Analyzer does not warn of missing exhaustiveness when combining sealed classes and enums.

[lrhn]

The analyzer correctly warns if any of the cases are removed from these switches, and not if all the cases are present:

enum E {a, b;}
sealed class S {}
class C1 implements S {}
class C2 implements S {}

void main() {
  E e = E.a as dynamic;
  switch (e) {
     case E.a: 
     case E.b:
  }
  S s = C1() as dynamic;
  switch (s) {
    case C1 _:
    case C2 _:
  }
}

However, it does not recognize a missing enum entry if it's combined with another type:

sealed class SE {}
class C3 implements SE {}
enum EE implements SE {a, b;}

void main() {
  SE se = EE.a as dynamic;
  switch (se) {
    case C3 _:
    // case EE.a:
    case EE.b:
  }
}

Here commenting out the EE.a or EE.b case does not give any errors in the analyzer. The CFE does give the correct error of a missing EE.a case.

Even commenting out both EE.? cases doesn't give an error.

It looks like the analyzer simply misses that an enum declaration can also introduce a subtype of a sealed type which should be included in exhaustiveness.

Checking the code ... yes, that is the problem. And it also mixes mixins:

sealed class S {}

class C1 implements S {}
mixin M2 implements S {}
class C3 with M2 {}

void main() {
  S s = C1() as dynamic;
  switch (s) {
    case C1 _:
    // case M2 _:  // No error from analyzer.
  }
} 

[bwilkerson]

@scheglov

[scheglov]

https://dart-review.googlesource.com/c/sdk/+/298260