[gcc r11-10870] libstdc++: Simplify constraints for std::any construction [PR104242]

[gcc r11-10870] libstdc++: Simplify constraints for std::any construction [PR104242]

[Jonathan Wakely]

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)

Diff:
---
 libstdc++-v3/include/std/any                      |  4 ++--
 libstdc++-v3/testsuite/20_util/any/cons/104242.cc | 12 ++++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/std/any b/libstdc++-v3/include/std/any
index d96ea06c1ae..5aec4040064 100644
--- a/libstdc++-v3/include/std/any
+++ b/libstdc++-v3/include/std/any
@@ -184,8 +184,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     /// Construct with a copy of @p __value as the contained object.
     template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>,
 	      typename _Mgr = _Manager<_VTp>,
-	      typename = _Require<__not_<__is_in_place_type<_VTp>>,
-				  is_copy_constructible<_VTp>>>
+	      enable_if_t<is_copy_constructible_v<_VTp>
+			  && !__is_in_place_type_v<_VTp>, bool> = true>
       any(_Tp&& __value)
       : _M_manager(&_Mgr::_S_manage)
       {
diff --git a/libstdc++-v3/testsuite/20_util/any/cons/104242.cc b/libstdc++-v3/testsuite/20_util/any/cons/104242.cc
new file mode 100644
index 00000000000..8d5868b7ff9
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/any/cons/104242.cc
@@ -0,0 +1,12 @@
+// { dg-do compile { target c++17 } }
+
+// PR libstdc++/104242 - Class with constructor from std::any is not copyable
+
+#include <any>
+#include <type_traits>
+
+struct A {
+    A(const A&) = default;
+    explicit A(std::any value);
+};
+static_assert(std::is_copy_constructible_v<A>);