https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120611
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Clang exposes __invoke but it is private:
<source>:2:35: error: '__invoke' is a private member of '(lambda at
<source>:2:18)'
2 | return decltype([]{return 42;})::__invoke();
| ^
<source>:2:18: note: implicitly declared private here
2 | return decltype([]{return 42;})::__invoke();
| ^
Both are implementation namespaces but both are exposed (though clang makes
their static function private).
I am not sure there is anything to fix here.