Feature suggestion: Ensure uniqness if Enum final fields

[Jens Teglhus Møller]

Hi

I often create enum's with one or more final fields where its a requirement that the field values are unique.

I have created a unit test assertion that will help verify this contract, but I feel it would be nice to have the check at compile time.

So my proposal is to have a @Unique (or similar named) annotation that you can put on any non static final field in an enum and give a compile time error if same value is discovered in more than one enum constant.

Example that should compile fine:

@Getter
@RequiredArgsConstructor
public enum Example1 {
  A("a"),
  B("b"),
  ;

  @Unique
  final String key;
}

Example that should fail due to duplicate key value:

@Getter
@RequiredArgsConstructor
public enum Example2 {
  A("a"),
  B("b"),
  C("b"),
  ;

  @Unique
  final String key;
}

Is this outside the scope of lombok?

Best regards Jens 

[Jens Teglhus Møller]

So after sleeping on it, I can of see that this will only make sense for fields that are set with constant arguments (native type, strings etc) if you pass a non deterministic function in the constructor then it cannot be determined at compile time.

It seemed like a good idea when I thought about it, but I have no idea how complex it would be to implement for constant values. It would also need some very good error messages.

Best regards Jens