Enum chalk_solve::solve::Guidance

pub enum Guidance<I: Interner> {
    Definite(Canonical<Substitution<I>>),
    Suggested(Canonical<Substitution<I>>),
    Unknown,
}

When a goal holds ambiguously (e.g., because there are multiple possible solutions), we issue a set of guidance back to type inference.

Variants

Definite(Canonical<Substitution<I>>)

The existential variables must have the given values if the goal is ever to hold, but that alone isn’t enough to guarantee the goal will actually hold.

Suggested(Canonical<Substitution<I>>)

There are multiple plausible values for the existentials, but the ones here are suggested as the preferred choice heuristically. These should be used for inference fallback only.

Unknown

There’s no useful information to feed back to type inference

Trait Implementations

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

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<I: Debug + Interner> Debug for Guidance<I>

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

Formats the value using the given formatter.

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

fn eq(&self, other: &Guidance<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: Eq + Interner> Eq for Guidance<I>

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

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