Support situation when argument for serializer<T>() function has SerialInfo annotations.

Because SerializationJvmIrIntrinsicSupport does not instantiate annotations yet,
this info could be lost. As a workaround, it is possible to call Companion.serializer()
functions instead of direct serializer instantiation, as they are plugin-generated
and correctly handle annotations.

Note that for some cases (enums & interfaces) this WA is not enough, so additional work
is needed later.

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2179

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

@@ -49,6 +49,7 @@ import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializersClassIds.
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializersClassIds.referenceArraySerializerId
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializersClassIds.sealedSerializerId
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SpecialBuiltins
+import org.jetbrains.kotlinx.serialization.compiler.resolve.annotationsWithArguments
 import org.jetbrains.kotlinx.serialization.compiler.resolve.getClassFromSerializationPackage
 import org.jetbrains.org.objectweb.asm.Opcodes
 import org.jetbrains.org.objectweb.asm.Type
@@ -381,8 +382,8 @@ class SerializationJvmIrIntrinsicSupport(val jvmBackendContext: JvmBackendContex
             val descriptor = StringBuilder("(${serializersModuleType.descriptor}${AsmTypes.K_CLASS_TYPE.descriptor}")
             // Generic args (if present)
             if (argSerializers.isNotEmpty()) {
-                fillArray(kSerializerType, argSerializers) { _, serializer ->
+                fillArray(kSerializerType, argSerializers) { _, (type, _) ->
-                    instantiate(serializer, null)
+                    generateSerializerForType(type, this, intrinsicType)
                 }
                 descriptor.append(kSerializerArrayType.descriptor)
             }
@@ -485,8 +486,8 @@ class SerializationJvmIrIntrinsicSupport(val jvmBackendContext: JvmBackendContex
                             aconst(null)
                         }
                         signature.append(kSerializerType.descriptor)
-                        fillArray(kSerializerType, argSerializers) { _, serializer ->
+                        fillArray(kSerializerType, argSerializers) { _, (type, _) ->
-                            instantiate(serializer, null)
+                            generateSerializerForType(type, this, intrinsicType)
                         }
                         signature.append(kSerializerArrayType.descriptor)
                     }
@@ -498,7 +499,8 @@ class SerializationJvmIrIntrinsicSupport(val jvmBackendContext: JvmBackendContex
                     AsmUtil.wrapJavaClassIntoKClass(this)
                     signature.append(AsmTypes.K_CLASS_TYPE.descriptor)
                     // Reference array serializer still needs serializer for its argument type
-                    instantiate(argSerializers[0], signature)
+                    generateSerializerForType(argSerializers[0].first, this, intrinsicType)
+                    signature.append(kSerializerType.descriptor)
                 }
 
                 sealedSerializerId -> {
@@ -550,7 +552,10 @@ class SerializationJvmIrIntrinsicSupport(val jvmBackendContext: JvmBackendContex
                     signature.append("Ljava/lang/Object;")
                 }
                 // all serializers get arguments with serializers of their generic types
-                else -> argSerializers.forEach { instantiate(it, signature) }
+                else -> argSerializers.forEach { (type, _) ->
+                    generateSerializerForType(type, this, intrinsicType)
+                    signature.append(kSerializerType.descriptor)
+                }
             }
             signature.append(")V")
             // invoke constructor

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

@@ -0,0 +1,40 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// TARGET_BACKEND: JVM_IR
+
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.internal.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.modules.*
+import kotlin.test.*
+
+@Serializable
+@JsonClassDiscriminator("sealed")
+sealed class Sealed
+
+@Serializable
+@JsonClassDiscriminator("abstract")
+abstract class Abstract
+
+@Serializable
+@JsonClassDiscriminator("object")
+object Object
+
+fun test(descriptor: SerialDescriptor, value: String, name: String = descriptor.serialName) {
+    val anno = descriptor.annotations.filterIsInstance<JsonClassDiscriminator>().singleOrNull()
+    requireNotNull(anno) { "Annotation value not found for $name" }
+    assertEquals(anno.discriminator, value, "Annotation value incorrect for $name")
+}
+
+fun box(): String {
+    test(serializer<Sealed>().descriptor, "sealed")
+    test(serializer<Abstract>().descriptor, "abstract")
+    test(serializer<Object>().descriptor, "object")
+    test(serializer<List<Sealed>>().descriptor.getElementDescriptor(0), "sealed", "List<Sealed>")
+    test(serializer<List<Abstract>>().descriptor.getElementDescriptor(0), "abstract", "List<Abstract>")
+    test(serializer<List<Object>>().descriptor.getElementDescriptor(0), "object", "List<Object>")
+    test(serializer<Array<Sealed>>().descriptor.getElementDescriptor(0), "sealed", "Array<Sealed>")
+    return "OK"
+}

