Is there a way to convey the fact that while incom...

# codereview

[Alex Kuznetsov]

Is there a way to convey the fact that while incoming T is nullable, it is not nullable in the outcome of the following:

fun<T> List<T>.indexedNotNull(): List<Pair<Int, T>> = this.mapIndexedNotNull { index, t -> 
    t?.let{ index to t }
}

[Joffrey]

You can use the notation T & Any, it's the only denotable intersection type for now, but that's the one you need so you're lucky :)

[ephemient]

you could do that, but

fun <T: Any> List<T?>.indexedNotNull(): List<Pair<Int, T>>

represents that fine (in the same way that .filterNotNull() does)

[ephemient]

come to think of it, the built-in .withIndex() is lazy, which you could also replicate pretty easily

fun <T: Any> Iterable<T?>.indexedNotNull(): Iterable<IndexedValue<T>> = Iterable {
    iterator {
        forEachIndexed { index, value ->
            if (value != null) yield(IndexedValue(index, value))
        }
    }
}

[Alex Kuznetsov]

TIL about forEachIndexed