class NonSendable { } actor MyActor { let nonSendable: NonSendable init(_ nonSendable: NonSendable) { self.nonSendable = nonSendable } } func makeActor(_ nonSendable: sending NonSendable) -> MyActor { MyActor(nonSendable) } let ns = NonSendable() let _ = makeActor(ns) let _ = makeActor(ns) // no data race detected func f() { let ns = NonSendable() let _ = makeActor(ns) // let _ = makeActor(ns) // when uncommenting this line, a data race is (correctly) detected }