no_default_cases

Invalid use of 'default' member in a switch.

The analyzer produces this diagnostic when a switch statement over an enum value or an instance of an enum-like class has a default clause.

Enum-like classes are non-abstract classes that have:

• Only private, non-factory constructors.
• Two or more static const fields whose type is the enclosing class.
• No subclasses in the defining library.

The following code produces this diagnostic because the switch statement over the enum value e has a default clause:

enum E { a, b, c }
​
void f(E e) {
  switch (e) {
    case .a:
      print('a');
    default:
      print('other');
  }
}

The following code produces this diagnostic because the switch statement over c, an instance of the enum-like class C, has a default clause:

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');
    default:
      print('other');
  }
}

If the value is an enum value, replace the default clause with case clauses for the enum values that aren't already handled:

enum E { a, b, c }
​
void f(E e) {
  switch (e) {
    case .a:
      print('a');
    case .b:
    case .c:
      print('other');
  }
}

If the value is an instance of an enum-like class, replace the default clause with case clauses for the constants that aren't already handled:

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:
    case .c:
      print('other');
  }
}