https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120025
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So the big problem with this extension is that it will not work with concepts
(and SFINAE) in a decent form. This is why the extension was removed in the
first place.
An example is:
```
template <class T>
T f();
template <class T>
concept allows = requires(T x) { f<T>().t = 0; };
struct s
{
int t;
};
static_assert(allows<s>);
```
Right now GCC does the correct thing even for -fpermissive.
