Hi @nine-fox , welcome to Ziggit.
I think you will have a hard time making the case that this is a bug. The main thing here is that usingnamespace has been slated for the chopping block. I would avoid it from now on. See Remove `usingnamespace` · Issue #20663 · ziglang/zig · GitHub for the compiler team conversation. You can find some of the conversation from ziggit here: POLL: Remove usingnamespace
Besides that, dependency loop detection improvements would not be a bug. Zig is moving fast and implementation details of the compiler should not be relied upon. It would be hard to explain that an improvement in dependency loop detection is a bug.
I am curious though: does the same error happen if you put mixin in it’s own file with it’s own? What about if you move MyNode into it’s own file as well? You might have found a perfect storm kind of issue.