From 70fca4483e0d48bc8cc45a72ba6d4276f2e9563b Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Tue, 31 Aug 2021 21:16:09 +0300
Subject: [PATCH] std::equal_to has no first_argument_type in C++20

---
 test/helpers/tracker.hpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/helpers/tracker.hpp b/test/helpers/tracker.hpp
index 0f86ba6f..bc3d4b47 100644
--- a/test/helpers/tracker.hpp
+++ b/test/helpers/tracker.hpp
@@ -30,6 +30,11 @@ namespace test {
     typedef test::less type;
   };
 
+  template<class T> struct equals_to_compare< std::equal_to<T> >
+  {
+    typedef std::less<T> type;
+  };
+
   template <class X1, class X2> void compare_range(X1 const& x1, X2 const& x2)
   {
     typedef test::list<typename X1::value_type> value_list;