Remove module-wide ObsoleteDescriptorApi opt-in

and remove access to .descriptor whenever possible

plugins/kotlin-serialization/kotlin-serialization-compiler/build.gradle.kts

@@ -60,7 +60,6 @@ sourceSets {
 
 tasks.withType<org.jetbrains.kotlin.gradle.dsl.KotlinCompile<*>> {
     kotlinOptions {
-        freeCompilerArgs += "-opt-in=org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI"
         freeCompilerArgs += "-opt-in=org.jetbrains.kotlin.compiler.plugin.ExperimentalCompilerApi"
     }
 }

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

@@ -11,7 +11,6 @@ import org.jetbrains.kotlin.backend.jvm.ir.fileParent
 import org.jetbrains.kotlin.backend.jvm.ir.representativeUpperBound
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.descriptors.isSealed
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrFunction
@@ -39,19 +38,26 @@ import org.jetbrains.kotlinx.serialization.compiler.backend.jvm.*
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 
-abstract class BaseIrGenerator(private val currentClass: IrClass, final override val compilerContext: SerializationPluginContext): IrBuilderWithPluginContext {
+abstract class BaseIrGenerator(private val currentClass: IrClass, final override val compilerContext: SerializationPluginContext) :
+    IrBuilderWithPluginContext {
 
-    private val throwMissedFieldExceptionFunc
-        = compilerContext.referenceFunctions(CallableId(SerializationPackages.internalPackageFqName, SerialEntityNames.SINGLE_MASK_FIELD_MISSING_FUNC_NAME)).singleOrNull()
+    private val throwMissedFieldExceptionFunc = compilerContext.referenceFunctions(
+        CallableId(
+            SerializationPackages.internalPackageFqName,
+            SerialEntityNames.SINGLE_MASK_FIELD_MISSING_FUNC_NAME
+        )
+    ).singleOrNull()
 
-    private val throwMissedFieldExceptionArrayFunc
-        = compilerContext.referenceFunctions(CallableId(SerializationPackages.internalPackageFqName, SerialEntityNames.ARRAY_MASK_FIELD_MISSING_FUNC_NAME)).singleOrNull()
+    private val throwMissedFieldExceptionArrayFunc = compilerContext.referenceFunctions(
+        CallableId(
+            SerializationPackages.internalPackageFqName,
+            SerialEntityNames.ARRAY_MASK_FIELD_MISSING_FUNC_NAME
+        )
+    ).singleOrNull()
 
-    private val enumSerializerFactoryFunc
-        = compilerContext.enumSerializerFactoryFunc
+    private val enumSerializerFactoryFunc = compilerContext.enumSerializerFactoryFunc
 
-    private val markedEnumSerializerFactoryFunc
-        = compilerContext.markedEnumSerializerFactoryFunc
+    private val markedEnumSerializerFactoryFunc = compilerContext.markedEnumSerializerFactoryFunc
 
     fun useFieldMissingOptimization(): Boolean {
         return throwMissedFieldExceptionFunc != null && throwMissedFieldExceptionArrayFunc != null
@@ -250,7 +256,7 @@ abstract class BaseIrGenerator(private val currentClass: IrClass, final override
             genericGetter
         )
         val (functionToCall, args: List<IrExpression>) = if (innerSerial != null) whenHaveSerializer(innerSerial, sti) else whenDoNot(sti)
-        val typeArgs = if (functionToCall.descriptor.typeParameters.isNotEmpty()) listOf(property.type) else listOf()
+        val typeArgs = if (functionToCall.owner.typeParameters.isNotEmpty()) listOf(property.type) else listOf()
         return irInvoke(encoder, functionToCall, typeArguments = typeArgs, valueArguments = args, returnTypeHint = returnTypeHint)
     }
 
@@ -267,7 +273,7 @@ abstract class BaseIrGenerator(private val currentClass: IrClass, final override
 
         val adjustedArgs: List<IrExpression> =
             // if typeArgs.size == args.size then the serializer is custom - we need to use the actual serializers from the arguments
-            if ((typeArgs.size != args.size) && (baseClass.descriptor.isSealed() || baseClass.descriptor.modality == Modality.ABSTRACT)) {
+            if ((typeArgs.size != args.size) && (baseClass.modality == Modality.SEALED || baseClass.modality == Modality.ABSTRACT)) {
                 val serializer = findStandardKotlinTypeSerializer(compilerContext, context.irBuiltIns.unitType)!!
                 // workaround for sealed and abstract classes - the `serializer` function expects non-null serializers, but does not use them, so serializers of any type can be passed
                 List(baseClass.typeParameters.size) { irGetObject(serializer) }

