TypeScript is the most complex type system in existence. I am unsurprised it is difficult to port, but I am still a bit surprised by the length of the project thus far.
You plan to contribute to the TypeScript project?
However they did mention this in the article, and hopefully that also means they'll make the package accessible to others too:
> The watcher is a self-contained package that has allowed us to keep a clean separation of concerns between what we care to watch and why.
amazing
