Rust is about safe-to-use abstractions, not necessarily safe-to-implement abstractions. While we like for abstractions to be implemented safely, it is totally o

Rust is about safe-to-use abstractions, not necessarily safe-to-implement abstractions. While we like for abstractions to be implemented safely, it is totally okay to write an abstraction using unsafe code provided you can give it a safe API. So these abstractions may be implemented unsafely, but once implemented you don't need unsafe to use them. The only abstractions that C++ has that Rust doesn't are those involving intrusive datastructures (and you can make them work in some cases).