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/diagnostics/conflict_errors.rs
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@ -17,9 +17,9 @@ use rustc_middle::hir::nested_filter::OnlyBodies;
use rustc_middle::mir::tcx::PlaceTy;
use rustc_middle::mir::{
self, AggregateKind, BindingForm, BorrowKind, CallSource, ClearCrossCrate, ConstraintCategory,
FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, MutBorrowKind, Operand, Place,
PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
VarBindingForm,
FakeBorrowKind, FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, MutBorrowKind,
Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind, VarBindingForm,
};
use rustc_middle::ty::{
self, suggest_constraining_type_params, PredicateKind, ToPredicate, Ty, TyCtxt,
@ -1486,7 +1486,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let first_borrow_desc;
let mut err = match (gen_borrow_kind, issued_borrow.kind) {
(
BorrowKind::Shared,
BorrowKind::Shared | BorrowKind::Fake(FakeBorrowKind::Deep),
BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow },
) => {
first_borrow_desc = "mutable ";
@ -1504,7 +1504,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
(
BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow },
BorrowKind::Shared,
BorrowKind::Shared | BorrowKind::Fake(FakeBorrowKind::Deep),
) => {
first_borrow_desc = "immutable ";
let mut err = self.cannot_reborrow_already_borrowed(
@ -1566,7 +1566,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
self.cannot_uniquely_borrow_by_two_closures(span, &desc_place, issued_span, None)
}
(BorrowKind::Mut { .. }, BorrowKind::Fake) => {
(BorrowKind::Mut { .. }, BorrowKind::Fake(FakeBorrowKind::Shallow)) => {
if let Some(immutable_section_description) =
self.classify_immutable_section(issued_borrow.assigned_place)
{
@ -1629,7 +1629,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
)
}
(BorrowKind::Shared, BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }) => {
(
BorrowKind::Shared | BorrowKind::Fake(FakeBorrowKind::Deep),
BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture },
) => {
first_borrow_desc = "first ";
self.cannot_reborrow_already_uniquely_borrowed(
span,
@ -1659,8 +1662,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
)
}
(BorrowKind::Shared, BorrowKind::Shared | BorrowKind::Fake)
| (BorrowKind::Fake, BorrowKind::Mut { .. } | BorrowKind::Shared | BorrowKind::Fake) => {
(
BorrowKind::Shared | BorrowKind::Fake(FakeBorrowKind::Deep),
BorrowKind::Shared | BorrowKind::Fake(_),
)
| (
BorrowKind::Fake(FakeBorrowKind::Shallow),
BorrowKind::Mut { .. } | BorrowKind::Shared | BorrowKind::Fake(_),
) => {
unreachable!()
}
};
@ -3572,7 +3581,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let loan_span = loan_spans.args_or_use();
let descr_place = self.describe_any_place(place.as_ref());
if loan.kind == BorrowKind::Fake {
if let BorrowKind::Fake(_) = loan.kind {
if let Some(section) = self.classify_immutable_section(loan.assigned_place) {
let mut err = self.cannot_mutate_in_immutable_section(
span,