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

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlinx.serialization.compiler.backend.ir
 
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
+import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.builders.IrBuilderWithScope
 import org.jetbrains.kotlin.ir.builders.irGet
 import org.jetbrains.kotlin.ir.builders.irGetField
@@ -78,6 +79,7 @@ fun IrBuilderWithScope.createPropertyByParamReplacer(
     Creates an initializer adapter function that can replace IR expressions of getting constructor parameter value by some other expression.
     Also adapter may replace IR expression of getting `this` value by another expression.
      */
+@OptIn(ObsoleteDescriptorBasedAPI::class)
 fun createInitializerAdapter(
     irClass: IrClass,
     paramGetReplacer: (ValueParameterDescriptor) -> IrExpression?,

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

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.StandardNames
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.builders.declarations.*
 import org.jetbrains.kotlin.ir.declarations.*
@@ -27,16 +28,12 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.platform.jvm.isJvm
-import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.jvm.JvmPrimitiveType
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationDependencies.LAZY_FQ
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationDependencies.LAZY_MODE_FQ
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationDependencies.LAZY_PUBLICATION_MODE_NAME
-import org.jetbrains.kotlinx.serialization.compiler.resolve.hasSerializableOrMetaAnnotation
-import org.jetbrains.kotlinx.serialization.compiler.resolve.isInheritableSerialInfoAnnotation
-import org.jetbrains.kotlinx.serialization.compiler.resolve.isSerialInfoAnnotation
 
 
 interface IrBuilderWithPluginContext {
@@ -134,7 +131,7 @@ interface IrBuilderWithPluginContext {
     }
 
     fun IrClass.contributeAnonymousInitializer(bodyGen: IrBlockBodyBuilder.() -> Unit) {
-        val symbol = IrAnonymousInitializerSymbolImpl(descriptor)
+        val symbol = IrAnonymousInitializerSymbolImpl(symbol)
         factory.createAnonymousInitializer(startOffset, endOffset, SERIALIZATION_PLUGIN_ORIGIN, symbol).also {
             it.parent = this
             declarations.add(it)
@@ -256,9 +253,6 @@ interface IrBuilderWithPluginContext {
             result
         )
 
-    @FirIncompatiblePluginAPI
-    fun KotlinType.toIrType() = compilerContext.typeTranslator.translateType(this)
-
     fun IrBuilderWithScope.setProperty(receiver: IrExpression, property: IrProperty, value: IrExpression): IrExpression {
         return if (property.setter != null)
             irSet(property.setter!!.returnType, receiver, property.setter!!.symbol, value)
@@ -269,7 +263,7 @@ interface IrBuilderWithPluginContext {
     fun IrBuilderWithScope.generateAnySuperConstructorCall(toBuilder: IrBlockBodyBuilder) {
         val anyConstructor = compilerContext.irBuiltIns.anyClass.owner.declarations.single { it is IrConstructor } as IrConstructor
         with(toBuilder) {
-            +IrDelegatingConstructorCallImpl.fromSymbolDescriptor(
+            +IrDelegatingConstructorCallImpl.fromSymbolOwner(
                 startOffset, endOffset,
                 compilerContext.irBuiltIns.unitType,
                 anyConstructor.symbol
@@ -348,14 +342,14 @@ interface IrBuilderWithPluginContext {
         createClassReference(classSymbol.starProjectedType, startOffset, endOffset)
 
