Type Alias Binders

pub type Binders<T> = Binders<T>;

Represents generic parameters and an item bound by them. When the item has parent, the binders also contain the generic parameters for its parent. See chalk’s documentation for details.

One thing to keep in mind when working with Binders (and Substitutions, which represent generic arguments) in rust-analyzer is that the ordering within is significant - the generic parameters/arguments for an item MUST come before those for its parent. This is to facilitate the integration with chalk-solve, which mildly puts constraints as such. See #13335 for its motivation in detail.

Aliased Type

struct Binders<T> {
    pub binders: VariableKinds<<T as HasInterner>::Interner>,
    /* private fields */
}

Fields

binders: VariableKinds<<T as HasInterner>::Interner>

The binders that quantify over the value.

Implementations

impl<T> Binders<&T>

where T: Clone + HasInterner,

pub fn cloned(self) -> Binders<T>

Converts a Binders<&T> to a Binders<T> by cloning T.

impl<T, I> Binders<Binders<T>>

where T: TypeFoldable<I> + HasInterner<Interner = I>, I: Interner,

pub fn fuse_binders(self, interner: <T as HasInterner>::Interner) -> Binders<T>

This turns two levels of binders (for<A> for<B>) into one level (for<A, B>).

impl<T> Binders<T>

where T: HasInterner,

pub fn new( binders: VariableKinds<<T as HasInterner>::Interner>, value: T, ) -> Binders<T>

Create new binders.

pub fn empty(interner: <T as HasInterner>::Interner, value: T) -> Binders<T>

Wraps the given value in a binder without variables, i.e. for<> (value). Since our deBruijn indices count binders, not variables, this is sometimes useful.

pub fn skip_binders(&self) -> &T

Skips the binder and returns the “bound” value. This is a risky thing to do because it’s easy to get confused about De Bruijn indices and the like. skip_binder is only valid when you are either extracting data that has nothing to do with bound vars, or you are being very careful about your depth accounting.

Some examples where skip_binder is reasonable:

• extracting the TraitId from a TraitRef;
• checking if there are any fields in a StructDatum

pub fn into_value_and_skipped_binders( self, ) -> (T, VariableKinds<<T as HasInterner>::Interner>)

Skips the binder and returns the “bound” value as well as the skipped free variables. This is just as risky as [skip_binders][Self::skip_binders].

pub fn as_ref(&self) -> Binders<&T>

Converts &Binders<T> to Binders<&T>. Produces new Binders with cloned quantifiers containing a reference to the original value, leaving the original in place.

pub fn map<U, OP>(self, op: OP) -> Binders<U>

where OP: FnOnce(T) -> U, U: HasInterner<Interner = <T as HasInterner>::Interner>,

Maps the binders by applying a function.

pub fn filter_map<U, OP>(self, op: OP) -> Option<Binders<U>>

where OP: FnOnce(T) -> Option<U>, U: HasInterner<Interner = <T as HasInterner>::Interner>,

Transforms the inner value according to the given function; returns None if the function returns None.

pub fn map_ref<'a, U, OP>(&'a self, op: OP) -> Binders<U>

where OP: FnOnce(&'a T) -> U, U: HasInterner<Interner = <T as HasInterner>::Interner>,

Maps a function taking Binders<&T> over &Binders<T>.

pub fn identity_substitution( &self, interner: <T as HasInterner>::Interner, ) -> Substitution<<T as HasInterner>::Interner>

Creates a Substitution containing bound vars such that applying this substitution will not change the value, i.e. ^0.0, ^0.1, ^0.2 and so on.

pub fn with_fresh_type_var( interner: <T as HasInterner>::Interner, op: impl FnOnce(Ty<<T as HasInterner>::Interner>) -> T, ) -> Binders<T>

Creates a fresh binders that contains a single type variable. The result of the closure will be embedded in this binder. Note that you should be careful with what you return from the closure to account for the binder that will be added.

XXX FIXME – this is potentially a pretty footgun-y function.

pub fn len(&self, interner: <T as HasInterner>::Interner) -> usize

Returns the number of binders.

impl<T, I> Binders<T>

where T: TypeFoldable<I> + HasInterner<Interner = I>, I: Interner,

pub fn substitute( self, interner: I, parameters: &(impl AsParameters<I> + ?Sized), ) -> T

Substitute parameters for the variables introduced by these binders. So if the binders represent (e.g.) <X, Y> { T } and parameters is the slice [A, B], then returns [X => A, Y => B] T.

impl<I> Binders<WhereClause<I>>

where I: Interner,

pub fn into_well_formed_goal(self, interner: I) -> Binders<DomainGoal<I>>

As with WhereClause::into_well_formed_goal, but for a quantified where clause. For example, forall<T> { Implemented(T: Trait)} would map to forall<T> { WellFormed(T: Trait) }.

pub fn into_from_env_goal(self, interner: I) -> Binders<DomainGoal<I>>

As with WhereClause::into_from_env_goal, but mapped over any binders. For example, forall<T> { Implemented(T: Trait)} would map to forall<T> { FromEnv(T: Trait) }.

pub fn trait_id(&self) -> Option<TraitId<I>>

If the underlying where clause is a TraitRef, returns its trait id.

