Re: :alnum: broken?

[Eli Zaretskii]

> From: Paul Eggert <address@hidden>
> Date: Sat, 22 Feb 2020 23:51:11 -0800
> Cc: address@hidden
> 
> On 2/22/20 7:49 PM, Richard Stallman wrote:
> > Can we do something to report such errors?
> 
> Yes, it would be easy to modify the Emacs regular expression parser to signal 
> an 
> error for patterns like [:alnum:]. GNU grep has been reporting these as 
> errors 
> ever since Paolo Bonzini changed it to do so in 2010, and it's been a win 
> there. 
> However, Eli's the Emacs maintainer and he has not yet been convinced to 
> change 
> GNU Emacs to be consistent with GNU grep.

AFAIU, Richard suggested to emit a warning from the byte compiler.
That might be a good-enough solution, better than signaling an error
at run time, IMO.