# Struct rustc_data_structures::unify::UnificationTable

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    pub struct UnificationTable<S>where
        S: UnificationStoreBase,{
        values: S,
    }

Expand description

Table of unification keys and their values. You must define a key type K that implements the `UnifyKey` trait. Unification tables can be used in two-modes:

- in-place (`UnificationTable<InPlace<K>>` or `InPlaceUnificationTable<K>`):
  - This is the standard mutable mode, where the array is modified in place.
  - To do backtracking, you can employ the `snapshot` and `rollback_to` methods.
- persistent (`UnificationTable<Persistent<K>>` or `PersistentUnificationTable<K>`):
  - In this mode, we use a persistent vector to store the data, so that cloning the table is an O(1) operation.
  - This implies that ordinary operations are quite a bit slower though.
  - Requires the `persistent` feature be selected in your Cargo.toml file.

## Fields§

§`values: S`

## Implementations§

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### impl<K> UnificationTable<InPlace<K, Vec<VarValue<K>>, ()>>
where K: UnifyKey,

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#### pub fn with_log<'a, L>( &'a mut self, undo_log: L ) -> UnificationTable<InPlace<K, &'a mut Vec<VarValue<K>>, L>>
where L: UndoLogs<UndoLog<Delegate<K>>>,

Creates a `UnificationTable` using an external `undo_log`, allowing mutating methods to be called if `L` does not implement `UndoLogs`

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### impl<S> UnificationTable<S>
where S: UnificationStoreBase + Default,

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#### pub fn new() -> UnificationTable<S>

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### impl<S> UnificationTable<S>
where S: UnificationStore,

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#### pub fn snapshot(&mut self) -> Snapshot<S>

Starts a new snapshot. Each snapshot must be either rolled back or committed in a “LIFO” (stack) order.

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#### pub fn rollback_to(&mut self, snapshot: Snapshot<S>)

Reverses all changes since the last snapshot. Also removes any keys that have been created since then.

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#### pub fn commit(&mut self, snapshot: Snapshot<S>)

Commits all changes since the last snapshot. Of course, they can still be undone if there is a snapshot further out.

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#### pub fn vars_since_snapshot( &self, snapshot: &Snapshot<S> ) -> Range<<S as UnificationStoreBase>::Key>

Returns the keys of all variables created since the `snapshot`.

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### impl<S> UnificationTable<S>
where S: UnificationStoreBase,

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

Returns the number of keys created so far.

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### impl<S> UnificationTable<S>
where S: UnificationStoreMut,

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#### pub fn new_key( &mut self, value: <S as UnificationStoreBase>::Value ) -> <S as UnificationStoreBase>::Key

Starts a new snapshot. Each snapshot must be either Creates a fresh key with the given value.

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#### pub fn reserve(&mut self, num_new_keys: usize)

Reserve memory for `num_new_keys` to be created. Does not actually create the new keys; you must then invoke `new_key`.

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#### pub fn reset_unifications( &mut self, value: impl FnMut(<S as UnificationStoreBase>::Key) -> <S as UnificationStoreBase>::Value )

Clears all unifications that have been performed, resetting to the initial state. The values of each variable are given by the closure.

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### impl<S, K, V> UnificationTable<S>
where S: UnificationStoreBase<Key = K, Value = V>, K: UnifyKey<Value = V>, V: UnifyValue,

//////////////////////////////////////////////////////////////////////// Public API

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#### pub fn try_probe_value<'a, K1>(&'a self, id: K1) -> Option<&'a V>
where K1: Into<K>, K: 'a,

Obtains current value for key without any pointer chasing; may return `None` if key has been union’d.

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### impl<S, K, V> UnificationTable<S>
where S: UnificationStoreMut<Key = K, Value = V>, K: UnifyKey<Value = V>, V: UnifyValue,

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#### pub fn union<K1, K2>(&mut self, a_id: K1, b_id: K2)
where K1: Into<K>, K2: Into<K>, V: UnifyValue<Error = NoError>,

Unions two keys without the possibility of failure; only applicable when unify values use `NoError` as their error type.

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#### pub fn union_value<K1>(&mut self, id: K1, value: V)
where K1: Into<K>, V: UnifyValue<Error = NoError>,

Unions a key and a value without the possibility of failure; only applicable when unify values use `NoError` as their error type.

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#### pub fn unioned<K1, K2>(&mut self, a_id: K1, b_id: K2) -> bool
where K1: Into<K>, K2: Into<K>,

Given two keys, indicates whether they have been unioned together.

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#### pub fn find<K1>(&mut self, id: K1) -> K
where K1: Into<K>,

Given a key, returns the (current) root key.

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#### pub fn unify_var_var<K1, K2>( &mut self, a_id: K1, b_id: K2 ) -> Result<(), <V as UnifyValue>::Error>
where K1: Into<K>, K2: Into<K>,

Unions together two variables, merging their values. If merging the values fails, the error is propagated and this method has no effect.

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#### pub fn unify_var_value<K1>( &mut self, a_id: K1, b: V ) -> Result<(), <V as UnifyValue>::Error>
where K1: Into<K>,

Sets the value of the key `a_id` to `b`, attempting to merge with the previous value.

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#### pub fn probe_value<K1>(&mut self, id: K1) -> V
where K1: Into<K>,

Returns the current value for the given key. If the key has been union’d, this will give the value from the current root.

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#### pub fn inlined_probe_value<K1>(&mut self, id: K1) -> V
where K1: Into<K>,

## Trait Implementations§

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### impl<S> Clone for UnificationTable<S>
where S: Clone + UnificationStoreBase,

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#### fn clone(&self) -> UnificationTable<S>

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<S> Debug for UnificationTable<S>
where S: Debug + UnificationStoreBase,

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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<S> Default for UnificationTable<S>
where S: Default + UnificationStoreBase,

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#### fn default() -> UnificationTable<S>

Returns the “default value” for a type. Read more

## Auto Trait Implementations§

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### impl<S> DynSend for UnificationTable<S>
where S: DynSend,

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### impl<S> DynSync for UnificationTable<S>
where S: DynSync,

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### impl<S> Freeze for UnificationTable<S>
where S: Freeze,

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### impl<S> RefUnwindSafe for UnificationTable<S>
where S: RefUnwindSafe,

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### impl<S> Send for UnificationTable<S>
where S: Send,

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### impl<S> Sync for UnificationTable<S>
where S: Sync,

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### impl<S> Unpin for UnificationTable<S>
where S: Unpin,

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### impl<S> UnwindSafe for UnificationTable<S>
where S: UnwindSafe,

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment = const ALIGN: Alignment = Alignment::of::<Self>();

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> 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> 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> 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<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.