You're already getting a lot of replies, and I don't want to pile on, but I think the clearest way to see the intent there is at the start of the following para

You're already getting a lot of replies, and I don't want to pile on, but I think the clearest way to see the intent there is at the start of the following paragraph: > Given that aliasing optimizations are something that the Rust compiler developers clearly want to support, we need some way of “ruling out” counterexamples like the one above from consideration.