ccusage Rust Code Similarity Detection
similarity-rs comes from the Nix dev shell (similarity in
nix/dev-shell.nix); prefix it with direnv exec . from outside the shell.
TypeScript duplication belongs to the typescript and ast-grep skills.
Run it over $ARGUMENTS, or over . when none was given. Functions and type
definitions are separate passes, so a default run silently misses parallel
structs and enums:
similarity-rs . --threshold 0.85 --min-lines 5
similarity-rs . --threshold 0.85 --experimental-types
--print shows the matching snippets and similarity-rs --help has the rest;
--skip-test is worth adding when fixture-shaped test functions drown out the
real findings.
Triage
A score is a starting point, not a verdict. Usually worth refactoring:
- 100% matches: extract a shared function or generic.
- 95-100% across different types: generic function with trait bounds.
- Duplicate impl methods on several types: trait with default implementations.
- 85-95% match arms or error handling: shared helper or macro.
- Parallel structs with identical fields: shared base or generic struct.
Usually left alone: short new() constructors, simple From/Into impls, and
anything a derive would generate.
Report each surviving candidate as a concrete before/after shape, not as a list of scores.