anchor.diff:        nullQuestion,
         typeParameterTypeNone(T),
         strT0: 'Null?',
  -      strT1: 'T',
  +      strT1: 'T, T extends Object',
       );
     }
   
  
positive.code:     isSubtype(
        typeParameterTypeStar(T),
        typeParameterTypeStar(T),
        strT0: 'T*',
        strT1: 'T*',
      );
    }
  
  
negative.code:     isNotSubtype(
        typeParameterTypeNone(T),
        objectNone,
        strT0: 'T, T extends num?',
        strT1: 'Object',
      );
    }
  