List

List

val inputChar = ('A'..'Z') + ('a'..'z') + ('0'..'9') + charRange

You can't append any items to the list again

Kotlin because a List is immutable and yours gets initialized as an empty one, so it will stay empty.

Use a MutableList<Char> and simply add single Chars to it if you need it

SO | Kotlin list char

Mutable List

fun main(args: Array<String>) {
    var genList = mutableListOf<Char>()
    genList.add('a')
    genList.add('A')
    genList.add('B')
    genList.add('C')
    println(genList)
}