无法访问派生类中的基本受保护成员！(在虚函数中）

我有一个抽象类，例如A(几个纯虚函数(。我是公共继承 A 类的 B 类。在提供虚函数的定义时，我正在尝试访问 A 类的私有成员(例如 Ptr (。但是，编译器无法找到类 A 的所有受保护成员的声明。 这里出了什么问题？

        //
        // LinkedListType.h
        //
        #ifndef LINKEDLISTTYPE_LINKEDLISTTYPE_H
        #define LINKEDLISTTYPE_LINKEDLISTTYPE_H
        #include <iostream>
        using namespace std;
        template <class Type>
        struct nodeType
        {
            int val;
            nodeType<Type> *link;
        };
        template <class Type>
        class LinkedListType{
        public:
            virtual void insertFirst(Type& node)=0;
            LinkedListType();
            ~LinkedListType();
            void destroyList();
        protected:
            int count;
            nodeType<Type> *first;
            nodeType<Type> *last;
        };
        #endif //LINKEDLISTTYPE_LINKEDLISTTYPE_H

        //
        // LinkedListType.cpp
        //
        #include <iostream>
        #include "LinkedListType.h"
        using namespace std;
        template <class Type>
        void LinkedListType<Type>::destroyList() {
            if (firstElem == NULL)cout<<"LinkedList is empty"<<endl;
            nodeType<Type> *tmp;
            while(tmp != NULL){
                tmp=first;
                first=first->link;
                delete tmp;
            }
            last=NULL;
            count =0;
        }

        template <class Type>
        LinkedListType<Type>::LinkedListType() {
            first=NULL;
            last=NULL;
            count=0;
        }

        template <class Type>
        LinkedListType<Type>::~LinkedListType() {
            destroyList();
        }


//
        // unorderedLinkedList.cpp
        //
        #ifndef UNORDEREDLINKEDLIST_UNORDEREDLINKEDLIST_H
        #define UNORDEREDLINKEDLIST_UNORDEREDLINKEDLIST_H
        #include <iostream>
        #include "LinkedListType.h"
        using namespace std;
        template <class Type>
        class unorderedLinkedList: public LinkedListType<Type>{
        public:
            void insertFirst(Type& node);
        };
        #endif //UNORDEREDLINKEDLIST_UNORDEREDLINKEDLIST_H

        //
        // unorderedLinkedList.h
        //
        #include <iostream>
        #include "unorderedLinkedList.h"
        using  namespace std;
        template <class Type>
        void unorderedLinkedList<Type>::insertFirst(Type& node) {
            nodeType<Type> *newNode= new nodeType<Type>;
            if(newNode == NULL)
                assert("Unable to allocate node to insert");
            newNode->val=node;
            newNode->link=first;  /* ---> ERROR error: use of undeclared 
                               identifier 'first'; did you mean 
                               'std::_PairT::first'? */
            first=newNode; /* ---> ERROR error: use of undeclared 
                                identifier 'first'; did you mean 
                               'std::_PairT::first'? */
            count++;
        }

        //
        // CMakeList.txt
        //
        cmake_minimum_required(VERSION 3.13)
        project(UnorderedLinkedList)
        set(CMAKE_CXX_STANDARD 14)
        add_executable(UnorderedLinkedList main.cpp LinkedListType.h LinkedListType.cpp unorderedLinkedList.h unorderedLinkedList.cpp)

        //Main program
        #include <iostream>
        #include "unorderedLinkedList.h"
        #include "unorderedLinkedList.cpp"
        using namespace std;
        int main() {
            std::cout << "Hello, World!" << std::endl;
            unorderedLinkedList<int> u1;
            u1.insertFirst(10);
            return 0;
        }