cio.cpp

#include <type_traits>
#include <iostream>

template <class A, class = void>
struct has_member : std::false_type {};

template <class A>
struct has_member<A, decltype(A::member, void())> : std::true_type {};

struct AA { static constexpr bool member = true; };
struct BB {};

int main() {
    std::cout << has_member<AA>::value << std::endl;
    std::cout << has_member<BB>::value << std::endl;
    return 0;
}