Re: [GHC] #13142: Core simplifier crashes while building stack.

21 Jan 2017

      #13142: Core simplifier crashes while building stack.
-------------------------------------+-------------------------------------
        Reporter:  jeiea             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * os:  Windows => Unknown/Multiple

Comment:

 A couple of clarifications:

 1. This isn't OS-specific - I can also reproduce it on Windows.
 2. This has nothing to do with `stack` in particular, but rather one of
 its dependencies, `store`. (Aside: `store` is gaining a reputation for
 causing GHC bugs. See also #13059.)
 3. This relies on building `store` with a debugging compiler (In fact, why
 is `stack` using a debugging compiler in the first place? Weird.)

 I tried to trim `store` down into as small of an example as I possibly
 could. Here's what I came up with:

 {{{#!hs
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DefaultSignatures #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE EmptyCase #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UnboxedTuples #-}
 {-# LANGUAGE UndecidableInstances #-}
 module StoreBug () where

 import Data.Foldable (foldl')
 import Data.Proxy
 import Data.Word
 import Foreign.Storable (Storable, sizeOf)
 import GHC.Generics
 import GHC.Types (Int(..))
 import GHC.TypeLits

 newtype Type = VarT Name
   deriving Generic

 data Name = Name OccName NameFlavour
   deriving Generic

 data NameFlavour
    = NameS
    | NameQ ModName
    | NameU !Int
    | NameL !Int
    | NameG PkgName ModName
    deriving Generic

 newtype ModName = ModName String
   deriving Generic

 newtype PkgName = PkgName String
   deriving Generic

 newtype OccName = OccName String
   deriving Generic

 instance Store Type
 instance Store Name
 instance Store NameFlavour
 instance Store ModName
 instance Store OccName
 instance Store PkgName

 instance Store Char where
   {-# INLINE size #-}
   size = sizeStorableTy "Foreign.Storable.Storable GHC.Types.Char"

 instance Store Int where
   {-# INLINE size #-}
   size = undefined

 instance Store a => Store [a] where
     size = sizeSequence
     {-# INLINE size #-}

 sizeSequence :: forall a. Store a => Size [a]
 sizeSequence = VarSize $ \t ->
     case size :: Size a of
         ConstSize n -> n * (length t) + sizeOf (undefined :: Int)
         VarSize f -> foldl' (\acc x -> acc + f x) (sizeOf (undefined ::
 Int)) t
 {-# INLINE sizeSequence #-}

 class Store a where
     size :: Size a

     default size :: (Generic a, GStoreSize (Rep a)) => Size a
     size = genericSize
     {-# INLINE size #-}

 data Size a
     = VarSize (a -> Int)
     | ConstSize !Int

 getSizeWith :: Size a -> a -> Int
 getSizeWith (VarSize f) x = f x
 getSizeWith (ConstSize n) _ = n
 {-# INLINE getSizeWith #-}

 contramapSize :: (a -> b) -> Size b -> Size a
 contramapSize f (VarSize g) = VarSize (g . f)
 contramapSize _ (ConstSize n) = ConstSize n
 {-# INLINE contramapSize #-}

 combineSizeWith :: forall a b c. (c -> a) -> (c -> b) -> Size a -> Size b
 -> Size c
 combineSizeWith toA toB sizeA sizeB =
     case (sizeA, sizeB) of
         (VarSize f, VarSize g) -> VarSize (\x -> f (toA x) + g (toB x))
         (VarSize f, ConstSize m) -> VarSize (\x -> f (toA x) + m)
         (ConstSize n, VarSize g) -> VarSize (\x -> n + g (toB x))
         (ConstSize n, ConstSize m) -> ConstSize (n + m)
 {-# INLINE combineSizeWith #-}

 sizeStorableTy :: forall a. Storable a => String -> Size a
 sizeStorableTy ty = ConstSize (sizeOf (error msg :: a))
   where
     msg = "In Data.Store.storableSize: " ++ ty ++ "'s sizeOf evaluated its
 argument."
 {-# INLINE sizeStorableTy #-}

 genericSize :: (Generic a, GStoreSize (Rep a)) => Size a
 genericSize = contramapSize from gsize
 {-# INLINE genericSize #-}

 type family SumArity (a :: * -> *) :: Nat where
     SumArity (C1 c a) = 1
     SumArity (x :+: y) = SumArity x + SumArity y

 class GStoreSize f where gsize :: Size (f a)

 instance GStoreSize f => GStoreSize (M1 i c f) where
     gsize = contramapSize unM1 gsize
     {-# INLINE gsize #-}

 instance Store a => GStoreSize (K1 i a) where
     gsize = contramapSize unK1 size
     {-# INLINE gsize #-}

