> I wonder why you think so? The inferred types in a language like Haskell or OCaml are almost always exactly what the programmer would have written

I have no experience with ML-using languages but in Scala, which has inferior but still useful type inference, it is recommended to add explicit types to public functions/methods because otherwise, implementation details or errors might alter the signature.

Take for example:

    data Tree = Node Leaf Leaf | Leaf Integral
    makeEmptyTree x => Leaf x

I assume `Leaf` will be inferred as a type, while the programmer might have meant `Tree` to be the public API. (or vice-versa)