Not include abstract classes in type switch

[BbIXOD]

To reproduce

1. create base abstract class
2. create one or more derivatives
3. switch variable of type Base by type in case where you need to implement complete match

Example

abstract class Base {}

class Derived extends Base {}

class AnotherDerived extends Base {}

Base? foo(Base b) {
  return switch (b) {
    Derived _ => null,
    AnotherDerived _ => null,
    // without this we have trouble: Base _ => null,
  };
}

Expected behavior

Linter does not complain, everything is fine

Actual behavior

Linter complains that match is not complete

[julemand101]

As far as I know, this works as intended. Your Base class are not sealed so if some other code would import your code and make another subclass of Base, then your foo function would no longer handle all possible cases.

It would then result in bad developer experience if making a subclass could give a compile error from inside the library you are using.

I recommend reading about the different class modifiers to learn about how to put restrictions on what is allowed to do with classes: https://dart.dev/language/class-modifiers

[lrhn]

What @julemand101 says. If you want a switch over the subclasses to be able to exhaust the superclass, the superclass must be marked sealed. Then it also works, so the feature already exists.