Handle @Serializable classes that implement interfaces by delegation

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

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2157

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -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"
+}

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirBlackBoxTestGenerated.java

@@ -57,6 +57,12 @@ public class SerializationFirBlackBoxTestGenerated extends AbstractSerialization
             runTest("plugins/kotlinx-serialization/testData/boxIr/contextualFallback.kt");
         }
 
+        @Test
+        @TestMetadata("delegatedInterface.kt")
+        public void testDelegatedInterface() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/boxIr/delegatedInterface.kt");
+        }
+
         @Test
         @TestMetadata("enumsAreCached.kt")
         public void testEnumsAreCached() throws Exception {

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java

@@ -55,6 +55,12 @@ public class SerializationIrBoxTestGenerated extends AbstractSerializationIrBoxT
         runTest("plugins/kotlinx-serialization/testData/boxIr/contextualFallback.kt");
     }
 
+    @Test
+    @TestMetadata("delegatedInterface.kt")
+    public void testDelegatedInterface() throws Exception {
+        runTest("plugins/kotlinx-serialization/testData/boxIr/delegatedInterface.kt");
+    }
+
     @Test
     @TestMetadata("enumsAreCached.kt")
     public void testEnumsAreCached() throws Exception {