non_final_field_in_enum

Enums can only declare final fields.

The analyzer produces this diagnostic when an instance field in an enum isn't marked as final.

The following code produces this diagnostic because the field f isn't a final field:

enum E {
  c;

  int f = 0;
}

If the field must be defined for the enum, then mark the field as being final:

enum E {
  c;

  final int f = 0;
}

If the field can be removed, then remove it:

enum E {
  c
}