anchor.diff:        _createPropertiesAndAccessors(this);
         assert(_accessors != null);
         return _accessors;
  -    }
  -
  -    if (_explicitTopLevelAccessors != null) {
  -      _accessors = <PropertyAccessorElementImpl>[]
  -        ..addAll(_explicitTopLevelAccessors.accessors)
  -        ..addAll(_explicitTopLevelVariables.implicitAccessors);
       }
   
       return _accessors ?? const <PropertyAccessorElement>[];
  
positive.code:   }
  }
  
  /// Container with information about explicit top-level property accessors and
  /// corresponding implicit top-level variables.
  class UnitExplicitTopLevelAccessors {
    final List<PropertyAccessorElementImpl> accessors =
        <PropertyAccessorElementImpl>[];
    final List<TopLevelVariableElementImpl> implicitVariables =
        <TopLevelVariableElementImpl>[];
  }
  
  /// Container with information about explicit top-level variables and
  /// corresponding implicit top-level property accessors.
  class UnitExplicitTopLevelVariables {
    final List<TopLevelVariableElementImpl> variables;
    final List<PropertyAccessorElementImpl> implicitAccessors =
        <PropertyAccessorElementImpl>[];
  
    UnitExplicitTopLevelVariables(int numberOfVariables)
        : variables = numberOfVariables != 0
              ? new List<TopLevelVariableElementImpl>(numberOfVariables)
              : const <TopLevelVariableElementImpl>[];
  }
  
  /// A concrete implementation of a [UriReferencedElement].
  abstract class UriReferencedElementImpl extends ElementImpl
      implements UriReferencedElement {
  
negative.code:   /// A list containing all of the variables contained in this compilation unit.
    List<TopLevelVariableElement> _variables;
  
    /// Initialize a newly created compilation unit element to have the given
    /// [name].
    CompilationUnitElementImpl()
  