Kotlin intersect extension by selector

IntersectBy.kt

/**
 * Returns a set containing all elements with keys returned by the given [selector] function
 * that are both contained in this collection and the specified collection.
 *
 * The returned set preserves the element iteration order of the original collection.
 */
inline fun <T, K> Iterable<T>.intersectBy(other: Iterable<K>, selector: (T) -> K): Set<T> {
    val list = ArrayList<T>()
    for (e in this.toSet()) {
        val key = selector(e)
        if (other.contains(key))
            list.add(e)
    }
    return list.toSet()
}

Usage.kt

fun main() {
  val list1 = listOf(Pair(1, "b"), Pair(2, "r"), Pair(3, "o"), Pair(4, "k"), Pair(5, "e"), Pair(6, "n"))
  val list2 = listOf(1, 5)
  val result = list1.intersectBy(list2) { it.first }
  // result = [ Pair(1, "b"), Pair(5,"e") ]
}