That's an interesting hybrid approach, thanks Andrea.

Is this what Svelte will use? (Asking anybody that knows, of course.)

Anyway, to me the main problem in using TS with libraries is that we have 3-4 major releases per year, and they're just too many. Unless one takes a very restrained approach, releasing very generic (and thus less helpful) types that won't (presumably) break future (or past) versions of TypeScript, we need to release with `typesVersions` targetting n different versions of TypeScript. That's an ever-growing bother indeed for maintainers as time passes.

And I fear the hybrid approach above won't escape this issue. So using "pure" JSDoc or JSDoc with just a sprinkle of TypeScript actually makes sense... But I'd expect this workflow to be winning with smaller projects, and that's why this announcement for Svelte has been surprising to me.