match arms differ in mutability

[bfops]

This doesn't compile (error: match arms have incompatible types: expected &int, found &mut int (values differ in mutability))

fn main() {
    let mut x: int = 1;
    let opt: Option<int> = None;
    let rx: &int =
      match opt {
        Some(_) => {
          &x
        },
        None => {
          &mut x
        },
      };
    println!("{}", *rx);
}

But this works:

fn main() {
  let mut x: int = 1;
    let opt: Option<int> = None;
    let rx: &int =
      match opt {
        Some(_) => {
          &x
        },
        None => {
          let y: &int = &mut x;
          y
        },
      };
    println!("{}", *rx);
}

Should this "cast" be able to happen implicitly?

[steveklabnik]

Rust does not do this kind of implicit casting, no. It could be done, but that would require an RFC to change. Please pursue one if you'd like to add this to Rust, thanks!

[bfops]

Ah turns out this has been fixed. I'm not sure which RFC touched this behavior, but the first version works now.