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Rollup merge of #121391 - Nadrieril:fix-liveness, r=compiler-errors

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never patterns: Fix liveness analysis in the presence of never patterns

There's a bunch of code that only looks at the first alternative of an or-pattern, under the assumption that all alternatives have the same set of bindings. This is true except for never pattern alternatives  (e.g. `Ok(x) | Err(!)`), so we skip these. I expect there's other code with this problem, I'll have to check that later.

I don't have tests for this yet because mir lowering causes other issues; I'll have some in the next PR.

r? ``@compiler-errors``
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Matthias Krüger 2024-02-21 22:48:58 +01:00 • committed by GitHub
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2 changed files with 11 additions and 4 deletions
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4
compiler/rustc_passes/src/liveness.rs
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@ -526,8 +526,8 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
}
fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode {
// In an or-pattern, only consider the first pattern; any later patterns
// must have the same bindings, and we also consider the first pattern
// In an or-pattern, only consider the first non-never pattern; any later patterns
// must have the same bindings, and we also consider that pattern
// to be the "authoritative" set of ids.
pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| {
let ln = self.live_node(hir_id, pat_sp);