Trait PredicateProxy 

pub trait PredicateProxy<I: Interner>:
    TypeSuperFoldable<I>
    + TypeSuperVisitable<I>
    + Flags
    + Copy {
    // Required methods
    fn allow_normalization(&self) -> bool;
    fn clause_kind_unchecked(&self) -> Option<Binder<I, ClauseKind<I>>>;
    fn map_projection(
        self,
        cx: I,
        f: impl FnOnce(Binder<I, ProjectionClause<I>>) -> Binder<I, ProjectionClause<I>>,
    ) -> Option<Self>;
}

Fold predicate deliberately doesn’t get access to an actual predicate. This way, we can compress lists of predicates, and hide this detail to folders. Instead, some type implementing this trait, PredicateProxy is passed, with its limited API.

Most TypeFolders only use fold_predicate to inspect type flags.

Required Methods

fn allow_normalization(&self) -> bool

fn clause_kind_unchecked(&self) -> Option<Binder<I, ClauseKind<I>>>

Gets the underlying clause kind (if this predicate is a clause, otherwise None). The fact that it’s unchecked, is because no attempt is made to hide implementation details. For example, in the future we may compress clauses together. Code calling clause_kind_unchecked will have to correctly deal with these implementation details, and have code handling any edgecase arising as a result.

fn map_projection( self, cx: I, f: impl FnOnce(Binder<I, ProjectionClause<I>>) -> Binder<I, ProjectionClause<I>>, ) -> Option<Self>

If self is a projection clause, call f with it. The result will be rebound and returned as Some. Otherwise, when self is not a projection clause, None is returned.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors