Subject: bug#29159: 27.0.50; Hang in HTML/CSS code

From: Stefan Monnier <[email-masked]>
Date: Sat, 25 Nov 2017 21:17:20 -0500

> In this particular example, `mhtml--extend-font-lock-region' wants to
> leave `font-lock-beg' at 40 while `font-lock-extend-region-multiline'
> wants it at 39, resulting in an endless back and forth.

Could you give some details?
Functions on font-lock-extend-region-functions should *never* shrink
a region (since that risks inf-looping, obviously).  After all, it's
called "...-extend-...", right?

So if font-lock-extend-region-multiline puts beg at 39, it's incorrect
for mhtml--extend-font-lock-region to move it back to 40.

        Stefan