When an override is not called because of move construction.

no-override.cpp

#include <iostream>
#include <stdexcept>
#include <utility>

struct Base {
  virtual const char *test() const { return "Base!"; }

  Base() = default;

  Base(const Base& other) noexcept {
    std::cout << "Copy CTOR" << std::endl;
  }

  Base(Base&& other) noexcept {
    std::cout << "Move CTOR" << std::endl;
  }

  Base operator=(Base&& other) noexcept {
    std::cout << "Move assigment." << std::endl;
    return *this;
  }

  Base& operator=(const Base& other) noexcept {
    std::cout << "Copy assigment." << std::endl;
    return *this;
  }
};

struct Deriv : Base {
  const char *test() const override { return "Deriv!"; }
};

int main() {
  Deriv d1 = Deriv{}; // d1.test() calls Deriv's override.
  Base& b = d1;       // b.test() calls Deriv's override.
  Base b1 = Deriv{};  // b.test() calls Base implementation... is a MOVE constructor!

  std::cout << d1.test() << std::endl;
  std::cout << b.test() << std::endl;
  std::cout << b1.test() << std::endl;

  return 0;
}