inline class SafeIndex(val rawIndex: Int) {
    val orNull: Int?
        get() = rawIndex.takeUnless { it < 0 }
}
inline fun SafeIndex.orElse(default: () -> Int): Int =
    if (rawIndex < 0) default() else rawIndex
inline fun <T> Iterable<T>.safeIndexOfFirst(predicate: (T) -> Bool) =
	SafeIndex(indexOf(predicate))

val n = completionProviders.safeIndexOfFirst { ... }
	.orElse { completionProviders.size }