bug#37659: rx additions: anychar, unmatchable, unordered-or

[Mattias Engdegård]

13 feb. 2020 kl. 20.30 skrev Eli Zaretskii <eliz@gnu.org>:

> Fine with me, thanks.

Thank you, pushed.

Now only the 'compositionality' patch remains. As noted it could be done on 
master, but since it is motivated by user-defined forms which were introduced 
in Emacs 27, I'd rather like it to be done in that branch.

It simply seems a bit incomplete otherwise. Users read about the longest-match 
guarantee of 'or', and of user-definitions, and look for a way of combining the 
two. Perhaps they try

(rx-let ((arith-op (or "+" "-" "*" "/"))
         (assign-op (or "=" "+=" "-=" "*=" "/="))
         (op (or arith-op assign-op)))
...)

which doesn't quite work for matching "+=", say.