misplaced qed symbol after displaymath inside item of inline list

Question

My problem involes a qed symbol which appears too early. My observations are that it happens after a displaymath inside an item of an unboxed inline list. All of this seems to be necessary to produce the error.

The packages involved are ntheorem, thmtools and enumitem.

If I compile this code with lualatex using TeXLive 2011.

\documentclass{scrreprt}

\PassOptionsToPackage{thmmarks}{ntheorem}
\PassOptionsToPackage{inline}{enumitem}

\usepackage{amsmath,MnSymbol}
\usepackage{ntheorem,thmtools}
\usepackage{
    enumitem,
}

\declaretheoremstyle[qed={\quad\blacksquare}]{plain}
\declaretheorem[style=plain,numbered=no,name=Proof]{proof}%

\begin{document}

\begin{proof}
  \begin{enumerate*}[mode=unboxed]
    \[a\]
    Still proof.
  \end{enumerate*}
\end{proof}

\end{document}

the output becomes:

The symbol is placed correctly if the enumerate* environment isn't used or if $$ or \begin{displaymath and \end{displaymath} is used to mark displaymath mode instead of \[ and \].

Clearly, the qed symbol should be at the end of the proof after “Still proof.” – What am I doing wrong? Couldn't find anything so far.

Answer 1

As per my earlier comment ntheorem seems to add the \qed to the very last display mode equation. So a hack is to to end a proof with

\vspace{-\belowdisplayskip}\[\]

Code:

\documentclass{scrreprt}

\PassOptionsToPackage{thmmarks}{ntheorem}
\PassOptionsToPackage{inline}{enumitem}

\usepackage{amsmath,MnSymbol}
\usepackage{ntheorem,thmtools}
\usepackage{
    enumitem,
}

\declaretheoremstyle[qed={\quad\blacksquare}]{plain}
\declaretheorem[style=plain,numbered=no,name=Proof]{proof}%

\begin{document}

\begin{proof}
  \begin{enumerate*}[mode=unboxed]
    \[a\]
    Still proof.
  \end{enumerate*}
  \vspace{-\belowdisplayskip}\[\]
\end{proof}
\end{document}

Answer 2

The problem is due to the use of the enumitem package.

Ntheorem supports a finite set of standard LaTeX environments. The algorithm consists of modifications to these environments to trace where the end mark belongs (for the implementation, see its documentation).

As there are dozens of packages that define own environments, it is not possible to support all of them.