Haskell refactoring technique: make it compile by making it undefined (blog.patch-tag.com)

Wherein a naughty house elf makes his package compile after discovering that an ill-considered dependency makes it unusable on windows.

Hey, I've been looking for that, without even realizing it. My biggest pet peeve with Haskell up to this point is that refactoring was painful again (after so many years working with Perl), because you had to propagate all the type changes immediately to get it to compile. Even though I agree that it's great that Haskell detects these problems and I agree I need to fix them "eventually" (before release), it was making refactoring heavyweight enough to bother me, even on relatively small codebases. (Besides, sometimes refactorings turn out to be wrong, and I need to discover that before fully performing it.)

That's still not the whole story, I think, but it's a tool going in the toolbox.