private static Collection<ClassDescriptor> getClassOrObjectDescriptorsByFqName(
      NamespaceDescriptor packageDescriptor, FqName path, boolean includeObjectDeclarations) {
    if (path.isRoot()) {
      return Collections.emptyList();
    }

    Collection<JetScope> scopes = Arrays.asList(packageDescriptor.getMemberScope());

    List<Name> names = path.pathSegments();
    if (names.size() > 1) {
      for (Name subName : path.pathSegments().subList(0, names.size() - 1)) {
        Collection<JetScope> tempScopes = Lists.newArrayList();
        for (JetScope scope : scopes) {
          ClassifierDescriptor classifier = scope.getClassifier(subName);
          if (classifier instanceof ClassDescriptorBase) {
            ClassDescriptorBase classDescriptor = (ClassDescriptorBase) classifier;
            tempScopes.add(classDescriptor.getUnsubstitutedInnerClassesScope());
          }
        }
        scopes = tempScopes;
      }
    }

    Name shortName = path.shortName();
    Collection<ClassDescriptor> resultClassifierDescriptors = Lists.newArrayList();
    for (JetScope scope : scopes) {
      ClassifierDescriptor classifier = scope.getClassifier(shortName);
      if (classifier instanceof ClassDescriptor) {
        resultClassifierDescriptors.add((ClassDescriptor) classifier);
      }
      if (includeObjectDeclarations) {
        ClassDescriptor objectDescriptor = scope.getObjectDescriptor(shortName);
        if (objectDescriptor != null) {
          resultClassifierDescriptors.add(objectDescriptor);
        }
      }
    }

    return resultClassifierDescriptors;
  }
  @Nullable
  public static ClassDescriptor getKotlinBuiltinClassDescriptor(@NotNull FqName qualifiedName) {
    if (!qualifiedName.firstSegmentIs(KotlinBuiltIns.BUILT_INS_PACKAGE_NAME)) return null;

    List<Name> segments = qualifiedName.pathSegments();
    if (segments.size() < 2) return null;

    JetScope scope = KotlinBuiltIns.getInstance().getBuiltInsPackageScope();
    for (int i = 1, size = segments.size(); i < size; i++) {
      ClassifierDescriptor classifier = scope.getClassifier(segments.get(i));
      if (classifier == null) return null;
      assert classifier instanceof ClassDescriptor
          : "Unexpected classifier in built-ins: " + classifier;
      scope = ((ClassDescriptor) classifier).getUnsubstitutedInnerClassesScope();
    }

    return (ClassDescriptor) scope.getContainingDeclaration();
  }