passed
     // directly. Detect that and bail, for compilation speed.
-    let fn_ty = tcx.type_of(def_id).subst_identity();
+    let fn_ty = tcx.type_of(def_id).instantiate_identity();
     if matches!(fn_ty.kind(), ty::FnDef(..)) {
         if fn_ty
             .fn_sig(tcx)
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
index a31551cf619..b73b72c3192 100644
--- a/compiler/rustc_mir_transform/src/dest_prop.rs
+++ b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -218,9 +218,9 @@ impl<'tcx> MirPass<'tcx> for DestinationPropagation {
                 if merged_locals.contains(*src) {
                     continue;
                 }
-                let Some(dest) =
-                    candidates.iter().find(|dest| !merged_locals.contains(**dest)) else {
-                        continue;
+                let Some(dest) = candidates.iter().find(|dest| !merged_locals.contains(**dest))
+                else {
+                    continue;
                 };
                 if !tcx.consider_optimizing(|| {
                     format!("{} round {}", tcx.def_path_str(def_id), round_count)
@@ -601,9 +601,7 @@ impl WriteInfo {
         rhs: &Operand<'tcx>,
         body: &Body<'tcx>,
     ) {
-        let Some(rhs) = rhs.place() else {
-            return
-        };
+        let Some(rhs) = rhs.place() else { return };
         if let Some(pair) = places_to_candidate_pair(lhs, rhs, body) {
             self.skip_pair = Some(pair);
         }
diff --git a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
index 8a7b027ddda..319fb4eaf3e 100644
--- a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
+++ b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
@@ -107,9 +107,7 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
         for i in 0..body.basic_blocks.len() {
             let bbs = &*body.basic_blocks;
             let parent = BasicBlock::from_usize(i);
-            let Some(opt_data) = evaluate_candidate(tcx, body, parent) else {
-                continue
-            };
+            let Some(opt_data) = evaluate_candidate(tcx, body, parent) else { continue };
 
             if !tcx.consider_optimizing(|| format!("EarlyOtherwiseBranch {:?}", &opt_data)) {
                 break;
@@ -119,10 +117,9 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
 
             should_cleanup = true;
 
-            let TerminatorKind::SwitchInt {
-                discr: parent_op,
-                targets: parent_targets
-            } = &bbs[parent].terminator().kind else {
+            let TerminatorKind::SwitchInt { discr: parent_op, targets: parent_targets } =
+                &bbs[parent].terminator().kind
+            else {
                 unreachable!()
             };
             // Always correct since we can only switch on `Copy` types
@@ -168,7 +165,8 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
             );
 
             let eq_new_targets = parent_targets.iter().map(|(value, child)| {
-                let TerminatorKind::SwitchInt{ targets, .. } = &bbs[child].terminator().kind else {
+                let TerminatorKind::SwitchInt { targets, .. } = &bbs[child].terminator().kind
+                else {
                     unreachable!()
                 };
                 (value, targets.target_for_value(value))
@@ -311,11 +309,9 @@ fn evaluate_candidate<'tcx>(
     parent: BasicBlock,
 ) -> Option<OptimizationData<'tcx>> {
     let bbs = &body.basic_blocks;
-    let TerminatorKind::SwitchInt {
-        targets,
-        discr: parent_discr,
-    } = &bbs[parent].terminator().kind else {
-        return None
+    let TerminatorKind::SwitchInt { targets, discr: parent_discr } = &bbs[parent].terminator().kind
+    else {
+        return None;
     };
     let parent_ty = parent_discr.ty(body.local_decls(), tcx);
     let parent_dest = {
@@ -332,18 +328,16 @@ fn evaluate_candidate<'tcx>(
     };
     let (_, child) = targets.iter().next()?;
     let child_terminator = &bbs[child].terminator();
-    let TerminatorKind::SwitchInt {
-        targets: child_targets,
-        discr: child_discr,
-    } = &child_terminator.kind else {
-        return None
+    let TerminatorKind::SwitchInt { targets: child_targets, discr: child_discr } =
+        &child_terminator.kind
+    else {
+        return None;
     };
     let child_ty = child_discr.ty(body.local_decls(), tcx);
     if child_ty != parent_ty {
         return None;
     }
-    let Some(StatementKind::Assign(boxed))
-        = &bbs[child].statements.first().map(|x| &x.kind) else {
+    let Some(StatementKind::Assign(boxed)) = &bbs[child].statements.first().map(|x| &x.kind) else {
         return None;
     };
     let (_, Rvalue::Discriminant(child_place)) = &**boxed else {
@@ -383,12 +377,8 @@ fn verify_candidate_branch<'tcx>(
         return false;
     }
     // ...assign the discriminant of `place` in that statement
-    let StatementKind::Assign(boxed) = &branch.statements[0].kind else {
-        return false
-    };
-    let (discr_place, Rvalue::Discriminant(from_place)) = &**boxed else {
-        return false
-    };
+    let StatementKind::Assign(boxed) = &branch.statements[0].kind else { return false };
+    let (discr_place, Rvalue::Discriminant(from_place)) = &**boxed else { return false };
     if *from_place != place {
         return false;
     }
@@ -397,8 +387,9 @@ fn verify_candidate_branch<'tcx>(
         return false;
     }
     // ...terminate on a `SwitchInt` that invalidates that local
-    let TerminatorKind::SwitchInt{ discr: switch_op, targets, .. } = &branch.terminator().kind else {
-        return false
+    let TerminatorKind::SwitchInt { discr: switch_op, targets, .. } = &branch.terminator().kind
+    else {
+        return false;
     };
     if *switch_op != Operand::Move(*discr_place) {
         return false;
diff --git a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
index cc0d7d51b60..e51f771e00d 100644
--- a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
@@ -18,9 +18,9 @@ pub fn build_ptr_tys<'tcx>(
     unique_did: DefId,
     nonnull_did: DefId,
 ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
-    let substs = tcx.mk_substs(&[pointee.into()]);
-    let unique_ty = tcx.type_of(unique_did).subst(tcx, substs);
-    let nonnull_ty = tcx.type_of(nonnull_did).subst(tcx, substs);
+    let args = tcx.mk_args(&[pointee.into()]);
+    let unique_ty = tcx.type_of(unique_did).instantiate(tcx, args);
+    let nonnull_ty = tcx.type_of(nonnull_did).instantiate(tcx, args);
     let ptr_ty = Ty::new_imm_ptr(tcx, pointee);
 
     (unique_ty, nonnull_ty, ptr_ty)
@@ -95,7 +95,8 @@ impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
             let unique_did =
                 tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::from_u32(0)].did;
 
