6 files declare their use of ContactFormInterface

ContactController.php in core/modules/contact/src/Controller/ContactController.php
ContactForm.php in core/modules/contact/src/Entity/ContactForm.php
ContactFormValidationTest.php in core/modules/contact/tests/src/Kernel/ContactFormValidationTest.php
ContactStorageTestHooks.php in core/modules/contact/tests/modules/contact_storage_test/src/Hook/ContactStorageTestHooks.php
contact_storage_test.module in core/modules/contact/tests/modules/contact_storage_test/contact_storage_test.module
MigrateContactCategoryTest.php in core/modules/contact/tests/src/Kernel/Migrate/MigrateContactCategoryTest.php

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