ghc: panic installing darcs-beta

I've just tried to install darcs using cabal install darcs-beta, and somewhere in the middle I've got

[ 57 of 136] Compiling Darcs.Repository.Prefs ( src/Darcs/Repository/Prefs.lhs, dist/build/Darcs/Repository/Prefs.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.3 for i386-apple-darwin):
	cat_evals
    base:GHC.Arr.Array{d ras}
    [ww{v a305N} [lid], ww1{v a305O} [lid], ww2{v a305P} [lid]]
    [!, !, _, _]

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

cabal: Error: some packages failed to install:
darcs-beta-2.2.98.2 failed during the building phase. The exception was:
exit: ExitFailure 1

Trac metadata

Trac field	Value
Version	6.10.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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