throwIfFinished method
Throws StateError if the job has finished: a context that outlived its job neither writes nor starts anything.
Also throws while the core unwinds the cleanup stack — see throwIfDisposing.
Implementation
@protected
void throwIfFinished(String action) {
if (_owner.isFinished) {
throw StateError('$_owner has already finished, cannot $action');
}
throwIfDisposing(action);
}