Support malformed types

pkg/compiler/lib/src/serialization/element_serialization.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.serialization.elements;
 
 import '../common.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
+import '../diagnostics/messages.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart' show ErroneousElementX;
 import 'constant_serialization.dart';
 import 'keys.dart';
 import 'modelz.dart';
 import 'serialization.dart';
 import 'serialization_util.dart';
 
 /// Enum kinds used for encoding [Element]s.
 enum SerializedElementKind {
@@ skipping 185 matching lines @@
     return null;
   }
 
   void serialize(ErroneousElement element, ObjectEncoder encoder,
       SerializedElementKind kind) {
     encoder.setElement(Key.ENCLOSING, element.enclosingElement);
     encoder.setString(Key.NAME, element.name);
     encoder.setEnum(Key.MESSAGE_KIND, element.messageKind);
     if (element.messageArguments.isNotEmpty) {
       MapEncoder mapEncoder = encoder.createMap(Key.ARGUMENTS);
-      element.messageArguments.forEach((String key, String value) {
-        mapEncoder.setString(key, value);
+      element.messageArguments.forEach((String key, var value) {
+        mapEncoder.setString(key, Message.convertToString(value));
       });
     }
   }
 }
 
 class LibrarySerializer implements ElementSerializer {
   const LibrarySerializer();
 
   SerializedElementKind getSerializedKind(Element element) {
     if (element.isLibrary) {
@@ skipping 584 matching lines @@
         return new LocalVariableElementZ(decoder);
       case SerializedElementKind.EXTERNAL_LIBRARY:
       case SerializedElementKind.EXTERNAL_LIBRARY_MEMBER:
       case SerializedElementKind.EXTERNAL_CLASS_MEMBER:
       case SerializedElementKind.EXTERNAL_CONSTRUCTOR:
         break;
     }
     throw new UnsupportedError("Unexpected element kind '${elementKind}.");
   }
 }