The example in 6.5.3 [basic.lookup.unqual] paragraph 3 is incorrect:
typedef int f;
struct A {
friend void f(A &);
operator int();
void g(A a) {
f(a);
}
};
Regardless of the resolution of other issues concerning the lookup
of names in friend declarations, this example is ill-formed
(the function and the typedef cannot exist in the same scope).
One possible repair of the example would be to make f a class with a constructor taking either A or int as its parameter.