anchor.diff:    /// - The type arguments from enclosing functions and closures for a
     ///   kindBinding.
     /// - The [_FunctionParameters] of a function type.
  -  /// - TBD for kindGenericFunction.
  +  /// - The type parameter bounds of a generic function.
     dynamic _rest;
   
     static Object _getRest(Rti rti) => rti._rest;
  
positive.code:   static _FunctionParameters _getFunctionParameters(Rti rti) {
      assert(_getKind(rti) == kindFunction);
      return JS('_FunctionParameters', '#', _getRest(rti));
    }
  
    /// On [Rti]s that are type environments*, derived types are cached on the
  
negative.code: 
    Object _requiredPositional;
    static JSArray _getRequiredPositional(_FunctionParameters parameters) =>
        JS('JSUnmodifiableArray', '#', parameters._requiredPositional);
    static void _setRequiredPositional(
        _FunctionParameters parameters, Object requiredPositional) {
      parameters._requiredPositional = requiredPositional;
  