In file included from /in/driver/main.cpp:5:0:
/in/hashtable.hpp: In instantiation of 'Value& HashTable<Key, Value, Hash, KeyEqual>::operator[](const Key&) [with Key = int; Value = int; Hash = std::hash<int>; KeyEqual = std::equal_to<int>]':
/in/driver/main.cpp:129:94:   required from here
/in/hashtable.hpp:418:14: error: unused variable 'inserted' [-Werror=unused-variable]
         bool inserted = insert(it, key, Value()); // Insert the new key-value pair
              ^~~~~~~~
cc1plus: all warnings being treated as errors