[GHC] #7800: Error message when deriving Typeable without PolyKinds

[GHC]

#7800: Error message when deriving Typeable without PolyKinds
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        Reporter:  monoidal                      |            Owner:
            Type:  bug                           |  dreixel
        Priority:  normal                        |           Status:  new
       Component:  Compiler                      |        Milestone:  7.8.1
      Resolution:                                |          Version:  7.7
Operating System:  Unknown/Multiple              |         Keywords:
 Type of failure:  Incorrect warning at          |     Architecture:
  compile-time                                   |  Unknown/Multiple
       Test Case:                                |       Difficulty:
        Blocking:                                |  Unknown
                                                 |       Blocked By:
                                                 |  Related Tickets:
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Comment (by monoidal):

 dreixel: I think it would be good to fix this before 7.8. Is it OK that I
 only edit the message to include "If you are deriving Typeable for a
 polykinded datatype, make sure PolyKinds is on"? This is rather blunt but
 it's a working solution.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7800#comment:3>
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