SFINAE with std::is_rvalue_reference for variadic template argument list fails

Question

I try to implement a function taking a variable list of rvalue references. It looks like this:

template <
    typename... Args,
    typename = std::enable_if_t<std::conjunction<
        std::is_rvalue_reference<Args>...>::value>
>
void myfunc(Args&&... args)
{ }

When I try to call it like this:

void doit()
{
    int x;

    myfunc(std::move(x));
}

The compiler tells me that he cannot find the function. If i remove the SFINAE check it works. Do I miss something here, or is the compiler wrong? I'm using Visual Studio with toolsets v140 and v141.

Thanks in advance, Martin

Answer 1

Args is not an rvalue reference, Args&& is.

#include <type_traits>
#include <utility>

template <
    typename... Args,
    typename = std::enable_if_t<std::conjunction<
        std::is_rvalue_reference<Args&&>...>::value>
>
void myfunc(Args&&... args) { }

struct probe {};

int main() {
    probe x;

    // this compiles
    myfunc(std::move(x));

    // this does not
    myfunc(x);

    return 0;
}