Parsing error on argument to LaTeX \vskip

[logological]

Pandoc's LaTeX parser doesn't seem to understand \vskip. It chokes as soon as it gets to the length argument, regardless whether it's positive or negative, bare or surrounded by braces. Here's a minimal example:

\documentclass{article}
\begin{document}
\vskip-1.5em foo
\end{document}

And here's the command-line output:

$ pandoc --to=docx test.tex > test.docx
Error at "test.tex" (line 3, column 7):
unexpected -
\vskip-1.5em foo
      ^

Again, line 3 could have been written as \vskip1.5em, \vskip{-1.5em}, etc.; Pandoc will emit a similar error regardless.

The problem occurs with Pandoc 3.4 (using try pandoc) and with Pandoc 3.3 on openSUSE Tumbleweed.

[jgm]

Looks like we are just missing em as a possible unit for dimension arguments -- as well as ex and px!