Actually it seems like they just colored everything async and you pick whether you have worker threads or not.

I do wonder if there's more magic to it than that because it's not like that isn't trivially possible in other languages. The issue is it's actually a huge foot gun when you mix things like this.

For example your code can run fine synchronously but will deadlock asynchronously because you don't account for methods running in parallel.

Or said another way, some code is thread safe and some code isn't. Coloring actually helps with that.

> Actually it seems like they just colored everything async and you pick whether you have worker threads or not.

There is no 'async' anywhere yet in the new Zig IO system (in the sense of the compiler doing the 'state machine code transform' on async functions).

AFAIK the current IO runtimes simply use traditional threads or coroutines with stack switching. Bringing code-transform-async-await back is still on the todo-list.

The basic idea is that the code which calls into IO interface doesn't need to know how the IO runtime implements concurrency. I guess though that the function that's called through the `.async()` wrapper is expected to work properly both in multi- and single-threaded contexts.