anchor.diff:      return _createInterfaceType(listClass, [elementType]);
     }
   
  +  /// Returns an instance of the `Set` type defined in 'dart:core' with
  +  /// [elementType] as its type argument.
  +  ///
  +  /// If no type argument is provided, the canonical raw type is returned.
  +  InterfaceType setType([DartType elementType]) {
  +    if (elementType == null) {
  +      return _getRawType(setClass);
  +    }
  +    return _createInterfaceType(setClass, [elementType]);
  +  }
  +
     /// Returns an instance of the `Map` type defined in 'dart:core' with
     /// [keyType] and [valueType] as its type arguments.
     ///
  
positive.code:     }
    }
  
    FieldEntity get symbolField => symbolImplementationField;
  
    InterfaceType get symbolImplementationType =>
  
negative.code:   /// The `List` class defined in 'dart:core';
    ClassEntity _listClass;
    ClassEntity get listClass => _listClass ??= _findClass(coreLibrary, 'List');
  
    /// The `Set` class defined in 'dart:core'.
    ClassEntity _setClass;
    ClassEntity get setClass => _setClass ??= _findClass(coreLibrary, 'Set');
  
    /// The `Map` class defined in 'dart:core';
    ClassEntity _mapClass;
  