In file included from /in/driver/main.cpp:5:0:
/in/hashtable.hpp: In instantiation of 'bool HashTable<Key, Value, Hash, KeyEqual>::insert(const HashTable<Key, Value, Hash, KeyEqual>::Iterator&, const Key&, const Value&) [with Key = int; Value = int; Hash = std::hash<int>; KeyEqual = std::equal_to<int>]':
/in/hashtable.hpp:312:22:   required from 'bool HashTable<Key, Value, Hash, KeyEqual>::insert(const Key&, const Value&) [with Key = int; Value = int; Hash = std::hash<int>; KeyEqual = std::equal_to<int>]'
/in/driver/main.cpp:111:43:   required from here
/in/hashtable.hpp:287:26: error: passing 'const HashTable<int, int, std::hash<int>, std::equal_to<int> >::Iterator' as 'this' argument discards qualifiers [-fpermissive]
             auto &node = *it;
                          ^~~
In file included from /in/driver/main.cpp:5:0:
/in/hashtable.hpp:122:19: note:   in call to 'HashTable<Key, Value, Hash, KeyEqual>::HashNode& HashTable<Key, Value, Hash, KeyEqual>::Iterator::operator*() [with Key = int; Value = int; Hash = std::hash<int>; KeyEqual = std::equal_to<int>; HashTable<Key, Value, Hash, KeyEqual>::HashNode = std::pair<const int, int>]'
         HashNode &operator*() {
                   ^~~~~~~~