[GHC] #14175: Panic repSplitTyConApp_maybe

[GHC]

#14175: Panic repSplitTyConApp_maybe
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.2
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13910            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * cc: RyanGlScott (added)


Comment:

 I suspect that this program (which panics after
 0829821a6b886788a3ba6989e57e25a037bb6d05 on GHC HEAD) has the same
 underlying symptom:

 {{{#!hs
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TypeFamilies #-}
 module Bug where

 class C k where
   data CD :: k -> k -> *

 instance C (Maybe a) where
   data CD :: (k -> *) -> (k -> *) -> *
 }}}
 {{{
 $ inplace/bin/ghc-stage2 --interactive ../Bug.hs
 GHCi, version 8.3.20170818: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 1] Compiling Bug              ( ../Bug.hs, interpreted )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.3.20170818 for x86_64-unknown-linux):
         getRuntimeRep
   k_a1v3[sk:1] :: k_a1vl[tau:1]
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1142:37 in
 ghc:Outputable
         pprPanic, called at compiler/types/Type.hs:1982:18 in ghc:Type
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14175#comment:2>
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