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Don't fake borrow inside a deref pattern

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This commit is contained in:
Nadrieril 2024-03-09 16:10:45 +01:00
parent c623319a30
commit 1dabacd059
2 changed files with 14 additions and 4 deletions
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14
compiler/rustc_mir_build/src/build/matches/mod.rs
View file

@ -5,7 +5,7 @@
//! This also includes code for pattern bindings in `let` statements and
//! function parameters.
use crate::build::expr::as_place::PlaceBuilder;
use crate::build::expr::as_place::{PlaceBase, PlaceBuilder};
use crate::build::scope::DropKind;
use crate::build::ForGuard::{self, OutsideGuard, RefWithinGuard};
use crate::build::{BlockAnd, BlockAndExtension, Builder};
@ -438,7 +438,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
if let Some(ref borrows) = fake_borrows {
self.calculate_fake_borrows(borrows, scrutinee_span)
self.calculate_fake_borrows(borrows, scrutinee_place_builder.base(), scrutinee_span)
} else {
Vec::new()
}
@ -1936,6 +1936,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn calculate_fake_borrows<'b>(
&mut self,
fake_borrows: &'b FxIndexSet<Place<'tcx>>,
scrutinee_base: PlaceBase,
temp_span: Span,
) -> Vec<(Place<'tcx>, Local)> {
let tcx = self.tcx;
@ -1946,6 +1947,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// Insert a Shallow borrow of the prefixes of any fake borrows.
for place in fake_borrows {
if let PlaceBase::Local(l) = scrutinee_base
&& l != place.local
{
// The base of this place is a temporary created for deref patterns. We don't emit
// fake borrows for these as they are not initialized in all branches.
// FIXME(deref_patterns): is this sound?
continue;
}
let mut cursor = place.projection.as_ref();
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

4
tests/ui/pattern/deref-patterns/bindings.rs
View file

@ -5,8 +5,7 @@
fn simple_vec(vec: Vec<u32>) -> u32 {
match vec {
deref!([]) => 100,
// FIXME(deref_patterns): fake borrows break guards
// deref!([x]) if x == 4 => x + 4,
deref!([x]) if x == 4 => x + 4,
deref!([x]) => x,
deref!([1, x]) => x + 200,
deref!(ref slice) => slice.iter().sum(),
@ -29,6 +28,7 @@ fn main() {
assert_eq!(simple_vec(vec![1]), 1);
assert_eq!(simple_vec(vec![1, 2]), 202);
assert_eq!(simple_vec(vec![1, 2, 3]), 6);
assert_eq!(simple_vec(vec![4]), 8);
assert_eq!(nested_vec(vec![vec![0, 42]]), 42);
assert_eq!(nested_vec(vec![vec![1, 42]]), 42);