// TFL Runtime type predicate.
class TFL_RuntimeType<TypeConstraint t> {
  Pred tflRuntimeTypePredicate = t.predicate;
  string tflRuntimeTypeDescription = t.summary;
}

class TFL_AnyTypeOf<list<Type> allowedRuntimeTypes, string description = "",
                    list<Type> allowedOpTypes = [AnyType]> :
  AnyTypeOf<allowedOpTypes, description>,
  TFL_RuntimeType<AnyTypeOf<allowedRuntimeTypes, description>>;