> This does not seem to me to increase the expressivity of the language, whereas Haskell's type system does Some of us don't view that as a wanted feature. I

> This does not seem to me to increase the expressivity of the language, whereas Haskell's type system does Some of us don't view that as a wanted feature. I wrote more optional/modular/pluggable type systems before. See: https://news.ycombinator.com/item?id=6196466 https://news.ycombinator.com/item?id=6196466 > polymorphic "return", or punts and doesn't do it Haskell's type inferencer is doing a "search" for a type that fits and slotting that in there as an implicit argument. An error occurs if two match and you need to provide a type signature to differentiate. You could do precisely the same thing using first-class type objects, which Clojure has. Haskell has finally added them too, but required a compiler change. (See: Typeable). That's how type classes work in general: A dictionary of methods has to be threaded through, unless the compiler can prove that the dictionary is a constant. Clojure does the same thing by embedding a pointer to that data in the first-class function object. Let's assume I have a typed module. I could trivially query that module, since the type descriptions are data. That's what the Haskell compiler is doing, but with first-class types, I can do it myself. There is no reason that a user-level macro can't add enough inference to perform polymorphic returns. But even if I could do this, I wouldn't want to. At most, I'd want an "infer-monad" form where I can explicitly say that I'm using my types to convey intent and am willing to pay the cost of coupling my program to a particular type system.