[TeX] \overset not preventing movable limits

[pkra]

This is basically #1929, but for v3.

On mathjax.org#demo (and also with the develop branch), \( \overset{a}{\prod }\) will render the a as a superscript (which it shouldn't).

[pkra]

It seems like the moveable limits check in

https://github.com/mathjax/MathJax-src/blob/5650c74c4d1102e96ae081bd76c90b87c617394f/ts/input/tex/base/BaseMethods.ts#L619-L633

doesn't quite work. Replacing it with the one from underover seems to do the job.

[dpvc]

Thanks for the report. It looks like the condition for \overset is not the same as for \underset or \overunderset, and they differ from the one used in the ParserUtil.underOver() method. unfortunately, your suggested solution isn't quite right, either. For one thing, you have left off the check for the movablelimits property on the node itself (which is important), and the check you are doing assumes the base is an mo element, which it may not be here.

I will push a branch that makes a utility function for making the check, and use it in all four places.