[GHC] #14563: GHC Panic with TypeInType / levity polymorphism

[GHC]

#14563: GHC Panic with TypeInType / levity polymorphism
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:                 |  Operating System:  Unknown/Multiple
  LevityPolymorphism, TypeInType     |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  #14555
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 This code is rightfully rejected.

 {{{#!hs
 -- {-# Language TypeInType #-}
 {-# Language RankNTypes, KindSignatures, PolyKinds #-}

 import GHC.Types (TYPE)
 import Data.Kind

 data Lan (g::TYPE rep -> TYPE rep') (h::TYPE rep -> TYPE rep'') a where
 Lan :: forall xx (g::TYPE rep -> TYPE rep') (h::TYPE rep -> Type) a. (g xx
 -> a) -> h xx -> Lan g h a
 }}}

 But uncomment first line and it panics

 {{{
 $ ghci2 ~/hs/132-bug.hs
 GHCi, version 8.3.20171122: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( /home/baldur/hs/132-bug.hs,
 interpreted )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.3.20171122 for x86_64-unknown-linux):
         zonkTcTyVarToVar
   'LiftedRep
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1147:37 in
 ghc:Outputable
         pprPanic, called at compiler/typecheck/TcType.hs:1640:17 in
 ghc:TcType

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

 >
 }}}

 Maybe the same as #14555.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14563>
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