Possible to use type_traits / SFINAE to find if a class defines a member TYPE?

Question

I have seen this question which allows one to check for the existence of a member function, but I\'m trying to find out whether a class has a member

Answer 1

I prefer to wrap it in macro.

test.h:

#include 

template
struct void_type
{
     using type = void;
};

template
using void_t = typename void_type::type;

#define HAS_TYPE(NAME) \
template \
struct has_type_##NAME: std::false_type \
{}; \
template \
struct has_type_##NAME>: std::true_type \
{} \

HAS_TYPE(bar);

test.cpp:

#include 

struct foo1;
struct foo2 { typedef int bar; };

int main()
{
    std::cout << has_type_bar::value << std::endl;
    std::cout << has_type_bar::value << std::endl;
    return 0;
}