[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 dmcclean):

 Great point. Not sure what I was thinking, sorry.

 Regarding "If I have a function `f :: forall (b :: Bool). Proxy b ->
 String` then `f`'s behavior cannot depend on the choice of `b`", I think I
 got off track by thinking that the binding happens in two stages, and that
 when type type-level lambda was applied it could "pick" which term-level
 function it wanted to return after inspecting the type argument, and that
 all of that always happened at compile time. But it doesn't.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9568#comment:3>
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