guard let value = optvalue else {
        return // optvalue is none
    }

I'm using this in my own code now to unwrap or return (it looks stupid):

        let value = if let Some(value) = optvalue {
            value
        } else { // optvalue is none
            return;
        };

[2] https://github.com/rust-lang/rfcs/issues/2616

[3] https://github.com/rust-lang/rfcs/pull/1303

    let value = match value {
        None => return,
        Some(value) => value
    };

  let value = value.ok_or(MyError)?;

    fn process_file(p: Path) -> Result<String, io::Error> {
        let file = File::open(p)?; //Return err if file can't be opened
        let mut out = String::new();
        file.read_to_string(&mut out)?; // Return err if read fails
        out
    }

[0] https://doc.rust-lang.org/nightly/unstable-book/language-fea...

[1] https://github.com/rust-lang/rust/issues/31436

  loop {
    let thing = match foo() {
      Some(bar) => bar,
      None => continue,
    }
  }

(in the context of walking a tree...):

    fn get_depth(root_opt: &Option<Box<TreeNode>>) -> usize {
        let root = match root_opt {
            Some(root) => root,
            None => return 0;
        };

        1 + std::cmp::max(get_depth(root.borrow().left), get_depth(root.borrow().right))
    }

    // want to do this
    if not let Some("pattern") = val {
        doSomething();
    }

    // can instead do
    if !matches!(val, Some("pattern")) {
        doSomething();
    }

``` let x = Some(1); let x = match x { Some(x) => x, None => return, };

assert_eq!(x, 1); ```