anchor.diff:  
     var actual10 = c1
         ?.. m1()?.m()                   /// static type warning
  -      .. m2()?.m();                   /// static type warning
  +      .. m2()?.m();
     Expect.equals(expected, actual10);
     Expect.equals(2, c1.m2().counter);
     Expect.equals(6, c1.counter1);
  
positive.code: 
    var actual4 = c1
        ?.. m1()?.m()                   /// static type warning
        .. m2()?.m();                   /// static type warning
    Expect.equals(expected, actual4);
    Expect.equals(2, c1.m2().counter);
  
  
negative.code: 
    var actual6 = c2
      ?.. m1()?.m()
      .. m2()?.m();
    Expect.isNull(actual6);
  
    c2 = new C();
  