[GHC] #12922: Kind classes compile with PolyKinds

[GHC]

#12922: Kind classes compile with PolyKinds
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        Reporter:  Tritlo            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Without thinking too deeply

 * `TypeInType` should imply `PolyKinds`.
 * `PolyKinds` should be enough for kind classes, if by "kind classes" you
 mean polymorphism over types of kind `Constraint`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12922#comment:5>
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