Comment by thefaux

This is incredibly impressive but I also simultaneously find it kind of depressing. In my not so humble opinion, typescript is already way too complicated and getting worse thanks to its velocity. A better approach would be to kill typescript's velocity by identifying a stable subset of the language that provides the vast majority of its benefits and optimize the heck out of a parser for that smaller language. This approach would be both easier and more sustainable since it would cap the language complexity making it easier to maintain and/or write alternative implementations.