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panic caused in ghci by the following code involving monad transformers

I was attempting to learn to use monad transformers when I came across this bug, the following is the contents of StateAccum.hs

import Control.Monad
import Control.Monad.State
import Control.Monad.List

sumUp :: [Int] -> State Int [()]
sumUp = sequence . map (modify . (+))

type StateWithList = ListT (State Int)

sumUp' xs = do x <- xs
               lift (modify (+x))
               return (lift get)


sumThreeLists :: [Int] -> [Int] -> [Int] -> Int
sumThreeLists xs ys zs = execState (sumUp xs >> sumUp ys >> sumUp zs) 0

main = do print $ execState (sumUp [1,2,3]) 0
          print $ sumThreeLists [1..10] [1..10] [1..10]

This is a transcript of the ghci session that causes the panic:

% ghci StateAccum.hs
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6.1, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( StateAccum.hs, interpreted )
Ok, modules loaded: Main.
*Main> sumUp' [return 1, return 2]
ghc-6.6.1: panic! (the 'impossible' happened)
  (GHC version 6.6.1 for powerpc-apple-darwin):
        nameModule it{v a1es}

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

*Main>

I'm using the binary ghc package for Mac OS PPC provided on the ghc site. The output for uname -a on my machine is

Darwin Logan-Capaldos-Computer.local 8.9.0 Darwin Kernel Version 8.9.0: Thu Feb 22 20:54:07 PST 2007; root:xnu-792.17.14~1/RELEASE_PPC Power Macintosh powerpc

Running with ghci -v, this is the output

% ghci -v StateAccum.hs
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6.1, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Using package config file: /usr/local/lib/ghc-6.6.1/package.conf
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
Hsc static flags: -static
Loading package base ... linking ... done.
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
*** Chasing dependencies:
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
Upsweep completely successful.
*** Deleting temp files:
Deleting: 
*** Chasing dependencies:
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
compile: input file StateAccum.hs
*** Checking old interface for main:Main:
[1 of 1] Compiling Main             ( StateAccum.hs, interpreted )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
    Result size = 244
*** Simplify:
    Result size = 292
    Result size = 263
    Result size = 263
*** Tidy Core:
    Result size = 263
*** CorePrep:
    Result size = 331
*** ByteCodeGen:
*** Deleting temp files:
Deleting: 
Upsweep completely successful.
*** Deleting temp files:
Deleting: 
Ok, modules loaded: Main.
*Main> sumUp' [return 1, return 2]
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
ghc-6.6.1: panic! (the 'impossible' happened)
  (GHC version 6.6.1 for powerpc-apple-darwin):
        nameModule it{v a1es}

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

*Main>
Trac metadata
Trac field Value
Version 6.6.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
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