[GHC] #9858: Typeable instances should be kind-aware

[GHC]

#9858: Typeable instances should be kind-aware
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        Reporter:  dreixel           |                   Owner:  dreixel
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.1
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by Ptharien's Flame):

 If I may interject from the outside (so to speak), I think the best way to
 explain Simon's proposition (1) is in terms of parametricity, in a manner
 akin to the widely-expounded-upon use of monadic effects in Haskell.
 Adding a `Typeable` constraint is just like surrounding a type with `IO`:
 it allows more operations, while simultaneously marking the code as not-
 quite-pure in a specific way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9858#comment:23>
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