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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++/100667] [11/12/13/14 Regression] std::tuple<A&&>
 cannot be constructed from A&&, if A not defined (only forward declared)
Date: Wed, 27 Mar 2024 12:59:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100667

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Piotr Nycz from comment #0)
> It looks that std library code start requiring this to pass:
> std::is_nothrow_constructible<A&&, A>...

Indeed, that's what the standard requires (Clang and MSVC reject this the s=
ame
way). The standard also says that using traits like is_constructible requir=
es
complete types.

However, that's clearly silly for is_constructible<A&&, A> because we know =
that
reference binding is valid for any A whether it's complete or not.

This is the subject of:
https://cplusplus.github.io/LWG/issue2939=