vs_2022_tuple_ref_bug

vs_2022_tuple_ref_bug.cpp

// demonstration of a bug in VS2022 / MSVC 19.38.32919
//
// repro steps:
// 1. make a C++17 or later project in VS2022
// 2. add the single-header library "soagen.hpp" to it from here:
//    https://raw.githubusercontent.com/marzer/soagen/ace22525eeff90d0ff9228b78d0045db87c24099/src/soagen/hpp/single/soagen.hpp
// 3. add this code file to it
// 4. compile + run
// 5. observe that line 53 below (ends with "#### BUG") evaluates to the wrong result
// 6. inspect the values in the debugger will show the references are corrupted

#include <utility>
#include <string>
#include <tuple>
#include <iostream>
#include "soagen.hpp"

using employees = soagen::table<soagen::table_traits<unsigned long long /* id */,
													 const std::string /* name */,
													 std::tuple<int, int, int> /* dob */,
													 unsigned long /* salary */>>;

template <typename Employee>
static void print_employee(const Employee& emp)
{
	std::cout << "{ "							   //
			  << emp.get<0>() << ", "			   //
			  << emp.get<1>() << ", "			   //
			  << "{ "							   //
			  << std::get<0>(emp.get<2>()) << ", " //
			  << std::get<1>(emp.get<2>()) << ", " //
			  << std::get<2>(emp.get<2>())		   //
			  << " }, "							   //
			  << emp.get<3>()					   //
			  << " }\n";
}

int main()
{
	std::cout << std::boolalpha;

	employees e;
	e.emplace_back(0, "mark gillard", std::tuple{ 16, 3, 1987 }, 50000);
	e.emplace_back(1, "joe bloggs", std::tuple{ 10, 4, 1980 }, 60000);
	e.emplace_back(2, "jane doe", std::tuple{ 6, 5, 1970 }, 70000);

	print_employee(e[0]);
	print_employee(std::as_const(e)[1]);
	print_employee(std::move(e)[2]);

	std::cout << (e[1] == e[1]) << "\n";
	std::cout << (e[1] == std::as_const(e)[1]) << "\n";
	std::cout << (e[1] == std::move(e)[1]) << "\n"; // #### BUG: 'false' but should be 'true'
	std::cout << (e[1] == std::move(std::as_const(e))[1]) << "\n";
}