Number equations like subsections

Question

I would like for equations to share the same counter as subsections. For example if my document is:

\documentclass{article}
\begin{document}
\section{A}
\begin{equation} 1+1=2 \end{equation}
\subsection{X}
\begin{equation} 1+1=2 \end{equation}
\begin{equation} 1+1=2 \end{equation}
\subsection{Y}
\begin{equation} 1+1=2 \end{equation}
\end{document}

I would like this output (produced here through a sneaky use of \tag):

Something similar to how theorems of amsthm can be "siblings" with another counter. I am aware of the \numberwithin command of amsmath, but this is not what I want. I am also aware of the aliascnt package, but since "equation" is an existing counter, it doesn't work.

Answer 1

I hope, this is what you want:

\documentclass{article}
\pagestyle{empty}% for cropping
\makeatletter
\let\c@equation=\c@subsection
\let\theequation=\thesubsection
\makeatother
\begin{document}
\section{A}
\begin{equation}
    1+1=2
\end{equation}
\subsection{X}
\begin{equation}
    1+1=2
\end{equation}
\begin{equation}
    1+1=2
\end{equation}
\subsection{Y}
\begin{equation}
    1+1=2
\end{equation}
\end{document}