If you're talking about getting it to compile... If foo is giving you problems, write it as foo :: (the type you think it should have) foo = undefined

If you're talking about getting it to compile... If foo is giving you problems, write it as foo :: (the type you think it should have) foo = undefined If it compiles you at least know your type is right. Then, leaving the type annotation in place, replace undefined with a more useful expression. (Soon we will all be using Type Holes instead of this trick.) I like hdevtools for mark-errors-on-save. I don't know if there's an emacs hook for it, but it's emacs so probably. If you're talking about debugging after it compiles... I'm still working on that. I spent part of this past weekend digging into QuickCheck.