     fun collectSerialInfoAnnotations(irClass: IrClass): List<IrConstructorCall> {
-        if (!(irClass.isInterface || irClass.descriptor.hasSerializableOrMetaAnnotation)) return emptyList()
+        if (!(irClass.isInterface || irClass.hasSerializableOrMetaAnnotation())) return emptyList()
         val annotationByFq: MutableMap<FqName, IrConstructorCall> =
-            irClass.annotations.associateBy { it.symbol.owner.parentAsClass.descriptor.fqNameSafe }.toMutableMap()
+            irClass.annotations.associateBy { it.symbol.owner.parentAsClass.fqNameWhenAvailable!! }.toMutableMap()
         for (clazz in irClass.getAllSuperclasses()) {
             val annotations = clazz.annotations
                 .mapNotNull {
-                    val descriptor = it.symbol.owner.parentAsClass.descriptor
-                    if (descriptor.isInheritableSerialInfoAnnotation) descriptor.fqNameSafe to it else null
+                    val parent = it.symbol.owner.parentAsClass
+                    if (parent.isInheritableSerialInfoAnnotation) parent.fqNameWhenAvailable!! to it else null
                 }
             annotations.forEach { (fqname, call) ->
                 if (fqname !in annotationByFq) {
@@ -371,7 +365,7 @@ interface IrBuilderWithPluginContext {
     fun IrBuilderWithScope.copyAnnotationsFrom(annotations: List<IrConstructorCall>): List<IrExpression> =
         annotations.mapNotNull { annotationCall ->
             val annotationClass = annotationCall.symbol.owner.parentAsClass
-            if (!annotationClass.descriptor.isSerialInfoAnnotation) return@mapNotNull null
+            if (!annotationClass.isSerialInfoAnnotation) return@mapNotNull null
 
             if (compilerContext.platform.isJvm()) {
                 val implClass = compilerContext.serialInfoImplJvmIrGenerator.getImplClass(annotationClass)
@@ -389,6 +383,7 @@ interface IrBuilderWithPluginContext {
             }
         }
 
+    @OptIn(ObsoleteDescriptorBasedAPI::class)
     fun IrBuilderWithScope.wrapperClassReference(classType: IrType): IrClassReference {
         if (compilerContext.platform.isJvm()) {
             // "Byte::class" -> "java.lang.Byte::class"

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

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.backend.jvm.ir.representativeUpperBound
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.expressions.IrExpression
@@ -23,11 +24,11 @@ import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.platform.js.isJs
+import org.jetbrains.kotlin.platform.konan.isNative
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.fir.SerializationPluginKey
-import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames
-import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationAnnotations
-import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationPackages
+import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 
 internal fun IrType.isKSerializer(): Boolean {
     val simpleType = this as? IrSimpleType ?: return false
@@ -89,7 +90,7 @@ private fun IrClass.checkSerializableOrMetaAnnotationArgs(mustDoNotHaveArgs: Boo
         return true
     }
     return annotations
-        .map { it.annotationClass.annotations }
+        .map { it.constructedClass.annotations }
         .any { it.hasAnnotation(SerializationAnnotations.metaSerializableAnnotationFqName) }
 }
 
@@ -98,6 +99,9 @@ internal val IrClass.isSerialInfoAnnotation: Boolean
             || annotations.hasAnnotation(SerializationAnnotations.inheritableSerialInfoFqName)
             || annotations.hasAnnotation(SerializationAnnotations.metaSerializableAnnotationFqName)
 
+internal val IrClass.isInheritableSerialInfoAnnotation: Boolean
+    get() = annotations.hasAnnotation(SerializationAnnotations.inheritableSerialInfoFqName)
+
 internal fun IrClass.shouldHaveGeneratedSerializer(context: SerializationPluginContext): Boolean
     = (isInternalSerializable && (modality == Modality.FINAL || modality == Modality.OPEN))
             || isEnumWithLegacyGeneratedSerializer(context)
@@ -142,6 +146,7 @@ fun IrClass.getSuperClassNotAny(): IrClass? {
     return if (parentClass.defaultType.isAny()) null else parentClass
 }
 
+@OptIn(ObsoleteDescriptorBasedAPI::class)
 internal fun IrDeclaration.isFromPlugin(): Boolean =
     this.origin == IrDeclarationOrigin.GeneratedByPlugin(SerializationPluginKey) || (this.descriptor as? CallableMemberDescriptor)?.kind == CallableMemberDescriptor.Kind.SYNTHESIZED // old FE doesn't specify origin
 
@@ -165,14 +170,35 @@ fun IrClass.findSerializableSyntheticConstructor(): IrConstructorSymbol? {
     return declarations.filterIsInstance<IrConstructor>().singleOrNull { it.isSerializationCtor() }?.symbol
 }
 
