bug#11309: 24.1.50; Case problems with [:upper:] and Cyrillic, Greek

[Lars Ingebrigtsen <larsi@gnus.org>]

Aidan Kehoe <kehoea@parhasard.net> writes:

> (let ((case-fold-search t))
>   (string-match "[[:upper:]]" "a\u0686"))
> => 0 ;; As documented
>
> (upcase "\u0430") ;; CYRILLIC SMALL LETTER A
> => "А" ;; "\u0410", so it's in the case table
>
> (let ((case-fold-search t))
>   (string-match "[[:upper:]]" "\u0430\u0686"))
> => nil ;; Ah, this is unexpected.

I tried this in Emacs 28, and I can confirm that this behaviour is still
present.

> (let ((case-fold-search t))
>   (string-match "[[:lower:]]" "\u0410\u0686"))
> => 0 ;; But this works as documented. 
>
> (upcase "\u03b2") ;; GREEK SMALL LETTER BETA
> => "Β" ;; "\u0392", it's in the case table
>
> (let ((case-fold-search t))
>   (string-match "[[:upper:]]" "\u03b2\u5357"))
> => nil ;; Oops
>
> (let ((case-fold-search t))
>   (string-match "[[:lower:]]" "\u0392\u5357"))
> => 0 ;; But this works, again. 

And this, too.

Anybody have any insight here?

-- 
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   bloggy blog: http://lars.ingebrigtsen.no