[GHC] #8813: further support deriving instances Typeable1, Typeable2, etc

[GHC]

#8813: further support deriving instances Typeable1, Typeable2, etc
----------------------------+----------------------------------------------
       Reporter:  maeder    |             Owner:
           Type:  task      |            Status:  new
       Priority:  normal    |         Milestone:
      Component:  Compiler  |           Version:  7.8.1-rc1
       Keywords:            |  Operating System:  Unknown/Multiple
   Architecture:            |   Type of failure:  GHC rejects valid program
  Unknown/Multiple          |         Test Case:
     Difficulty:  Unknown   |          Blocking:
     Blocked By:            |
Related Tickets:            |
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 ghc-7.8.20140130 complains with

 {{{
     Not in scope: type constructor or class ‛Typeable2’
     Perhaps you meant ‛Typeable’ (imported from Data.Typeable)
 }}}

 changing Typeable2 to Typeable fixes it but is incompatible with ghc-7.6:

 {{{
     Expecting two more arguments to `Gr'
     In the stand-alone deriving instance for `Typeable Gr'
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8813>
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