[GHC] #14190: Typeable imposes seemingly redundant constraints on polykinded instances

[GHC]

#14190: Typeable imposes seemingly redundant constraints on polykinded instances
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:  Typeable
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4000
       Wiki Page:                    |
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Comment (by simonpj):

 > Without it, we have no way to get the kinds of the pieces once we
 decompose

 I think it would be useful to give a concrete example of this, and put
 that example in a Note with the code for `typeRepKind`.

 So far I have always supposed that it's a convenience mechanism: you can
 always pass a `TypeRep` for the kind separately.  But maybe I'm wrong.

 I'm not against `typeRepKind`, just wanting a slam-dunk argument that we
 need it.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14190#comment:12>
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