using hash_type = std::uint64_t;
constexpr auto fnv_basis = 14695981039346656037ull;
constexpr auto fnv_prime = 109951162821ull;

constexpr hash_type hash(const char *str, hash_type h = fnv_basis)
{
    return *str ? hash(str + 1, (h ^ *str) * fnv_prime) : h;
}

// all unregistered event types will call this function
template <hash_type Hash>
constexpr int checkRegistered()
{
    static_assert(false, "Event type is not registered");
    return 0; // because we can't do constexpr void
}

// "registration" is done by template specialization
#define REGISTER_EVENT_TYPE(type)           \
template <>                                 \
constexpr int checkRegistered<hash(type)>() \
{                                           \
    return 0;                               \
}                                           \

REGISTER_EVENT_TYPE("LevelChangedEvent")

template <hash_type EventType>
void doStuff()
{
    checkRegistered<EventType>(); // compile time check if type is registered!
    ... // do stuff
}

int main()
{
    doStuff<hash("LevelChangedEvent")>(); // ok
    doStuff<hash("HpChangedEvent")>(); // static_assert expected here
}