Function onMainThread

flow/include/flow/ThreadHelper.actor.h:809–819

// TODO: Add SFINAE overloads for functors returning void or a non-Future type.
template <class F>
ThreadFuture<decltype(std::declval<F>()().getValue())> onMainThread(F f) {
	Promise<Void> signal;
	auto returnValue = new ThreadSingleAssignmentVar<decltype(std::declval<F>()().getValue())>();
	returnValue->addref(); // For the ThreadFuture we return
	// TODO: Is this cancellation logic actually needed?
	Future<Void> cancelFuture = internal_thread_helper::doOnMainThread<decltype(std::declval<F>()().getValue()), F>(
	    signal.getFuture(), f, returnValue);
	returnValue->setCancel(std::move(cancelFuture));
	g_network->onMainThread(std::move(signal), TaskPriority::DefaultOnMainThread);
	return ThreadFuture<decltype(std::declval<F>()().getValue())>(returnValue);
}

template <class V>
class ThreadSafeAsyncVar : NonCopyable, public ThreadSafeReferenceCounted<ThreadSafeAsyncVar<V>> {