Async-await on stable Rust
This is a big improvement, however this is still explicit/userland asynchronous programming: If anything down the callstack is synchronous, it blocks everything. This requires every components of a program, including every dependency, to be specifically designed for this kind of concurency.<p>Async I/O gives awesome performance, but further abstractions would make it easier and less risky to use. Designing everything around the fact that a program uses async I/O, including things that have nothing to do with I/O, is crazy.<p>Programming languages have the power to implement concurrency patterns that offer the same kind of performances, without the hassle.