# Struct rustc_infer::infer::type_variable::TypeVariableTable

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    pub struct TypeVariableTable<'a, 'tcx> {
        storage: &'a mut TypeVariableStorage<'tcx>,
        undo_log: &'a mut InferCtxtUndoLogs<'tcx>,
    }

## Fields§

§`storage: &'a mut TypeVariableStorage<'tcx>`§`undo_log: &'a mut InferCtxtUndoLogs<'tcx>`

## Implementations§

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### impl<'tcx> TypeVariableTable<'_, 'tcx>

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#### pub fn var_origin(&self, vid: TyVid) -> TypeVariableOrigin

Returns the origin that was given when `vid` was created.

Note that this function does not return care whether `vid` has been unified with something else or not.

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#### pub fn equate(&mut self, a: TyVid, b: TyVid)

Records that `a == b`, depending on `dir`.

Precondition: neither `a` nor `b` are known.

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#### pub fn sub(&mut self, a: TyVid, b: TyVid)

Records that `a <: b`, depending on `dir`.

Precondition: neither `a` nor `b` are known.

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#### pub fn instantiate(&mut self, vid: TyVid, ty: Ty<'tcx>)

Instantiates `vid` with the type `ty`.

Precondition: `vid` must not have been previously instantiated.

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#### pub fn new_var( &mut self, universe: UniverseIndex, origin: TypeVariableOrigin ) -> TyVid

Creates a new type variable.

- `diverging`: indicates if this is a “diverging” type variable, e.g., one created as the type of a `return` expression. The code in this module doesn’t care if a variable is diverging, but the main Rust type-checker will sometimes “unify” such variables with the `!` or `()` types.
- `origin`: indicates why the type variable was created. The code in this module doesn’t care, but it can be useful for improving error messages.

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#### pub fn num_vars(&self) -> usize

Returns the number of type variables created thus far.

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#### pub fn root_var(&mut self, vid: TyVid) -> TyVid

Returns the “root” variable of `vid` in the `eq_relations` equivalence table. All type variables that have been equated will yield the same root variable (per the union-find algorithm), so `root_var(a) == root_var(b)` implies that `a == b` (transitively).

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#### pub fn sub_root_var(&mut self, vid: TyVid) -> TyVid

Returns the “root” variable of `vid` in the `sub_relations` equivalence table. All type variables that have been are related via equality or subtyping will yield the same root variable (per the union-find algorithm), so `sub_root_var(a) == sub_root_var(b)` implies that:

    exists X. (a <: X || X <: a) && (b <: X || X <: b)

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#### pub fn sub_unified(&mut self, a: TyVid, b: TyVid) -> bool

Returns `true` if `a` and `b` have same “sub-root” (i.e., exists some type X such that `forall i in {a, b}. (i <: X || X <: i)`.

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#### pub fn probe(&mut self, vid: TyVid) -> TypeVariableValue<'tcx>

Retrieves the type to which `vid` has been instantiated, if any.

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#### pub fn inlined_probe(&mut self, vid: TyVid) -> TypeVariableValue<'tcx>

An always-inlined variant of `probe`, for very hot call sites.

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#### pub fn replace_if_possible(&mut self, t: Ty<'tcx>) -> Ty<'tcx>

If `t` is a type-inference variable, and it has been instantiated, then return the with which it was instantiated. Otherwise, returns `t`.

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#### fn eq_relations( &mut self ) -> UnificationTable<InPlace<TyVidEqKey<'tcx>, &'_ mut UnificationStorage<TyVidEqKey<'tcx>>, &'_ mut InferCtxtUndoLogs<'tcx>>>

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#### fn sub_relations( &mut self ) -> UnificationTable<InPlace<TyVid, &'_ mut UnificationStorage<TyVid>, &'_ mut InferCtxtUndoLogs<'tcx>>>

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#### pub fn vars_since_snapshot( &mut self, value_count: usize ) -> (Range<TyVid>, Vec<TypeVariableOrigin>)

Returns a range of the type variables created during the snapshot.

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#### pub fn unresolved_variables(&mut self) -> Vec<TyVid>

Returns indices of all variables that are not yet instantiated.

## Auto Trait Implementations§

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### impl<'a, 'tcx> !RefUnwindSafe for TypeVariableTable<'a, 'tcx>

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### impl<'a, 'tcx> Send for TypeVariableTable<'a, 'tcx>

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### impl<'a, 'tcx> Sync for TypeVariableTable<'a, 'tcx>

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### impl<'a, 'tcx> Unpin for TypeVariableTable<'a, 'tcx>

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### impl<'a, 'tcx> !UnwindSafe for TypeVariableTable<'a, 'tcx>

## Blanket Implementations§

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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> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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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, 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.

## 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: 16 bytes