dart How to get an enum with index?

Question

I defined an enum:

enum TestEnum {
  test1,
  test2,
}

and I want make an enum with index:

E buildEnum<E extends ?????????????????>(int index) {
  try {
    return E.values[index];
  }
  catch(e) {
    return null;
  }
}

I don't know the type of enum.

Answer 1

enum A { a0, a1, a2 }
A.values[index]

// e.g: A.values[0] == A.a0