anchor.diff:    | VerifyUserList
     | VerifyFigureItOut
   
  -type files_for_module_name = smap<(option<string> * option<string>)>
  +type intf_and_impl = option<string> * option<string>
  +
  +type files_for_module_name = smap<intf_and_impl>
  +
  +let intf_and_impl_to_string ii =
  +  match ii with
  +  | None, None -> "<None>, <None>"
  +  | Some intf, None -> intf
  +  | None, Some impl -> impl
  +  | Some intf, Some impl -> intf ^ ", " ^ impl
  +
   
   let files_for_module_name_to_string (m:files_for_module_name) =
     BU.print_string "Printing the file system map {\n";
  
positive.code:     boolean telling whether the map was modified.
      
      If the open is an implicit open (as indicated by the flag),
      make sure that we don't overshadow any existing entry *)
  let enter_namespace
    (original_map: files_for_module_name)
    (working_map: files_for_module_name)
  
negative.code:     match sopt with
      | None -> "<None>"
      | Some s -> s in
    smap_iter m (fun k v -> BU.print2 "%s:%s\n" k (intf_and_impl_to_string v));
    BU.print_string "}\n"
  
  type color = | White | Gray | Black
  