 instance GStoreSize U1 where
     gsize = ConstSize 0
     {-# INLINE gsize #-}

 instance GStoreSize V1 where
     gsize = ConstSize 0
     {-# INLINE gsize #-}

 instance (GStoreSize a, GStoreSize b) => GStoreSize (a :*: b) where
     gsize = combineSizeWith (\(x :*: _) -> x) (\(_ :*: y) -> y) gsize
 gsize
     {-# INLINE gsize #-}

 instance (SumArity (a :+: b) <= 255, GStoreSizeSum 0 (a :+: b))
          => GStoreSize (a :+: b) where
     gsize = VarSize $ \x -> sizeOf (undefined :: Word8) + gsizeSum x
 (Proxy :: Proxy 0)
     {-# INLINE gsize #-}

 class KnownNat n => GStoreSizeSum (n :: Nat) (f :: * -> *) where gsizeSum
 :: f a -> Proxy n -> Int

 instance (GStoreSizeSum n a, GStoreSizeSum (n + SumArity a) b, KnownNat n)
          => GStoreSizeSum n (a :+: b) where
     gsizeSum (L1 l) _ = gsizeSum l (Proxy :: Proxy n)
     gsizeSum (R1 r) _ = gsizeSum r (Proxy :: Proxy (n + SumArity a))
     {-# INLINE gsizeSum #-}

 instance (GStoreSize a, KnownNat n) => GStoreSizeSum n (C1 c a) where
     gsizeSum x _ = getSizeWith gsize x
     {-# INLINE gsizeSum #-}
 }}}

 And here's the panic I get when I compile it with a debug-enabled GHC
 HEAD:

