117 files declare their use of LanguageManagerInterface

AccountForm.php in core/modules/user/src/AccountForm.php
ActiveLinkResponseFilter.php in core/lib/Drupal/Core/EventSubscriber/ActiveLinkResponseFilter.php
AjaxResponseAttachmentsProcessor.php in core/lib/Drupal/Core/Ajax/AjaxResponseAttachmentsProcessor.php
AliasManager.php in core/modules/path_alias/src/AliasManager.php
AssetResolver.php in core/lib/Drupal/Core/Asset/AssetResolver.php
BaseFieldOverrideStorage.php in core/lib/Drupal/Core/Field/BaseFieldOverrideStorage.php
BigPipeResponseAttachmentsProcessor.php in core/modules/big_pipe/src/Render/BigPipeResponseAttachmentsProcessor.php
BigPipeResponseAttachmentsProcessorTest.php in core/modules/big_pipe/tests/src/Unit/Render/BigPipeResponseAttachmentsProcessorTest.php
BlockForm.php in core/modules/block/src/BlockForm.php
BookBreadcrumbBuilder.php in core/modules/book/src/BookBreadcrumbBuilder.php
BookManager.php in core/modules/book/src/BookManager.php
BulkForm.php in core/modules/views/src/Plugin/views/field/BulkForm.php
CheckRequirementsTest.php in core/modules/migrate/tests/src/Unit/Plugin/migrate/destination/CheckRequirementsTest.php
CKEditor5.php in core/modules/ckeditor5/src/Plugin/Editor/CKEditor5.php
CommentStorage.php in core/modules/comment/src/CommentStorage.php
CommentViewBuilder.php in core/modules/comment/src/CommentViewBuilder.php
Config.php in core/modules/migrate/src/Plugin/migrate/destination/Config.php
ConfigEntityMapper.php in core/modules/config_translation/src/ConfigEntityMapper.php
ConfigEntityStorage.php in core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php
ConfigEntityStorageTest.php in core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
ConfigMapperManager.php in core/modules/config_translation/src/ConfigMapperManager.php
ConfigNamesMapper.php in core/modules/config_translation/src/ConfigNamesMapper.php
ConfigSubscriber.php in core/modules/language/src/EventSubscriber/ConfigSubscriber.php
ConfigTranslationController.php in core/modules/config_translation/src/Controller/ConfigTranslationController.php
ConfigTranslationOverviewAccess.php in core/modules/config_translation/src/Access/ConfigTranslationOverviewAccess.php
ConfigurableLanguageManagerInterface.php in core/modules/language/src/ConfigurableLanguageManagerInterface.php
ConfigurableLanguageRenderer.php in core/modules/views/src/Entity/Render/ConfigurableLanguageRenderer.php
ContactLinkTest.php in core/modules/contact/tests/src/Unit/ContactLinkTest.php
ContentTranslationHandler.php in core/modules/content_translation/src/ContentTranslationHandler.php
ContentTranslationManageAccessCheck.php in core/modules/content_translation/src/Access/ContentTranslationManageAccessCheck.php
ContextualLinkManager.php in core/lib/Drupal/Core/Menu/ContextualLinkManager.php
ContextualLinkManagerTest.php in core/tests/Drupal/Tests/Core/Menu/ContextualLinkManagerTest.php
CssCollectionOptimizerLazy.php in core/lib/Drupal/Core/Asset/CssCollectionOptimizerLazy.php
CssCollectionOptimizerLazyUnitTest.php in core/tests/Drupal/Tests/Core/Asset/CssCollectionOptimizerLazyUnitTest.php
CurrentLanguageContext.php in core/lib/Drupal/Core/Language/ContextProvider/CurrentLanguageContext.php
DataEntityRow.php in core/modules/rest/src/Plugin/views/row/DataEntityRow.php
DateFormatter.php in core/lib/Drupal/Core/Datetime/DateFormatter.php
