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From: "de34 at live dot cn" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/113060] std::variant converting
 constructor/assignment is non-conforming after P2280?
Date: Mon, 19 Feb 2024 09:07:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113060

--- Comment #5 from Jiang An <de34 at live dot cn> ---
Function pointers seem working (https://gcc.godbolt.org/z/Mbvfafdof).

```
template<class Ti, class Tp, class =3D void>
constexpr bool is_array_element_initializable_from =3D false;
template<class Ti, class Tp>
constexpr bool is_array_element_initializable_from<Ti, Tp,
    decltype(std::declval<auto (*)(Tp&& t)
        -> decltype((void)
array_element_initialization_tester<Ti>{{std::forward<Tp>(t)}})>()
    (std::declval<Tp>()))> =3D true;
```

So perhaps we can simply change `decltype(_Arr<_Ti>{{std::declval<_Tp>()}})=
` to
`decltype(std::declval<auto (*)(_Tp&& __t) ->
decltype(_Arr<_Ti>{{std::forward<_Tp>(__t)}})>(std::declval<_Tp>()))` to
resolve this "bug".=