[Augmentations] No error when augmenting enum has no values

[sgrekhov]

The code below produce no expected error in the analyzer.

enum E1 {
  e0;
}

augment enum E1 {}
//           ^^
// [analyzer] unspecified
// [cfe] unspecified

But enum without any values must be a syntax error (even it is an augmenting declaration).

Appropriate failing co19 test https://github.com/dart-lang/co19/blob/master/LanguageFeatures/Augmentation-libraries/augmenting_enum_values_A03_t04.dart

[eernstg]

Yes, I'd expect a syntax error for that, too. I'm not aware of any grammar updates that would allow for the list of <enumEntry> terms to be empty.