Add SerializerFactory supertype for Native & JS in FIR serialization plugin.

This supertype is intended to be used with @AssociatedObject on platforms
where reflection possibilities are limited.

plugins/kotlinx-serialization/kotlinx-serialization.k2/build.gradle.kts

@@ -10,6 +10,8 @@ dependencies {
     compileOnly(project(":compiler:fir:tree"))
     compileOnly(project(":compiler:fir:resolve"))
     compileOnly(project(":compiler:fir:entrypoint"))
+    compileOnly(project(":js:js.config"))
+    compileOnly(project(":compiler:cli-common"))
 
     implementation(project(":kotlinx-serialization-compiler-plugin.common"))
 

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirResolveExtension.kt

@@ -32,7 +32,10 @@ import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.SpecialNames
+import org.jetbrains.kotlin.platform.js.isJs
+import org.jetbrains.kotlin.platform.konan.isNative
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames
+import org.jetbrains.kotlinx.serialization.compiler.resolve.SerialEntityNames.SERIALIZER_FACTORY_INTERFACE_NAME
 import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationPackages
 
 val generatedSerializerClassId = ClassId(SerializationPackages.internalPackageFqName, SerialEntityNames.GENERATED_SERIALIZER_CLASS)
@@ -321,6 +324,10 @@ class SerializationFirResolveExtension(session: FirSession) : FirDeclarationGene
             name = SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT
             symbol = FirRegularClassSymbol(classId)
             superTypeRefs += session.builtinTypes.anyType
+            if (owner.companionNeedsSerializerFactory()) {
+                val serializerFactoryClassId = ClassId(SerializationPackages.internalPackageFqName, SERIALIZER_FACTORY_INTERFACE_NAME)
+                superTypeRefs += serializerFactoryClassId.constructClassLikeType(emptyArray(), false).toFirResolvedTypeRef()
+            }
         }
         return regularClass.symbol
     }
@@ -328,4 +335,14 @@ class SerializationFirResolveExtension(session: FirSession) : FirDeclarationGene
     override fun FirDeclarationPredicateRegistrar.registerPredicates() {
         register(FirSerializationPredicates.annotatedWithSerializable)
     }
+
+    private fun FirClassSymbol<*>.companionNeedsSerializerFactory(): Boolean {
+        if (!(moduleData.platform.isNative() || moduleData.platform.isJs())) return false
+        if (isSerializableObject) return true
+        if (isSerializableEnum) return true
+        if (isAbstractOrSealedSerializableClass) return true
+        if (isSealedSerializableInterface) return true
+        if (typeParameterSymbols.isEmpty()) return false
+        return true
+    }
 }

plugins/kotlinx-serialization/kotlinx-serialization.k2/src/org/jetbrains/kotlinx/serialization/compiler/fir/SerializationFirUtils.kt

@@ -157,6 +157,9 @@ internal val FirClassSymbol<*>.isInternalSerializable: Boolean
         return hasSerializableAnnotationWithoutArgs
     }
 
+internal val FirClassSymbol<*>.isAbstractOrSealedSerializableClass: Boolean
+    get() = isInternalSerializable && (rawStatus.modality == Modality.ABSTRACT || rawStatus.modality == Modality.SEALED)
+
 internal val FirClassSymbol<*>.isInternallySerializableEnum: Boolean
     get() = classKind.isEnumClass && hasSerializableAnnotationWithoutArgs