[GHC] #5935: Failure to resolve AnyK

[GHC]

#5935: Failure to resolve AnyK
---------------------------------------+------------------------------------
 Reporter:  goldfire                   |          Owner:                         
     Type:  bug                        |         Status:  new                    
 Priority:  normal                     |      Component:  Compiler (Type checker)
  Version:  7.4.1                      |       Keywords:  DataKinds PolyKinds    
       Os:  Unknown/Multiple           |   Architecture:  Unknown/Multiple       
  Failure:  GHC rejects valid program  |       Testcase:                         
Blockedby:                             |       Blocking:                         
  Related:                             |  
---------------------------------------+------------------------------------
 Consider the following code:

 {{{
 {-# LANGUAGE PolyKinds,
              GADTs,
              DataKinds,
              KindSignatures
  #-}

 data SList a where
   SNil :: SList '[]

 x :: SList ('[] :: [Bool])
 x = SNil
 }}}

 Compiling this code causes GHC to emit an error saying that {{{AnyK}}}
 cannot be unified with {{{Bool}}}. It seems that {{{AnyK}}} is a
 placeholder for an undetermined kind and that it should unify with any
 well-formed kind.

 As a much smaller issue, the error emitted speaks about "types" where it
 means "kinds".

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5935>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler