Chapter 5. Changes in Rust 1.84.1 Toolset

RHEL provides Rust Toolset in version 1.84.1. Notable enhancements since the previously available version 1.79.0 include:

The new LazyCell and LazyLock types delay the initialization until the first use. These extend the earlier OnceCell and OnceLock types with the initialization function included in each instance.
The new sort implementations in the standard library improve the runtime performance and compile times. They also try to detect cases where a comparator is not producing a total order, making that panic instead of returning unsorted data.
Precise capturing for opaque return types have been added. The new use<..> syntax specifies the generic parameters and lifetimes used in an impl Trait return type.
Many new features for const code have been added, for example:
- Floating point support
- const immediates for inline assembly
- References to statics
- Mutable reference and pointers
Many new features for unsafe code have been added, for example:
- Strict provenance APIs
- &raw pointer syntax
- Safely addressing statics
- Declaring safe items in unsafe extern blocks
The Cargo dependency resolver is now version aware. If a dependency crate specifies its minimum supported Rust version, Cargo uses this information when it resolves the dependency graph instead of using the latest semver-compatible crate version.

Compatibility notes:

The WebAssembly System Interface (WASI) target is changed from rust-std-static-wasm32-wasi to rust-std-static-wasm32-wasip1. You can select the WASI target also by using the --target wasm32-wasip1 parameter on the command line. For more information, see the Changes to Rust’s WASI targets upstream blog post.
The split panic hook and panic handler arguments core::panic::PanicInfo and std::panic::PanicInfo are now different types.
extern "C" functions abort the process on uncaught panics. Use extern "C-unwind" instead to allow unwinding across ABI boundaries.

Rust Toolset is a rolling Application Stream, and Red Hat only supports the latest version. For more information, see the Red Hat Enterprise Linux Application Streams Life Cycle document.