anchor.diff:        element = invocation.methodName.staticElement;
       }
       if (element is ExecutableElement) {
  -      return new _ExecutableParameters._(session, astProvider, element);
  +      return new _ExecutableParameters._(astProvider, element);
       } else {
         return null;
       }
     }
   
  -  _ExecutableParameters._(this.session, this.astProvider, this.executable) {
  +  _ExecutableParameters._(this.astProvider, this.executable) {
       for (var parameter in executable.parameters) {
         if (parameter.isNotOptional) {
           required.add(parameter);
  
positive.code: 
      Future<void> addParameter(int offset, String prefix, String suffix) async {
        if (offset != null) {
          DartChangeBuilder changeBuilder = await context.addParameter(
              offset, prefix, namedExpression.staticType, name, suffix);
          _addFixFromBuilder(
              changeBuilder, DartFixKind.ADD_MISSING_PARAMETER_NAMED,
              args: [name]);
  
negative.code:   final List<ParameterElement> optionalPositional = [];
    final List<ParameterElement> named = [];
  
    factory _ExecutableParameters(AstProvider astProvider, AstNode invocation) {
      Element element;
      if (invocation is InstanceCreationExpression) {
        element = invocation.staticElement;
  