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const_refs_to_cell: dont let mutable references sneak past the interior mutability check

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This commit is contained in:
Ralf Jung 2024-08-21 22:30:16 +02:00
parent 9ad5728593
commit 544a6a7df3
5 changed files with 59 additions and 11 deletions
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13
compiler/rustc_const_eval/src/check_consts/check.rs
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@ -433,7 +433,18 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
// `TransientCellBorrow` (we consider the equivalent mutable case a
// `TransientMutBorrow`), but such reborrows got accidentally stabilized already and
// it is too much of a breaking change to take back.
if borrowed_place_has_mut_interior && !place.is_indirect() {
// However, we only want to consider places that are obtained by dereferencing
// a *shared* reference. Mutable references to interior mutable data are stable,
// and we don't want `&*&mut interior_mut` to be accepted.
let is_indirect = place.iter_projections().any(|(base, proj)| {
matches!(proj, ProjectionElem::Deref)
&& matches!(
base.ty(self.body, self.tcx).ty.kind(),
ty::Ref(_, _, Mutability::Not) | ty::RawPtr(_, Mutability::Not)
)
});
if borrowed_place_has_mut_interior && !is_indirect {
match self.const_kind() {
// In a const fn all borrows are transient or point to the places given via
// references in the arguments (so we already checked them with