null created by danieluranga - https://repl.it/HkrZ/3

HkrZ-3.cpp

#include <iostream>

enum Id
{
  A, B, C, D
};

struct Data
{
  Id id;
  const char* val;
};

constexpr Data arr[] =
{
  {A, "test"},
  {B, "otra cosa"},
  {C, "tercera"},
};

constexpr int arrLength() { return sizeof(arr) / sizeof(arr[0]); }

template<Id id, int index>
struct findById2
{
  static constexpr const Data* value = (id == arr[index].id) ? &arr[index] : findById2<id, index + 1>::value;
};

template<Id id>
struct findById2<id, arrLength()>
{
  static constexpr const Data* value = id == arr[arrLength() - 1].id ? arr : nullptr;
};

template<Id id>
struct findById
{
  static constexpr const Data* value = findById2<id, 0>::value;
};

int main()
{
  std::cout << "A: " << findById<A>::value->val << std::endl;
  std::cout << "B: " << findById<B>::value->val << std::endl;
  std::cout << "C: " << findById<C>::value->val << std::endl;
  static_assert(findById<C>::value != nullptr, "err");
}