Vakul Rai
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
   */
  protected $trustedData = FALSE;

+  /**
+   * Indicates whether the config entity contains overridden data.
+   *
+   * @var bool
+   */
+  protected $hasOverrides = FALSE;
-  protected $hasOverrides = FALSE;
+  protected bool $hasOverrides = FALSE;
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
    return $this->trustedData;
  }

+  /**
+   * {@inheritdoc}
+   */
+  public function hasOverrides() {
-  public function hasOverrides() {
+  public function hasOverrides(): bool {
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityInterface.php
   */
  public function hasTrustedData();

+  /**
+   * Returns whether the config entity has overridden configuration.
+   *
+   * @return bool
+   *   TRUE if the entity has overridden configuration.
+   */
+  public function hasOverrides();
-  public function hasOverrides();
+  public function hasOverrides(): bool;
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php
      throw new EntityMalformedException('The entity does not have an ID.');
    }

+    /** @var \Drupal\Core\Config\Entity\ConfigEntityInterface $entity */
+    if ($entity->hasOverrides()) {
+      throw new UnsupportedEntityOperationException('A config entity with config overrides must not be saved. Use \Drupal\Core\Config\Entity\ConfigEntityStorageInterface::loadOverrideFree() to load a non-overridden config entity. Check issue https://www.drupal.org/project/drupal/issues/2910353 for more details');
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationRoleUiTest.php 0 → 100644
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationRoleUiTest.php 0 → 100644
+    parent::setUp();
+
+    ConfigurableLanguage::createFromLangcode('de')->save();
+    $user = $this->drupalCreateUser([
+      'administer site configuration',
+      'translate configuration',
+      'administer users',
+      'administer permissions',
+    ]);
+    $this->drupalLogin($user);
+  }
+
+  /**
+   * Test that permissions can be saved with translated role labels.
+   */
+  public function testDateFormatUi() {
-  public function testDateFormatUi() {
+  public function testDateFormatUi(): void {
--- a/core/modules/language/tests/src/Functional/Update/NonDefaultConfigSaveUpdateTest.php 0 → 100644
+++ b/core/modules/language/tests/src/Functional/Update/NonDefaultConfigSaveUpdateTest.php 0 → 100644
+class NonDefaultConfigSaveUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.8.0.filled.standard.php.gz',
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.config-non-default-language.php',
+    ];
+  }
+
+  /**
+   * Tests language_post_update_language_select_widget().
+   */
+  public function testNonDefaultConfigOverride() {
-  public function testNonDefaultConfigOverride() {
+  public function testNonDefaultConfigOverride(): void {
--- a/core/modules/views_ui/src/ViewUI.php
+++ b/core/modules/views_ui/src/ViewUI.php
    return $this;
  }

+  /**
+   * {@inheritdoc}
+   */
+  public function hasOverrides() {
-  public function hasOverrides() {
+  public function hasOverrides(): bool {
--- a/core/tests/Drupal/KernelTests/Core/Config/ConfigLanguageOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Config/ConfigLanguageOverrideTest.php
    $this->assertNull($override->get('value'));
  }

+  /**
+   * Tests language overrides of config entities.
+   */
+  public function testConfigEntityLanguageOverrides() {
-  public function testConfigEntityLanguageOverrides() {
+  public function testConfigEntityLanguageOverrides(): void {
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
    $this->entityStorage->save($entity);
  }

+  /**
+   * @covers ::save
+   */
+  public function testSaveWithOverrides() {
-  public function testSaveWithOverrides() {
+  public function testSaveWithOverrides(): void {
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
    }
  }

+  /**
+   * @covers ::load
+   * @covers ::postLoad
+   * @covers ::mapFromStorageRecords
+   * @covers ::doLoadMultiple
+   */
+  public function testLoadWithOverrides() {
-  public function testLoadWithOverrides() {
+  public function testLoadWithOverrides(): void {