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Do not use desugared local names in tail_expr_drop_order diagnostics #157942

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Merged
rust-bors merged 2 commits into from
Jun 21, 2026
Merged

Do not use desugared local names in tail_expr_drop_order diagnostics #157942

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cb94fdb
add regression test
qaijuang Jun 15, 2026
8e3a32e
do not use desugared local names in tail_expr_drop_order
qaijuang Jun 15, 2026
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1 change: 1 addition & 0 deletions compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -466,6 +466,7 @@ fn collect_user_names(body: &Body<'_>) -> FxIndexMap<Local, Symbol> {
for var_debug_info in &body.var_debug_info {
if let mir::VarDebugInfoContents::Place(place) = &var_debug_info.value
&& let Some(local) = place.local_or_deref_local()
&& !body.local_decls[local].from_compiler_desugaring()
{
names.entry(local).or_insert(var_debug_info.name);
}
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15 changes: 15 additions & 0 deletions tests/ui/drop/tail_expr_drop_order-on-coroutine-unwind.rs
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Expand Up @@ -26,3 +26,18 @@ async fn retry_db() -> Result<(), Drop> {
}

fn main() {}

// Regression test for https://github.com/rust-lang/rust/issues/136206:
// a user-written binding named `__awaitee` is still a user-visible name.
impl Drop {
fn get(&self) -> u8 {
0
}
}

fn user_written_awaitee() -> u8 {
let __awaitee = Drop;
__awaitee.get() + Drop.get()
//~^ ERROR relative drop order changing in Rust 2024
//~| WARNING this changes meaning in Rust 2024
}
53 changes: 42 additions & 11 deletions tests/ui/drop/tail_expr_drop_order-on-coroutine-unwind.stderr
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Expand Up @@ -4,14 +4,14 @@ error: relative drop order changing in Rust 2024
LL | match func().await {
| ^^^^^^^-----
| | |
| | this value will be stored in a temporary; let us call it `#3`
| | up until Edition 2021 `#3` is dropped last but will be dropped earlier in Edition 2024
| | this value will be stored in a temporary; let us call it `#1`
| | `#1` will be dropped later as of Edition 2024
| this value will be stored in a temporary; let us call it `#2`
| up until Edition 2021 `#2` is dropped last but will be dropped earlier in Edition 2024
| `__awaitee` calls a custom destructor
| `__awaitee` will be dropped later as of Edition 2024
| | this value will be stored in a temporary; let us call it `#4`
| | up until Edition 2021 `#4` is dropped last but will be dropped earlier in Edition 2024
| | this value will be stored in a temporary; let us call it `#2`
| | `#2` will be dropped later as of Edition 2024
| this value will be stored in a temporary; let us call it `#3`
| up until Edition 2021 `#3` is dropped last but will be dropped earlier in Edition 2024
| this value will be stored in a temporary; let us call it `#1`
| `#1` will be dropped later as of Edition 2024
...
LL | Err(e) => {}
| -
Expand All @@ -22,12 +22,12 @@ LL | }
LL | }
| - now the temporary value is dropped here, before the local variables in the block or statement
|
note: `#2` invokes this custom destructor
note: `#3` invokes this custom destructor
--> $DIR/tail_expr_drop_order-on-coroutine-unwind.rs:9:1
|
LL | impl std::ops::Drop for Drop {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: `#1` invokes this custom destructor
note: `#2` invokes this custom destructor
--> $DIR/tail_expr_drop_order-on-coroutine-unwind.rs:9:1
|
LL | impl std::ops::Drop for Drop {
Expand All @@ -46,5 +46,36 @@ note: the lint level is defined here
LL | #![deny(tail_expr_drop_order)]
| ^^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error
error: relative drop order changing in Rust 2024
--> $DIR/tail_expr_drop_order-on-coroutine-unwind.rs:40:23
|
LL | let __awaitee = Drop;
| ---------
| |
| `__awaitee` calls a custom destructor
| `__awaitee` will be dropped later as of Edition 2024
LL | __awaitee.get() + Drop.get()
| ^^^^
| |
| this value will be stored in a temporary; let us call it `#1`
| up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
...
LL | }
| - now the temporary value is dropped here, before the local variables in the block or statement
|
note: `#1` invokes this custom destructor
--> $DIR/tail_expr_drop_order-on-coroutine-unwind.rs:9:1
|
LL | impl std::ops::Drop for Drop {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: `__awaitee` invokes this custom destructor
--> $DIR/tail_expr_drop_order-on-coroutine-unwind.rs:9:1
|
LL | impl std::ops::Drop for Drop {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects like releasing locks or sending messages
= warning: this changes meaning in Rust 2024
= note: for more information, see <https://doc.rust-lang.org/edition-guide/rust-2024/temporary-tail-expr-scope.html>

error: aborting due to 2 previous errors

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