[GHC] #9000: Kind checking fails when using PolyKinds

[GHC]

#9000: Kind checking fails when using PolyKinds
-------------------------------------+-------------------------------------
       Reporter:  facundo.dominguez  |             Owner:
           Type:  bug                |            Status:  new
       Priority:  normal             |         Milestone:
      Component:  Compiler (Type     |           Version:  7.8.2
  checker)                           |  Operating System:  Linux
       Keywords:                     |   Type of failure:  GHC rejects
   Architecture:  x86_64 (amd64)     |  valid program
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
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 GHC HEAD and earlier versions are failing on the following program:

 {{{
 {-# LANGUAGE PolyKinds #-}
 import GHC.Exts(Any)
 f = (undefined :: a -> m a) :: Any -> Any Any
 }}}

 {{{
 ../tmp/test-polykinds.hs:3:6:
     Couldn't match kind ‘k1’ with ‘*’
       ‘k1’ is a rigid type variable bound by
            an expression type signature: Any -> Any Any
            at ../tmp/test-polykinds.hs:3:5
     Expected type: Any -> Any Any
       Actual type: Any -> m0 Any
     In the expression: (undefined :: a -> m a) :: Any -> Any Any
     In an equation for ‘f’:
         f = (undefined :: a -> m a) :: Any -> Any Any
 }}}

 Rewriting the program as follows has compilation succeed.
 {{{
 f = (undefined :: a -> m a) `asTypeOf` (undefined :: Any -> Any Any)
 }}}

 And removing the {{{PolyKinds}}} extension also has compilation succeed.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9000>
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