From: Mike Dupont <jamesmikedupont@googlemail.com>
Date: Wed, 30 Aug 2017 06:03:56 -0400

Load this large haskell file
it hangs emacs, I think it is something in the mode.

https://github.com/h4ck3rm1k3/gcc-ontology/blob/7889b822218950fcdc414a4e054d6e7bb4a3e52e/tests/test_haskell1_b.hs

It doesn't hang here, neither with Emacs 24.5 nor with the current
master.  It displays the first screenful rather quickly, and then
works very sluggishly, even at the beginning of the buffer, much worse
at the end.  But the latter is a known issue: this file is a single
11MB line of text, and Emacs's display is very slow with such long
lines.