typelevelcrap.scala

scala> trait DayOfWeek; trait Sun extends DayOfWeek; trait Mon extends DayOfWeek // etc
defined trait DayOfWeek
defined trait Sun
defined trait Mon

scala> trait Weekend[D <: DayOfWeek]; implicit object SunInWeekend extends Weekend[Sun] // define one for Sat too
defined trait Weekend
defined module SunInWeekend

scala> def goSkiing[D <: DayOfWeek : Weekend] = println("whee")
goSkiing: [D <: DayOfWeek](implicit evidence$1: Weekend[D])Unit

scala> goSkiing[Sun]
whee

scala> goSkiing[Mon]
<console>:38: error: could not find implicit value for evidence parameter of type Weekend[Mon]
              goSkiing[Mon]
                      ^