this is commonly used with a similar meaning to self in cases where self can't be used because it is a reserved keyword.

Example:

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<St1::Item>> {
        let this = self.project();
        this.inner.poll_next(cx)
    }

https://github.com/rust-lang/futures-rs/blob/master/futures-util/src/stream/select.rs#L113-L116