detect if a class has specific static field of specific type in C++

main.cpp

#include <iostream>
#include "type_checker.h"

typedef struct payload {} payload;

typedef struct payload2 {
    static std::string id;
} payload2;
std::string payload2::id;

int main() {
    std::cout << has_static_id<payload>::value << std::endl; // 0
    std::cout << has_static_id<payload2>::value << std::endl; // 1
    return 0;
}

type_checker.h

#include <type_traits>

// reference https://stackoverflow.com/a/16000226

template<typename T, typename = void>
struct has_static_id : std::false_type {
};

template<typename T>
struct has_static_id<T, typename std::enable_if<std::is_same<std::string, std::decay_t<decltype(T::id)>>::value, void>::type> : std::true_type  {
};