Error in bash syntax file

The following line of legal bash code gets flagged as an error:

echo ${@:i:1}

The above line displays the i'th command line argument.

I am running vim 8.1, with lots of patches applied. My sh.vim files (3 of them) are all dated Jun 15, 2019.

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/vim_use/362297683.6459386.1596059832744%40mail.yahoo.com.