Macro bail 

macro_rules! bail {
    ($e:expr) => { ... };
}

Return early with an error.

Modelled after anyhow::bail.

Example

use homestar_invocation::{bail, Error, Unit};

fn has_permission(user: usize, resource: usize) -> bool {
     true
}


if !has_permission(user, resource) {
    bail!(Error::Unknown);
}