Abstract:

In this marathon live-streamed podcast episode for Rustacean Station, hosts Jon Gjengset and Ben Striegel conduct a comprehensive review of seven Rust releases, from version 1.72 to 1.78. The discussion covers a wide array of significant language and tooling advancements.

Major highlights include the long-awaited stabilization of async fn and return-position impl Trait in traits (AFIT/RPITIT) in version 1.75, a milestone for asynchronous programming in Rust. The hosts also detail numerous improvements to the Cargo build tool, such as inline lint configuration, secure registry authentication, and more helpful update notifications. Other key topics include enhancements to compiler diagnostics with the new #[diagnostic] attribute, the introduction of C-string literals, the offset_of! macro for safer low-level programming, and many new stabilized APIs. Throughout the stream, the hosts engage in a practical demonstration of open-source contribution by submitting and tracking a live pull request to the Rust compiler's documentation.

A Marathon of Rust Updates: What's New from 1.72 to 1.78

• 0:19:22 Rust 1.72: The first release covered includes improved compiler error messages that suggest enabling a specific feature flag if an item is disabled. It also removes the limit on const evaluation time, allowing for more complex compile-time computations.
• 41:55 The Live PR Saga: During the 1.72 review, the hosts open a live pull request to the official Rust repository to improve the documentation for the String::leak method. They continue to check on its progress and address feedback throughout the stream.
• 1:17:46 Rust 1.73: This version introduces cleaner, multi-line panic messages for improved readability. It also stabilizes a more ergonomic API for thread_local! statics that use Cell or RefCell, removing the need for a closure in common cases.
• 1:57:17 Rust 1.74: Key updates include the ability to configure lints directly in Cargo.toml and the stabilization of Cargo registry authentication for secure interaction with private repositories. Rustdoc search is also enhanced to understand generic type parameters in function signatures.
• 2:52:07 Rust 1.75 - A Major Milestone: This release marks the stabilization of async fn in traits and return-position impl Trait in traits (AFIT/RPITIT), a landmark feature enabling more ergonomic and powerful asynchronous abstractions. Other additions include pointer byte-offset APIs for low-level memory manipulation.
• 3:53:49 Rust 1.76: A smaller release that focuses on quality-of-life improvements. It adds type_name_of_val, which returns the name of a type from a value instance, and Arc::unwrap_or_clone for more efficient data retrieval from reference-counted pointers.
• 4:18:26 Rust 1.77: C-string literals (e.g., c"hello") are stabilized, allowing for the compile-time creation of null-terminated strings without runtime allocation. This release also adds support for recursion in async fn (when using indirection like Box::pin) and stabilizes the offset_of! macro for safely calculating field offsets in structs.
• 5:19:14 Rust 1.78: The new #[diagnostic] attribute is stabilized, allowing library authors to provide custom, more helpful compiler errors for their traits. This release also enables debug assertions in the pre-compiled standard library to be active when user code is built in debug mode, catching more potential bugs.