Accessing the evaluated expression which caused an error

[Zach Riggle <zachriggle@xxxxxxxxx>]

I have a neat script that registers a TRAPERR function, which dumps
out a backtrace, with the filename, line of source, and a few lines of
source around the line where the error was triggered.  Here's a
contrived example: https://i.imgur.com/jDOa8Pq.png

This is done using funcfiletrace, funcstack, and syntax-highlighted
with 'bat'.  I'm aware of funcsourcetrace, funcstack, and TRAPDEBUG /
ZSH_DEBUG_CMD as well, but none of these contain the actual expression
evaluated -- just the input to zsh.

These are excellent to show a backtrace, but I'm curious whether there
are additional functions that I might be able to leverage to show the
fully-evaluated expression which caused TRAPERR to be invoked.

I know that zsh has the data internally, since "zsh -x" shows the
fully-evaluated expression, so that data must be available somewhere,
even if it's not exposed in a shell variable.

I looked through the docs, as well as the output of "env" and
"declare" from within TRAPERR, but couldn't find anything helpful.

Thanks!
Zach Riggle