The components that used __type_identity in C++20 mode (due source
compatibility with other standard) lead to instantiation of separate
class template from std::type_identity for each used type. This
patch makes __type_identity an alias to type_identity if later is
available.
libstdc++-v3/ChangeLog:
* include/std/type_traits (__type_identity, __type_identity_t)
[__cpp_lib_type_identity]: Define as alias to type_identity
and it's nested type respectively.
---
Testing on x86_64-linux. Waiting for full test to finish.
OK for trunk when all tests passes.
libstdc++-v3/include/std/type_traits | 36 ++++++++++++++++++----------
1 file changed, 23 insertions(+), 13 deletions(-)
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index 1c03c22e8ee..667725b1b01 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -164,6 +164,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using __conditional_t
= typename __conditional<_Cond>::template type<_If, _Else>;
+#ifdef __cpp_lib_type_identity // C++ >= 20
+ /** * Identity metafunction.
+ * @since C++20
+ * @{
+ */
+ template<typename _Tp>
+ struct type_identity { using type = _Tp; };
+
+ template<typename _Tp>
+ using type_identity_t = typename type_identity<_Tp>::type;
+ /// @}
+
+ /// @cond undocumented
+ template <typename _Tp>
+ using __type_identity = type_identity<_Tp>;
+
+ template<typename _Tp>
+ using __type_identity_t = typename type_identity<_Tp>::type;
+ /// @endcond
+#else
/// @cond undocumented
template <typename _Type>
struct __type_identity
@@ -171,7 +191,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
using __type_identity_t = typename __type_identity<_Tp>::type;
+ /// @endcond
+#endif
+ /// @cond undocumented
namespace __detail
{
// A variadic alias template that resolves to its first argument.
@@ -3955,19 +3978,6 @@ template<typename _Ret, typename _Fn, typename... _Args>
/// @}
#endif // __cpp_lib_remove_cvref
-#ifdef __cpp_lib_type_identity // C++ >= 20
- /** * Identity metafunction.
- * @since C++20
- * @{
- */
- template<typename _Tp>
- struct type_identity { using type = _Tp; };
-
- template<typename _Tp>
- using type_identity_t = typename type_identity<_Tp>::type;
- /// @}
-#endif
-
#ifdef __cpp_lib_unwrap_ref // C++ >= 20
/** Unwrap a reference_wrapper
* @since C++20
--
2.54.0
