Subject: 27.1; "Old-style backquotes detected!" when there are no backquotes.

From: Bruce Mardle <[email-masked]>
Date: Fri, 8 Apr 2022 17:43:21 +0000 (UTC)

Short version:
Try to evaluate
'(, foo)
and you'll get (error "Old-style backquotes detected!"), which is
confusing considering that the expression doesn't contain a backquote!

Long version:
My code was evaluating happily yesterday (on what much have been an old
version of Emacs) but came up with that error on 27.1 today.  It turned
out I had "(, " in a few places. They should have been "(* ", (OCR
failure) so I suppose I should thank the error message for helping me find
those... but it's a confusing message when source doesn't contain any
backquotes!
(I spent a while Googling to find out what was happening but only found
cases of people getting the error message whose code *did* contain a
backquote.)

In GNU Emacs 27.1 (build 1, x86_64-pc-cygwin)
 of 2020-10-29 built on moufang2
Repository revision: 14432a33511ec750815c6f3b188f2c0d21b4cb22
Repository branch: master
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elisp--preceding-sexp: Old-style backquotes detected!
Making completion list...
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