[GHC] #15883: GHC panic: newtype F rep = F (forall (a :: TYPE rep). a)

[GHC]

#15883: GHC panic: newtype F rep = F (forall (a :: TYPE rep). a)
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.3
          Component:  Compiler       |           Version:  8.6.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 {{{#!hs
 {-# Language RankNTypes     #-}
 {-# Language KindSignatures #-}
 {-# Language PolyKinds      #-}

 import GHC.Exts

 newtype Foo rep = MkFoo (forall (a :: TYPE rep). a)
 }}}

 {{{
 $ ~/code/unmodifiedghc/inplace/bin/ghc-stage2 --interactive -ignore-dot-
 ghci /tmp/U.hs
 GHCi, version 8.7.20181029: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( /tmp/U.hs, interpreted )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.7.20181029 for x86_64-unknown-linux):
         isUnliftedType
   forall (a :: TYPE rep_a1AA[sk:0]). a :: TYPE rep_a1AA[sk:0]
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:2332:10 in ghc:Type
         isUnliftedType, called at
 compiler/typecheck/TcTyClsDecls.hs:3055:25 in ghc:TcTyClsDecls

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

 >
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15883>
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