[GHC] #5937: Kind variables not allowed in data declaration kind annotation

[GHC]

#5937: Kind variables not allowed in data declaration kind annotation
---------------------------------------+------------------------------------
 Reporter:  goldfire                   |          Owner:                         
     Type:  bug                        |         Status:  new                    
 Priority:  normal                     |      Component:  Compiler (Type checker)
  Version:  7.5                        |       Keywords:  PolyKinds              
       Os:  Unknown/Multiple           |   Architecture:  Unknown/Multiple       
  Failure:  GHC rejects valid program  |       Testcase:                         
Blockedby:                             |       Blocking:                         
  Related:                             |  
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 GHC won't accept kind variables stated directly in a data declaration. For
 example, the following does not compile:

 {{{
 data SMaybe :: (k -> *) -> Maybe k -> * where
   SNothing :: SMaybe s 'Nothing
   SJust :: s a -> SMaybe s ('Just a)
 }}}

 However, the following does compile:

 {{{
 data SMaybe' (s :: k -> *) (m :: Maybe k) where
   SNothing' :: SMaybe' s 'Nothing
   SJust' :: s a -> SMaybe' s ('Just a)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5937>
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