From 802f1e1eec328f2810a796f1ee06beb3312768c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Me=C3=9Fmer?=
 <smessmer@users.noreply.github.com>
Date: Tue, 18 Dec 2018 13:41:47 -0800
Subject: [PATCH] Fix void_t for older compilers

---
 flat_hash_map.hpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/flat_hash_map.hpp b/flat_hash_map.hpp
index a8723ee..47ab30e 100644
--- a/flat_hash_map.hpp
+++ b/flat_hash_map.hpp
@@ -263,7 +263,10 @@ inline size_t next_power_of_two(size_t i)
     return i;
 }
 
-template<typename...> using void_t = void;
+// Implementation taken from http://en.cppreference.com/w/cpp/types/void_t
+// (it takes CWG1558 into account and also works for older compilers)
+template<typename... Ts> struct make_void { typedef void type;};
+template<typename... Ts> using void_t = typename make_void<Ts...>::type;
 
 template<typename T, typename = void>
 struct HashPolicySelector