过去将来完成时
过去将来完成时
should / would have done sth.
用法
1、 过去将来完成时表示在过去某一时间对将来某一时刻以前所会发生的动作。 构造：should / would have done sth.
I thought you'd have left by this time.我想这会儿你已经走了。
He told them he would have finished it by 8 o'clock.他告诉他们他会在8点以前干完。
I guessed that Helen wuold have told her something.我猜海伦会告诉她一些情况的。
2、 过去将来完成时还常用在虚拟语气中，表示与过去的事实相反。
[注]在当代英语中，大家都用 would (缩略式为 'd)