-            let Some(nonnull_def) = tcx.type_of(unique_did).subst_identity().ty_adt_def() else {
+            let Some(nonnull_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def()
+            else {
                 span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
             };
 
diff --git a/compiler/rustc_mir_transform/src/function_item_references.rs b/compiler/rustc_mir_transform/src/function_item_references.rs
index 0b41e57be3b..fdf6ab33c82 100644
--- a/compiler/rustc_mir_transform/src/function_item_references.rs
+++ b/compiler/rustc_mir_transform/src/function_item_references.rs
@@ -2,7 +2,7 @@ use itertools::Itertools;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, EarlyBinder, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt};
 use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
 use rustc_span::{symbol::sym, Span};
 use rustc_target::spec::abi::Abi;
@@ -40,20 +40,19 @@ impl<'tcx> Visitor<'tcx> for FunctionItemRefChecker<'_, 'tcx> {
         {
             let source_info = *self.body.source_info(location);
             let func_ty = func.ty(self.body, self.tcx);
-            if let ty::FnDef(def_id, substs_ref) = *func_ty.kind() {
+            if let ty::FnDef(def_id, args_ref) = *func_ty.kind() {
                 // Handle calls to `transmute`
                 if self.tcx.is_diagnostic_item(sym::transmute, def_id) {
                     let arg_ty = args[0].ty(self.body, self.tcx);
                     for inner_ty in arg_ty.walk().filter_map(|arg| arg.as_type()) {
-                        if let Some((fn_id, fn_substs)) =
-                            FunctionItemRefChecker::is_fn_ref(inner_ty)
+                        if let Some((fn_id, fn_args)) = FunctionItemRefChecker::is_fn_ref(inner_ty)
                         {
                             let span = self.nth_arg_span(&args, 0);
-                            self.emit_lint(fn_id, fn_substs, source_info, span);
+                            self.emit_lint(fn_id, fn_args, source_info, span);
                         }
                     }
                 } else {
-                    self.check_bound_args(def_id, substs_ref, &args, source_info);
+                    self.check_bound_args(def_id, args_ref, &args, source_info);
                 }
             }
         }
@@ -63,11 +62,11 @@ impl<'tcx> Visitor<'tcx> for FunctionItemRefChecker<'_, 'tcx> {
 
 impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     /// Emits a lint for function reference arguments bound by `fmt::Pointer` in calls to the
-    /// function defined by `def_id` with the substitutions `substs_ref`.
+    /// function defined by `def_id` with the substitutions `args_ref`.
     fn check_bound_args(
         &self,
         def_id: DefId,
-        substs_ref: SubstsRef<'tcx>,
+        args_ref: GenericArgsRef<'tcx>,
         args: &[Operand<'tcx>],
         source_info: SourceInfo,
     ) {
@@ -76,15 +75,17 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
         for bound in bounds {
             if let Some(bound_ty) = self.is_pointer_trait(bound) {
                 // Get the argument types as they appear in the function signature.
-                let arg_defs = self.tcx.fn_sig(def_id).subst_identity().skip_binder().inputs();
+                let arg_defs =
+                    self.tcx.fn_sig(def_id).instantiate_identity().skip_binder().inputs();
                 for (arg_num, arg_def) in arg_defs.iter().enumerate() {
                     // For all types reachable from the argument type in the fn sig
                     for inner_ty in arg_def.walk().filter_map(|arg| arg.as_type()) {
                         // If the inner type matches the type bound by `Pointer`
                         if inner_ty == bound_ty {
                             // Do a substitution using the parameters from the callsite
-                            let subst_ty = EarlyBinder::bind(inner_ty).subst(self.tcx, substs_ref);
-                            if let Some((fn_id, fn_substs)) =
+                            let subst_ty =
+                                EarlyBinder::bind(inner_ty).instantiate(self.tcx, args_ref);
+                            if let Some((fn_id, fn_args)) =
                                 FunctionItemRefChecker::is_fn_ref(subst_ty)
                             {
                                 let mut span = self.nth_arg_span(args, arg_num);
@@ -94,7 +95,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
                                     let callsite_ctxt = span.source_callsite().ctxt();
                                     span = span.with_ctxt(callsite_ctxt);
                                 }
-                                self.emit_lint(fn_id, fn_substs, source_info, span);
+                                self.emit_lint(fn_id, fn_args, source_info, span);
                             }
                         }
                     }
@@ -115,8 +116,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     }
 
     /// If a type is a reference or raw pointer to the anonymous type of a function definition,
-    /// returns that function's `DefId` and `SubstsRef`.
-    fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, SubstsRef<'tcx>)> {
+    /// returns that function's `DefId` and `GenericArgsRef`.
+    fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, GenericArgsRef<'tcx>)> {
         let referent_ty = match ty.kind() {
             ty::Ref(_, referent_ty, _) => Some(referent_ty),
             ty::RawPtr(ty_and_mut) => Some(&ty_and_mut.ty),
@@ -124,8 +125,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
         };
         referent_ty
             .map(|ref_ty| {
-                if let ty::FnDef(def_id, substs_ref) = *ref_ty.kind() {
-                    Some((def_id, substs_ref))
+                if let ty::FnDef(def_id, args_ref) = *ref_ty.kind() {
+                    Some((def_id, args_ref))
                 } else {
                     None
                 }
@@ -145,7 +146,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     fn emit_lint(
         &self,
         fn_id: DefId,
-        fn_substs: SubstsRef<'tcx>,
+        fn_args: GenericArgsRef<'tcx>,
         source_info: SourceInfo,
         span: Span,
     ) {
@@ -155,7 +156,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
             .assert_crate_local()
             .lint_root;
         // FIXME: use existing printing routines to print the function signature
-        let fn_sig = self.tcx.fn_sig(fn_id).subst(self.tcx, fn_substs);
+        let fn_sig = self.tcx.fn_sig(fn_id).instantiate(self.tcx, fn_args);
         let unsafety = fn_sig.unsafety().prefix_str();
         let abi = match fn_sig.abi() {
             Abi::Rust => String::from(""),
@@ -167,8 +168,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
             }
         };
         let ident = self.tcx.item_name(fn_id).to_ident_string();
-        let ty_params = fn_substs.types().map(|ty| format!("{}", ty));
-        let const_params = fn_substs.consts().map(|c| format!("{}", c));
+        let ty_params = fn_args.types().map(|ty| format!("{}", ty));
+        let const_params = fn_args.consts().map(|c| format!("{}", c));
         let params = ty_params.chain(const_params).join(", ");
         let num_args = fn_sig.inputs().map_bound(|inputs| inputs.len()).skip_binder();
         let variadic = if fn_sig.c_variadic() { ", ..." } else { "" };
diff --git a/compiler/rustc_mir_transform/src/generator.rs b/compiler/rustc_mir_transform/src/generator.rs
index 264bc61f1b3..eaeaff69cf3 100644
--- a/compiler/rustc_mir_transform/src/generator.rs
+++ b/compiler/rustc_mir_transform/src/generator.rs
@@ -65,7 +65,7 @@ use rustc_middle::mir::dump_mir;
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
-use rustc_middle::ty::{GeneratorSubsts, SubstsRef};
+use rustc_middle::ty::{GeneratorArgs, GenericArgsRef};
 use rustc_mir_dataflow::impls::{
     MaybeBorrowedLocals, MaybeLiveLocals, MaybeRequiresStorage, MaybeStorageLive,
 };
@@ -194,11 +194,11 @@ fn replace_base<'tcx>(place: &mut Place<'tcx>, new_base: Place<'tcx>, tcx: TyCtx
 const SELF_ARG: Local = Local::from_u32(1);
 
