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panic! ASSERT failed compiler/types/Type.hs line 1712

    • Closed Issue created by Ben Price @brprice

    The following code causes a panic when loaded into GHCi (more complicated code below makes GHC panic also)

    {-# LANGUAGE GADTs , PolyKinds #-}

module Bug where

data TyConT (a::k) = TyConT String

tyConTArr :: TyConT (->)
tyConTArr = TyConT "(->)"

data G2 c a where
  G2 :: TyConT a -> TyConT b -> G2 c (c a b)


getT2 :: TyConT (c :: k2 -> k1 -> k) -> TyConT (a :: k) -> Maybe (G2 c a)
getT2 (TyConT c) (TyConT a) = Nothing

s tf = case getT2 tyConTArr tf
       of Just (G2 _ _) -> Nothing
          _ -> Nothing

    ghci Bug.hs yields

    ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20150717 for x86_64-unknown-linux):
        ASSERT failed!
  file compiler/types/Type.hs line 1712
  a_ame -> b_amf
  k_anj

    And for GHC:

    {-# LANGUAGE GADTs , PolyKinds #-}

module Bug2 where

import Unsafe.Coerce

data TyConT (a::k) = TyConT String

eqTyConT :: TyConT a -> TyConT b -> Bool
eqTyConT (TyConT a) (TyConT b) = a == b



tyConTArr :: TyConT (->)
tyConTArr = TyConT "(->)"


data TypeRepT (a::k) where
  TRCon :: TyConT a -> TypeRepT a
  TRApp :: TypeRepT a -> TypeRepT b -> TypeRepT (a b)


data GetAppT a where
  GA :: TypeRepT a -> TypeRepT b -> GetAppT (a b)

getAppT :: TypeRepT a -> Maybe (GetAppT a)
getAppT (TRApp a b) = Just $ GA a b
getAppT _ = Nothing



eqTT :: TypeRepT (a::k1) -> TypeRepT (b::k2) -> Bool
eqTT (TRCon a) (TRCon b) = eqTyConT a b
eqTT (TRApp c a) (TRApp d b) = eqTT c d && eqTT a b
eqTT _ _ = False


data G2 c a where
  G2 :: TypeRepT a -> TypeRepT b -> G2 c (c a b)


getT2 :: TypeRepT (c :: k2 -> k1 -> k) -> TypeRepT (a :: k) -> Maybe (G2 c a)
getT2 c t = do GA t' b <- getAppT t
               GA c' a <- getAppT t'
               if eqTT c c'
                 then Just (unsafeCoerce $ G2 a b :: G2 c a)
                 else Nothing

tyRepTArr :: TypeRepT (->)
tyRepTArr = TRCon tyConTArr

s tf = case getT2 tyRepTArr tf
       of Just (G2 _ _) -> Nothing
          _ -> Nothing

    ghc Bug2.hs yields

    [1 of 1] Compiling Bug2             ( Bug2.hs, Bug2.o )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20150717 for x86_64-unknown-linux):
        ASSERT failed!
  file compiler/types/Type.hs line 1712
  a_amr -> b_ams
  k_a1c2

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

    This is a regression from 7.10.1 (fails at 1224bb55)

    uname -a: Linux cam-05-unx 3.5.0-54-generic #81~precise1-Ubuntu SMP Tue Jul 15 04:02:22 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

    using GCC 4.6.3

    gcc -v output:

    Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)

    ghc -v Bug2.hs:

    Glasgow Haskell Compiler, Version 7.11.20150717, stage 2 booted by GHC version 7.10.1
Using binary package database: /5playpen/t-bepric/ghc-build/inplace/lib/package.conf.d/package.cache
Using binary package database: /home/t-bepric/.ghc/x86_64-linux-7.11.20150717/package.conf.d/package.cache
wired-in package ghc-prim mapped to ghc-prim-0.4.0.0-inplace
wired-in package integer-gmp mapped to integer-gmp-1.0.0.0-inplace
wired-in package base mapped to base-4.8.2.0-inplace
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to template-haskell-2.10.0.0-inplace
wired-in package ghc mapped to ghc-7.11.20150717-inplace
wired-in package dph-seq not found.
wired-in package dph-par not found.
Hsc static flags: 
wired-in package ghc-prim mapped to ghc-prim-0.4.0.0-inplace
wired-in package integer-gmp mapped to integer-gmp-1.0.0.0-inplace
wired-in package base mapped to base-4.8.2.0-inplace
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to template-haskell-2.10.0.0-inplace
wired-in package ghc mapped to ghc-7.11.20150717-inplace
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Chasing dependencies:
Chasing modules from: *Bug2.hs
Stable obj: []
Stable BCO: []
Ready for upsweep
  [NONREC
      ModSummary {
         ms_hs_date = 2015-07-22 15:01:01 UTC
         ms_mod = Bug2,
         ms_textual_imps = [import (implicit) Prelude, import Unsafe.Coerce]
         ms_srcimps = []
      }]
*** Deleting temp files:
Deleting: 
compile: input file Bug2.hs
Created temporary directory: /tmp/ghc33699_0
*** Checking old interface for Bug2:
[1 of 1] Compiling Bug2             ( Bug2.hs, Bug2.o )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
Result size of Desugar (before optimization)
  = {terms: 206, types: 667, coercions: 24}
Result size of Desugar (after optimization)
  = {terms: 133, types: 421, coercions: 10}
*** Simplifier:
*** Deleting temp files:
Deleting: /tmp/ghc33699_0/ghc_1.s
Warning: deleting non-existent /tmp/ghc33699_0/ghc_1.s
*** Deleting temp dirs:
Deleting: /tmp/ghc33699_0
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20150717 for x86_64-unknown-linux):
        ASSERT failed!
  file compiler/types/Type.hs line 1712
  a_amr -> b_ams
  k_a1c2
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