# Blank left and right delimiters produce an unknown symbol

I recently compiled one of my files after updating my TeX distribution (including the unicode-math package, as I use the MinionMath font set) and noticed a strange error. In my file I used a cases environment, and for some reason an unknown symbol was printed at the end of the environment. Here is a minimal example. When I input

\begin{equation*}
f(x) \colonequals
\begin{cases}
1, & x ≤ 1  \\
x, & x ≥ 1
\end{cases}
\end{equation*}

it produces the following:

The same problem occurs when using the \left. and \right. blank delimiters, so I think that it's ultimately a problem with the delimiters. I was wondering if there's a way to make this unknown symbol go away.

I'm using the TeXLive distribution and compiling with XeLaTeX. Here's how I've loaded the fonts (which hasn't been a problem in the past 6 months).

\usepackage[math-style=ISO]{unicode-math}
\setmainfont[Numbers={OldStyle}, Ligatures={Common}, ItalicFont={Minion Pro Italic}, BoldFont={Minion Pro Semibold}, BoldItalicFont={Minion Pro Semibold Italic}]{Minion Pro}
\setmonofont{Exemplar Pro}
\setmathfont[
Extension = .otf,
Scale = 1,
Script = Math,
SizeFeatures = {
{Size = -6, Font = MinionMath-Tiny,
Style = MathScriptScript},
{Size = 6-8.4, Font = MinionMath-Capt,
Style = MathScript},
{Size = 8.4-13, Font = MinionMath-Regular,
Style = MathScript},
{Size = 13-19.9, Font = MinionMath-Subh,
Style = MathScript},
{Size = 19.9-72, Font = MinionMath-Disp},
{Size = 72-, Font = MinionMath-Disp,
Style = MathScript},
},
]{MinionMath-Regular}
\setmathfont[range={\mathfrak}]{xits-math.otf}
\setmathfont[range={\mathcal}]{xits-math.otf}
\setmathfont[range={\mathit}]{MinionMath-Regular.otf}

I'm using the amsart documentclass.

• Welcome to TeX.SE. Please state which TeX distribution and which LateX format (pdfLaTeX, LuaLaTeX, something else?) you use. Also, how are the text and math fonts loaded? – Mico Aug 27 '15 at 6:02
• Minion Math is a commercial font and not available for the public and package unicode-minionmath is not on CTAN and, of course, provide a complete example which shows the behaviour. – user2478 Aug 27 '15 at 6:30
• Yeah, I just took that line off; just a copy/paste error. In any case that shouldn't be the problem. – Peter Haine Aug 27 '15 at 6:34

The following example with up-to-date TeXLive works well:

\documentclass{amsart}
\usepackage{colonequals}
\usepackage[math-style=ISO]{unicode-math}
\setmainfont[Numbers=OldStyle]{Minion Pro}
\setmathfont{MinionMath-Regular}
\setmathfont[range={\mathfrak,\mathcal}]{XITS Math}
\begin{document}

foo \textit{bar} \textbf{baz}

\begin{equation*}
f(x) \colonequals
\begin{cases}
1, & x ≤ 1  \\
x, & x ≥ 1
\end{cases}
\end{equation*}

\end{document}
• Strange...In previous versions I needed to have the line \setmathfont[range={\mathit}]{MinionMath-Regular.otf} at the end to get the spacing to work correctly, but removing it removed the error. – Peter Haine Aug 27 '15 at 6:48