是否可以分配或复制具有 const 成员的类

问：

根据 abseil.io/tips/177 的说法，它说

具体来说，如果您的类具有 const 成员，则无法将其分配给（无论是通过复制分配还是移动分配）。该语言可以理解这一点：如果您的类型具有 const 成员，则不会合成 copy-assignment 和 move-assignment 运算符。

我创建了一个简短的片段，我看到对象可以复制/移动。我怎么能理解 abseil.io/tips/177 的那句话？

#include <iostream>
class Stitch {
 public:
  Stitch(int in):num(in) { std::cout << "c'tor, address:" << this << std::endl; }
  ~Stitch() { std::cout << "d'tor, address:" << this << std::endl; }
  const int num;
  const std::size_t kAddr = (int)(this);
};
int main() {
  Stitch s1(1);
  std::cout << "s1 address: " << &s1 << " " << s1.num << std::endl;
  Stitch s2 = s1;
  std::cout << "s2 address: " << &s2 << " " << s2.num <<  std::endl;
  Stitch s3 = std::move(s1);
  std::cout << "s3 address: " << &s3 << " " << s3.num <<  std::endl;
  Stitch s4 = Stitch(4);
  std::cout << "s4 address: " << &s4 << " " << s4.num <<  std::endl;
}