Sample.kt

sealed class WidgetType {
    data class SlideBar(val min: Int, val max: Int, val step: Int) : WidgetType()
    data class Radio(val items: List<RadioItem>) : WidgetType()
}

data class RadioItem(
    val name: String,
    val value: Int
)

enum class Widget(val widgetType: WidgetType) {
    FOO(WidgetType.SlideBar(0, 9, 3)),
    Bar(WidgetType.SlideBar(0, 100, 3)),
    XXX(WidgetType.Radio(
        listOf(RadioItem("aaa", 0), RadioItem("bbb", 1)))
    )
}

fun main() {
    val widgets = TODO()
    val widgetType = Widget.FOO.widgetType
    when (widgetType) {
        is WidgetType.Radio -> {
            widgetType.items
        }
        is WidgetType.SlideBar -> {
            widgetType.min
        }
    }
}