\leavevmode cause overlay of labels in description list

Question

I have a description list at the beginning of a proof environment and want the first label to begin in the same column as the remaining labels. When I put a \leavevmode before the first \item, the label for the first item overlays the label for the second item.

\documentclass{article}
\usepackage{amsmath}
\usepackage{amsthm}

\theoremstyle{definition}

\theoremstyle{remark}

\numberwithin{equation}{section}

\usepackage[colorlinks,hidelinks,draft=false]{hyperref}

\usepackage{cleveref}

% \newtheorem must follow cleveref
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}[theorem]{Corollary}
\def\corollaryautorefname{Corollary}         % Needed for \autoref
\newtheorem{definition}[theorem]{Definition}
\def\definitionautorefname{Definition}       % Needed for \autoref
\newtheorem{example}[theorem]{Example}
\newtheorem{lemma}[theorem]{Lemma}
\def\lemmaautorefname{Lemma}                 % Needed for \autoref

\newtheorem{remark}[theorem]{Remark}
\newtheorem{xca}[theorem]{Exercise}
\usepackage[draft]{showlabels}
\showlabels{cite}
\showlabels{cref}
\showlabels{crefrange}

\begin{document}
\begin{theorem}
foo
\begin{proof}
\begin{description}
\leavevmode
\item[prop1:]
proof of prop1.
\item[prop2:]
proof of prop2
\end{description}
\end{proof}
\end{theorem}
\end{document}

Answer 1

A latex list should only have items preceded by \item. \leavevmode is a syntax error, what is the intention?

If you want a "normal" paragraph to hole the proof label before the list starts you could put \leavevmode (or \mbox{} would be better LaTeX) before the

\begin{description}

Not after it.