There's more than just memory safety for high assurance apps. Personally, I think Rust is heading in the right direction, but I am not sure it's complexity will ever be smooth or enjoyable for some. I feel you get most, if not all, that Rust is trying to achieve with Ada/SPARK right now for high-integrity, mission-critical apps along with a proven legacy: jet fighter software, railway controls, avionics, embedded, space, etc...

Take a look at the Adacore site, especially the free books (PDF):

https://www.adacore.com/books

Ada for the Embedded C Developer

Embedded Spark & Ada Use Cases