Conflict of mathtools and amsmath?

Question

I was using this template: https://www.overleaf.com/latex/templates/university-of-michigan-dissertation-template-unofficial/tpnjzndnrzmf

As long as I add \usepackage{mathtools} in package.tex, there is a "!" after Appendices.

I suspect this is because of the conflict between mathtools and amsmath after reading this: mathtools vs amsmath

But even if I comment out \RequirePackage{amsmath} in thesis-umich.cls, the problem is still present. How can I fix this problem?

Answer 1

The problem has nothing to do with mathtools it self, but rather to it loading the calc package`. So we can reduce the problem to

\documentclass{thesis-umich} 
\usepackage{calc} 
\begin{document} 
test  
\appendix  
test 
\end{document}

which produces the error

! Undefined control sequence.
\@calc@post@scan ...st@scan \else \def \calc@next 
                                                  {\calc@error #1}\fi \fi \f...
l.11 \appendix

When using Overleaf, please never ever ignore compilation errors. Overleaf, like many LaTeX editors run in a mode that tries to complete the compilation even if there are errors. This may cause issues in the PDF with things not being typeset correctly. Often a single error causes many others ...

The problem her is this definition in thesis-umich.cls

\renewcommand{\appendix}{ %
 % Move to new page.
 \clearpage %
 % Renew the counters.
 \renewcommand*{\thechapter}{\Alph{chapter}} %
 % Start over the chapter counter.
 \setcounter{chapter}{0} %
 % Add a pdf anchor.
 \phantomsection %
 % Add blank space to table of contents
 \addtocontents{toc}{\vspace{3.9ex}}
 % Add the page to the table of contents.
 \addcontentsline{toc}{backchapter}{Appendices}
 % Stop adding sections to the table of contents.
 \addtocontents{toc}{\setcounter{tocdepth}{1}} %
 % Header for appendices.
 \renewcommand{\@chapapp}{APPENDIX} %
 % Renew the chapter and section labels.
 \let\@chapter\@chapter@appendix %
}

especially the line

\addtocontents{toc}{\setcounter{tocdepth}{1}} %

whenever calc is loaded, \setcounter becomes a fragile command, and this it needs protection (from premature expansion) when being written to a file.

So here the fix is to add this to your preamble (don't change the cls file, rather send those maintaining it a message and ask them to fix it).

\makeatletter
\renewcommand{\appendix}{ %
 % Move to new page.
 \clearpage %
 % Renew the counters.
 \renewcommand*{\thechapter}{\Alph{chapter}} %
 % Start over the chapter counter.
 \setcounter{chapter}{0} %
 % Add a pdf anchor.
 \phantomsection %
 % Add blank space to table of contents
 \addtocontents{toc}{\vspace{3.9ex}}
 % Add the page to the table of contents.
 \addcontentsline{toc}{backchapter}{Appendices}
 % Stop adding sections to the table of contents.
 \addtocontents{toc}{\protect\setcounter{tocdepth}{1}} % <-----
 % Header for appendices.
 \renewcommand{\@chapapp}{APPENDIX} %
 % Renew the chapter and section labels.
 \let\@chapter\@chapter@appendix %
}
\makeatother