Throw Exception on Error

To deliberately return an error, use the throw keyword.

if some_bad_condition_has_happened {
    throw error;    // 'throw' any value as the exception
}

throw;              // defaults to '()'

Catch a Thrown Exception

It is possible to catch an exception, instead of having it abort the script run, via the try … catch statement common to many C-like languages.

fn code_that_throws() {
    throw 42;
}

try
{
    code_that_throws();
}
catch (err)         // 'err' captures the thrown exception value
{
    print(err);     // prints 42
}