[GHC] #13780: Nightmarish pretty-printing of equality type in GHC 8.2 error message

[GHC]

#13780: Nightmarish pretty-printing of equality type in GHC 8.2 error message
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13819            |  Differential Rev(s):  Phab:D3794
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ryan Scott <ryan.gl.scott@…>):

 In [changeset:"424ecadbb3d06f4d4e0813de670369893e1da2a9/ghc"
 424ecadb/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="424ecadbb3d06f4d4e0813de670369893e1da2a9"
 Add regression tests for #13601, #13780, #13877

 Summary:
 Some recent commits happened to fix other issues:

 * c2417b87ff59c92fbfa8eceeff2a0d6152b11a47 fixed #13601 and #13780
 * 8e15e3d370e9c253ae0dbb330e25b72cb00cdb76 fixed the original program in
 #13877

 Let's add regression tests for each of these to ensure they stay fixed.

 Test Plan: make test TEST="T13601 T13780a T13780c T13877"

 Reviewers: goldfire, bgamari, austin

 Reviewed By: bgamari

 Subscribers: rwbarton, thomie

 GHC Trac Issues: #13601, #13780, #13877

 Differential Revision: https://phabricator.haskell.org/D3794
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13780#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler