\documentclass[11pt, oneside]{article}
\pagestyle{plain}
\usepackage{amsfonts,amssymb,amsmath,amsthm,amstext}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{proposition}[theorem]{Proposition}
\usepackage{thmtools}
\usepackage{thm-restate}
\begin{document}
\section{Equations}
\begin{restatable}{theorem}{xyz}
$a = b = c.$
\end{restatable}
\begin{restatable}{proposition}{ab}
Let $a = b.$ Then $b = a.$
\end{restatable}
\section{The same equations}
New theorem.
\begin{theorem}
$a \neq d.$
\end{theorem}
Old theorems.
\xyz*
\ab*
\end{document}
I am using a restatable environment to repeat theorems. This works fine for {theorem}, but not for {proposition}. I would like to have the same numbering when restating a proposition (just like it happens for theorem).
Any help would be greatly appreciated, thank you.