Support malformed types

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

Index: pkg/compiler/lib/src/serialization/type_serialization.dart
diff --git a/pkg/compiler/lib/src/serialization/type_serialization.dart b/pkg/compiler/lib/src/serialization/type_serialization.dart
index 3d4cb9fd353d5ac8cd582d36a9b0032fb4d98743..24a46ae27f84757df04aac019727a6bd9b99f8e5 100644
--- a/pkg/compiler/lib/src/serialization/type_serialization.dart
+++ b/pkg/compiler/lib/src/serialization/type_serialization.dart
@@ -35,7 +35,9 @@ class TypeSerializer extends DartTypeVisitor<dynamic, ObjectEncoder> {
     encoder.setTypes(Key.NAMED_PARAMETER_TYPES, type.namedParameterTypes);
   }
 
-  void visitMalformedType(MalformedType type, ObjectEncoder encoder) {}
+  void visitMalformedType(MalformedType type, ObjectEncoder encoder) {
+    encoder.setElement(Key.ELEMENT, type.element);
+  }
 
   void visitInterfaceType(InterfaceType type, ObjectEncoder encoder) {
     encoder.setElement(Key.ELEMENT, type.element);
@@ -79,8 +81,11 @@ class TypeDeserializer {
         return new TypedefType(decoder.getElement(Key.ELEMENT),
             decoder.getTypes(Key.TYPE_ARGUMENTS, isOptional: true));
       case TypeKind.STATEMENT:
-      case TypeKind.MALFORMED_TYPE:
         throw new UnsupportedError("Unexpected type kind '${typeKind}.");
+      case TypeKind.MALFORMED_TYPE:
+        // TODO(johnniwinther): Do we need the 'userProvidedBadType' or maybe
+        // just a toString of it?
+        return new MalformedType(decoder.getElement(Key.ELEMENT), null);
       case TypeKind.DYNAMIC:
         return const DynamicType();
       case TypeKind.VOID: