I’ve begun to notice the use of “did” in contexts that call for “had.”
In an episode of CSI New York, the Sinese character remarks:
If I didn’t do it, he would have killed me.
He’s referring to something bad he did earlier in the episode. He wasn’t killed, so the act he’s referring to is both contrary to fact and in the past.
The statement is an example of the contrary-to-fact past conditional. Because the “if” clause refers to a contrary-to-fact past event, it requires the past perfect form of the verb.
If I hadn’t done it, he would have killed me.
Here’s another example of using “did” when “had” was called for:
Did you bring any beer? I wish I did.
The speaker has arrived at a gathering of friends. It’s clear from the context that he’s wishing he’d thought to bring some beer.
The main verb in the first sentence is “bring.” The second sentence conveys a regret that the speaker did not carry out an act in the past. Since the bringing of the beer remained undone in the past, the past tense of “bring” is called for in the second sentence:
Did you bring any beer? I wish I had (“brought some” is understood).
What do you think? Do errors like these portend a further erosion of the past perfect?