11 files declare their use of DiscoveryInterface in Zircon Profile 8

AnnotatedClassDiscovery.php in core/lib/Drupal/Component/Annotation/Plugin/Discovery/AnnotatedClassDiscovery.php

Contains \Drupal\Component\Annotation\Plugin\Discovery\AnnotatedClassDiscovery.

ConfigSchemaDiscovery.php in core/lib/Drupal/Core/Config/Schema/ConfigSchemaDiscovery.php

Contains \Drupal\Core\Config\Schema\ConfigSchemaDiscovery.

DefaultFactory.php in core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php

Contains \Drupal\Component\Plugin\Factory\DefaultFactory.

EntityTypeManagerTest.php in core/tests/Drupal/Tests/Core/Entity/EntityTypeManagerTest.php

Contains \Drupal\Tests\Core\Entity\EntityTypeManagerTest.

HookDiscovery.php in core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php

Contains \Drupal\Core\Plugin\Discovery\HookDiscovery.

InfoHookDecorator.php in core/lib/Drupal/Core/Plugin/Discovery/InfoHookDecorator.php

Contains \Drupal\Core\Plugin\Discovery\InfoHookDecorator.

LocalActionManagerTest.php in core/tests/Drupal/Tests/Core/Menu/LocalActionManagerTest.php

Contains \Drupal\Tests\Core\Menu\LocalActionManagerTest.

MailManagerTest.php in core/tests/Drupal/Tests/Core/Mail/MailManagerTest.php

Contains \Drupal\Tests\Core\Mail\MailManagerTest.

PluginManagerInterface.php in core/lib/Drupal/Component/Plugin/PluginManagerInterface.php

Contains \Drupal\Component\Plugin\PluginManagerInterface.

YamlDiscovery.php in core/lib/Drupal/Core/Plugin/Discovery/YamlDiscovery.php

Contains \Drupal\Core\Plugin\Discovery\YamlDiscovery.

YamlDiscoveryDecorator.php in core/lib/Drupal/Core/Plugin/Discovery/YamlDiscoveryDecorator.php

Contains \Drupal\Core\Plugin\Discovery\YamlDiscoveryDecorator.