Add explicit ~xt parameter to Xt.call to make it polymorphic

Author: polytypic

src/kcas/kcas.ml

@@ -743,7 +743,7 @@ module Xt = struct
 
   type 'a tx = { tx : 'x. xt:'x t -> 'a } [@@unboxed]
 
-  let call { tx } = tx [@@inline]
+  let call ~xt { tx } = tx ~xt [@@inline]
 
   let rec add_awaiters awaiter casn = function
     | NIL as cont -> cont

src/kcas/kcas.mli

@@ -345,7 +345,7 @@ module Xt : sig
       explicit transaction log.  The universal quantification helps to ensure
       that the transaction log cannot accidentally escape. *)
 
-  val call : 'a tx -> xt:'x t -> 'a
+  val call : xt:'x t -> 'a tx -> 'a
   (** [call ~xt tx] is equivalent to [tx.Xt.tx ~xt]. *)
 
   val commit : ?backoff:Backoff.t -> ?mode:Mode.t -> 'a tx -> 'a

test/kcas/test.ml

@@ -555,6 +555,15 @@ let test_rollback () =
 
 (* *)
 
+let test_call () =
+  let never = Xt.{ tx = (fun ~xt:_ -> Retry.later ()) } in
+  let result =
+    Xt.commit { tx = Xt.first [ Xt.call never; (fun ~xt:_ -> 101) ] }
+  in
+  assert (result = 101)
+
+(* *)
+
 let test_mode () =
   assert (Loc.get_mode (Loc.make ~mode:Mode.lock_free 0) == Mode.lock_free);
   assert (
@@ -598,6 +607,7 @@ let () =
   test_periodic_validation ();
   test_explicit_validation ();
   test_rollback ();
+  test_call ();
   test_mode ();
   test_xt ();
   Printf.printf "Test suite OK!\n%!"