| name | refactoring |
| description | Rust Refactoring Guide guidance for Fortress Rollback. Use when Refactoring code, planning safe transformations, verification after changes. |
Rust Refactoring Guide
Three Rules of Safe Refactoring
- Preserve Semantics -- behavior identical unless explicitly changing it
- Incremental Steps -- one change at a time, verify, proceed
- Test Coverage First -- ensure tests exist before refactoring
When to Refactor
| Signal | Action |
|---|
unwrap()/expect() in production | Convert to Result propagation |
.clone() without clear need | Analyze ownership, use references |
| Manual loops with indexing | Convert to iterators |
| Primitive types for domain concepts | Wrap in newtypes |
Vec<T> where &[T] suffices | Accept slices at boundaries |
| Large enum variants | Box the large variants |
Verification Checklist
cargo nextest run && cargo clippy --workspace --all-targets --features tokio,json
cargo check && cargo nextest run
cargo fmt && cargo clippy --workspace --all-targets --features tokio,json && cargo nextest run
rg "unwrap\(\)|expect\(|panic!\(|todo!\(" src/
Refactoring Patterns Summary
| # | Pattern | From | To | Clippy Lint |
|---|
| 1 | Clone to Reference | fn(x: String) | fn(x: &str) | needless_pass_by_value |
| 2 | Unnecessary to_string() | name.to_string() for lookup | Direct &str | unnecessary_to_owned |
| 3 | Pre-allocate Collections | Vec::new() + push loop | Vec::with_capacity(n) | -- |
| 4 | Reuse Collections in Loops | New buffer each iteration | .clear() + reuse | -- |
| 5 | clone_from | x = y.clone() | x.clone_from(&y) | -- |
| 6 | Index Loop to Iterator | for i in 0..len | .iter() chain | -- |
| 7 | Avoid Intermediate collect() | -> Vec<T> | -> impl Iterator | -- |
| 8 | chunks_exact | .chunks(n) | .chunks_exact(n) | -- |
| 9 | iter().copied() | .iter().map(|&b| b) | .iter().copied() | -- |
| 10 | swap_remove | .remove(i) unordered | .swap_remove(i) | -- |
| 11 | unwrap() to ? | .unwrap() | .ok_or(err)? | unwrap_used |
| 12 | expect() to Error | .expect(msg) | .map_err(|e| Err)? | expect_used |
| 13 | Index to get() | collection[i] | .get(i)? | indexing_slicing |
| 14 | Silent Swallow to Explicit | let _ = result | Propagate or handle | -- |
| 15 | unwrap_or to unwrap_or_else | unwrap_or(expensive()) | unwrap_or_else(|| ...) | or_fun_call |
| 16 | &String/&Vec to slice | fn(v: &Vec<T>) | fn(v: &[T]) | ptr_arg |
| 17 | Return Borrowed to Owned | Complex lifetime returns | Cow<'_, str> | -- |
| 18 | mem::take | Clone + clear | mem::take(&mut x) | -- |
| 19 | Struct Decomposition | &mut self conflicts | Direct field access / parts_mut() | -- |
| 20 | Cow for Conditional Ownership | Always clone | Cow::Borrowed/Cow::Owned | -- |
| 21 | Primitive to Newtype | fn(from: u64, to: u64) | Type-safe wrappers | -- |
| 22 | Bool to Enum | fn(secure: bool) | Security::Secure | -- |
| 23 | Option Fields to Types | email: Option<String> | VerifiedUser { email: String } | -- |
| 24 | String Status to Enum | status: String | TaskStatus::Complete | -- |
| 25 | Checked Arithmetic | center - radius | center.checked_sub(radius)? | arithmetic_side_effects |
Common Pitfalls
- Over-optimizing cold paths -- profile first, optimize hot paths
- Breaking trait bounds -- don't add new bounds to existing generics
- Changing public return types --
Vec<T> to impl Iterator is breaking
- Clone removal causing borrow conflicts -- analyze why clone existed
mem::take with invalid Default -- use mem::replace with valid replacement- Iterator refactoring changes order -- sequential iterators if order matters
- Changing error variant structure -- use
#[non_exhaustive] on error enums
Automated Transformation Checklist
Pre-Refactoring
Post-Refactoring
