From 4f23017594734e9792bbcf205e1c61a2f32aa7c8 Mon Sep 17 00:00:00 2001
From: q66 <daniel@octaforge.org>
Date: Wed, 5 Aug 2015 20:05:03 +0100
Subject: [PATCH] keyset: allow get_key to return by value (still use reference
 where possible)

---
 ostd/keyset.hh | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/ostd/keyset.hh b/ostd/keyset.hh
index 6108f1d..0905efb 100644
--- a/ostd/keyset.hh
+++ b/ostd/keyset.hh
@@ -19,11 +19,17 @@ namespace ostd {
 
 namespace detail {
     template<typename T>
-    using KeysetKey = const Decay<decltype(declval<const T &>().get_key())>;
+    using KeysetKeyRet = decltype(declval<const T &>().get_key());
+    template<typename T>
+    using KeysetKey = const Decay<KeysetKeyRet<T>>;
 
     template<typename T, typename A> struct KeysetBase {
         using Key = KeysetKey<T>;
-        static inline const Key &get_key(const T &e) {
+
+        using RetKey = Conditional<
+            IsReference<KeysetKeyRet<T>>::value, Key &, Key
+        >;
+        static inline RetKey get_key(const T &e) {
             return e.get_key();
         }
         static inline T &get_data(T &e) {