Comment by flohofwoe

> But then it means if you use that IO instance with the magic then your function gets transformed into a state machine?

This was essentially like the old async/await implementation in Zig already worked. The same function gets the state-machine treatment if it was called in an async context, otherwise it's compiled as a 'regular' sequential function.

E.g. at runtime there may be two versions of a function, but not in the code base. Not sure though how that same idea would be implemented with the new IO interface, but since Zig strictly uses a single-compilation-unit model the compiler might be able to trace the usage of a specific IO implementation throughout the control flow?