void main(int x, String s, bool a) {
  switch (x) {
    case 1:
      print('one');
      break;
    case 2:
      print('two');
      break;
    case 1:
      print('duplicate one');
      break;
    case 2 when a:
      print('duplicate two');
      break;
  }

  switch (s) {
    case 'a':
      print('a');
      break;
    case 'a':
      print('duplicate a');
      break;
  }
}

void main(int x, String s, bool a, bool b) {
  switch (x) {
    case 1:
      print('one');
      break;
    case 2:
      print('two');
      break;
    default:
      print('other');
  }

  switch (s) {
    case 'a':
      print('a');
      break;
    case 'b':
      print('b');
      break;
  }

  switch (x) {
    case 1 when a:
      print('one-a');
      break;
    case 1 when b:
      print('one-b');
      break;
  }

  switch (x) {
    case 1:
      print('again');
      break;
  }

  // Guarded case before a plain case: the plain `case 1:` is still reachable
  // (it matches when the guard is false), so nothing is flagged.
  switch (x) {
    case 1 when a:
      print('one-a');
      break;
    case 1:
      print('one');
      break;
  }
}