---

name: rust-knowledge-patch description: This skill should be used when writing Rust code, using async closures, let chains, Edition 2024 features, new collection methods like extract_if, integer arithmetic methods, or any Rust features from 2024-2026. license: MIT metadata: author: Nevaberry version: "1.93"

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