[gcc r16-3674] libstdc++: Rename template parameter of std::constant_wrapper

[Jonathan Wakely]

https://gcc.gnu.org/g:f65747d0d966bdee2cbe6053cf2347bedba8cf0d

commit r16-3674-gf65747d0d966bdee2cbe6053cf2347bedba8cf0d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Sep 9 00:34:21 2025 +0100

    libstdc++: Rename template parameter of std::constant_wrapper
    
    This fixes:
    FAIL: 17_intro/badnames.cc  -std=gnu++26 (test for excess errors)
    
    libstdc++-v3/ChangeLog:
    
            * include/std/type_traits (constant_wrapper): Rename template
            parameter to avoid BADNAME.

Diff:
---
 libstdc++-v3/include/std/type_traits | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 26cbbb4fd5ba..42a1e7f1732b 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -4648,12 +4648,12 @@ template<typename _Ret, typename _Fn, typename... _Args>
       }
   };
 
-  template<_CwFixedValue _X, typename>
+  template<_CwFixedValue _Xv, typename>
   struct constant_wrapper : _CwOperators
   {
-    static constexpr const auto& value = _X._M_data;
+    static constexpr const auto& value = _Xv._M_data;
     using type = constant_wrapper;
-    using value_type = typename decltype(_X)::_S_type;
+    using value_type = typename decltype(_Xv)::_S_type;
 
     template<_ConstExprParam _Right>
       constexpr auto