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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/109242] C++2b std::optional::transform omits required
 std::remove_cv_t from return optional type
Date: Wed, 29 Mar 2023 21:26:00 +0000
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X-Bugzilla-Keywords: wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109242

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu=
.org
             Status|NEW                         |ASSIGNED

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Peter Kasting from comment #2)
> struct S {
>   int& i() const;
> };
>=20
> void foo() {
>   std::optional<S>().transform(&S::i);

The U type is a reference here, which isn't allowed.


This shows the bug:

struct A { };
const A f(int);
std::optional<int> o;
A&& p =3D *o.transform(f);=