Hyperref's Autoref When Using the Same Counter for Theorems, Lemmas, Etc

Question

First, apologies if this is a duplicate: I have genuinely searched for the question, but haven't been able to find it!

I am using the same counter for my theorems, lemmas, propositions, etc. I want to use \autoref (or another package) in the following way: upon calling \autoref{result1}, I get back Theorem 1, but upon calling \autoref{result2} I get Lemma 2. This probably isn't particularly clear, so I've put in a MWE, using autoref and cleveref. In both cases, I always get the word 'Theorem' where I want 'Lemma'.

\documentclass[]{article}
\usepackage[UKenglish]{babel}
\usepackage{hyperref, cleveref}

\newtheorem{thm}     {Theorem}
\newtheorem{lem}[thm]{Lemma}
\def\thmautorefname{Theorem}
\def\lemautorefname{Lemma}

\begin{document}

\begin{thm} \label{T1}  Theorem 1... \end{thm}
\begin{lem} \label{L2}  Lemma 2... \end{lem}

\autoref{T1} \autoref{L2}

\Cref{T1} \Cref{L2}

\end{document}

I want the output to be "Theorem 1 Lemma 2", but at the moment it's "Theorem 1 Theorem 2".

Answer 1

Elaborating on my comment, for cleveref the names in \cref's are correct if you use the amsthm package:

\documentclass{article}

\usepackage[UKenglish]{babel}

\usepackage{amsthm,hyperref,cleveref}

\newtheorem{thm}     {Theorem}
\newtheorem{lem}[thm]{Lemma}

\begin{document}

\begin{thm} \label{T1}  Theorem 1\dots \end{thm}
\begin{lem} \label{L2}  Lemma 2\dots \end{lem}

\Cref{T1} \Cref{L2}

\end{document}

You also get correct names if you use the thmtools or the ntheorem package instead of amsthm. Even better the thmtools package also corrects hyperrefs \autoref command:

\documentclass{article}

\usepackage[UKenglish]{babel}

\usepackage{thmtools,hyperref,cleveref}

\newtheorem{thm}     {Theorem}
\newtheorem{lem}[thm]{Lemma}

\begin{document}

\begin{thm} \label{T1}  Theorem 1\dots \end{thm}
\begin{lem} \label{L2}  Lemma 2\dots \end{lem}

\autoref{T1} \autoref{L2}

\Cref{T1} \Cref{L2}

\end{document}

When experimenting remember to compile twice to see the effect of a package change, as a first run of latex puts information about these labels in the .aux file, which is then read on the second run for use in the referencing commands.

Answer 2

Using shared counters for the lemma etc. can be tricky -- neither \cref nor \autoref know which counter is refstepped internally, so both assume thm here.

With the package aliascnt a name alias for an existing counter can be defined, say \newaliascnt{lem}{thm}.

In conjunction with \newtheorem \aliascntresetthe{lem} must be used.

\documentclass[]{article}
\usepackage[UKenglish]{babel}
\usepackage{aliascnt}
\usepackage{hyperref, cleveref}

\newtheorem{thm}{Theorem}
\newaliascnt{lem}{thm}
\newtheorem{lem}[lem]{Lemma}
\aliascntresetthe{lem}
\def\thmautorefname{Theorem}
\def\lemautorefname{Lemma}

\begin{document}

\begin{thm} \label{T1}  Theorem 1... \end{thm}
\begin{lem} \label{L2}  Lemma 2... \end{lem}

\autoref{T1} \autoref{L2}

\Cref{T1} \Cref{L2}

\end{document}