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>),
}
Expand description

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

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

Lists generic arguments that are inputs to this domain goal.

Trait Implementations

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Checks whether self and other could possibly match.

Checks whether self and other could possibly match.

Formats the value using the given formatter. Read more

The interner associated with the type.

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

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

This method tests for !=.

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. Read more

Recursively visits the type contents.

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. Read more

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

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Cast a value to type U using CastTo.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Cast a value to type T.

Checks whether self and other could possibly match.

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Shifts this term in one level of binders.

Shifts a term valid at outer_binder so that it is valid at the innermost binder. See DebruijnIndex::shifted_in_from for a detailed explanation. Read more

Shifts a term valid at the innermost binder so that it is valid at outer_binder. See DebruijnIndex::shifted_out_to for a detailed explanation. Read more

Shifts this term out one level of binders.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

Check whether there are free (non-bound) variables.