Add test for async Send with PhantomData<*mut ()> + unsafe impl Send + dyn Trait#154398
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r? @jackh726 rustbot has assigned @jackh726. Use Why was this reviewer chosen?The reviewer was selected based on:
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So, see this comment: commit message needs to be updated. Otherwise, r=me |
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…impl Send + dyn Trait Add a regression test covering the case where a type uses PhantomData<*mut ()> to opt out of Sync, restores Send via an unsafe impl, and is then captured across an .await point with a trait object type parameter (Box<dyn Trait>). The compiler currently erases lifetimes in MIR coroutine witnesses, losing the 'static bound needed to apply the unsafe impl Send. The test verifies this is fixed by -Zhigher-ranked-assumptions and documents the PhantomData<Cell<()>> workaround as a comparison. See the PR description for links to the relevant issues. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
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@jackh726 commit message updated to resolve the notice. |
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Add a regression test for #154397, covering the case where:
PhantomData<*mut ()>to opt out ofSyncSendis restored viaunsafe impl<T: Send + 'static> Send.awaitin an async blockBox<dyn Trait>)This is an instance of #110338. The test includes both revisions:
assumptions: compiles with-Zhigher-ranked-assumptions(check-pass)no_assumptions: documents the current failure as a known-bugAlso includes a
PhantomData<Cell<()>>comparison showing the workaround compiles in all cases.