You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/rust-farm/101/loooops/src
    
    the code of the file until where you have to start completion: use rand::Rng;

#[cfg(test)]
mod tests {
    use crate::*;

    #[test]
    fn valid_rngsum_test() {
        // unwrap ile Result içerisindeki Ok değerini alırız.
        let result = rngsum(1, 6).unwrap();
        assert_eq!(result, 21);
    }

    #[test]
    fn invalid_range_rng
    
pub fn rngsum(start: i32, stop: i32) -> Result<i32, CalculationError> {
    // start, stop ikilisini kıyasladığımız matching
    match (start, stop) {
        (s, e) if s > e => Err(CalculationError::InvalidRange),
        (s, e) if s == e => Err(CalculationError::InvalidSpacing),
        (s, e) => {
            let mut total = 0;
            // basit olarak s değerine e değerine kadar giden bir döngü
            for n in s..=e {
                total += n;
            }
            Ok(total)
        }
    }
    /*    if start > stop {
        Err(CalculationError::InvalidRange)
    } else if start == stop {
        Err(CalculationError::InvalidSpacing)
    } else {
        let mut total = 0;
        for n in start..=stop {
            total += n;
        }
        Ok(total)
    }*/
}