Clarify whether get_return_object() result is stored with 'auto' or 'decltype(auto)' semantics

[lewissbaker]

The current specification (N4680) wording for get_return_object() in 8.4.4(5) simply just says that:

... the return value is produced by a call to p.get_return_object()

This return-value can potentially be of a different type to the return-type of the coroutine function and so the return-value needs to be stored somewhere while the coroutine is started.

I'm assuming that the coroutine is translated to something (very roughly) like this:

R foo(ARGS... args)
{
  coro_frame* f = new coro_frame(std::forward<ARGS>(args)...);
  auto returnObject = f->promise.get_return_object();
  std::experimental::coroutine_handle<decltype(f->promise)>::from_promise(f->promise).resume();
  return returnObject; // possible implicit conversion to R here
}

However, I'm wondering what the semantics are when get_return_object() returns a reference. Is the referenced copied/moved into a new variable (auto semantics) or is the reference itself stored as the returnObject (decltype(auto) semantics)?

Can the wording of 8.4.4(5) be amended to clarify this?