12 files declare their use of DataDefinitionInterface

ComputedFileUrlTest.php in core/modules/file/tests/src/Kernel/ComputedFileUrlTest.php
ContentEntityNormalizerTest.php in core/modules/serialization/tests/src/Unit/Normalizer/ContentEntityNormalizerTest.php
DateTimeComputed.php in core/modules/datetime/src/DateTimeComputed.php
EntityFieldTest.php in core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php
FieldItemBase.php in core/lib/Drupal/Core/Field/FieldItemBase.php
FieldItemList.php in core/lib/Drupal/Core/Field/FieldItemList.php
FieldTestItem.php in core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php
InternalTypedDataTestTrait.php in core/modules/serialization/tests/src/Unit/Normalizer/InternalTypedDataTestTrait.php
ListElement.php in core/modules/config_translation/src/FormElement/ListElement.php
TextProcessed.php in core/modules/text/src/TextProcessed.php
TimestampItemNormalizerTest.php in core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php
TypedDataDefinitionTest.php in core/tests/Drupal/KernelTests/Core/TypedData/TypedDataDefinitionTest.php

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