 /// Generator has not been resumed yet.
-const UNRESUMED: usize = GeneratorSubsts::UNRESUMED;
+const UNRESUMED: usize = GeneratorArgs::UNRESUMED;
 /// Generator has returned / is completed.
-const RETURNED: usize = GeneratorSubsts::RETURNED;
+const RETURNED: usize = GeneratorArgs::RETURNED;
 /// Generator has panicked and is poisoned.
-const POISONED: usize = GeneratorSubsts::POISONED;
+const POISONED: usize = GeneratorArgs::POISONED;
 
 /// Number of variants to reserve in generator state. Corresponds to
 /// `UNRESUMED` (beginning of a generator) and `RETURNED`/`POISONED`
@@ -223,7 +223,7 @@ struct TransformVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     is_async_kind: bool,
     state_adt_ref: AdtDef<'tcx>,
-    state_substs: SubstsRef<'tcx>,
+    state_args: GenericArgsRef<'tcx>,
 
     // The type of the discriminant in the generator struct
     discr_ty: Ty<'tcx>,
@@ -265,7 +265,7 @@ impl<'tcx> TransformVisitor<'tcx> {
             (false, true) => 1,  // Poll::Pending
         });
 
-        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_substs, None, None);
+        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
 
         // `Poll::Pending`
         if self.is_async_kind && idx == VariantIdx::new(1) {
@@ -431,8 +431,8 @@ fn make_generator_state_argument_pinned<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body
 
     let pin_did = tcx.require_lang_item(LangItem::Pin, Some(body.span));
     let pin_adt_ref = tcx.adt_def(pin_did);
-    let substs = tcx.mk_substs(&[ref_gen_ty.into()]);
-    let pin_ref_gen_ty = Ty::new_adt(tcx, pin_adt_ref, substs);
+    let args = tcx.mk_args(&[ref_gen_ty.into()]);
+    let pin_ref_gen_ty = Ty::new_adt(tcx, pin_adt_ref, args);
 
     // Replace the by ref generator argument
     body.local_decls.raw[1].ty = pin_ref_gen_ty;
@@ -1431,7 +1431,7 @@ pub(crate) fn mir_generator_witnesses<'tcx>(
     // The first argument is the generator type passed by value
     let gen_ty = body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty;
 
-    // Get the interior types and substs which typeck computed
+    // Get the interior types and args which typeck computed
     let movable = match *gen_ty.kind() {
         ty::Generator(_, _, movability) => movability == hir::Movability::Movable,
         ty::Error(_) => return None,
@@ -1465,14 +1465,14 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         // The first argument is the generator type passed by value
         let gen_ty = body.local_decls.raw[1].ty;
 
-        // Get the discriminant type and substs which typeck computed
+        // Get the discriminant type and args which typeck computed
         let (discr_ty, upvars, interior, movable) = match *gen_ty.kind() {
-            ty::Generator(_, substs, movability) => {
-                let substs = substs.as_generator();
+            ty::Generator(_, args, movability) => {
+                let args = args.as_generator();
                 (
-                    substs.discr_ty(tcx),
-                    substs.upvar_tys().collect::<Vec<_>>(),
-                    substs.witness(),
+                    args.discr_ty(tcx),
+                    args.upvar_tys().collect::<Vec<_>>(),
+                    args.witness(),
                     movability == hir::Movability::Movable,
                 )
             }
@@ -1483,20 +1483,20 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         };
 
         let is_async_kind = matches!(body.generator_kind(), Some(GeneratorKind::Async(_)));
-        let (state_adt_ref, state_substs) = if is_async_kind {
+        let (state_adt_ref, state_args) = if is_async_kind {
             // Compute Poll<return_ty>
             let poll_did = tcx.require_lang_item(LangItem::Poll, None);
             let poll_adt_ref = tcx.adt_def(poll_did);
-            let poll_substs = tcx.mk_substs(&[body.return_ty().into()]);
-            (poll_adt_ref, poll_substs)
+            let poll_args = tcx.mk_args(&[body.return_ty().into()]);
+            (poll_adt_ref, poll_args)
         } else {
             // Compute GeneratorState<yield_ty, return_ty>
             let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
             let state_adt_ref = tcx.adt_def(state_did);
-            let state_substs = tcx.mk_substs(&[yield_ty.into(), body.return_ty().into()]);
-            (state_adt_ref, state_substs)
+            let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
+            (state_adt_ref, state_args)
         };
-        let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_substs);
+        let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args);
 
         // We rename RETURN_PLACE which has type mir.return_ty to new_ret_local
         // RETURN_PLACE then is a fresh unused local with type ret_ty.
@@ -1570,7 +1570,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
             tcx,
             is_async_kind,
             state_adt_ref,
-            state_substs,
+            state_args,
             remap,
             storage_liveness,
             always_live_locals,
@@ -1763,7 +1763,9 @@ fn check_suspend_tys<'tcx>(tcx: TyCtxt<'tcx>, layout: &GeneratorLayout<'tcx>, bo
             debug!(?decl);
 
             if !decl.ignore_for_traits && linted_tys.insert(decl.ty) {
-                let Some(hir_id) = decl.source_info.scope.lint_root(&body.source_scopes) else { continue };
+                let Some(hir_id) = decl.source_info.scope.lint_root(&body.source_scopes) else {
+                    continue;
+                };
 
                 check_must_not_suspend_ty(
                     tcx,
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 240beabfc1a..7860cf76247 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -105,7 +105,7 @@ struct Inliner<'tcx> {
     /// Caller codegen attributes.
     codegen_fn_attrs: &'tcx CodegenFnAttrs,
     /// Stack of inlined instances.
-    /// We only check the `DefId` and not the substs because we want to
+    /// We only check the `DefId` and not the args because we want to
     /// avoid inlining cases of polymorphic recursion.
     /// The number of `DefId`s is finite, so checking history is enough
     /// to ensure that we do not loop endlessly while inlining.
@@ -329,11 +329,11 @@ impl<'tcx> Inliner<'tcx> {
         let terminator = bb_data.terminator();
         if let TerminatorKind::Call { ref func, target, fn_span, .. } = terminator.kind {
             let func_ty = func.ty(caller_body, self.tcx);
-            if let ty::FnDef(def_id, substs) = *func_ty.kind() {
-                // To resolve an instance its substs have to be fully normalized.
-                let substs = self.tcx.try_normalize_erasing_regions(self.param_env, substs).ok()?;
+            if let ty::FnDef(def_id, args) = *func_ty.kind() {
+                // To resolve an instance its args have to be fully normalized.
+                let args = self.tcx.try_normalize_erasing_regions(self.param_env, args).ok()?;
                 let callee =
-                    Instance::resolve(self.tcx, self.param_env, def_id, substs).ok().flatten()?;
+                    Instance::resolve(self.tcx, self.param_env, def_id, args).ok().flatten()?;
 
                 if let InstanceDef::Virtual(..) | InstanceDef::Intrinsic(_) = callee.def {
                     return None;
@@ -343,7 +343,7 @@ impl<'tcx> Inliner<'tcx> {
                     return None;
                 }
 
