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static mut: allow reference to arbitrary types, not just slices and arrays

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This commit is contained in:
Ralf Jung 2023-11-05 16:58:47 +01:00
parent 7df6f4a15e
commit 9a819ab8f7
9 changed files with 46 additions and 77 deletions
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40
compiler/rustc_const_eval/src/transform/check_consts/check.rs
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@ -476,35 +476,27 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
}
}
Rvalue::Ref(_, BorrowKind::Mut { .. }, place) => {
let ty = place.ty(self.body, self.tcx).ty;
let is_allowed = match ty.kind() {
// Inside a `static mut`, `&mut [...]` is allowed.
ty::Array(..) | ty::Slice(_)
if self.const_kind() == hir::ConstContext::Static(hir::Mutability::Mut) =>
{
true
}
// FIXME(ecstaticmorse): We could allow `&mut []` inside a const context given
// that this is merely a ZST and it is already eligible for promotion.
// This may require an RFC?
/*
ty::Array(_, len) if len.try_eval_target_usize(cx.tcx, cx.param_env) == Some(0)
=> true,
*/
_ => false,
};
Rvalue::Ref(_, BorrowKind::Mut { .. }, place)
| Rvalue::AddressOf(Mutability::Mut, place) => {
// Inside mutable statics, we allow arbitrary mutable references.
// We've allowed `static mut FOO = &mut [elements];` for a long time (the exact
// reasons why are lost to history), and there is no reason to restrict that to
// arrays and slices.
let is_allowed =
self.const_kind() == hir::ConstContext::Static(hir::Mutability::Mut);
if !is_allowed {
self.check_mut_borrow(place.local, hir::BorrowKind::Ref)
self.check_mut_borrow(
place.local,
if matches!(rvalue, Rvalue::Ref(..)) {
hir::BorrowKind::Ref
} else {
hir::BorrowKind::Raw
},
);
}
}
Rvalue::AddressOf(Mutability::Mut, place) => {
self.check_mut_borrow(place.local, hir::BorrowKind::Raw)
}
Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Fake, place)
| Rvalue::AddressOf(Mutability::Not, place) => {
let borrowed_place_has_mut_interior = qualifs::in_place::<HasMutInterior, _>(