From 61656a5a1b213b919c7361e804c56e83cb3b1985 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Thu, 2 Jan 2020 12:31:03 +0100
Subject: impl: fix subtractable traits

---
 include/newtype/impl/type_traits_extensions.hpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/include/newtype/impl/type_traits_extensions.hpp b/include/newtype/impl/type_traits_extensions.hpp
index 56824e2..d3e6d8b 100644
--- a/include/newtype/impl/type_traits_extensions.hpp
+++ b/include/newtype/impl/type_traits_extensions.hpp
@@ -595,7 +595,7 @@ namespace nt::impl
      * @note This specialization forms the case for subtractable T
      */
     template<typename T>
-    struct is_subtractable<T, std::void_t<decltype(std::declval<T const &>() + std::declval<T const &>())>> : std::true_type
+    struct is_subtractable<T, std::void_t<decltype(std::declval<T const &>() - std::declval<T const &>())>> : std::true_type
     {
     };
 
@@ -625,8 +625,8 @@ namespace nt::impl
      * @note This specialization forms the case for subtractable T detemining if T is noexcept subtractable
      */
     template<typename T>
-    struct is_nothrow_subtractable<T, std::void_t<decltype(std::declval<T const &>() + std::declval<T const &>())>>
-        : std::bool_constant<noexcept(std::declval<T const &>() + std::declval<T const &>())>
+    struct is_nothrow_subtractable<T, std::void_t<decltype(std::declval<T const &>() - std::declval<T const &>())>>
+        : std::bool_constant<noexcept(std::declval<T const &>() - std::declval<T const &>())>
     {
     };
 
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