anchor.diff:    LibraryElement get exportedLibrary;
   }
   
  +/// An element that represents an extension.
  +///
  +/// Clients may not extend, implement or mix-in this class.
  +abstract class ExtensionElement implements Element {
  +  /// Return a list containing all of the accessors (getters and setters)
  +  /// declared in this extension.
  +  List<PropertyAccessorElement> get accessors;
  +
  +  /// Return the type that is extended by this extension.
  +  DartType get extendedType;
  +
  +  /// Return a list containing all of the methods declared in this extension.
  +  List<MethodElement> get methods;
  +
  +  /// Return a list containing all of the type parameters declared by this
  +  /// extension.
  +  List<TypeParameterElement> get typeParameters;
  +
  +  /// Return the element representing the getter with the given [name] that is
  +  /// declared in this extension, or `null` if this extension does not declare a
  +  /// getter with the given name.
  +  PropertyAccessorElement /*?*/ getGetter(String name);
  +
  +  /// Return the element representing the method with the given [name] that is
  +  /// declared in this extension, or `null` if this extension does not declare a
  +  /// method with the given name.
  +  MethodElement /*?*/ getMethod(String name);
  +
  +  /// Return the element representing the setter with the given [name] that is
  +  /// declared in this extension, or `null` if this extension does not declare a
  +  /// setter with the given name.
  +  PropertyAccessorElement /*?*/ getSetter(String name);
  +}
  +
   /// A field defined within a type.
   ///
   /// Clients may not extend, implement or mix-in this class.
  
positive.code:   /// Return `true` if this library is part of the SDK.
    bool get isInSdk;
  
    /// Return a list containing the strongly connected component in the
    /// import/export graph in which the current library resides.
    List<LibraryElement> get libraryCycle;
  
negative.code:   /// consists of. This includes the defining compilation unit and units
    /// included using the `part` directive.
    List<CompilationUnitElement> get units;
  
    /// Return a list containing all of the imports that share the given [prefix],
    /// or an empty array if there are no such imports.
  