7 files declare their use of UnroutedUrlAssemblerInterface in Drupal 9

FormSubmitterTest.php in core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php

GotoAction.php in core/lib/Drupal/Core/Action/Plugin/Action/GotoAction.php

LinkTest.php in core/modules/jsonapi/tests/src/Unit/JsonApiResource/LinkTest.php

RedirectResponseSubscriber.php in core/lib/Drupal/Core/EventSubscriber/RedirectResponseSubscriber.php

RedirectResponseSubscriberTest.php in core/tests/Drupal/Tests/Core/EventSubscriber/RedirectResponseSubscriberTest.php

RequestFormatRouteFilterTest.php in core/tests/Drupal/Tests/Core/Routing/RequestFormatRouteFilterTest.php

Url.php in core/lib/Drupal/Core/Url.php