std::bind and rvalue reference

Question

Let's consider the following piece of code:

class Widget{
};

int main(){
Widget w;
auto lambda = bind([](Widget&& ref){ return; }, std::move(w));

return 0;
}

and it triggers error

no match for call to ‘(std::_Bind<main()::<lambda(Widget&&)>(Widget)>) ()’
     lambda();

And my question is: Why the error has appeared? After all, I do an explicit cast to rvalue reference – I mean std::move(w) and I take argument by rvalue reference – I mean Widget&& ref.

What's up?

Moreover the the below code works, what makes me worried the more:

class Widget{
};

int main(){
Widget w;
auto lambda = bind([](Widget& ref){ return; }, std::move(w));

return 0;
}

Answer 1

To make it work you need to write it like this:

#include <functional>
#include <iostream>

class Widget{};

int main()
{
    Widget a;
    auto lf = [](Widget&& par){ };

    auto f = std::bind
    (
        lf,
        std::bind
        (
            std::move<Widget&>, a
        )
    );
    f();
    return 0;
}

My compiler is gcc version 4.9.2 20141101 (Red Hat 4.9.2-1) (GCC)