[Bug c++/64063] [DR 1665] Incorrect "ambiguous template specialization" error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64063

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The current handling of the following is still wrong (rejects-valid)
independent of DR 1665. It should compile because it can only refer to the
template:

template<typename T>
struct S
{
  void foo(int);
  template<typename U> void foo(U) { }
};

template void S<char>::foo<>(int);