[GHC] #8560: undeducable Typeable error with data kinds when deriving Data for GADT in GHC version 7.7.20131122

[GHC]

#8560: undeducable Typeable error with data kinds when deriving Data for GADT in
GHC version 7.7.20131122
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        Reporter:  carter            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by carter):

 the key bit is that however I add typeable info for the datakind level
 variant of  Nat, i get

 {{{

 test.hs:33:1:
     No instance for (Typeable n)
       arising from the superclasses of an instance declaration
     In the instance declaration for ‛Data (Shape ('S n) a)’
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8560#comment:3>
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