Enum rustc_abi::TagEncoding
source · pub enum TagEncoding<VariantIdx: Idx> {
Direct,
Niche {
untagged_variant: VariantIdx,
niche_variants: RangeInclusive<VariantIdx>,
niche_start: u128,
},
}
Variants§
Direct
The tag directly stores the discriminant, but possibly with a smaller layout (so converting the tag to the discriminant can require sign extension).
Niche
Niche (values invalid for a type) encoding the discriminant:
Discriminant and variant index coincide.
The variant untagged_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).
Trait Implementations§
source§impl<VariantIdx: Clone + Idx> Clone for TagEncoding<VariantIdx>
impl<VariantIdx: Clone + Idx> Clone for TagEncoding<VariantIdx>
source§fn clone(&self) -> TagEncoding<VariantIdx>
fn clone(&self) -> TagEncoding<VariantIdx>
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl<VariantIdx, __CTX> HashStable<__CTX> for TagEncoding<VariantIdx>
impl<VariantIdx, __CTX> HashStable<__CTX> for TagEncoding<VariantIdx>
fn hash_stable(&self, __hcx: &mut __CTX, __hasher: &mut StableHasher)
impl<VariantIdx: Eq + Idx> Eq for TagEncoding<VariantIdx>
impl<VariantIdx: Idx> StructuralPartialEq for TagEncoding<VariantIdx>
Auto Trait Implementations§
impl<VariantIdx> Freeze for TagEncoding<VariantIdx>where
VariantIdx: Freeze,
impl<VariantIdx> RefUnwindSafe for TagEncoding<VariantIdx>where
VariantIdx: RefUnwindSafe,
impl<VariantIdx> Send for TagEncoding<VariantIdx>where
VariantIdx: Send,
impl<VariantIdx> Sync for TagEncoding<VariantIdx>where
VariantIdx: Sync,
impl<VariantIdx> Unpin for TagEncoding<VariantIdx>where
VariantIdx: Unpin,
impl<VariantIdx> UnwindSafe for TagEncoding<VariantIdx>where
VariantIdx: UnwindSafe,
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§unsafe fn clone_to_uninit(&self, dst: *mut T)
unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)source§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
source§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
source§impl<Q, K> Equivalent<K> for Q
impl<Q, K> Equivalent<K> for Q
source§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.source§impl<T> Instrument for T
impl<T> Instrument for T
source§fn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
source§fn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
source§impl<T> IntoEither for T
impl<T> IntoEither for T
source§fn into_either(self, into_left: bool) -> Either<Self, Self>
fn into_either(self, into_left: bool) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left
is true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read moresource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left(&self)
returns true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read moresource§impl<T> WithSubscriber for T
impl<T> WithSubscriber for T
source§fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
source§fn with_current_subscriber(self) -> WithDispatch<Self>
fn with_current_subscriber(self) -> WithDispatch<Self>
impl<'a, T> Captures<'a> for Twhere
T: ?Sized,
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.