{
  // An array within the state of a `FabricPrimitive` renders its holes the way
  // any other array does. No shipped primitive's realm encoding holds an
  // array, so a class defined here stands in.
  "holes": (() => {
    class Holey extends FabricPrimitive {
      static get [REALM_CODEC]() {
        return {
          tagForValue: () => "Holey@1",
          encode: () => [1, , , 4, , 6],
        };
      }
    }
    return new Holey();
  })(),

  "leading and trailing holes": (() => {
    class Edges extends FabricPrimitive {
      static get [REALM_CODEC]() {
        return {
          tagForValue: () => "Edges@1",
          encode: () => {
            const list = [, 2];
            list.length = 5;
            return { list };
          },
        };
      }
    }
    return new Edges();
  })(),
}

--

holes:
/Holey([1,void*2,4,void,6])
/Holey([
  1,
  void * 2,
  4,
  void,
  6
])
/Holey([
  1,
  void * 2,
  4,
  void,
  6
])

leading and trailing holes:
/Edges(list:[void,2,void*3])
/Edges(
  list: [
    void,
    2,
    void * 3
  ]
)
/Edges(
  list: [
    void,
    2,
    void * 3
  ]
)