+internal fun IrClass.needSerializerFactory(compilerContext: SerializationPluginContext): Boolean {
+    if (!(compilerContext.platform?.isNative() == true || compilerContext.platform.isJs())) return false
+    val serializableClass = getSerializableClassDescriptorByCompanion(this) ?: return false
+    if (serializableClass.isSerializableObject) return true
+    if (serializableClass.isSerializableEnum()) return true
+    if (serializableClass.isAbstractOrSealedSerializableClass) return true
+    if (serializableClass.isSealedSerializableInterface) return true
+    if (serializableClass.typeParameters.isEmpty()) return false
+    return true
+}
+
+
+internal fun getSerializableClassDescriptorByCompanion(companion: IrClass): IrClass? {
+    if (companion.isSerializableObject) return companion
+    if (!companion.isCompanion) return null
+    val classDescriptor = (companion.parent as? IrClass) ?: return null
+    if (!classDescriptor.shouldHaveGeneratedMethodsInCompanion) return null
+    return classDescriptor
+}
+
+
 internal fun IrExpression.isInitializePropertyFromParameter(): Boolean =
     this is IrGetValueImpl && this.origin == IrStatementOrigin.INITIALIZE_PROPERTY_FROM_PARAMETER
 
-internal val IrConstructorCall.annotationClass
+internal val IrConstructorCall.constructedClass
     get() = this.symbol.owner.constructedClass
 
 internal val List<IrConstructorCall>.hasAnySerialAnnotation: Boolean
-    get() = serialNameValue != null || any { it.annotationClass.isSerialInfoAnnotation == true }
+    get() = serialNameValue != null || any { it.constructedClass.isSerialInfoAnnotation }
 
 internal val List<IrConstructorCall>.serialNameValue: String?
     get() = findAnnotation(SerializationAnnotations.serialNameAnnotationFqName)?.getStringConstArgument(0) // @SerialName("foo")

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

@@ -6,6 +6,7 @@
 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.IrProperty
 import org.jetbrains.kotlin.ir.types.IrSimpleType
@@ -41,6 +42,7 @@ class IrSerializableProperties(
     override val serializableStandaloneProperties: List<IrSerializableProperty>
 ) : ISerializableProperties<IrSerializableProperty>
 
+@OptIn(ObsoleteDescriptorBasedAPI::class)
 internal fun serializablePropertiesForIrBackend(
     irClass: IrClass,
     serializationDescriptorSerializer: SerializationDescriptorSerializerPlugin? = null

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

@@ -8,6 +8,7 @@ package org.jetbrains.kotlinx.serialization.compiler.backend.ir
 import org.jetbrains.kotlin.backend.common.extensions.FirIncompatiblePluginAPI
 import org.jetbrains.kotlin.backend.common.ir.addExtensionReceiver
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.builders.declarations.*
 import org.jetbrains.kotlin.ir.declarations.*
@@ -30,12 +31,14 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
+import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames
 
 // This doesn't support annotation arguments of type KClass and Array<KClass> because the codegen doesn't compute JVM signatures for
 // such cases correctly (because inheriting from annotation classes is prohibited in Kotlin).
 // Currently it results in an "accidental override" error where a method with return type KClass conflicts with the one with Class.
+@OptIn(ObsoleteDescriptorBasedAPI::class)
 class SerialInfoImplJvmIrGenerator(
     private val context: SerializationPluginContext,
     private val moduleFragment: IrModuleFragment,
@@ -53,7 +56,7 @@ class SerialInfoImplJvmIrGenerator(
 
     fun getImplClass(serialInfoAnnotationClass: IrClass): IrClass =
         annotationToImpl.getOrPut(serialInfoAnnotationClass) {
-            @OptIn(FirIncompatiblePluginAPI::class) // TODO
+            @OptIn(FirIncompatiblePluginAPI::class)
             val implClassSymbol = context.referenceClass(serialInfoAnnotationClass.kotlinFqName.child(SerialEntityNames.IMPL_NAME))
             implClassSymbol!!.owner.apply(this::generate)
         }
@@ -112,6 +115,9 @@ class SerialInfoImplJvmIrGenerator(
             putValueArgument(0, IrConstImpl.string(UNDEFINED_OFFSET, UNDEFINED_OFFSET, context.irBuiltIns.stringType, name))
         }
 
