Subject: Re: bug#61281: “`(a \, b)” equals to “`(a . ,b)”

From: Michael Heerdegen <[email-masked]>
Date: Thu, 09 Feb 2023 03:15:51 +0100

Drew Adams <[email-masked]> writes:

> Maybe we mean different things by the bugged behavior?  Do you see
> lots of places where the Emacs sources use "\,"?

Yes, there are indeed some.  A common one is (eq \, (car-safe EXPR)) to
test whether some expression is an "unquote expression".  Used in
code-walker like things - byte compiler, stuff to save expressions in
files, pcase, such things.

Any package can make use of the reader constructs in non-trivial ways (I
mean, uses unrelated to backquote).  And the only way to treat such
expressions is to test for the expansion.

> > > Assuming the bug isn't going to be fixed, I'd propose we just describe
> > > the problem in a comment.
> >
> > Where should this comment be located?
>
> As part of the comment you pointed to, which tries
> to describe how the code works/behaves?

See my other comment then.

Michael.