type _ int_foo =
  | IF_constr : <foo:int; ..> int_foo

type _ int_bar =
  | IB_constr : <bar:int; ..> int_bar


let g (type t) (x:t) (e : t int_foo) (e' : t int_bar) =
  let IF_constr, IB_constr = e, e' in
  (x:<foo:int; bar:int>)