# Rust Language Support

AI Distiller provides support for Rust codebases using both tree-sitter and line-based parsing, with comprehensive support for Rust's ownership system, traits, generics, and modern language features.

## Overview

Rust support in AI Distiller captures the essential structure of Rust code including ownership annotations, lifetime parameters, trait bounds, and async constructs. The distilled output preserves Rust's type safety and memory safety guarantees while optimizing for AI comprehension.

## Supported Rust Constructs

### Core Language Features

| Construct | Support Level | Notes |
|-----------|--------------|-------|
| **Structs** | ✅ Full | Including tuple structs, generics |
| **Enums** | ✅ Full | With variants and associated data |
| **Traits** | ✅ Full | Including associated types, supertraits |
| **Implementations** | ✅ Full | Inherent and trait implementations |
| **Functions** | ✅ Full | Free functions, methods, closures |
| **Type Aliases** | ✅ Full | Including generic type aliases |
| **Modules** | ✅ Full | Inline and file modules |
| **Use statements** | ✅ Full | Including renames and globs |
| **Macros** | ⚠️ Partial | Macro definitions detected, not expanded |
| **Async/Await** | ✅ Full | Async functions and blocks |
| **Unsafe** | ✅ Full | Unsafe functions and blocks marked |

### Type System Features

| Feature | Support Level | Notes |
|---------|--------------|-------|
| **Lifetimes** | ✅ Full | Including `'static`, elided lifetimes |
| **References** | ✅ Full | `&T`, `&mut T`, `&'a T` |
| **Generic parameters** | ✅ Full | Type, lifetime, const generics |
| **Trait bounds** | ✅ Full | Including `where` clauses |
| **Associated types** | ✅ Full | In traits and implementations |
| **Return types** | ✅ Full | Including `impl Trait`, `-> Result<T, E>` |
| **Self types** | ✅ Full | `self`, `&self`, `&mut self`, `&'a self` |

## Recent Fixes (2025-06-15)

1. **&self parameters missing** (✅ Fixed)
   - **Issue**: Methods with lifetime-annotated self like `&'a self` were missing parameters
   - **Fix**: Enhanced `isSelfParameter()` to handle complex self patterns
   - **Impact**: All self parameter variations now correctly displayed

2. **Complex return types cut off** (✅ Fixed)
   - **Issue**: Return types like `-> Option<HashMap<String, Vec<T>>>` were truncated
   - **Fix**: Changed regex from non-greedy to greedy matching
   - **Impact**: Full return type signatures preserved

3. **Generic return types** (✅ Fixed)
   - **Issue**: Generic parameters in return types were not captured
   - **Fix**: Improved return type extraction in line parser
   - **Impact**: Complete generic type information shown

4. **Trait methods showing `pub`** (✅ Fixed)
   - **Issue**: Methods in trait definitions incorrectly showed `pub` keyword
   - **Fix**: Added context detection to suppress visibility in traits
   - **Impact**: Idiomatic Rust trait syntax

## Key Features

### 1. **Ownership and Borrowing Representation**

```rust
// Input
impl<'a> Parser<'a> {
    pub fn new(input: &'a str) -> Self {
        Self { input, position: 0 }
    }
    
    pub fn parse(&mut self) -> Result<Ast, ParseError> {
        // implementation
    }
    
    fn consume(&mut self, expected: &str) -> Option<&'a str> {
        // implementation
    }
}
```

```
// Output (default)
impl<'a> Parser<'a> {
    pub fn new(input: &'a str) -> Self
    pub fn parse(&mut self) -> Result<Ast, ParseError>
}
```

### 2. **Trait Definitions and Implementations**

```rust
// Input
pub trait Serialize: Sized {
    type Error: std::error::Error;
    
    fn serialize<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error>;
    
    fn to_bytes(&self) -> Result<Vec<u8>, Self::Error> {
        let mut buf = Vec::new();
        self.serialize(&mut buf)?;
        Ok(buf)
    }
}

impl<T: Display> Serialize for T {
    type Error = std::io::Error;
    
    fn serialize<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error> {
        write!(writer, "{}", self)
    }
}
```

```
// Output
pub trait Serialize: Sized {
    type Error: std::error::Error;
    fn serialize<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error>;
    fn to_bytes(&self) -> Result<Vec<u8>, Self::Error>
}

impl<T: Display> Serialize for T {
    type Error = std::io::Error;
    fn serialize<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error>
}
```