+    @FirIncompatiblePluginAPI
+    fun KotlinType.toIrType() = compilerContext.typeTranslator.translateType(this)
+
     private fun IrType.kClassToJClassIfNeeded(): IrType = when {
         this.isKClass() -> javaLangType
         this.isKClassArray() -> compilerContext.irBuiltIns.arrayClass.typeWith(javaLangType)

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

@@ -83,14 +83,14 @@ class SerializableCompanionIrGenerator(
 
         val irSerializableClass = if (irClass.isCompanion) irClass.parentAsClass else irClass
         val serializableWithAlreadyPresent = irSerializableClass.annotations.any {
-            it.symbol.descriptor.constructedClass.fqNameSafe == annotationMarkerClass.owner.fqNameWhenAvailable
+            it.constructedClass.fqNameWhenAvailable == annotationMarkerClass.owner.fqNameWhenAvailable
         }
         if (serializableWithAlreadyPresent) return
 
         val annotationCtor = annotationMarkerClass.constructors.single { it.owner.isPrimary }
         val annotationType = annotationMarkerClass.defaultType
 
-        val annotationCtorCall = IrConstructorCallImpl.fromSymbolDescriptor(startOffset, endOffset, annotationType, annotationCtor).apply {
+        val annotationCtorCall = IrConstructorCallImpl.fromSymbolOwner(startOffset, endOffset, annotationType, annotationCtor).apply {
             putValueArgument(
                 0,
                 createClassReference(
@@ -150,7 +150,7 @@ class SerializableCompanionIrGenerator(
     }
 
     private fun generateSerializerFactoryIfNeeded(getterDescriptor: IrSimpleFunction) {
-        if (!irClass.descriptor.needSerializerFactory()) return
+        if (!irClass.needSerializerFactory(compilerContext)) return
         val serialFactoryDescriptor = irClass.findDeclaration<IrSimpleFunction> {
             it.valueParameters.size == 1
                     && it.valueParameters.first().isVararg

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

@@ -6,7 +6,6 @@
 package org.jetbrains.kotlinx.serialization.compiler.backend.ir
 
 import org.jetbrains.kotlin.backend.common.lower.irThrow
-import org.jetbrains.kotlin.codegen.CompilationException
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.ir.IrStatement
@@ -19,12 +18,10 @@ import org.jetbrains.kotlin.ir.expressions.IrStatementOrigin
 import org.jetbrains.kotlin.ir.expressions.impl.IrDelegatingConstructorCallImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
-import org.jetbrains.kotlin.js.resolve.diagnostics.findPsi
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.utils.getOrPutNullable
-import org.jetbrains.kotlinx.serialization.compiler.diagnostic.serializableAnnotationIsUseless
 import org.jetbrains.kotlinx.serialization.compiler.extensions.SerializationPluginContext
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.CACHED_DESCRIPTOR_FIELD_NAME
@@ -97,8 +94,9 @@ class SerializableIrGenerator(
             }
 
             // Missing field exception parts
-            val exceptionCtorRef = compilerContext.referenceConstructors(ClassId(SerializationPackages.packageFqName, Name.identifier(MISSING_FIELD_EXC)))
-                .single { it.owner.valueParameters.singleOrNull()?.type?.isString() == true }
+            val exceptionCtorRef =
+                compilerContext.referenceConstructors(ClassId(SerializationPackages.packageFqName, Name.identifier(MISSING_FIELD_EXC)))
+                    .single { it.owner.valueParameters.singleOrNull()?.type?.isString() == true }
             val exceptionType = exceptionCtorRef.owner.returnType
 
             val seenVarsOffset = serializableProperties.bitMaskSlotCount()
@@ -244,7 +242,7 @@ class SerializableIrGenerator(
             ?: error("Non-serializable parent of serializable $irClass must have no arg constructor")
 
