* substituted by the wildcard
     */
    private WildcardType makeSuperWildcard(Type bound, TypeVar formal) {
        if (bound.tag == BOT) {
            return new WildcardType(syms.objectType,
                                    BoundKind.UNBOUND,
                                    syms.boundClass,
                                    formal);
        } else {
            return new WildcardType(bound,
                                    BoundKind.SUPER,
                                    syms.boundClass,
                                    formal);
        }
    }