### 3. **Async and Error Handling**

```rust
// Input
#[derive(Debug, thiserror::Error)]
pub enum ApiError {
    #[error("Network error: {0}")]
    Network(#[from] reqwest::Error),
    #[error("Parse error: {0}")]
    Parse(#[from] serde_json::Error),
}

pub async fn fetch_user(id: u64) -> Result<User, ApiError> {
    let response = client.get(&format!("/users/{}", id)).send().await?;
    let user = response.json::<User>().await?;
    Ok(user)
}
```

```
// Output
#[derive(Debug, thiserror::Error)]
pub enum ApiError {
    Network(reqwest::Error),
    Parse(serde_json::Error),
}

pub async fn fetch_user(id: u64) -> Result<User, ApiError>
```

## Visibility Rules

Rust visibility in AI Distiller:
- **pub**: Public, accessible from outside module
- **pub(crate)**: Visible within the crate
- **pub(super)**: Visible in parent module
- **pub(in path)**: Visible in specific path
- **(default)**: Private to the module

## Known Limitations

1. **Macro expansion**: Macros are detected but not expanded
2. **Const generics**: Complex const generic expressions may not be fully captured
3. **Pattern matching**: Match expressions in implementations are simplified
4. **Inline assembly**: `asm!` blocks are not parsed
5. **Procedural macros**: Attribute macros are shown but not processed

## Best Practices

### 1. **Explicit Lifetime Annotations**

While Rust allows lifetime elision, explicit lifetimes help AI understanding:

```rust
// Good for AI comprehension
pub fn parse<'a>(input: &'a str) -> Result<Token<'a>, Error>

// Less clear (though valid Rust)
pub fn parse(input: &str) -> Result<Token, Error>
```

### 2. **Clear Trait Bounds**

Use descriptive trait bounds:

```rust
// Good
pub fn process<T: Serialize + Send + 'static>(item: T) -> Result<(), Error>

// Better with where clause for complex bounds
pub fn process<T>(item: T) -> Result<(), Error>
where
    T: Serialize + Send + 'static,
    T::Error: From<std::io::Error>,
```

### 3. **Module Organization**

Structure modules for clear API boundaries:

```rust
pub mod api {
    pub struct Client { /* ... */ }
    pub trait Handler { /* ... */ }
}

mod internal {  // Private implementation details
    pub(super) fn helper() { /* ... */ }
}
```

## Output Examples

<details>
<summary>Complex Generic System</summary>

Input:
```rust
pub struct Cache<K, V, S = RandomState> 
where 
    K: Hash + Eq,
    V: Clone,
    S: BuildHasher,
{
    map: HashMap<K, V, S>,
    capacity: usize,
}

impl<K, V, S> Cache<K, V, S>
where
    K: Hash + Eq,
    V: Clone,
    S: BuildHasher,
{
    pub fn with_hasher(capacity: usize, hasher: S) -> Self {
        Self {
            map: HashMap::with_hasher(hasher),
            capacity,
        }
    }
    
    pub fn get(&self, key: &K) -> Option<&V> {
        self.map.get(key)
    }
    
    pub fn insert(&mut self, key: K, value: V) -> Option<V> {
        if self.map.len() >= self.capacity {
            self.evict_oldest();
        }
        self.map.insert(key, value)
    }
    
    fn evict_oldest(&mut self) {
        // implementation
    }
}
```

Output (default):
```
pub struct Cache<K, V, S = RandomState>
where
    K: Hash + Eq,
    V: Clone,
    S: BuildHasher,
{
    -map: HashMap<K, V, S>
    -capacity: usize
}

impl<K, V, S> Cache<K, V, S>
where
    K: Hash + Eq,
    V: Clone,
    S: BuildHasher,
{
    pub fn with_hasher(capacity: usize, hasher: S) -> Self
    pub fn get(&self, key: &K) -> Option<&V>
    pub fn insert(&mut self, key: K, value: V) -> Option<V>
}
```

</details>

## Integration Tips

### For AI Code Review
```bash
# Get public API surface
aid src/ --private=0 --protected=0 --internal=0 --implementation=0

# Include trait implementations  
aid src/ --format text --output rust-api.txt
```

### For Documentation Generation
```bash
# Extract all public items with doc comments
aid src/ --private=0 --protected=0 --internal=0 --comments=1
```

## Future Improvements

- Full macro expansion support
- Better const generic handling
- Improved async trait support
- Pattern matching in function signatures
- Integration with cargo metadata

## Contributing

Rust support is actively maintained. Key areas for contribution:
- Macro system integration
- Complex lifetime scenarios
- Const generic expressions
- Async trait implementations

See [CONTRIBUTING.md](../../CONTRIBUTING.md) for development setup.