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name: rust description: Rust performance optimization guidelines. This skill should be used when writing, reviewing, or refactoring Rust code to ensure optimal performance patterns. Triggers on tasks involving memory allocation, ownership, borrowing, iterators, async code, or performance optimization.

Community Rust Best Practices

Comprehensive performance optimization guide for Rust applications. Contains 42 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

When to Apply

Reference these guidelines when:

• Writing new Rust code
• Optimizing memory allocation and ownership patterns
• Working with iterators and collections
• Writing async code with Tokio or other runtimes
• Reviewing code for performance issues

Rule Categories by Priority

Quick Reference

1. Memory Allocation (CRITICAL)

• mem-avoid-unnecessary-clone - Avoid unnecessary clone calls
• mem-preallocate-vec-capacity - Preallocate Vec capacity
• mem-use-cow-for-conditional-ownership - Use Cow for conditional ownership
• mem-use-arc-for-shared-immutable-data - Use Arc for shared immutable data
• mem-avoid-format-for-simple-concatenation - Avoid format! for simple concatenation
• mem-use-smallvec-for-small-collections - Use SmallVec for small collections

2. Ownership & Borrowing (CRITICAL)

• own-accept-str-slice-not-string - Accept &str instead of &String
• own-accept-slice-not-vec - Accept &[T] instead of &Vec
• own-use-into-for-flexible-ownership - Use Into for flexible ownership
• own-return-borrowed-when-possible - Return borrowed data when possible
• own-use-asref-for-generic-borrows - Use AsRef for generic borrows

3. Data Structure Selection (HIGH)

• ds-use-hashset-for-membership - Use HashSet for membership tests
• ds-use-hashmap-for-key-lookup - Use HashMap for key-value lookups
• ds-use-btreemap-for-sorted-iteration - Use BTreeMap for sorted iteration
• ds-use-vecdeque-for-queue-operations - Use VecDeque for queue operations
• ds-use-entry-api-for-conditional-insert - Use Entry API for conditional insert

4. Iterator & Collection Patterns (HIGH)

• iter-chain-instead-of-intermediate-collect - Chain iterators instead of intermediate collect
• iter-use-iter-over-into-iter-when-borrowing - Use iter() over into_iter() when borrowing
• iter-use-filter-map-for-combined-operations - Use filter_map for combined operations
• iter-use-flat-map-for-nested-iteration - Use flat_map for nested iteration
• iter-use-extend-for-bulk-append - Use extend() for bulk append
• iter-use-fold-for-accumulation - Use fold() for complex accumulation

5. Async & Concurrency (MEDIUM-HIGH)

• async-avoid-blocking-in-async-context - Avoid blocking in async context
• async-use-join-for-concurrent-futures - Use join! for concurrent futures
• async-use-rwlock-over-mutex-for-read-heavy - Use RwLock over Mutex for read-heavy
• async-minimize-lock-scope - Minimize lock scope
• async-use-buffered-for-bounded-concurrency - Use buffered() for bounded concurrency
• async-avoid-holding-lock-across-await - Avoid holding lock across await

6. Algorithm Complexity (MEDIUM)

• algo-avoid-nested-loops-for-lookup - Avoid nested loops for lookups
• algo-use-binary-search-for-sorted-data - Use binary search for sorted data
• algo-use-sort-unstable-when-order-irrelevant - Use sort_unstable when order irrelevant
• algo-use-select-nth-unstable-for-partial-sort - Use select_nth_unstable for partial sort
• algo-use-chunks-for-batch-processing - Use chunks() for batch processing

7. Compile-Time Optimization (MEDIUM)

• comp-use-const-for-compile-time-computation - Use const for compile-time computation
• comp-prefer-static-dispatch - Prefer static dispatch over dynamic
• comp-reduce-monomorphization-bloat - Reduce monomorphization bloat
• comp-use-const-generics-for-array-sizes - Use const generics for array sizes
• comp-avoid-repeated-parsing-of-static-data - Avoid repeated parsing of static data

8. Micro-optimizations (LOW)

• micro-use-inline-for-small-functions - Apply inline attribute to small hot functions
• micro-avoid-bounds-checks-in-hot-loops - Avoid bounds checks in hot loops
• micro-use-wrapping-arithmetic-when-safe - Use wrapping arithmetic when safe
• micro-use-byte-literals-for-ascii - Use byte literals for ASCII

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Full Compiled Document

For a comprehensive guide with all rules in a single document, see AGENTS.md.

Reference Files