Cleveref and tcolorbox for theorems that share a counter

Question

I'd like to have different theorem environments share the same counter using tcolorbox in beamer. However cleveref doesn't seem to pick up their names correctly. Can anyone point me to what I'm doing wrong?

Here's a MWE:

\documentclass[10pt,aspectratio=169]{beamer}

\usepackage{amsmath}
\usepackage{amsthm}

\usepackage[most]{tcolorbox}
\tcbuselibrary{theorems}

\usepackage{cleveref}
\crefname{lemma}{lemma}{lemmas}
\crefname{theorem}{theorem}{theorems}

\renewtcolorbox[use counter=theorem]{theorem}[1][]{
    title={\thetheorem. Theorem.},
    before upper={\tcbtitle\;\itshape},
    #1
    }

\renewtcolorbox[use counter=theorem]{lemma}[1][]{
    title={\thetheorem. Lemma.},
    before upper={\tcbtitle\;\itshape},
    #1
    }

\begin{document}

\begin{frame}{Blah}
    \begin{theorem}[label=bar]
        Blah blah.
    \end{theorem}
    \cref{bar}

    \begin{lemma}[label=foo]{}{}
        Blah blah.
    \end{lemma}
    \cref{foo}
\end{frame}

\end{document}

Which produces:

I would like "lemma 2" instead of "theorem 2". I tried adding label type = lemma as suggested here, but without any success.

Answer 1

beamer is quite peculiar in it's treatment of cross-referencing but, if you are willing to use zref-clever, and do some setup, you may get away with the following:

\documentclass[10pt,aspectratio=169]{beamer}

\usepackage{amsmath}
\usepackage{amsthm}

\usepackage[most]{tcolorbox}
\tcbuselibrary{theorems}

% Create 'zlabel' and 'zlabel type' options for tcolorbox.
\tcbset{%
  zlabel/.style={phantom={\zlabel{#1}}},%
  zlabel type/.code={\zcsetup{reftype={#1}}},%
}

\usepackage{zref-clever}

% From "Work-around 2: beamer" in zref-clever's User manual
\makeatletter
\RenewDocumentCommand{\zlabel}{ D<>{1} m }{%
  \ifx\label\ltx@gobble
  \else
    \zref@wrapper@babel{\zref@label<#1>}{#2}%
  \fi
}
\NewCommandCopy\beamer@old@zref@label\zref@label
\RenewDocumentCommand{\zref@label}{ D<>{1} m }{%
  \alt<#1>{%
    \zref@ifpropundefined{anchor}{}{\zref@setcurrent{anchor}{#2}}%
    \beamer@old@zref@label{#2}%
    \beamer@nameslide{#2}%
  }{%
    \beamer@dummynameslide%
  }%
}
\makeatother

\renewtcolorbox[use counter=theorem]{theorem}[1][]{
    title={\thetheorem. Theorem.},
    before upper={\tcbtitle\;\itshape},
    #1
    }

\renewtcolorbox[use counter=theorem]{lemma}[1][]{
    title={\thetheorem. Lemma.},
    zlabel type={lemma},
    before upper={\tcbtitle\;\itshape},
    #1
    }

\begin{document}

\begin{frame}
  \zcref{bar,foo}
\end{frame}

\begin{frame}{Blah}
  \begin{theorem}[zlabel=bar]
    Blah blah.
  \end{theorem}
  \zcref{bar}

  \begin{lemma}[zlabel=foo]
    Blah blah.
  \end{lemma}
  \zcref{foo}
\end{frame}

\end{document}