Adding generational references needs to be built into the language at a very deep level to work properly, AFAICT.

One can almost do it by using "side tables" but it would come at a rather high performance cost for Rust. Since generations are located inside / next to the object in Vale, we can take advantage of the cache to avoid any significant slowdowns.

Additionally, one of the main benefits of this approach is simplicity for the user, and I'm not sure Rust can be made simpler by adding more mechanisms.