RE: :alnum: broken?

[Drew Adams]

> The less experienced users, which are those who fall the most on the
> trap (me raises hand) hardly would benefit from a compiler warning. We
> use regexps on interactive *-regexp commands, not on Elisp code that we
> later compile. That's package writers.

That's definitely true, IMO.  But:

1. Warning during regexp input (e.g. regexp Isearch)
   would likely, itself, be quite confusing or
   annoying.

2. There are _lots_ of regexp-learning gotchas. The
   case currently discussed is just one such.  Any
   attempt to interrupt input with some guidance
   wrt what a user might be doing wrong would truly
   be a distraction to lots of other users, and
   even the same user sometimes, and at some point.

   It could be imagined that Emacs could provide a
   mode that helps users in such ways, but it would
   need to be quite smart and configurable.

   The differences in help level needed for different
   users make that alone problematic.  Ideally,
   perhaps, such help would watch a given user and
   learn over time (machine-learning) just what
   kinds of help might be most appropriate.