12 files declare their use of MessengerInterface

BlockListBuilder.php in core/modules/block/src/BlockListBuilder.php
Cookie.php in core/modules/user/src/Authentication/Provider/Cookie.php
DeleteMultipleForm.php in core/lib/Drupal/Core/Entity/Form/DeleteMultipleForm.php
FormAjaxSubscriber.php in core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php
FormAjaxSubscriberTest.php in core/tests/Drupal/Tests/Core/Form/EventSubscriber/FormAjaxSubscriberTest.php
FormErrorHandlerTest.php in core/tests/Drupal/Tests/Core/Form/FormErrorHandlerTest.php
MaintenanceModeSubscriber.php in core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
MessageAction.php in core/lib/Drupal/Core/Action/Plugin/Action/MessageAction.php
MessengerTest.php in core/tests/Drupal/KernelTests/Core/Messenger/MessengerTest.php
RoleListBuilder.php in core/modules/user/src/RoleListBuilder.php
UserMultipleCancelConfirm.php in core/modules/user/src/Form/UserMultipleCancelConfirm.php
VocabularyListBuilder.php in core/modules/taxonomy/src/VocabularyListBuilder.php

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