See:
https://rjlipton.wpcomstaging.com /2015/03/08/lint-for-math/
https://news.ycombinator.com/item?id=9168531
One could imagine TeXmacs having such a lint that works in the background as you type up your paper and highlights likely math errors much like Word highlights likely grammar errors.
I think this would make WYSIWYG editing of math documents more compelling.
TeXmacs checks the syntax of math formulas and tell you when there is a problem with a red box. You get a green box if everything is all-right, i.e. if your formula parses correclty. You can activate it by selecting “semantic editing”. Joris made a presentation about it some years ago: https://www.texmacs.org/joris/2011/magixalix2/magixalix2-abs.html
Such a lint could go beyond syntactic correctness.
I understand. Probably for very simple formulas (and trivial mistakes it could work). Note however that it is not an “hobby” project and the effort to put into that vs. its usefulness is questionable. Probably it will be able to catch simple mistakes, but not less obvious ones, and therefore is useless for a professional mathematician, and harmful for a non-professional one since it will allow you to be less careful in what you are doing. Just a different kind of project, not really an extension of TeXmacs. I do not see how this would make WYSIWYG more compelling since a similar system can certainly work for math entered in LaTeX (modulo weird macro definitions).
Maybe not so much WYSIWYG but more advanced editing environments in general where you can get feedback in the editor in real-time as you type.