Errata on chapter 4

There is a mistake in this chapter where the reader is asked to add a class to the same stack.kt file where the inference is… this is fine except the implementation code is wrong:
class Stack() {
private val storage = arrayListOf()

it should be:
class StackImpl : Stack {
private val storage = arrayListOf()

Thank you for sharing your implementation @arrmixer!

@mateisuica Can you please help with this when you get a chance? Thank you - much appreciated! :]