Rust 1.85-1.93 Knowledge Patch

Claude's baseline knowledge covers Rust through 1.84. This skill provides features from 1.85 (Feb 2025) through 1.93 (Jan 2026).

Quick Reference

Edition 2024 (Major Changes)

Change Migration

unsafe extern "C" {}

Add unsafe to extern blocks

#[unsafe(no_mangle)]

Wrap unsafe attrs in unsafe()

unsafe {} in unsafe fns Explicit unsafe blocks required

static mut denied Use atomics/sync primitives

gen reserved Rename identifiers

set_var /remove_var unsafe Wrap in unsafe {}

Let chains (Edition 2024 only):

if let Some(x) = opt && x > 0 && let Some(y) = other { ... }

See references/edition-2024.md for full migration guide.

Async

• Async closures: async || {} with AsyncFn , AsyncFnMut , AsyncFnOnce traits

• OnceLock::wait : Block until initialization completes

• RwLockWriteGuard::downgrade : Write → read lock without releasing

See references/async-and-concurrency.md .

Collections

Method Types

extract_if

Vec, LinkedList, HashMap, HashSet, BTreeMap, BTreeSet

pop_if

Vec

pop_front_if / pop_back_if

VecDeque

get_disjoint_mut

slices, HashMap

Cell::update

Cell

Tuple collection: (Vec<>, Vec<>) = iter.map(|x| (a, b)).collect()

See references/collections.md .

Integers

Method Description

midpoint

Exact midpoint without overflow

is_multiple_of

Divisibility check

unbounded_shl/shr

Return 0 on overflow

cast_signed/unsigned

Bit reinterpretation

*_sub_signed

Subtract signed from unsigned

strict_*

Panic on overflow (release too)

carrying_/borrowing_

Extended precision arithmetic

unchecked_*

UB on overflow (perf-critical)

See references/integers-and-arithmetic.md .

Slices & Arrays

• Chunking: as_chunks , as_rchunks → (&[[T; N]], &[T])

• Conversion: slice.as_array::<N>() → Option<&[T; N]>

• Boundaries: str.ceil_char_boundary(n) , floor_char_boundary(n)

• Const: reverse , rotate_left , rotate_right

See references/slices-and-arrays.md .

Strings & Paths

• Path::file_prefix : Filename without ANY extensions

• PathBuf::add_extension : Add without replacing

• OsStr::display : Lossy UTF-8 display

• String::into_raw_parts : Decompose to (ptr, len, cap)

See references/strings-and-paths.md .

Pointers & Memory

• Trait upcasting: &dyn Derived → &dyn Base automatic

• NonNull provenance: from_ref , without_provenance , expose_provenance

• MaybeUninit slices: write_copy_of_slice , assume_init_ref

• Zeroed constructors: Box::new_zeroed() , Arc::new_zeroed()

See references/pointers-and-memory.md .

Assembly & SIMD

• Safe #[target_feature] : No unsafe needed for decorated fns

• asm! labels: Jump to Rust code blocks

• asm! cfg: #[cfg(...)] on individual lines

• Naked functions: #[unsafe(naked)]

• naked_asm!

See references/assembly-and-simd.md .

I/O

• io::pipe() : Cross-platform anonymous pipes

• File::lock/unlock : Advisory file locking

• i128/u128 in FFI: No more warnings

See references/io-and-process.md .

Misc

• Result::flatten : Result<Result<T,E>,E> → Result<T,E>

• fmt::from_fn : Display from closure

• Duration::from_mins/hours : Convenience constructors

• Const TypeId::of : Compile-time type IDs

• Const float rounding: floor , ceil , round in const

See references/misc-apis.md .

Cargo

• LLD default (x86_64 Linux): Faster linking

• cargo publish --workspace : Multi-crate publishing

• Auto cache cleaning: 3mo network, 1mo local

See references/cargo-and-tooling.md .

Reference Files

Detailed documentation in references/ :

File Contents

edition-2024.md

Full Edition 2024 migration guide

async-and-concurrency.md

Async closures, locks, atomics

integers-and-arithmetic.md

All integer methods

collections.md

extract_if, pop_if, disjoint_mut

slices-and-arrays.md

Chunking, conversion, const ops

strings-and-paths.md

Path/String APIs

pointers-and-memory.md

Upcasting, provenance, MaybeUninit

assembly-and-simd.md

asm!, target_feature, naked fns

io-and-process.md

Pipes, FFI, file locking

misc-apis.md

Floats, Duration, formatting, cfg

cargo-and-tooling.md

LLD, workspace publish, cache