Struct rustc_data_structures::unify::UnificationTable

pub struct UnificationTable<S> where
    S: UnificationStore,  { /* fields omitted */ }

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.

Methods

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

pub fn new() -> UnificationTable<S>

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.

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.

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.

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

Creates a fresh key with the given value.

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.

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

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

pub fn len(&self) -> usize

Returns the number of keys created so far.

Important traits for Range<A>

impl<A> Iterator for Range<A> where
    A: Step,  type Item = A;

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

Returns the keys of all variables created since the snapshot.

impl<'tcx, S, K, V> UnificationTable<S> where
    K: UnifyKey<Value = V>,
    S: UnificationStore<Key = K, Value = V>,
    V: UnifyValue, 

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

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.

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.

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.

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

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

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.

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.

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.

Trait Implementations

impl<S> Clone for UnificationTable<S> where
    S: UnificationStore + Clone, 

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

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<S> Debug for UnificationTable<S> where
    S: UnificationStore + Debug, 

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

Formats the value using the given formatter.

impl<S> Default for UnificationTable<S> where
    S: UnificationStore + Default, 

fn default() -> UnificationTable<S>

Returns the "default value" for a type.