[istd] no need to re-implement List.fold_until

Summary: Use `Base.List.fold_until` instead.

Reviewed By: mbouaziz

Differential Revision: D7350958

fbshipit-source-id: a585e80

infer/src/IR/Errlog.ml

@@ -48,21 +48,20 @@ let make_trace_element lt_level lt_loc lt_description lt_node_tags =
 type loc_trace = loc_trace_elem list
 
 let compute_local_exception_line loc_trace =
-  let compute_local_exception_line state step =
-    match state with
-    | `Stop _ ->
-        state
-    | `Continue (last_known_step_at_level_zero_opt, line_opt) ->
-        let last_known_step_at_level_zero_opt' =
-          if Int.equal step.lt_level 0 then Some step else last_known_step_at_level_zero_opt
-        in
-        match last_known_step_at_level_zero_opt' with
-        | Some step_zero when contains_exception step ->
-            `Stop (last_known_step_at_level_zero_opt', Some step_zero.lt_loc.line)
-        | _ ->
-            `Continue (last_known_step_at_level_zero_opt', line_opt)
+  let open Base.Continue_or_stop in
+  let compute_local_exception_line (last_known_step_at_level_zero_opt, line_opt) step =
+    let last_known_step_at_level_zero_opt' =
+      if Int.equal step.lt_level 0 then Some step else last_known_step_at_level_zero_opt
+    in
+    match last_known_step_at_level_zero_opt' with
+    | Some step_zero when contains_exception step ->
+        Stop (Some step_zero.lt_loc.line)
+    | _ ->
+        Continue (last_known_step_at_level_zero_opt', line_opt)
   in
-  snd (List_.fold_until ~init:(`Continue (None, None)) ~f:compute_local_exception_line loc_trace)
+  match List.fold_until ~init:(None, None) ~f:compute_local_exception_line loc_trace with
+  | Finished (_, line_opt) | Stopped_early line_opt ->
+      line_opt
 
 
 type node_id_key = {node_id: int; node_key: Caml.Digest.t}

infer/src/istd/IStd.ml

@@ -10,14 +10,6 @@
 include Core
 
 module List_ = struct
-  let rec fold_until ~init ~f l =
-    match (l, init) with
-    | _, `Stop init' | [], `Continue init' ->
-        init'
-    | h :: t, `Continue _ ->
-        fold_until ~init:(f init h) ~f t
-
-
   let merge_dedup l1 l2 ~compare =
     let rec loop acc l1 l2 =
       match (l1, l2) with