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Consider lvalues of field and index as possibly temporary places

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This commit is contained in:
Michael Goulet 2025-02-23 01:09:51 +00:00
parent 2797936f6d
commit bad8e98c7d
5 changed files with 46 additions and 1 deletions
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8
compiler/rustc_lint/src/if_let_rescope.rs
View file

@ -436,6 +436,14 @@ impl<'tcx> Visitor<'tcx> for FindSignificantDropper<'_, 'tcx> {
self.check_promoted_temp_with_drop(expr)?;
intravisit::walk_expr(self, expr)
}
// `(Drop, ()).1` introduces a temporary and then moves out of
// part of it, therefore we should check it for temporaries.
// FIXME: This may have false positives if we move the part
// that actually has drop, but oh well.
hir::ExprKind::Index(expr, _, _) | hir::ExprKind::Field(expr, _) => {
self.check_promoted_temp_with_drop(expr)?;
intravisit::walk_expr(self, expr)
}
// If always introduces a temporary terminating scope for its cond and arms,
// so don't visit them.
hir::ExprKind::If(..) => ControlFlow::Continue(()),

4
tests/ui/drop/lint-if-let-rescope-false-positives.rs
View file

@ -26,4 +26,8 @@ fn main() {
// Make sure we don't lint if we consume the droppy value.
if let None = consume(Drop) {} else {}
// Make sure we don't lint on field exprs of place exprs.
let tup_place = (Drop, ());
if let None = consume(tup_place.1) {} else {}
}

6
tests/ui/drop/lint-if-let-rescope.fixed
View file

@ -94,6 +94,12 @@ fn main() {
//~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
}
match Some((droppy(), ()).1) { Some(_value) => {} _ => {}}
//~^ ERROR: `if let` assigns a shorter lifetime since Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| HELP: the value is now dropped here in Edition 2024
//~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
// We want to keep the `if let`s below as direct descendents of match arms,
// so the formatting is suppressed.
#[rustfmt::skip]

6
tests/ui/drop/lint-if-let-rescope.rs
View file

@ -94,6 +94,12 @@ fn main() {
//~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
}
if let Some(_value) = Some((droppy(), ()).1) {} else {}
//~^ ERROR: `if let` assigns a shorter lifetime since Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| HELP: the value is now dropped here in Edition 2024
//~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
// We want to keep the `if let`s below as direct descendents of match arms,
// so the formatting is suppressed.
#[rustfmt::skip]

23
tests/ui/drop/lint-if-let-rescope.stderr
View file

@ -175,5 +175,26 @@ LL - while (if let Some(_value) = droppy().get() { false } else { true }) {
LL + while (match droppy().get() { Some(_value) => { false } _ => { true }}) {
|
error: aborting due to 7 previous errors
error: `if let` assigns a shorter lifetime since Edition 2024
--> $DIR/lint-if-let-rescope.rs:97:8
|
LL | if let Some(_value) = Some((droppy(), ()).1) {} else {}
| ^^^^^^^^^^^^^^^^^^^^^^^^--------------^^^
| |
| this value has a significant drop implementation which may observe a major change in drop order and requires your discretion
|
= warning: this changes meaning in Rust 2024
= note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-if-let-scope.html>
help: the value is now dropped here in Edition 2024
--> $DIR/lint-if-let-rescope.rs:97:51
|
LL | if let Some(_value) = Some((droppy(), ()).1) {} else {}
| ^
help: a `match` with a single arm can preserve the drop order up to Edition 2021
|
LL - if let Some(_value) = Some((droppy(), ()).1) {} else {}
LL + match Some((droppy(), ()).1) { Some(_value) => {} _ => {}}
|
error: aborting due to 8 previous errors