Rustc compiler freezes when creating a recursive data structure

Hello.
The following code makes the compiler freezes:

``` rust
struct Node {
    value: i32,
    left: Option<Node>,
    right: Option<Node>,
}

fn main() {
    println!("Hello, world!");
}
```

(the version with `Option<Box<Node>>` works fine, though)

Running `cargo build` takes forever. I use `rustc 1.8.0` on ArchLinux.

Thanks to fix this issue.
