@Nullable
  public final DomElement getDomElement(final XmlTag element) {
    if (myChanging) return null;

    final DomInvocationHandler handler = getDomHandler(element);
    return handler != null ? handler.getProxy() : null;
  }
  @NotNull
  public XmlFile getContainingFile(@NotNull DomElement domElement) {
    if (domElement instanceof DomFileElement) {
      return ((DomFileElement) domElement).getFile();
    }
    DomInvocationHandler handler = DomManagerImpl.getDomInvocationHandler(domElement);
    assert handler != null : domElement;
    while (handler != null
        && !(handler instanceof DomRootInvocationHandler)
        && handler.getXmlTag() == null) {
      handler = handler.getParentHandler();
    }
    if (handler instanceof DomRootInvocationHandler) {
      return ((DomRootInvocationHandler) handler).getParent().getFile();
    }
    assert handler != null;
    XmlTag tag = handler.getXmlTag();
    assert tag != null;
    while (true) {
      final PsiElement parentTag = PhysicalDomParentStrategy.getParentTagCandidate(tag);
      if (!(parentTag instanceof XmlTag)) {
        return (XmlFile) tag.getContainingFile();
      }

      tag = (XmlTag) parentTag;
    }
  }
  public static List<XmlTag> getCustomSubTags(
      final DomInvocationHandler handler, final XmlTag[] subTags, final XmlFile file) {
    if (subTags.length == 0) {
      return Collections.emptyList();
    }

    final DomGenericInfoEx info = handler.getGenericInfo();
    final Set<XmlName> usedNames = new THashSet<XmlName>();
    List<? extends DomCollectionChildDescription> collectionChildrenDescriptions =
        info.getCollectionChildrenDescriptions();
    //noinspection ForLoopReplaceableByForEach
    for (int i = 0, size = collectionChildrenDescriptions.size(); i < size; i++) {
      DomCollectionChildDescription description = collectionChildrenDescriptions.get(i);
      usedNames.add(description.getXmlName());
    }
    List<? extends DomFixedChildDescription> fixedChildrenDescriptions =
        info.getFixedChildrenDescriptions();
    //noinspection ForLoopReplaceableByForEach
    for (int i = 0, size = fixedChildrenDescriptions.size(); i < size; i++) {
      DomFixedChildDescription description = fixedChildrenDescriptions.get(i);
      usedNames.add(description.getXmlName());
    }
    return ContainerUtil.findAll(
        subTags,
        tag -> {
          if (StringUtil.isEmpty(tag.getName())) return false;

          for (final XmlName name : usedNames) {
            if (isNameSuitable(name, tag, handler, file)) {
              return false;
            }
          }
          return true;
        });
  }
 public static boolean isNameSuitable(
     final XmlName name,
     final XmlTag tag,
     @NotNull final DomInvocationHandler handler,
     final XmlFile file) {
   return isNameSuitable(handler.createEvaluatedXmlName(name), tag, file);
 }
  public static void assertValidity(DomElement element, String msg) {
    if (element instanceof DomFileElementImpl) {
      final String s = ((DomFileElementImpl) element).checkValidity();
      if (s != null) {
        throw new AssertionError(s);
      }
      return;
    }

    final DomInvocationHandler handler = DomManagerImpl.getDomInvocationHandler(element);
    assert handler != null;
    try {
      handler.assertValid();
    } catch (AssertionError e) {
      throw new AssertionError(msg + e.getMessage());
    }
  }
  static XmlFile getFile(DomElement domElement) {
    if (domElement instanceof DomFileElement) {
      return ((DomFileElement) domElement).getFile();
    }
    DomInvocationHandler handler = DomManagerImpl.getDomInvocationHandler(domElement);
    assert handler != null : domElement;
    while (true) {
      if (handler instanceof DomRootInvocationHandler) {
        return ((DomRootInvocationHandler) handler).getParent().getFile();
      }

      XmlTag tag = handler.getXmlTag();
      if (tag != null) {
        return getContainingFile(tag);
      }
      DomInvocationHandler parent = handler.getParentHandler();
      if (parent == null) {
        throw new AssertionError("No parent for " + handler.toStringEx());
      }
      handler = parent;
    }
  }
 static AbstractDomChildrenDescription findChildrenDescription(
     final XmlTag tag, final DomInvocationHandler parent) {
   final DomGenericInfoEx info = parent.getGenericInfo();
   return info.findChildrenDescription(
       parent, tag.getLocalName(), tag.getNamespace(), false, tag.getName());
 }