#include <iostream>
#include <typeinfo>

// Defined in C++17. Needed by all checks
template <class... Ts>
using void_t = void;

// For each different member you want to check for, you need something like this
template <class T, class=void>
struct has_foo_member : std::false_type{};

template <class T>
struct has_foo_member<T, void_t<decltype(T::foo)>> : std::true_type{};

// Where you can use the aforementioned checks with enable_if
template <class T, std::enable_if_t<has_foo_member<T>::value>* = nullptr>
void print_has_foo_member() {
  std::cout << "Class " << typeid(T).name() << ": has a foo member" << std::endl;
}

template <class T, std::enable_if_t<!has_foo_member<T>::value>* = nullptr>
void print_has_foo_member() {
  std::cout << "Class " << typeid(T).name() << ": does not have a foo member" << std::endl;
}

// Here are some example classes we will check
struct Empty {
};

struct HasStaticFoo {
    static int foo;
};

struct HasNonstaticFoo {
    double foo;
};

struct HasFooMethod {
    double foo(){ return 1; };
};
int main()
{
    print_has_foo_member<Empty>();
    print_has_foo_member<HasStaticFoo>();
    print_has_foo_member<HasNonstaticFoo>();
    print_has_foo_member<HasFooMethod>();
}