Hi guys. I'm wondering how to throw exception from...

# kotlin-native

[salomonbrys]

Hi guys.
I'm wondering how to throw exception from suspending function in Swift using Kotlin 1.4-M3.
Here's the setup: I have a Kotlin interface like this:

interface Foo {
    @Throws(CancellationException::class, MyException::class)
    suspend fun bar(param: Int): String
}

This interface gets translated thusly in Swift:

public protocol Foo {
    /**
     @note This method converts instances of CancellationException, MyException to errors.
     Other uncaught Kotlin exceptions are fatal.
    */
    func bar(param: Int32, completionHandler: @escaping (String?, Error?) -> Void)
}

I can (and do) implement this interface in Swift, creating a class with coroutine functions that I can use in Kotlin (btw, blown away by the fact that it actually works, amazing job!).
What I don't see, however, is how can the bar function use the completionHandler with a MyException . In other words, I need to express a async failure in Kotlin. In other other words, the bar function may fail asynchronously, and I need the coroutine (not the callback) to throw a MyException :

class SwiftFoo : Foo {
    func bar(param: Int32, completionHandler: @escaping (TCPSocket?, Error?) -> Void) {
        someSwiftAsyncApi(param) { result in
            if let result = result { completionHandler(result, nil) }
            else { completionHandler(nil, MyException("someSwiftAsyncApi failed!")) } // TYPE ERROR
        }
    }
}

This does not compile because MyException is not a Swift Error.
Any way to do this?