This was a fun read, but it's a shame it hasn't gotten more attention. I wouldn't have guessed that Bun was using a custom fork of Zig. Since the feature has been closed, I strongly suspect that they'll eventually need to need to go back to upstream and revert their usage of private members. Using Python style `_members` seems like it should be good enough. If you're already manually managing memory it seems like respecting those privacy hints should be reasonable enough.
