7 files declare their use of ResultInterface in Facets 8

ArrayWidget.php in src/Plugin/facets/widget/ArrayWidget.php

QueryStringCreated.php in src/Event/QueryStringCreated.php

QueryStringTest.php in tests/src/Unit/Plugin/url_processor/QueryStringTest.php

SearchApiDateTest.php in tests/src/Kernel/Plugin/query_type/SearchApiDateTest.php

SearchApiGranularTest.php in tests/src/Unit/Plugin/query_type/SearchApiGranularTest.php

SearchApiStringTest.php in tests/src/Unit/Plugin/query_type/SearchApiStringTest.php

WidgetPluginBase.php in src/Widget/WidgetPluginBase.php