[Bug] Hessian2 breaks Kotlin object singleton identity, silently selecting the wrong when branch #16489

plugins {
    kotlin("jvm") version "2.4.20"
    application
}
repositories { mavenCentral() }
dependencies {
    implementation("org.apache.dubbo:dubbo:3.3.6")
    implementation("io.netty:netty-all:4.1.118.Final")
    implementation("org.javassist:javassist:3.30.2-GA")
    implementation("org.slf4j:slf4j-simple:2.0.13")
}
kotlin { jvmToolchain(21) }
application { mainClass = "repro.MainKt" }

package repro

import java.io.Serializable
import org.apache.dubbo.config.*
import org.apache.dubbo.config.bootstrap.DubboBootstrap

sealed interface Reply : Serializable

data class Found(val text: String) : Reply

object NotFoundObject : Reply          // equals() is inherited identity comparison
data object NotFoundDataObject : Reply // compiler generates equals()
enum class NotFoundEnum : Reply { INSTANCE }

interface ReplyService {
    fun roundTrip(reply: Reply): Reply // returns its argument unchanged
}

class ReplyServiceImpl : ReplyService {
    override fun roundTrip(reply: Reply): Reply = reply
}

/** The dispatch a consumer actually writes. */
private fun describe(reply: Reply): String = when (reply) {
    NotFoundObject -> "matched NotFoundObject"
    NotFoundDataObject -> "matched NotFoundDataObject"
    NotFoundEnum.INSTANCE -> "matched NotFoundEnum.INSTANCE"
    is Found -> "matched Found(${reply.text})"
    else -> ">>> FELL THROUGH TO else <<<"
}

private fun report(label: String, sent: Reply, back: Reply) =
    println("%-12s | ===:%-5s | ==:%-5s | %s".format(label, back === sent, back == sent, describe(back)))

fun main() {
    DubboBootstrap.getInstance()
        .application(ApplicationConfig("repro"))
        .registry(RegistryConfig("N/A"))
        .protocol(ProtocolConfig("dubbo", 20881))
        .service(ServiceConfig<ReplyService>().apply {
            setInterface(ReplyService::class.java)
            setRef(ReplyServiceImpl())
        })
        .start()

    val svc = ReferenceConfig<ReplyService>().apply {
        setInterface(ReplyService::class.java)
        url = "dubbo://127.0.0.1:20881"
    }.get()

    report("object", NotFoundObject, svc.roundTrip(NotFoundObject))
    report("data object", NotFoundDataObject, svc.roundTrip(NotFoundDataObject))
    report("enum", NotFoundEnum.INSTANCE, svc.roundTrip(NotFoundEnum.INSTANCE))
    report("data class", Found("hi"), svc.roundTrip(Found("hi")))

    DubboBootstrap.getInstance().destroy()
}