[metaltyphoon]

Traits, generics, ownership, RAII shows up in many languages, so what other concept outside of lifetimes does Rust introduces?

[ridiculous_fish]

Affine types, variance, higher-rank trait bounds, phantom data, MaybeUninit, and the whole macro and proc-macro systems are some examples of concepts that I found to be challenging when learning Rust.

Dyn-safety is another but I had encountered that previously in Swift.