From fb3ce863ff3679390efb5667499097d5edb45fb2 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Mon, 8 Mar 2021 03:26:40 +0200
Subject: [PATCH] Add MSVC workaround for monospace constexpr (refs #25)

---
 include/boost/variant2/variant.hpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/boost/variant2/variant.hpp b/include/boost/variant2/variant.hpp
index f46fdb4..06a0419 100644
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -81,6 +81,8 @@ struct monostate
 {
 };
 
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1940)
+
 constexpr bool operator<(monostate, monostate) noexcept { return false; }
 constexpr bool operator>(monostate, monostate) noexcept { return false; }
 constexpr bool operator<=(monostate, monostate) noexcept { return true; }
@@ -88,6 +90,17 @@ constexpr bool operator>=(monostate, monostate) noexcept { return true; }
 constexpr bool operator==(monostate, monostate) noexcept { return true; }
 constexpr bool operator!=(monostate, monostate) noexcept { return false; }
 
+#else
+
+constexpr bool operator<(monostate const&, monostate const&) noexcept { return false; }
+constexpr bool operator>(monostate const&, monostate const&) noexcept { return false; }
+constexpr bool operator<=(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator>=(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator==(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator!=(monostate const&, monostate const&) noexcept { return false; }
+
+#endif
+
 // variant forward declaration
 
 template<class... T> class variant;