Added support serialization of local classes in IR backend

Resolves Kotlin/kotlinx.serialization#1427

plugins/kotlin-serialization/kotlin-serialization-compiler/testData/diagnostics/LocalAndAnonymous.kt

@@ -1,17 +1,42 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER,-UNUSED_VARIABLE
+// !DIAGNOSTICS: -UNUSED_PARAMETER,-UNUSED_VARIABLE,-EXPERIMENTAL_API_USAGE_ERROR,-EXPERIMENTAL_API_USAGE
 // WITH_RUNTIME
 // SKIP_TXT
 
 import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
 
 fun container() {
-    <!LOCAL_CLASSES_NOT_SUPPORTED!>@Serializable<!>
-    class X
+    @Serializable
+    class X // local classes are allowed
 
-    val y = <!LOCAL_CLASSES_NOT_SUPPORTED!>@Serializable<!> object {}
+    val y = <!ANONYMOUS_OBJECTS_NOT_SUPPORTED!>@Serializable<!> object {
+        fun inObjectFun() {
+            <!ANONYMOUS_OBJECTS_NOT_SUPPORTED!>@Serializable<!>
+            class X // local classes in anonymous object functions are not allowed
+        }
+    }
+
+
+    class LocalSerializer : KSerializer<Any?> {
+        override val descriptor: SerialDescriptor = buildSerialDescriptor("tmp", PrimitiveKind.INT)
+        override fun serialize(encoder: Encoder, value: Any?) {
+            encoder.encodeNull()
+        }
+
+        override fun deserialize(decoder: Decoder): Any? {
+            return decoder.decodeNull()
+        }
+    }
+
+    @Serializable
+    class WithLocalSerializerInProperty(<!LOCAL_SERIALIZER_USAGE!>@Serializable(with = LocalSerializer::class)<!> val x: Any?)
+
+    <!LOCAL_SERIALIZER_USAGE, SERIALIZER_TYPE_INCOMPATIBLE!>@Serializable(with = LocalSerializer::class)<!>
+    data class WithLocalSerializer(val i: Int)
 }
 
-val topLevelAnon = <!LOCAL_CLASSES_NOT_SUPPORTED!>@Serializable<!> object {}
+val topLevelAnon = <!ANONYMOUS_OBJECTS_NOT_SUPPORTED!>@Serializable<!> object {}
 
 @Serializable class A {
     @Serializable class B // nested classes are allowed
@@ -19,4 +44,4 @@ val topLevelAnon = <!LOCAL_CLASSES_NOT_SUPPORTED!>@Serializable<!> object {}
     <!INNER_CLASSES_NOT_SUPPORTED!>@Serializable<!> inner class C // inner classes are not
 
     @Serializable object F {} // regular named object, OK
-}
+}

plugins/kotlin-serialization/kotlin-serialization-compiler/testData/diagnostics/SerializerTypeIncompatible.kt

@@ -14,6 +14,9 @@ object BazSerializer: KSerializer<Baz>
 @Serializer(forClass = Baz::class)
 object NullableBazSerializer: KSerializer<Baz?>
 
+<!SERIALIZER_TYPE_INCOMPATIBLE!>@Serializable(with = BazSerializer::class)<!>
+class Biz(val i: Int)
+
 @Serializable
 class Foo(@Serializable(with = BazSerializer::class) val i: <!SERIALIZER_TYPE_INCOMPATIBLE!>Bar<!>)