bug#23833: 24.5; assoc-string with CASE-FOLD may fail

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 23 Jun 2016 19:19:09 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: ynyaaa@gmail.com, 23833@debbugs.gnu.org
> 
> > From: Noam Postavsky <npostavs@users.sourceforge.net>
> > Date: Thu, 23 Jun 2016 11:53:00 -0400
> > Cc: ynyaaa@gmail.com, 23833@debbugs.gnu.org
> > 
> > Would it not make more sense if upcase converted dz into DZ?
> 
> We want to go by what UnicodeData.txt says:
> 
>   01F1;LATIN CAPITAL LETTER DZ;Lu;0;L;<compat> 0044 005A;;;;N;;;;01F3;01F2
>   01F2;LATIN CAPITAL LETTER D WITH SMALL LETTER Z;Lt;0;L;<compat> 0044 007A;;;;N;;;01F1;01F3;01F2
>   01F3;LATIN SMALL LETTER DZ;Ll;0;L;<compat> 0064 007A;;;;N;;;01F1;;01F2
> 
> The problem here is that both DZ and Dz name dz as their lower-case
> variant, and Emacs can only have one pair.  So we chose the other one
> for the upcase conversion.  We could switch them, but one of them will
> necessarily be lost, this way or another.

On second thought, I think you are right, and swapping the pairs will
yield better results, so I've just did that on master for these and a
few other similar characters.

Of course, this doesn't resolve the original issue in any way, since
characters that have title-case will still fail the OP's test.

Thanks.