Re: [GHC] #13959: substTyVar's definition is highly dubious

12 Jul 2017

      #13959: substTyVar's definition is highly dubious
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       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:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 Here's a much more detailed stack trace when compiling
 `Data.Type.Equality`:

 {{{
 $ inplace/bin/ghc-stage2 -fforce-recomp -O2 -DDEBUG -dcore-lint Bug.hs
 [1 of 1] Compiling Data.Type.Equality ( Bug.hs, Bug.o )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.3.20170712 for x86_64-unknown-linux):
         ASSERT failed!
   in_scope InScope {k1_X49O a_X49V b_X49X}
   tenv [X49T :-> k1_X49O, X49V :-> a_X49V, X49X :-> b_X49X]
   tenvFVs [X49M :-> k2_X49M, X49O :-> k1_X49O, X49V :-> a_X49V,
            X49X :-> b_X49X]
   cenv []
   cenvFVs []
   tys [*]
   cos []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1188:22 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2089:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2122:29 in
 ghc:TyCoRep
         substTy, called at compiler/types/TyCoRep.hs:2198:44 in
 ghc:TyCoRep
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/utils/Outputable.hs:1186:5 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2089:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2122:29 in
 ghc:TyCoRep
         substTy, called at compiler/types/TyCoRep.hs:2198:44 in
 ghc:TyCoRep
 CallStack (from -prof):
   Panic.panic (compiler/utils/Panic.hs:(182,1)-(186,68))
   Outputable.pprDebugAndThen
 (compiler/utils/Outputable.hs:(1191,1)-(1194,43))
   ErrUtils.prettyPrintGhcErrors.\
 (compiler/main/ErrUtils.hs:(658,23)-(666,44))
   GhcMonad.gcatch.\.\ (compiler/main/GhcMonad.hs:117:46-63)
   Panic.throwGhcException (compiler/utils/Panic.hs:171:1-35)
   Panic.panicDoc (compiler/utils/Panic.hs:192:1-61)
   Outputable.pprPanic (compiler/utils/Outputable.hs:1137:1-49)
   Outputable.assertPprPanic
 (compiler/utils/Outputable.hs:(1185,1)-(1188,35))
   TyCoRep.checkValidSubst (compiler/types/TyCoRep.hs:(2088,1)-(2113,57))
   TyCoRep.substTy (compiler/types/TyCoRep.hs:(2120,1)-(2123,45))
   Var.updateTyVarKind (compiler/basicTypes/Var.hs:456:1-64)
   TyCoRep.substTyVar (compiler/types/TyCoRep.hs:(2194,1)-(2198,61))
   TyCoRep.subst_ty.go (compiler/types/TyCoRep.hs:(2176,5)-(2191,60))
   TyCoRep.subst_ty (compiler/types/TyCoRep.hs:(2173,1)-(2191,60))
   TyCoRep.subst_co.go_ty (compiler/types/TyCoRep.hs:2240:5-26)
   TyCoRep.subst_co.go (compiler/types/TyCoRep.hs:(2243,5)-(2264,66))
   TyCoRep.subst_co (compiler/types/TyCoRep.hs:(2236,1)-(2270,36))
   TyCoRep.substCoUnchecked (compiler/types/TyCoRep.hs:(2223,1)-(2225,33))
   TyCoRep.substCoWithUnchecked
 (compiler/types/TyCoRep.hs:(2045,1)-(2047,41))
