1*67e74705SXin Li template<typename, typename = int> struct A; 2*67e74705SXin Li template<typename T> struct B; 3*67e74705SXin Li 4*67e74705SXin Li template<typename, typename> struct A {}; 5*67e74705SXin Li template<typename T> struct B : A<T> {}; 6