-                let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, substs);
+                let fn_sig = self.tcx.fn_sig(def_id).instantiate(self.tcx, args);
                 let source_info = SourceInfo { span: fn_span, ..terminator.source_info };
 
                 return Some(CallSite { callee, fn_sig, block: bb, target, source_info });
@@ -368,7 +368,7 @@ impl<'tcx> Inliner<'tcx> {
         // inlining. This is to ensure that the final crate doesn't have MIR that
         // reference unexported symbols
         if callsite.callee.def_id().is_local() {
-            let is_generic = callsite.callee.substs.non_erasable_generics().next().is_some();
+            let is_generic = callsite.callee.args.non_erasable_generics().next().is_some();
             if !is_generic && !callee_attrs.requests_inline() {
                 return Err("not exported");
             }
@@ -855,8 +855,8 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
             };
 
             let kind = match parent_ty.ty.kind() {
-                &ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                    self.tcx.type_of(def_id).subst(self.tcx, substs).kind()
+                &ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                    self.tcx.type_of(def_id).instantiate(self.tcx, args).kind()
                 }
                 kind => kind,
             };
@@ -869,23 +869,23 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                     };
                     check_equal(self, *f_ty);
                 }
-                ty::Adt(adt_def, substs) => {
+                ty::Adt(adt_def, args) => {
                     let var = parent_ty.variant_index.unwrap_or(FIRST_VARIANT);
                     let Some(field) = adt_def.variant(var).fields.get(f) else {
                         self.validation = Err("malformed MIR");
                         return;
                     };
-                    check_equal(self, field.ty(self.tcx, substs));
+                    check_equal(self, field.ty(self.tcx, args));
                 }
-                ty::Closure(_, substs) => {
-                    let substs = substs.as_closure();
-                    let Some(f_ty) = substs.upvar_tys().nth(f.as_usize()) else {
+                ty::Closure(_, args) => {
+                    let args = args.as_closure();
+                    let Some(f_ty) = args.upvar_tys().nth(f.as_usize()) else {
                         self.validation = Err("malformed MIR");
                         return;
                     };
                     check_equal(self, f_ty);
                 }
-                &ty::Generator(def_id, substs, _) => {
+                &ty::Generator(def_id, args, _) => {
                     let f_ty = if let Some(var) = parent_ty.variant_index {
                         let gen_body = if def_id == self.callee_body.source.def_id() {
                             self.callee_body
@@ -910,7 +910,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
 
                         f_ty.ty
                     } else {
-                        let Some(f_ty) = substs.as_generator().prefix_tys().nth(f.index()) else {
+                        let Some(f_ty) = args.as_generator().prefix_tys().nth(f.index()) else {
                             self.validation = Err("malformed MIR");
                             return;
                         };
@@ -1130,10 +1130,10 @@ fn try_instance_mir<'tcx>(
 ) -> Result<&'tcx Body<'tcx>, &'static str> {
     match instance {
         ty::InstanceDef::DropGlue(_, Some(ty)) => match ty.kind() {
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 let fields = def.all_fields();
                 for field in fields {
-                    let field_ty = field.ty(tcx, substs);
+                    let field_ty = field.ty(tcx, args);
                     if field_ty.has_param() && field_ty.has_projections() {
                         return Err("cannot build drop shim for polymorphic type");
                     }
diff --git a/compiler/rustc_mir_transform/src/inline/cycle.rs b/compiler/rustc_mir_transform/src/inline/cycle.rs
index 8a10445f837..822634129fc 100644
--- a/compiler/rustc_mir_transform/src/inline/cycle.rs
+++ b/compiler/rustc_mir_transform/src/inline/cycle.rs
@@ -3,7 +3,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::mir::TerminatorKind;
 use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::{self, subst::SubstsRef, InstanceDef, TyCtxt};
+use rustc_middle::ty::{self, GenericArgsRef, InstanceDef, TyCtxt};
 use rustc_session::Limit;
 
 // FIXME: check whether it is cheaper to precompute the entire call graph instead of invoking
@@ -43,16 +43,16 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
         recursion_limit: Limit,
     ) -> bool {
         trace!(%caller);
-        for &(callee, substs) in tcx.mir_inliner_callees(caller.def) {
-            let Ok(substs) = caller.try_subst_mir_and_normalize_erasing_regions(
+        for &(callee, args) in tcx.mir_inliner_callees(caller.def) {
+            let Ok(args) = caller.try_subst_mir_and_normalize_erasing_regions(
                 tcx,
                 param_env,
-                ty::EarlyBinder::bind(substs),
+                ty::EarlyBinder::bind(args),
             ) else {
-                trace!(?caller, ?param_env, ?substs, "cannot normalize, skipping");
+                trace!(?caller, ?param_env, ?args, "cannot normalize, skipping");
                 continue;
             };
-            let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, substs) else {
+            let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, args) else {
                 trace!(?callee, "cannot resolve, skipping");
                 continue;
             };
@@ -147,7 +147,7 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
 pub(crate) fn mir_inliner_callees<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance: ty::InstanceDef<'tcx>,
-) -> &'tcx [(DefId, SubstsRef<'tcx>)] {
+) -> &'tcx [(DefId, GenericArgsRef<'tcx>)] {
     let steal;
     let guard;
     let body = match (instance, instance.def_id().as_local()) {
@@ -165,7 +165,7 @@ pub(crate) fn mir_inliner_callees<'tcx>(
         if let TerminatorKind::Call { func, .. } = &terminator.kind {
             let ty = func.ty(&body.local_decls, tcx);
             let call = match ty.kind() {
-                ty::FnDef(def_id, substs) => (*def_id, *substs),
+                ty::FnDef(def_id, args) => (*def_id, *args),
                 _ => continue,
             };
             calls.insert(call);
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index e4dc617620e..a430f8da35c 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -5,7 +5,7 @@ use crate::MirPass;
 use rustc_hir::Mutability;
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::ValidityRequirement;
-use rustc_middle::ty::{self, ParamEnv, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, GenericArgsRef, ParamEnv, Ty, TyCtxt};
 use rustc_span::symbol::Symbol;
 use rustc_target::abi::FieldIdx;
 
