A modern programming language that makes developers happier.

kotlinlang

```sealed class IssueStatus(
    val transitionsTo: List&lt;IssueStatus&gt;
) {
    constructor(vararg transitionsTo: IssueStatus) : this(transitionsTo.toList())

    data object Closed : IssueStatus()
    data object Acknowledged : IssueStatus(New, Closed)
    data object New : IssueStatus(Acknowledged, Closed)
}```
How would you solve this issue?
References inside `transitionsTo` are null, as they're referencing before it's been declared

```sealed class IssueStatus {
    abstract val transitionsTo: List<IssueStatus>

    data object Closed : IssueStatus() {
        override val transitionsTo: List<IssueStatus>
            get() = emptyList()
    }

    data object Acknowledged : IssueStatus() {
        override val transitionsTo: List<IssueStatus>
            get() = listOf(New, Closed)
    }

    data object New : IssueStatus() {
        override val transitionsTo: List<IssueStatus>
            get() = listOf(Acknowledged, Closed)
    }
}```

sure would be nice if <https://youtrack.jetbrains.com/issue/KT-8970> prevented you from getting into this state though

By the way, when converting a `vararg` parameter, you might as well use `asList()` instead of `toList()` because the array instance is one the compiler has auto-generated, and not one that you can change yourself, therefore there's no need to guard against changes by copying the array.

(there is still a need to guard against changes if it could potentially be called by Java, although that's not the case here)