22 files declare their use of DataDefinitionInterface

ComputedFileUrlTest.php in core/modules/file/tests/src/Kernel/ComputedFileUrlTest.php
ConsoleInputCollector.php in core/lib/Drupal/Core/Recipe/ConsoleInputCollector.php
ContentEntityNormalizerTest.php in core/modules/serialization/tests/src/Unit/Normalizer/ContentEntityNormalizerTest.php
ContextTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/ContextTest.php
DateTimeComputed.php in core/modules/datetime/src/DateTimeComputed.php
EntityFieldTest.php in core/tests/Drupal/KernelTests/Core/Entity/EntityFieldTest.php
FieldItemList.php in core/lib/Drupal/Core/Field/FieldItemList.php
FieldItemListTest.php in core/tests/Drupal/Tests/Core/Field/FieldItemListTest.php
FieldItemNormalizer.php in core/modules/jsonapi/src/Normalizer/FieldItemNormalizer.php
FieldStorageGetPropertyDefinitionTest.php in core/tests/Drupal/KernelTests/Core/Field/FieldStorageGetPropertyDefinitionTest.php
FieldTestItem.php in core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php
InputCollectorInterface.php in core/lib/Drupal/Core/Recipe/InputCollectorInterface.php
InputTest.php in core/tests/Drupal/KernelTests/Core/Recipe/InputTest.php
InternalTypedDataTestTrait.php in core/modules/serialization/tests/src/Unit/Normalizer/InternalTypedDataTestTrait.php
ListElement.php in core/modules/config_translation/src/FormElement/ListElement.php
Mapping.php in core/lib/Drupal/Core/Config/Schema/Mapping.php
RecipeInputFormTrait.php in core/lib/Drupal/Core/Recipe/RecipeInputFormTrait.php
SqlContentEntityStorageSchemaTest.php in core/tests/Drupal/Tests/Core/Entity/Sql/SqlContentEntityStorageSchemaTest.php
TextProcessed.php in core/modules/text/src/TextProcessed.php
TextProcessedTest.php in core/modules/text/tests/src/Unit/TextProcessedTest.php
TimestampItemNormalizerTest.php in core/modules/serialization/tests/src/Unit/Normalizer/TimestampItemNormalizerTest.php
TypedDataDefinitionTest.php in core/tests/Drupal/KernelTests/Core/TypedData/TypedDataDefinitionTest.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.