ghc-package.eclass launches best_version with an unspecified name on line 66: cabalpackage="$(best_version cabal)" Should be: cabalpackage="$(best_version dev-haskell/cabal)" The previous version will break if someone introduces a virtual or another package of that name. (also - it breaks paludis)
Ok, fixed in the official haskell overlay. It'll make its way into portage cvs from there.
Finally in portage. Thanks for the report. ks