anchor.diff:          and set newValue = setValue newValue |> ignore
   
       /// Sets the value; use when a return value is required to determine if the value has changed.
  -    member x.Set newValue = set newValue
  +    member x.Set newValue = setValue newValue
  
positive.code:                 true
          | _ -> failwith "Unexpected expression type; needs PropertyGet"
  
  and FieldBacker<'T>(om: ObservableBase, propertyExpr) =
      let mutable value = Unchecked.defaultof<'T>
      let propertyName = 
          match propertyExpr with
          | PropertyGet(_, propOrValInfo, _) -> propOrValInfo.Name
  
negative.code:         [<CLIEvent>]
          member x.PropertyChanged = propertyChanged.Publish
  
      member x.MakeField<'T>(propertyExpr, ?initialValue: 'T) = // TODO would rather have protected mfunc or func
          new FieldBacker<'T>(x, propertyExpr, initialValue)
  
      // Used by FieldBacker
      member internal x.NotifyPropertyChanged(propertyName) =
  