| name | reduce-similarities |
| description | Detect duplicate Rust code using AST-based similarity analysis. Use when working with .rs files and looking for code duplication or refactoring opportunities. |
| argument-hint | [path] [--threshold 0.85] [--print] |
| allowed-tools | Bash(similarity-rs *) Read Grep Glob |
| paths | **/*.rs |
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:
similarity-rs
direnv exec . 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
| Option | Description |
|---|
--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 |
--print | Show actual code snippets |
--experimental-types | Enable struct/enum similarity detection |
--filter-function <name> | Filter by function name |
--fail-on-duplicates | Exit 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
