!7

p {
  final Alt<S, Int> a = alt1('Hello);
  final Alt<S, Int> b = alt2(123);
  
  assertTrue(a.isA());
  assertFalse(a.isB());
  assertFalse(b.isA());
  assertTrue(b.isB());
  
  assertEqualsVerbose('Hello, a.a());
  assertFail(r { a.b() });
  
  assertEqualsVerbose(123, b.b());
  assertFail(r { b.a() });
  
  print("OK!");
}