Yea it’s like when we writeSome(2). It’s not a function call but a variant of the Option enum.

Do you mean RAII guards

https://rust-unofficial.github.io/patterns/patterns/behavioural/RAII.html

Or match guards?

https://doc.rust-lang.org/rust-by-example/flow_control/match/guard.html

Yeah I don’t mean just terse functional idioms. Any programming technique that blew your mind the first time you came across it would qualify.