Sendability of function types in property does not match requirement in protocol

Question

I am trying to add a protocol which has all the attributes and functions of a Process but I see a warning with terminationHandler.

I was hoping not to see this warning since @Sendable is already added to terminationHandler.

protocol ProcessProtocol {
    var executableURL: URL? { get set }
    var arguments: [String]? { get set }
    var environment: [String : String]? { get set }
    var currentDirectoryURL: URL? { get set }
    var standardInput: Any? { get set }
    var standardOutput: Any? { get set }
    var standardError: Any? { get set }
    func run() throws
    func interrupt()
    func terminate()
    func suspend() -> Bool
    func resume() -> Bool
    var processIdentifier: Int32 { get }
    var isRunning: Bool { get }
    var terminationStatus: Int32 { get }
    var terminationReason: Process.TerminationReason { get }
    var terminationHandler: (@Sendable (Process) -> Void)? { get set }
    var qualityOfService: QualityOfService { get set }
}

extension Process: ProcessProtocol {}

Answer 1

It is a bit odd indeed, because your protocol signature exactly matches what the Developer Documentation signature shows for Process - terminationHandler. Removing the @Sendable notation actually resolves the warning, not sure why. I'd submit a bug report to Apple regarding this.