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 c3d081ca8e7c7c0cf23f5c3139da02d4ac36c608..9593b10a14c5a47d5ee972c32bb222f195330496 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -23,6 +23,7 @@ import 'elements/elements.dart'
         Element,
         Elements,
         EnumClassElement,
+        EnumConstantElement,
         ExecutableElement,
         FieldElement,
         FunctionElement,
@@ -1953,7 +1954,7 @@ 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) {