   Coercion.mkInstCo (compiler/types/Coercion.hs:(950,1)-(952,31))
   CoreOpt.pushCoTyArg.co2 (compiler/coreSyn/CoreOpt.hs:1012:5-62)
   CoreOpt.pushCoTyArg (compiler/coreSyn/CoreOpt.hs:(990,1)-(1012,62))
   Simplify.simplCast.addCoerce
 (compiler/simplCore/Simplify.hs:(1427,8)-(1461,53))
   Simplify.simplCast (compiler/simplCore/Simplify.hs:(1421,1)-(1461,53))
   Simplify.rebuildCall (compiler/simplCore/Simplify.hs:(1761,1)-(1853,47))
   Simplify.completeCall
 (compiler/simplCore/Simplify.hs:(1718,1)-(1749,60))
   Simplify.simplIdF (compiler/simplCore/Simplify.hs:(1680,1)-(1712,53))
   Simplify.simplExprC (compiler/simplCore/Simplify.hs:(1035,1)-(1041,42))
   Simplify.simplExpr (compiler/simplCore/Simplify.hs:(1018,1)-(1026,45))
   Simplify.simplLam (compiler/simplCore/Simplify.hs:(1501,1)-(1538,37))
   Simplify.simplExprF1 (compiler/simplCore/Simplify.hs:(1064,1)-(1140,52))
   Simplify.simplExprF (compiler/simplCore/Simplify.hs:(1049,1)-(1059,26))
   Simplify.simplLazyBind (compiler/simplCore/Simplify.hs:(381,1)-(432,68))
   Simplify.simplBind (compiler/simplCore/Simplify.hs:(362,1)-(368,58))
   Simplify.simplRecOrTopPair.trace_bind
 (compiler/simplCore/Simplify.hs:(330,5)-(334,56))
   Simplify.simplRecOrTopPair
 (compiler/simplCore/Simplify.hs:(321,1)-(334,56))
   Simplify.simplTopBinds.simpl_bind
 (compiler/simplCore/Simplify.hs:(268,5)-(272,65))
   Simplify.simplTopBinds.simpl_binds
 (compiler/simplCore/Simplify.hs:(264,5)-(266,64))
   Simplify.simplTopBinds (compiler/simplCore/Simplify.hs:(248,1)-(272,65))
   SimplCore.SimplTopBinds (compiler/simplCore/SimplCore.hs:758:29-64)
   SimplMonad.initSmpl (compiler/simplCore/SimplMonad.hs:(72,1)-(78,36))
   SimplCore.simplifyPgmIO.do_iteration
 (compiler/simplCore/SimplCore.hs:(691,5)-(798,48))
   SimplCore.simplifyPgmIO
 (compiler/simplCore/SimplCore.hs:(658,1)-(800,47))
   IOEnv.liftIO (compiler/utils/IOEnv.hs:188:5-33)
   CoreMonad.liftIO (compiler/simplCore/CoreMonad.hs:615:5-37)
   CoreMonad.liftIOWithCount (compiler/simplCore/CoreMonad.hs:619:1-87)
   SimplCore.simplifyPgm (compiler/simplCore/SimplCore.hs:(644,1)-(649,48))
   SimplCore.Simplify (compiler/simplCore/SimplCore.hs:456:40-55)
   SimplCore.doCorePass (compiler/simplCore/SimplCore.hs:(455,1)-(500,50))
   SimplCore.runCorePasses.do_pass
 (compiler/simplCore/SimplCore.hs:(442,5)-(450,28))
   SimplCore.runCorePasses
 (compiler/simplCore/SimplCore.hs:(439,1)-(452,24))
   IOEnv.thenM.\ (compiler/utils/IOEnv.hs:(83,37)-(84,60))
   IOEnv.thenM (compiler/utils/IOEnv.hs:(83,1)-(84,61))
   CoreMonad.>>=.\ (compiler/simplCore/CoreMonad.hs:(524,30)-(528,38))
   CoreMonad.>>= (compiler/simplCore/CoreMonad.hs:(524,5)-(528,38))
   IOEnv.runIOEnv (compiler/utils/IOEnv.hs:127:1-30)
