diff options
Diffstat (limited to 'compiler/rustc_abi/src/lib.rs')
| -rw-r--r-- | compiler/rustc_abi/src/lib.rs | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs index 39574ca558f..6740001c38b 100644 --- a/compiler/rustc_abi/src/lib.rs +++ b/compiler/rustc_abi/src/lib.rs @@ -1380,8 +1380,21 @@ impl Niche { } rustc_index::newtype_index! { + /// The *source-order* index of a variant in a type. + /// + /// For enums, these are always `0..variant_count`, regardless of any + /// custom discriminants that may have been defined, and including any + /// variants that may end up uninhabited due to field types. (Some of the + /// variants may not be present in a monomorphized ABI [`Variants`], but + /// those skipped variants are always counted when determining the *index*.) + /// + /// `struct`s, `tuples`, and `unions`s are considered to have a single variant + /// with variant index zero, aka [`FIRST_VARIANT`]. #[derive(HashStable_Generic)] - pub struct VariantIdx {} + pub struct VariantIdx { + /// Equivalent to `VariantIdx(0)`. + const FIRST_VARIANT = 0; + } } #[derive(PartialEq, Eq, Hash, Clone)] @@ -1422,7 +1435,7 @@ impl LayoutS { let size = scalar.size(cx); let align = scalar.align(cx); LayoutS { - variants: Variants::Single { index: VariantIdx::new(0) }, + variants: Variants::Single { index: FIRST_VARIANT }, fields: FieldsShape::Primitive, abi: Abi::Scalar(scalar), largest_niche, |