anchor.diff:    Token get beginToken => breakKeyword;
   
     @override
  -  Iterable<SyntacticEntity> get childEntities => ChildEntities()
  -    ..add(breakKeyword)
  -    ..add(_label)
  -    ..add(semicolon);
  -
  -  @override
     Token get endToken => semicolon;
   
     @override
  
positive.code:   }
  
    @override
    Iterable<SyntacticEntity> get childEntities => super._childEntities
      ..add(keyword)
      ..add(_type)
      ..add(_identifier);
  
    @override
    LocalVariableElement? get declaredElement {
      return _identifier.staticElement as LocalVariableElement;
    }
  
negative.code:   set value(StringLiteral? value) {
      _value = _becomeParentOf(value as StringLiteralImpl);
    }
  
    @override
    ChildEntities get _childEntities => ChildEntities()
      ..addToken('ifKeyword', ifKeyword)
      ..addToken('leftParenthesis', leftParenthesis)
      ..addNode('name', name)
      ..addToken('equalToken', equalToken)
      ..addNode('value', value)
      ..addToken('rightParenthesis', rightParenthesis)
      ..addNode('uri', uri);
  
    @override
    E? accept<E>(AstVisitor<E> visitor) => visitor.visitConfiguration(this);
  