anchor.diff:  
     void _unhandledSend();
   }
  +
   /// Builder for initializer expressions. These expressions exclude any nested
   /// expression that is not needed to infer strong mode types.
   class InitializerBuilder extends ExpressionListener {
  
positive.code:             : ReferenceKind.topLevelFunction,
          typeVariables?.length ?? 0 /* todo */);
    }
    void endTypeArguments(int count, Token beginToken, Token endToken) {
      debugEvent("TypeArguments");
      push(popList(count) ?? const []);
  
negative.code:       // _endFields(count, s.currentEnum.values, false);
      }
    }
  
    void endFormalParameter(
        Token covariantKeyword, Token thisKeyword, FormalParameterType kind) {
      debugEvent("FormalParameter");
  