CODE:

#include
#include
#include

template
class has_equal{
	template
	struct null_value{
		static U& value;
	};

	template
	static std::true_type test(U*,decltype(null_value::value==null_value::value)* = 0); //※ここでSFINAEが行われる。
	static std::false_type test(void*);
	
public:
	typedef decltype(test(static_cast(0))) type;
	static const bool value = type::value;
};

struct sample1{
};

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