anchor.diff:    }
   }
   
  -/// 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 {
  
positive.code:   /// A list containing all of the variables contained in this compilation unit.
    List<TopLevelVariableElement> _variables;
  
    /// Resynthesized explicit top-level property accessors.
    UnitExplicitTopLevelAccessors _explicitTopLevelAccessors;
  
    /// Resynthesized explicit top-level variables.
    UnitExplicitTopLevelVariables _explicitTopLevelVariables;
  
    /// Initialize a newly created compilation unit element to have the given
    /// [name].
    CompilationUnitElementImpl()
  
negative.code:       _createPropertiesAndAccessors(this);
        assert(_accessors != null);
        return _accessors;
      }
  
      return _accessors ?? const <PropertyAccessorElement>[];
  