在Swift方法中，指定了@MainActor，调用withCheckedContinuation并进行其他异步调用，看起来withCheckedContinuation在@MainActor线程上被调用，但其他异步调用不是。
这是巧合吗？
以下代码可以放入XCode为您创建的默认iOS App的ContentView.swift中：

import SwiftUI

func printCurrentThread(_ label: String) {
    print("\(label) called on \(Thread.current)")
}

class SomeNonThreadSafeLibrary {
    func getFromServer(msg: String, completionHandler: @escaping (String) -> Void) {
        DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
            completionHandler(msg)
        }
    }
}

class AppController: ObservableObject {
    @Published var something1: String = "not set"
    @Published var something2: String = "not set"
    var someNonThreadSafeLibrary: SomeNonThreadSafeLibrary? = SomeNonThreadSafeLibrary()

    func someOtherAsyncFunction(calledFrom: String) async {
        printCurrentThread("\(calledFrom) -> someOtherAsyncFunction")
    }

    func getSomethingAsynchronously() async -> String {
        printCurrentThread("getSomethingAsynchronously")
        await someOtherAsyncFunction(calledFrom: "getSomethingAsynchronously")
        return await withCheckedContinuation { continuation in
            printCurrentThread("getSomethingAsynchronously -> withCheckedContinuation")
            do {
                try Task.checkCancellation()
                self.someNonThreadSafeLibrary?.getFromServer(msg: "getSomethingAsynchronously") { result in
                    printCurrentThread("getSomethingAsynchronously -> getFromServer closure")
                    continuation.resume(returning: result)
                }
            }
            catch {}
        }
    }

    @MainActor
    func getSomethingAsynchronouslyWithMainActor() async -> String {
        printCurrentThread("getSomethingAsynchronouslyWithMainActor")
        await someOtherAsyncFunction(calledFrom: "getSomethingAsynchronouslyWithMainActor")
        return await withCheckedContinuation { continuation in
            printCurrentThread("getSomethingAsynchronouslyWithMainActor -> withCheckedContinuation")
            do {
                try Task.checkCancellation()
                self.someNonThreadSafeLibrary?.getFromServer(msg: "getSomethingAsynchronouslyWithMainActorWithMainActor") { result in
                    printCurrentThread("getSomethingAsynchronouslyWithMainActor -> getFromServer closure")
                    continuation.resume(returning: result)
                }
            }
            catch {}
        }
    }

    @MainActor
    func getValueForSomething() async {
        something1 = await getSomethingAsynchronously()
    }

    @MainActor
    func getValueForSomethingWithMainActor() async {
        something2 = await getSomethingAsynchronouslyWithMainActor()
    }

}

struct ContentView: View {
    @StateObject private var appController = AppController()
    var body: some View {
        VStack {
            Text("something1 is \(appController.something1)")
            Text("something2 is \(appController.something2)")
        }
        .task {
            await appController.getValueForSomething()
        }
        .task {
            await appController.getValueForSomethingWithMainActor()
        }
        .padding()
    }
}

代码的输出如下所示...
带@MainActor的func在线程1上调用，不带@MainActor的func在任意线程上调用，如预期：

getSomethingAsynchronouslyWithMainActor called on <_NSMainThread: 0x600001910400>{number = 1, name = main}
getSomethingAsynchronously called on <NSThread: 0x60000195c300>{number = 7, name = (null)}

然后从这些方法中的每一个调用不做任何事情的func someOtherAsyncFunction，在这两种情况下（即调用函数上有或没有@MainActor），它会在任意线程上被调用，这意味着函数上的@MainActor不会被它内部调用的函数继承：

getSomethingAsynchronously -> someOtherAsyncFunction called on <NSThread: 0x60000195c300>{number = 7, name = (null)}
getSomethingAsynchronouslyWithMainActor -> someOtherAsyncFunction called on <NSThread: 0x6000019582c0>{number = 6, name = (null)}

然而，在withCheckedContinuation闭包的特定情况下，当@MainActor在调用函数上时，它似乎确实在线程1上运行：

getSomethingAsynchronously -> withCheckedContinuation called on <NSThread: 0x60000195c300>{number = 7, name = (null)}
 getSomethingAsynchronouslyWithMainActor -> withCheckedContinuation called on <_NSMainThread: 0x600001910400>{number = 1, name = main}

那么...... withCheckedContinuation似乎通过其调用函数运行在@MainActor上，这仅仅是一个巧合，还是设计使然？为什么它只是withCheckedContinuation，而不是someOtherAsyncFunction？
如果是设计的，我可以从哪里获得更多关于指定位置的信息？