Subject: Maximally unhelpful diagnostic message.

From: Alan Mackenzie <[email-masked]>
Date: Tue, 29 Aug 2017 18:41:40 +0000

Hello, Emacs.

In GNU Emacs 25.2.3 (x86_64-unknown-linux-gnu, GTK+ Version 3.22.16)
of 2017-08-15 built on ACM
Configured using:
  'configure --with-gif=no --with-tiff=no --with-gpm'

Configured features:
XPM JPEG PNG RSVG SOUND GPM DBUS GSETTINGS NOTIFY ACL GNUTLS LIBXML2
FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11

I was just debugging some code when I was presented with the diagnostic:

    Assertion failed: (eq 10 (char-before))

.  Just that.  Nothing else.  No backtrace, no context, no nothing.
This is not helpful.

I request that consideration be given to providing one or more of these
details when assertion code triggers.

Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).