[][src]Enum rustc_target::abi::TagEncoding

pub enum TagEncoding {
    Niche {
        dataful_variant: VariantIdx,
        niche_variants: RangeInclusive<VariantIdx>,
        niche_start: u128,



The tag directly stores the discriminant, but possibly with a smaller layout (so converting the tag to the discriminant can require sign extension).


Niche (values invalid for a type) encoding the discriminant: Discriminant and variant index coincide. The variant dataful_variant contains a niche at an arbitrary offset (field tag_field of the enum), which for a variant with discriminant d is set to (d - niche_variants.start).wrapping_add(niche_start).

For example, Option<(usize, &T)> is represented such that None has a null pointer for the second tuple field, and Some is the identity function (with a non-null reference).

Fields of Niche

dataful_variant: VariantIdxniche_variants: RangeInclusive<VariantIdx>niche_start: u128

Trait Implementations

impl Debug for TagEncoding[src]

impl Eq for TagEncoding[src]

impl Hash for TagEncoding[src]

impl<__CTX> HashStable<__CTX> for TagEncoding where
    __CTX: HashStableContext

impl PartialEq<TagEncoding> for TagEncoding[src]

impl StructuralEq for TagEncoding[src]

impl StructuralPartialEq for TagEncoding[src]

Auto Trait Implementations

impl RefUnwindSafe for TagEncoding

impl Send for TagEncoding

impl Sync for TagEncoding

impl Unpin for TagEncoding

impl UnwindSafe for TagEncoding

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized

impl<T> Borrow<T> for T where
    T: ?Sized

impl<T> BorrowMut<T> for T where
    T: ?Sized

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 

impl<T> MaybeResult<T> for T[src]

type Error = !

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.