13 files declare their use of Config

BlockTheme.php in core/modules/block/src/Plugin/migrate/process/BlockTheme.php
ConfigCRUDTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigCRUDTest.php
ConfigEntityStorage.php in core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php
ConfigEntityStorageTest.php in core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
ConfigEventsTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigEventsTest.php
ConfigFactoryTest.php in core/tests/Drupal/Tests/Core/Config/ConfigFactoryTest.php
ConfigImportSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
ConfigTest.php in core/tests/Drupal/Tests/Core/Config/ConfigTest.php
ImportableEntityStorageInterface.php in core/lib/Drupal/Core/Config/Entity/ImportableEntityStorageInterface.php
QueryFactory.php in core/lib/Drupal/Core/Config/Entity/Query/QueryFactory.php
QueryFactoryTest.php in core/tests/Drupal/Tests/Core/Config/Entity/Query/QueryFactoryTest.php
theme.inc in core/includes/theme.inc
The theme system, which controls the output of Drupal.
UserUpdate7002.php in core/modules/user/src/Plugin/migrate/process/d6/UserUpdate7002.php

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