[GHC] #14179: "Conflicting family instance" error pretty prints data family instances poorly

[GHC]

#14179: "Conflicting family instance" error pretty prints data family instances
poorly
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4711
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * status:  new => patch
 * differential:   => Phab:D4711


Comment:

 Replying to [comment:3 simonpj]:
 > PS: The first sentence of comment:2 doesn't make sense though: "pretty-
 print conflicting data family instances slightly differently than
 conflicting data family instances".  Maybe needs an edit.

 Good catch. Fixed.

 Alas, I wasn't able to do much about the kind signature thing, since by
 the time we call this error message, we've completely lost track of
 whether the original data family instance declaration was written with an
 explicit kind signature or not. Nevertheless, I've implemented the other
 suggestions in this thread in Phab:D4711, which substantially cleans up
 the error message (and will at the very least give results that make sense
 in //some// context).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14179#comment:4>
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