I’m a long time fan of TS, but I think this is a very exciting decision —- I have always been of the opinion any reasonably large project should workout a doubt use TS, so hearing about how this goes for them in 2/5/10 years in terms of how easily people are able to maintain code they didn’t create, how readily large refactorings can be made, how often runtime type errors occur (not just the literal TypeError, but all the things TS can catch, like null checks, index typing checks, etc) will be quite interesting.

I wish them luck!

One note of concern though: in their design doc they say incremental compilation is the number one problem and list multi-minute compile times. That’s huge! I wouldn’t use TS either of it took minutes to compile my projects. However, I think there’s room for improvement in their tooling if they took some time to explore what other large TS projects do instead of just giving up on it entirely —- VSCode for instance has incremental compilation in hundreds of ms or less.