looks like someone fixed it, the line is now:

.filter({ el-> cache.merge(el, 1, { a, b-> a + b })!! <= maxOccurrences })

and i see no generated warnings

Many katas from years ago are overranked.

Sorry, how is this 6 kyu? This is 7 or 8. How is that kata the same difficulty as this?

Ditto! Did you resolve this?

I agree. I've been using Codewars to learn Kotlin and this has blocked me way more than the actual solution :)

Kotlin version is not working. My code works, all random tests pass every time, but I get this output which prevents it from being accepted:

fixture.kt:49:51: warning: unchecked cast: HashMap<Int, Int> to Map<Int, Int>
                            .filter({ el-> (cache as java.util.Map<Int, Int>)
                                                  ^
fixture.kt:49:54: warning: this class shouldn't be used in Kotlin. Use kotlin.collections.Map or kotlin.collections.MutableMap instead.
                            .filter({ el-> (cache as java.util.Map<Int, Int>)
                                                     ^

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