Function associated_type_for_impl_trait_in_trait

fn associated_type_for_impl_trait_in_trait(
    tcx: TyCtxt<'_>,
    opaque_ty_def_id: LocalDefId,
) -> LocalDefId

Given an opaque_ty_def_id corresponding to an impl Trait in an associated function from a trait, synthesize an associated type for that impl Trait that inherits properties that we infer from the method and the opaque type.