我正在尝试在列表中使用自定义的类似定理的环境（使用包enumitem），但收到错误消息
“LaTeX 错误：出现问题——可能缺少 \item。”
在列表之外，自定义环境可以正常工作。我该如何纠正这个问题？enumitem包和自定义环境之间是否存在不兼容问题？
以下是 MWE：
\documentclass{article}
\usepackage{amsthm} % theorem-like environments
\usepackage{framed} % vertical bar to the left of text of custom environment
\usepackage{enumitem} % enumerations
\usepackage{lipsum} % dummy text
% custom environment, with vertical bar to the left of text
\newtheorem{theoremzz}{Theorem}
\newenvironment{theorem}[1][]{\begin{theoremzz}[#1]\begin{leftbar}}{\end{leftbar}\end{theoremzz}}
% default environment
\newtheorem{proposition}[theoremzz]{Proposition}
\begin{document}
\begin{enumerate}
\item I want my custom \texttt{theorem} environment inside this item of the list.
\begin{theorem}
\lipsum[1][1-4]
\end{theorem}
As you can see, it did not work correctly.
\item Now an attempt with a default \texttt{proposition} environment:
\begin{proposition}
\lipsum[2][1-4]
\end{proposition}
It works!
\end{enumerate}
\noindent Outside the list, the custom environment works:
\begin{theorem}
\lipsum[3][1-4]
\end{theorem}
\end{document}
答案1
考虑将嵌套放置theorem在具有适当宽度的 内minipage（\linewidth）。此装箱可避免错误。添加一些额外的间距以匹配周围的布局。
\documentclass{article}
\usepackage{amsthm,framed}
\usepackage{lipsum}
% Custom environment, with vertical bar to the left of text
\newtheorem{theoremzz}{Theorem}
\newenvironment{theorem}[1][]{\begin{theoremzz}[#1]\begin{leftbar}}{\end{leftbar}\end{theoremzz}}
% default environment
\newtheorem{proposition}[theoremzz]{Proposition}
\begin{document}
\begin{enumerate}
\item I want my custom \texttt{theorem} environment inside this item of the list.
\vspace{\topsep}
\begin{minipage}{\linewidth}
\begin{theorem}
\lipsum[1][1-4]
\end{theorem}
\end{minipage}
\vspace{\topsep}
As you can see, it worked as expected.
\item Now an attempt with a default \texttt{proposition} environment:
\begin{proposition}
\lipsum[2][1-4]
\end{proposition}
It works!
\end{enumerate}
\noindent Outside the list, the custom environment works:
\begin{theorem}
\lipsum[3][1-4]
\end{theorem}
\end{document}