below is an example in standard N2960. 

struct A { A(); };
struct B : public A { B(); };
A::A() { }
B::B() { }
A::A a;
int main()
{
	return 0;
}

According to the standard [class.qual]/2, 'A::A a;' is error because A::A is not a type name. But g++ can compile it without error or warning.