produce a trigger when "eliminate_if" removes a definition

src/transform/eliminate_if.ml

@@ -69,9 +69,10 @@ let add_ld axl d = match d with
       let vl,e = open_ls_defn ld in
       begin match e with
         | Term t when has_if t ->
-            let f = elim_f (ls_defn_axiom ld) in
             let nm = ls.ls_name.id_short ^ "_def" in
             let pr = create_prsymbol (id_derive nm ls.ls_name) in
+            let hd = t_app ls (List.map t_var vl) t.t_ty in
+            let f = f_forall vl [[Term hd]] (elim_f (f_equ hd t)) in
             create_prop_decl Paxiom pr f :: axl, (ls, None)
         | _ ->
             axl, make_ls_defn ls vl (e_map elim_t elim_f e)