Self defined alph list breaks when enumitem is used

Question

Please see the following MWE. (Written in light of this answer.)

\documentclass{article}

\usepackage{polyglossia}
\usepackage{fontspec}
% Bangla
\setmainlanguage[numerals=Bengali, changecounternumbering=true]{bengali}
\newfontfamily\bengalifont[Script=Bengali,AutoFakeBold=4.0,AutoFakeSlant=0.4]{SolaimanLipi}
\newfontfamily\bengalifontbf[Script=Bengali,AutoFakeBold=4.0,AutoFakeSlant=0.4]{SolaimanLipi}
\newfontfamily\bengalifonttt[Script=Bengali,AutoFakeBold=4.0,AutoFakeSlant=0.4]{SolaimanLipi}
\newfontfamily\bengalifontsf[Script=Bengali,AutoFakeBold=4.0,AutoFakeSlant=0.4]{SolaimanLipi}

\setotherlanguage{english}
\defaultfontfeatures{Ligatures=TeX}

% Times New Roman used
\newfontfamily\englishfont[Mapping=tex-text, Ligatures=TeX]{Times New Roman}

\renewcommand\theenumi{\bngl{enumi}}

% alph lists for Bengali, bngl
\makeatletter
\def\bngl#1{\expandafter\@bngl\csname c@#1\endcsname}
\def\@bngl#1{%
  \ifcase#1\or
  ক\or
  খ\or
  গ\or
  ঘ\or
  ঙ\or
  চ\or
  ছ\or
  জ\or
  ঝ\else\@ctrerr\fi}
\makeatother

% \usepackage{enumitem}

\begin{document}

\begin{enumerate}
\item এক
\item দুই
\item তিন
\item চার 
\end{enumerate}

\end{document}

The above code works fine and produces the expected results.

But breaks as soon as the enumitem package line is uncommented.

Is there any way I can use both my defined \bngl and enumitem?

Answer 1

You must made the counter known to enumitem. I remove your font (that I don't have) as the actual content of your counter is not relevant:

\documentclass{article}
\usepackage{enumitem}

\makeatletter
\def\bngl#1{\expandafter\@bngl\csname c@#1\endcsname}

\def\@bngl#1{%
  \ifcase#1\or
  AA\or %adapt to your liking
  BB\or
  CC\or
  DD\or
  EE\or
  FF\or
  GG\or
  HH\or
  II\else\@ctrerr\fi}

\AddEnumerateCounter\bngl\@bngl{m} %make the counter known to enumitem
\makeatother

\setlist[1,enumerate]{label=\bngl*}
\begin{document}

\begin{enumerate}
\item test
\item test
\item test
\item test
\end{enumerate}

\end{document}