let x = match x {
Some(x) => x,
None => return None,
}
let x = x?; let x = match x {
Some(x) => x,
None => return None,
}
let x = x?;For example, look a Swift's guard statements. It even narrows the type down-scope after you short-circuit.
If you borrow in the `match {expr}`, Rust still thinks it matters when you're trying to short-circuit in the `None` branch and will complain about the borrowed lifetime. Though this is something #![feature(nll)] fixes.
You can implement std::ops::Try for a custom data structure, but that doesn't help you in any of the cases where you just want to do some day-to-day short-circuiting without inventing your own data structure.
I shouldn't have used Option, though. It was a bad example.
fn do_something() -> Box<Future<Item=(), Error=Error>> {
let val = match do_result() {
Ok(x) => x,
Err(e) => return Box::new(err(e.into())),
};
// do something with `val`
unimplemented!();
} let val = do_result().map_err(|e| Box::new(err(e.into())))?;