Re: Emacs regexp scan (Sep 29)

[Paul Eggert <eggert@cs.ucla.edu>]

On 10/5/19 9:59 AM, Lars Ingebrigtsen wrote:
> what's so special about regexps that "[-+]" has to be mass-rewritten
> as "[+-]"?

There's no mass rewriting here. I changed regexps near other (more-complicated) 
regexps that didn't put "-" at the end, regexps that were in fact incorrect 
evidently due to their authors' confusion. Using a consistent style in a 
trouble-prone area can help avoid future bugs when someone changes that code in 
the future.

If you add regexps to Emacs in the future, I suggest putting literal "-" at the 
end of bracket expressions, since that's the style recommended in the manual for 
a solid technical reason, namely to avoid all-too-common confusion in this area 
that causes real bugs. That is why the regexp scanner flags these "-" instances: 
it finds real bugs, some of which were fixed in the most-recent patch in this 
area. Of course there's a cost-benefit analysis to doing lint checking like 
this. In this particular case, the number of actual bugs and the simplicity of 
pacifying the lint checker mean that the benefits of using the checker outweigh 
the cost.

That being said, there's no pressing need to go through all the Emacs code and 
rewrite [-+] to [+-], just as there's no pressing need to go through all the 
Emacs code and remove the useless and distracting "register" keyword.