std::promise where T must be default constructible in Visual Studio 2017?

Question

I am trying to compile the following code in Visual Studio 2017:

#include 

int main()
{
    std::promise&         


        

Answer 1

I suppose you do not need std::reference_wrapper<int>. There is the suitable overloaded template for std::promise available:

template<class R> class promise<R&>;

Therefore you can fix your code in Visual Studio 2017:

#include <future>

int main()
{
    std::promise<int&> promise;
    (void)promise;
}

Answer 2

Looks like it is a known issue in MSVC's standard library implementation. A simpler reproduction scenario:

#include <future>
struct NoDefaultCtor
{
    NoDefaultCtor() = delete;
};
int main() {
    std::promise<NoDefaultCtor> p;
    return 0;
}