Conflict between TikZ and *.cls file

Question

I am attempting to convert a document from one class to another. In the original class, I am able to use TikZ and PGFPlots for my graphics. However, in the new class, I receive the following error:

! Missing number, treated as zero.
<to be read again> 
                   }
l.51 \section{Introduction}
                       

If I remove all of the \section{} commands, the document compiles fine. Furthermore, the \section*{} commands do not cause an error.

The class .cls file for which I am experiencing the errors can be found at: https://bitbucket.org/lgriffiths/lyx-classes/src/df41b5298566/_miktex_tex_latex/ifasd/ifasd.cls

MWE

\documentclass{ifasd}
\usepackage{lipsum}
\usepackage{tikz}
\begin{document}

\section*{Testing One}
\lipsum[1]

\section*{Testing Two}
\lipsum[2]

\section{Testing Three}
\lipsum[1]

\end{document}

Answer 1

There is an error in the specification for the section titles: the \MakeUppercase instruction should go in the last mandatory argument of \titleformat. Where it is now it doesn't make sense.

\titleformat{\section}[hang]
  {\normalsize\normalfont\bfseries}
  {\thesection}
  {6pt}
  {\MakeUppercase}

Answer 2

try

\documentclass{ifasd}
\usepackage{lipsum}
\usepackage{tikz}
\titleformat{\section}[hang]%
  {\normalsize\normalfont\bfseries\uppercase}%
  {\thesection}{6pt}{}
\begin{document}
[ ... ]

Answer 3

Whittling down ifasd, the following MWE has an apparent conflict between tikz (or pstricks) and how \MakeUppercase is being used:

\documentclass{article}
\usepackage{titlesec}
\titleformat{\section}[hang]%
  {\normalsize\normalfont\bfseries\MakeUppercase}%
  {\thesection}{6pt}{}
\pagestyle{empty}
\usepackage{lipsum}
\usepackage{tikz}
\begin{document}
\tableofcontents

\section{Testing One}
\lipsum[1]

\end{document}

Here's a bit of a work around until someone comes up with a better solution.

\documentclass{article}
\usepackage{titlesec}
\titleformat{\section}[hang]%
  {\normalsize\normalfont\bfseries}%
  {\thesection}{6pt}{}
%..%'
\usepackage{xparse}
\let\oldsection\section
\RenewDocumentCommand\section{ som }{%
    \IfBooleanTF{#1}
        {\oldsection*{#3}}
        {\IfNoValueTF{#2}
         {\oldsection{\MakeUppercase{#3}}}
         {\oldsection[#2]{#3}}}}
%..%'
\pagestyle{empty}
\usepackage{lipsum}
\usepackage{tikz}
\begin{document}
\tableofcontents

%\MakeUppercase This one
\section{Testing One}
\lipsum[1]

\end{document}

So, in terms of your class, you can write something along the lines of

\documentclass{ifasd}
%..%'
\usepackage{xparse}
\let\oldsection\section
\RenewDocumentCommand\section{ som }{%
    \IfBooleanTF{#1}
        {\oldsection*{#3}}
        {\IfNoValueTF{#2}
         {\oldsection{\MakeUppercase{#3}}}
         {\oldsection[#2]{#3}}}}
%..%'
\usepackage{tikz}
\usepackage{lipsum}
\begin{document}

\section*{Testing One}
\lipsum[1]

\section*{Testing Two}
\lipsum[2]

\section{Testing Three}{}
\lipsum[1]

\end{document}

provided you've gone into ifasd and removed the apparently confounding \MakeUppercase from the \titleformat commands.

The idea for writing \section this way is due to an answer by @egreg to a question of mine.