[GHC] #12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor and -O

[GHC]

#12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor
and -O
-------------------------------------+-------------------------------------
           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:
-------------------------------------+-------------------------------------
 ghc version: 41ec722d71 with assertion that fails in
 https://ghc.haskell.org/trac/ghc/ticket/12926 commented out


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

 module Numeric.Polynomial.Log () where

 class AdditiveGroup v where
   (^+^) :: v -> v -> v
   negateV :: v -> v
   (^-^) :: v -> v -> v
   v ^-^ v' = v ^+^ negateV v'

 class AdditiveGroup v => VectorSpace v where
   type Scalar v :: *
   (*^) :: Scalar v -> v -> v


 data Poly1 a = Poly1 a a

 data IntOfLog poly a = IntOfLog !a !(poly a)

 instance Num a => AdditiveGroup (Poly1 a) where
     {-# INLINE (^+^) #-}
     {-# INLINE negateV #-}
     Poly1 a b ^+^ Poly1 a' b' = Poly1 (a + a') (b + b')
     negateV (Poly1 a b) = Poly1 (negate a) (negate b)


 instance (AdditiveGroup (poly a), Num a) => AdditiveGroup (IntOfLog poly
 a) where
     {-# INLINE (^+^) #-}
     {-# INLINE negateV #-}
     IntOfLog k p ^+^ IntOfLog k' p' = IntOfLog (k + k') (p ^+^ p')
     negateV (IntOfLog k p) = IntOfLog (negate k) (negateV p)
     {-# SPECIALISE instance Num a => AdditiveGroup (IntOfLog Poly1 a) #-}

 instance (VectorSpace (poly a), Scalar (poly a) ~ a, Num a) => VectorSpace
 (IntOfLog poly a) where
     type Scalar (IntOfLog poly a) = a
     s *^ IntOfLog k p = IntOfLog (s * k) (s *^ p)

 }}}


 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.1.20161206 for x86_64-unknown-linux):
         ASSERT failed!
   $dAdditiveGroup_aIU
   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/stgSyn/CoreToStg.hs:967:78 in
 ghc:CoreToStg
   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/stgSyn/CoreToStg.hs:967:78 in
 ghc:CoreToStg

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

 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12944>
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