Enum rustc_target::abi::Variants

pub enum Variants<FieldIdx, VariantIdx>where
    FieldIdx: Idx,
    VariantIdx: Idx,{
    Single {
        index: VariantIdx,
    },
    Multiple {
        tag: Scalar,
        tag_encoding: TagEncoding<VariantIdx>,
        tag_field: usize,
        variants: IndexVec<VariantIdx, LayoutS<FieldIdx, VariantIdx>>,
    },
}

Variants

Single

Fields

index: VariantIdx

Single enum variants, structs/tuples, unions, and all non-ADTs.

Multiple

Fields

tag: Scalar

tag_encoding: TagEncoding<VariantIdx>

tag_field: usize

variants: IndexVec<VariantIdx, LayoutS<FieldIdx, VariantIdx>>

Enum-likes with more than one inhabited variant: each variant comes with a discriminant (usually the same as the variant index but the user can assign explicit discriminant values). That discriminant is encoded as a tag on the machine. The layout of each variant is a struct, and they all have space reserved for the tag. For enums, the tag is the sole field of the layout.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.