Nested nullary spores

[aleloi]

This test does not compile:

@Test
def nestedPTTCaptureNullary(): Unit = {
  val s = spore{
    delayed {
      spore {
        (_: Unit) => ()
      }
      ()
    }
  }
}

If the outer nullary spore is replaced by Spore[Unit, ...] as below, it compiles:

  @Test
  def nestedPTTCapture(): Unit = {
    val s = spore{
      (_: Unit) => {
        spore {
          (_: Unit) => ()
        }
        ()
      }
    }
  }

In both cases, traverser.traverse(body) (here) is called when checking the outer spore. In both cases, the value of body is a tree that looks like (something alpha-convertible to) this when printed with showRaw:

{
  {
    class anonspore$macro$62 extends AnyRef with scala.spores.Spore[Unit,Unit] { 
      def <init>(): anonspore$macro$62 = {
        anonspore$macro$62.super.<init>();
        ()
      };
      this._className_=(this.getClass().getName());
      def apply(x$macro$61: Unit): Unit = ()
    };
    new anonspore$macro$62()
  };
  ()
}

The difference is that when the traverser goes through the constructor call anonspore$macro$62.super.<init>(), it finds an illegal This reference here in the nullary spore case. This does not happen for (_: Unit) => ...-spores.