找出菜单快照里的bug

data class Menu(val items: List<String>)

class MenuBuilder {
    private val items = mutableListOf<String>()
    fun item(name: String) { items += name }
    fun build(): Menu = Menu(items)
}

fun main() {
    val builder = MenuBuilder()
    builder.item("home")
    val menu = builder.build()
    builder.item("admin")
    println(menu.items)
}