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fix getting the discriminant of a zero-variant enum

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This commit is contained in:
Ralf Jung 2021-11-14 13:28:47 -05:00
parent c8e94975a6
commit eebf676bf8
2 changed files with 9 additions and 1 deletions
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4
compiler/rustc_middle/src/ty/sty.rs
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@ -2067,7 +2067,9 @@ impl<'tcx> TyS<'tcx> {
) -> Option<Discr<'tcx>> { ) -> Option<Discr<'tcx>> {
match self.kind() { match self.kind() {
TyKind::Adt(adt, _) if adt.variants.is_empty() => { TyKind::Adt(adt, _) if adt.variants.is_empty() => {
bug!("discriminant_for_variant called on zero variant enum"); // This can actually happen during CTFE, see
// https://github.com/rust-lang/rust/issues/89765.
None
} }
TyKind::Adt(adt, _) if adt.is_enum() => { TyKind::Adt(adt, _) if adt.is_enum() => {
Some(adt.discriminant_for_variant(tcx, variant_index)) Some(adt.discriminant_for_variant(tcx, variant_index))

6
src/test/ui/consts/const_discriminant.rs
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@ -25,6 +25,12 @@ enum SingleVariant {
const TEST_V: Discriminant<SingleVariant> = discriminant(&SingleVariant::V); const TEST_V: Discriminant<SingleVariant> = discriminant(&SingleVariant::V);
pub const TEST_VOID: () = {
// This is UB, but CTFE does not check validity so it does not detect this.
unsafe { std::mem::discriminant(&*(&() as *const () as *const Void)); };
};
fn main() { fn main() {
assert_eq!(TEST_A, TEST_A_OTHER); assert_eq!(TEST_A, TEST_A_OTHER);
assert_eq!(TEST_A, discriminant(black_box(&Test::A(17)))); assert_eq!(TEST_A, discriminant(black_box(&Test::A(17))));