Why use inline without lambdas

Question

I'm trying to understand how to use inline modifier correctly. I understand general case, when we inlining lambda to prevent excess allocation, as described in docs.

I was inspecting kotlin stdlib and found in _Strings.kt the following piece of code:

@kotlin.internal.InlineOnly
public inline fun CharSequence.elementAtOrNull(index: Int): Char? {
    return this.getOrNull(index)
}

What's the reasoning behind using inline here?

Answer 1

This particular function and a few others in kotlin-stdlib are marked as @InlineOnly so that they are not present in the actual stdlib class files and are only available for the Kotlin compiler to inline them. The goal that is achieved in this way is reducing the methods count in the artifacts, which matters for Android.

Apart from that, using inline functions without lambdas is useful for reifying type parameters.