I came across the following conversation:
A: I'll let you know where I am planning to go on vacation.
B: It wouldn't be vacation if you did.
I am a little confused about the use of did here. Shouldn't it be do instead?
I would see him if I went.
It would be a vacation if you went.
In this type of conditional sentence, the main clause is would + the verb, and the IF clause is in the simple past. Should is also often used here.
It wouldn't be vacation if you did.
Did here here is a substitute for not repeating a verb that was mentioned earlier in a conversation.
For example: John: "I want to work during my vacation".
Mary: It wouldn't be a vacation if you did. [did substitutes for worked]. It wouldn't be a vacation if you worked.
In English, we often use an auxilary to avoid repeating the main verb again.
John: They see the car in the street every night. Mary: If they do [see the car], they should call the cops.
[Please note, I am only giving simple examples here to make my point.]
It s a question of tense agreement:
It is not a vacation if you do
It wouldn't be a vacation if you did