#include <iostream>
#include <sstream>
#include <type_traits>
 
template<typename S, typename T>
class is_streamable
{
    template<typename SS, typename TT>
    static auto test(SS&& s, TT&& t)
    -> decltype(std::forward<SS>(s) << std::forward<TT>(t));
 
    struct dummy_t {};
    static dummy_t test(...);
 
    using return_type = decltype(test(std::declval<S>(), std::declval<T>()));
 
public:
    static const bool value = !std::is_same<return_type, dummy_t>::value;
};
 
class C {};
 
int main() {
	std::cout <<is_streamable<std::stringstream, C>::value << std::endl;
	return 0;
}

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