Polymer core-selector does not refresh - dart

Question

The Dart code for my Polymer element looks like this:
#CustomTag('my-element')
class MyElement extends PolymerElement {
final List<String> colors = toObservable(['red', 'green', 'blue']);
MyElement.created() : super.created();
}
And the HTML looks like this:
<polymer-element name="my-element">
<template>
<style>
.core-selected {
font-weight: bold;
}
</style>
<core-selector id="selector" selected="1">
<template repeat="{{color in colors}}">
<div value="{{color}}">{{color}}</div>
</template>
</core-selector>
<hr>
<!-- Prints the selected index, but does not update -->
<div>{{$['selector'].selected]}}</div>
</template>
<script type="application/dart" src="my_element.dart"></script>
</polymer-element>
Using <div>{{$['selector'].selected]}}</div> correctly shows the index of the selected color, but picking a different color does not refresh the value of selected. Am I using this correctly? Or is this a bug?

Answer 1

I agree it's a bug, but in the meantime you can work around it like this
<core-selector id="selector" selected="{{selected}}">
...
<div>{{selected}}</div>
with the backing code containing the obvious
#observable int selected = 1;
I do wonder if your version works when used in a pure JS environment? But that's another question.