Scala 2.11 hangs

package model.stats

trait TimeUnit {
    val text: String
    val larger: TimeUnit
    val smaller: TimeUnit
}

object Second extends TimeUnit {
    override val text = "second"
    override val larger = Minute
    override val smaller = null
}

object Minute extends TimeUnit {
    override val text = "minute"
    override val larger = Hour
    override val smaller = Second
}

object Hour extends TimeUnit {
    override val text = "hour"
    override val larger = Day
    override val smaller = Minute
}

object Day extends TimeUnit {
    override val text = "day"
    override val larger = Month
    override val smaller = Hour
}

object Month extends TimeUnit {
    override val text = "month"
    override val larger = Year
    override val smaller = Day
}

object Year extends TimeUnit {
    override val text = "year"
    override val larger = null
    override val smaller = Month
}

object TimeUnit {
    def apply(string: String): TimeUnit = string match {
        case "second" => Second
        case "minute" => Minute
        case "hour" => Hour
        case "day" => Day
        case "month" => Month
    }
}