Kotlin/JS generated code references undefined variable when @Serializable

I have a simple class that I’m trying to make Serializable, but even just adding @Serializable on the class causes the generated JS code to throw an exception.

Here’s the class:

@Serializable
class MyClass(val questions: List<String>, val finaleQuestions: List<String>){

    val rounds: List<String>

    init {
        rounds = mutableListOf<String>().also { mutableRounds ->
            questions.forEach {
                mutableRounds.add(it)
            }
        }
    }
}

var myClass = MyClass(listOf("a"), listOf("b"))

Here’s the code generated when @Serializable is present:

function MyClass(questions, finaleQuestions) {
    MyClass$Companion_getInstance();
    this.questions = questions;
    this.finaleQuestions = finaleQuestions;
    this.currentRoundCounter = 0;
    this.rounds = null;
    var $receiver = ArrayList_init();
    var tmp$;
    tmp$ = this$MyClass.questions.iterator(); // <-- throws "this$MyClass is not defined"
    while (tmp$.hasNext()) {
      var element = tmp$.next();
      closure$mutableRounds.add_11rb$(element); //<-- this is also different btw
    }
    this.rounds = $receiver;
  } 

Code generated without @Serializable (works):

function MyClass(questions, finaleQuestions) {
    this.questions = questions;
    this.finaleQuestions = finaleQuestions;
    this.rounds = null;
    var $receiver = ArrayList_init();
    var tmp$;
    tmp$ = this.questions.iterator(); // <-- difference here
    while (tmp$.hasNext()) {
      var element = tmp$.next();
      $receiver.add_11rb$(element);
    }
    this.rounds = $receiver;
  }

This is using id 'kotlin2js' version '1.3.0-rc-190' and compile "org.jetbrains.kotlinx:kotlinx-serialization-runtime-js:0.8.3-rc13"

[mschirmacher]

Stumbled across this bug today, too. It took me half the day to find out that this code breaks the js-code:

init {
        children.forEach { it.parent = this}
    }

While this code doesn’t

init {
        for (child in children) {
            child.parent = this
        }
    }

This is really annoying 😦

[sandwwraith]

It should be fixed in the IR in recent Kotlin versions (legacy compiler still affected). If problem happens in IR, please reopen