static <A extends Concept> ConceptRefToVar<A> conceptRefToVar(Concept.Ref<A> ref) {
  ret new ConceptRefToVar<A>(ref);
}

sclass ConceptRefToVar<A extends Concept> is IVarWithNotify<A> {
  Concept.Ref<A> ref;
  event fireChange;
  
  *(Concept.Ref<A> *ref) {
    ref.concept().onChange(l0 fireChange);
  }
  
  public void set(A a) { ref.set(a); }
  public A get() { ret ref!; }
}