Rustacean Station What's New in Rust 1.85 through 1.87
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Jan 22, 2026 A fast tour of Rust 1.85–1.87 highlights. They cover async closures, trait object upcasting, and hiding trait implementations from diagnostics. Tuple FromIterator, undeprecating std::env::home_dir, and small stabilized APIs get attention. New capabilities include disjoint mutable indexing, anonymous pipes, asm! jumps to Rust code, safe architecture intrinsics, and several stdlib convenience methods.
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Waker::noop For Simple Future Contexts
- Waker::noop provides a non-allocating no-op waker for contexts where a future won't be woken, simplifying manual Future implementations.
- Jon Gjengset highlights it avoids unsafe vtable work or Arc-based wakers for simple cases like single-run futures.
c_char Simplified To i8 Except Windows And Apple
- Rust simplified the definition of c_char: defaults to i8 except on Windows and Apple, matching clang and reducing per-target tables.
- Jon Gjengset explains this avoids brittle platform-specific tables and follows Clang's convention for new targets.
Safe Trait Upcasting Between Subtraits And Supertraits
- Trait upcasting allows converting a trait object of a subtrait into a trait object of its supertrait safely and without unsafe code.
- Jon Gjengset notes vtable layout guarantees let the compiler construct the supertrait vtable from the subtrait object for valid upcasts.