为什么我不能使用模板化类来专门化类模板？

Question

Why is the below partial specialization not allowed? The class is specialized with a templated class:

template <class T>
class ClassT{};

template<class F>
class ClassF{};

//error here
template<>
template <class T>
class ClassF <ClassT<T> >{};

int main(int argc, char* argv[])
{
    ClassF<ClassT<int> > ftx; //no error
}

The error:

tester.cpp(8): error C2910: 'ClassF<ClassT<T>>' : cannot be explicitly specialized

Answer 1

The original problem I was having is that I forgot to include the header of the class I was trying to specialize! Of course that would never work but the error message was not clear enough: I did not get undefined identifier or something similar which would have been more useful. So that's why I was fiddling with syntax, trying template<> trick etc.