bjoernager/rust
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Rollup merge of #122598 - Nadrieril:full-derefpats, r=matthewjasper

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deref patterns: lower deref patterns to MIR

This lowers deref patterns to MIR. This is a bit tricky because this is the first kind of pattern that requires storing a value in a temporary. Thanks to https://github.com/rust-lang/rust/pull/123324 false edges are no longer a problem.

The thing I'm not confident about is the handling of fake borrows. This PR ignores any fake borrows inside a deref pattern. We are guaranteed to at least fake borrow the place of the first pointer value, which could be enough, but I'm not certain.
This commit is contained in:
León Orell Valerian Liehr 2024-04-23 17:25:15 +02:00 • committed by GitHub
commit 332cac2c6d
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51 changed files with 764 additions and 301 deletions
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29
compiler/rustc_borrowck/src/lib.rs
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@ -1056,18 +1056,19 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
Control::Continue
}
(Read(_), BorrowKind::Shared | BorrowKind::Fake)
| (Read(ReadKind::Borrow(BorrowKind::Fake)), BorrowKind::Mut { .. }) => {
Control::Continue
}
(Read(_), BorrowKind::Shared | BorrowKind::Fake(_))
| (
Read(ReadKind::Borrow(BorrowKind::Fake(FakeBorrowKind::Shallow))),
BorrowKind::Mut { .. },
) => Control::Continue,
(Reservation(_), BorrowKind::Fake | BorrowKind::Shared) => {
(Reservation(_), BorrowKind::Fake(_) | BorrowKind::Shared) => {
// This used to be a future compatibility warning (to be
// disallowed on NLL). See rust-lang/rust#56254
Control::Continue
}
(Write(WriteKind::Move), BorrowKind::Fake) => {
(Write(WriteKind::Move), BorrowKind::Fake(FakeBorrowKind::Shallow)) => {
// Handled by initialization checks.
Control::Continue
}
@ -1175,10 +1176,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
match rvalue {
&Rvalue::Ref(_ /*rgn*/, bk, place) => {
let access_kind = match bk {
BorrowKind::Fake => {
BorrowKind::Fake(FakeBorrowKind::Shallow) => {
(Shallow(Some(ArtificialField::FakeBorrow)), Read(ReadKind::Borrow(bk)))
}
BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))),
BorrowKind::Shared | BorrowKind::Fake(FakeBorrowKind::Deep) => {
(Deep, Read(ReadKind::Borrow(bk)))
}
BorrowKind::Mut { .. } => {
let wk = WriteKind::MutableBorrow(bk);
if allow_two_phase_borrow(bk) {
@ -1197,7 +1200,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
flow_state,
);
let action = if bk == BorrowKind::Fake {
let action = if bk == BorrowKind::Fake(FakeBorrowKind::Shallow) {
InitializationRequiringAction::MatchOn
} else {
InitializationRequiringAction::Borrow
@ -1557,7 +1560,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
// only mutable borrows should be 2-phase
assert!(match borrow.kind {
BorrowKind::Shared | BorrowKind::Fake => false,
BorrowKind::Shared | BorrowKind::Fake(_) => false,
BorrowKind::Mut { .. } => true,
});
@ -2122,14 +2125,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
| WriteKind::Replace
| WriteKind::StorageDeadOrDrop
| WriteKind::MutableBorrow(BorrowKind::Shared)
| WriteKind::MutableBorrow(BorrowKind::Fake),
| WriteKind::MutableBorrow(BorrowKind::Fake(_)),
)
| Write(
WriteKind::Move
| WriteKind::Replace
| WriteKind::StorageDeadOrDrop
| WriteKind::MutableBorrow(BorrowKind::Shared)
| WriteKind::MutableBorrow(BorrowKind::Fake),
| WriteKind::MutableBorrow(BorrowKind::Fake(_)),
) => {
if self.is_mutable(place.as_ref(), is_local_mutation_allowed).is_err()
&& !self.has_buffered_diags()
@ -2153,7 +2156,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
return false;
}
Read(
ReadKind::Borrow(BorrowKind::Mut { .. } | BorrowKind::Shared | BorrowKind::Fake)
ReadKind::Borrow(BorrowKind::Mut { .. } | BorrowKind::Shared | BorrowKind::Fake(_))
| ReadKind::Copy,
) => {
// Access authorized