Shame that Swift is pretty much confined to iOS app development.

    protocol Weapon {}
    class Staff: Weapon {}
    class Sword: Weapon {}

    protocol Player {
       associatedtype T: Weapon
       var weapon: T  { get set } 
    }

    class Wizard: Player {
       var weapon = Staff()
    }

    class Warrior: Player {
       var weapon = Sword()
    }