[luatex] open math constants leaks out?

[Ulrike Fischer]

I tried to find out why using Linux Libertine in math leads to wrong
spacing in the limits of an integral
(http://tex.stackexchange.com/q/326588/2388)

Imho the reason is that linlibertine_R has a mathconstants table. 
When using the font in math something is leaking out and affects
legacy math. This plain tex example demonstrates the problem (tested
in texlive 2016)

\input luaotfload.sty

\font\test={Linux Libertine O}

$$ \int_{a}^{a} $$

\textfont4=\test

$$ \int_{a}^{a} $$

\bye

Is this a bug? And what exactly happens that luatex changes the
spacing?


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/