Improving our example 4-pinning to the rescue 241 impl Foo { fn a(self: Pin<&mut Self>)-> Pin<&mut Maybe Self Ref> { unsafe { self. map_unchecked_mut(|s| &mut s. a) } } fn b(self: Pin<&mut Self>)-> &mut String { unsafe { &mut self. get_unchecked_mut(). b } } } Note that these methods will only be callable when Foo is pinned. Y ou won't be able to call either of these methods on a regular instance of Foo. Pin projections do have a few subtleties that you should be aware of, but they're explained in quite some detail in the official documentation ( https://doc. rust-lang. org/stable/std/ pin/index. html ), so I'll refer you there for more information about the precautions you must take when writing projections. Note Since pin projections can be a bit error-prone to create yourself, there is a popular create for making pin projections called pin_project (https://docs. rs/pin-project/latest/ pin_project/ ). If you ever end up having to make pin projections, it's worth checking out. With that, we've pretty much covered all the advanced topics in async Rust. However, before we go on to our last chapter, let's see how pinning will prevent us from making the big mistake we made in the last iteration of our coroutine example. Improving our example 4-pinning to the rescue Fortunately, the changes we need to make are small, but before we continue and make the changes, let's create a new folder and copy everything we had in our previous example over to that folder: Copy the entire c-coroutines-problem folder and name the new copy e-coroutines-pin Open Cargo. toml and rename the name of the package e-coroutines-pin