after.rs

cache.entry(sql).or_insert_with_result(|sql| {
    Statement::prepare(&self.raw_connection, &sql)
        .map(CachedStatement::new)
}).clone()

before.rs

match cache.entry(sql) {
    Occupied(entry) => Ok(entry.get().clone()),
    Vacant(entry) => {
        let statement = try!(Statement::prepare(&self.raw_connection, entry.key()));
        Ok(entry.insert(CachedStatement::new(statement)).clone())
    }
}