src/Pure/Tools/codegen_serializer.ML

     | ((b, p as _ :: _ :: _), []) => mk_mixfix (if b then NOBR else BR, p)
     | _ => Scan.!! (the_default ("malformed mixfix annotation: " ^ quote s) o snd) Scan.fail ()
   end;
 
 fun parse_args f args =
-  case f args
-   of (x, []) => x
-    | (_, _) => error "bad serializer arguments";
+  case Scan.read Args.stopper f args
+   of SOME x => x
+    | NONE => error "bad serializer arguments";
 
 
 (* list and string serializer *)
 
 fun implode_list c_nil c_cons e =