HList-like Builder question mark ?

hbuilder.kt

fun main() {

    mock<WriteRound<Int, WriteRound<String, WriteRound<Boolean, Terminate>>>>()
        .set(3)
        .set("sss")
        .set(true)

}

fun <T> mock(): T = TODO()

sealed class WriteBuilder

object Terminate : WriteBuilder()
class WriteRound<V, N : WriteBuilder> : WriteBuilder()

object Query

fun <V> WriteRound<V, Terminate>.set(v: V): Query { TODO() }

fun <V, T : WriteRound<*, *>, W : WriteRound<V, T>> W.set(v: V): T {
    TODO()
}