anchor.diff:      }
     }
   
  -  /**
  -   * Resolve the instance fields in the given field declaration [node].
  -   */
  +  /// Resolve the instance fields in the given field declaration [node].
     void _resolveFieldDeclaration(FieldDeclaration node) {
       if (!node.isStatic) {
         for (VariableDeclaration field in node.fields.variables) {
  
positive.code:     return super.visitIsExpression(node);
    }
  
    /**
     * Check for instances of `x is double`, `x is int`, `x is! double` and
     * `x is! int`.
     *
     * @param node the is expression to check
     * @return `true` if and only if a hint code is generated on the passed node
     * See [HintCode.IS_DOUBLE],
     * [HintCode.IS_INT],
     * [HintCode.IS_NOT_DOUBLE], and
     * [HintCode.IS_NOT_INT].
     */
    bool _checkForIsDoubleHints(IsExpression node) {
      DartType type = node.type.type;
      Element element = type?.element;
  
negative.code:   }
  }
  
  /// A visitor that finds dead code and unused labels.
  class DeadCodeVerifier extends RecursiveAstVisitor<Object> {
    /// The error reporter by which errors will be reported.
    final ErrorReporter _errorReporter;
  
    ///  The type system for this visitor
    final TypeSystem _typeSystem;
  
    /// The object used to track the usage of labels within a given label scope.
    _LabelTracker labelTracker;
  
    /// Initialize a newly created dead code verifier that will report dead code
    /// to the given [errorReporter] and will use the given [typeSystem] if one is
    /// provided.
    DeadCodeVerifier(this._errorReporter, {TypeSystem typeSystem})
        : this._typeSystem = typeSystem ?? new StrongTypeSystemImpl(null);
  
  