src/Pure/drule.ML

   val dest_term: thm -> cterm
   val cterm_rule: (thm -> thm) -> cterm -> cterm
   val cterm_add_frees: cterm -> cterm list -> cterm list
   val cterm_add_vars: cterm -> cterm list -> cterm list
   val dummy_thm: thm
+  val free_dummy_thm: thm
   val is_sort_constraint: term -> bool
   val sort_constraintI: thm
   val sort_constraint_eq: thm
   val with_subgoal: int -> (thm -> thm) -> thm -> thm
   val comp_no_flatten: thm * int -> int -> thm -> thm

 
 val cterm_add_frees = Thm.add_frees o mk_term;
 val cterm_add_vars = Thm.add_vars o mk_term;
 
 val dummy_thm = mk_term (certify Term.dummy_prop);
+val free_dummy_thm = Thm.tag_free_dummy dummy_thm;
 
 
 (* sort_constraint *)
 
 fun is_sort_constraint (Const ("Pure.sort_constraint", _) $ Const ("Pure.type", _)) = true