37 files declare their use of Markup

AttributeTest.php in core/tests/Drupal/Tests/Core/Template/AttributeTest.php
CommentFieldPreprocessTest.php in core/modules/comment/tests/src/Kernel/CommentFieldPreprocessTest.php
ConfigFormBase.php in core/lib/Drupal/Core/Form/ConfigFormBase.php
ConfigTest.php in core/tests/Drupal/Tests/Core/Config/ConfigTest.php
EngineTwigTest.php in core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php
errors.inc in core/includes/errors.inc
Functions for error handling.
FieldPluginBaseTest.php in core/modules/views/tests/src/Unit/Plugin/field/FieldPluginBaseTest.php
FieldViewsDataProvider.php in core/modules/views/src/FieldViewsDataProvider.php
HtmlTag.php in core/lib/Drupal/Core/Render/Element/HtmlTag.php
HtmlTagTest.php in core/tests/Drupal/Tests/Core/Render/Element/HtmlTagTest.php
LinkGeneratorTest.php in core/tests/Drupal/Tests/Core/Utility/LinkGeneratorTest.php
MailManager.php in core/lib/Drupal/Core/Mail/MailManager.php
MailTest.php in core/modules/system/tests/src/Kernel/Mail/MailTest.php
MarkupNormalizerTest.php in core/modules/serialization/tests/src/Unit/Normalizer/MarkupNormalizerTest.php
Messenger.php in core/lib/Drupal/Core/Messenger/Messenger.php
MessengerTest.php in core/tests/Drupal/KernelTests/Core/Messenger/MessengerTest.php
ModulesListForm.php in core/modules/system/src/Form/ModulesListForm.php
PluginBaseTest.php in core/modules/views/tests/src/Kernel/Plugin/PluginBaseTest.php
Rearrange.php in core/modules/views_ui/src/Form/Ajax/Rearrange.php
RendererPlaceholdersTest.php in core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
RendererTest.php in core/tests/Drupal/Tests/Core/Render/RendererTest.php
RequirementsTrait.php in core/modules/mysql/src/RequirementsTrait.php
SerializerTest.php in core/modules/jsonapi/tests/src/Kernel/Serializer/SerializerTest.php
SystemAdminThemePreprocess.php in core/modules/system/src/Theme/SystemAdminThemePreprocess.php
SystemRequirementsHooks.php in core/modules/system/src/Hook/SystemRequirementsHooks.php
SystemTestController.php in core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
Test.php in core/modules/system/tests/modules/test_page_test/src/Controller/Test.php
TestController.php in core/modules/system/tests/modules/jswebassert_test/src/Controller/TestController.php
ThemePreprocess.php in core/lib/Drupal/Core/Theme/ThemePreprocess.php
TokenTest.php in core/tests/Drupal/Tests/Core/Utility/TokenTest.php
twig.engine in core/themes/engines/twig/twig.engine
Handles integration of Twig templates with the Drupal theme system.
TwigEnvironment.php in core/lib/Drupal/Core/Template/TwigEnvironment.php
TwigExtension.php in core/lib/Drupal/Core/Template/TwigExtension.php
TwigExtensionTest.php in core/modules/system/tests/src/Functional/Theme/TwigExtensionTest.php
TwigExtensionTest.php in core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
TwigMarkupInterfaceTest.php in core/tests/Drupal/KernelTests/Core/Theme/TwigMarkupInterfaceTest.php
TwigThemeEngine.php in core/lib/Drupal/Core/Template/TwigThemeEngine.php

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