Overload Resolution: How is this not ambiguous?

Question

Suppose we have this code, copied from a separate question:

namespace x 
{
    void f()
    {
    }

    class C 
    {
        void f() 
        {
            using x::f;
            f();         // <==
        }
    };
}

The name f on the indicated line unambiguously refers to x::f (at least according to both gcc and clang). Why is x::f preferred over x::C::f in this case? Shouldn't it be ambiguous as both names are visible?

Answer 1

Because the using declaration brings x::f into the scope of f, which is narrower than that of C. Unqualified lookup considers the local block scope, finds a match, and stops before considering the wider class scope. There is no argument-dependent lookup since there are no function arguments, so no further scopes are considered.