On Tue, May 23, 2023, 20:22 许传奇(夜灯) via SG15 <sg15@lists.isocpp.org> wrote:
Now we can't assume `user.cpp` isn't the same with `user.orig.cpp`. It is surprising since such patterns are
pretty common in practice. And I'm worrying that we'll meet problems if this is true.

It's actually worse than that. Since the compiler is free to replace `#include` by the equivalent `import` the semantic change can happen even without any source change in the code.

If someone declare the header to be importable, the semantics change silently.

As I said before, so far, early experiences simply put the burden on the user not to choose headers where this would be a problem.