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libstdc++: Simplify constraints for std::any construction

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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.
This commit is contained in:
Jonathan Wakely 2021-10-04 23:14:30 +01:00
parent 824e085573
commit 6da36b7d0e
2 changed files with 6 additions and 9 deletions
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11
libstdc++-v3/include/bits/utility.h
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@ -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

4
libstdc++-v3/include/std/any
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@ -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)
{