Incorrect \underbrace output if used with mathtools

[zepinglee]

Description

The \underbrace command produces incorrect output if the mathtools package is loaded.

Add info or delete as appropriate:

• Relevant for XeTeX
• Relevant for LuaTeX
• Related issue: #169
• https://tex.stackexchange.com/q/521394/82731

Minimal example demonstrating the issue

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{STIXTwoMath-Regular.otf}
\usepackage{mathtools}
\begin{document}
\[
  \overbrace{a+b+c+d}^{e/f/g/h}
  \underbrace{a+b+c+d}_{e/f/g/h}
  \LaTeXoverbrace{a+b+c+d}^{e/f/g/h}
  \LaTeXunderbrace{a+b+c+d}_{e/f/g/h}
\]
\end{document}

Further details

• TeX Live 2021 with all packages up-to-date
• amsmath 2021/10/15 v2.17l
• unicode-math 2020/01/31 v0.8q
• mathtools 2021/04/12 v1.27

I'm sure if it's better for unicode-math to fix it rather than mathtools.

[zepinglee]

I suppose it should be fixed in mathtools.

\AtEndOfPackageFile*{mathtools}{
  \@ifpackageloaded{unicode-math}{
    \let\underbrace\LaTeXunderbrace
    \let\overbrace\LaTeXoverbrace
  }{}
}