Not quite; the method uses `&mut self`, so it actually operates on a mutable reference to the value that happens to be a primitive. If you declare a boolean without specifying the binding as mutable, you'd get a compiler error from trying to call this method. Moreover, if anything else had a reference to it at the same time, it would also cause a compiler error to call this method.

This is definitely something that Rust does a bit different than most other languages, but it's not anything specific to this method, booleans, or particularly new to the language. Most people will learn about the common different ways of defining a method (via ownership, shared reference, or mutable reference) fairly early on in programming Rust.