Comment by messe 19 hours ago
> The one thing you could say is that using some kind of token makes it dead simple to have different tokens. But that's really not something I run into often at all when using async.
It's valuable to library authors who can now write code that's agnostic of the users' choice of runtime, while still being able to express that asynchronicity is possible for certain code paths.
But you can't call it from synchronous rust. Zig is moving toward all sync code also using the Io interface.
yes, you can:
runtime.block_on(async { })
Let me rephrase, you can't call it like any other function.
In Zig, a function that does IO can be called the same way whether or not it performs async operations or not. And if those async operations don't need concurrency (which Zig expresses separately to asynchronicity), then they'll run equally well on a sync Io runtime.
Here's a problem with that:
Cannot start a runtime from within a runtime. This happens because a function (like `block_on`) attempted to block the current thread while the thread is being used to drive asynchronous tasks.
But that can already be done using async await. If you write an async function in Rust for example you are free to call it with any async runtime you want.