While working on P0634 I noticed that the following testcase is accepted while it probably shouldn't be:

template<typename T> struct A {
  template<typename U> struct B;
  template<typename U> using C = U;
};

template<typename T> A<T>::B<T> f1();
template<typename T> A<T>::C<T> f2();

The dependent names "A<T>::B<T>" should be prefixed by the typename keyword, and the template keyword should come after ::.

With P0634 that typename will no longer be required[*] but I think it still requires "::template".

[*] it is a decl-specifier of the decl-specifier-seq of a simple-declaration or a function-definition in namespace scope