Parameterized type lost when going through interface

[peter-ahe-google]

The program below produces an error:

1
2
Unhandled exception:
0 is not a T
 0. Function: 'AbstractLink.prepend' url: '/Users/ahe/Dart/all/dart.googlecode.com/dart/frog/fisk.dart' line:21 col:7
 1. Function: '::.main' url: '/Users/ahe/Dart/all/dart.googlecode.com/dart/frog/fisk.dart' line:43 col:49

If I change the method prepend to return "new LinkEntry<T>" instead of "new Link<T>" it works.

interface Link<T> extends Iterable<T> factory LinkFactory {
  Link(T head, [Link<T> tail]);
  Link<T> prepend(T element);
}

interface EmptyLink<T> extends Link<T> factory LinkTail<T> {
  const EmptyLink();
}

class LinkFactory {
  factory Link<T>(head, [Link tail]) {
    return new LinkEntry<T>(head, tail);
  }
}

class AbstractLink<T> implements Link<T> {
  const AbstractLink();
  Link<T> prepend(T element) {
    print("$element");
    if (0 is T) {
      throw "0 is not a T";
    }
    return new Link<T>(element, this);
  }
}

class LinkTail<T> extends AbstractLink<T> implements EmptyLink<T> {
  const LinkTail();
}

class LinkEntry<T> extends AbstractLink<T> {
  LinkEntry(T head, Link<T> realTail);
}

class Fisk {
  Link<String> nodes = const EmptyLink<Fisk>();
  final int id;
  Fisk(this.id);
  toString() => id.toString();
}

main() {
  new Fisk(0).nodes.prepend(new Fisk(1)).prepend(new Fisk(2));
}

[crelier]

Fixed in r1662.

---

Set owner to @crelier.
Added Fixed label.