https://src.fedoraproject.org/rpms/dbus-c++/blob/rawhide/f/dbus-c++-template-operators.patch
https://bugs.gentoo.org/737120
https://bugs.gentoo.org/740068

commit a0b9ef3b469ca23c6a3229d8abb967cbbddcee38
Author: Peter Williams <peter@newton.cx>
Date:   Sat Dec 19 21:12:46 2015 -0500

    Fix some weird template/operator issues on OS X.
    
    I frankly don't understand at all what's going on here. These fixes
    derive from:
    
    https://chromium.googlesource.com/chromiumos/third_party/dbus-cplusplus/+/c3f69f6be02e31521474dce7eadf6ba4f4a7ce94
    https://chromium.googlesource.com/chromiumos/third_party/dbus-cplusplus/+/7104857773f790a549d399715482fa23d9b736cd
    
    Except I've dropped some changes that break the OS X build for me. Frankly, if
    it compiles, that's good enough for me.

--- a/include/dbus-c++/types.h
+++ b/include/dbus-c++/types.h
@@ -89,13 +89,7 @@ public:
   }
 
   template <typename T>
-  operator T() const
-  {
-    T cast;
-    MessageIter ri = _msg.reader();
-    ri >> cast;
-    return cast;
-  }
+  operator T() const;
 
 private:
 
@@ -316,7 +310,7 @@ struct type< Struct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14,
   }
 };
 
-} /* namespace DBus */
+extern DXXAPI DBus::MessageIter &operator << (DBus::MessageIter &iter, const DBus::Variant &val);
 
 inline DBus::MessageIter &operator << (DBus::MessageIter &iter, const DBus::Invalid &)
 {
@@ -551,6 +545,8 @@ inline DBus::MessageIter &operator >> (DBus::MessageIter &iter, DBus::Signature
   return ++iter;
 }
 
+extern DXXAPI DBus::MessageIter &operator >> (DBus::MessageIter &iter, DBus::Variant &val);
+
 template<typename E>
 inline DBus::MessageIter &operator >> (DBus::MessageIter &iter, std::vector<E>& val)
 {
@@ -644,7 +640,16 @@ inline DBus::MessageIter &operator >> (DBus::MessageIter &iter, DBus::Struct<T1,
   return ++iter;
 }
 
-extern DXXAPI DBus::MessageIter &operator >> (DBus::MessageIter &iter, DBus::Variant &val);
+template <typename T>
+inline DBus::Variant::operator T() const
+{
+  T cast;
+  DBus::MessageIter ri = _msg.reader();
+  ri >> cast;
+  return cast;
+}
+
+} /* namespace DBus */
 
 #endif//__DBUSXX_TYPES_H
 
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -34,7 +34,7 @@
 #include "message_p.h"
 #include "internalerror.h"
 
-using namespace DBus;
+namespace DBus {
 
 Variant::Variant()
   : _msg(CallMessage()) // dummy message used as temporary storage for variant data
@@ -104,3 +104,4 @@ MessageIter &operator >> (MessageIter &iter, Variant &val)
   return ++iter;
 }
 
+} /* namespace DBus */