[GHC] #15704: Different saturations of the same polymorphic-kinded type constructor aren't seen as apart types

[GHC]

#15704: Different saturations of the same polymorphic-kinded type constructor
aren't seen as apart types
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        Reporter:  mniip             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.6.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9371             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mniip):

 Considering `unify_tys` is called recursively from when `unify_ty` needs
 to match a constructor application, I think this functionality of
 "Maybe"ing out on lists of different lengths needs to be moved somewhere
 closer to coaxiom compatibility checking and further away from
 `unify_tys`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15704#comment:4>
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