C++ lets you do this kind of stuff as well.

Primitive types and composite types having the same capabilities is a bit of a value statement for C++ and Rust IMO, and it's missing in a lot of languages downstream (IMO) of the "every variable is a reference to a slot/pointer" philosophy taken by most every managed language

C++ doesn't have methods/ "member functions" on the primitive types.

One reason is that C++ doesn't know where to put them, for user defined class, struct or union types these "member functions" as their name suggests live inside the class/ struct/ union definition but for a primitive where would these live?

In Rust they're just impl blocks, for example the method we're discussing here is:

    impl bool {    
        pub const fn toggle(&mut self) {
            *self = !*self;
        }
    }