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check-similarity-rs

Testing & Quality
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Detect duplicate Rust code using AST-based similarity analysis. Use when working with .rs files and looking for code duplication or refactoring opportunities.

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How to use this skill

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Source SKILL.md: https://github.com/mizchi/similarity/blob/HEAD/.claude/skills/check-similarity-rs/SKILL.md

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Rust Code Similarity Detection

What to do

Run similarity-rs on the target Rust project to detect duplicate functions, struct/enum definitions, and impl methods, then analyze results and propose refactoring.

If similarity-rs is not installed:

cargo install similarity-rs

Step 1: Run similarity analysis

similarity-rs $ARGUMENTS

If no arguments given:

similarity-rs . --threshold 0.85 --min-lines 5

For struct/enum similarity:

similarity-rs . --threshold 0.85 --experimental-types

Step 2: Analyze results

High-priority

  • 100% similarity: Exact duplicates -> extract shared function or use generics
  • 95-100%: Same algorithm on different types -> generic function with trait bounds
  • Duplicate impl methods: Same logic across types -> trait with default implementation

Medium-priority

  • 85-95%: Similar match arms or error handling -> macro or shared helper
  • Parallel struct definitions: Identical fields -> shared base or generic struct

Acceptable

  • Short new() constructors with field initialization
  • Simple From/Into implementations
  • Derive-equivalent implementations

Step 3: Propose refactoring

For each high-priority pair, show before/after code with Rust idioms.

Key Options

OptionDescription
--threshold <0-1>Similarity threshold (default: 0.85)
--min-lines <n>Skip functions shorter than n lines (default: 3)
--min-tokens <n>Skip functions with fewer AST nodes
--printShow actual code snippets
--experimental-typesEnable struct/enum similarity detection
--filter-function <name>Filter by function name
--fail-on-duplicatesExit code 1 if duplicates found

Common Rust refactoring patterns

  • Type-specific functions -> generic fn<T: Trait> with trait bounds
  • Duplicate impl blocks across types -> trait with default methods
  • Repeated match patterns -> macro_rules! or helper function
  • Parallel X/Y/Z functions -> enum parameter or tuple-based abstraction
  • Similar error handling -> shared Result combinator or ? chain