Trait Implementations

impl<I> CastTo<Binders<WhereClause<I>>> for Binders<WhereClause<I>>

where I: Interner,

fn cast_to( self, _interner: <Binders<WhereClause<I>> as HasInterner>::Interner, ) -> Binders<WhereClause<I>>

Cast a value to type T.

impl<I, T> CastTo<Goal<I>> for Binders<T>

where I: Interner, T: HasInterner<Interner = I> + CastTo<Goal<I>>,

fn cast_to(self, interner: I) -> Goal<I>

Cast a value to type T.

impl<I, T> CastTo<ProgramClause<I>> for Binders<T>

where I: Interner, T: HasInterner<Interner = I> + CastTo<DomainGoal<I>>,

fn cast_to(self, interner: I) -> ProgramClause<I>

Cast a value to type T.

impl<T> Clone for Binders<T>

where T: Clone + HasInterner, <T as HasInterner>::Interner: Clone,

fn clone(&self) -> Binders<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T> Debug for Binders<T>

where T: HasInterner + Debug,

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

Formats the value using the given formatter.

impl<T> HasInterner for Binders<T>

where T: HasInterner,

type Interner = <T as HasInterner>::Interner

The interner associated with the type.

impl<T> Hash for Binders<T>

where T: Hash + HasInterner, <T as HasInterner>::Interner: Hash,

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

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<V, U> IntoIterator for Binders<V>

where V: HasInterner + IntoIterator<Item = U>, U: HasInterner<Interner = <V as HasInterner>::Interner>,

Allows iterating over a Binders<Vec>, for instance. Each element will include the same set of parameter bounds.

type Item = Binders<U>

The type of the elements being iterated over.

type IntoIter = BindersIntoIterator<V>

Which kind of iterator are we turning this into?

fn into_iter(self) -> <Binders<V> as IntoIterator>::IntoIter

Creates an iterator from a value.

impl<I> IntoWhereClauses<I> for Binders<InlineBound<I>>

where I: Interner,

type Output = Binders<WhereClause<I>>

fn into_where_clauses( &self, interner: I, self_ty: Ty<I>, ) -> Vec<Binders<WhereClause<I>>>

impl<T> PartialEq for Binders<T>

where T: PartialEq + HasInterner, <T as HasInterner>::Interner: PartialEq,

fn eq(&self, other: &Binders<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, I> TypeFoldable<I> for Binders<T>

where I: Interner, T: HasInterner<Interner = I> + TypeFoldable<I>,

fn try_fold_with<E>( self, folder: &mut dyn FallibleTypeFolder<I, Error = E>, outer_binder: DebruijnIndex, ) -> Result<Binders<T>, E>

Apply the given folder folder to self; binders is the number of binders that are in scope when beginning the folder. Typically binders starts as 0, but is adjusted when we encounter Binders<T> in the IR or other similar constructs.

fn fold_with( self, folder: &mut dyn TypeFolder<I, Error = Infallible>, outer_binder: DebruijnIndex, ) -> Self

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.

impl<T, I> TypeVisitable<I> for Binders<T>

where I: Interner, T: HasInterner + TypeVisitable<I>,

fn visit_with<B>( &self, visitor: &mut dyn TypeVisitor<I, BreakTy = B>, outer_binder: DebruijnIndex, ) -> ControlFlow<B>

Apply the given visitor visitor to self; binders is the number of binders that are in scope when beginning the visitor. Typically binders starts as 0, but is adjusted when we encounter Binders<T> in the IR or other similar constructs.

impl<I, T> Zip<I> for Binders<T>

where I: Interner, T: Clone + HasInterner<Interner = I> + Zip<I> + TypeFoldable<I>,

fn zip_with<Z>( zipper: &mut Z, variance: Variance, a: &Binders<T>, b: &Binders<T>, ) -> Result<(), NoSolution>

where Z: Zipper<I>,

Uses the zipper to walk through two values, ensuring that they match.

impl<T> Copy for Binders<T>

where T: HasInterner + Copy, <<T as HasInterner>::Interner as Interner>::InternedVariableKinds: Copy,

impl<T> Eq for Binders<T>

where T: Eq + HasInterner, <T as HasInterner>::Interner: Eq,

impl<T> StructuralPartialEq for Binders<T>

where T: HasInterner,