6 files declare their use of ResolverInterface in GraphQL 8.4

DataProducerProxy.php in src/Plugin/GraphQL/DataProducer/DataProducerProxy.php

MockingTrait.php in tests/src/Traits/MockingTrait.php

ResolverBuilder.php in src/GraphQL/ResolverBuilder.php

ResolverBuilderTest.php in tests/src/Kernel/ResolverBuilderTest.php

ResolverRegistry.php in src/GraphQL/ResolverRegistry.php

ResolverRegistryInterface.php in src/GraphQL/ResolverRegistryInterface.php