https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110195
--- Comment #5 from jack <jack.cui2 at foxmail dot com> ---
(In reply to Andrew Pinski from comment #4)
> Note clang accepts Single{} where Single is an empty class also before C++20
> ...
I think Clang accepting empty class case does not neccessarily mean it is
correct.
Because this one defeat the purpose of the uniform initialization and probably
a surprise that use can create it even if it is private.
