Rust’s ownership model (which is more than just the borrow checker, it’s the whole concept of one location actually owning data, and aliasing XOR mutability, an

Rust’s ownership model (which is more than just the borrow checker, it’s the whole concept of one location actually owning data, and aliasing XOR mutability, and the pervading effects of this design on the language and its libraries) is a really big deal, even if it doesn’t look like it would be at a casual glance. It changes how you approach programming and reason about systems, and truly is (or should be used as) a fundamentally different approach to data flow and what’s possible, a smidgeon like Prolog in that way of being different, though not as much. I miss it very frequently when working in other languages (which is mostly JavaScript these days), because there are plenty of things that just become impossible to express reliably without it. Working in another language you can adopt conventions of writing in this style, but you can’t verify it without representing it in the type system, so the result will be riddled with holes in other languages. (It is, however, difficult to disentangle some features that Rust’s ownership model requires but which aren’t necessarily a part of that ownership model: for example, algebraic data types are essential and expression orientation extremely desirable, but there are other languages which have those features without the rest of the ownership model.) People often think memory safety without garbage collection is Rust’s shtick, but it’s actually the ownership model that’s Rust’s defining feature, underpinning everything and making that possible.