Yeah, i actually did same thing with stacktraces

private val checkPoints: MutableSet<String> = HashSet()

fun once(action: () -> Unit) {
    val stackTrace = Throwable().stackTrace[1]
    val key = "${stackTrace.fileName}_${stackTrace.methodName}_${stackTrace.lineNumber}"
    if (!checkPoints.contains(key)) {
        checkPoints.add(key)
        action()
    }
}

fun main() {
    repeat(100) {
        once { print("Say hi!") }
    }
}

Tiny suggestion:

!checkPoints.contains(key)

is

key !in  checkPoints

Never check before adding a value, that's doing double work,

add

returns a boolean https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-mutable-set/add.html.

if (checkPoints.add(key)) {
    action()
}

not that I'd recommend using it anywhere except for debug stuff, but

Thread.currentThread().stackTrace

can give you current stacktrace without creation a Throwable