[yodsanklai]

OCaml is a somewhat old language with algebraic types (so including discriminated unions) yet exceptions were introduced precisely to avoid dealing with propagating errors as a values. I agree with your point, but would argue that even with sum types, propagating errors is tedious and there's a case for using exception.

I wonder if another reason why errors as value are making a come back is because of the asynchronous programming style which is becoming quite pervasive, and doesn't play well with exceptions.