[GHC] #7905: Type checker barfs on nonsensical expression

11 May 2013

      #7905: Type checker barfs on nonsensical expression
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Reporter:  jpaugh              |          Owner:          
    Type:  bug                 |         Status:  new     
Priority:  normal              |      Component:  Compiler
 Version:  7.6.2               |       Keywords:          
      Os:  Linux               |   Architecture:  x86     
 Failure:  Compile-time crash  |      Blockedby:          
Blocking:                      |        Related:          
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 I got the infamous "impossible bug" by trying something nonsensical in my
 program. I reproduced the bug in the attached minimal program (18 lines).
 The precise error message is:

 {{{
 Impossible.hs:18:5:
     Couldn't match kind `* -> *' with `*'
     Expected type: [Char] -> ZT IO ()
       Actual type: [Char] -> ZT IO ()
     Kind incompatibility when matching types:
       [Char] :: * -> *
       [Char] :: *
     The function `lift'ghc: panic! (the 'impossible' happened)
   (GHC version 7.6.2 for i386-unknown-linux):
         kindFunResult ghc-prim:GHC.Prim.*{(w) tc 34d}
 }}}

 Note that this error occurs whether on not the ''MonadTrans'' instance is
 there.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7905
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