[beta] Clippy backport#156793
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Fixes rust-lang/rust-clippy#16849 changelog: [`manual_noop_waker`]: Add MSRV check
…t changes runtime behavior. (rust-lang#16878) Closes rust-lang/rust-clippy#16875 ### What was wrong The lint suggested collapsing `pattern => { if test { body } }` into `pattern if test => { body }`. These are not equivalent. In the original, once `pattern` matches, the match exits regardless of `test`. In the suggestion, a failing guard allows fall-through to subsequent arms, which can match values that previously never reached them. ```rust // Before (original) match a { Some(_) => { if b == 0 { res = 1 } } _ if b == 1 => res = 2, // unreachable when a is Some(_) _ => {} } // After (suggestion — WRONG, changes behavior) match a { Some(_) if b == 0 => res = 1, _ if b == 1 => res = 2, // now reachable when a is Some(_) and b != 0 _ => {} } ``` ### Fix The `if`-guard collapsing is only safe when there are no non-wildcard arms between the current arm and the wildcard arm. The fix adds a check that all arms after the current one are "wild-like" (a bare `_`, a binding, or `None`, all without guards) before suggesting the transformation. As a side effect, three `#[expect(clippy::collapsible_match)]` suppressions in `clippy_lints/src/methods/mod.rs` are removed. They had been added to suppress this exact false positive and are no longer needed. ### Still lints correctly When only wildcard arms follow, the transformation is safe and the lint still fires: ```rust // This still lints — only `_ => {}` follows, fall-through is harmless match a { Some(_) => { if b == 0 { res = 1 } // triggers collapsible_match } _ => {} } ``` changelog: [`collapsible_match`]: no longer suggests collapsing `pattern => { if test { body } }` into a match guard when non-wildcard arms follow, as this changes the semantics of the match. <!-- TRIAGEBOT_START --> <!-- TRIAGEBOT_SUMMARY_START --> ### Summary Notes - [Beta-nomination](rust-lang/rust-clippy#16878 (review)) by [samueltardieu](https://github.com/samueltardieu) *Managed by `@rustbot`—see [help](https://forge.rust-lang.org/triagebot/note.html) for details* <!-- TRIAGEBOT_SUMMARY_END --> <!-- TRIAGEBOT_END -->
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The Clippy subtree was changed cc @rust-lang/clippy |
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This was referenced May 21, 2026
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Backporting two fixes in Clippy
manual_noop_wakerrust-clippy#16850collapsible_matchsuggested a transformation that changes runtime behavior. rust-clippy#16878The first one fixes a lint that was added in 1.96.0 (current beta), so that this bug doesn't go to stable. The second one fixes a suggestion that can cause bugs in the code of our users.
Both commits are already on the r-l/r main branch.
r? Mark-Simulacrum