Ticket #7343: ean_result_of_sfinae.patch

boost/utility/detail/result_of_iterate.hpp

@@ -60 +60 @@
 
 template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
          BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
-struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
+struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)),
+         typename result_of_always_void<decltype(
+           boost::declval<F>()(
+             BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), declval<T, >() BOOST_PP_INTERCEPT)
+           )
+         )>::type>
 {
   typedef decltype(
     boost::declval<F>()(

boost/utility/result_of.hpp

@@ -56 +56 @@
 #if !defined(BOOST_NO_SFINAE) && !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
 namespace detail {
 
+template<typename T>
+struct result_of_always_void
+{
+    typedef void type;
+};
+
 BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
 
 template<typename F, typename FArgs, bool HasResultType> struct tr1_result_of_impl;
-template<typename F> struct cpp0x_result_of_impl;
+template<typename F, typename Enable = void> struct cpp0x_result_of_impl {};
 
 template<typename F>
 struct result_of_void_impl

libs/utility/test/result_of_test.cpp

@@ -129 +129 @@
 #endif
 };
 
+// sfinae_tests are derived from example code from Joel de Guzman,
+// which demonstrated the interaction between result_of and SFINAE.
+template <typename F, typename Arg>
+typename boost::result_of<F(Arg const&)>::type
+sfinae_test(F f, Arg const& arg)
+{
+    return f(arg);
+}
+
+template <typename F, typename Arg>
+typename boost::result_of<F(Arg&)>::type
+sfinae_test(F f, Arg& arg)
+{
+    return f(arg);
+}
+
+int sfinae_test_f(int& i)
+{
+    return i;
+}
+
 struct X {};
 
 int main()
@@ -268 +289 @@
 #endif
 #endif
 
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE)
+  int i = 123;
+  sfinae_test(sfinae_test_f, i);
+#endif // defined(BOOST_RESULT_OF_USE_DECLTYPE)
+
   return 0;
 }