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Change comment to reflect switch to THIR unsafeck

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Nadrieril 2024-06-22 18:21:03 +02:00
parent ff49c3769b
commit beb1d35d7d
1 changed files with 10 additions and 14 deletions
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24
compiler/rustc_mir_build/src/build/matches/mod.rs
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@ -1258,21 +1258,17 @@ fn lower_match_tree<'pat>(
// cases.
let source_info = self.source_info(scrutinee_span);
// Matching on a `scrutinee_place` with an uninhabited type doesn't
// generate any memory reads by itself, and so if the place "expression"
// contains unsafe operations like raw pointer dereferences or union
// field projections, we wouldn't know to require an `unsafe` block
// around a `match` equivalent to `std::intrinsics::unreachable()`.
// See issue #47412 for this hole being discovered in the wild.
// Matching on a scrutinee place of an uninhabited type doesn't generate any memory
// reads by itself, and so if the place is uninitialized we wouldn't know. In order to
// disallow the following:
// ```rust
// let x: !;
// match x {}
// ```
// we add a dummy read on the place.
//
// HACK(eddyb) Work around the above issue by adding a dummy inspection
// of `scrutinee_place`, specifically by applying `ReadForMatch`.
//
// NOTE: ReadForMatch also checks that the scrutinee is initialized.
// This is currently needed to not allow matching on an uninitialized,
// uninhabited value. If we get never patterns, those will check that
// the place is initialized, and so this read would only be used to
// check safety.
// NOTE: If we require never patterns for empty matches, those will check that the place
// is initialized, and so this read would no longer be needed.
let cause_matched_place = FakeReadCause::ForMatchedPlace(None);
if let Some(scrutinee_place) = scrutinee_place_builder.try_to_place(self) {