 
-        val call = IrDelegatingConstructorCallImpl.fromSymbolDescriptor(
+        val call = IrDelegatingConstructorCallImpl.fromSymbolOwner(
             startOffset,
             endOffset,
             compilerContext.irBuiltIns.unitType,
@@ -270,13 +268,14 @@ class SerializableIrGenerator(
         propertiesStart: Int
     ): Int {
         check(superClass.isInternalSerializable)
-        val superCtorRef = superClass.findSerializableSyntheticConstructor() ?: error("Class serializable internally should have special constructor with marker")
+        val superCtorRef = superClass.findSerializableSyntheticConstructor()
+            ?: error("Class serializable internally should have special constructor with marker")
         val superProperties = serializablePropertiesForIrBackend(superClass).serializableProperties
         val superSlots = superProperties.bitMaskSlotCount()
         val arguments = allValueParameters.subList(0, superSlots) +
                 allValueParameters.subList(propertiesStart, propertiesStart + superProperties.size) +
                 allValueParameters.last() // SerializationConstructorMarker
-        val call = IrDelegatingConstructorCallImpl.fromSymbolDescriptor(
+        val call = IrDelegatingConstructorCallImpl.fromSymbolOwner(
             startOffset,
             endOffset,
             compilerContext.irBuiltIns.unitType,
@@ -307,7 +306,7 @@ class SerializableIrGenerator(
             // Compute offset of properties in superclass
             var ignoreIndexTo = -1
             val superClass = irClass.getSuperClassOrAny()
-            if (superClass.descriptor.isInternalSerializable) {
+            if (superClass.isInternalSerializable) {
                 ignoreIndexTo = serializablePropertiesForIrBackend(superClass).serializableProperties.size
 
                 // call super.writeSelf
@@ -380,16 +379,18 @@ class SerializableIrGenerator(
             irClass: IrClass,
             context: SerializationPluginContext,
         ) {
-            val serializableClass = irClass.descriptor
-
-            if (serializableClass.isInternalSerializable) {
+            if (irClass.isInternalSerializable) {
                 SerializableIrGenerator(irClass, context).generate()
                 irClass.patchDeclarationParents(irClass.parent)
-            } else if (serializableClass.serializableAnnotationIsUseless) {
-                throw CompilationException(
-                    "@Serializable annotation on $serializableClass would be ignored because it is impossible to serialize it automatically. " +
-                            "Provide serializer manually via e.g. companion object", null, serializableClass.findPsi()
-                )
+            } else {
+                val serializableAnnotationIsUseless = with(irClass) {
+                    hasSerializableOrMetaAnnotationWithoutArgs() && !isInternalSerializable && !hasCompanionObjectAsSerializer && kind != ClassKind.ENUM_CLASS && !isSealedSerializableInterface
+                }
+                if (serializableAnnotationIsUseless)
+                    throw AssertionError(
+                        "@Serializable annotation on $irClass would be ignored because it is impossible to serialize it automatically. " +
+                                "Provide serializer manually via e.g. companion object"
+                    )
             }
         }
     }

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

@@ -54,8 +54,7 @@ class SerializerForEnumsGenerator(
         val decode = decoderClass.functionByName(CallingConventions.decodeEnum)
         val serialDescGetter = irGet(descriptorGetterSymbol.owner.returnType, irThis(), descriptorGetterSymbol)
 
-        val serializableIrClass = requireNotNull(serializableIrClass) { "Enums do not support external serialization" }
-        val valuesF = serializableIrClass.functions.single { it.name == StandardNames.ENUM_VALUES }
+        val valuesF = this@SerializerForEnumsGenerator.serializableIrClass.functions.single { it.name == StandardNames.ENUM_VALUES }
         val getValues = irInvoke(dispatchReceiver = null, callee = valuesF.symbol)
 
 
@@ -67,7 +66,7 @@ class SerializerForEnumsGenerator(
                 getValues,
                 arrayGet.symbol,
                 irInvoke(irGet(loadFunc.valueParameters[0]), decode, serialDescGetter),
-                typeHint = serializableIrClass.defaultType
+                typeHint = this@SerializerForEnumsGenerator.serializableIrClass.defaultType
             )
         +irReturn(getValueByOrdinal)
     }

