[GHC] #810: GHC complains about missing instance in conjunction with GADTs

[GHC]

#810: GHC complains about missing instance in conjunction with GADTs
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  Reporter:  wolfgang at jeltsch.net  |          Owner:       
      Type:  bug                   |         Status:  new  
  Priority:  normal                |      Milestone:       
 Component:  Compiler              |        Version:  6.4.1
  Severity:  normal                |     Resolution:       
  Keywords:                        |             Os:  Linux
Difficulty:  Unknown               |   Architecture:  x86  
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Comment (by simonpj):

 The odd thing is that it works with 6.4.2 (batch, not GHCi).  Maybe Chris
 can try again?

 My comment about luck is simply that GHC is badly broken when it comes to
 a mixture of type classes and GADTs.  It's something high on my priority
 list, but for you can't rely on it to behave well, or even predictably.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/810>
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