[GHC] #10865: Poly-kinded Const

[GHC]

#10865: Poly-kinded Const
-------------------------------------+-------------------------------------
              Reporter:  int-index   |             Owner:  ekmett
                  Type:  feature     |            Status:  new
  request                            |
              Priority:  normal      |         Milestone:
             Component:  Core        |           Version:  7.10.2
  Libraries                          |
              Keywords:  poly-       |  Operating System:  Unknown/Multiple
  kinded, Const                      |
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Currently `Const` is defined as

 {{{
 newtype Const a b = Const { getConst :: a }
 }}}

 I propose to define it poly-kinded in the second argument like so:

 {{{
 newtype Const a (b :: k) = Const { getConst :: a }
 }}}

 This should be completely backwards-compatible.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10865>
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