Minor, make ProtoContainer sealed with two subclasses

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/MemberDeserializer.kt

@@ -239,8 +239,8 @@ public class MemberDeserializer(private val c: DeserializationContext) {
     }
 
     private fun DeclarationDescriptor.asProtoContainer(): ProtoContainer? = when(this) {
-        is PackageFragmentDescriptor -> ProtoContainer(null, fqName, c.nameResolver, c.typeTable)
-        is DeserializedClassDescriptor -> ProtoContainer(classProto, null, c.nameResolver, c.typeTable)
+        is PackageFragmentDescriptor -> ProtoContainer.Package(fqName, c.nameResolver, c.typeTable)
+        is DeserializedClassDescriptor -> ProtoContainer.Class(classProto, c.nameResolver, c.typeTable)
         else -> null // TODO: support annotations on lambdas and their parameters
     }
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/ProtoContainer.kt

@@ -19,16 +19,25 @@ package org.jetbrains.kotlin.serialization.deserialization
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.serialization.ProtoBuf
 
-public data class ProtoContainer(
-        val classProto: ProtoBuf.Class?,
-        val packageFqName: FqName?,
+sealed class ProtoContainer(
         val nameResolver: NameResolver,
         val typeTable: TypeTable
 ) {
-    init {
-        assert((classProto != null) xor (packageFqName != null))
+    class Class(
+            val classProto: ProtoBuf.Class,
+            nameResolver: NameResolver,
+            typeTable: TypeTable
+    ) : ProtoContainer(nameResolver, typeTable) {
+        override fun debugFqName(): FqName = nameResolver.getClassId(classProto.fqName).asSingleFqName()
     }
 
-    fun getFqName(): FqName =
-            packageFqName ?: nameResolver.getClassId(classProto!!.getFqName()).asSingleFqName()
+    class Package(
+            val fqName: FqName,
+            nameResolver: NameResolver,
+            typeTable: TypeTable
+    ) : ProtoContainer(nameResolver, typeTable) {
+        override fun debugFqName(): FqName = fqName
+    }
+
+    abstract fun debugFqName(): FqName
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedClassDescriptor.kt

@@ -296,7 +296,7 @@ public class DeserializedClassDescriptor(
             val annotations = enumEntryProtos[name]?.let { proto ->
                 DeserializedAnnotations(c.storageManager) {
                     c.components.annotationAndConstantLoader.loadEnumEntryAnnotations(
-                            ProtoContainer(classProto, null, c.nameResolver, c.typeTable), proto
+                            ProtoContainer.Class(classProto, c.nameResolver, c.typeTable), proto
                     )
                 }
             } ?: if (name in oldEnumEntryNames) Annotations.EMPTY