I use Arch Linux, and I have the latest GHC installed using pacman, few modules (such as Prelude and some other basics) are installed using pacman too. Few days ago I decided to install Cabal, and I experienced a big problem: somehow modules installed by pacman were assumed invalid by Cabal. Therefore I decided to uncheck them in GHC and reinstall in Cabal (they were dependency for few my targets). Everything went fine, except now GHC can't find these packages now. Furthermore, now I can't even recompile XMonad which is pretty sad.
I have few ideas on how to fix this problem, and I need your help. Basically, I think it would be nice to remove all Haskell packages except GHC itself from pacman and move to Cabal. But this method would require me to recompile all modules on my own (which is pretty long) and I will have to figure out how to make XMonad work from Cabal.
I would very like to get any nice way to make GHC use local Cabal packages together with global ones, it would be perfect.