[Bug c++/86883] Unexpected error: expansion pattern '' contains no argument packs

[ppalka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86883

--- Comment #7 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Another testcase (based off of the PR118454 testcase):

template<class T> using identity = T;

template<class T> struct A;

template<class... Ts>
struct B {
  template<class U, Ts...> struct dual;

  template<class T, int... Vs>
  using ty1 = dual<identity<T>, Vs...>;

  template<class T, int... Vs>
  using ty2 = dual<T, Vs...>;
};