Edsko de Vries from Well-Typed has written the
nothunkslibrary which can give warnings if there are thunks in your code:
nothunks is great and I’m happy to have it, but IMHO its using the typeclass system to overcome a feature deficiency in GHC. If I could have my way, I would transform nothunk uses into Unlifted types. This way the my types just feel cleaner because Foo :: a isn’t masquerading as something (a thing that can be a thunk, and therefore includes \bot) as something that it isn’t (a thing that does not contain \bot as a value). So I would find this approach cleaner because I have type level witnesses instead of typeclass constraints that serve as witnesses. I guess I should help @jaror improving the ergonomics of Unlifted.