A friend declaration is a member-declaration, but it is not clear how far the granting of friendship goes in a friend declaration. For example:

  class c {
    class n {};
    friend struct s;
  };

  struct s {
    friend class c::n;          // #1
    friend c::n g();            // #2
    friend void f() { c::n(); } // #3
  };

In particular, if a friend function is defined inside the class definition, as in #3, does its definition have access to the private and protected members of the befriending class? Implementations vary on this point.

See CWG1699 for the full discussion.