How do I declare a custom struct as metatype that is inside an struct?

[HaoTian]

Here is the code should be like:

Struct BaseStruct
{
        Struct Para1
        {
                int a;
        };
};

Q_DECLARE_METATYPE(Para1) //this is not work.
Q_DECLARE_METATYPE(BaseStruct::Para1) //this is not work either.