Use ConstExp for storing constants.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import 'elements.dart';
+import '../cps_ir/const_expression.dart';
 import '../helpers/helpers.dart';  // Included for debug helpers.
 import '../tree/tree.dart';
 import '../util/util.dart';
 import '../resolution/resolution.dart';
 import '../resolution/class_members.dart' show ClassMemberMixin;
 
 import '../dart2jslib.dart' show invariant,
                                  InterfaceType,
                                  DartType,
                                  TypeVariableType,
@@ skipping 2585 matching lines @@
  *     const data = const Data();
  *
  *     @data
  *     class Foo {}
  *
  *     @data @data
  *     class Bar {}
  *
  * In this example, there are three instances of [MetadataAnnotation]
  * and they correspond each to a location in the source code where
- * there is an at-sign, '@'. The [value] of each of these instances
+ * there is an at-sign, '@'. The [constant] of each of these instances
  * are the same compile-time constant, [: const Data() :].
  *
  * The mirror system does not have a concept matching this class.
  */
 abstract class MetadataAnnotationX implements MetadataAnnotation {
   /**
    * The compile-time constant which this annotation resolves to.
    * In the mirror system, this would be an object mirror.
    */
-  Constant value;
+  ConstExp constant;
   Element annotatedElement;
   int resolutionState;
 
   /**
    * The beginning token of this annotation, or [:null:] if it is synthetic.
    */
   Token get beginToken;
 
   MetadataAnnotationX([this.resolutionState = STATE_NOT_STARTED]);
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
+    if (annotatedElement.isClass || annotatedElement.isTypedef) {
+      TypeDeclarationElement typeDeclaration = annotatedElement;
+      typeDeclaration.ensureResolved(compiler);
+    }
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   Node parseNode(DiagnosticListener listener);
 
-  String toString() => 'MetadataAnnotation($value, $resolutionState)';
+  String toString() => 'MetadataAnnotation($constant, $resolutionState)';
 }
 
 /// Metadata annotation on a parameter.
 class ParameterMetadataAnnotation extends MetadataAnnotationX {
   final Metadata metadata;
 
   ParameterMetadataAnnotation(Metadata this.metadata);
 
   Node parseNode(DiagnosticListener listener) => metadata.expression;
 
@@ skipping 47 matching lines @@
   AstElement get definingElement;
 
   bool get hasResolvedAst => definingElement.hasTreeElements;
 
   ResolvedAst get resolvedAst {
     return new ResolvedAst(declaration,
         definingElement.node, definingElement.treeElements);
   }
 
 }