Can we discuss whether there should be a coroutine <=> thread mapping? I think it should be explicit and user-controlled. Otherwise performance guarantees can be hard to establish (consider NUMA cache optimization.)

Also, I suggest being a little careful with the Go analogy since Go channels are built on mutex locking, and are typically used as a synchronization device. I'm not that familiar with lock-free queues, but wouldn't they be non-blocking? I.e., no "await" or blocking "select" or "for _ = range x" or whatnot.

The coroutines and thread mapping is entirely in userland and will be an option that std.event.Loop provides.

The implementation is lock free but it integrates with coroutines, and the get() and put() functions of Channel are async. So you define the channel buffer size (possibly zero) and that many put() awaits will resolve immediately. The next put() await will resume when the next get() completes.

So it still acts like a synchronization device, with async/await.

Exiting news !

FWIW, I think this broke the self-hosted build on my Mac.

$ ./bin/zig build --build-file ../build.zig
/Users/isaachier/proj/zig/zig/src-self-hosted/module.zig:270:62: error: expected type 'BuildError', found '@typeOf(Module_addRootSrc).ReturnType.ErrorSet'
                await (async self.events.put(Event{ .Error = err }) catch unreachable);
                                                             ^
/Users/isaachier/proj/zig/zig/src-self-hosted/module.zig:262:48: note: called from here
        _ = try async<self.a()> self.buildAsync();
                                               ^
/Users/isaachier/proj/zig/zig/build/lib/zig/std/os/path.zig:1158:43: note: 'error.NotSupported' not a member of destination error set
                    posix.ENOTSUP => error.NotSupported,
                                          ^
The following command exited with error code 1: ...

can you try this?

--- a/src-self-hosted/module.zig
+++ b/src-self-hosted/module.zig
@@ -115,6 +115,7 @@ pub const Module = struct {
         InputOutput,
         NoStdHandles,
         Overflow,
+        NotSupported,
     };
 
     pub const Event = union(enum) {

I'll clean this up soon.

That did the trick!