@@ -163,14 +163,14 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
                 }
 
                 // Transmuting a transparent struct/union to a field's type is a projection
-                if let ty::Adt(adt_def, substs) = operand_ty.kind()
+                if let ty::Adt(adt_def, args) = operand_ty.kind()
                     && adt_def.repr().transparent()
                     && (adt_def.is_struct() || adt_def.is_union())
                     && let Some(place) = operand.place()
                 {
                     let variant = adt_def.non_enum_variant();
                     for (i, field) in variant.fields.iter().enumerate() {
-                        let field_ty = field.ty(self.tcx, substs);
+                        let field_ty = field.ty(self.tcx, args);
                         if field_ty == *cast_ty {
                             let place = place.project_deeper(&[ProjectionElem::Field(FieldIdx::from_usize(i), *cast_ty)], self.tcx);
                             let operand = if operand.is_move() { Operand::Move(place) } else { Operand::Copy(place) };
@@ -189,22 +189,22 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         statements: &mut Vec<Statement<'tcx>>,
     ) {
         let TerminatorKind::Call { func, args, destination, target, .. } = &mut terminator.kind
-        else { return };
+        else {
+            return;
+        };
 
         // It's definitely not a clone if there are multiple arguments
         if args.len() != 1 {
             return;
         }
 
-        let Some(destination_block) = *target
-        else { return };
+        let Some(destination_block) = *target else { return };
 
         // Only bother looking more if it's easy to know what we're calling
-        let Some((fn_def_id, fn_substs)) = func.const_fn_def()
-        else { return };
+        let Some((fn_def_id, fn_args)) = func.const_fn_def() else { return };
 
         // Clone needs one subst, so we can cheaply rule out other stuff
-        if fn_substs.len() != 1 {
+        if fn_args.len() != 1 {
             return;
         }
 
@@ -212,8 +212,7 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         // doing DefId lookups to figure out what we're actually calling.
         let arg_ty = args[0].ty(self.local_decls, self.tcx);
 
-        let ty::Ref(_region, inner_ty, Mutability::Not) = *arg_ty.kind()
-        else { return };
+        let ty::Ref(_region, inner_ty, Mutability::Not) = *arg_ty.kind() else { return };
 
         if !inner_ty.is_trivially_pure_clone_copy() {
             return;
@@ -227,15 +226,14 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         if !self.tcx.consider_optimizing(|| {
             format!(
                 "InstSimplify - Call: {:?} SourceInfo: {:?}",
-                (fn_def_id, fn_substs),
+                (fn_def_id, fn_args),
                 terminator.source_info
             )
         }) {
             return;
         }
 
-        let Some(arg_place) = args.pop().unwrap().place()
-        else { return };
+        let Some(arg_place) = args.pop().unwrap().place() else { return };
 
         statements.push(Statement {
             source_info: terminator.source_info,
@@ -254,17 +252,21 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         terminator: &mut Terminator<'tcx>,
         _statements: &mut Vec<Statement<'tcx>>,
     ) {
-        let TerminatorKind::Call { func, target, .. } = &mut terminator.kind  else { return; };
-        let Some(target_block) = target else { return; };
+        let TerminatorKind::Call { func, target, .. } = &mut terminator.kind else {
+            return;
+        };
+        let Some(target_block) = target else {
+            return;
+        };
         let func_ty = func.ty(self.local_decls, self.tcx);
-        let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(self.tcx, func_ty) else {
+        let Some((intrinsic_name, args)) = resolve_rust_intrinsic(self.tcx, func_ty) else {
             return;
         };
         // The intrinsics we are interested in have one generic parameter
-        if substs.is_empty() {
+        if args.is_empty() {
             return;
         }
-        let ty = substs.type_at(0);
+        let ty = args.type_at(0);
 
         let known_is_valid = intrinsic_assert_panics(self.tcx, self.param_env, ty, intrinsic_name);
         match known_is_valid {
@@ -295,10 +297,10 @@ fn intrinsic_assert_panics<'tcx>(
 fn resolve_rust_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     func_ty: Ty<'tcx>,
-) -> Option<(Symbol, SubstsRef<'tcx>)> {
-    if let ty::FnDef(def_id, substs) = *func_ty.kind() {
+) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
+    if let ty::FnDef(def_id, args) = *func_ty.kind() {
         if tcx.is_intrinsic(def_id) {
-            return Some((tcx.item_name(def_id), substs));
+            return Some((tcx.item_name(def_id), args));
         }
     }
     None
diff --git a/compiler/rustc_mir_transform/src/large_enums.rs b/compiler/rustc_mir_transform/src/large_enums.rs
index 8ed4706e172..19108dabdf4 100644
--- a/compiler/rustc_mir_transform/src/large_enums.rs
+++ b/compiler/rustc_mir_transform/src/large_enums.rs
@@ -48,7 +48,7 @@ impl EnumSizeOpt {
         alloc_cache: &mut FxHashMap<Ty<'tcx>, AllocId>,
     ) -> Option<(AdtDef<'tcx>, usize, AllocId)> {
         let adt_def = match ty.kind() {
-            ty::Adt(adt_def, _substs) if adt_def.is_enum() => adt_def,
+            ty::Adt(adt_def, _args) if adt_def.is_enum() => adt_def,
             _ => return None,
         };
         let layout = tcx.layout_of(param_env.and(ty)).ok()?;
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index fa8257cf984..d419329f2d6 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -553,6 +553,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
             &const_goto::ConstGoto,
             &remove_unneeded_drops::RemoveUnneededDrops,
+            &ref_prop::ReferencePropagation,
             &sroa::ScalarReplacementOfAggregates,
             &match_branches::MatchBranchSimplification,
             // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
@@ -560,7 +561,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &instsimplify::InstSimplify,
             &simplify::SimplifyLocals::BeforeConstProp,
             &copy_prop::CopyProp,
-            &ref_prop::ReferencePropagation,
             // Perform `SeparateConstSwitch` after SSA-based analyses, as cloning blocks may
             // destroy the SSA property. It should still happen before const-propagation, so the
             // latter pass will leverage the created opportunities.
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index ce98e9b0c84..d1ecfe9f851 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -2,7 +2,7 @@
 
 use crate::{errors, MirPass};
 use rustc_middle::mir::*;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
@@ -19,7 +19,8 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                 &mut terminator.kind
             {
                 let func_ty = func.ty(local_decls, tcx);
-                let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(tcx, func_ty) else {
+                let Some((intrinsic_name, generic_args)) = resolve_rust_intrinsic(tcx, func_ty)
+                else {
                     continue;
                 };
                 match intrinsic_name {
@@ -149,7 +150,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::size_of | sym::min_align_of => {
                         if let Some(target) = *target {
-                            let tp_ty = substs.type_at(0);
+                            let tp_ty = generic_args.type_at(0);
                             let null_op = match intrinsic_name {
                                 sym::size_of => NullOp::SizeOf,
                                 sym::min_align_of => NullOp::AlignOf,
@@ -251,7 +252,9 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                         if let (Some(target), Some(arg)) = (*target, args[0].place()) {
                             let ty::RawPtr(ty::TypeAndMut { ty: dest_ty, .. }) =
                                 destination.ty(local_decls, tcx).ty.kind()
-                            else { bug!(); };
+                            else {
+                                bug!();
+                            };
 
