Hello,

I am blocked by this case not working (I reported on Mantis ...
https://caml.inria.fr/mantis/view.php?id=7636)

Any hint on how to make it works, apart fomr Obj.magic ?

I can not change the types, they come from a functor.

====================================================
type ('a, 'b) elt = 'a

type 'a iter = { f : 'b.('a, 'b) elt -> unit }

let promote f : 'a -> unit =
  let f : 'b.('a, 'b) elt -> unit = fun x -> f x in
    { f }
====================================================

Cheers,
Christophe