[brundolf]

Interesting, I hadn't heard this before. Do you have any resources I could read?

Edit: I do know that languages where strings are immutable use that fact to do lots of optimization (automatically sharing "copied" strings and just cloning reference-counters, for example), but you can accomplish some of this in Rust too with Rc<> or even persistent data structures if you really want to. And of course there are cases where it's more efficient to actually mutate a string, which these languages can't do. But it sounds like you're talking about something else?

[estebank]

There are three strategies that other languages use automatically that you can also apply in Rust by hand: string interning, small string optimization and "Copy-on-write". For the first and second, you can use some existing crate like https://docs.rs/string-interner/0.12.2/string_interner/ and https://github.com/rust-analyzer/smol_str. For the later, you can use Cow<'_, str> https://doc.rust-lang.org/std/borrow/enum.Cow.html. I'm having trouble thinking of a case where Rc<String> would be appropriate.