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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 <[email protected]>
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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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// 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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// 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() { } |