anchor.diff:    ///
     /// This method is useful for tests or test harnesses that want to assert the
     /// handler for the specified channel has not been altered by a previous test.
  -  bool checkMockMethodCallHandler(Future<dynamic> handler(MethodCall call)) => _methodChannelMockHandlers[this] == handler;
  +  bool checkMockMethodCallHandler(Future<dynamic> Function(MethodCall call)? handler) => _methodChannelMockHandlers[this] == handler;
   
     Future<ByteData?> _handleAsMethodCall(ByteData? message, Future<dynamic> handler(MethodCall call)) async {
       final MethodCall call = codec.decodeMethodCall(message);
  
positive.code:   ///
    /// The handler's return value is sent back to the platform plugins as a
    /// message reply. It may be null.
    void setMessageHandler(Future<T> handler(T message)) {
      if (handler == null) {
        binaryMessenger.setMessageHandler(name, null);
      } else {
  
negative.code:   ///
    /// This method is useful for tests or test harnesses that want to assert the
    /// handler for the specified channel has not been altered by a previous test.
    bool checkMethodCallHandler(Future<dynamic> Function(MethodCall call)? handler) => _methodChannelHandlers[this] == handler;
  
    /// Sets a mock callback for intercepting method invocations on this channel.
    ///
  