In practice this is a compiler bug, though, and is treated as such, and not a soundness hole in the abstract design of the type system.
There has also not been a single case of this bug being triggered in the wild by accident.
There has also not been a single case of this bug being triggered in the wild by accident.
There was a Git repository demontrating unsoundness issues in the compiler, but I seem to be unable to find it anymore :/. It seemed like there would be more than one underlying issue, but I can't really remember that.
But this time I've starred and cloned it!
I didn't quite see if this actually exploits multiple bugs or leverages just one, though.
Per https://blog.rust-lang.org/2023/01/20/types-announcement.htm... there is a roadmap for ensuring Rust type system soundness end of year 2027. I think it means the implementation.