packages/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/EnumTests.swift:15:1: error: extension declares a conformance of imported type 'DataWithEnum' to imported protocol 'Equatable'; this will not behave correctly if the owners of 'test_plugin' introduce this conformance in the future
 13 | }
 14 | 
 15 | extension DataWithEnum: Equatable {
    | |- error: extension declares a conformance of imported type 'DataWithEnum' to imported protocol 'Equatable'; this will not behave correctly if the owners of 'test_plugin' introduce this conformance in the future
    | `- note: add '@retroactive' to silence this warning
 16 |   public static func == (lhs: DataWithEnum, rhs: DataWithEnum) -> Bool {
 17 |     lhs.state == rhs.state