build过去将来时表示什么

不能说将来过去时，应该是过去将来时，其结构是 “would + 动词原形”，指的是发生在过去某个时候以后的行为。

例如:

He said to me that his mother would come and see him soon. 过去将来时would come and see 发生在said 以后。

If I were you， I would not make friends with him. 要是我是你，我就不会和去他交朋友。虚拟语气的过去将来时would not make在虚拟动词 were 以后。