Learning Concurrency in Kotlin

Unconfined

Because Unconfined doesn't care to enforce a specific thread or pool of threads, it first overrides isDispatchNeeded() to indicate that it isn't needed:

override fun isDispatchNeeded(context: CoroutineContext): Boolean = false

And it throws an exception if you actually try to dispatch something with it:

override fun dispatch(context: CoroutineContext, block: Runnable) {     throw UnsupportedOperationException() }