[GHC] #12592: Explicit type signature for type classes fails

[GHC]

#12592: Explicit type signature for type classes fails
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 This is expected behavior. I think the problem is that you're confusing a
 type with its kind. In the definition for `IxCopointed` above, your kind
 for w -- `IxFunct i` or `i -> i -> Type -> Type` -- implies that the type
 of `i` is `i`, which is not what you mean. That is, when you say `w ::
 IxFunct i`, then the first two arguments to `w` should have ''kind'' `i`,
 not necessarily ''be'' `i`.

 Does this clarify? And I don't see a way to improve the error message
 (beyond the general improvement our error messages would enjoy). If so,
 please close the ticket.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12592#comment:1>
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