rust-development

What this skill does

# Rust Development

Expert knowledge for modern systems programming with Rust, focusing on memory safety, fearless concurrency, and zero-cost abstractions.

## When to Use This Skill

| Use this skill when... | Use sibling skill instead when... |
|---|---|
| Writing Rust code, ownership, lifetimes, async/await | Configuring lint rules in detail -- use `clippy-advanced` |
| Choosing crates from the ecosystem (Tokio, Serde) | Detecting unused dependencies -- use `cargo-machete` |
| Designing module structure or trait hierarchies | Running tests with parallel isolation -- use `cargo-nextest` |
| Learning idiomatic Rust patterns and edition features | Generating coverage reports -- use `cargo-llvm-cov` |

## Core Expertise

**Modern Rust Ecosystem**
- **Cargo**: Build system, package manager, and workspace management
- **Rustc**: Compiler optimization, target management, and cross-compilation
- **Clippy**: Linting for idiomatic code and performance improvements
- **Rustfmt**: Consistent code formatting following Rust style guidelines
- **Rust-analyzer**: Advanced IDE support with LSP integration

**Language Features**
- Rust 2024 edition: RPITIT, async fn in traits, impl Trait improvements
- Const generics and compile-time computation
- Generic associated types (GATs)
- Let-else patterns and if-let chains

## Key Capabilities

**Ownership & Memory Safety**
- Implement ownership patterns with borrowing and lifetimes
- Design zero-copy abstractions and efficient memory layouts
- Apply RAII patterns through Drop trait and smart pointers (Box, Rc, Arc)
- Leverage interior mutability patterns (Cell, RefCell, Mutex, RwLock)
- Use Pin/Unpin for self-referential structures

**Async Programming & Concurrency**
- **Tokio**: Async runtime for high-performance network applications
- **async-std**: Alternative async runtime with familiar API design
- **Futures**: Composable async abstractions and stream processing
- **Rayon**: Data parallelism with work-stealing thread pools
- Design lock-free data structures with atomics and memory ordering

**Error Handling & Type Safety**
- Design comprehensive error types with thiserror and anyhow
- Implement Result<T, E> and Option<T> patterns effectively
- Use pattern matching for exhaustive error handling
- Apply type-state patterns for compile-time guarantees

**Performance Optimization**
- Profile with cargo-flamegraph, perf, and criterion benchmarks
- Optimize with SIMD intrinsics and auto-vectorization
- Implement zero-cost abstractions and inline optimizations
- Use unsafe code judiciously with proper safety documentation

**Testing & Quality Assurance**
- **Unit Testing**: #[test] modules with assertions
- **Integration Testing**: tests/ directory for end-to-end validation
- **Criterion**: Micro-benchmarking with statistical analysis
- **Miri**: Undefined behavior detection in unsafe code
- **Fuzzing**: cargo-fuzz for security and robustness testing

## Essential Commands

```bash
# Project setup
cargo new my-project      # Binary crate
cargo new my-lib --lib    # Library crate
cargo init                # Initialize in existing directory

# Development workflow
cargo build                      # Debug build
cargo build --release           # Optimized build
cargo run                       # Build and run
cargo run --release             # Run optimized
cargo test                      # Run all tests
cargo test --lib               # Library tests only
cargo bench                     # Run benchmarks

# Code quality
cargo clippy                    # Lint code
cargo clippy -- -W clippy::pedantic  # Stricter lints
cargo fmt                       # Format code
cargo fmt --check              # Check formatting
cargo fix                       # Auto-fix warnings

# Dependencies
cargo add serde --features derive  # Add dependency
cargo update                       # Update deps
cargo audit                        # Security audit
cargo deny check                   # License/advisory check

# Advanced tools
cargo expand                    # Macro expansion
cargo flamegraph               # Profile with flame graph
cargo doc --open               # Generate and open docs
cargo miri test                # Check for UB

# Cross-compilation
rustup target add wasm32-unknown-unknown
cargo build --target wasm32-unknown-unknown
```

## Best Practices

**Idiomatic Rust Patterns**
```rust
// Use iterators over manual loops
let sum: i32 = numbers.iter().filter(|x| **x > 0).sum();

// Prefer combinators for Option/Result
let value = config.get("key")
    .and_then(|v| v.parse().ok())
    .unwrap_or_default();

// Use pattern matching effectively
match result {
    Ok(value) if value > 0 => process(value),
    Ok(_) => handle_zero(),
    Err(e) => return Err(e.into()),
}

// Let-else for early returns
let Some(config) = load_config() else {
    return Err(ConfigError::NotFound);
};
```

**Project Structure**
```
my-project/
├── Cargo.toml
├── src/
│   ├── lib.rs        # Library root
│   ├── main.rs       # Binary entry point
│   ├── error.rs      # Error types
│   └── modules/
│       └── mod.rs
├── tests/            # Integration tests
├── benches/          # Benchmarks
└── examples/         # Example programs
```

**Error Handling**
```rust
use thiserror::Error;

#[derive(Error, Debug)]
pub enum AppError {
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),

    #[error("parse error: {message}")]
    Parse { message: String },

    #[error("not found: {0}")]
    NotFound(String),
}

pub type Result<T> = std::result::Result<T, AppError>;
```

**Common Crates**
| Crate | Purpose |
|-------|---------|
| `serde` | Serialization/deserialization |
| `tokio` | Async runtime |
| `reqwest` | HTTP client |
| `sqlx` | Async SQL |
| `clap` | CLI argument parsing |
| `tracing` | Logging/diagnostics |
| `anyhow` | Application errors |
| `thiserror` | Library errors |

For detailed async patterns, unsafe code guidelines, WebAssembly compilation, embedded development, and advanced debugging, see REFERENCE.md.