[GHC] #4370: Bring back monad comprehensions

[GHC]

#4370: Bring back monad comprehensions
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  Reporter:  simonpj           |          Owner:                  
      Type:  feature request   |         Status:  new             
  Priority:  normal            |      Milestone:  _|_             
 Component:  Compiler          |        Version:  6.12.3          
Resolution:                    |       Keywords:                  
        Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown      |     Difficulty:                  
  Testcase:                    |      Blockedby:                  
  Blocking:                    |        Related:                  
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Comment(by carter):

 does some of the constraint kinds / poly kinds machinery allow the
 remainder of this ticket to be addressed?

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4370#comment:67>
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