Is it ok this code is valid in Kotlin? Class Base doesn't explicitly tell that fun buz is overriden.

interface MyInt {
    fun boo()
    fun buz()
}

open class Base {
    fun buz() {
        //
    }
}

class Impl: MyInt, Base() {
    override fun boo() {
        //
    }
}

Why should Base tell that? Base doesn't know about MyInt ?

Because in this case

Base

class implicitly overrides

fun buz

. There is no

override fun buz

in

class Imp

This case has come up previously on this slack, and I agree it's a bit weird. You can see it in action in the playground: https://play.kotlinlang.org/#eyJ2ZXJzaW9uIjoiMS45LjIwIiwicGxhdGZvcm0iOiJqYXZhIiwiYXJncy[…]B9XG59XG5cbmZ1biBtYWluKCkge1xuICAgIEltcGwoKS5idXooKVxufSJ9

Do you recall how it's explained, or do you have a link/hint how to search for it? It's definitely surprising and I'd love to know more details

It was a long time ago, so I don't think it will show up in this slack's history… I don't remember if there was any explanation, other than people being surprised. If you really want to learn more about it, I think it's worth creating an issue (https://kotl.in/issue) to ask the team directly