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avoid downcasting for enum variants without further fields

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Ralf Jung
2017-06-19 23:49:57 -07:00
committed by Oliver Schneider
parent a91ee4bb03
commit fda5cc9b4c
1 changed files with 11 additions and 6 deletions
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src/librustc_mir/interpret/lvalue.rs
+11 -6
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@@ -561,13 +561,18 @@ pub(super) fn acquire_valid(&mut self, lvalue: Lvalue<'tcx>, ty: Ty<'tcx>, outer
let variant_idx = adt.discriminants(self.tcx)
.position(|variant_discr| variant_discr.to_u128_unchecked() == discr)
.ok_or(EvalError::InvalidDiscriminant)?;
// Downcast to this variant
let lvalue = self.eval_lvalue_projection(lvalue, ty, &mir::ProjectionElem::Downcast(adt, variant_idx))?;
// Recursively validate the fields
let variant = &adt.variants[variant_idx];
self.validate_variant(lvalue, ty, variant, subst, outer_mutbl)
if variant.fields.len() > 0 {
// Downcast to this variant
let lvalue = self.eval_lvalue_projection(lvalue, ty, &mir::ProjectionElem::Downcast(adt, variant_idx))?;
// Recursively validate the fields
self.validate_variant(lvalue, ty, variant, subst, outer_mutbl)
} else {
// No fields, nothing left to check. Downcasting may fail, e.g. in case of a CEnum.
Ok(())
}
}
AdtKind::Struct => {
self.validate_variant(lvalue, ty, adt.struct_variant(), subst, outer_mutbl)