[GHC] #13202: Levity polymorphism panic in GHCi

[GHC]

#13202: Levity polymorphism panic in GHCi
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       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 adamgundry):

 I've just seen this as well, in a different context:
 {{{
 GHCi, version 8.1.20170217: http://www.haskell.org/ghc/  :? for help
 Prelude> import GHC.Records
 Prelude GHC.Records> :set -XTypeApplications -XDataKinds
 Prelude GHC.Records> let foo = getField @"name"
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.1.20170217 for x86_64-unknown-linux):
         isUnliftedType
   forall (a :: TYPE q). a :: TYPE q
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1197:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1201:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:1889:10 in ghc:Type
         isUnliftedType, called at compiler/typecheck/TcRnDriver.hs:1822:32
 in ghc:TcRnDriver

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13202#comment:1>
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