The data look fully immutable, which means no cycles, so I'd bet on some form of reference counting being used for garbage collection (though I haven't looked c

The data look fully immutable, which means no cycles, so I'd bet on some form of reference counting being used for garbage collection (though I haven't looked closely). As for memory safety, there are just five well-encapsulated uses of unsafe in the whole repository; you can inspect them and decide for yourself :)