[src][deadCommon] remove unnecessary ref

The `find` function was expecting a `ref` for the `occur` parameter
although it is always passed (updated) as argument to its inner `loop`
function.

Author: fantazio

src/deadArg.ml

@@ -43,7 +43,7 @@ let register_use label expr builddir loc last_loc count_tbl =
     else expr.exp_loc.Location.loc_start
   in
   if check_underscore label then
-    let loc = VdNode.find loc label (ref count) in
+    let loc = VdNode.find loc label count in
     if not (Hashtbl.mem met (last_loc, loc, label)) then (
       Hashtbl.add met (last_loc, loc, label) ();
       let opt_arg_use = {

src/deadCommon.ml

@@ -300,17 +300,17 @@ module VdNode = struct
           update loc1 (opts, Some loc2);
         end
 
-
+  (* find the loc of the function declaring the nth occurence of the label *)
   let find loc lab occur =
     let met = LocHash.create 8 in
     let rec loop loc lab occur =
       let count =
         if is_end loc then 0
         else List.filter (( = ) lab) (get_opts loc) |> List.length
       in
-      if is_end loc || LocHash.mem met loc || count >= !occur then loc
-      else begin
-        occur := !occur - count;
+      if is_end loc || LocHash.mem met loc || count >= occur then loc
+      else (
+        let occur = occur - count in
         LocHash.replace met loc ();
         match get_next loc with
         | Some next -> loop (func next) lab occur
@@ -320,7 +320,7 @@ module VdNode = struct
               ^ (string_of_int loc.Lexing.pos_lnum)
             in
               failwith (loc ^ ": optional argument `" ^ lab ^ "' unlinked")
-      end
+      )
     in loop (func loc) lab occur
 
   let eof () =