↓なら通ったけど、ちょっと・・・。そして onCancel に Sendable でない Box を渡せてしまってるのはなぜ？？？ func download(url: URL) async throws -> Data? { let urlSessionTask: Box<URLSessionTask> = .init() return try await withTaskCancellationHandler { return try await withUnsafeThrowingContinuation { continuation in let task = URLSession.shared.dataTask(with: url) { data, _, error in if let error = error { // Ideally translate NSURLErrorCancelled to CancellationError here continuation.resume(throwing: error) } else { continuation.resume(returning: data) } } task.resume() urlSessionTask.value = task } } onCancel: { urlSessionTask.value?.cancel() // runs immediately when cancelled } } final class Box<Value> { var value: Value? }
