public StoreResult(
IEnumerator <object> task, Expression <Func <T> > target,
TaskExecutionPolicy executionPolicy = TaskExecutionPolicy.RunWhileFutureLives
)
{
_Task = task;
_Thunk = new SchedulableGeneratorThunk(_Task);
_ExecutionPolicy = executionPolicy;
_Future = Future.New <T>();
_Future.Bind(target);
_Future.RegisterOnComplete(Completed);
}