I don't think so: If you want the equivalent of Haskell type classes in OCaml then you have to either use a functors or some sort of class IIRC. I'm sure Oleg will have done something though.

I believe they're experimental in Coq.

yup, you're right, you got to use functors or go home.

Yeup, some folks did show the functors + modules \equiv type classes in some sense, for system F or a variant thereof. Theres also an oleg approach too I think.