May confirm the bugfrom GNU Emacs 25.1.91.1 (i686-pc-linux-gnu, GTK+ 
Version 3.14.5)of 2017-01-02
With emacs -Q it opens quickly, but hangs when moving down.
Without -Q emacs freezes.

Assume the length of line is the reason, not the file resp. the mode.

BTW haskell-mode is developed at https://github.com/haskell



On 30.08.2017 16:38, Eli Zaretskii wrote:
>> 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.
>
>
>