anchor.diff:      Map<int, int> localClosureIndexMap = serializeFunctionBody(b,
           node.initializers, node.body, node.constKeyword != null, false, false);
       if (node.constKeyword != null) {
  -      Set<String> constructorParameterNames =
  -          node.parameters.parameters.map((p) => p.identifier.name).toSet();
  +      List<String> constructorParameterNames =
  +          node.parameters.parameters.map((p) => p.identifier.name).toList();
         b.constantInitializers = node.initializers
             .map((ConstructorInitializer initializer) =>
                 serializeConstructorInitializer(initializer, (Expression expr) {
  
positive.code:   /// needed by type inference.
    bool _serializeClosureBodyExprs = false;
  
    /// If a closure function body is being serialized, the set of closure
    /// parameter names which are currently in scope.  Otherwise `null`.
    Set<String> _parameterNames;
  
    /// Indicates whether parameters found during visitors might inherit
    /// covariance.
  
negative.code:   /// Serialize the given [expression], creating an [UnlinkedExprBuilder].
    UnlinkedExprBuilder serializeConstExpr(
        bool forConst, Map<int, int> localClosureIndexMap, Expression expression,
        [List<String> variableNames]) {
      _ConstExprSerializer serializer = new _ConstExprSerializer(
          forConst, this, localClosureIndexMap, variableNames);
      serializer.serialize(expression);
      return serializer.toBuilder(expression.beginToken, expression.endToken);
    }
  