anchor.diff:  
         ClassElement superclass = cls.superclass;
         if (superclass != null) {
  -        jsAst.Node superAccess = emitter.classAccess(superclass);
  +        jsAst.Node superAccess = emitter.constructorAccess(superclass);
           inherits.add(
               js.statement(
                   r'#.inheritFrom(#, #)', [helper, classAccess, superAccess]));
  
positive.code:       ClassElement superclass = cls.superclass;
        jsAst.Node superAccess =
            superclass == null ? js('null')
                : emitter.classAccess(superclass);
        jsAst.Node classAccess = emitter.classAccess(cls);
        updates.add(
            js.statement(
                r'# = #.schemaChange(#, #, #)',
  
negative.code:     }
  
      updates.add(
          js.statement('delete #.prototype.#', [prototypeAccess, getterName]));
      updates.add(
          js.statement('delete #.prototype.#', [prototypeAccess, setterName]));
    }
  }
  
  