[GHC] #7015: Add support for 'static'

[GHC]

#7015: Add support for 'static'
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              Reporter:  edsko       |            Owner:
                  Type:  feature     |           Status:  patch
  request                            |        Milestone:  7.10.1
              Priority:  normal      |          Version:  7.4.2
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D119   |
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Comment (by simonpj):

 Edsko my remark about a "hack" was not intended as a criticism. Of course,
 if GHC is inadequate you must hack around its shortcomings.  My intent was
 solely this: let's not enshrine a temporary hack into the design of the
 language that GHC implements.

 There are two things going on in this ticket:

  * What should be the specification of the feature that GHC implements?
 I think we are agreeing that: the argument of `static` should have no free
 type variables.  Let's put that into the spec.[[BR]][[BR]]
  That leaves open the question of adding an impredicative-like feature,
 the ability to have terms of type `Static (forall a. [a] -> [a])`, which
 make perfect sense, have no free type variables, but which are disallowed
 at present.

  * Given the above restriction, and the absence of the impredicative
 support, how can we hack around the restriction to get something like
 polymorphism.  This is the `Any` discussion on #9429.  Even lacking a fix
 for poly-kinded `Any`, it's not a disaster because for any particular kind
 we can always do the job; it's just a bit inelegant.

 If we agree about these things, perhaps you can update the wiki page as
 above and we can go from there.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7015#comment:26>
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