Puzzling hang in runBlocking

[elizarov]

From @konrad-kaminski

This code hangs, but does not hang without invokeOnCompletion:

fun main() {
    runBlocking {
        val job = GlobalScope.launch {  }
        job.invokeOnCompletion {  }
    }
}

Initial investigation shows that it is timing-depended, e.g. adding println statements inside runBlocking before } affects whether it hangs or not, too.

[qwwdfsad]

Single-threaded reproducer:

runBlocking {
  coroutineContext[Job]!!.invokeOnCompletion {  }
}