bug#64128: regexp parser zero-width assertion bugs

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 64128@debbugs.gnu.org
> Date: Sat, 17 Jun 2023 15:18:00 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> 
> > Clearly, but some behaviour needs to be preserved for compatibility.
> > Regexps like "^*" aren't uncommon. Can it be generalised in a useful way?
> > 
> 
> doc/lispref/searching.texi says that "*" is treated as an ordinary 
> character if it is in a context where its special meaning makes no 
> sense, giving "*foo" as an example. If we break with this tradition by 
> making "\b*" an error instead of being equivalent to "\b\*", we should 
> update that part of the manual.
> 
> One possible way forward is to update doc/lispref/searching.texi to 
> specify what we want. Then we can modify the code to match the updated 
> documentation.
> 
> In my experience, modifying the doc is often the hard part, so I took a 
> crack at that in the draft proposed patch, which I have not installed.
> 
> Comments?

My comment is that since this was a documented feature, I'm not
interested in making it an error.