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Abusing reborrowing for fun, profit, and a safepoint garbage collector

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Rust's references adhere to a strict "one exclusive XOR many shared" model, which gives the language much of its greatest safety guarantees. Reborrowing is a feature that seems on surface to break this rule: An exclusive reference can be turned into shared references and those shared references can be used together with the exclusive reference as long as these are all used as if they were shared references. Only once the exclusive reference is used as exclusive, all the derived or "reborrowed" s

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Other talks by Aapo Alasuutari

Can I borrow that? (Reborrow traits)

RustNL
RustWeek 19:54 1017 views

Can I borrow that? (Reborrow traits) by Aapo Alasuutari. Exclusive references make Rust, yet they cannot be built within Rust: the core act of reborrowing, that is giving temporary exclusive access and reclaiming exclusivity afterwards, is a feature implemented outside of the language. For custom user types or even reference wrappers like `Option &mut T` the best one can do is use explicit methods like `as_deref_mut` or `rb_mut`. The `Reborrow` traits project goal aims to fix this gap and make exclusive references buildable within the language. Come hear the how and why, why-nots, and what is to come! About Aapo Alasuutari (he/him): Aapo Alasuutari is a TypeScript developer by day, but by night transforms into a data-oriented design zealot building a JavaScript engine in Rust. At other times he sings in two choirs and collects side-projects like an enthusiastic blind magpie. - git: https://github.com/aapoalas - bluesky: https://bsky.app/profile/aapoalas.trynova.dev - linkedin: https://www.linkedin.com/in/aapo-alasuutari-b4968b63/ - website: https://trynova.dev/ This talk was given at RustWeek 2026 as part of the Rust Project track on Wednesday 20 May. You can find a playlist of all talks in this track at https://www.youtube.com/playlist?list=PL8Q1w7Ff68DBkk0ddSEqdf97swuDvMSKS, and a playlist of all RustWeek 2026 talks at https://www.youtube.com/playlist?list=PL8Q1w7Ff68DBpmF38rcIAf8Z9Gj2TnlgM For information about RustWeek 2027, go to https://2027.rustweek.org. We hope to see you there!