google's really been sidelined for front-end tech across the board: it's all written in microsoft's language, in microsoft's editor, with facebook's framework, whereas dart, clojure compiler, angular are all withering away. does not seem like google wants to compete.

typescript is both supremely complex, and it's also (afaik) not based on a formal specification but rather the behavior of the typescript compiler / checker is the definition of what typescript is. the lack of a second implementation matters a lot or not at all depending.

the context is that most parts of the 'web development stack' have gotten a lot of competing implementations, a lot of them fast and in rust with lots of competition. the typescript type checker has not, there was one attempt to write another version and it fizzled.