src/Pure/General/path.scala

     Long_Name.explode(name).exists(a => reserved_windows.contains(Word.uppercase(a)))
 
 
   /* case-insensitive names */
 
-  def check_case_insensitive(paths: List[Path])
+  def check_case_insensitive(paths: List[Path]): Unit =
   {
     val table =
       (Multi_Map.empty[String, String] /: paths)({ case (tab, path) =>
         val name = path.expand.implode
         tab.insert(Word.lowercase(name), name)