[Bug]: mathtext silently ignores content after mismatched opening brace #26510

Bug summary

All's in the title.

Code for reproduction

from pylab import *; figtext(.5, .5, r"$a={a$")

Actual outcome

"a = " is printed.

Expected outcome

An exception is thrown.

Additional information

This appears at least as far back as 3.5, so is unlikely to come from the recent mathtext work.

Operating system

macos

Matplotlib Version

3.8.0.dev1801+g5d5700a99e

Matplotlib Backend

any

Python version

3.11.3

Jupyter version

No response

Installation

git checkout