Earlier quoted context omitted.
It feels a little bit like if you'd want a linter to be part of an ES spec. As in: I appreciate TypeScript for the compile-time guarantees it gives me.
A good comparison here is the Python approach: Python 3 made the syntax for type annotations a first-class part of the language but only to the point of parsing that syntax and providing an AST, it did not (and at least for now will not) define "compile time" or "run time" meanings for them. The immediate benefit to adding Typescript/Flow-like annotations to the ES spec would be that you could run Typescript files un…
That makes sense. I can also imagine not wanting to start too quickly with that though, to learn what such a syntax would have to support from Flow and TypeScript.