[Haskell-cafe] datatype contexts

I agree with prior discussion on this list that adding contexts to datatype declarations seems to be more trouble than its worth, since these contexts just have to be added again to every function using the datatype. However, I have often wondered: why do function *have* to have these contexts? What would it affect in the language if we made the contexts be implicit, so that if we have data Datatype a = Context a => Datatype a then for function declarations f :: D a -> ... the context "Context a" is automatically asserted by the compiler? Cheers, Greg