Fontspec（和其他几个软件包）无法正常工作。我重新安装了 MacTeX-2018，但同样的错误不断出现（见下文）。l3kernel 和 l3packages 都已安装。TeX Live Utility 上的所有软件包都是最新的。我正在运行 macOS Mojave。
输入：
\documentclass{article}
\usepackage{fontspec}
\begin{document}
\section{Section}
\end{document}
输出：
TraditionalBuilder: Engine: xelatex. Invoking latexmk... done.
Errors:
/opt/local/share/texmf-texlive/tex/latex/l3packages/xparse/xparse.sty:26:
Missing = inserted for \ifnum. [\RequirePackage{expl3}[2018-04-12]]
/opt/local/share/texmf-texlive/tex/latex/l3packages/xparse/xparse.sty:27:
Missing = inserted for \ifnum. [\@ifpackagelater{expl3}{2018-04-12}]
/opt/local/share/texmf-texlive/tex/latex/fontspec/fontspec.sty:23:
Missing = inserted for \ifnum. [\ProvidesExplPackage]
/opt/local/share/texmf-texlive/tex/latex/fontspec/fontspec-xetex.sty:43:
Missing = inserted for \ifnum. [\ProvidesExplPackage]
Warnings:
/opt/local/share/texmf-texlive/tex/latex/fontspec/fontspec-xetex.sty:
Package fontspec Warning:
I have found the tuenc.def encoding definition file(fontspec)
but the TU encoding is not defined by the LaTeX2e(fontspec)
kernel; attempting to correct but you really should(fontspec)
update to the latest version of LaTeX2e.