diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs index 068491646f47b..fb37eb79a335f 100644 --- a/compiler/rustc_const_eval/src/transform/validate.rs +++ b/compiler/rustc_const_eval/src/transform/validate.rs @@ -755,8 +755,26 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> { self.fail(location, format!("explicit `{:?}` is forbidden", kind)); } } - StatementKind::StorageLive(..) - | StatementKind::StorageDead(..) + 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(); + if locals_with_storage.contains(*local) { + self.fail( + location, + format!("StorageLive({local:?}) which already has storage here"), + ); + } + } + } + StatementKind::StorageDead(_) | StatementKind::Coverage(_) | StatementKind::ConstEvalCounter | StatementKind::Nop => {} diff --git a/tests/ui/mir/validate/storage-live.rs b/tests/ui/mir/validate/storage-live.rs new file mode 100644 index 0000000000000..ed3c26ed6da5a --- /dev/null +++ b/tests/ui/mir/validate/storage-live.rs @@ -0,0 +1,30 @@ +// compile-flags: -Zvalidate-mir -Ztreat-err-as-bug +// failure-status: 101 +// error-pattern: broken MIR in +// error-pattern: StorageLive(_1) which already has storage here +// normalize-stderr-test "note: .*\n\n" -> "" +// normalize-stderr-test "thread 'rustc' panicked.*\n" -> "" +// normalize-stderr-test "storage_live\[....\]" -> "storage_live[HASH]" +// rustc-env:RUST_BACKTRACE=0 + +#![feature(custom_mir, core_intrinsics)] + +extern crate core; +use core::intrinsics::mir::*; +use core::ptr::{addr_of, addr_of_mut}; + +#[custom_mir(dialect = "built")] +fn multiple_storage() { + mir!( + let a: usize; + { + StorageLive(a); + StorageLive(a); + Return() + } + ) +} + +fn main() { + multiple_storage() +} diff --git a/tests/ui/mir/validate/storage-live.stderr b/tests/ui/mir/validate/storage-live.stderr new file mode 100644 index 0000000000000..b586a8658498f --- /dev/null +++ b/tests/ui/mir/validate/storage-live.stderr @@ -0,0 +1,13 @@ +error: internal compiler error: broken MIR in Item(WithOptConstParam { did: DefId(0:8 ~ storage_live[HASH]::multiple_storage), const_param_did: None }) (before pass CheckPackedRef) at bb0[1]: + StorageLive(_1) which already has storage here + --> $DIR/storage-live.rs:22:13 + | +LL | StorageLive(a); + | ^^^^^^^^^^^^^^ + +error: the compiler unexpectedly panicked. this is a bug. + +query stack during panic: +#0 [mir_const] preparing `multiple_storage` for borrow checking +#1 [mir_promoted] processing MIR for `multiple_storage` +end of query stack