Equivalent of ksh, zsh {N}<[WORD] ?

[R. Bernstein]

Both zsh and ksh have a way to open a file or duplicate a file
descriptor and let the interpreter pick the descriptor saving the
newly-allocated file descriptor number in a variable. In particular:

   exec {fd}<&0

will duplicate stdin and save the newly allocated file-descriptor
number to fd. Also:

   exec {fd}<filename

opens filename with a new file descriptor and saves the number
allocated in fd. Short of going outside of the language and using
lsof, /proc, or the processes table, I haven't been able to figure out
how to do the corresponding thing in bash. Is there a way?

If not, it would be great if a future version had this extension that
zsh and ksh both seem to have.

Thanks!