                             block.statements.push(Statement {
                                 source_info: terminator.source_info,
@@ -315,10 +318,10 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
 fn resolve_rust_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     func_ty: Ty<'tcx>,
-) -> Option<(Symbol, SubstsRef<'tcx>)> {
-    if let ty::FnDef(def_id, substs) = *func_ty.kind() {
+) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
+    if let ty::FnDef(def_id, args) = *func_ty.kind() {
         if tcx.is_intrinsic(def_id) {
-            return Some((tcx.item_name(def_id), substs));
+            return Some((tcx.item_name(def_id), args));
         }
     }
     None
diff --git a/compiler/rustc_mir_transform/src/ref_prop.rs b/compiler/rustc_mir_transform/src/ref_prop.rs
index bbd9f76ba5c..c17c791f9c3 100644
--- a/compiler/rustc_mir_transform/src/ref_prop.rs
+++ b/compiler/rustc_mir_transform/src/ref_prop.rs
@@ -71,7 +71,7 @@ pub struct ReferencePropagation;
 
 impl<'tcx> MirPass<'tcx> for ReferencePropagation {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 4
+        sess.mir_opt_level() >= 2
     }
 
     #[instrument(level = "trace", skip(self, tcx, body))]
@@ -355,7 +355,10 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
     }
 
     fn visit_var_debug_info(&mut self, debuginfo: &mut VarDebugInfo<'tcx>) {
-        if let VarDebugInfoContents::Place(ref mut place) = debuginfo.value
+        // If the debuginfo is a pointer to another place:
+        // - if it's a reborrow, see through it;
+        // - if it's a direct borrow, increase `debuginfo.references`.
+        while let VarDebugInfoContents::Place(ref mut place) = debuginfo.value
             && place.projection.is_empty()
             && let Value::Pointer(target, _) = self.targets[place.local]
             && target.projection.iter().all(|p| p.can_use_in_debuginfo())
@@ -369,28 +372,37 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
                 debuginfo.references = references;
                 *place = target;
                 self.any_replacement = true;
+            } else {
+                break
             }
         }
+
+        // Simplify eventual projections left inside `debuginfo`.
+        self.super_var_debug_info(debuginfo);
     }
 
     fn visit_place(&mut self, place: &mut Place<'tcx>, ctxt: PlaceContext, loc: Location) {
-        if place.projection.first() != Some(&PlaceElem::Deref) {
-            return;
-        }
-
         loop {
-            if let Value::Pointer(target, _) = self.targets[place.local] {
-                let perform_opt = matches!(ctxt, PlaceContext::NonUse(_))
-                    || self.allowed_replacements.contains(&(target.local, loc));
-
-                if perform_opt {
-                    *place = target.project_deeper(&place.projection[1..], self.tcx);
-                    self.any_replacement = true;
-                    continue;
+            if place.projection.first() != Some(&PlaceElem::Deref) {
+                return;
+            }
+
+            let Value::Pointer(target, _) = self.targets[place.local] else { return };
+
+            let perform_opt = match ctxt {
+                PlaceContext::NonUse(NonUseContext::VarDebugInfo) => {
+                    target.projection.iter().all(|p| p.can_use_in_debuginfo())
                 }
+                PlaceContext::NonUse(_) => true,
+                _ => self.allowed_replacements.contains(&(target.local, loc)),
+            };
+
+            if !perform_opt {
+                return;
             }
 
-            break;
+            *place = target.project_deeper(&place.projection[1..], self.tcx);
+            self.any_replacement = true;
         }
     }
 
diff --git a/compiler/rustc_mir_transform/src/remove_uninit_drops.rs b/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
index 283931de043..6f9edd07d73 100644
--- a/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
+++ b/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
@@ -1,6 +1,6 @@
 use rustc_index::bit_set::ChunkedBitSet;
 use rustc_middle::mir::{Body, TerminatorKind};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, VariantDef};
 use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
 use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
@@ -38,8 +38,7 @@ impl<'tcx> MirPass<'tcx> for RemoveUninitDrops {
         let mut to_remove = vec![];
         for (bb, block) in body.basic_blocks.iter_enumerated() {
             let terminator = block.terminator();
-            let TerminatorKind::Drop { place, .. } = &terminator.kind
-            else { continue };
+            let TerminatorKind::Drop { place, .. } = &terminator.kind else { continue };
 
             maybe_inits.seek_before_primary_effect(body.terminator_loc(bb));
 
@@ -64,9 +63,9 @@ impl<'tcx> MirPass<'tcx> for RemoveUninitDrops {
         for bb in to_remove {
             let block = &mut body.basic_blocks_mut()[bb];
 
-            let TerminatorKind::Drop { target, .. }
-                = &block.terminator().kind
-            else { unreachable!() };
+            let TerminatorKind::Drop { target, .. } = &block.terminator().kind else {
+                unreachable!()
+            };
 
             // Replace block terminator with `Goto`.
             block.terminator_mut().kind = TerminatorKind::Goto { target: *target };
@@ -99,7 +98,7 @@ fn is_needs_drop_and_init<'tcx>(
     // This pass is only needed for const-checking, so it doesn't handle as many cases as
     // `DropCtxt::open_drop`, since they aren't relevant in a const-context.
     match ty.kind() {
-        ty::Adt(adt, substs) => {
+        ty::Adt(adt, args) => {
             let dont_elaborate = adt.is_union() || adt.is_manually_drop() || adt.has_dtor(tcx);
             if dont_elaborate {
                 return true;
@@ -119,7 +118,7 @@ fn is_needs_drop_and_init<'tcx>(
                     let downcast =
                         move_path_children_matching(move_data, mpi, |x| x.is_downcast_to(vid));
                     let Some(dc_mpi) = downcast else {
-                        return variant_needs_drop(tcx, param_env, substs, variant);
+                        return variant_needs_drop(tcx, param_env, args, variant);
                     };
 
