People are often confused about how to discuss something that didn’t happen in the past. It’s standard usage to say “If I had remembered where I parked the car, I would have gotten home sooner.” Notice that in the part of the sentence containing “if” the helping verb is “had” but in the other part of the sentence, which depends logically on the first, the verb “gotten” is preceded by “would have.”
The same pattern applies when the “if” is in a later part of the sentence: “I would have gotten home sooner if I had remembered where I parked the car.” Plain old “had” stays with the “if” clause (the second one) and “would have” goes in the other clause (the first one).
The problem is that people used to thinking of “would have” as marking non-events in the past often replace a correct “had” with an incorrect “would have”: “If I would have remembered where I parked the car. . . .” This is nonstandard.
Even worse, the same mistake is made in sentences where no “if” is involved: “The robber wished he would have given the bank clerk a fake ID when she asked for one.” This should be “The robber wished he had given.”
One reminder of the correct pattern is that “had” all by itself can replace “if . . had”: “Had I remembered where I parked the car. . . . “Would have” clearly can’t be used in this way, so you need to stick with plain old “had.”
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