[quodlibetor]

The nice thing about Rust not having Async IO built into the language is that arbitrary third-party implementations are possible on a level playing field with the async framework being developed by the core team.

For example, there is the May[1] concurrency library. It provides alternative implementations of the standard library's IO interface, but does Go's automatic suspend/resume, so it still looks like blocking code, which is nice. From what I can tell it's still early days on a one-person project, but it is interesting, at least.

[1]: https://blog.zhpass.com/2017/12/23/may-announcement/

[Rapzid]

Let me offer a counter point. Every language I have used that has gone the route of "let the community make their own concurrency libraries" has turned out a mess; specifically Ruby and Python.

On the other hand, the concurrency OOTB languages have all had much better ecosystems and experiences; C#, nodejs(now and w/TypeScript), F#, Golang, etc.

[barrkel]

"Batteries included" is almost always better than "level playing field" because of network effects. The larger the set of common types / protocols available, the higher up the abstraction stack interfacing between two unrelated third party components can be. Minimalist environments have to pay taxes in the form of glue code and adapters for different ways of representing the same underlying concepts (though the costs are reduced in duck-typed languages). Even worse things happen when you try and use two third-party components and they share different versions of a common dependency - sometimes there's no easy way out.

Inferior approaches sometimes do get baked in to standard libraries. Having a culture of versioning, deprecating, migrating, is better IMO. But it's even better again to do a really good job first time around. Not easy, but I didn't say it was!

[steveklabnik]

It also has possibly irreconcilable soundness issues :/

libfringe is another extremely interesting player in this space.

[stjepang]

I'd like to read more about those soundness issues - do you have a link?

[steveklabnik]

see https://github.com/Xudong-Huang/may/issues/6 as one example