# make_fields

Tiny derive macro inspired by `makeFields` from the
[lens](https://hackage.haskell.org/package/lens-5.2.2) library.

Rust's lack of higher kinded types prevents us from doing cool things like
monadic tagless final, free monads or monad transformers.

I have found that using traits or typeclasses to describe generically what
your functions need is sometimes enough in the abscence of these commodities.

Thus, this crate.

## Example

```rust
use make_fields::HasFields;

// This will create immutable accessors for all fields, plus a trait
// indicating that some T "Has" that field.

#[derive(HasFields)]
struct AppConfig {
    db: HashMap<String, String>,
    port: u16,
    host: String,
}

// Now we can write our function generically like this, which makes it
// easier to write test using a mock object or something.

fn connect_to_server<T>(cfg: &T)
where
    T: HasPort<Port = u16> + HasHost<Host = String>,
{
    // ...
}
```

## Contributing

Please feel free to open an issue or PR if you think you can make `make_fields`
better!

## License

MIT