diff options
| -rw-r--r-- | compiler/rustc_hir_typeck/src/gather_locals.rs | 7 | ||||
| -rw-r--r-- | tests/ui/pattern/rfc-3637-guard-patterns/only-gather-locals-once.rs | 15 |
2 files changed, 21 insertions, 1 deletions
diff --git a/compiler/rustc_hir_typeck/src/gather_locals.rs b/compiler/rustc_hir_typeck/src/gather_locals.rs index 956671fc66e..7d99b0e7869 100644 --- a/compiler/rustc_hir_typeck/src/gather_locals.rs +++ b/compiler/rustc_hir_typeck/src/gather_locals.rs @@ -218,7 +218,12 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> { ); } let old_outermost_fn_param_pat = self.outermost_fn_param_pat.take(); - intravisit::walk_pat(self, p); + if let PatKind::Guard(subpat, _) = p.kind { + // We'll visit the guard when checking it. Don't gather its locals twice. + self.visit_pat(subpat); + } else { + intravisit::walk_pat(self, p); + } self.outermost_fn_param_pat = old_outermost_fn_param_pat; } diff --git a/tests/ui/pattern/rfc-3637-guard-patterns/only-gather-locals-once.rs b/tests/ui/pattern/rfc-3637-guard-patterns/only-gather-locals-once.rs new file mode 100644 index 00000000000..7bb39ca7bb9 --- /dev/null +++ b/tests/ui/pattern/rfc-3637-guard-patterns/only-gather-locals-once.rs @@ -0,0 +1,15 @@ +//@ check-pass +//! Test that `GatherLocalsVisitor` only visits expressions in guard patterns when checking the +//! expressions, and not a second time when visiting the pattern. If locals are declared inside the +//! the guard expression, it would ICE if visited twice ("evaluated expression more than once"). + +#![feature(guard_patterns)] +#![expect(incomplete_features)] + +fn main() { + match (0,) { + // FIXME(guard_patterns): liveness lints don't work yet; this will ICE without the `_`. + (_ if { let _x = false; _x },) => {} + _ => {} + } +} |