We want the type-safety of TypeScript, without having to rewrite everything. Thankfully, TypeScript (quietly) added support for checking .js files with JSDoc in TypeScript 2.3
We already have the JSDoc effort underway - we’re working on it right now on this stream!
There are XPCOM / WebIDL pieces we need to figure out
There is pathing to figure out
But this was recently piloted, and logic bugs were found and fixed