Question

Does a return type like this represent something meaningful in c++11?

template <typename R>
R&& grabStuff();

T instance = grabStuff<T>();

I would hope that grabStuff should throw a compile-time error if R does not have a move constructor, since this would seem to disallow the return type to use a copy constructor

Answer 1

As always, when returning references you must return a reference to something that’s still alive after the function returns. How you do that is up to you. Example:

T global_thing;

T && get() { return std::move(global_thing); }

struct Foo { Foo(T &&); /* ... */ };

int main()
{
    global_thing.reset();
    Foo a(get());
    global_thing.reset();
    Foo b(get());
}

The more typical example for returning an rvalue reference is std::move itself, though, which returns a reference to the thing you pass into it (and thus it’s the caller’s responsibility to provide a valid input).