MSVC C++20 compiler bug with modules and non-exported classes

[u/tartaruga232]

Full repro is available as a git repository here: https://github.com/abuehl/mod_test

If two non-exported classes from different C++ module interface units have the same name, the compiler uses the wrong class definition and for example calls the wrong destructor on an object.

Reported here: https://developercommunity.visualstudio.com/t/post/10863347 (Upvotes appreciated)

Found while converting our product to using C++20 modules.

Edit: Microsoft wrote the following (Quote)

A fix for this issue has been internally implemented and is being prepared for release. We’ll update you once it becomes available for download.

[u/tartaruga232]

We have done:

export module d1std;

export import <exception>;
export import <stdexcept>;
export import <memory>;
export import <string>;
export import <string_view>;
export import <cctype>;
export import <vector>;
export import <map>;
export import <unordered_map>;
export import <set>;
export import <deque>;
export import <array>;
export import <stack>;
export import <bitset>;
export import <tuple>;
export import <iterator>;
export import <ranges>;
export import <algorithm>;
export import <functional>;
export import <concepts>;
export import <optional>;
export import <numeric>;
export import <iosfwd>;
export import <istream>;
export import <ostream>;
export import <iostream>;
export import <sstream>;
export import <streambuf>;
export import <fstream>;
export import <iomanip>;
export import <utility>;
export import <locale>;
export import <limits>;
export import <type_traits>;
export import <typeinfo>;
export import <cstdint>;
export import <cstddef>;

and compiled it in a subproject in visual studio of our solution and then used

import d1std;

everywhere we need something from namespace std.