[mpolichette]

I can empathize with the author here that types can be very challenging to get right, especially with high amounts of dynamism.

However, I think that saying it is "terrible for library developers" is a bit far. I think its terrible for developers who want to make use of advance types... which ultimately doesn't depend if you're a library dev at all.

It boils down to: "Typescript learning curve gets really steep after the basics"

The author mentions they help maintain redux-saga. I don't want to dig on them, but from my personal experience, that library takes you down quite an opinionated application path with complexity inherit to it. Heck, just making types for redux was a pain, let alone adding async and additional composability.

My take is that the author has chosen complex tech to work with, and that influences the complexity in their types.