anchor.diff:    /// [token].
     void set period(Token token);
   
  -  /// Return the expression used to compute the object being indexed. If this
  -  /// index expression is not part of a cascade expression, then this is the
  -  /// same as [target]. If this index expression is part of a cascade
  +  /// Return the expression used to compute the object being indexed.
  +  ///
  +  /// If this index expression is not part of a cascade expression, then this
  +  /// is the same as [target]. If this index expression is part of a cascade
     /// expression, then the target expression stored with the cascade expression
     /// is returned.
     Expression get realTarget;
  
positive.code: ///
  /// Clients may not extend, implement or mix-in this class.
  abstract class Identifier implements Expression {
    /// Return the best element available for this operator. If resolution was
    /// able to find a better element based on type propagation, that element will
    /// be returned. Otherwise, the element found using the result of static
    /// analysis will be returned. If resolution has not been performed, then
    /// `null` will be returned.
    ///
    /// Deprecated: The analyzer no longer computes propagated type information.
    /// Use [staticElement] instead.
  
negative.code:   T thisOrAncestorOfType<T extends AstNode>();
  
    /// Return a textual description of this node in a form approximating valid
    /// source.
    ///
    /// The returned string will not be valid source primarily in the case where
    /// the node itself is not well-formed.
    String toSource();
  
    /// Use the given [visitor] to visit all of the children of this node.
    ///
    /// The children will be visited in lexical order.
    void visitChildren(AstVisitor visitor);
  }
  
  