public goto_statement(label_node v_label, location v_location)
     : base(v_location)
 {
     _label = v_label;
 }
 public labeled_statement(label_node v_label, statement_node v_statement, location v_location)
     : base(v_location)
 {
     _label     = v_label;
     _statement = v_statement;
 }