XXX not complete

  ? interface Foo guards FooStamp {}
  # value: Foo
  
  ? interface Bar {}
  # value: <Bar advisory guard/stamp>
  
  ? Foo :DeepFrozen
  # value: Foo
  
  ? FooStamp :DeepFrozen
  # value: <Foo stamp>
  
  ? [Foo.getDocComment()]
  # value: [null]

  ? [Bar.getDocComment()]
  # value: [null]