In file included from /in/driver/main.cpp:5:0:
/in/hashtable.hpp: In member function 'HashTable<Key, Value, Hash, KeyEqual>::Iterator HashTable<Key, Value, Hash, KeyEqual>::erase(const HashTable<Key, Value, Hash, KeyEqual>::Iterator&) [with Key = int; Value = int; Hash = std::hash<int>; KeyEqual = std::equal_to<int>]':
/in/hashtable.hpp:395:5: error: control reaches end of non-void function [-Werror=return-type]
     }
     ^
cc1plus: all warnings being treated as errors