How to test call member?, C++ (clang)

How to test call member?

//clang 3.7.0

#include <iostream>
#include <type_traits>

class SCallFailure{};

template<typename T>
struct Has_Call
{
    static SCallFailure test(...);
    
    template<typename... Args>
    static auto test(Args... args ) -> decltype( std::declval<T>().call(args...) );
    
};

template<typename T>
struct HasCallS : std::true_type
{};

template<>
struct HasCallS<SCallFailure> : public std::false_type
{};

template<typename T, typename... Args>
constexpr bool hasCall(Args... args)
{
    typedef decltype(Has_Call<T>::test(args...)) R;
    
    return HasCallS<R>::value;
}

class A
{
public:
    int call(int,int){ return 0; }
};

class B
{
public:
    int call(){ return 0; }
};

class C
{};

int main()
{

std::cout << "A " <<  (hasCall<A>(0,0) ? "has " : "not have ") << " int call(int,int) member function" << std::endl; 
    std::cout << "B " <<  (hasCall<B>() ? "has " : "not have ") << " int call() member function" << std::endl; 
    //std::cout << "C " <<  (hasCall<C>() ? "has " : "not have ") << " int call() member function" << std::endl; 
    return 0;
}


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