[Bug c++/80830] [8 Regression] ICE in tsubst_copy, at cp/pt.c:14569

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80830

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Reduced test-case:

template <int> class a;
class b
{
  friend int operator>> (int, b);
};
template <int c> int &operator>> (int &, a<c> &);
template <int = 3> class a
{
  friend int &operator>><> (int &, a &);
  a<>
  d ()
  {
  }
};