Rust code - type error.

rust-json.rs

fn getString(json: std::json::Json, key: ~str) -> Option<~str> {
  match json {
		std::json::Object(map) => {
			match map.find(&key) {
				Some(&std::json::String(str)) => Some(~"return str here"),
				_ => None
			}
		},
		_ => None
	}
}

rust-json.rs:15:28: 15:32 error: by-move pattern bindings may not occur behind @ or & bindings
rust-json.rs:15 Some(&std::json::String(str)) => Some(~"return str here"),
^~~~
error: aborting due to previous error