[GHC] #11714: Kind of (->) type constructor is overly constrained

[GHC]

#11714: Kind of (->) type constructor is overly constrained
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        Reporter:  bgamari           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
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 goldfire):

 > {{{#!hs
 > (->) :: forall (rep1 :: RuntimeRep) (rep2 :: RuntimeRep).
 >         TYPE rep1 -> TYPE rep2 -> *
 > }}}

 Yes, this is exactly what we need. But I daresay this will be a
 performance disaster, littering Core with extra `RuntimeRep` arguments at
 every arrow, and requiring a substitution to get `->`'s kind.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11714#comment:2>
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