Code shared from the Rust Playground

playground.rs

struct A {
    a : i32,
}

impl A {
    fn bind_lifetime_mut(&mut self) -> &i32 {
        return &self.a;
    }

    fn legal(&mut self) -> &i32 {
        self.bind_lifetime_mut();
        return self.bind_lifetime_mut();
    }

    fn not_legal(&mut self) -> &i32 {
        let test_ret = self.bind_lifetime_mut();
        if *test_ret == 1 {
            return test_ret;
        }
        return self.bind_lifetime_mut()
    }
}