Rationale:

To make Events more useful (and more akin to regular event programming), they should be able to report the status of the Event they were tracking.

Possible implementation:

• Add a Status field to TaskExecutor::EventState
• Add a TaskExecutor::setEventStatus(const EventHandle& event, Status status) method (that takes the same lock as TaskExecutor::waitForEvent) to set the EventState's status
• Make TaskExecutor::waitForEvent(const EventHandle& event) return the eventState's Status:

void ThreadPoolTaskExecutor::waitForEvent(const EventHandle& event) {
    invariant(event.isValid());
    auto eventState = checked_cast<EventState*>(getEventFromHandle(event));
    stdx::unique_lock<stdx::mutex> lk(_mutex);
    while (!eventState->isSignaledFlag) {
        eventState->isSignaledCondition.wait(lk);
    }
+    return eventState->status
}