fixup! Do not emit unnecessary source mappings

Author: vouillon

compiler/lib/js_output.ml

@@ -497,6 +497,9 @@ struct
     in
     traverse l e
 
+  (* The debuggers do not stop on some statements, like function
+     declarations. So there is no point in outputting some debug
+     information there. *)
   let stop_on_statement st =
     match st with
     | Block _