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

[Jonathan Wakely via Gcc-patches]

libstdc++-v3/ChangeLog:

        * include/bits/utility.h (__is_in_place_type_v): Define
        variable template to detect in_place_type_t specializations.
        (__is_in_place_type): Replace class template with alias
        template using __is_in_place_type_v.
        * include/std/any (any(T&&)): Check __is_in_place_type first and
        avoid instantiating is_copy_constructible unnecessarily.

Tested powerpc64le-linux. Committed to trunk.


commit 6da36b7d0e43b6f9281c65c19a025d4888a25b2d
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Mon Oct 4 23:14:30 2021

    libstdc++: Simplify constraints for std::any construction
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/utility.h (__is_in_place_type_v): Define
            variable template to detect in_place_type_t specializations.
            (__is_in_place_type): Replace class template with alias
            template using __is_in_place_type_v.
            * include/std/any (any(T&&)): Check __is_in_place_type first and
            avoid instantiating is_copy_constructible unnecessarily.

diff --git a/libstdc++-v3/include/bits/utility.h 
b/libstdc++-v3/include/bits/utility.h
index 96d350874d9..fce52a4530d 100644
--- a/libstdc++-v3/include/bits/utility.h
+++ b/libstdc++-v3/include/bits/utility.h
@@ -184,17 +184,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline constexpr in_place_index_t<_Idx> in_place_index{};
 
   template<typename>
-    struct __is_in_place_type_impl : false_type
-    { };
+    inline constexpr bool __is_in_place_type_v = false;
 
   template<typename _Tp>
-    struct __is_in_place_type_impl<in_place_type_t<_Tp>> : true_type
-    { };
+    inline constexpr bool __is_in_place_type_v<in_place_type_t<_Tp>> = true;
 
   template<typename _Tp>
-    struct __is_in_place_type
-      : public __is_in_place_type_impl<_Tp>
-    { };
+    using __is_in_place_type = bool_constant<__is_in_place_type_v<_Tp>>;
+
 #endif // C++17
 #endif // C++14
 
diff --git a/libstdc++-v3/include/std/any b/libstdc++-v3/include/std/any
index 625cac619f0..e3d9d774de4 100644
--- a/libstdc++-v3/include/std/any
+++ b/libstdc++-v3/include/std/any
@@ -183,8 +183,8 @@ _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>,
-             enable_if_t<is_copy_constructible<_VTp>::value
-                         && !__is_in_place_type<_VTp>::value, bool> = true>
+             typename = _Require<__not_<__is_in_place_type<_VTp>>,
+                                 is_copy_constructible<_VTp>>>
       any(_Tp&& __value)
       : _M_manager(&_Mgr::_S_manage)
       {