#include <memory>

class A : public std::enable_shared_from_this<A> {
public:
    int id;
    A(int x) : id(x) {}
};

class B : public A
{
public:
    B() : id(1000);
};


int main() {
  A a(100);
  a.shared_from_this();
  B b;
  std::shared_ptr<B> bad = b.shared_from_this();
}

//
// /home/nomaddo/CLionProjects/test/main.cpp: In function ‘int main()’:
// /home/nomaddo/CLionProjects/test/main.cpp:20:29: error: conversion from ‘std::shared_ptr<A>’ to non-scalar type ‘B’ requested
//  B bad = b.shared_from_this();
//  ^