Scala insertion sort implementation

InsertionSort.scala

import scala.annotation.tailrec

object sortings {
  def insertionSort(ar: Array[Int]): Array[Int] = {
    @tailrec
    def loop(i: Int, key: Int): Int =
      if (i < 0 || ar(i) < key) i + 1
      else {
        ar(i + 1) = ar(i)
        loop(i - 1, key)
      }
    for (i <- ar.indices.drop(1)) {
      val key = ar(i)
      val j = loop(i - 1, key)
      ar(j) = key
    }
    ar
  }
}