[GHC] #2893: Implement "Quantified constraints" proposal

[GHC]

#2893: Implement "Quantified constraints" proposal
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        Reporter:  porges            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler          |              Version:  6.10.1
      Resolution:                    |             Keywords:
                                     |  QuantifiedConstraints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #5927             |  Differential Rev(s):  Phab:D4353
       Wiki Page:                    |
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Comment (by Iceland_jack):

 `f` should have an `Ord a` constraint right?


 {{{#!hs
 f :: (Ord a, forall x. Ord x => Ord (m x)) => m a -> m a -> Bool
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2893#comment:36>
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