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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109680] [13/14 Regression] is_convertible<int() const,
 int(*)()> incorrectly true
Date: Mon, 01 May 2023 16:32:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109680

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
template <typename T, typename U =3D T&&>
U __declval (int);
template <typename T>
T __declval (long);
template <typename T>
auto declval () noexcept -> decltype (__declval <T> (0));
using To =3D int () const;
using From =3D int (*) ();
To foo () { return declval <From> (); }
>From bar () { return declval <To> (); }
static_assert (!__is_convertible (To, From), "");
static_assert (!__is_convertible (From, To), "");
should show that both assertions should succeed.  Dunno if in this case the
reason why it isn't convertible is simply the fact that functions can't be
declared to return function/method/array types or some other reason as well=
.=