Rust

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name: Rust slug: rust version: 1.0.1 description: Write idiomatic Rust avoiding ownership pitfalls, lifetime confusion, and common borrow checker battles. metadata: {"clawdbot":{"emoji":"🦀","requires":{"bins":["rustc","cargo"]},"os":["linux","darwin","win32"]}}

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Quick Reference

| Topic | File | Key Trap | |-------|------|----------| | Ownership & Borrowing | ownership-borrowing.md | Move semantics catch everyone | | Strings & Types | types-strings.md | String vs &str, UTF-8 indexing | | Errors & Iteration | errors-iteration.md | unwrap() in production, lazy iterators | | Concurrency & Memory | concurrency-memory.md | Rc not Send, RefCell panics | | Advanced Traps | advanced-traps.md | unsafe, macros, FFI, performance |

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Critical Traps (High-Frequency Failures)

Ownership — #1 Source of Compiler Errors

Variable moved after use — clone explicitly or borrow with &

for item in vec moves vec — use &vec or .iter() to borrow

String moved into function — pass &str for read-only access

Borrowing — The Borrow Checker Always Wins

Can't have &mut and & simultaneously — restructure or interior mutability

Returning reference to local fails — return owned value instead

Mutable borrow through &mut self blocks all access — split struct or RefCell

Lifetimes — When Compiler Can't Infer

'static means CAN live forever, not DOES — String is 'static capable

Struct with reference needs <'a> — struct Foo<'a> { bar: &'a str }

Function returning ref must tie to input — fn get<'a>(s: &'a str) -> &'a str

Strings — UTF-8 Surprises

s[0] doesn't compile — use .chars().nth(0) or .bytes()

.len() returns bytes, not chars — use .chars().count()

s1 + &s2 moves s1 — use format!("{}{}", s1, s2) to keep both

Error Handling — Production Code

unwrap() panics — use ? or match in production

? needs Result/Option return type — main needs -> Result<()>

expect("context") > unwrap() — shows why it panicked

Iterators — Lazy Evaluation

.iter() borrows, .into_iter() moves — choose carefully

.collect() needs type — collect::>() or typed binding

Iterators are lazy — nothing runs until consumed

Concurrency — Thread Safety

Rc is NOT Send — use Arc for threads

Mutex lock returns guard — auto-unlocks on drop, don't hold across await

RwLock deadlock — reader upgrading to writer blocks forever

Memory — Smart Pointers

RefCell panics at runtime — if borrow rules violated

Box for recursive types — compiler needs known size

Avoid Rc> spaghetti — rethink ownership

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Common Compiler Errors (NEW)

| Error | Cause | Fix | |-------|-------|-----| | value moved here | Used after move | Clone or borrow | | cannot borrow as mutable | Already borrowed | Restructure or RefCell | | missing lifetime specifier | Ambiguous reference | Add <'a> | | the trait bound X is not satisfied | Missing impl | Check trait bounds | | type annotations needed | Can't infer | Turbofish or explicit type | | cannot move out of borrowed content | Deref moves | Clone or pattern match |

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Cargo Traps (NEW)

cargo update updates Cargo.lock, not Cargo.toml — manual version bump needed

Features are additive — can't disable a feature a dependency enables

[dev-dependencies] not in release binary — but in tests/examples

cargo build --release much faster — debug builds are slow intentionally