44 files declare their use of PluginInspectionInterface in Drupal 8

ActionInterface.php in core/lib/Drupal/Core/Action/ActionInterface.php

BlockPluginInterface.php in core/lib/Drupal/Core/Block/BlockPluginInterface.php

CKEditorPluginInterface.php in core/modules/ckeditor/src/CKEditorPluginInterface.php

ConditionInterface.php in core/lib/Drupal/Core/Condition/ConditionInterface.php

DefaultLazyPluginCollectionTest.php in core/tests/Drupal/Tests/Core/Plugin/DefaultLazyPluginCollectionTest.php

EditorPluginInterface.php in core/modules/editor/src/Plugin/EditorPluginInterface.php

ElementInterface.php in core/lib/Drupal/Core/Render/Element/ElementInterface.php

FilterFormat.php in core/modules/filter/src/Entity/FilterFormat.php

FilterInterface.php in core/modules/filter/src/Plugin/FilterInterface.php

HelpSectionPluginInterface.php in core/modules/help/src/HelpSectionPluginInterface.php

HelpTopicPluginInterface.php in core/modules/help_topics/src/HelpTopicPluginInterface.php

ImageEffectInterface.php in core/modules/image/src/ImageEffectInterface.php

ImageToolkitInterface.php in core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php

ImageToolkitOperationInterface.php in core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationInterface.php

InPlaceEditorInterface.php in core/modules/quickedit/src/Plugin/InPlaceEditorInterface.php

LayoutEntityHelperTraitTest.php in core/modules/layout_builder/tests/src/Unit/LayoutEntityHelperTraitTest.php

LayoutInterface.php in core/lib/Drupal/Core/Layout/LayoutInterface.php

MediaSourceInterface.php in core/modules/media/src/MediaSourceInterface.php

MenuLinkInterface.php in core/lib/Drupal/Core/Menu/MenuLinkInterface.php

MenuLinkParentTest.php in core/modules/migrate/tests/src/Unit/process/MenuLinkParentTest.php

MigrateDestinationInterface.php in core/modules/migrate/src/Plugin/MigrateDestinationInterface.php

MigrateFieldInterface.php in core/modules/migrate_drupal/src/Plugin/MigrateFieldInterface.php

MigrateIdMapInterface.php in core/modules/migrate/src/Plugin/MigrateIdMapInterface.php

MigrateProcessInterface.php in core/modules/migrate/src/Plugin/MigrateProcessInterface.php

MigrateSourceInterface.php in core/modules/migrate/src/Plugin/MigrateSourceInterface.php

MigrationInterface.php in core/modules/migrate/src/Plugin/MigrationInterface.php

PluginDependencyTrait.php in core/lib/Drupal/Core/Plugin/PluginDependencyTrait.php

PluginDependencyTraitTest.php in core/tests/Drupal/Tests/Core/Plugin/PluginDependencyTraitTest.php

PluginFormBase.php in core/lib/Drupal/Core/Plugin/PluginFormBase.php

PluginInterface.php in core/modules/views/src/Plugin/views/PluginInterface.php

PluginSettingsInterface.php in core/lib/Drupal/Core/Field/PluginSettingsInterface.php

PluginWithFormsInterface.php in core/lib/Drupal/Core/Plugin/PluginWithFormsInterface.php

QueueWorkerInterface.php in core/lib/Drupal/Core/Queue/QueueWorkerInterface.php

ResourceInterface.php in core/modules/rest/src/Plugin/ResourceInterface.php

SearchInterface.php in core/modules/search/src/Plugin/SearchInterface.php

SectionStorageInterface.php in core/modules/layout_builder/src/SectionStorageInterface.php

SerializedColumnNormalizerTrait.php in core/modules/serialization/src/Normalizer/SerializedColumnNormalizerTrait.php

SystemMenuOffCanvasForm.php in core/modules/system/src/Form/SystemMenuOffCanvasForm.php

TypedData.php in core/lib/Drupal/Core/TypedData/TypedData.php

VariantInterface.php in core/lib/Drupal/Core/Display/VariantInterface.php

ViewsPluginInterface.php in core/modules/views/src/Plugin/views/ViewsPluginInterface.php

WorkflowTypeConfigureFormBase.php in core/modules/workflows/src/Plugin/WorkflowTypeConfigureFormBase.php

WorkflowTypeStateFormBase.php in core/modules/workflows/src/Plugin/WorkflowTypeStateFormBase.php

WorkflowTypeTransitionFormBase.php in core/modules/workflows/src/Plugin/WorkflowTypeTransitionFormBase.php