8 files declare their use of ServiceProviderInterface

ConfigOverride.php in core/lib/Drupal/Core/Installer/ConfigOverride.php
CoreServiceProvider.php in core/lib/Drupal/Core/CoreServiceProvider.php
DrupalKernel.php in core/lib/Drupal/Core/DrupalKernel.php
InstallerServiceProvider.php in core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
KernelTestBase.php in core/tests/Drupal/KernelTests/KernelTestBase.php
NormalInstallerServiceProvider.php in core/lib/Drupal/Core/Installer/NormalInstallerServiceProvider.php
RouterTestServiceProvider.php in core/modules/system/tests/modules/router_test_directory/src/RouterTestServiceProvider.php
UpdateServiceProvider.php in core/lib/Drupal/Core/Update/UpdateServiceProvider.php

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