rspec/rules/S3562/dart/rule.adoc

== Why is this an issue?

For completeness, a ``++switch++``  over the values of an ``++enum++`` must either address each value in the ``++enum++`` or contain a ``++default++`` case. ``++switch++`` statements that are not over ``++enum++`` must end with a ``++default++`` case. This exhaustiveness is enforced by compiler. However, in the code there might be other enum-like classes which are not enums according to compiler, but sthe switch over its constants was intended to be exhaustive.

This rule with raise an issue when switch over such enum-like classes doesn't cover all cases.

Enum-like classes are classes that:

* are defined as non-abstract;
* have only one private non-factory constructor
* have two or more static const fields whose type is the enclosing class and
no subclasses of the class is in the defining library


=== Noncompliant code example

[source,dart]
----
class MyEnum {
  final int i;
  const EnumLike._(this.i);

  static const a = MyEnum._(1);
  static const b = MyEnum._(2);
  static const c = MyEnum._(3);
}

void foo(MyEnum e) {
  switch(e) { // Noncompliant, case 'b' is missing
    case MyEnum.a:
      print('a');
    case MyEnum.b:
      print('b');
  }
}
----


=== Compliant solution

[source,dart]
----
class MyEnum {
  final int i;
  const EnumLike._(this.i);

  static const a = MyEnum._(1);
  static const b = MyEnum._(2);
  static const c = MyEnum._(3);
}

void foo(MyEnum e) {
  switch(e) {
    case MyEnum.a:
      print('a');
    case MyEnum.b:
      print('b');
    case MyEnum.c:
      print('c');
  }
}
----
or

[source,dart]
----
class MyEnum {
  final int i;
  const EnumLike._(this.i);

  static const a = MyEnum._(1);
  static const b = MyEnum._(2);
  static const c = MyEnum._(3);
}

void foo(MyEnum e) {
  switch(e) {
    case MyEnum.a:
      print('a');
      break;
    case MyEnum.b:
      print('b');
      break;
    default:
      print('default');
  }
}
----


== Resources

* https://dart.dev/tools/linter-rules/exhaustive_cases[Dart Lint rule]
* https://dart.dev/language/branches#exhaustiveness-checking[Exhaustiveness checking]