From 3f3b2128ec1b0e5a7c6b72234e57ec052a6ff71c Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Thu, 21 Sep 2023 11:07:14 -0700
Subject: [PATCH] Update `extract()` SFINAE to be friendly to msvc-14.0

msvc-14.0 seems to require the parameter pack be explicitly mentioned though no other compilers seem to have this issue
---
 include/boost/unordered/detail/implementation.hpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/boost/unordered/detail/implementation.hpp b/include/boost/unordered/detail/implementation.hpp
index f3629a2b..d2c46e10 100644
--- a/include/boost/unordered/detail/implementation.hpp
+++ b/include/boost/unordered/detail/implementation.hpp
@@ -2878,11 +2878,13 @@ namespace boost {
           return no_key();
         }
 
-        template <template <class...> class Tuple, typename T, typename T2,
+        template <template <typename...> class Tuple, typename T, typename T2,
+          typename... Args>
+        static auto extract(
+          std::piecewise_construct_t, Tuple<T, Args...> const& k, T2 const&) ->
           typename std::enable_if<
-            !std::is_same<T, boost::tuples::null_type>::value, int>::type = 0>
-        static typename is_key<key_type, T>::type extract(
-          std::piecewise_construct_t, Tuple<T> const& k, T2 const&)
+            !std::is_same<T, boost::tuples::null_type>::value,
+            typename is_key<key_type, T>::type>::type
         {
           using std::get;
           return typename is_key<key_type, T>::type(get<0>(k));