src/vs/workbench/services/search/common/search.ts/isSerializedSearchComplete
export function isSerializedSearchComplete(arg: ISerializedSearchProgressItem | ISerializedSearchComplete): arg is ISerializedSearchComplete {
	if ((arg as any).type === 'error') {
		return true;
	} else if ((arg as any).type === 'success') {
		return true;
	} else {
		return false;
	}
}