Rust 1.85 Released: The Rust 2024 Edition and Async Closures

What happened

Rust 1.85.0 was released on February 20, 2025, according to the official Rust blog, and with it the Rust team stabilised the Rust 2024 edition. Editions are Rust's mechanism for opt-in changes that might otherwise pose a backwards-compatibility risk, applied per crate so the ecosystem can migrate at its own pace.

The Rust 2024 edition

The Rust team described Rust 2024 as the largest edition it has released. It bundles a broad set of opt-in changes across the language, standard library, Cargo, Rustdoc and Rustfmt, including new rules for how impl Trait captures lifetimes, changes to temporary scopes in if let and tail expressions, requiring the unsafe keyword on extern blocks, warning on unsafe operations in unsafe functions by default, and reserving the gen keyword for future generator blocks. Existing projects can migrate with the help of cargo fix, and many need no code changes at all.

Async closures

Rust 1.85 also stabilised async closures, written as async || {}, which return futures when called and can capture values from their environment, just as regular closures differ from functions. This came with three new traits in the standard library prelude, AsyncFn, AsyncFnMut and AsyncFnOnce, which solve cases that were previously awkward or impossible to express, such as a future borrowing from the closure's captures or writing higher-ranked async function signatures.

Why it mattered

The 2024 edition consolidated years of language evolution into a coherent opt-in upgrade, tightening safety defaults and reserving syntax for future features. Async closures, meanwhile, filled a long-standing gap in Rust's async story, making common asynchronous patterns first-class. Together they marked one of the most significant Rust releases since the 2021 edition.

Related on Skillo

See also: Rust 1.65 and generic associated types.

Sources

• Announcing Rust 1.85.0 and Rust 2024 (official Rust blog)

Published date reflects the original event date (2025-02-20). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.