 {{{
 $ ~/Software/ghc5/inplace/bin/ghc-stage2 -fforce-recomp -O2 StoreBug.hs
 [1 of 1] Compiling StoreBug         ( StoreBug.hs, StoreBug.o )
 WARNING: file compiler/simplCore/SimplCore.hs, line 666
   Simplifier bailing out after 4 iterations [3866, 755, 220, 8]
     Size = {terms: 1,490, types: 7,176, coercions: 4,808}
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.1.20170121 for x86_64-unknown-linux):
         ASSERT failed!
   in_scope InScope {wild_00 wild_X25 g1_a33l g2_a33m $cfrom_a47d
                     $cto_a47F $cfrom_a48a $cto_a48C $cfrom_a496 $cto_a4bk
 $cfrom_a4dA
                     $cto_a4e2 $cfrom_a4ew $cto_a4fb $cfrom_a4fS $cto_a4gk
                     $cp1GStoreSizeSum_a4gV $cgsizeSum_a4gX
 $cp1GStoreSizeSum_a4hh
                     $cgsizeSum_a4hj $cgsize_a4hV $cgsize_a4ix $csize_a4iU
 $csize_a4j2
                     $csize_a4jb $csize_a4jj $csize_a4jw $csize_a4jJ
 $csize_a4jW
                     $csize_a4k9 $csize_a4km $cgsize_a4kD $cgsize_a4kY
 $cgsize_a4l6
                     $cgsize_a4li $dGStoreSize_a4qQ $dGStoreSize_a4qW
 $dGStoreSize_a4r2
                     $dGStoreSize_a4r8 $dGStoreSize_a4BJ $dGStoreSize_a4BS
 ww2_a5CX
                     sizeSequence genericSize $tc'ModName $tcModName
 $tc'PkgName
                     $tcPkgName $tc'NameS $tc'NameQ $tc'NameU $tc'NameL
 $tc'NameG
                     $tcNameFlavour $tc'OccName $tcOccName $tc'Name $tcName
 $tc'VarT
                     $tcType $tc'VarSize $tc'ConstSize $tcSize
 $tcGStoreSize
                     $tc'C:GStoreSize $fGStoreSize:*: $fGStoreSizeV1
 $fGStoreSizeU1
                     $fGStoreSizeM1 $tcStore $dmsize $tc'C:Store
 $fGStoreSizeK1
                     $fStore[] $fStoreInt $fStoreChar $fStorePkgName
 $fStoreOccName
                     $fStoreModName $fStoreNameFlavour $fStoreName
 $fStoreType
                     $tcGStoreSizeSum $tc'C:GStoreSizeSum
 $fGStoreSizeSumnM1
                     $fGStoreSizeSumn:+: $fGStoreSize:+: $fGenericModName
                     $fGenericPkgName $fGenericNameFlavour $fGenericOccName
                     $fGenericName $fGenericType $trModule $cto_s4Pr
 $cfrom_s4Ps
                     $cfrom_s4Pv $cto_s4Pw $cfrom_s4Px $cfrom_s4PF
 $cto_s4PG $cfrom_s4PH
                     $cto_s4PI $cfrom_s4PJ $trModule_s50k $trModule_s50l
 $trModule_s50m
                     $trModule_s50n $tc'ModName_s50o $tc'ModName_s50p
 $tcModName_s50q
                     $tcModName_s50r $tc'PkgName_s50s $tc'PkgName_s50t
 $tcPkgName_s50u
                     $tcPkgName_s50v $tc'NameG_s50w $tc'NameG_s50x
 $tc'NameL_s50y
                     $tc'NameL_s50z $tc'NameU_s50A $tc'NameU_s50B
 $tc'NameQ_s50C
                     $tc'NameQ_s50D $tc'NameS_s50E $tc'NameS_s50F
 $tcNameFlavour_s50G
                     $tcNameFlavour_s50H $tc'OccName_s50I $tc'OccName_s50J
                     $tcOccName_s50K $tcOccName_s50L $tc'Name_s50M
 $tc'Name_s50N
                     $tcName_s50O $tcName_s50P $tc'VarT_s50Q $tc'VarT_s50R
 $tcType_s50S
                     $tcType_s50T $tc'ConstSize_s50U $tc'ConstSize_s50V
 $tc'VarSize_s50W
                     $tc'VarSize_s50X $tcSize_s50Y $tcSize_s50Z
 $tc'C:GStoreSize_s510
                     $tc'C:GStoreSize_s511 $tcGStoreSize_s512
 $tcGStoreSize_s513
                     $tc'C:Store_s514 $tc'C:Store_s515 $tcStore_s516
 $tcStore_s517
                     $tc'C:GStoreSizeSum_s518 $tc'C:GStoreSizeSum_s519
                     $tcGStoreSizeSum_s51a $tcGStoreSizeSum_s51b
 $sgenericSize_s59c
                     $sgenericSize_s59f $sgenericSize_s59i
 $sgenericSize_s59l
                     $sgenericSize_s59o $sgenericSize_s59r $sgsize_s59B
 $sgsize_s59D
                     $sgsize_s59F $sgsize_s59H $sgsize_s59J $sgsize_s59L
 lvl_s5bw
                     lvl_s5bx $csize_s5i3 $dGStoreSize_s5jy
 $dGStoreSize_s5jM
                     $dGStoreSize_s5k0 $dGStoreSize_s5kc $dGStoreSize_s5lQ
                     $dGStoreSize_s5od $dGStoreSize_s5rC g_s5tx g_s5tA
 g_s5tD
                     $dGStoreSize_s5u4 g_s5u5 $dGStoreSize_s5uv
 $dGStoreSize_s5uZ
                     $sgenericSize_s5v0 $csize_s5v2 g_s5vy
 $sgenericSize_s5vA
                     $csize_s5vF $w$j_s5Wr a_s5Ws ww_s5Ww ww_s5Wx $wg_s5WC
                     $w$dGStoreSize_s5WI $wg_s5WT lvl_s65L lvl_s65M
 lvl_s65N lvl_s65O
                     lvl_s65P lvl_s65Q lvl_s65R lvl_s65S lvl_s65T lvl_s65U
 lvl_s65W
                     lvl_s65X lvl_s65Y lvl_s65Z lvl_s660 lvl_s661 lvl_s662
 lvl_s663
                     lvl_s664 lvl_s665 lvl_s666 lvl_s667 lvl_s66c lvl_s66d
 lvl_s66e
                     lvl_s66f lvl_s66g lvl_s66h lvl_s66i lvl_s66j lvl_s66k
 lvl_s66l
                     lvl_s66m lvl_s66n lvl_s66s lvl_s66t lvl_s66u lvl_s66v
 lvl_s66w
                     lvl_s66x lvl_s66y lvl_s66z lvl_s66A lvl_s66B lvl_s66C
 lvl_s66D
                     lvl_s66I lvl_s66J lvl_s66K lvl_s66L $s$w$j_s69S
 $s$w$j_s69T
                     $s$w$j_s69U}
   tenv []
   tenvFVs []
   cenv [s69R :-> sg_s69R]
   cenvFVs [s69R :-> sg_s69R]
   tys [R]
   cos []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1166:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1215:22 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2078:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2111:17 in
 ghc:TyCoRep
         substTy, called at compiler/types/OptCoercion.hs:345:12 in
 ghc:OptCoercion
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1166:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1170:37 in
 ghc:Outputable
         pprPanic, called at compiler/utils/Outputable.hs:1213:5 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2078:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2111:17 in
 ghc:TyCoRep
         substTy, called at compiler/types/OptCoercion.hs:345:12 in
 ghc:OptCoercion
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13142#comment:2
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