[Bug c++/86171] [6/7/8/9 Regression] g++ ICE on valid code: tree check: expected var_decl or function_decl, have type_decl in duplicate_decls, at cp/decl.c:2291

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86171

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
A well-formed variant:

template <class> struct A;
template <class T> using B = typename A<T>::X;
template <class T> struct A {
  typedef int X;
  typedef B<T> U;
};
B<short> b;