|  | mixin Diagnosticable { | 
|  | void debugFillProperties(DiagnosticPropertiesBuilder properties) {} | 
|  | } | 
|  |  | 
|  | class DiagnosticPropertiesBuilder {} | 
|  |  | 
|  | abstract class PointerEvent with Diagnosticable {} | 
|  |  | 
|  | abstract class PointerSignalEvent extends PointerEvent {} | 
|  |  | 
|  | mixin _PointerEventDescription on PointerEvent { | 
|  | @override | 
|  | void debugFillProperties(DiagnosticPropertiesBuilder properties) {} | 
|  | } | 
|  |  | 
|  | mixin _CopyPointerScrollEvent on PointerEvent {} | 
|  |  | 
|  | class PointerScrollEvent extends PointerSignalEvent | 
|  | with _PointerEventDescription, _CopyPointerScrollEvent { | 
|  | @override | 
|  | void debugFillProperties(DiagnosticPropertiesBuilder properties) {} | 
|  | } | 
|  |  | 
|  | main() {} |