data class Parent(
  val defaultedValue: String = "default",
  val child: Child = Child(),
)

data class Child(
  val childValue1: String = "root",
  val childValue2: Int = 5,
  val childValue3: Boolean = true,
)

fun main() {
  
  fun thingThatTakesParent(parent: Parent): Unit = TODO()
  
  thingThatTakesParent(
    parent = (
      child = (
        childValue2 = 6,
      ),
    ),
  )
}