I just found something a bit puzzling in the langu...

# announcements

[Pere Casafont]

I just found something a bit puzzling in the language (thread)

[Pere Casafont]

https://play.kotlinlang.org/#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

[Pere Casafont]

Isn't the compiler being a bit too smart there? Shouldn't this be an error?

[Pere Casafont]

weirder:

object A {
    val foo: String
    val bar: String
    
    init {
        println(1)
        foo = "hi"
        println(2)
        bar = B.baz
        println(3)
    }
}

object B {
    val baz: String
    val mor: String
    
    init {
        println(4)
        baz = A.foo
        println(5)
        mor = A.bar
        println(6)
    }
}

fun main() {
    println(B.mor)
}

[karelpeeters]

It's not actually being smart, it's easy to get runtime exceptions when doing things like this. It just happens to work out here.

[egorand]

FWIW I don't think it has anything to do with the language/compiler, it's how JVM loads classes and executes initializers

[karelpeeters]

Looks like they put in some effort to make it work the same way on JS though.

[egorand]

But does play.kotlinlang.org compile into JS and run it in the browser, or does it send code to a backend that compiles and runs it on JVM?

[karelpeeters]

Well you can choose between JVM and JS in the gear icon on the right.

[Hullaballoonatic]

object instantiation is lazy

[Hullaballoonatic]

that's the answer to your puzzle