                     dc_mpi
@@ -131,7 +130,7 @@ fn is_needs_drop_and_init<'tcx>(
                     .fields
                     .iter()
                     .enumerate()
-                    .map(|(f, field)| (FieldIdx::from_usize(f), field.ty(tcx, substs), mpi))
+                    .map(|(f, field)| (FieldIdx::from_usize(f), field.ty(tcx, args), mpi))
                     .any(field_needs_drop_and_init)
             })
         }
@@ -149,11 +148,11 @@ fn is_needs_drop_and_init<'tcx>(
 fn variant_needs_drop<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ParamEnv<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     variant: &VariantDef,
 ) -> bool {
     variant.fields.iter().any(|field| {
-        let f_ty = field.ty(tcx, substs);
+        let f_ty = field.ty(tcx, args);
         f_ty.needs_drop(tcx, param_env)
     })
 }
diff --git a/compiler/rustc_mir_transform/src/remove_zsts.rs b/compiler/rustc_mir_transform/src/remove_zsts.rs
index 1f37f03cff1..1ba9ad87537 100644
--- a/compiler/rustc_mir_transform/src/remove_zsts.rs
+++ b/compiler/rustc_mir_transform/src/remove_zsts.rs
@@ -15,7 +15,7 @@ impl<'tcx> MirPass<'tcx> for RemoveZsts {
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // Avoid query cycles (generators require optimized MIR for layout).
-        if tcx.type_of(body.source.def_id()).subst_identity().is_generator() {
+        if tcx.type_of(body.source.def_id()).instantiate_identity().is_generator() {
             return;
         }
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index b176db3c9e0..5e8ba4f544c 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -3,8 +3,8 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::InternalSubsts;
-use rustc_middle::ty::{self, EarlyBinder, GeneratorSubsts, Ty, TyCtxt};
+use rustc_middle::ty::GenericArgs;
+use rustc_middle::ty::{self, EarlyBinder, GeneratorArgs, Ty, TyCtxt};
 use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 
 use rustc_index::{Idx, IndexVec};
@@ -69,9 +69,9 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
         ty::InstanceDef::DropGlue(def_id, ty) => {
             // FIXME(#91576): Drop shims for generators aren't subject to the MIR passes at the end
             // of this function. Is this intentional?
-            if let Some(ty::Generator(gen_def_id, substs, _)) = ty.map(Ty::kind) {
+            if let Some(ty::Generator(gen_def_id, args, _)) = ty.map(Ty::kind) {
                 let body = tcx.optimized_mir(*gen_def_id).generator_drop().unwrap();
-                let body = EarlyBinder::bind(body.clone()).subst(tcx, substs);
+                let body = EarlyBinder::bind(body.clone()).instantiate(tcx, args);
                 debug!("make_shim({:?}) = {:?}", instance, body);
                 return body;
             }
@@ -160,12 +160,12 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
 
     assert!(!matches!(ty, Some(ty) if ty.is_generator()));
 
-    let substs = if let Some(ty) = ty {
-        tcx.mk_substs(&[ty.into()])
+    let args = if let Some(ty) = ty {
+        tcx.mk_args(&[ty.into()])
     } else {
-        InternalSubsts::identity_for_item(tcx, def_id)
+        GenericArgs::identity_for_item(tcx, def_id)
     };
-    let sig = tcx.fn_sig(def_id).subst(tcx, substs);
+    let sig = tcx.fn_sig(def_id).instantiate(tcx, args);
     let sig = tcx.erase_late_bound_regions(sig);
     let span = tcx.def_span(def_id);
 
@@ -377,12 +377,10 @@ fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -
 
     match self_ty.kind() {
         _ if is_copy => builder.copy_shim(),
-        ty::Closure(_, substs) => {
-            builder.tuple_like_shim(dest, src, substs.as_closure().upvar_tys())
-        }
+        ty::Closure(_, args) => builder.tuple_like_shim(dest, src, args.as_closure().upvar_tys()),
         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
-        ty::Generator(gen_def_id, substs, hir::Movability::Movable) => {
-            builder.generator_shim(dest, src, *gen_def_id, substs.as_generator())
+        ty::Generator(gen_def_id, args, hir::Movability::Movable) => {
+            builder.generator_shim(dest, src, *gen_def_id, args.as_generator())
         }
         _ => bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty),
     };
@@ -404,7 +402,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         // we must subst the self_ty because it's
         // otherwise going to be TySelf and we can't index
         // or access fields of a Place of type TySelf.
-        let sig = tcx.fn_sig(def_id).subst(tcx, &[self_ty.into()]);
+        let sig = tcx.fn_sig(def_id).instantiate(tcx, &[self_ty.into()]);
         let sig = tcx.erase_late_bound_regions(sig);
         let span = tcx.def_span(def_id);
 
@@ -587,17 +585,17 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         dest: Place<'tcx>,
         src: Place<'tcx>,
         gen_def_id: DefId,
-        substs: GeneratorSubsts<'tcx>,
+        args: GeneratorArgs<'tcx>,
     ) {
         self.block(vec![], TerminatorKind::Goto { target: self.block_index_offset(3) }, false);
         let unwind = self.block(vec![], TerminatorKind::Resume, true);
         // This will get overwritten with a switch once we know the target blocks
         let switch = self.block(vec![], TerminatorKind::Unreachable, false);
-        let unwind = self.clone_fields(dest, src, switch, unwind, substs.upvar_tys());
+        let unwind = self.clone_fields(dest, src, switch, unwind, args.upvar_tys());
         let target = self.block(vec![], TerminatorKind::Return, false);
         let unreachable = self.block(vec![], TerminatorKind::Unreachable, false);
-        let mut cases = Vec::with_capacity(substs.state_tys(gen_def_id, self.tcx).count());
-        for (index, state_tys) in substs.state_tys(gen_def_id, self.tcx).enumerate() {
+        let mut cases = Vec::with_capacity(args.state_tys(gen_def_id, self.tcx).count());
+        for (index, state_tys) in args.state_tys(gen_def_id, self.tcx).enumerate() {
             let variant_index = VariantIdx::new(index);
             let dest = self.tcx.mk_place_downcast_unnamed(dest, variant_index);
             let src = self.tcx.mk_place_downcast_unnamed(src, variant_index);
@@ -613,7 +611,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
             cases.push((index as u128, start_block));
             let _final_cleanup_block = self.clone_fields(dest, src, target, unwind, state_tys);
         }
-        let discr_ty = substs.discr_ty(self.tcx);
+        let discr_ty = args.discr_ty(self.tcx);
         let temp = self.make_place(Mutability::Mut, discr_ty);
         let rvalue = Rvalue::Discriminant(src);
         let statement = self.make_statement(StatementKind::Assign(Box::new((temp, rvalue))));
@@ -642,7 +640,7 @@ fn build_call_shim<'tcx>(
     // `FnPtrShim` contains the fn pointer type that a call shim is being built for - this is used
     // to substitute into the signature of the shim. It is not necessary for users of this
     // MIR body to perform further substitutions (see `InstanceDef::has_polymorphic_mir_body`).
-    let (sig_substs, untuple_args) = if let ty::InstanceDef::FnPtrShim(_, ty) = instance {
+    let (sig_args, untuple_args) = if let ty::InstanceDef::FnPtrShim(_, ty) = instance {
         let sig = tcx.erase_late_bound_regions(ty.fn_sig(tcx));
 
         let untuple_args = sig.inputs();
@@ -659,11 +657,11 @@ fn build_call_shim<'tcx>(
     let sig = tcx.fn_sig(def_id);
     let sig = sig.map_bound(|sig| tcx.erase_late_bound_regions(sig));
 
