[clang] Clarify use of contractions in diagnostic messages (PR #116803)

[via cfe-commits]

Sirraide wrote:

> I don't think contractions are the confusing part of diagnostics, but I do think we want consistency between our diagnostics as much as possible and we use a mixture of both contractions and no contractions inconsistently (though that's improving). I fall on the side of avoiding contractions rather than including them.

I guess that makes sense yeah (I personally don’t care *that* much about consistency wrt diagnostic wording, but I can also see why that’s something we’d want).

> Do you have strong opinions on using contractions? Would you recommend we go the other direction and switch to consistently using contractions?

I don’t have *strong* opinions about this, no; *linguistically*, imo either way is fine (I’d just be a bad linguist if I didn’t argue against prescriptivism whenever it comes up ;Þ), but I don’t have a problem w/ picking one over the other for non-linguistic reasons. I mean, I would probably prefer it if we could write diagnostic messages w/o having to think too hard as to what the correct style is wrt things like these (because it’s what I think people will just naturally do), but if it’s just a matter of ‘we want to be consistent, so let’s always do X, even though that choice is more or less arbitrary’, then that’s equally valid.

So in sum, enforcing one over the other is not what I’d want to do (and I just don’t think it’s all that necessary), but if we decide to go that route, then I’m fine w/ that too ;Þ

https://github.com/llvm/llvm-project/pull/116803