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I'd like to have a trait that can a) be mixed into any class with a particular method, and b) can call super. Something like this: // A and B are from a library that I don't control. No changes allowed here. class A { def stuff = "a stuff" } class B { def stuff = "b stuff" } // My code starts here type HasStuffMethod = { def stuff: String } // Note that this doesn't compile - gets: // class type required but AnyRef{def stuff: String} found trait ImplementsStuff extends HasStuffMethod { override def stuff = "trait + " + super.stuff } val a = new A with ImplementsStuff assert(a.stuff == "trait + a stuff") val b = new B with ImplementsStuff assert(b.stuff == "trait + b stuff") Is there any way to do this? Note that I don't control A and B; they're coming from another library that I can't modify. [Edit - added after seeing answers] Is there a way to call the original method in something like this? trait ImplementsStuff { this: HasStuffMethod => abstract override def stuff = "foo" + "how do I call the original method here?" } This isn't useful, since when you mix it into something it gives: error: overriding method stuff in class A of type => java.lang.String; method stuff in trait ImplementsStuff of type => java.lang.String cannot override a concrete member without a third member that's overridden by both (this rule is designed to prevent ``accidental overrides'') But it's no accident; yes, I really do want you to step all over that existing method. And then let me call it, too.

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