A Kotlin expression function to get a required value from a map alternatively throw an IllegalArgumentException like require

kotlin-get-required.kt

inline fun <K, V> Map<K, V>.getRequired(key: K): V = this.get(key) ?: throw IllegalArgumentException("$key not found in $keys")

fun main() {
    val aMap = mapOf("a" to 1, "b" to 2, "c" to 3)

	val anA = aMap.get("a") ?: error("a not found in ${aMap.keys}")
	// while line reads easier
	val guaranteedB = aMap.getRequired("b")
	
    
    println("a=$anA")
	println("b=$guaranteedB")
	// should throw IllegalArgumentException: d not found in [a, b, c]
	val aD = aMap.getRequired("d")
    println("d=$aD")
}