Skip to content

fix getting the discriminant of a zero-variant enum #90910

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Nov 16, 2021
Merged

fix getting the discriminant of a zero-variant enum #90910

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
eebf676
fix getting the discriminant of a zero-variant enum
RalfJung Nov 14, 2021
9ec8862
expand comment
RalfJung Nov 15, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 3 additions & 1 deletion compiler/rustc_middle/src/ty/sty.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2067,7 +2067,9 @@ impl<'tcx> TyS<'tcx> {
) -> Option<Discr<'tcx>> {
match self.kind() {
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() => {
Some(adt.discriminant_for_variant(tcx, variant_index))
Expand Down
7 changes: 7 additions & 0 deletions src/test/ui/consts/const_discriminant.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,13 @@ enum SingleVariant {

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.
// This is a regression test for https://github.com/rust-lang/rust/issues/89765.
unsafe { std::mem::discriminant(&*(&() as *const () as *const Void)); };
};


fn main() {
assert_eq!(TEST_A, TEST_A_OTHER);
assert_eq!(TEST_A, discriminant(black_box(&Test::A(17))));
Expand Down