Demo the problem with naive await implementation

AwaitProblem.kt

import java.util.concurrent.CompletableFuture

// ======================================================================================================
// demo the problem with naive await implementation

fun main(args: Array<String>) {
    val n: Int = 100000
    var actualCount = 0;
    async<Unit> {
        repeat(n) { // repeat n times
            actualCount++
            await(someAsyncOperation())
        }
    }
    print("Actually executed $actualCount times, expected $n times")
}

fun someAsyncOperation(): CompletableFuture<Unit> {
    // return a future that is already completed
    return CompletableFuture.completedFuture(Unit)
}

// ======================================================================================================
// code copied from https://github.com/Kotlin/kotlin-coroutines/blob/master/examples/async.kt

fun <T> async(coroutine c: FutureController<T>.() -> Continuation<Unit>): CompletableFuture<T> {
    val controller = FutureController<T>()
    controller.c().resume(Unit)
    return controller.future
}

class FutureController<T> {
    val future = CompletableFuture<T>()

    suspend fun <V> await(f: CompletableFuture<V>, machine: Continuation<V>) {
        f.whenComplete { value, throwable ->
            if (throwable == null)
                machine.resume(value)
            else
                machine.resumeWithException(throwable)
        }
    }

    operator fun handleResult(value: T, c: Continuation<Nothing>) {
        future.complete(value)
    }

    operator fun handleException(t: Throwable, c: Continuation<Nothing>) {
        future.completeExceptionally(t)
    }
}