anchor.diff:    final Statement _body;
     final List<_CatchClause> _catches;
     final Statement? _finally;
  -  final _bodyNode = Node._();
   
     _TryStatement(this._body, this._catches, this._finally) : super._();
   
  
positive.code:     }
      _body._visit(h);
      if (_catches.isNotEmpty) {
        h._flow.tryCatchStatement_bodyEnd(_bodyNode);
        for (var catch_ in _catches) {
          catch_._visit(h);
        }
        h._flow.tryCatchStatement_end();
      }
      if (_finally != null) {
        h._flow.tryFinallyStatement_finallyBegin(
            _catches.isNotEmpty ? this : _bodyNode);
        _finally!._visit(h);
        h._flow.tryFinallyStatement_end();
      }
  
negative.code:       assignedVariables.beginNode();
      }
      _body._preVisit(assignedVariables);
      assignedVariables.endNode(_body);
      for (var catch_ in _catches) {
        catch_._preVisit(assignedVariables);
      }
  