bjoernager/rust
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Variants::Single: do not use invalid VariantIdx for uninhabited enums

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This commit is contained in:
Ralf Jung 2024-12-01 13:12:43 +01:00
parent 37e74596c0
commit 21de42bf8d
47 changed files with 549 additions and 281 deletions
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23
compiler/rustc_const_eval/src/interpret/discriminant.rs
View file

@ -44,7 +44,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
}
}
/// Read discriminant, return the runtime value as well as the variant index.
/// Read discriminant, return the variant index.
/// Can also legally be called on non-enums (e.g. through the discriminant_value intrinsic)!
///
/// Will never return an uninhabited variant.
@ -66,21 +66,14 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
// straight-forward (`TagEncoding::Direct`) or with a niche (`TagEncoding::Niche`).
let (tag_scalar_layout, tag_encoding, tag_field) = match op.layout().variants {
Variants::Single { index } => {
// Do some extra checks on enums.
if ty.is_enum() {
// Hilariously, `Single` is used even for 0-variant enums.
// (See https://github.com/rust-lang/rust/issues/89765).
if ty.ty_adt_def().unwrap().variants().is_empty() {
throw_ub!(UninhabitedEnumVariantRead(index))
}
if op.layout().is_uninhabited() {
// For consistency with `write_discriminant`, and to make sure that
// `project_downcast` cannot fail due to strange layouts, we declare immediate UB
// for uninhabited variants.
if op.layout().for_variant(self, index).is_uninhabited() {
throw_ub!(UninhabitedEnumVariantRead(index))
}
// for uninhabited enums.
throw_ub!(UninhabitedEnumVariantRead(None));
}
return interp_ok(index);
// Since the type is inhabited, there must be an index.
return interp_ok(index.unwrap());
}
Variants::Multiple { tag, ref tag_encoding, tag_field, .. } => {
(tag, tag_encoding, tag_field)
@ -199,11 +192,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
// `uninhabited_enum_branching` MIR pass. It also ensures consistency with
// `write_discriminant`.
if op.layout().for_variant(self, index).is_uninhabited() {
throw_ub!(UninhabitedEnumVariantRead(index))
throw_ub!(UninhabitedEnumVariantRead(Some(index)))
}
interp_ok(index)
}
/// Read discriminant, return the user-visible discriminant.
/// Can also legally be called on non-enums (e.g. through the discriminant_value intrinsic)!
pub fn discriminant_for_variant(
&self,
ty: Ty<'tcx>,

4
compiler/rustc_const_eval/src/interpret/validity.rs
View file

@ -342,7 +342,9 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
match layout.variants {
Variants::Single { index } => {
// Inside a variant
PathElem::Field(def.variant(index).fields[FieldIdx::from_usize(field)].name)
PathElem::Field(
def.variant(index.unwrap()).fields[FieldIdx::from_usize(field)].name,
)
}
Variants::Multiple { .. } => bug!("we handled variants above"),
}