Flow\TokenStream::expect PHP Method

    public function expect($primary, $secondary = null)
    {
        $token = $this->getCurrentToken();
        if (is_null($secondary) && !is_int($primary)) {
            $secondary = $primary;
            $primary = Token::NAME;
        }
        if (!$token->test($primary, $secondary)) {
            if (is_null($secondary)) {
                $expecting = Token::getTypeError($primary);
            } elseif (is_array($secondary)) {
                $expecting = '"' . implode('" or "', $secondary) . '"';
            } else {
                $expecting = '"' . $secondary . '"';
            }
            if ($token->getType() === Token::EOF) {
                throw new SyntaxError('unexpected end of file', $token);
            } else {
                throw new SyntaxError(sprintf('unexpected "%s", expecting %s', str_replace("\n", '\\n', $token->getValue()), $expecting), $token);
            }
        }
        $this->next();
        return $token;
    }