anchor.diff:  
       if (FAILED(hr)) throw WindowsException(hr);
   
  -    return IVector(retValuePtr);
  +    return IVector(retValuePtr, allocator: allocator);
     }
   
     Pointer<COMObject> PickSingleFileAsync() {
  
positive.code:   }
  
    IVector<String> get FileTypeFilter {
      final retValuePtr = calloc<COMObject>();
  
      final hr = ptr.ref.lpVtbl.value
          .elementAt(14)
  
negative.code: /// {@category Interface}
  /// {@category winrt}
  class IFileOpenPicker extends IInspectable {
    final Allocator allocator;
  
    // vtable begins at 6, is 11 entries long.
    IFileOpenPicker(Pointer<COMObject> ptr, {this.allocator = calloc})
        : super(ptr);
  
    int get ViewMode {
      final retValuePtr = calloc<Int32>();
  