(* TEST_BELOW
(* Blank lines added here to preserve locations. *)




*)

(* PR#6992, reported by Stephen Dolan *)

type (_, _) eq = Eq : ('a, 'a) eq
let cast : type a b . (a, b) eq -> a -> b = fun Eq x -> x

module Fix (F : sig type 'a f end) = struct
  type 'a fix = ('a, 'a F.f) eq
  let uniq (type a) (type b) (Eq : a fix) (Eq : b fix) : (a, b) eq = Eq
end

(* This would allow:
module FixId = Fix (struct type 'a f = 'a end)
 let bad : (int, string) eq = FixId.uniq Eq Eq
 let _ = Printf.printf "Oh dear: %s" (cast bad 42)
*)

(* TEST
 flags = " -w -a ";
 ocamlc_byte_exit_status = "2";
 setup-ocamlc.byte-build-env;
 ocamlc.byte;
 check-ocamlc.byte-output;
*)