I agree that would be a good convention to move away from - I don't think it takes a GADT, though; a regular data type should be fine. For my part I think we s

I agree that would be a good convention to move away from - I don't think it takes a GADT, though; a regular data type should be fine. For my part I think we should also deprecate the Functor (and dependent) instances for Either and tuple - but I know there are some who strongly disagree and I don't care all that much.