Literals.kt

typealias UserAddressBuilderLambda = () -> UserAddress  // 1
class UserAddressBuilder(
    addressInit: UserAddressBuilder.() -> Unit   // 2
) : UserAddressBuilderLambda {
    init {
        this.addressInit()   // 3
    }

    var userCity: String = ""
    var userCountry: String = ""

    override fun invoke(): UserAddress {  // 4
        return object : UserAddress {
            override val city: String = userCity
            override val country: String = userCountry
        }
    }
}