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

@@ -16,14 +16,11 @@ import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.deepCopyWithVariables
-import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
-import org.jetbrains.kotlin.ir.expressions.IrExpression
-import org.jetbrains.kotlin.ir.expressions.IrExpressionBody
+import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.IrBranchImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrDelegatingConstructorCallImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrGetValueImpl
-import org.jetbrains.kotlin.ir.expressions.mapValueParametersIndexed
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrConstructorSymbol
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
@@ -117,7 +114,7 @@ open class SerializerIrGenerator(
         }
 
         val anonymousInit = irClass.run {
-            val symbol = IrAnonymousInitializerSymbolImpl(descriptor)
+            val symbol = IrAnonymousInitializerSymbolImpl(symbol)
             irClass.factory.createAnonymousInitializer(startOffset, endOffset, SERIALIZATION_PLUGIN_ORIGIN, symbol).also {
                 it.parent = this
                 declarations.add(it)
@@ -207,7 +204,7 @@ open class SerializerIrGenerator(
         addFunctionBody(typedConstructorDescriptor) { ctor ->
             // generate call to primary ctor to init serialClassDesc and super()
             val primaryCtor = irClass.constructors.primary
-            +IrDelegatingConstructorCallImpl.fromSymbolDescriptor(
+            +IrDelegatingConstructorCallImpl.fromSymbolOwner(
                 startOffset,
                 endOffset,
                 compilerContext.irBuiltIns.unitType,
@@ -268,15 +265,11 @@ open class SerializerIrGenerator(
 
         val localSerialDesc = irTemporary(irGet(descriptorGetterSymbol.owner.returnType, irThis(), descriptorGetterSymbol), "desc")
 
-        //  fun beginStructure(desc: SerialDescriptor, vararg typeParams: KSerializer<*>): StructureEncoder
+        //  public fun beginStructure(descriptor: SerialDescriptor): CompositeDecoder
         val beginFunc =
             encoderClass.functions.single { it.owner.name.asString() == CallingConventions.begin && it.owner.valueParameters.size == 1 }
 
-        val call = irCall(beginFunc, type = kOutputClass.defaultType).mapValueParametersIndexed { _, _ ->
-            irGet(localSerialDesc)
-        }
-        // can it be done in more concise way? e.g. additional builder function?
-        call.dispatchReceiver = irGet(saveFunc.valueParameters[0])
+        val call = irInvoke(irGet(saveFunc.valueParameters[0]), beginFunc, irGet(localSerialDesc), typeHint = kOutputClass.defaultType)
         val objectToSerialize = saveFunc.valueParameters[1]
         val localOutput = irTemporary(call, "output")
 

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/extensions/SerializationLoweringExtension.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
 import org.jetbrains.kotlin.backend.common.runOnFilePostfix
 import org.jetbrains.kotlin.backend.jvm.ir.fileParent
 import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
@@ -93,6 +94,7 @@ private class SerializerClassLowering(
             SerializerIrGenerator.generate(irClass, context, context.metadataPlugin)
             SerializableCompanionIrGenerator.generate(irClass, context)
 
+            @OptIn(ObsoleteDescriptorBasedAPI::class)
             if (context.platform.isJvm() && KSerializerDescriptorResolver.isSerialInfoImpl(irClass.descriptor)) {
                 serialInfoJvmGenerator.generate(irClass)
             }

plugins/kotlin-serialization/kotlin-serialization-compiler/testData/boxIr/enumsAreCached.kt

@@ -20,7 +20,7 @@ enum class Plain {
 class Holder(val p: Plain, val w: WithNames)
 
 @OptIn(InternalSerializationApi::class)
-fun box(): String {
+fun testSerializers(): String {
     val cs = (Holder.serializer() as GeneratedSerializer<*>).childSerializers()
     val str1 = cs[0].toString()
     if (!str1.contains("kotlinx.serialization.internal.EnumSerializer")) return str1
@@ -32,4 +32,17 @@ fun box(): String {
 //    val str2 = cs[1].toString()
 //    if (!str2.contains("kotlinx.serialization.internal.EnumSerializer")) return str2
     return "OK"
+}
+
+fun testSerialization(previous: String): String {
+    if (previous != "OK") return previous
+    val h = Holder(Plain.B, WithNames.ENTRY1)
+    val s = Json.encodeToString(Holder.serializer(), h)
+    if (s != """{"p":"B","w":"A"}""") return s
+    if (Json.decodeFromString(Holder.serializer(), s).w != WithNames.ENTRY1) return "Deserialization failure"
+    return "OK"
+}
+
+fun box(): String {
+    return testSerialization(testSerializers())
 }