Expand description
Convenience assert!-like macros which immediately returns None or Err(...) instead of
panicking.
Examples
In a function returning an Option<T>, invoke the macro with just enough parameters to get a
condition to check.
check!(a < n);
check_eq!(a, b);This will expand to:
if !(a < n) {
return None;
}
if a != b {
return None;
}In a function returning a Result<T, E>, invoke the macro with an extra argument, which is the
error to return if the check fails (and must have type E), just like you can add arguments to
choose a panic message with assert!.
check!(a < n, MyError::TooBig);
check_eq!(a, b, MyError::NotEqual);This will expand to:
if !(a < n) {
return Err(MyError::TooBig);
}
if a != b {
return Err(MyError::NotEqual);
}Note
Actually, the two following lines are quite equivalent:
check!(a <= b);
(a <= b).then(|| ())?;