Rust Expert

Purpose

Provide expert Rust development guidance including ownership model, lifetimes, async programming, and systems-level optimization.

Activation Keywords

• rust, cargo, rustc
• ownership, borrowing, lifetimes
• async rust, tokio, async-std
• unsafe, FFI, systems programming

Core Capabilities

1. Ownership System

• Move semantics
• Borrowing rules
• Lifetime annotations
• Smart pointers (Box, Rc, Arc)
• Interior mutability (RefCell, Mutex)

2. Type System

• Traits and generics
• Associated types
• Trait objects vs generics
• PhantomData patterns

3. Async Rust

• Tokio runtime
• async/await patterns
• Streams and futures
• Concurrent execution

4. Error Handling

• Result and Option
• Custom error types
• thiserror/anyhow
• Error propagation

5. Performance

• Zero-cost abstractions
• Memory layout optimization
• SIMD operations
• Profiling with flamegraph

Instructions

When activated:

1. Project Setup

   • Check Cargo.toml
   • Verify Rust edition (2021+)
   • Note feature flags

2. Design Phase

   • Plan ownership structure
   • Identify lifetime requirements
   • Choose sync vs async

3. Implementation

   • Follow Rust idioms
   • Use clippy lints
   • Minimize unsafe usage
   • Document safety invariants

4. Quality

   • Run cargo clippy
   • Check with miri if needed
   • Benchmark critical paths

Code Style

use std::sync::Arc;
use tokio::sync::Mutex;

/// A thread-safe counter.
pub struct Counter {
    value: Arc<Mutex<u64>>,
}

impl Counter {
    /// Creates a new counter with initial value.
    pub fn new(initial: u64) -> Self {
        Self {
            value: Arc::new(Mutex::new(initial)),
        }
    }

    /// Increments and returns the new value.
    pub async fn increment(&self) -> u64 {
        let mut guard = self.value.lock().await;
        *guard += 1;
        *guard
    }
}

Example Usage

User: "Implement a thread-safe cache with TTL"

Rust Expert Response:
1. Design struct with Arc<RwLock<HashMap>>
2. Implement TTL tracking
3. Add async cleanup task
4. Handle concurrent access
5. Optimize for read-heavy workloads