bug#42602: Wrong (not-)casechars value for "polish" in ispell-dictionary-base-alist

[Eli Zaretskii <eliz@gnu.org>]

> From: Sebastian Urban <mrsebastianurban@gmail.com>
> Date: Wed, 29 Jul 2020 18:12:02 +0200
> 
> for words like:
>     męski
>     miód
>     klątwa
>     ślad
>     łuk
>     żaba
>     źrebak
>     grzać
>     bańka
> ispell.el sends to Aspell only part of the word, e.g. "lad" instead of
> "ślad", or "kl"/"twa" (depending on the cursor position) instead of
> "klątwa".
> 
> I think this is because wrong value of (NOT-)CASECHARS, which is ASCII
> A-z letters and a few chars of which only ó/Ó is valid for Polish.
> 
> Although, for some reason, it doesn't recognize "ó" in word "miód",
> sending "mi" or "d". It is on the list of CASECHARS under \363, so it
> should work.  Moreover, if I type in regexp-builder "[\363\323]" it
> won't recognize ó/Ó, but it doesn't have a problem with other Polish
> chars, like "ł" ("[\502]") or "ż" ("[\574]").
> 
> If I put in my init.el:
> --8<---------------cut here---------------start------------->8---
> (setq ispell-program-name "C:/cygwin64/bin/aspell")
> (add-hook 'ispell-initialize-spellchecker-hook
>            (lambda ()
>            (add-to-list 'ispell-local-dictionary-alist
>                         '("pl"
>                           ;; "[[:alpha:]]"
>                           ;; "[^[:alpha:]]"
>                           ;; ęóąśłżźćńĘÓĄŚŁŻŹĆŃ
> "[A-Za-z\431\363\405\533\502\574\572\407\504\430\323\404\532\501\573\571\406\503]"
> "[^A-Za-z\431\363\405\533\502\574\572\407\504\430\323\404\532\501\573\571\406\503]"
>                           "[.]" nil nil nil iso-8859-2))))
> (setq ispell-dictionary "pl")
> --8<---------------cut here---------------start------------->8---
> 
> everything seems to work, even ó/Ó are recognised.

I don't understand this change.  Values above octal 377 cannot be
right in the above regexps, because they are supposed to be in Latin-2
encoding, which is a single-byte encoding, and so can only handle
values below octal 400.  How did you come up with those values?

Anyway, I'm quite sure some other factor is at work here.

> Tested on:
> - GNU Emacs 26.3 (build 1, x86_64-w64-mingw32) of 2019-08-29,
> - GNU Emacs 28.0.50 (build 1, x86_64-w64-mingw32) of 2020-07-05,
> with Aspell from Cygwin installation.

Your Emacs is a native MinGW build, whereas Aspell seems to be a
Cygwin build?  If so, you could have incompatibility in character
encoding.  What is your Windows locale?  And what does

  M-: (getenv "LANG") RET

yield inside Emacs?