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implement StructuralPartialEq for MaybeDangling#154891

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WaffleLapkin wants to merge 1 commit intorust-lang:mainfrom
WaffleLapkin:deregress-manually-drop-matching
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implement StructuralPartialEq for MaybeDangling#154891
WaffleLapkin wants to merge 1 commit intorust-lang:mainfrom
WaffleLapkin:deregress-manually-drop-matching

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@WaffleLapkin WaffleLapkin commented Apr 6, 2026 •
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This fixes -- a stable-to-stable regression where constants of type ManuallyDrop<T> would not be allowed to be used as a pattern due to MaybeDangling<T> in ManuallyDrop<T> not implementing StructuralPartialEq.

Fixes #154890

I'm sorry, @theemathas, I forgot to address your comment 😭

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 6, 2026
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rustbot commented Apr 6, 2026

r? @JohnTitor

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r=me once CI passes

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@WaffleLapkin
implement StructuralPartialEq for MaybeDangling
d5f98fb 
This fixes a stable-to-stable regression where constants of type
`ManuallyDrop<T>` would not be allowed to be used as a pattern due to
`MaybeDangling<T>` in `ManuallyDrop<T>` not implementing
`StructuralPartialEq`.
@WaffleLapkin WaffleLapkin force-pushed the deregress-manually-drop-matching branch from 68bcf7c to d5f98fb Compare April 6, 2026 16:19
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Jules-Bertholet commented Apr 6, 2026

Why not just derive(PartialEq, Eq, PartialOrd, Ord, Hash) for MaybeDangling? That way, ManuallyDrop can revert to derived impls also.

@Jules-Bertholet Jules-Bertholet mentioned this pull request Apr 6, 2026
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Jules-Bertholet commented Apr 6, 2026

Filed a PR: #154905

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WaffleLapkin commented Apr 6, 2026

@bors r=JohnTitor

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rust-bors bot commented Apr 6, 2026

📌 Commit d5f98fb has been approved by JohnTitor

It is now in the queue for this repository.

@rust-bors rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 6, 2026
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ManuallyDrop can't be used as a constant in match since 1.94

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