class A<T>
{
    public class B { }
}

class Stuff<T>
{
    public static void Foo(A<T>.B x) { }
    public static void Foo(A<int>.B x) { }
}

class Program
{ 
    static void Main()
    {
        Stuff<int>.Foo(new A<int>.B()); // here
    }
}