The to-infintive expresses an unactualized event:
1/ For us to have given up at that stage ... (but we didn't give up)
T/ If we had given up at that stage ... (but we didn't give up.)
Conditional: You could have finished yesterday or by now or even by tomorrow (but you didn't finish yesterday or by now. Maybe you'll finish it by tomorrow.)
2/ Had [it] not been for your laziness, you could have finished the work BY NOW.
3/ I would like you told me... (ungrammatical)
4/ In the sentence "He wouldn't have come unless you had invited him"
(He was there)
5/ If only you had listened to me, you wouldn't be in such a situation
If only you'd listened to me you wouldn't be in such a situation.
6/ If I knew the answer I would tell you. <present>
If I had known the answer I would have told you. <past>
If I had known the answer I would tell you.
7/ I won't tell you UNLESS (that is) you promise to keep it to yourself.
8/ Were it not for the fact that his father is on the board of directors, he wouldn't get this job. ("get" is present, not past; he doesn't have the job yet, but there's some indication that he may just get it.)
- For Teachers