wtf, rust?

gistfile1.txt

// Config.rs:34

fn save_PrettyJSON<'a, T: Encodable<json::PrettyEncoder<'a>>>(p: &Path, toEncode: ~[T]) {
    match File::create(p) {
        Some(f) => {
            let f2 = @mut f as @mut io::Writer;
            let a = &mut json::PrettyEncoder::init(f2);
            toEncode.encode(a);
        }, None => fail!("failed to save json")
    };
}

#[feature(managed_boxes)];

struct Whatever<'a> { w: &'a mut std::io::Writer }
impl <'a> Whatever<'a> {
    fn new<'b>(w: &'b mut std::io::Writer) -> Whatever<'b> {
        Whatever { w: w }
    }
}

fn save_PrettyJSON(p: &Path) {
    match std::io::File::create(p) {
        Some(f) => {
            let mut f2 = f;
            let a = &mut Whatever::new(@mut f2 as @mut std::io::Writer);
        },
        None => fail!()
    };
}

fn main() {
    save_PrettyJSON(&Path::init("sntahoeu"));
}

#[feature(managed_boxes)];

struct DroppableStruct;
impl Drop for DroppableStruct {
    fn drop(&mut self) {
        println!("Dropping");
    }
}

trait MyTrait { }
impl MyTrait for DroppableStruct {}


struct Whatever<'a> { w: &'a mut MyTrait }
impl <'a> Whatever<'a> {
    fn new<'b>(w: &'b mut MyTrait) -> Whatever<'b> {
        Whatever { w: w }
    }
}

fn main() {
    let mut f = DroppableStruct;
    let _a = &mut Whatever::new(@mut f as @mut MyTrait);
}