6 files declare their use of SubformStateInterface

CKEditor5.php in core/modules/ckeditor5/src/Plugin/Editor/CKEditor5.php
ConditionPluginBase.php in core/lib/Drupal/Core/Condition/ConditionPluginBase.php
ExtractorTest.php in core/tests/Drupal/Tests/Core/Theme/Icon/Plugin/ExtractorTest.php
IconExtractorSettingsFormTest.php in core/tests/Drupal/Tests/Core/Theme/Icon/IconExtractorSettingsFormTest.php
InlineBlock.php in core/modules/layout_builder/src/Plugin/Block/InlineBlock.php
SubformStateTest.php in core/tests/Drupal/Tests/Core/Form/SubformStateTest.php

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