Equation number referral doesn't appear within the empheq/array environment?

Question

Why doesn't the equation number referral appear within the empheq/array environment ? In this example I left out the formulas within the empheq environment (the problem remains with the formulas added).

\documentclass{article}
\usepackage{amsmath}
\usepackage{empheq}

\begin{document}

\begin{empheq}{align}
\label{eq:1}
\left\{\!\!\begin{array}{l}
\text{An equation reference should appear after the question mark, but doesn't ? \eqref{eq:2}}\\
\text{This doesn't work either : \eqref{eq:2}}
\end{array}\right.
\end{empheq}

I can definitely refer to the equation though, like this : \eqref{eq:2}.

\begin{empheq}{align}
\label{eq:2}
1+1=2
\end{empheq}


It compiles without throwing an error.

\end{document}

Answer 1

The problem goes away if you use (\ref{whatever}) in place of \eqref{whatever}. I have no idea why this happens, though.

Answer 2

The main problem is that empheq redefines \maketag@@@ because it need to separate the display from the eqn numbers. But \eqref also make use of this macro to typeset the reference to an eqn numbers. The fix below seem to do the trick and will be build into the next empheq release

\makeatletter
\MHInternalSyntaxOn
\renewenvironment{empheq}[2][]{%
  \let\savedmaketag\maketag@@@
  \renewcommand\eqref[1]{\textup{%
      \let\maketag@@@\savedmaketag%
      \tagform@{\ref{##1}}}%
  }
  \setkeys{EmphEqEnv}{#2}\setkeys{\EQ_options_name:}{#1}%
  \EmphEqMainEnv}{\endEmphEqMainEnv}
\MHInternalSyntaxOff
\makeatother