Function rustc_trait_selection::traits::project::project_and_unify_type

fn project_and_unify_type<'cx, 'tcx>(
    selcx: &mut SelectionContext<'cx, 'tcx>, 
    obligation: &Obligation<'tcx, ProjectionPredicate<'tcx>>
) -> Result<Result<Option<Vec<PredicateObligation<'tcx>>>, InProgress>, MismatchedProjectionTypes<'tcx>>

Evaluates constraints of the form:

<T as Trait>::U == V

If successful, this may result in additional obligations.

See poly_project_and_unify_type for an explanation of the return value.