Compiling this code returns Internal error: e2ir.c 118.

    class Owner {

      this() {
        nested_ = new Nested(this);
      }

      class Nested {

        this(Owner owner) {
        }

      }

      private Nested nested_;

    }

    class OwnerDerived : Owner {
    }

I suggest the error should be something like "constructor not allowed on class Nested, try 'static class' instead"? Another problem is that if you leave out the OwnerDerived declaration, it compiles ok.