For users of the systems that can't run the current haskell 8.x software (at present at least) I extracted what i believe is the bulk of the haskell 7.x world and have it as a portfile overlay.
It seems to work. pandoc installs and runs on 10.6.8, for example, as does HedgeWars. Perhaps it might be of use for someone -- maybe some motivated person might know how to use that working ghc @7.8.3 and build it forward to some current haskell compiler. clone this <https://github.com/kencu/mp-haskell7-world.git> and overlay it if you like. Best, Ken
