[n4134] - Resumable Functions rev2 was implemented in VS2015 Update 2 [1]
It appears that Visual Studio 2015 Update 3 actually implements http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/p0057r0.pdf
an awaitable type needs to define 3 member functions.
bool await_ready() const;
void await_suspend(std::coroutine_handle<>);
T await_resume();await_ready() is called when co_await is used on an awaitable. It returns false to suspend, otherwise it needs to have a value ready.
await_suspend() is called when await_ready() returns false, right before the function is suspended.
await_resume() is called right before this function is resumed.
The coroutine promise is looked up under the resumable function type R::promise_type A resumable function must specify coroutine promise, which has:
get_return_object()
initial_suspend()
final_suspend()Coroutines must be of type resumable function:
struct promise_type;
constructor(coroutine_handle<promise_type> c);
destructor(); // call c.destroy()| [n4134] | http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4134.pdf |
| [1] | https://github.com/kirkshoop/await |