Bug: Type checking is broken for enums

[MichaelTamm]

I think, the following code should not compile:

enum A { foo, bar }

enum B { foo, bar, baz }

void main() {
  final x = A.foo;
  print(x == B.foo ? '$x == B.foo' : '$x != B.foo');
}

... because it makes no sense to compare x (an instance of enum A) with an instance of enum B.

Link to the example in DartPad

• Dart SDK 2.19.6

[lrhn]

It is indeed statically detectable that the an instance of type A will not be equal to an instance of type B.
Because both are enum classes, which means nothing else can implement the types, and enums cannot override ==.

It's not something the language tries to prevent you from doing. After all, it works (it returns false as it should) and the == operator has parameter type Object, so it's perfectly fine to ask.
It's a little weird to make this example code not compile, but allow it if you wrote Object x = A.foo;.

The analyzer could choose to tell you that the comparison is useless. And it does, you just have to ask for it by enabling the
unrelated_type_equality_checks lint.

[MichaelTamm]

Just for reference: The Linter unrelated_type_equality_checks does not work for this example: #58653