Problem with functions accepting inner classes of template classes

Question

I have a problem with inner classes in class templates. I have a template class (say: Matrix), and a subclass (say: Matrix::Row).

Answer 1

How should the compiler be able to deduce this? Imagine the following setup:

struct A { typedef int T; };
struct B { typedef int T; };

template  void foo(typename S::T);

Now when you say int x; foo(x);, there's no way to match this unambiguously.

The point is that you are not deducing a template parameter from a given class template, but rather just an arbitrary, free-standing type. The fact that that type was defined inside another class is not relevant for that.