e: java.lang.IllegalStateException: class NewImport has duplicate serial name of property feedId, either in it or its parents.

@Serializable
sealed class FeedOperation(open val feedId: FeedId) {

    @Serializable
    data class NewImport(override val feedId: FeedId) : FeedOperation(feedId)

    @Serializable
    data class RedoImport(override val feedId: FeedId) : FeedOperation(feedId)

    @Serializable
    data class RemoveImported(override val feedId: FeedId) : FeedOperation(feedId)
}

abstract

open

@Serializable
sealed class FeedOperation(@Transient open val feedId: FeedId = null!!)

@Serializable
sealed class FeedOperation {
    abstract val feedId: FeedId

    @Serializable
    data class NewImport(override val feedId: FeedId) : FeedOperation()

    @Serializable
    data class RedoImport(override val feedId: FeedId) : FeedOperation()

    @Serializable
    data class RemoveImported(override val feedId: FeedId) : FeedOperation()
}

@Serializable
sealed class FeedOperation(abstract val feedId: FeedId)