EmailAction.php in core/lib/Drupal/Core/Action/Plugin/Action/EmailAction.php
EntityConfigBase.php in core/modules/migrate/src/Plugin/migrate/destination/EntityConfigBase.php
EntityDisplayRepository.php in core/lib/Drupal/Core/Entity/EntityDisplayRepository.php
EntityField.php in core/modules/views/src/Plugin/views/field/EntityField.php
EntityFieldManager.php in core/lib/Drupal/Core/Entity/EntityFieldManager.php
EntityFieldManagerTest.php in core/tests/Drupal/Tests/Core/Entity/EntityFieldManagerTest.php
EntityFieldRenderer.php in core/modules/views/src/Entity/Render/EntityFieldRenderer.php
EntityFormDisplayAccessControlHandlerTest.php in core/tests/Drupal/Tests/Core/Entity/Access/EntityFormDisplayAccessControlHandlerTest.php
EntityOperations.php in core/modules/views/src/Plugin/views/field/EntityOperations.php
EntityRepository.php in core/lib/Drupal/Core/Entity/EntityRepository.php
EntityRepositoryTest.php in core/tests/Drupal/Tests/Core/Entity/EntityRepositoryTest.php
EntityRow.php in core/modules/views/src/Plugin/views/row/EntityRow.php
EntitySearchPage.php in core/modules/search/src/Plugin/migrate/destination/EntitySearchPage.php
EntityTypeBundleInfo.php in core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php
EntityTypeBundleInfoTest.php in core/tests/Drupal/Tests/Core/Entity/EntityTypeBundleInfoTest.php
EntityUserRole.php in core/modules/user/src/Plugin/migrate/destination/EntityUserRole.php
EntityUuidConverter.php in core/modules/jsonapi/src/ParamConverter/EntityUuidConverter.php
EntityViewBuilder.php in core/lib/Drupal/Core/Entity/EntityViewBuilder.php
ExportForm.php in core/modules/locale/src/Form/ExportForm.php
FieldConfigStorage.php in core/modules/field/src/FieldConfigStorage.php
FieldStorageConfigStorage.php in core/modules/field/src/FieldStorageConfigStorage.php
FileEventSubscriber.php in core/modules/file/src/EventSubscriber/FileEventSubscriber.php
FinishResponseSubscriber.php in core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
FinishResponseSubscriberTest.php in core/tests/Drupal/Tests/Core/EventSubscriber/FinishResponseSubscriberTest.php
HelpSearch.php in core/modules/help/src/Plugin/Search/HelpSearch.php
HelpTopicSection.php in core/modules/help/src/Plugin/HelpSection/HelpTopicSection.php
HtmlResponseAttachmentsProcessor.php in core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
Importer.php in core/lib/Drupal/Core/DefaultContent/Importer.php
JsCollectionOptimizerLazy.php in core/lib/Drupal/Core/Asset/JsCollectionOptimizerLazy.php
KeyValueEntityStorage.php in core/lib/Drupal/Core/Entity/KeyValueStore/KeyValueEntityStorage.php
Language.php in core/modules/language/src/Plugin/Condition/Language.php
Language.php in core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Language.php
LanguageBlock.php in core/modules/language/src/Plugin/Block/LanguageBlock.php
LanguageConverter.php in core/modules/language/src/LanguageConverter.php
LanguageFilter.php in core/modules/views/src/Plugin/views/filter/LanguageFilter.php
LanguageFormatter.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/LanguageFormatter.php
LanguageListBuilder.php in core/modules/language/src/LanguageListBuilder.php
LanguagePluginTest.php in core/modules/ckeditor5/tests/src/Unit/LanguagePluginTest.php
LanguagesCacheContext.php in core/lib/Drupal/Core/Cache/Context/LanguagesCacheContext.php
LanguageTestController.php in core/modules/language/tests/language_test/src/Controller/LanguageTestController.php
LinkApproveTest.php in core/modules/comment/tests/src/Unit/Plugin/views/field/LinkApproveTest.php
LinkBase.php in core/modules/views/src/Plugin/views/field/LinkBase.php
LinkBaseTest.php in core/modules/views/tests/src/Unit/Plugin/views/field/LinkBaseTest.php
LinkReplyTest.php in core/modules/comment/tests/src/Unit/Plugin/views/field/LinkReplyTest.php
LocalActionManager.php in core/lib/Drupal/Core/Menu/LocalActionManager.php
LocaleLookup.php in core/modules/locale/src/LocaleLookup.php
LocaleTranslation.php in core/modules/locale/src/LocaleTranslation.php
LocalTaskManager.php in core/lib/Drupal/Core/Menu/LocalTaskManager.php
MachineNameTest.php in core/tests/Drupal/Tests/Core/Render/Element/MachineNameTest.php
MailHandler.php in core/modules/contact/src/MailHandler.php
MediaListBuilder.php in core/modules/media/src/MediaListBuilder.php
MenuLinkContent.php in core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php
MenuLinkContentDeprecationsTest.php in core/modules/menu_link_content/tests/src/Kernel/MenuLinkContentDeprecationsTest.php
MessageForm.php in core/modules/contact/src/MessageForm.php
MigrationPluginManager.php in core/modules/migrate_drupal/src/MigrationPluginManager.php
MigrationPluginManager.php in core/modules/migrate/src/Plugin/MigrationPluginManager.php
NegotiationUrlForm.php in core/modules/language/src/Form/NegotiationUrlForm.php
NodeGrantDatabaseStorage.php in core/modules/node/src/NodeGrantDatabaseStorage.php
NodeRevisionRevertTranslationForm.php in core/modules/node/src/Form/NodeRevisionRevertTranslationForm.php
NodeSearch.php in core/modules/node/src/Plugin/Search/NodeSearch.php
NodeTranslationExceptionSubscriber.php in core/modules/node/src/EventSubscriber/NodeTranslationExceptionSubscriber.php
PathAliasListBuilder.php in core/modules/path/src/PathAliasListBuilder.php
PluralFormula.php in core/modules/locale/src/PluralFormula.php
RenderedEntity.php in core/modules/views/src/Plugin/views/field/RenderedEntity.php
RenderedEntityTest.php in core/modules/views/tests/src/Unit/Plugin/views/field/RenderedEntityTest.php
RendererBase.php in core/modules/views/src/Entity/Render/RendererBase.php
RevisionLinkDeleteTest.php in core/modules/node/tests/src/Unit/Plugin/views/field/RevisionLinkDeleteTest.php
RevisionLinkRevertTest.php in core/modules/node/tests/src/Unit/Plugin/views/field/RevisionLinkRevertTest.php
RevisionLinkTest.php in core/modules/node/tests/src/Unit/Plugin/views/field/RevisionLinkTest.php
RouteProvider.php in core/lib/Drupal/Core/Routing/RouteProvider.php
SanitizeNameTest.php in core/modules/file/tests/src/Unit/SanitizeNameTest.php
ShortcutSetStorage.php in core/modules/shortcut/src/ShortcutSetStorage.php
SqlContentEntityStorage.php in core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php
Token.php in core/lib/Drupal/Core/Utility/Token.php
TranslateFormBase.php in core/modules/locale/src/Form/TranslateFormBase.php
UserPasswordForm.php in core/modules/user/src/Form/UserPasswordForm.php
VersionHistoryController.php in core/lib/Drupal/Core/Entity/Controller/VersionHistoryController.php
ViewDuplicateForm.php in core/modules/views_ui/src/ViewDuplicateForm.php
ViewsData.php in core/modules/views/src/ViewsData.php
ViewsQueryAlter.php in core/modules/workspaces/src/ViewsQueryAlter.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.