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Rollup merge of #125616 - RalfJung:mir-validate-downcast-projection, r=compiler-errors

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MIR validation: ensure that downcast projection is followed by field projection

Cc https://github.com/rust-lang/rust/issues/120369
This commit is contained in:
Matthias Krüger 2024-05-27 20:43:26 +02:00 • committed by GitHub
commit 61f9d35798
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3 changed files with 26 additions and 6 deletions
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26
compiler/rustc_mir_transform/src/validate.rs
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@ -689,8 +689,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
if Some(adt_def.did()) == self.tcx.lang_items().dyn_metadata() {
self.fail(
location,
format!("You can't project to field {f:?} of `DynMetadata` because \
layout is weird and thinks it doesn't have fields."),
format!(
"You can't project to field {f:?} of `DynMetadata` because \
layout is weird and thinks it doesn't have fields."
),
);
}
@ -839,7 +841,25 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
&& cntxt != PlaceContext::NonUse(NonUseContext::VarDebugInfo)
&& place.projection[1..].contains(&ProjectionElem::Deref)
{
self.fail(location, format!("{place:?}, has deref at the wrong place"));
self.fail(
location,
format!("place {place:?} has deref as a later projection (it is only permitted as the first projection)"),
);
}
// Ensure all downcast projections are followed by field projections.
let mut projections_iter = place.projection.iter();
while let Some(proj) = projections_iter.next() {
if matches!(proj, ProjectionElem::Downcast(..)) {
if !matches!(projections_iter.next(), Some(ProjectionElem::Field(..))) {
self.fail(
location,
format!(
"place {place:?} has `Downcast` projection not followed by `Field`"
),
);
}
}
}
self.super_place(place, cntxt, location);