Ebuild should be updated and probably, portage stable version should be 1.0.7 now...
An untested ebuild may be found here: http://www.haskell.org/~gentoo/gentoo-haskell/portage/dev-util/darcs/
Hi Paulo, the url you have found is in fact the Gentoo Haskell overlay. I've put the darcs-1.0.8 ebuild in the tree, please sync and you'll be ready to emerge it. Thanks for reminding us. This closes the bug.