public com.sun.javadoc.Type superclassType() {
        if (isInterface() || isAnnotationType() ||
                (tsym == env.syms.objectType.tsym))
            return null;
        Type sup = env.types.supertype(type);
        return TypeMaker.getType(env,
                                 (sup != type) ? sup : env.syms.objectType);
    }