Add a task to the new task model for computing constant values.

pkg/analyzer/lib/src/task/general.dart

 // Copyright (c) 2015, 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 analyzer.src.task.general;
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
+import 'package:analyzer/src/generated/element.dart';
 
 /**
  * A task that gets the contents of the source associated with an analysis
  * target.
  */
 class GetContentTask extends SourceBasedAnalysisTask {
   /**
    * The task descriptor describing this kind of task.
    */
   static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('GetContentTask',
@@ skipping 34 matching lines @@
    * Create a [GetContentTask] based on the given [target] in the given
    * [context].
    */
   static GetContentTask createTask(
       AnalysisContext context, AnalysisTarget target) {
     return new GetContentTask(context, target);
   }
 }
 
 /**
+ * A base class for analysis tasks whose target is expected to be an element.
+ */
+abstract class ElementBasedAnalysisTask extends AnalysisTask {

[scheglov, 2015/05/08 18:46:08]

I'm not sure that this is a right place for this task.
Elements are probably too Dart specific.
Maybe move it to src/dart.dart ?

[Brian Wilkerson, 2015/05/08 19:22:38]

Agreed.

[Paul Berry, 2015/05/08 19:44:22]

Done.

+  /**
+   * Initialize a newly created task to perform analysis within the given
+   * [context] in order to produce results for the given [element].
+   */
+  ElementBasedAnalysisTask(AnalysisContext context, Element element)
+      : super(context, element);
+
+  @override
+  String get description {
+    Source source = target.source;
+    String sourceName = source == null ? '<unknown source>' : source.fullName;
+    return '${descriptor.name} for element $target in source $sourceName';
+  }
+}
+
+/**
  * A base class for analysis tasks whose target is expected to be a source.
  */
 abstract class SourceBasedAnalysisTask extends AnalysisTask {
   /**
    * Initialize a newly created task to perform analysis within the given
    * [context] in order to produce results for the given [target].
    */
   SourceBasedAnalysisTask(AnalysisContext context, AnalysisTarget target)
       : super(context, target);
 
   @override
   String get description {
     Source source = target.source;
     String sourceName = source == null ? '<unknown source>' : source.fullName;
     return '${descriptor.name} for source $sourceName';
   }
 }