Is there an idiomatic way to create generic mutable list of nulls? I did in the following way:

private fun <T> mutableListOfNulls(size: Int) = (0..<size).map<Int, T?> { null }.toMutableList()

but I guess there should be simpler solution

There is MutableList:

val list = MutableList<YourType?>(size) { null }

yay, thanks!