如何将结构模板标记为朋友？

I have code like this:

我有这样的代码：

template <typename T, typename U> struct MyStruct {
    T aType;
    U anotherType;
};

class IWantToBeFriendsWithMyStruct
{
    friend struct MyStruct; //what is the correct syntax here ?
};
template <t