SortedSet#map

a.scala

scala> import scala.collection.immutable.SortedSet
import scala.collection.immutable.SortedSet

scala> case class Hoge(i: Int)
defined class Hoge

scala> SortedSet(1, 2, 3, 4, 5)
res0: scala.collection.immutable.SortedSet[Int] = TreeSet(1, 2, 3, 4, 5)

scala> SortedSet(1, 2, 3, 4, 5).map(Hoge.apply)
res1: scala.collection.immutable.Set[Hoge] = Set(Hoge(4), Hoge(1), Hoge(3), Hoge(5), Hoge(2))

scala> SortedSet(1, 2, 3, 4, 5).map(1+)
warning: there was one feature warning; re-run with -feature for details
res2: scala.collection.immutable.SortedSet[Int] = TreeSet(2, 3, 4, 5, 6)

scala> implicit val o: Ordering[Hoge] = Ordering.by(h => h.i)
o: Ordering[Hoge] = scala.math.Ordering$$anon$9@e27ba81

scala> SortedSet(1, 2, 3, 4, 5).map(Hoge.apply)
res3: scala.collection.immutable.SortedSet[Hoge] = TreeSet(Hoge(1), Hoge(2), Hoge(3), Hoge(4), Hoge(5))

scala/scala#6037