anchor.diff:    }
   
     @override
  -  void evaluate(ConstantExpression constant) {
  -    constantValueMap.putIfAbsent(constant, () {
  -      return constant.evaluate(
  -          new AstEvaluationEnvironment(compiler), constantSystem);
  -    });
  -  }
  +  void evaluate(ConstantExpression constant) {}
   
     ConstantExpression compileVariable(VariableElement element) {
       return internalCompileVariable(element, false, true);
  
positive.code: 
  library dart2js.compile_time_constant_evaluator;
  
  import 'common/resolution.dart' show Resolution;
  import 'common/tasks.dart' show CompilerTask, Measurer;
  import 'common.dart';
  import 'compiler.dart' show Compiler;
  import 'constant_system_dart.dart';
  import 'constants/constant_system.dart';
  import 'constants/constructors.dart';
  import 'constants/evaluation.dart';
  import 'constants/expressions.dart';
  import 'constants/values.dart';
  import 'common_elements.dart' show CommonElements;
  import 'elements/elements.dart';
  import 'elements/types.dart' show DartTypes;
  import 'elements/modelx.dart' show ConstantVariableMixin;
  import 'elements/operators.dart';
  import 'elements/resolution_types.dart';
  import 'resolution/tree_elements.dart' show TreeElements;
  import 'resolution/deferred_load.dart' show AstDeferredLoadTask;
  import 'tree/tree.dart';
  import 'universe/call_structure.dart' show CallStructure;
  import 'util/util.dart' show Link;
  
  /// A [ConstantEnvironment] provides access for constants compiled for variable
  /// initializers.
  
negative.code:       Node node, TreeElements definitions,
        {bool isConst: true}) {
      assert(node != null);
      return null;
    }
  
  