needn't have done sth. 本不必做某事(你在过去做的那件事现在看来是没有必要的)。
needn't do sth. 不必做某事。(现在没有必要做某事,自然那件事还没有做)。
didn't need to do sth. 过去不必做某事 (后来是否做了不得而知,也不关心)。
need not have done something 意思是某人做了某事,但那么做是不必要的,是浪费时间。
You needn't have woken me up. I don't have to go to work today.
你本来用不着叫醒我。今天我不必上班。
I needn't have cooked so much food. Nobody was hungry.
我不该做这么多吃的,大家都不饿。
而 did not need to do something 则仅仅表示不必做某事(不管是否已经做了)。试比较:
I needn't have watered the flowers. Just after I finished it started raining.
我其实不必给花浇水的。刚浇完就下雨了。
It started raining, so I didn't need to water the flowers.
下起雨来了,这样我就不用给花浇水了。
need never have ... 是 need not have ... 的强调形式。
I need never have packed all that suncream - it rained every day.
我其实根本不需要带上那些防晒霜的 —— 天天都下雨。
need not 或 do not need to 表示不必做某事。
You needn't tell Jennifer - she already knows.
你不用告诉珍妮弗了 —— 她已经知道了。
need not 有时也表示某事不一定真实。
“She looks quite ill. I'm sure it's flu.”“It needn't be - maybe she's just over-
tired.”
“她看上去病得很重,肯定是得了流感。”“那也不一定 — 也许只是劳累过度了。”
(以上摘自《牛津英语用法指南》第四版 532.6;532.7)
【归纳】
needn't have done sth. 本来不必做某事(但是实际上已经做了某事)。
needn't do sth. 不必做某事。( 实际上还没有做)。
didn't need to do sth. (过去)不必做某事
不能说:did not need to have done