Auto merge of #112246 - Mark-Simulacrum:beta-next, r=Mark-Simulacrum

[beta] backports + stage0 bump

This bumps the beta branch to use 1.70 as the bootstrap compiler, and backports:

* #112070

r? `@Mark-Simulacrum`

Author: bors

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) |
 
         // `PlaceMention` and `AscribeUserType` both evaluate the place, which must not
         // contain dangling references.

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -766,8 +766,8 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             PlaceContext::MutatingUse(_) => ty::Invariant,
             PlaceContext::NonUse(StorageDead | StorageLive | VarDebugInfo) => ty::Invariant,
             PlaceContext::NonMutatingUse(
-                Inspect | Copy | Move | PlaceMention | SharedBorrow | ShallowBorrow | UniqueBorrow
-                | AddressOf | Projection,
+                Inspect | Copy | Move | PlaceMention | SharedBorrow | ShallowBorrow | AddressOf
+                | Projection,
             ) => ty::Covariant,
             PlaceContext::NonUse(AscribeUserTy(variance)) => variance,
         }

compiler/rustc_codegen_ssa/src/mir/analyze.rs

@@ -234,7 +234,6 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
             | PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::Inspect
                 | NonMutatingUseContext::SharedBorrow
-                | NonMutatingUseContext::UniqueBorrow
                 | NonMutatingUseContext::ShallowBorrow
                 | NonMutatingUseContext::AddressOf
                 | NonMutatingUseContext::Projection,

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -412,9 +412,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         BorrowKind::Shallow => {
                             PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow)
                         }
-                        BorrowKind::Unique => {
-                            PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow)
-                        }
+                        BorrowKind::Unique => PlaceContext::MutatingUse(MutatingUseContext::Borrow),
                         BorrowKind::Mut { .. } => {
                             PlaceContext::MutatingUse(MutatingUseContext::Borrow)
                         }

compiler/rustc_middle/src/mir/syntax.rs

@@ -220,6 +220,11 @@ pub enum BorrowKind {
     /// immutable, but not aliasable. This solves the problem. For
     /// simplicity, we don't give users the way to express this
     /// borrow, it's just used when translating closures.
+    ///
+    // FIXME(#112072): This is wrong. Unique borrows are mutable borrows except
+    // that they do not require their pointee to be marked as a mutable.
+    // They should still be treated as mutable borrows in every other way,
+    // e.g. for variance or overlap checking.
     Unique,
 
     /// Data is mutable and not aliasable.

compiler/rustc_middle/src/mir/visit.rs

@@ -650,8 +650,8 @@ macro_rules! make_mir_visitor {
                             BorrowKind::Shallow => PlaceContext::NonMutatingUse(
                                 NonMutatingUseContext::ShallowBorrow
                             ),
-                            BorrowKind::Unique => PlaceContext::NonMutatingUse(
-                                NonMutatingUseContext::UniqueBorrow
+                            BorrowKind::Unique => PlaceContext::MutatingUse(
+                                MutatingUseContext::Borrow
                             ),
                             BorrowKind::Mut { .. } =>
                                 PlaceContext::MutatingUse(MutatingUseContext::Borrow),
@@ -1265,8 +1265,6 @@ pub enum NonMutatingUseContext {
     SharedBorrow,
     /// Shallow borrow.
     ShallowBorrow,
-    /// Unique borrow.
-    UniqueBorrow,
     /// AddressOf for *const pointer.
     AddressOf,
     /// PlaceMention statement.
@@ -1345,9 +1343,7 @@ impl PlaceContext {
         matches!(
             self,
             PlaceContext::NonMutatingUse(
-                NonMutatingUseContext::SharedBorrow
-                    | NonMutatingUseContext::ShallowBorrow
-                    | NonMutatingUseContext::UniqueBorrow
+                NonMutatingUseContext::SharedBorrow | NonMutatingUseContext::ShallowBorrow
             ) | PlaceContext::MutatingUse(MutatingUseContext::Borrow)
         )
     }

compiler/rustc_mir_dataflow/src/impls/liveness.rs

@@ -199,8 +199,7 @@ impl DefUse {
                 | NonMutatingUseContext::Move
                 | NonMutatingUseContext::PlaceMention
                 | NonMutatingUseContext::ShallowBorrow
-                | NonMutatingUseContext::SharedBorrow
-                | NonMutatingUseContext::UniqueBorrow,
+                | NonMutatingUseContext::SharedBorrow,
             ) => Some(DefUse::Use),
 
             PlaceContext::MutatingUse(MutatingUseContext::Projection)

compiler/rustc_mir_transform/src/const_prop.rs

@@ -772,7 +772,6 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
             // mutation.
             | NonMutatingUse(NonMutatingUseContext::SharedBorrow)
             | NonMutatingUse(NonMutatingUseContext::ShallowBorrow)
-            | NonMutatingUse(NonMutatingUseContext::UniqueBorrow)
             | NonMutatingUse(NonMutatingUseContext::AddressOf)
             | MutatingUse(MutatingUseContext::Borrow)
             | MutatingUse(MutatingUseContext::AddressOf) => {

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -130,7 +130,6 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
             PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::SharedBorrow
                 | NonMutatingUseContext::ShallowBorrow
-                | NonMutatingUseContext::UniqueBorrow
                 | NonMutatingUseContext::AddressOf,
             ) => true,
             // For debuginfo, merging locals is ok.

compiler/rustc_mir_transform/src/ssa.rs

@@ -216,7 +216,6 @@ impl<'tcx> Visitor<'tcx> for SsaVisitor<'_> {
             PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::SharedBorrow
                 | NonMutatingUseContext::ShallowBorrow
-                | NonMutatingUseContext::UniqueBorrow
                 | NonMutatingUseContext::AddressOf,
             )
             | PlaceContext::MutatingUse(_) => {