After reading a good chunk of the Programming Rust book (minus concurrency, async and macros) I can understand that. My C++ experience helped a lot in comprehending and mentally mapping Rust concepts.

As far as I can tell, that’s normal Rust code, but yes it’s unreadable if you come from C++ or another language and don’t know Rust syntax. The funny thing is that this kind of code is supposed to be the readable part of Rust :-)