\ attrs ccAttrs ret namespace swift_##name COMPATIBILITY_PAREN(typedArgs) { \ static Override_##name Override; \ static swift_once_t Predicate; \ swift_once( \ &Predicate, [](void *) { Override = getOverride_##name(); }, nullptr); \ if (Override != nullptr) \ return Override(COMPATIBILITY_UNPAREN_WITH_COMMA(namedArgs) \ swift_##name##Impl); \ return swift_##name##Impl COMPATIBILITY_PAREN(namedArgs); \ } COMPATIBILITY_OVERRIDE(dynamicCastClass, const void *, , , swift::, (const void *object, const ClassMetadata *targetType), (object, targetType)) https://github.com/apple/swift/blob/main/stdlib/public/CompatibilityOverride/CompatibilityOverride.h 22