[GHC] #9568: Type classes that fully cover closed kinds

[GHC]

#9568: Type classes that fully cover closed kinds
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              Reporter:  dmcclean    |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:  ⊥
              Priority:  lowest      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:
  (Type checker)                     |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:
       Type of failure:              |
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by goldfire):

 I agree fully with Reid (rwbarton). Those "class constraints" are really,
 under the hood, implicit parameters (dictionaries) passed around at
 runtime. Given that they have runtime significance, I don't think it's a
 good idea to hide them from the programmer.

 On the relationship to Pi-types: As described in
 [https://www.youtube.com/watch?v=O805YjOsQjI this video] and
 [wiki:DependentHaskell this wiki page], I'm working on a version of GHC
 that allows a type parameter to be made available at runtime. This feature
 could be used to simulate dictionary passing (I believe), by examining the
 type parameter at runtime and making decisions based on it. So, I guess
 this might improve the syntax a bit -- hard to say for sure at this point.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9568#comment:2>
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