https://discuss.kotlinlang.org/t/sealed-class-inheritance-and-constructors/2283/8 Found this, which I think answers my question

sealed class Message {
    abstract val id: Long
    abstract val type: String
    abstract val channel: String
}

data class Typing(override val id: Long, override val channel: String) : Message() {
    override val type = "typing"
}

That'll do okay, it's not as clean as I'd like, but it's good enough

Hi guys, is Unit considered Any? 😛

Imagine I have an extension signature like this:

fun <T, C : Any> Iterable<T>.convert(predicate: (T) -> C): List<C>

Why is this valid?

val list = ArrayList<String>()
        list.convert {

        }

My predicate should return Any, but it is returning Unit. Hence my initial question.

Unit

is subtype of

Any

I see. Isn't that weird? Also, how can I define a predicate that doesn't allow a Unit return

dont think you can exclude it

what even is the point of

.convert()

here

seems just like boneless

.map()

, which has the same “problem”

Its because T and C are bounded to

Any

, and

Unit

is an instance of

Any

.

Unit

isn’t quite the same as Java’s

void

, it actually is an object, so the implicitly returned

Unit

object can also be cast to

Any

. You’ll need to set up some kind of base class or interface that your predicate requires other than

Any

. Also, the naming might be a bit confusing, as a “predicate” is usually a function which returns a

Boolean

Don't mind the usefulnees of "convert". This was a mere example of something that I noticed today at work

But I understand now. Thanks guys 🙂

Compiles fine and crashes with a NullPointerException. Good job, compiler!

oof

surprised the compiler considers that an exhaustive return

I'm going to guess that's a contracts bug, it takes `let`'s

callsInPlace(block, InvocationKind.EXACTLY_ONCE)

a bit too literally.

Yup, doesn't compile in

1.2

.

is there terminology for a top level val vs a val in an object vs a val in a method

I guess the first two are "top level property" and "property"

what's the last one?

I'd say just a variable.

local property

Guys, one of my coworkers asked me about interesting snippet, do you know why this doesn't trigger compile error on Kotlin 1.3? It doesn't compile on 1.2.30 🙂

because of the

main

with no arguments?

what’s the error?

main is not a problem, you can call it anywhere, problem is in validate function

it has a case where is no return, when value is null

Isnt this the problem reported by @karelpeeters recently? https://youtrack.jetbrains.net/issue/KT-28061