Use ConstExp for storing constants.

sdk/lib/_internal/compiler/implementation/patch_parser.dart

 // Copyright (c) 2012, 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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 310 matching lines @@
                               EagerAnnotationHandler handler) {
     for (Link<MetadataAnnotation> link = element.metadata;
          !link.isEmpty;
          link = link.tail) {
       MetadataAnnotation annotation = link.head;
       if (handler.apply(compiler, element, annotation)) {
         // TODO(johnniwinther): Perform this check in
         // [Compiler.onLibrariesLoaded].
         compiler.enqueuer.resolution.addDeferredAction(element, () {
           annotation.ensureResolved(compiler);
-          handler.validate(compiler, element, annotation, annotation.value);
+          handler.validate(
+              compiler, element, annotation, annotation.constant.value);
         });
         return true;
       }
     }
     return false;
   }
 }
 
 /// Annotation handler for pre-resolution detection of `@Native(...)`
 /// annotations.
@@ skipping 155 matching lines @@
         "Trying to patch a function more than once.");
   }
   origin.applyPatch(patch);
 }
 
 // TODO(johnniwinther): Add unittest when patch is (real) metadata.
 bool isPatchElement(leg.Compiler compiler, Element element) {
   return EagerAnnotationHandler.checkAnnotation(compiler, element,
       const PatchAnnotationHandler());
 }