solution

<?PHP
    NAMESPACE ILLI\Bug;
    INTERFACE Foo {}

    CLASS Instance IMPLEMENTS Foo
    {
        private static $instances = [];

        public static function getInstance()
        {
            $thread = get_called_class();

            if(isset(self::$instances[$thread]))
                return self::$instances[$thread];

            self::$instances[$thread] = new $thread;
            return self::$instances[$thread]->__staticconstruct();
        }
        /*
        use tInstance
        {
            tInstance_get as public getInstance;
        }
        */
        private static $counter = 0;

        private function __construct()
        {
        }

        private function __staticconstruct()
        {
            var_dump(self::getInstance() instanceOf Foo);
            return $this;
        }
    }