core::try!

macro_rules! try {
    ($e:expr) => ({
        use $crate::result::Result::{Ok, Err};

        match $e {
            Ok(e) => e,
            Err(e) => return Err(e),
        }
    })
}

Short circuiting evaluation on Err

libstd contains a more general try! macro that uses FromError.