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Permit mutable references in all const contexts

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This commit is contained in:
oli
2021-01-03 18:46:20 +00:00
parent 1986b58c64
commit d118021f8b
35 changed files with 298 additions and 171 deletions
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29
compiler/rustc_mir/src/transform/check_consts/validation.rs
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@@ -466,6 +466,29 @@ impl Validator<'mir, 'tcx> {
}
}
}
fn check_mut_borrow(&mut self, local: Local, kind: hir::BorrowKind) {
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
// TransientMutBorrow/MutBorrow as appropriate).
// The borrow checker guarantees that no new non-transient borrows are created.
// NOTE: Once we have heap allocations during CTFE we need to figure out
// how to prevent `const fn` to create long-lived allocations that point
// to mutable memory.
hir::ConstContext::ConstFn => self.check_op(ops::TransientMutBorrow(kind)),
_ => {
// Locals with StorageDead do not live beyond the evaluation and can
// thus safely be borrowed without being able to be leaked to the final
// value of the constant.
if self.local_has_storage_dead(local) {
self.check_op(ops::TransientMutBorrow(kind));
} else {
self.check_op(ops::MutBorrow(kind));
}
}
}
}
}
impl Visitor<'tcx> for Validator<'mir, 'tcx> {
@@ -562,15 +585,15 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
if !is_allowed {
if let BorrowKind::Mut { .. } = kind {
self.check_op(ops::MutBorrow(hir::BorrowKind::Ref));
self.check_mut_borrow(place.local, hir::BorrowKind::Ref)
} else {
self.check_op(ops::CellBorrow);
}
}
}
Rvalue::AddressOf(Mutability::Mut, _) => {
self.check_op(ops::MutBorrow(hir::BorrowKind::Raw))
Rvalue::AddressOf(Mutability::Mut, ref place) => {
self.check_mut_borrow(place.local, hir::BorrowKind::Raw)
}
Rvalue::Ref(_, BorrowKind::Shared | BorrowKind::Shallow, ref place)