Numberwithin with enumitem 2

Question

Following topic1 and topic2, I've implemented Mico's answers. Now, I want to reference equations under this enumeration too. For instance,

\documentclass{article}
\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{enumitem,cleveref}

\newlist{myenum}{enumerate}{3}
\setlist[myenum,1]{label=\textbf{\arabic*.},
                   ref  =\arabic*}
\setlist[myenum,2]{label=\textbf{(\alph*)},
                   ref  =\themyenumi.(\alph*)}
\setlist[myenum,3]{label=\bfseries(\roman*),
                   ref  =\themyenumii.(\roman*)}

\numberwithin{equation}{myenumi}

\begin{document}

\begin{myenum}
\item 
   \begin{equation}\label{eq:euler}
      e^{i\pi}+1 = 0
   \end{equation}
\end{myenum}

As shown in \cref{eq:euler}.

\end{document}

However, these lines got me this error: "Missing \endcsname inserted. \begin{equation}". Any ideas about why is this happening and/or how to solve this? Thanks.

Edit: I've discovered that this occurs when including the \usepackage{hyperref} line.

Answer 1

I suspect you've encountered an incompatibility between the enumitem and hyperref packages. I'm afraid I'm not in a position to offer a full fix. All I can suggest is that you not use the enumitem package and, instead, modify the low-level macros \theenumi, \labelenumi, \theenumii, \labelenumii, \p@enumii, etc.

\documentclass{article}
\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{cleveref}

\renewcommand{\theenumi}{\arabic{enumi}}
\renewcommand{\theenumii}{(\alph{enumii})}
\renewcommand{\theenumiii}{(\roman{enumiii})}
\renewcommand{\labelenumi}{\textbf{\theenumi.}}
\renewcommand{\labelenumii}{\textbf{\theenumii}}
\renewcommand{\labelenumiii}{\textbf{\theenumiii}}
\makeatletter
\renewcommand\p@enumii{\theenumi} % "prefixes" for use in cross-references
\renewcommand\p@enumiii{\theenumi\theenumii}
\makeatother

\numberwithin{equation}{enumi}

\begin{document}

\begin{enumerate}
\item 
   \begin{equation}\label{eq:euler}
      e^{i\pi}+1 = 0
   \end{equation}
\end{enumerate}

As shown in \cref{eq:euler}, \dots
\end{document}