[GHC] #10432: panic with kind polymorphism

[GHC]

#10432: panic with kind polymorphism
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        Reporter:  Ashley Yakeley    |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.10.1
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 This works in HEAD, but another variant makes HEAD, too, fail in the same
 way `No skolem info`:
 {{{
 matchReflK2 :: forall (a :: ka) (b :: kb) (r :: *).
               ('WrapType a :~: 'WrapType b) ->  r
 matchReflK2 x
  = let foo :: ('WrapType a ~ 'WrapType b) => r
        foo = undefined
    in undefined
 }}}
 Reason: the type of `foo` mentions `a`, `b`, `r` as free variables; the
 ambiguity check doesn't bind them; the error message generator falls over.

 Need to look into this.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10432#comment:1>
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