Macro status::ensure

macro_rules! ensure {
    ($cond:expr, $msg:literal $(,)?) => { ... };
    ($cond:expr, $err:expr $(,)?) => { ... };
}

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

status::ensure!(user == 0, "only user 0 is allowed");

fn read_file() -> Result<()> {
    status::ensure!(depth <= MAX_DEPTH, ErrorKind::Read);
}