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From: "hewillk at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/102163] New: std::variant rejects valid constant expression
Date: Wed, 01 Sep 2021 16:57:18 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102163

            Bug ID: 102163
           Summary: std::variant rejects valid constant expression
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

#include <variant>

struct O {
  O() =3D default;
  O(O&&) =3D default;
  O(const O&) =3D default;
  O& operator=3D(const O&) =3D default;
  O& operator=3D(O&&) =3D default;
  ~O() =3D default;

  constexpr O(int x) {}
};

constexpr std::variant<float, O> v{42};

https://godbolt.org/z/PdEx4z7rf

GCC-trunk rejected it under -std=3Dc++20, it seems to be a language feature=
 bug.=