[GHC] #11600: Panic (ASSERT failed) in compiler/types/TyCoRep.hs:1939

[GHC]

#11600: Panic (ASSERT failed) in compiler/types/TyCoRep.hs:1939
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        Reporter:  hvr               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by hvr):

 Fyi, here's the same panic with a slightly newer snapshot of GHC HEAD
 (i.e. a008eadfaa4816be349b4fefde9b9b9edc1ca359), but this time
 bootstrapped with GHC 8.0 (and thus CallStack support):

 {{{
 "inplace/bin/ghc-stage1" -hisuf dyn_hi -osuf  dyn_o -hcsuf dyn_hc -fPIC
 -dynamic  -O0 -H64m -Wall -fllvm-fill-undef-with-garbage    -Werror
 -hide-all-packages -i -ighc/. -ighc/stage2/build
 -ighc/stage2/build/autogen -Ighc/stage2/build -Ighc/stage2/build/autogen
 -optP-DGHCI -optP-include -optPghc/stage2/build/autogen/cabal_macros.h
 -package-id array-0.5.1.0 -package-id base-4.9.0.0 -package-id
 bytestring-0.10.7.0 -package-id containers-0.5.7.1 -package-id
 deepseq-1.4.2.0 -package-id directory-1.2.5.1 -package-id filepath-1.4.1.0
 -package-id ghc-8.1 -package-id ghc-boot-8.1 -package-id ghci-8.1
 -package-id haskeline-0.7.2.2 -package-id process-1.4.2.0 -package-id
 time-1.6 -package-id transformers-0.5.2.0 -package-id unix-2.7.2.0 -Wall
 -fno-warn-name-shadowing -XHaskell2010  -O -dcore-lint -no-hs-main
 -threaded -no-user-package-db -rtsopts      -Wnoncanonical-monad-instances
 -odir ghc/stage2/build -hidir ghc/stage2/build -stubdir ghc/stage2/build
 -c ghc/./GHCi/UI.hs -o ghc/stage2/build/GHCi/UI.dyn_o
 WARNING: file compiler/specialise/Specialise.hs, line 1173
   Missed specialisation opportunity for $fMonadIOExceptT_$cliftIO
   [] 2 [] 1 [ALWAYS]
 WARNING: file compiler/specialise/Specialise.hs, line 1173
   Missed specialisation opportunity for $w$c<*>
   [] 2 [] 1 [0]
 ghc-stage1: panic! (the 'impossible' happened)
   (GHC version 8.1.20160218 for x86_64-unknown-linux):
         ASSERT failed!
   CallStack (from HasCallStack):
   assertPprPanic, called at compiler/types/TyCoRep.hs:1932:56 in
 ghc:TyCoRep
   checkValidSubst, called at compiler/types/TyCoRep.hs:2076:17 in
 ghc:TyCoRep
   substCo, called at compiler/coreSyn/CoreSubst.hs:605:20 in ghc:CoreSubst
   in_scope InScope {fromTarget_aiKD pprTT_aj4s pp_resume_aj4J
 ...
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11600#comment:6>
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