-    assert_eq!(sig_substs.is_some(), !instance.has_polymorphic_mir_body());
-    let mut sig = if let Some(sig_substs) = sig_substs {
-        sig.subst(tcx, &sig_substs)
+    assert_eq!(sig_args.is_some(), !instance.has_polymorphic_mir_body());
+    let mut sig = if let Some(sig_args) = sig_args {
+        sig.instantiate(tcx, &sig_args)
     } else {
-        sig.subst_identity()
+        sig.instantiate_identity()
     };
 
     if let CallKind::Indirect(fnty) = call_kind {
@@ -751,7 +749,7 @@ fn build_call_shim<'tcx>(
 
         // `FnDef` call with optional receiver.
         CallKind::Direct(def_id) => {
-            let ty = tcx.type_of(def_id).subst_identity();
+            let ty = tcx.type_of(def_id).instantiate_identity();
             (
                 Operand::Constant(Box::new(Constant {
                     span,
@@ -868,12 +866,12 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
     // Normalize the sig.
     let sig = tcx
         .fn_sig(ctor_id)
-        .subst_identity()
+        .instantiate_identity()
         .no_bound_vars()
         .expect("LBR in ADT constructor signature");
     let sig = tcx.normalize_erasing_regions(param_env, sig);
 
-    let ty::Adt(adt_def, substs) = sig.output().kind() else {
+    let ty::Adt(adt_def, args) = sig.output().kind() else {
         bug!("unexpected type for ADT ctor {:?}", sig.output());
     };
 
@@ -896,7 +894,7 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
     // return;
     debug!("build_ctor: variant_index={:?}", variant_index);
 
-    let kind = AggregateKind::Adt(adt_def.did(), variant_index, substs, None, None);
+    let kind = AggregateKind::Adt(adt_def.did(), variant_index, args, None, None);
     let variant = adt_def.variant(variant_index);
     let statement = Statement {
         kind: StatementKind::Assign(Box::new((
@@ -941,7 +939,7 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
 fn build_fn_ptr_addr_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
     assert!(matches!(self_ty.kind(), ty::FnPtr(..)), "expected fn ptr, found {self_ty}");
     let span = tcx.def_span(def_id);
-    let Some(sig) = tcx.fn_sig(def_id).subst(tcx, &[self_ty.into()]).no_bound_vars() else {
+    let Some(sig) = tcx.fn_sig(def_id).instantiate(tcx, &[self_ty.into()]).no_bound_vars() else {
         span_bug!(span, "FnPtr::addr with bound vars for `{self_ty}`");
     };
     let locals = local_decls_for_sig(&sig, span);
diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs
index e59219321b7..b7a51cfd619 100644
--- a/compiler/rustc_mir_transform/src/simplify.rs
+++ b/compiler/rustc_mir_transform/src/simplify.rs
@@ -199,7 +199,8 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
         let last = current;
         *start = last;
         while let Some((current, mut terminator)) = terminators.pop() {
-            let Terminator { kind: TerminatorKind::Goto { ref mut target }, .. } = terminator else {
+            let Terminator { kind: TerminatorKind::Goto { ref mut target }, .. } = terminator
+            else {
                 unreachable!();
             };
             *changed |= *target != last;
diff --git a/compiler/rustc_mir_transform/src/sroa.rs b/compiler/rustc_mir_transform/src/sroa.rs
index 881a1547c52..e66ae8ff884 100644
--- a/compiler/rustc_mir_transform/src/sroa.rs
+++ b/compiler/rustc_mir_transform/src/sroa.rs
@@ -20,7 +20,7 @@ impl<'tcx> MirPass<'tcx> for ScalarReplacementOfAggregates {
         debug!(def_id = ?body.source.def_id());
 
         // Avoid query cycles (generators require optimized MIR for layout).
-        if tcx.type_of(body.source.def_id()).subst_identity().is_generator() {
+        if tcx.type_of(body.source.def_id()).instantiate_identity().is_generator() {
             return;
         }
 
@@ -64,7 +64,7 @@ fn escaping_locals<'tcx>(
         if ty.is_union() || ty.is_enum() {
             return true;
         }
-        if let ty::Adt(def, _substs) = ty.kind() {
+        if let ty::Adt(def, _args) = ty.kind() {
             if def.repr().flags.contains(ReprFlags::IS_SIMD) {
                 // Exclude #[repr(simd)] types so that they are not de-optimized into an array
                 return true;
@@ -161,7 +161,9 @@ struct ReplacementMap<'tcx> {
 
 impl<'tcx> ReplacementMap<'tcx> {
     fn replace_place(&self, tcx: TyCtxt<'tcx>, place: PlaceRef<'tcx>) -> Option<Place<'tcx>> {
-        let &[PlaceElem::Field(f, _), ref rest @ ..] = place.projection else { return None; };
+        let &[PlaceElem::Field(f, _), ref rest @ ..] = place.projection else {
+            return None;
+        };
         let fields = self.fragments[place.local].as_ref()?;
         let (_, new_local) = fields[f]?;
         Some(Place { local: new_local, projection: tcx.mk_place_elems(&rest) })
diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs
index 8dc2dfe13bd..04bc461c815 100644
--- a/compiler/rustc_mir_transform/src/ssa.rs
+++ b/compiler/rustc_mir_transform/src/ssa.rs
@@ -266,9 +266,11 @@ fn compute_copy_classes(ssa: &mut SsaLocals, body: &Body<'_>) {
     let mut copies = IndexVec::from_fn_n(|l| l, body.local_decls.len());
 
     for (local, rvalue, _) in ssa.assignments(body) {
-        let (Rvalue::Use(Operand::Copy(place) | Operand::Move(place)) | Rvalue::CopyForDeref(place))
-            = rvalue
-        else { continue };
+        let (Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
+        | Rvalue::CopyForDeref(place)) = rvalue
+        else {
+            continue;
+        };
 
         let Some(rhs) = place.as_local() else { continue };
         let local_ty = body.local_decls()[local].ty;
diff --git a/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs b/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
index 5389b9f52eb..092bcb5c979 100644
--- a/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
+++ b/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
@@ -105,7 +105,8 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
         for bb in body.basic_blocks.indices() {
             trace!("processing block {:?}", bb);
 
-            let Some(discriminant_ty) = get_switched_on_type(&body.basic_blocks[bb], tcx, body) else {
+            let Some(discriminant_ty) = get_switched_on_type(&body.basic_blocks[bb], tcx, body)
+            else {
                 continue;
             };