Enum rustc_target::abi::TagEncoding

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pub enum TagEncoding<VariantIdx>
where VariantIdx: Idx,
{ Direct, Niche { untagged_variant: VariantIdx, niche_variants: RangeInclusive<VariantIdx>, niche_start: u128, }, }

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Direct

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

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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).

Fields

§untagged_variant: VariantIdx
§niche_variants: RangeInclusive<VariantIdx>
§niche_start: u128

Trait Implementations§

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impl<VariantIdx> Clone for TagEncoding<VariantIdx>
where VariantIdx: Clone + Idx,

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fn clone(&self) -> TagEncoding<VariantIdx>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<VariantIdx> Debug for TagEncoding<VariantIdx>
where VariantIdx: Debug + Idx,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<VariantIdx> Hash for TagEncoding<VariantIdx>
where VariantIdx: Hash + Idx,

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fn hash<__H>(&self, state: &mut __H)
where __H: Hasher,

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl<VariantIdx, __CTX> HashStable<__CTX> for TagEncoding<VariantIdx>
where VariantIdx: Idx + HashStable<__CTX>, __CTX: HashStableContext,

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fn hash_stable(&self, __hcx: &mut __CTX, __hasher: &mut StableHasher)

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impl<VariantIdx> PartialEq for TagEncoding<VariantIdx>
where VariantIdx: PartialEq + Idx,

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fn eq(&self, other: &TagEncoding<VariantIdx>) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<VariantIdx> Eq for TagEncoding<VariantIdx>
where VariantIdx: Eq + Idx,

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impl<VariantIdx> StructuralPartialEq for TagEncoding<VariantIdx>
where VariantIdx: Idx,

Auto Trait Implementations§

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impl<VariantIdx> Freeze for TagEncoding<VariantIdx>
where VariantIdx: Freeze,

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impl<VariantIdx> RefUnwindSafe for TagEncoding<VariantIdx>
where VariantIdx: RefUnwindSafe,

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impl<VariantIdx> Send for TagEncoding<VariantIdx>
where VariantIdx: Send,

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impl<VariantIdx> Sync for TagEncoding<VariantIdx>
where VariantIdx: Sync,

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impl<VariantIdx> Unpin for TagEncoding<VariantIdx>
where VariantIdx: Unpin,

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impl<VariantIdx> UnwindSafe for TagEncoding<VariantIdx>
where VariantIdx: UnwindSafe,

Blanket Implementations§

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impl<T> Aligned for T

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const ALIGN: Alignment = _

Alignment of Self.
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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<'a, T> Captures<'a> for T
where 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.