scala> val m = Map(1 -> 2) m: scala.collection.immutable.Map[Int,Int] = Map(1 -> 2) scala> m.map{case (a, b) => (a+ 1, a+2, a+3)} res42: scala.colle
Whilst Ben's is the correct answer, an alternative would have been to use a type alias:
type I3 = (Int, Int, Int) m.map{case (a, b) => (a+ 1, a+2, a+3)}(breakOut[Map[_,_], I3, List[I3]])