19 files declare their use of ItemInterface in Feeds 8.3

AfterParseBase.php in src/EventSubscriber/AfterParseBase.php

AfterParseBaseTest.php in tests/src/Unit/EventSubscriber/AfterParseBaseTest.php

BasicFieldSource.php in src/Feeds/Source/BasicFieldSource.php

EntityEvent.php in src/Event/EntityEvent.php

EntityProcessorBase.php in src/Feeds/Processor/EntityProcessorBase.php

EntityProcessorBaseTest.php in tests/src/Kernel/Feeds/Processor/EntityProcessorBaseTest.php

Feed.php in src/Entity/Feed.php

FeedInterface.php in src/FeedInterface.php

FeedsExecutable.php in src/FeedsExecutable.php

FeedsExecutableTest.php in tests/src/Unit/FeedsExecutableTest.php

ItemTestBase.php in tests/src/Unit/Feeds/Item/ItemTestBase.php

ParserResult.php in src/Result/ParserResult.php

ParserResultInterface.php in src/Result/ParserResultInterface.php

ParserResultTest.php in tests/src/Unit/Result/ParserResultTest.php

ProcessEvent.php in src/Event/ProcessEvent.php

ProcessEventTest.php in tests/src/Unit/Event/ProcessEventTest.php

ProcessorInterface.php in src/Plugin/Type/Processor/ProcessorInterface.php

SiteSource.php in tests/modules/feeds_test_extra_sources/src/Feeds/Source/SiteSource.php

SourceInterface.php in src/Plugin/Type/Source/SourceInterface.php