[Bug libstdc++/102894] New: make_any is not SFINAE-friendly

[Bug libstdc++/102894] New: make_any is not SFINAE-friendly

[de34 at live dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

            Bug ID: 102894
           Summary: make_any is not SFINAE-friendly
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: de34 at live dot cn
  Target Milestone: ---

std::make_any is specified in [any.nonmembers] p2-3 via "Effects: Equivalent
to: ...". According to [structure.specifications] p4, it propagates the
"Constraints:" of the constructor (in [any.cons] p11 and p17), and thus
SFINAE-friendly.

The following program should fail to compile. But currently it compiles with
libstdc++ due to lack of constraints. Note that std::make_optional is correctly
constrained in libstdc++.

Wandbox link:https://wandbox.org/permlink/noMWBjdCp0hg1pEZ

#include <type_traits>
#include <utility>
#include <any>

namespace test {
template<class T, class... Args>
auto test_make_any(int)
    -> decltype((void)std::make_any<T>(std::declval<Args>()...),
std::true_type{});
template<class, class...>
auto test_make_any(...) -> std::false_type;
template<class T, class... Args>
inline constexpr bool can_make_any = decltype(test_make_any<T,
Args...>(0))::value;
}

int main()
{
    static_assert(test::can_make_any<int, int, int>); // should not pass
}

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-10-22
             Status|UNCONFIRMED                 |ASSIGNED

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

--- Comment #1 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:0c1f737a485f05c591c94b50acfb416c45a4c916

commit r12-4634-g0c1f737a485f05c591c94b50acfb416c45a4c916
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Oct 22 22:55:00 2021 +0100

    libstdc++: Constrain std::make_any [PR102894]

    std::make_any should be constrained so it can only be called if the
    construction of the return value would be valid.

    libstdc++-v3/ChangeLog:

            PR libstdc++/102894
            * include/std/any (make_any): Add SFINAE constraint.
            * testsuite/20_util/any/102894.cc: New test.

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.4

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

--- Comment #2 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:88d481c9ee1e6a24dc11ab56d8688308e0211855

commit r11-9293-g88d481c9ee1e6a24dc11ab56d8688308e0211855
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Oct 22 22:55:00 2021 +0100

    libstdc++: Constrain std::make_any [PR102894]

    std::make_any should be constrained so it can only be called if the
    construction of the return value would be valid.

    libstdc++-v3/ChangeLog:

            PR libstdc++/102894
            * include/std/any (make_any): Add SFINAE constraint.
            * testsuite/20_util/any/102894.cc: New test.

    (cherry picked from commit 0c1f737a485f05c591c94b50acfb416c45a4c916)

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:923637b6cb70986e83ae0109ec4bcd26fdfe3624

commit r10-10308-g923637b6cb70986e83ae0109ec4bcd26fdfe3624
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Oct 22 22:55:00 2021 +0100

    libstdc++: Constrain std::make_any [PR102894]

    std::make_any should be constrained so it can only be called if the
    construction of the return value would be valid.

    libstdc++-v3/ChangeLog:

            PR libstdc++/102894
            * include/std/any (make_any): Add SFINAE constraint.
            * testsuite/20_util/any/102894.cc: New test.

    (cherry picked from commit 0c1f737a485f05c591c94b50acfb416c45a4c916)

[Bug libstdc++/102894] make_any is not SFINAE-friendly

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102894

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

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

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 11.3 and 10.4, thanks for the report.