Macro unwrap::unwrap_err

macro_rules! unwrap_err {
    ($e:expr) => { ... };
    ($e:expr, $($arg:tt)*) => { ... };
}

A replacement for calling unwrap_err() on a Result.

This macro is intended to be used in all cases where one would unwrap_err a Result to deliberately panic in case of unexpected non-error, e.g. in test-cases. Such unwrap_errs don't give a precise point of failure in the code and instead indicate some line number in the Rust core library. This macro provides a precise point of failure and decorates the failure for easy viewing.

Examples

let some_result = Err::<u64, String>("Failed".to_string());
let string_length = unwrap_err!(some_result, "This is an optional user-supplied text.").len();
assert_eq!(string_length, 6);