A modern programming language that makes developers happier.

kotlinlang

Hello, World!  Hey, when doing sealed classes, the compiler complains that the types can only be subtypes of the sealed class.  Does that mean that the one example on the official doc is wrong?

```
data class Pagination(val pageIndex: PageIndex, val itemCount: Int = DEFAULT_ITEM_COUNT) {
    companion object {
        const val DEFAULT_ITEM_COUNT = 25
    }


    sealed class PageIndex {
        internal abstract val before: String?
        internal abstract val after: String?

    }

    object FirstPage : PageIndex() {
        override val before: String? = null
        override val after: String? = null
    }

    data class Before(private val elementId: String) : PageIndex() {
        override val before = elementId
        override val after: String? = null
    }

    data class After(private val elementId: String) : PageIndex() {
        override val before: String? = null
        override val after = elementId
    }
}
```

And the error is “This type is sealed so it can be inherited by only its own nested classes or objects”

You can only inherit from a sealed class with either a class nested inside the sealed class or a class in the same file of a _top level_ sealed class. Your `PageIndex` is not top level, so only classes nested inside `PageIndex` can inherit from it.

Oh.  So strange :slightly_smiling_face:  OK so if I move everything outside of `Pagination` it should work

it does work indeed!  I wonder why this restriction exists.  Anyway, many thanks :slightly_smiling_face: