src/Pure/Isar/toplevel.ML

 fun loc_begin loc (Context.Theory thy) =
       (Context.Theory o loc_exit, loc_init (the_default ("-", Position.none) loc) thy)
   | loc_begin NONE (Context.Proof lthy) =
       (Context.Proof o Local_Theory.restore, lthy)
   | loc_begin (SOME loc) (Context.Proof lthy) =
-      (Context.Proof o Named_Target.reinit lthy, loc_init loc (loc_exit (Local_Theory.assert_nonbrittle lthy)));
+      (Context.Proof o Named_Target.reinit lthy,
+        loc_init loc (loc_exit (Local_Theory.assert_nonbrittle lthy)));
 
 
 (* datatype node *)
 
 datatype node =