[GHC] #14734: QuantifiedConstraints conflated with impredicative polymorphism?

[GHC]

#14734: QuantifiedConstraints conflated with impredicative polymorphism?
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:  invalid           |             Keywords:
                                     |  QuantifiedConstraints wipT2893
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Iceland_jack):

 Btw, should the following work?

 {{{#!hs
 GHCi, version 8.5.20180128: http://www.haskell.org/ghc/  :? for help
 Prelude> :set -XGADTs -XQuantifiedConstraints -XConstraintKinds
 Prelude> data Imp a b where Imp :: (a => b) => Imp a b
 Prelude> :kind forall a b. Imp a (b => a)
 forall a b. Imp a (b => a) :: *
 Prelude>
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14734#comment:7>
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