Rust: Weekly Recap - Performance Optimizations & Language Evolution
The Rust compiler saw significant performance improvements this week with intrinsic optimizations removing unnecessary memory allocations, while the language gained a new unstable Share trait for ergonomic reference counting.
Duration: PT2M27S
Transcript
This is your Rust weekly recap for May 17th through 24th, 2026.
20 pull requests merged with no additional commits this week.
**Performance & Compiler Improvements**
The biggest performance win comes from PR #156116, which eliminates unnecessary memory allocations for most compiler intrinsics. Previously, even returning a constant from `size_of_val` required stack allocation. This change allows intrinsics to return values directly, with all but 5 intrinsics in LLVM moving to this more efficient approach.
The `derive(PartialOrd)` macro received optimization when used alongside `derive(Ord)`, implementing a fast path that reduces generated code complexity in PR #155598.
An unsound feature was removed in PR #156242 - `target_feature_inline_always` relied on unstable LLVM pass ordering and has been eliminated to improve code soundness.
**Language Features**
A new unstable `Share` trait was introduced in PR #156828 as part of the 2026 ergonomic reference counting initiative. The trait provides a semantic alias for cloning reference-counted types, with initial implementations for references, `Arc`, `Rc`, and MPSC channel senders.
Target feature handling became more strict with PR #152821, allowing completely forbidden features to generate hard errors rather than warnings when they should be target modifiers instead.
**Bug Fixes**
Several MIR-related issues were resolved, including a reborrow ICE in place lowering and field validation fixes for the `Reborrow` trait implementation.
Float literal type suggestions were improved to avoid suggesting invalid syntax when literals end with dots.
**Documentation & Tooling**
Rustdoc gained better "jump to definition" support for primitive type methods and now consistently shows dyn compatibility sections for all traits, making it clearer when traits are object-safe.
Debug tooling improved with better handling of invalid `String` and `Vec` types in LLDB, plus Windows LLVM DLL distribution fixes.
Next week, we'll likely see continued refinement of the Share trait and potential stabilization discussions for recent performance improvements.
That's your Rust recap - focused development with meaningful performance gains and careful language evolution.