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Rollup merge of #92237 - compiler-errors:issue-92100, r=cjgillot

Visit expressions in-order when resolving pattern bindings

[edited:] Visit the pattern's sub-expressions before defining any bindings.

Otherwise, we might get into a case where a Lit/Range expression in a pattern has a qpath pointing to a Ident pattern that is defined after it, causing an ICE when lowering to HIR. I have a more detailed explanation in the issue linked.

Fixes #92100
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Matthias Krüger 2021-12-29 10:17:10 +01:00 committed by GitHub
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5 changed files with 50 additions and 1 deletions

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@ -1603,10 +1603,13 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
pat_src: PatternSource,
bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
) {
// We walk the pattern before declaring the pattern's inner bindings,
// so that we avoid resolving a literal expression to a binding defined
// by the pattern.
visit::walk_pat(self, pat);
self.resolve_pattern_inner(pat, pat_src, bindings);
// This has to happen *after* we determine which pat_idents are variants:
self.check_consistent_bindings_top(pat);
visit::walk_pat(self, pat);
}
/// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.