smol_str

It’s nice that rustc’s niche optimization lets smolstr be implemented with a simple enum, rather than having to do some unsafe union bit packing[0]. The only concession that had to be made to the compiler is using an enum for the InlineSize value to show that the last 3 bits of that aren’t used. [0]: https://github.com/rust-analyzer/smol_str/blob/fde86a5c0cb8f...

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.