src/Pure/Isar/session.ML

 
 (* add_path *)
 
 fun add_path reset s =
   let val sess = ! session @ [s] in
-    (case gen_duplicates (op =) sess of
+    (case duplicates (op =) sess of
       [] => (session := sess; session_path := ((if reset then [] else ! session_path) @ [s]))
     | dups => error ("Duplicate session identifiers " ^ commas_quote dups ^ " in " ^ str_of sess))
   end;