[Bug libstdc++/117686] [15 Regression] error in unordered_set::emplace

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117686

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is the fix:

--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -2287,7 +2287,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        else if constexpr (sizeof...(_Args) == 2)
          {
            pair<const _Args&...> __refs(__args...);
-           if constexpr (__is_key_type<pair<_Args...>>)
+           if constexpr (__is_key_type<pair<const _Args&...>>)
              {
                const auto& __key = _ExtractKey{}(__refs);
                __kp = std::__addressof(__key);