[GHC] #12926: ghc master (8.1.20161202) panics with assertion failure with devel2 flavor and -O2

[GHC]

#12926: ghc master (8.1.20161202) panics with assertion failure with devel2 flavor
and -O2
-------------------------------------+-------------------------------------
           Reporter:  pacak          |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           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:
-------------------------------------+-------------------------------------
 Following code if compiled with -O2 (but not -O1) causes assertion
 failure. Depends only on vector.


 {{{#!hs
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE MultiParamTypeClasses #-}

 module A where

 import GHC.Base
 import qualified Data.Vector.Unboxed.Base
 import qualified Data.Vector.Generic.Base
 import Data.Vector.Generic.Mutable
 import qualified Data.Vector.Generic.Mutable.Base
 import Data.Vector.Generic (fromList)

 data A = A Int Int Int

 instance Data.Vector.Unboxed.Base.Unbox A

 newtype instance Data.Vector.Unboxed.Base.MVector s_a4iX A
   = MV_A (Data.Vector.Unboxed.Base.MVector s_a4iX (Int, Int, Int))

 instance MVector Data.Vector.Unboxed.Base.MVector A where
   basicLength (MV_A v) = basicLength v
   basicUnsafeSlice idx len (MV_A v) = MV_A (basicUnsafeSlice idx len v)
   basicUnsafeNew len = (MV_A `liftM` (basicUnsafeNew len))
   basicUnsafeWrite (MV_A v) idx val_a4iW = basicUnsafeWrite v idx ( (\ (A
 a_a4iT b_a4iU c_a4iV) -> (a_a4iT, b_a4iU, c_a4iV)) val_a4iW)

 newtype instance Data.Vector.Unboxed.Base.Vector A = V_A
 (Data.Vector.Unboxed.Base.Vector (Int, Int, Int))

 instance Data.Vector.Generic.Base.Vector Data.Vector.Unboxed.Base.Vector A
 where

 mkA :: Data.Vector.Unboxed.Base.Vector A
 mkA = fromList []
 }}}



 {{{

 ghc: panic! (the 'impossible' happened)
 [7/1644]
   (GHC version 8.1.20161202 for x86_64-unknown-linux):
         ASSERT failed!
   in_scope InScope {wild_00 eta_X1T $cbasicUnsafeFreeze_a6sr
                     $cbasicUnsafeThaw_a6st $cbasicLength_a6sv
 $cbasicUnsafeSlice_a6sx
                     $cbasicUnsafeIndexM_a6sz $cbasicUnsafeCopy_a6sF
 $celemseq_a6t3
                     $cbasicLength_a6tm $cbasicUnsafeSlice_a6ty
 $cbasicOverlaps_a6tL
                     $cbasicUnsafeNew_a6tN $cbasicInitialize_a6uj
                     $cbasicUnsafeReplicate_a6up $cbasicUnsafeRead_a6uJ
                     $cbasicUnsafeWrite_a6uL $cbasicClear_a6vg
 $cbasicSet_a6vE
                     $cbasicUnsafeCopy_a6w2 $cbasicUnsafeMove_a6wr
                     $cbasicUnsafeGrow_a6wQ wild_a7QO dt_a7QQ ds1_a7QR
 ds2_a7QS ds3_a7QT
                     wild_a80U x_a819 xs1_a81a ds4_a84V z_a84W s7_a84X
 ds5_a851
                     wild5_a85V v3_a85X i_a85Y wild7_a866 x_a868 y_a86k
 wild9_a86m $tcA
                     $trModule $tc'A $fVectorVectorA $fUnboxA
 $fMVectorMVectorA mkA
                     $cbasicUnsafeSlice_s7QF $trModule_s7Su $trModule_s7Sv
 $tc'A_s7Sw
                     $s$dmbasicUnsafeGrow_s7Vp $s$dmbasicUnsafeMove_s7Vw
                     $s$dmbasicUnsafeReplicate_s7VB $s$dmbasicSet_s7VG
                     $s$dmbasicUnsafeCopy_s7VN $s$dmbasicUnsafeCopy_s7VW
 $sunstream_s886
                     $s$fMVectorMVector(,,)_$cbasicUnsafeNew_s896
                     $s$fMVectorMVector(,,)_$cbasicUnsafeWrite_s89h
                     $s$fMVectorMVector(,,)_$cbasicUnsafeSlice_s89k
                     $s$fMVectorMVector(,,)_$cbasicLength_s89l
 $sfromList_s89m
                     $snew_s89n $s$dmelemseq_s89o $s$dmbasicClear_s89p
 lvl_s89Y $j_sa8p
                     lvl_sbhM lvl_sbhN lvl_sbhO lvl_sbhP lvl_sbhQ lvl_sbhR
 lvl_sbhT
                     lvl_sbhU lvl_sbhV lvl_sbhW lvl_sbi1 lvl_sbi2 lvl_sbi4
 lvl_sbi5
                     lvl_sbi6 lvl_sbi7 foldlM_loop_sbns foldlM_loop_sbnL
 lvl_sbo2
                     $sfoldlM_loop_sbHS $s$j_sbI5 $sfoldlM_loop_sbIa
 $sfoldlM_loop_sbIx}
   tenv []
   tenvFVs []
   cenv [sbHY :-> sg_sbHY]
   cenvFVs [sbHY :-> sg_sbHY]
   tys [PrimState (ST RealWorld)]
   cos []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1114:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1163:22 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2023:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2056:17 in
 ghc:TyCoRep
         substTy, called at compiler/types/Coercion.hs:1457:33 in
 ghc:Coercion
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1114:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1118:37 in
 ghc:Outputable
         pprPanic, called at compiler/utils/Outputable.hs:1161:5 in
 ghc:Outputable
         assertPprPanic, called at compiler/types/TyCoRep.hs:2023:56 in
 ghc:TyCoRep
         checkValidSubst, called at compiler/types/TyCoRep.hs:2056:17 in
 ghc:TyCoRep
         substTy, called at compiler/types/Coercion.hs:1457:33 in
 ghc:Coercion

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

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12926>
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