bug#35614: AUCTeX stopped working after upgrade: TeX-shdex-eval: Invalid dialect expression : :classopt.

[Ikumi Keita]

Hi Jakub,

>>>>> Jakub Narębski <address@hidden> writes:
> Thankfully I use version of GNU Emacs with AUCTeX preinstalled,
> so uninstalling ELPA version made AUCTeX work as workaround
> (AUCTeX-date "2017-06-03", from
> https://vigou3.github.io/emacs-modified-windows/)

Preinstalled version.  Well, that seems to be the reason of fail.
Having a look at the page linked from the page presented above, the
site-start.el file[1] contains lines
----------------------------------------------------------------------
(load "auctex.el" nil t t)
(load "preview-latex.el" nil t t)
----------------------------------------------------------------------
.  This indicates that the preinstalled AUCTeX was not installed from
ELPA, but by the traditional configure-make-make_install method.  Then,
installing from ELPA doubles the instance of AUCTeX and they conflict to
each other.

If you still want to use the updated version from ELPA, it is necessary
to do either of the following two options:
1. Uninstall the preinstalled version of AUCTeX before using ELPA
2. Perform the configure-make-make_install method for the development
   version of AUCTeX source taken from the git repository, after
   installing unix-like shell on your windows.

The option 1 consists of removing all the AUCTeX-related files and the
activation codes quoted above from your PC.

Regards,
Ikumi Keita

[1] 
https://gitlab.com/vigou3/emacs-modified-windows/blob/v26.2-modified-1/site-start.el