[GHC] #15881: GHC Panic: data A n (a :: n) :: a -> Type

[GHC]

#15881: GHC Panic: data A n (a :: n) :: a -> Type
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        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.3
       Component:  Compiler          |              Version:  8.6.2
      Resolution:                    |             Keywords:  TypeInType
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 Iceland_jack):

 goes away if `a` is unused `data A n (a :: n) :: Type`

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15881#comment:1>
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