9 files declare their use of ServerRequestInterface in Zircon Profile 8

ControllerResolver.php in core/lib/Drupal/Core/Controller/ControllerResolver.php

Contains \Drupal\Core\Controller\ControllerResolver.

ControllerResolverTest.php in core/tests/Drupal/Tests/Core/Controller/ControllerResolverTest.php

Contains \Drupal\Tests\Core\Controller\ControllerResolverTest.

HttpFoundationFactory.php in vendor/symfony/psr-http-message-bridge/Factory/HttpFoundationFactory.php

HttpFoundationFactoryInterface.php in vendor/symfony/psr-http-message-bridge/HttpFoundationFactoryInterface.php

HttpMessageFactoryInterface.php in vendor/symfony/psr-http-message-bridge/HttpMessageFactoryInterface.php

Server.php in vendor/zendframework/zend-diactoros/src/Server.php

ServerRequest.php in vendor/zendframework/zend-diactoros/src/ServerRequest.php

ServerRequest.php in vendor/symfony/psr-http-message-bridge/Tests/Fixtures/ServerRequest.php

ServerRequestFactory.php in vendor/zendframework/zend-diactoros/src/ServerRequestFactory.php