This is a really cool paper with impressive results.

An interesting property that this paper doesn't consider (I believe the language described does not allow it though) is casting pointers/references to integers. Many languages consider this unsafe, but Rust does not. Considering casting pointers to integers unsafe prevents 'address disclosure' vulnerabilities, which is relevant in the context of any program that incorporates (potentially buggy) unsafe code (read: all of them). This can be used to defeat ASLR.