bug#48871: 27.2; Unusably slow in C# mode

[Eli Zaretskii <eliz@gnu.org>]

> From: jan <rtm443x@googlemail.com>
> Date: Sun, 6 Jun 2021 14:34:19 +0100
> Cc: 48871@debbugs.gnu.org
> 
> had already tried the -Q option. Emacs started but when I tried "M-x
> csharp-mode" it didn't recognise it. I tried exactly the same on the
> normally-started emacs to check I was entering it correctly and that
> did understand it.
> I guess the -Q effectively disables some modes? I was surprised.
> 
> Yep, customisation may well  be the issue here.

So let's try to figure out why "emacs -Q" fails to load csharp-mode.
Since there's no such mode bundled with Emacs, I guess you downloaded
it from somewhere?  Then try this:

  emacs -Q
  M-x load-file RET /path/to/csharp-mode.el RE

The last line assumes that the Lisp file which defines the function
csharp-mode is called csharp-mode.el; if not, change the file name to
fit the reality.  Also, "/path/to/" should be replaced with the actual
absolute file name of the file on your system.

Then say what you tried:

   M-x csharp-mode RET

If that still doesn't work, please show the error messages.  Likely
they will identify packages csharp-mode depends on that you also need
to load with "M-x load-file".

> I have a file of equivalent size which should demo the issue but can't
> zip it as gmail blocks anything with a zip attached, I can post as
> attachment directly but it's 220KBytes, you ok with that on your
> mailing list?

Yes, it's okay.  But let's first try and see whether "emacs -Q"
exhibits the same problem, okay?