anchor.diff:      use dynamicVm = new DesktopBindingTarget()
       dynamicVm.BindView "Test" v2
   
  -    let obs = PropertyChangedObserver()
  -    obs.Subscribe dynamicVm
  +    let obs = PropertyChangedObserver(dynamicVm)    
       
       let props = TypeDescriptor.GetProperties(dynamicVm)
       let prop = props.Find("Test", false)
  
positive.code:     use bt = new TestBindingTarget()
  
      let value = Mutable.create 0
      let obs = PropertyChangedObserver()
      obs.Subscribe bt
  
      let ibt = bt :> IBindingTarget
  
  
negative.code:     use dynamicVm = new DesktopBindingTarget()
      dynamicVm.BindMutable "Test" v1
  
      let obs = PropertyChangedObserver(dynamicVm)    
      
      let props = TypeDescriptor.GetProperties(dynamicVm)
      let prop = props.Find("Test", false)
  