Visibility of template specialization of C++ function

Question

Suppose I have fileA.h which declares a class classA with template function SomeFunc(). This function is implemented directly

Answer 1

@[anthony-williams],

are you sure you're not confusing extern template declarations with extern template instantiations? From what I see, extern template may only be used for explicit instantiation, not for specialization (which implies implicit instantiation). [temp.expl.spec] doesn't mention the extern keyword:

explicit-specialization:
    template < > declaration