Update elements, nodes and visitors for serialization.

pkg/compiler/lib/src/typechecker.dart

Index: pkg/compiler/lib/src/typechecker.dart
diff --git a/pkg/compiler/lib/src/typechecker.dart b/pkg/compiler/lib/src/typechecker.dart
index bd230563c9991ea6deef58172796a8e4186da1ea..d232bdf85df54baee48f4d51d52a81d285c8ef86 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -26,6 +26,7 @@ import 'elements/elements.dart' show
     Element,
     Elements,
     EnumClassElement,
+    EnumConstantElement,
     ExecutableElement,
     FieldElement,
     FunctionElement,
@@ -1945,7 +1946,7 @@ class TypeCheckerVisitor extends Visitor<DartType> {
             <ConstantValue, FieldElement>{};
         List<FieldElement> unreferencedFields = <FieldElement>[];
         EnumClassElement enumClass = expressionType.element;
-        enumClass.enumValues.forEach((FieldElement field) {
+        enumClass.enumValues.forEach((EnumConstantElement field) {
           ConstantValue constantValue =
               compiler.constants.getConstantValueForVariable(field);
           if (constantValue == null) {