Just tried K2 on Kore and I get errors on serialized fun interfaces :

@Serializable(RecipeType.Companion.RecipeTypeSerializer::class)
fun interface RecipeType {
	override fun toString(): String

	companion object {
		data object RecipeTypeSerializer : ToStringSerializer<RecipeType>() // serializer just using the `.toString()` method, deserialization isn't available
	}
}

object RecipeTypes {
	val BLASTING = RecipeType { "blasting" }
	val CAMPFIRE_COOKING = RecipeType { "campfire_cooking" }
	val CRAFTING_SHAPED = RecipeType { "crafting_shaped" }
    ...
}

The errors I get :

Interface '@Serializable(...) fun interface RecipeType : Any' does not have constructors.

On each line of

RecipeType { ... }

Is this issue known, and is there any YouTrack issue about that ?

cc @sandwwraith

This doesn't look like something I'm aware of. Do you mind creating a YT ticket with a detailed description?

Will do that tomorrow if I have time to !