#ownership

Jane Street OxCaml — Modes (Uniqueness, Locality, Linearity)

§1 Provenance Vendor : Jane Street Capital, in collaboration with Tarides on the upstream merge. Project : OxCaml — open-source branch of OCaml. Announced/rebranded July 2025. Repo: ocaml-flambda/ocaml-jst . Docs : https://oxcaml.org/documentation/modes/intro/ . Blog series "Oxidizing OCaml" : Locality: https://blog.janestreet.com/oxidizing-ocaml-locality/ Rust-Style Ownership: https://blog.janestreet.com/oxidizing-ocaml-ownership/ Data Race Freedom: https://blog.janestreet.com/oxidizing-ocaml-parallelism/ Data-race-freedom proposal in tree : https://github.com/ocaml-flambda/ocaml-jst/blob/main/jane/doc/proposals/data-race-freedom.md . 2025 community write-up : Tarides, "Introducing Jane Street's OxCaml Branch!", https://tarides.com/blog/2025-07-09-introducing-jane-street-s-oxcaml-branch/ . Production milestone : ICFP...

Hylo (formerly Val)

§1 Provenance Authors : Dimitri Racordon, Dave Abrahams, Sean Parent, et al. Originally proposed in WG21 paper P2676R0 (Oct 2022), https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2676r0.pdf . Project home : https://hylo-lang.org/ . Tour: https://docs.hylo-lang.org/language-tour/ . Specification: https://github.com/hylo-lang/specification/blob/main/spec.md . Renamed Jan 2024 : Val → Hylo, to disambiguate from other "Val" projects. Object-model doc for Swift designers : https://github.com/hylo-lang/Documentation/blob/main/object-model-for-swift-designers.md . Discussion on Rust comparison : https://github.com/orgs/hylo-lang/discussions/788 . §2 Core type discipline Hylo has only value types....

Swift consuming / borrowing / inout & Noncopyable Types

§1 Provenance Vendor : Apple. Swift Evolution. Foundational law : SE-0176 Enforce Exclusive Access to Memory (Swift 5, 2017–2018). Parameter modifiers : SE-0377 borrowing / consuming parameter ownership modifiers , https://github.com/swiftlang/swift-evolution/blob/main/proposals/0377-parameter-ownership-modifiers.md . Noncopyable foundation : SE-0390 Noncopyable structs and enums , https://github.com/swiftlang/swift-evolution/blob/main/proposals/0390-noncopyable-structs-and-enums.md . Generics : SE-0427 Noncopyable Generics , https://github.com/swiftlang/swift-evolution/blob/main/proposals/0427-noncopyable-generics.md . Pattern matching : SE-0432 Borrowing/consuming pattern matching for noncopyable types . Std lib primitives : SE-0437. 2026 review item...

Scala 3 Capture Checking

§1 Provenance Lead : Martin Odersky and the EPFL LAMP group. Capture-checking research and Capybara extension led by Oliver Bračevac. Reference docs (experimental) : https://docs.scala-lang.org/scala3/reference/experimental/cc.html . Advanced: https://docs.scala-lang.org/scala3/reference/experimental/cc-advanced.html . Nightly basics: https://nightly.scala-lang.org/docs/reference/experimental/capture-checking/basics.html . Scala Days 2025 talk : Oliver Bračevac (EPFL/LAMP), https://bracevac.org/assets/pdf/scaladays2025_annot.pdf and https://scaladays.org/editions/2025/talks/capture-checking-a-new-approach . Conference papers : "What's in the Box: Ergonomic and Expressive Capture Tracking over Generic Data Structures", OOPSLA 2025 (System Capless). https://2025.splashcon.org/details/OOPSLA/133/ ... "System Capybara: Capture...

Austral

§1 Provenance Author : Fernando Borretti. Reference site : https://austral-lang.org/ . Spec: https://austral-lang.org/spec . Features: https://austral-lang.org/features . Introduction post : https://borretti.me/article/introducing-austral . Implementation post : https://borretti.me/article/how-australs-linear-type-checker-works (the linear checker is <600 LOC of OCaml). Long essay on why this matters: https://borretti.me/article/type-systems-memory-safety . External comparison : https://verdagon.dev/blog/linear-types-borrowing by Evan Ovadia. HN thread : https://news.ycombinator.com/item?id=34168452 . Repo : https://github.com/austral/austral . §2 Core type discipline Austral has a single concept doing all the...

Vale Generational References

§1 Provenance Author : Evan Ovadia. Canonical write-up : "Vale's Memory Safety Strategy: Generational References and Regions", https://verdagon.dev/blog/generational-references (originally Aug 2021, updated July 9 2023). Earlier v1 at https://verdagon.dev/blog/generational-references-v1 . Project page : https://vale.dev/vision/safety-generational-references and the Linear-Aliasing Model, https://vale.dev/linear-aliasing-model . Memory Safety Grimoire (Apr 24 2024): a survey of 14 memory-safety techniques, https://verdagon.dev/grimoire/grimoire . 2024 follow-up : "Zero-Cost Memory Safety with Vale Regions, Part 1: Immutable Region Borrowing", https://verdagon.dev/blog/zero-cost-borrowing-regions-part-1-immutable-borrowing ....

