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lowering: extend temporary lifetimes around await
This commit changes the HIR lowering around `await` so that temporary
lifetimes are extended. Previously, await was lowered as:
```rust
{
let mut pinned = future;
loop {
match ::std::future::poll_with_tls_context(unsafe {
<::std::pin::Pin>::new_unchecked(&mut pinned)
}) {
::std::task::Poll::Ready(result) => break result,
::std::task::Poll::Pending => {}
}
yield ();
}
}
```
With this commit, await is lowered as:
```rust
match future {
mut pinned => loop {
match ::std::future::poll_with_tls_context(unsafe {
<::std::pin::Pin>::new_unchecked(&mut pinned)
}) {
::std::task::Poll::Ready(result) => break result,
::std::task::Poll::Pending => {}
}
yield ();
}
}
```
However, this change has the following side-effects:
- All temporaries in future will be considered to live across a
yield for the purpose of auto-traits.
- Borrowed temporaries in future are likely to be considered to be live
across the yield for the purpose of the generator transform.
Signed-off-by: David Wood <david@davidtw.co>- Loading branch information
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19 changes: 19 additions & 0 deletions
19
src/test/ui/async-await/issue-63832-await-short-temporary-lifetime-1.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| // check-pass | ||
| // edition:2018 | ||
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| struct Test(String); | ||
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| impl Test { | ||
| async fn borrow_async(&self) {} | ||
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| fn with(&mut self, s: &str) -> &mut Self { | ||
| self.0 = s.into(); | ||
| self | ||
| } | ||
| } | ||
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| async fn test() { | ||
| Test("".to_string()).with("123").borrow_async().await; | ||
| } | ||
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| fn main() { } |
12 changes: 12 additions & 0 deletions
12
src/test/ui/async-await/issue-63832-await-short-temporary-lifetime.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,12 @@ | ||
| // check-pass | ||
| // edition:2018 | ||
|
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| async fn foo(x: &[Vec<u32>]) -> u32 { | ||
| 0 | ||
| } | ||
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| async fn bar() { | ||
| foo(&[vec![123]]).await; | ||
| } | ||
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| fn main() { } |