Rust: Drop Improvements and Compiler Fixes

Transcript

Good morning. This is your Rust development briefing for May 16th, 2026.

The team merged 15 pull requests overnight, headlined by significant language feature improvements. P8L1 merged implementation of pinned drop sugar, introducing `fn drop(&pin mut self)` as syntactic sugar for `Drop::pin_drop`. This change spans 11 files with over 600 additions, making pinned drop operations more ergonomic.

TomtheCoder2 merged an unconstrained parameter fix addressing issue 107295, with changes across 42 files in the compiler's HIR analysis system. This was part of a larger rollup by JonathanBrouwer consolidating 12 separate pull requests.

aerooneqq merged delegation improvements that emit proper errors when self types aren't specified but are accessed, fixing crashes in delegation syntax. bjorn3 merged changes requiring External Item Implementations to be defined when compiling Rust dynamic libraries, preventing linker complaints about undefined symbols.

cjgillot merged destination propagation optimizations, computing liveness as ranges instead of traveling bitsets for better performance. GuillaumeGomez fixed rustdoc macro expansion to correctly handle associated items.

Additional merges included Wasm configuration updates by daxpedda disabling `main_needs_argc_argv` for most Wasm targets, UTF-8 pattern enforcement by qaijuang, and LLVM argument precedence fixes by guybedford allowing user arguments to override target specifications.

What's next: The delegation feature continues maturing with better error handling, and the pinned drop sugar will need documentation updates. Performance improvements in MIR transformations show ongoing optimization work.

That's your Rust briefing. Back tomorrow with more updates.