   CoreMonad.runCoreM (compiler/simplCore/CoreMonad.hs:(565,1)-(581,63))
   SimplCore.core2core (compiler/simplCore/SimplCore.hs:(75,1)-(99,54))
   HscTypes.liftIO.\ (compiler/main/HscTypes.hs:245:31-55)
   HscTypes.liftIO (compiler/main/HscTypes.hs:245:5-55)
   HscMain.Core2Core (compiler/main/HscMain.hs:1173:7-42)
   HscMain.hscSimplify' (compiler/main/HscMain.hs:(1170,1)-(1173,42))
   HscMain.finish (compiler/main/HscMain.hs:(702,1)-(740,70))
   HscTypes.>>=.\ (compiler/main/HscTypes.hs:(240,33)-(242,56))
   HscTypes.>>= (compiler/main/HscTypes.hs:(240,5)-(242,56))
   HscTypes.runHsc (compiler/main/HscTypes.hs:(251,1)-(254,12))
   HscMain.hscIncrementalCompile
 (compiler/main/HscMain.hs:(644,1)-(690,60))
   DriverPipeline.compileOne'
 (compiler/main/DriverPipeline.hs:(134,1)-(289,55))
   GhcMake.upsweep_mod.compile_it_discard_iface
 (compiler/main/GhcMake.hs:(1436,13)-(1438,61))
   GhcMake.upsweep_mod (compiler/main/GhcMake.hs:(1376,1)-(1532,49))
   GhcMonad.liftIO (compiler/main/GhcMonad.hs:110:3-30)
   GhcMake.upsweep.upsweep' (compiler/main/GhcMake.hs:(1245,3)-(1344,91))
   GhcMake.upsweep (compiler/main/GhcMake.hs:(1237,1)-(1344,91))
   GhcMake.load'.upsweep_fn (compiler/main/GhcMake.hs:(389,9)-(390,41))
   GhcMake.load' (compiler/main/GhcMake.hs:(242,1)-(490,38))
   GhcMake.load (compiler/main/GhcMake.hs:(234,1)-(236,44))
   Main.doMake (ghc/Main.hs:(695,1)-(720,13))
   GhcMonad.gcatch.\ (compiler/main/GhcMonad.hs:117:19-63)
   GhcMonad.gcatch (compiler/main/GhcMonad.hs:(116,3)-(117,63))
   ErrUtils.prettyPrintGhcErrors
 (compiler/main/ErrUtils.hs:(657,1)-(666,44))
   Main.main' (ghc/Main.hs:(154,1)-(258,33))
   GhcMonad.gmask.\.\.g_restore.\ (compiler/main/GhcMonad.hs:121:65-80)
   GhcMonad.gmask.\.\.g_restore (compiler/main/GhcMonad.hs:121:33-80)
   GhcMonad.gmask.\.\ (compiler/main/GhcMonad.hs:(120,30)-(123,53))
   Exception.gmask.\ (compiler/utils/Exception.hs:64:27-29)
   Exception.gmask (compiler/utils/Exception.hs:64:3-30)
   GhcMonad.gmask.\ (compiler/main/GhcMonad.hs:(119,19)-(123,53))
   GhcMonad.gmask (compiler/main/GhcMonad.hs:(118,3)-(123,53))
   Exception.gfinally (compiler/utils/Exception.hs:(56,3)-(60,14))
   GhcMonad.>>=.\ (compiler/main/GhcMonad.hs:107:26-57)
   GhcMonad.>>= (compiler/main/GhcMonad.hs:107:3-57)
   Panic.withSignalHandlers (compiler/utils/Panic.hs:(240,1)-(298,37))
   GHC.runGhc (compiler/main/GHC.hs:(440,1)-(445,26))
   Exception.gcatch (compiler/utils/Exception.hs:63:3-37)
   Exception.ghandle (compiler/utils/Exception.hs:73:1-21)
   GHC.defaultErrorHandler (compiler/main/GHC.hs:(380,1)-(412,7))
   Main.main (ghc/Main.hs:(90,1)-(150,64))
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13959#comment:3
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler