Handle @serializable classes that implement interfaces by delegation

by filtering out delegated properties that end up in irClass.properties() list

Fixes Kotlin/kotlinx.serialization#2157

(cherry picked from commit dc0cd61)

plugins/kotlinx-serialization/kotlinx-serialization.backend/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/IrSerializableProperties.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlinx.serialization.compiler.backend.ir
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrDeclarationOrigin
 import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.types.IrSimpleType
 import org.jetbrains.kotlin.ir.util.*
@@ -78,7 +79,7 @@ internal fun serializablePropertiesForIrBackend(
 
     val (primaryCtorSerializableProps, bodySerializableProps) = properties
         .asSequence()
-        .filter { !it.isFakeOverride && !it.isDelegated }
+        .filter { !it.isFakeOverride && !it.isDelegated && it.origin != IrDeclarationOrigin.DELEGATED_MEMBER }
         .filter(::isPropSerializable)
         .map {
             val isConstructorParameterWithDefault = primaryParamsAsProps[it] ?: false

plugins/kotlinx-serialization/testData/boxIr/delegatedInterface.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JVM_IR
+
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+import kotlinx.serialization.json.*
+
+@Serializable()
+class Dto(
+    val data: Map<Int, Int>
+) : Map<Int, Int> by data
+
+fun box(): String {
+    val dto = Dto(mapOf(1 to 2))
+    val s = Json.encodeToString(dto)
+    if (s != """{"data":{"1":2}}""") return s
+    val d = Json.decodeFromString<Dto>(s)
+    if (d.size != 1) return "Delegation to Map failed"
+    if (d.data != dto.data) return "Equals failed ${d.data}"
+    return "OK"
+}