That is interesting, I did not know that.
Still, I don't want to use TypeScript for the reasons I wrote. I'm as minimalist as possible, and I don't want to use a language that changes my code to something else without any gain for me since I can write exactly what I want in ES 2015+ already. So it's just those types, and I could get them from "Flow" too and in that case keep my ES 2015+ code. Yes I know TypeScript is very close to ES 2015+, but I never know when it does change the code unless I look at the transpiled result.
EDIT: Actually, I did know that, looking at that page I remember why I dismissed it:
> Note any tags not listed explicitly below (such as @typedef, or @constructor) are not yet supported.
But that is something I make heavy use of. It would be really messy if I wasn't able to introduce "custom types" even in my limited "IDE based static type system".