anchor.diff:    Expect.equals(s1, s2, '\n  $name.$name1: "$s1"\n  $name.$name2: "$s2"\n');
   }
   
  -void check(String name, f1, f2, [f3, f4, f5, f6]) {
  +void check(String name, f1, f2, [f3, f4, f5, f6, f7]) {
     check2(name, 'f1', f1, 'f2', f2);
     if (f3 != null) check2(name, 'f1', f1, 'f3', f3);
     if (f4 != null) check2(name, 'f1', f1, 'f4', f4);
     if (f5 != null) check2(name, 'f1', f1, 'f5', f5);
     if (f6 != null) check2(name, 'f1', f1, 'f6', f6);
  +  if (f7 != null) check2(name, 'f1', f1, 'f7', f7);
   }
   
   class IntPlusNull {
  
positive.code:     return a + null;
    }
  
    static test() {
      check('IntPlusNull', f1, f2, f3, f4, f5, f6);
    }
  }
  
  
negative.code:     return a + null;
    }
  
    static f7() {
      return 'a' + null;
    }
  
    static test() {
      check('StringPlusNull', f1, f2, f3, f4, f5, f6, f7);
    }
  }
  
  