[texhax] strange behavior of \shoveleft or \shoveright

[Victor Ivrii]

 \shoveleft applied to the first line in multline (or  multline*)
shifts it to the right
\shoveright applied to the first line in multiline (or multline*)
shifts it to the left

while they should not have any effect (so nobody needs to apply them)
! This is in bot [reqno] and [leqno] modes and {mathtools}  do not
change this behaviour.

Victor

\documentclass[12pt]{article}
\usepackage{amsmath}

\begin{document}

\begin{multline}
\shoveleft{12345678912345678234567123456789123456782345671}\\
\shoveright{12345678912345678234567123456789123456782345671}
\end{multline}


\begin{multline}
{12345678912345678234567123456789123456782345671}\\
\shoveright{12345678912345678234567123456789123456782345671}
\end{multline}


\begin{multline}
\shoveleft{12345678912345678234567123456789123456782345671}\\
{12345678912345678234567123456789123456782345671}
\end{multline}
\begin{multline}
{12345678912345678234567123456789123456782345671}\\
{12345678912345678234567123456789123456782345671}
\end{multline}

\end{document}