<group-clab> doesn't work if the list of <button-clab>s is set by a dom-repeat template

[Arual90]

This works

<group-clab>
  <button-clab>[[buttons.0.name]]</button-clab>
  <button-clab>[[buttons.1.name]]</button-clab>
</group-clab>

This doesn't work

<group-clab>
  <template is="dom-repeat" items="[[buttons]]" as="btn">
    <button-clab>[[btn.name]]</button-clab>
  </template>
</group-clab>

[moebiusmania]

can't work out of the box, the <template is="dom-repeat">is Polymer-specific syntax but the <group-clab>environment could be different.

I'm searching for another solution...