VS2015 Variadic模板错误？

Question

template<typename T0, typename T1, typename ...ArgN>
bool is_any_test(T0 arg0, T1 arg1, ArgN... argn...)
    {
    return arg0 == arg1 || is_any_test<T0, ArgN...>(arg0, argn...);
    };

template<typename T0, typename T1>
bool is_any_test(T0 arg0, T1 arg1)
    {
    return arg0 == arg1;
    };

int wmain(int /*argc*/, const wchar_t* /*argv[]*/)
    {
    is_any_test(3,4);
    return 0;
    };

(can run it right here http://webcompiler.cloudapp.net/ )

On VS2015 this results in

C2668 ambiguous call to overloaded function

On VS2013 this worked fine. Is this a bug or am I missing something? Is there any workaroung? (changing all the occurancies to plain ifs - is not an option)

Answer 1

I've modified your code to working example (not tested 100%..)

template <class T>
bool is_any_test_impl(T t) {
    return false;
}

template<class T1,class T2,class... Args>
bool is_any_test_impl(T1 t1, T2 t2, Args&&... args) {
    return t1 == t2 || is_any_test_impl(std::forward<T1>(t1),std::forward<Args>(args)...);
}

template<class... Args>
bool is_any_test(Args&&... args)
{
    return is_any_test_impl(std::forward<Args>(args)...);
};

/*
    auto b = is_any_test(1, 2, 3, 4, 5); //false
    auto b1 = is_any_test(1, 2, 3, 4, 5, 1); //true
*/

Answer 2

Typo. See comments for more detail...