exhaustive_cases

Missing case clauses for some constants in '{0}'.

The analyzer produces this diagnostic when a switch statement over an instance of an enum-like type is missing a case clause for one or more of the type's constants and doesn't have a default clause.

Enum-like types are classes or extension types that have:

• Only private, non-factory constructors.
• Two or more static const fields whose type is the enclosing type.

In addition, an enum-like class must be non-abstract and have no subclasses in the defining library.

The following code produces this diagnostic because the switch statement is missing a case clause for the constant C.c:

class const C._(final int i) {
  static const C a = ._(1);
  static const C b = ._(2);
  static const C c = ._(3);
}
​
void f(C c) {
  switch (c) {
    case .a:
      print('a');
    case .b:
      print('b');
  }
}

Extension types can also be enum-like. The following code produces this diagnostic because the switch statement is missing a case clause for the constant E.b:

extension type const E._(int value) {
  static const E a = ._(1);
  static const E b = ._(2);
}
​
void f(E e) {
  switch (e) {
    case .a:
      print('a');
  }
}

If the missing constant needs to be handled separately, then add a case clause for it:

class const C._(final int i) {
  static const C a = ._(1);
  static const C b = ._(2);
  static const C c = ._(3);
}
​
void f(C c) {
  switch (c) {
    case .a:
      print('a');
    case .b:
      print('b');
    case .c:
      print('c');
  }
}

If the missing constant doesn't need to be handled specially, then add a default clause to cover it:

class const C._(final int i) {
  static const C a = ._(1);
  static const C b = ._(2);
  static const C c = ._(3);
}
​
void f(C c) {
  switch (c) {
    case .a:
      print('a');
    case .b:
      print('b');
    default:
      print('other');
  }
}