This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 118c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-10-11

1945. Friend declarations naming members of class templates in non-templates

During the discussion of issue 1918, it was decided that the last part of the issue should be split off into a separate issue. According to 13.7.5 [temp.friend] paragraph 5,

A member of a class template may be declared to be a friend of a non-template class.

Does this make the example from issue 1918,

  template<typename T> struct A {
    class B {
      class C {};
    };
  };
  class X {
    static int x;
    template <typename T> friend class A<T>::B::C;
  };
  template<> struct A<int> {
    typedef struct Q B;
  };
  struct Q {
    class C {
      int f() { return X::x; }
    };
  };

ill-formed because the friend declaration does not refer to a member of a class template? This does not appear to be the interpretation chosen by most implementations.

Additional note (January, 2024)

The example is ill-formed per the resolution of issue 1862 (adopted in November, 2017).