can add mut to self in trait impl

mut-for-immutable.rs

// The trait itself says the method takes self as immutable
trait ImmutableOp {
    fn do_immutable(self);
}

impl ImmutableOp for Vec<u8> {
    // FAILS TO COMPILE, AS IT SHOULD:
    // fn do_immutable(self) {
    //     self.push(0);
    // }

    // COMPILES FINE; SHOULD IT?:
    fn do_immutable(mut self) {
        self.push(0);
    }
}

fn main() {
    // immutable binding
    let v = Vec::new();
    
    // mutated
    v.do_immutable();
}