GraphQL\Validator\Messages::unusedVariableMessage PHP Метод

    static function unusedVariableMessage($varName)
    {
        return "Variable \${$varName} is not used.";
    }

 public function __invoke(ValidationContext $context)
 {
     $visitedFragmentNames = new \stdClass();
     $variableDefs = [];
     $variableNameUsed = new \stdClass();
     return ['visitSpreadFragments' => true, Node::OPERATION_DEFINITION => ['enter' => function () use(&$visitedFragmentNames, &$variableDefs, &$variableNameUsed) {
         $visitedFragmentNames = new \stdClass();
         $variableDefs = [];
         $variableNameUsed = new \stdClass();
     }, 'leave' => function () use(&$visitedFragmentNames, &$variableDefs, &$variableNameUsed) {
         $errors = [];
         foreach ($variableDefs as $def) {
             if (empty($variableNameUsed->{$def->variable->name->value})) {
                 $errors[] = new Error(Messages::unusedVariableMessage($def->variable->name->value), [$def]);
             }
         }
         return !empty($errors) ? $errors : null;
     }], Node::VARIABLE_DEFINITION => function ($def) use(&$variableDefs) {
         $variableDefs[] = $def;
         return Visitor::skipNode();
     }, Node::VARIABLE => function ($variable) use(&$variableNameUsed) {
         $variableNameUsed->{$variable->name->value} = true;
     }, Node::FRAGMENT_SPREAD => function ($spreadAST) use(&$visitedFragmentNames) {
         // Only visit fragments of a particular name once per operation
         if (!empty($visitedFragmentNames->{$spreadAST->name->value})) {
             return Visitor::skipNode();
         }
         $visitedFragmentNames->{$spreadAST->name->value} = true;
     }];
 }