Scala convert Iterable or collection.Seq to collection.immutable.Seq

Use the to method to convert between arbitrary collection types in Scala 2.10:

scala> Array(1, 2, 3).toSeq
res0: Seq[Int] = WrappedArray(1, 2, 3)

scala> Array(1, 2, 3).to[collection.immutable.Seq]
res1: scala.collection.immutable.Seq[Int] = Vector(1, 2, 3)