[Bug c++/104242] New: Class with constructor from std::any is not copyable

[Bug c++/104242] New: Class with constructor from std::any is not copyable

[fchelnokov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

            Bug ID: 104242
           Summary: Class with constructor from std::any is not copyable
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

The following code
```
#include <any>
#include <type_traits>

struct A {
    A(const A&) = default;
    explicit A(std::any value);
};
static_assert(std::is_copy_constructible_v<A>);
```
is accepted by GCC 11, but rejected by GCC trunk. Demo:
https://gcc.godbolt.org/z/sWTbhqE6c

[Bug c++/104242] Class with constructor from std::any is not copyable

[fchelnokov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

--- Comment #1 from Fedor Chelnokov <fchelnokov at gmail dot com> ---
The error message is
invalid use of incomplete type 'std::__conditional_t<true,
std::is_copy_constructible<A>, std::__not_<std::integral_constant<bool, false>
> >' {aka 'struct std::is_copy_constructible<A>'}
...

[Bug c++/104242] [12 Regression] Class with constructor from std::any is not copyable

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
            Summary|Class with constructor from |[12 Regression] Class with
                   |std::any is not copyable    |constructor from std::any
                   |                            |is not copyable
   Target Milestone|---                         |12.0

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note Clang's error message might be more helpfull:
In file included from <source>:2:
In file included from
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/any:39:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:168:14:
error: base class has incomplete type
    : public __conditional_t<_B1::value, _B2, _B1>
      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:2244:36:
note: in instantiation of template class
'std::__and_<std::__not_<std::integral_constant<bool, false>>,
std::is_copy_constructible<A>>' requested here
    using _Require = __enable_if_t<__and_<_Cond...>::value>;
                                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/any:188:19:
note: in instantiation of template type alias '_Require' requested here
              typename = _Require<__not_<__is_in_place_type<_VTp>>,
                         ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/any:190:7:
note: in instantiation of default argument for 'any<const A &, A,
std::any::_Manager_internal<A>>' required here
      any(_Tp&& __value)
      ^~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:971:54:
note: while substituting deduced template arguments into function template
'any' [with _Tp = const A &, _VTp = (no value), _Mgr = (no value), $3 = (no
value)]
    : public __bool_constant<__is_constructible(_Tp, _Args...)>
                                                     ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:1003:14:
note: in instantiation of template class 'std::__is_constructible_impl<A, const
A &>' requested here
    : public __is_constructible_impl<_Tp, const _Tp&>
             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:1010:14:
note: in instantiation of template class 'std::__is_copy_constructible_impl<A,
true>' requested here
    : public __is_copy_constructible_impl<_Tp>
             ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:3205:5:
note: in instantiation of template class 'std::is_copy_constructible<A>'
requested here
    is_copy_constructible<_Tp>::value;
    ^
<source>:9:20: note: in instantiation of variable template specialization
'std::is_copy_constructible_v<A>' requested here
static_assert(std::is_copy_constructible_v<A>);
                   ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.1/../../../../include/c++/12.0.1/type_traits:1009:12:
note: definition of 'std::is_copy_constructible<A>' is not complete until the
closing '}'
    struct is_copy_constructible
           ^

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-01-26
             Status|UNCONFIRMED                 |NEW

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Most likely caused by r12-4190.

Confirmed.

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:7a42b1fa1a090ead96cc0f94a8060a9650c810d5

commit r12-7708-g7a42b1fa1a090ead96cc0f94a8060a9650c810d5
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Mar 18 13:10:01 2022 +0000

    libstdc++: Simplify constraints for std::any construction [PR104242]

    Partially revert r12-4190-g6da36b7d0e43b6f9281c65c19a025d4888a25b2d
    because using __and_<..., is_copy_constructible<T>> when T is incomplete
    results in an error about deriving from is_copy_constructible<T> when
    that is incomplete. I don't know how to fix that, so this simply
    restores the previous constraint which worked in this case (even though
    I think it's technically undefined to use is_copy_constructible<T> with
    incomplete T). This doesn't restore exactly what we had before, but uses
    the is_copy_constructible_v and __is_in_place_type_v variable templates
    instead of the ::value member.

    libstdc++-v3/ChangeLog:

            PR libstdc++/104242
            * include/std/any (any(T&&)): Revert change to constraints.
            * testsuite/20_util/any/cons/104242.cc: New test.

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed

[Bug libstdc++/104242] [12 Regression] Class with constructor from std::any is not copyable

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104242

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:5fc6b3a03355e1f77a7c38c0fa7afb0822ad954f

commit r11-10870-g5fc6b3a03355e1f77a7c38c0fa7afb0822ad954f
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Mar 18 13:10:01 2022 +0000

    libstdc++: Simplify constraints for std::any construction [PR104242]

    Partially revert r12-4190-g6da36b7d0e43b6f9281c65c19a025d4888a25b2d
    because using __and_<..., is_copy_constructible<T>> when T is incomplete
    results in an error about deriving from is_copy_constructible<T> when
    that is incomplete. I don't know how to fix that, so this simply
    restores the previous constraint which worked in this case (even though
    I think it's technically undefined to use is_copy_constructible<T> with
    incomplete T). This doesn't restore exactly what we had before, but uses
    the is_copy_constructible_v and __is_in_place_type_v variable templates
    instead of the ::value member.

    libstdc++-v3/ChangeLog:

            PR libstdc++/104242
            * include/std/any (any(T&&)): Revert change to constraints.
            * testsuite/20_util/any/cons/104242.cc: New test.

    (cherry picked from commit 7a42b1fa1a090ead96cc0f94a8060a9650c810d5)