Fix SourceElement for classes loaded in decompiler

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

@@ -26,7 +26,7 @@ data class ClassData(
 
 data class ClassDataWithSource(
         val classData: ClassData,
-        val sourceElement: SourceElement = SourceElement.NO_SOURCE
+        val sourceElement: SourceElement
 )
 
 data class PackageData(

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

@@ -53,4 +53,6 @@ sealed class ProtoContainer(
     }
 
     abstract fun debugFqName(): FqName
+
+    override fun toString() = "${javaClass.simpleName}: ${debugFqName()}"
 }