No error in CFE if extension type has two incompatible superinterfaces

[sgrekhov]

The error expected below is reported by analyzer but not reported by CFE

// SharedOptions=--enable-experiment=inline-class

extension type V1(int id) {
  int m() => 42;
}

extension type V2(int id) {
  String m() => "42";
}

extension type V(int id) implements V1, V2 {
//             ^
// [analyzer] unspecified
// [cfe] unspecified
}

main() {
  print(V);
}

Tested on the edge SDK (Aug 10, 2023) on Linux x64

[eernstg]

It's perhaps worth noting that even compatible superinterfaces won't do: There is an error as soon as an extension type member name has more than one implementation in superinterfaces and no redeclaration in the most specific extension type, also when they have exactly the same signature.

extension type V1(int id) {
  int m() => 42;
}

extension type V2(int id) {
  int m() => 42;
}

extension type V(int id) implements V1, V2 {
//             ^
// [analyzer] unspecified
// [cfe] unspecified
}

But there is no conflict if it is the same declaration:

extension type V0(int id) {
  int m() => 42;
}

extension type V1(int id) implements V0 {}
extension type V2(int id) implements V0 {}

extension type V(int id) implements V1, V2 {} // OK.