Method add_op

crates/gitql-core/src/values/date.rs:53–60

(&self, other: &Box<dyn Value>)

    }

    fn add_op(&self, other: &Box<dyn Value>) -> Result<Box<dyn Value>, String> {
        if let Some(days) = other.as_int() {
            let days_to_timestamp = days * 24 * 60 * 60;
            let timestamp = self.timestamp + days_to_timestamp;
            return Ok(Box::new(DateValue::new(timestamp)));
        }
        Err("Unexpected type to perform `+` with".to_string())
    }

    fn sub_op(&self, other: &Box<dyn Value>) -> Result<Box<dyn Value>, String> {
        if let Some(days) = other.as_int() {