Macro adhocerr::ensure

macro_rules! ensure {
    ($cond:expr, $msg:literal) => { ... };
    ($cond:expr, $msg:literal?) => { ... };
    ($cond:expr, $fmt:literal, $($arg:tt)*) => { ... };
    ($cond:expr, $fmt:literal, $($arg:tt)*?) => { ... };
}

Return early with an error if a condition is not satisfied.

This macro is equivalent to if !$cond { return Err(From::from($err)); }.

Analogously to assert!, ensure! takes a condition and exits the function if the condition fails. Unlike assert!, ensure! returns an Error rather than panicking.

Example

use adhocerr::ensure;

fn main() -> Result<(), impl std::error::Error + 'static> {
    ensure!(user == 0, "only user 0 is allowed");
    Ok(())
}

use adhocerr::ensure;

fn main() -> Result<(), anyhow::Error> {
    ensure!(depth <= MAX_DEPTH, "Recursion limit exceeded"?);
    Ok(())
}