private class DefaultProperty<T> internal constructor(private val default: () -> T) : ReadWriteProperty<Any?, T> {
    private var inner: T? = null

    override fun getValue(thisRef: Any?, property: KProperty<*>): T = inner ?: default()

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        inner = value
    }

}

private inline fun <reified T> defaultProperty(noinline default: () -> T): DefaultProperty<T> = DefaultProperty(default)

class Test {
	val foo: String? by defaultProperty { null }
}