TaskInstances are cancelable, either explicitly
or automatically due to the host object being destroyed, or
because concurrency policy enforced by a
Task Modifier canceled the task instance.
If this TaskInstance is canceled or throws an error (or yields a promise that rejects), this property will be set with that error. Otherwise, it is null.
True if the task instance has started, else false.
True if the task instance is canceled
True if the task instance resolves to a rejection.
True if the task has run to completion.
True if the task instance is fulfilled.
If this TaskInstance runs to completion by returning a property other than a rejecting promise, this property will be set with that value.