[Bug c++/71882] elaborated-type-specifier friend not looked up in unnamed namespace

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71882

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
IMHO that's a reasonable interpretation, but so is GCC's :-)

Transforming the program as per 10.3.1.1 [namespace.unnamed] we get:

namespace N { }
using namespace N;
namespace N { struct S; }
  class C {
    friend struct S;
    static void f();
  };
namespace N { struct S { void f() { C::f(); } }; }


GCC and EDG still reject this, and Clang still accepts it.

This seems related to https://wg21.link/cwg138