From bf46b9cb281cd196ca6227b2b72ef64dee390b5a Mon Sep 17 00:00:00 2001 From: Camille GILLOT Date: Sat, 25 Feb 2023 16:29:06 +0000 Subject: Explain that this is UB catching instead of malformed MIR. --- compiler/rustc_const_eval/src/transform/validate.rs | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'compiler/rustc_const_eval/src/transform') diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs index be5b1aad13c..b12a63f23fa 100644 --- a/compiler/rustc_const_eval/src/transform/validate.rs +++ b/compiler/rustc_const_eval/src/transform/validate.rs @@ -756,6 +756,13 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> { } } StatementKind::StorageLive(local) => { + // We check that the local is not live when entering a `StorageLive` for it. + // Technically, violating this restriction is only UB and not actually indicative + // of not well-formed MIR. This means that an optimization which turns MIR that + // already has UB into MIR that fails this check is not necessarily wrong. However, + // we have no such optimizations at the moment, and so we include this check anyway + // to help us catch bugs. If you happen to write an optimization that might cause + // this to incorrectly fire, feel free to remove this check. if self.reachable_blocks.contains(location.block) { self.storage_liveness.seek_before_primary_effect(location); let locals_with_storage = self.storage_liveness.get(); -- cgit 1.4.1-3-g733a5