Enum chalk_ir::DomainGoal

pub enum DomainGoal<I: Interner> {
    Holds(WhereClause<I>),
    WellFormed(WellFormed<I>),
    FromEnv(FromEnv<I>),
    Normalize(Normalize<I>),
    IsLocal(Ty<I>),
    IsUpstream(Ty<I>),
    IsFullyVisible(Ty<I>),
    LocalImplAllowed(TraitRef<I>),
    Compatible,
    DownstreamType(Ty<I>),
    Reveal,
    ObjectSafe(TraitId<I>),
}

A “domain goal” is a goal that is directly about Rust, rather than a pure logical statement. As much as possible, the Chalk solver should avoid decomposing this enum, and instead treat its values opaquely.

Variants

Holds(WhereClause<I>)

Simple goal that is true if the where clause is true.

WellFormed(WellFormed<I>)

True if the type or trait ref is well-formed.

FromEnv(FromEnv<I>)

True if the trait ref can be derived from in-scope where clauses.

Normalize(Normalize<I>)

True if the alias type can be normalized to some other type

IsLocal(Ty<I>)

True if a type is considered to have been “defined” by the current crate. This is true for a struct Foo { } but false for a #[upstream] struct Foo { }. However, for fundamental types like Box<T>, it is true if T is local.

IsUpstream(Ty<I>)

True if a type is not considered to have been “defined” by the current crate. This is false for a struct Foo { } but true for a #[upstream] struct Foo { }. However, for fundamental types like Box<T>, it is true if T is upstream.

IsFullyVisible(Ty<I>)

True if a type and its input types are fully visible, known types. That is, there are no unknown type parameters anywhere in this type.

More formally, for each struct S<P0..Pn>: forall<P0..Pn> { IsFullyVisible(S<P0…Pn>) :- IsFullyVisible(P0), … IsFullyVisible(Pn) }

Note that any of these types can have lifetimes in their parameters too, but we only consider type parameters.

LocalImplAllowed(TraitRef<I>)

Used to dictate when trait impls are allowed in the current (local) crate based on the orphan rules.

LocalImplAllowed(T: Trait) is true if the type T is allowed to impl trait Trait in the current crate. Under the current rules, this is unconditionally true for all types if the Trait is considered to be “defined” in the current crate. If that is not the case, then LocalImplAllowed(T: Trait) can still be true if IsLocal(T) is true.

Compatible

Used to activate the “compatible modality” rules. Rules that introduce predicates that have to do with “all compatible universes” should depend on this clause so that they only apply if this is present.

DownstreamType(Ty<I>)

Used to indicate that a given type is in a downstream crate. Downstream crates contain the current crate at some level of their dependencies.

Since chalk does not actually see downstream types, this is usually introduced with implication on a fresh, universally quantified type.

forall { if (DownstreamType(T)) { /* … */ } }

This makes a new type T available and makes DownstreamType(T) provable for that type.

Reveal

Used to activate the “reveal mode”, in which opaque (impl Trait) types can be equated to their actual type.

ObjectSafe(TraitId<I>)

Used to indicate that a trait is object safe.

Implementations

impl<I: Interner> DomainGoal<I>

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

Convert Implemented(...) into FromEnv(...), but leave other goals unchanged.

pub fn inputs(&self, interner: I) -> Vec<GenericArg<I>>

Lists generic arguments that are inputs to this domain goal.

Trait Implementations

impl<I: Interner> CastTo<DomainGoal<I>> for DomainGoal<I>

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

Cast a value to type T.

impl<I: Interner> CastTo<DomainGoal<I>> for FromEnv<I>

fn cast_to(self, _interner: I) -> DomainGoal<I>

Cast a value to type T.

impl<I: Interner> CastTo<DomainGoal<I>> for Normalize<I>

fn cast_to(self, _interner: I) -> DomainGoal<I>

Cast a value to type T.

impl<I: Interner> CastTo<DomainGoal<I>> for WellFormed<I>

fn cast_to(self, _interner: I) -> DomainGoal<I>

Cast a value to type T.

impl<I: Clone + Interner> Clone for DomainGoal<I>

fn clone(&self) -> DomainGoal<I>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<I: Interner> CouldMatch<DomainGoal<I>> for ProgramClause<I>

fn could_match(
    &self,
    interner: I,
    db: &dyn UnificationDatabase<I>,
    other: &DomainGoal<I>
) -> bool

Checks whether self and other could possibly match.

impl<I: Interner> CouldMatch<DomainGoal<I>> for ProgramClauseData<I>

fn could_match(
    &self,
    interner: I,
    db: &dyn UnificationDatabase<I>,
    other: &DomainGoal<I>
) -> bool

Checks whether self and other could possibly match.

impl<I: Interner> Debug for DomainGoal<I>

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

Formats the value using the given formatter.

impl<I: Interner> HasInterner for DomainGoal<I>

type Interner = I

The interner associated with the type.

impl<I: Hash + Interner> Hash for DomainGoal<I>

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<I: PartialEq + Interner> PartialEq<DomainGoal<I>> for DomainGoal<I>

fn eq(&self, other: &DomainGoal<I>) -> bool

This method tests for self and other values to be equal, and is used by ==.

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

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

impl<I: Interner> TypeFoldable<I> for DomainGoal<I>

fn try_fold_with<E>(
    self,
    folder: &mut dyn FallibleTypeFolder<I, Error = E>,
    outer_binder: DebruijnIndex
) -> Result<Self, 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>,
    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<I: Interner> TypeSuperVisitable<I> for DomainGoal<I>

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

Recursively visits the type contents.

impl<I: Interner> TypeVisitable<I> for DomainGoal<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: Interner> Zip<I> for DomainGoal<I>

fn zip_with<Z: Zipper<I>>(
    zipper: &mut Z,
    variance: Variance,
    a: &Self,
    b: &Self
) -> Fallible<()>

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

impl<I: Interner> Copy for DomainGoal<I>where
    I::InternedSubstitution: Copy,
    I::InternedLifetime: Copy,
    I::InternedType: Copy,

impl<I: Eq + Interner> Eq for DomainGoal<I>

impl<I: Interner> StructuralEq for DomainGoal<I>

impl<I: Interner> StructuralPartialEq for DomainGoal<I>