I'm trying to define an inner type that has one, and exactly one, instance per outer instance (so not an

object

), which cannot be constructed elsewhere without reflection, but I can't seem to get it any tighter than

inner

. Making it

private

will not allow to me create the one instance:

inner class TheLock internal constructor()
    private val theLockInstance = TheLock()

    inline fun <T> synced(block: (TheLock) -> T) =
            synchronized(this) {
                block(theLockInstance)
            }

I asked about this a while ago: https://kotlinlang.slack.com/archives/C0922A726/p1518037873000134