clone_is_tricky.ml

(* Multi-shot continuations don't play nicely with linear resources.
 * This program illustrates that resuming an inner one-shot continuation 
 * within an outer multi-shot context causes a runtime error.
 *)
open Effect
open Effect.Deep

type _ Effect.t += Foo : unit Effect.t
type _ Effect.t += Bar : unit Effect.t

let _ =
  let run () =
    try_with perform Foo
      {
        effc =
          (fun (type a) (e : a Effect.t) ->
            match e with
            | Foo ->
                Some (fun (k : (a, _) continuation) -> continue k (perform Bar))
                (* This continuation is resumed twice *)
            | _ -> None);
      }
  in
  try_with run ()
    {
      effc =
        (fun (type a) (e : a Effect.t) ->
          match e with
          | Bar ->
              Some
                (fun (k : (a, _) continuation) ->
                  continue (Multicont.Deep.clone_continuation k) ();
                  continue k ())
          | _ -> None);
    }