13 files declare their use of AccessResultInterface in Drupal 9

AccessibleTestingTrait.php in core/modules/block_content/tests/src/Unit/Access/AccessibleTestingTrait.php

AccessResultTest.php in core/tests/Drupal/Tests/Core/Access/AccessResultTest.php

Contains \Drupal\Tests\Core\Access\AccessResultTest.

BlockPluginHasSettingsTrayFormAccessCheckTest.php in core/modules/settings_tray/tests/src/Unit/Access/BlockPluginHasSettingsTrayFormAccessCheckTest.php

Element.php in core/lib/Drupal/Core/Render/Element.php

EntityAccessDeniedHttpException.php in core/modules/jsonapi/src/Exception/EntityAccessDeniedHttpException.php

FieldResolver.php in core/modules/jsonapi/src/Context/FieldResolver.php

FormBuilder.php in core/lib/Drupal/Core/Form/FormBuilder.php

MediaAccessControlHandlerTest.php in core/modules/media/tests/src/Kernel/MediaAccessControlHandlerTest.php

MenuLinkContentEntityAccessTest.php in core/modules/menu_link_content/tests/src/Unit/MenuLinkContentEntityAccessTest.php

MenuLinkTree.php in core/lib/Drupal/Core/Menu/MenuLinkTree.php

Renderer.php in core/lib/Drupal/Core/Render/Renderer.php

RendererTest.php in core/tests/Drupal/Tests/Core/Render/RendererTest.php

Contains \Drupal\Tests\Core\Render\RendererTest.

ResourceResponseTestTrait.php in core/modules/jsonapi/tests/src/Functional/ResourceResponseTestTrait.php