[honua]

I was wanting the same kind of thing! We have an old Node (lol, funny to write that) code base of about 60 services that fetch data from 3rd party APIs. They're all very dis-organized and written in different styles, so a tool like that would be really useful. I've been experimenting with using Facebook's Flow on this, but it doesn't do the magic that you describe (which I'd like)

[smt88]

The good thing about TS is that you can add types gradually. I actually think there's a lot of value in adding the typing manually because A) you're guaranteed to find bugs, and B) you have to revisit your assumptions with the advantage of hindsight.

[clarus]

With Flow you can also add types gradually. Actually, one of the reasons why Facebook created Flow is that they thought that TypeScript was not "gradual enough". A good presentation on how Flow differs from other type systems: https://www.youtube.com/watch?v=VEaDsKyDxkY