Compute frontend/backend specific constants.

sdk/lib/_internal/compiler/implementation/js_emitter/metadata_emitter.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.
 
 part of dart2js.js_emitter;
 
 class MetadataEmitter extends CodeEmitterHelper {
   /// A list of JS expressions that represent metadata, parameter names and
   /// type, and return types.
   final List<String> globalMetadata = [];
 
   /// A map used to canonicalize the entries of globalMetadata.
   final Map<String, int> globalMetadataMap = <String, int>{};
 
   /// The metadata function returns the metadata associated with
   /// [element] in generated code.  The metadata needs to be wrapped
   /// in a function as it refers to constants that may not have been
   /// constructed yet.  For example, a class is allowed to be
   /// annotated with itself.  The metadata function is used by
   /// mirrors_patch to implement DeclarationMirror.metadata.
   jsAst.Fun buildMetadataFunction(Element element) {
     if (!backend.retainMetadataOf(element)) return null;
     return compiler.withCurrentElement(element, () {
       var metadata = [];
       Link link = element.metadata;
       // TODO(ahe): Why is metadata sometimes null?
       if (link != null) {
         for (; !link.isEmpty; link = link.tail) {
           MetadataAnnotation annotation = link.head;
-          Constant value = annotation.value;
+          Constant value =
+              backend.constants.getConstantForMetadata(annotation);
           if (value == null) {
             compiler.internalError(annotation, 'Annotation value is null.');
           } else {
             metadata.add(task.constantReference(value));
           }
         }
       }
       if (metadata.isEmpty) return null;
       return js.fun(
           [], [js.return_(new jsAst.ArrayInitializer.from(metadata))]);
     });
   }
 
   List<int> reifyDefaultArguments(FunctionElement function) {
     FunctionSignature signature = function.functionSignature;
     if (signature.optionalParameterCount == 0) return const [];
     List<int> defaultValues = <int>[];
     for (Element element in signature.optionalParameters) {
-      Constant value =
-          compiler.constantHandler.initialVariableValues[element];
+      Constant value = backend.constants.getConstantForVariable(element);
       String stringRepresentation = (value == null)
           ? "null"
           : jsAst.prettyPrint(task.constantReference(value), compiler)
               .getText();
       defaultValues.add(addGlobalMetadata(stringRepresentation));
     }
     return defaultValues;
   }
 
   int reifyMetadata(MetadataAnnotation annotation) {
-    Constant value = annotation.value;
+    Constant value = backend.constants.getConstantForMetadata(annotation);
     if (value == null) {
       compiler.internalError(annotation, 'Annotation value is null.');
       return -1;
     }
     return addGlobalMetadata(
         jsAst.prettyPrint(task.constantReference(value), compiler).getText());
   }
 
   int reifyType(DartType type) {
     jsAst.Expression representation =
@@ skipping 52 matching lines @@
       // TODO(ahe): Why is metadata sometimes null?
       if (link != null) {
         for (; !link.isEmpty; link = link.tail) {
           metadata.add(reifyMetadata(link.head));
         }
       }
       return metadata;
     });
   }
 }