[GHC] #12989: ($) can have a more general type

[GHC]

#12989: ($) can have a more general type
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |             Keywords:
      Resolution:                    |  LevityPolymorphism
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 andrewthad):

 One drawback of giving `($)` the more general type is than `(&)` can no
 longer be made symmetric with it. That is, we have no way of writing:

 {{{
 (&) :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep)
               (a :: TYPE r1) (b :: TYPE r2).
        a -> (a -> b) -> b
 }}}

 This probably isn't that big of a deal, but it is a little weird.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12989#comment:4>
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