Pony Reference Capabilities

§1 Provenance Authors : Sylvan Clebsch (founder), Sebastian Blessing, Sophia Drossopoulou; Imperial College London + Microsoft Research. Tutorial home : https://tutorial.ponylang.io/reference-capabilities/reference-capabilities.html . Foundational paper : Clebsch, Drossopoulou, Blessing, McNeil, "Deny Capabilities for Safe, Fast Actors", AGERE 2015. Subtyping : https://tutorial.ponylang.io/reference-capabilities/capability-subtyping.html . Recovery : https://tutorial.ponylang.io/reference-capabilities/recovering-capabilities.html . Practitioner intro : https://zartstrom.github.io/pony/2016/08/28/reference-capabilities-in-pony.html ; https://bluishcoder.co.nz/2017/07/31/reference_capabilities_consume_recover_in_pony.html . §2 Core type discipline Every reference in Pony has both a type T and a capability cap ....

Project Verona Regions

§1 Provenance Sponsor : Microsoft Research Cambridge, Microsoft Special Projects, Imperial College London. Core authors : Sylvan Clebsch (also Pony founder), Matthew J. Parkinson, Sophia Drossopoulou, Tobias Wrigstad, Juliana Franco. PM support from Mads Torgersen (C#). Project home : https://www.microsoft.com/en-us/research/project/project-verona/ . Publications : https://microsoft.github.io/verona/publications.html . Repo : https://github.com/microsoft/verona (MIT license). Key papers : Cheeseman, Parkinson, Clebsch, Kogias, Drossopoulou, Chisnall, Wrigstad, Liétar, "When Concurrency Matters: Behaviour-Oriented Concurrency", OOPSLA 2024. Arvidsson, Castegren,...

Linear Haskell

§1 Provenance Paper : Bernardy, Boespflug, Newton, Peyton Jones, Spiwack, "Linear Haskell: practical linearity in a higher-order polymorphic language", arXiv:1710.09756, POPL 2018. GHC documentation (user's guide): 9.0 intro: https://downloads.haskell.org/ghc/9.0.1/docs/html/users_guide/exts/linear_types.html 9.12 (Nov 2024): https://downloads.haskell.org/~ghc/9.12.0.20241128/docs/users_guide/exts/linear_types.html 9.15 dev (2026): https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/linear_types.html Status in user guide every release : "currently considered experimental, with bugs, warts, and bad error messages expected". §2 Core type discipline Linearity is a property of the arrow , not the value...

Rust Polonius (2026)

§1 Provenance Working group : Polonius WG, Rust compiler-team. Niko Matsakis (design), Jack Huey, Matthew Jasper, Amanda Stjerna (impl/PhD). Foundational papers : Matsakis et al., Non-Lexical Lifetimes RFC (RFC 2094, 2017), stabilised by default in Rust 1.63 (Aug 2022). Stjerna, Polonius Revisited (2023, Inside Rust blog). 2026 stabilisation goal : "Stabilize and model Polonius Alpha", https://rust-lang.github.io/rust-project-goals/2026/polonius.html WG page : https://rust-lang.github.io/compiler-team/working-groups/polonius/ Crate : https://github.com/rust-lang/polonius (Datafrog/Datalog reference impl, now superseded by in-tree...

Ownership, Borrowing, Reference Modes

Inko — Singly-Owned Values

§1 Provenance Author : Yorick Peterse. Project home : https://inko-lang.org/ . Repo: https://github.com/inko-lang/inko (MIT license). Memory management reference : https://docs.inko-lang.org/manual/latest/getting-started/memory-management/ . Versioned: https://docs.inko-lang.org/manual/v0.13.2/getting-started/memory-management/ . Comparison page : https://docs.inko-lang.org/manual/master/getting-started/compared/ . Funded by : NLnet, https://nlnet.nl/project/Inko/ . Release notes : 0.10.0 (2022) introduced the ownership model. 0.18.1 (2025) latest stable. https://inko-lang.org/news/inko-0-18-1-is-released/ . Theoretical foundation : cites Servetto et al., "Ownership You Can Count On: A Hybrid Approach to Safe Explicit Memory Management"....

Mojo (2026)

§1 Provenance Vendor : Modular Inc. Lead: Chris Lattner. Reference docs : https://docs.modular.com/mojo/manual/values/ownership/ . Deep dive: https://www.modular.com/blog/deep-dive-into-ownership-in-mojo . Lifetimes / provenance proposal : https://github.com/modular/modular/discussions/338 . Wikipedia summary : https://en.wikipedia.org/wiki/Mojo_(programming_language) . Production-ready milestone : Q1 2026. Open source commitment : "fall 2026" for the compiler; the standard library has been open since 2024. 2024–2025 contributor : Evan Ovadia (Vale) worked at Modular Jul 2024 – Dec 2025 on linear types, associated...