From 076085fd29f65f548ab1e4b45af249a30f178b2e Mon Sep 17 00:00:00 2001
From: Jeremiah Willcock <jewillco@osl.iu.edu>
Date: Fri, 14 Sep 2012 21:41:06 +0000
Subject: [PATCH] Using lazy_enable_if to avoid "reference to void" errors for
 properties that are not found; fixes #7378

[SVN r80528]
---
 include/boost/pending/property.hpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/boost/pending/property.hpp b/include/boost/pending/property.hpp
index f79e7448..0befc798 100644
--- a/include/boost/pending/property.hpp
+++ b/include/boost/pending/property.hpp
@@ -123,12 +123,14 @@ namespace boost {
     typedef lookup_one_property_internal<Base, PropName> base_type;
     public:
     template <typename PL>
-    static typename enable_if<is_same<PL, boost::property<Tag, T, Base> >, typename base_type::type&>::type
+    static typename lazy_enable_if<is_same<PL, boost::property<Tag, T, Base> >,
+                                   add_reference<typename base_type::type> >::type
     lookup(PL& prop, const PropName& tag) {
       return base_type::lookup(prop.m_base, tag);
     }
     template <typename PL>
-    static typename enable_if<is_same<PL, boost::property<Tag, T, Base> >, const typename base_type::type&>::type
+    static typename lazy_enable_if<is_same<PL, boost::property<Tag, T, Base> >,
+                                   add_reference<const typename base_type::type> >::type
     lookup(const PL& prop, const PropName& tag) {
       return base_type::lookup(prop.m_base, tag);
     }