## TypeVariableStorage

# Struct TypeVariableStorage

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    pub(crate) struct TypeVariableStorage<'tcx> {
        values: IndexVec<TyVid, TypeVariableData>,
        eq_relations: UnificationTableStorage<TyVidEqKey<'tcx>>,
        sub_unification_table: UnificationTableStorage<TyVidSubKey>,
    }

## Fields§

§`values: IndexVec<TyVid, TypeVariableData>`

The origins of each type variable.

§`eq_relations: UnificationTableStorage<TyVidEqKey<'tcx>>`

Two variables are unified in `eq_relations` when we have a constraint `?X == ?Y`. This table also stores, for each key, the known value.

§`sub_unification_table: UnificationTableStorage<TyVidSubKey>`

Only used by `-Znext-solver` and for diagnostics. Tracks whether type variables are related via subtyping at all, ignoring which of the two is the subtype.

When reporting ambiguity errors, we sometimes want to treat all inference vars which are subtypes of each others as if they are equal. For this case we compute the transitive closure of our subtype obligations here.

E.g. when encountering ambiguity errors, we want to suggest specifying some method argument or to add a type annotation to a local variable. Because subtyping cannot change the shape of a type, it’s fine if the cause of the ambiguity error is only related to the suggested variable via subtyping.

Even for something like `let x = returns_arg(); x.method();` the type of `x` is only a supertype of the argument of `returns_arg`. We still want to suggest specifying the type of the argument.

## Implementations§

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### impl<'tcx> TypeVariableStorage<'tcx>

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#### pub(crate) fn with_log<'a>( &'a mut self, undo_log: &'a mut InferCtxtUndoLogs<'tcx>, ) -> TypeVariableTable<'a, 'tcx>

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#### pub(crate) fn eq_relations_ref( &self, ) -> &UnificationTableStorage<TyVidEqKey<'tcx>>

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#### pub(super) fn finalize_rollback(&mut self)

## Trait Implementations§

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### impl<'tcx> Clone for TypeVariableStorage<'tcx>

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#### fn clone(&self) -> TypeVariableStorage<'tcx>

Returns a duplicate 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<'tcx> Default for TypeVariableStorage<'tcx>

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#### fn default() -> TypeVariableStorage<'tcx>

Returns the “default value” for a type. Read more
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### impl<'tcx> Rollback<UndoLog<'tcx>> for TypeVariableStorage<'tcx>

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#### fn reverse(&mut self, undo: UndoLog<'tcx>)

## Auto Trait Implementations§

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### impl<'tcx> DynSend for TypeVariableStorage<'tcx>

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### impl<'tcx> DynSync for TypeVariableStorage<'tcx>

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### impl<'tcx> Freeze for TypeVariableStorage<'tcx>

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### impl<'tcx> !RefUnwindSafe for TypeVariableStorage<'tcx>

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### impl<'tcx> Send for TypeVariableStorage<'tcx>

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### impl<'tcx> Sync for TypeVariableStorage<'tcx>

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### impl<'tcx> Unpin for TypeVariableStorage<'tcx>

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### impl<'tcx> !UnwindSafe for TypeVariableStorage<'tcx>

## 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<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T, R> CollectAndApply<T, R> for T

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#### fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to `f(&iter.collect::<Vec<_>>())`.

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#### type Output = R

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### impl<T> DynClone for T
where T: Clone,

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#### fn __clone_box(&self, _: Private) -> *mut ()

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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> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `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 more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `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 more
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### impl<P> IntoQueryParam<P> for P

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#### fn into_query_param(self) -> P

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### impl<T> MaybeResult<T> for T

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#### type Error = !

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#### fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

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#### fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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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<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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#### fn upcast(self, interner: I) -> U

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### impl<I, T> UpcastFrom<I, T> for T

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#### fn upcast_from(from: T, _tcx: I) -> T

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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<Tcx, T> Value<Tcx> for T
where Tcx: DepContext,

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#### default fn from_cycle_error( tcx: Tcx, cycle_error: &CycleError, _guar: ErrorGuaranteed, ) -> T

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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<T> ErasedDestructor for T
where T: 'static,

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 72 bytes