From a544ada8fe998bc7c47be942008430a7ec8366da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Samuel=20Garc=C3=ADa=20Salas?= <samuel9@gmail.com>
Date: Sat, 17 Oct 2015 08:53:58 +0200
Subject: [PATCH] std::hash support for gsl::not_null.

---
 include/gsl.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/gsl.h b/include/gsl.h
index 519682b..ca37848 100644
--- a/include/gsl.h
+++ b/include/gsl.h
@@ -197,6 +197,19 @@ private:
 
 } // namespace gsl
 
+namespace std
+{
+    template<class T>
+    struct hash<gsl::not_null<T *>>
+    {
+        size_t operator()(const gsl::not_null<T *> & value) const
+        {
+            return hash<T *>{}(value);
+        }
+    };
+
+} // namespace std
+
 #ifdef _MSC_VER
 
 #undef constexpr