plugins/kotlinx-serialization/testData/codegen/Intrinsics.asm.ir.txt

@@ -127,7 +127,8 @@ public final class IntrinsicsKt : java/lang/Object {
           GETSTATIC (Box, Companion, LBox$Companion;)
           NEW (kotlinx/serialization/internal/ArrayListSerializer)
           DUP
-          GETSTATIC (Simple$$serializer, INSTANCE, LSimple$$serializer;)
+          GETSTATIC (Simple, Companion, LSimple$Companion;)
+          INVOKEVIRTUAL (Simple$Companion, serializer, ()Lkotlinx/serialization/KSerializer;)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
           INVOKEVIRTUAL (Box$Companion, serializer, (Lkotlinx/serialization/KSerializer;)Lkotlinx/serialization/KSerializer;)
           POP
@@ -142,7 +143,8 @@ public final class IntrinsicsKt : java/lang/Object {
           GETSTATIC (Box, Companion, LBox$Companion;)
           NEW (kotlinx/serialization/internal/ArrayListSerializer)
           DUP
-          GETSTATIC (Simple$$serializer, INSTANCE, LSimple$$serializer;)
+          GETSTATIC (Simple, Companion, LSimple$Companion;)
+          INVOKEVIRTUAL (Simple$Companion, serializer, ()Lkotlinx/serialization/KSerializer;)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
           INVOKEVIRTUAL (Box$Companion, serializer, (Lkotlinx/serialization/KSerializer;)Lkotlinx/serialization/KSerializer;)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
@@ -167,10 +169,9 @@ public final class IntrinsicsKt : java/lang/Object {
           DUP
           NEW (kotlinx/serialization/internal/ArrayListSerializer)
           DUP
-          NEW (Box$$serializer)
+          GETSTATIC (Box, Companion, LBox$Companion;)
-          DUP
           GETSTATIC (kotlinx/serialization/internal/IntSerializer, INSTANCE, Lkotlinx/serialization/internal/IntSerializer;)
-          INVOKESPECIAL (Box$$serializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
+          INVOKEVIRTUAL (Box$Companion, serializer, (Lkotlinx/serialization/KSerializer;)Lkotlinx/serialization/KSerializer;)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
         LABEL (L21)

plugins/kotlinx-serialization/testData/codegen/IntrinsicsAdvanced.asm.ir.txt

@@ -50,7 +50,8 @@ public final class IntrinsicsAdvancedKt : java/lang/Object {
           POP
           NEW (kotlinx/serialization/internal/ArrayListSerializer)
           DUP
-          GETSTATIC (Simple$$serializer, INSTANCE, LSimple$$serializer;)
+          GETSTATIC (Simple, Companion, LSimple$Companion;)
+          INVOKEVIRTUAL (Simple$Companion, serializer, ()Lkotlinx/serialization/KSerializer;)
           INVOKESPECIAL (kotlinx/serialization/internal/ArrayListSerializer, <init>, (Lkotlinx/serialization/KSerializer;)V)
           POP
         LABEL (L3)
@@ -109,7 +110,8 @@ public final class IntrinsicsAdvancedKt : java/lang/Object {
           ANEWARRAY (kotlinx/serialization/KSerializer)
           DUP
           ICONST_0
-          GETSTATIC (Simple$$serializer, INSTANCE, LSimple$$serializer;)
+          GETSTATIC (Simple, Companion, LSimple$Companion;)
+          INVOKEVIRTUAL (Simple$Companion, serializer, ()Lkotlinx/serialization/KSerializer;)
           AASTORE
           INVOKESTATIC (kotlinx/serialization/SerializersKt, noCompiledSerializer, (Lkotlinx/serialization/modules/SerializersModule;Lkotlin/reflect/KClass;[Lkotlinx/serialization/KSerializer;)Lkotlinx/serialization/KSerializer;)
         LABEL (L15)

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

@@ -111,6 +111,12 @@ public class SerializationFirBlackBoxTestGenerated extends AbstractSerialization
             runTest("plugins/kotlinx-serialization/testData/boxIr/inlineClasses.kt");
         }
 
+        @Test
+        @TestMetadata("intrinsicAnnotations.kt")
+        public void testIntrinsicAnnotations() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/boxIr/intrinsicAnnotations.kt");
+        }
+
         @Test
         @TestMetadata("intrinsicsBox.kt")
         public void testIntrinsicsBox() throws Exception {

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

@@ -109,6 +109,12 @@ public class SerializationIrBoxTestGenerated extends AbstractSerializationIrBoxT
         runTest("plugins/kotlinx-serialization/testData/boxIr/inlineClasses.kt");
     }
 
+    @Test
+    @TestMetadata("intrinsicAnnotations.kt")
+    public void testIntrinsicAnnotations() throws Exception {
+        runTest("plugins/kotlinx-serialization/testData/boxIr/intrinsicAnnotations.kt");
+    }
+
     @Test
     @TestMetadata("intrinsicsBox.kt")
     public void testIntrinsicsBox() throws Exception {