From ac9f617f7f629270180d8a2d75ce9da603b0161c Mon Sep 17 00:00:00 2001
From: Daniel Walker <daniel.j.walker@gmail.com>
Date: Wed, 19 Sep 2012 23:10:08 +0000
Subject: [PATCH] SFINAE enabled result_of fixes [7343]

[SVN r80605]
---
 .../utility/detail/result_of_iterate.hpp      | 66 ++++++++++++++++++-
 include/boost/utility/result_of.hpp           | 18 ++++-
 test/result_of_test.cpp                       | 26 ++++++++
 3 files changed, 107 insertions(+), 3 deletions(-)

diff --git a/include/boost/utility/detail/result_of_iterate.hpp b/include/boost/utility/detail/result_of_iterate.hpp
index 5cf30b6..df05bbf 100644
--- a/include/boost/utility/detail/result_of_iterate.hpp
+++ b/include/boost/utility/detail/result_of_iterate.hpp
@@ -58,17 +58,79 @@ struct result_of<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
 
 namespace detail {
 
+#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
+
 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))>
+class is_callable<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))> {
+    typedef char (&pass)[1];
+    typedef char (&fail)[2];
+
+    template<typename G BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
+             BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename S)>
+    struct sub {};
+    template<typename S>
+    struct stub {};
+
+    template<typename G BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
+             BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename S)>
+    static pass test(sub<G BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
+                         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),S)>
+                   , stub<
+                          decltype(
+                              boost::declval<G>()(
+                                  BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<S, >() BOOST_PP_INTERCEPT)
+                              )
+                          )
+                      >* x = 0);
+    static fail test(...);
+
+public:
+    const static bool value = sizeof(pass) == sizeof(test(sub<F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
+                                                              BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)
+                                                          >()));
+    typedef typename boost::mpl::bool_<value>::type type;
+};
+
+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)), true>
+    : lazy_enable_if<
+          is_callable<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
+        , cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), false>
+      >
+{};
+
+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)), false>
 {
   typedef decltype(
     boost::declval<F>()(
-      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), declval<T, >() BOOST_PP_INTERCEPT)
+      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
     )
   ) type;
 };
 
+#else // BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
+
+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)), 
+                            typename result_of_always_void<decltype(
+                                boost::declval<F>()(
+                                    BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
+                                )
+	                    )>::type> {
+  typedef decltype(
+    boost::declval<F>()(
+      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
+    )
+  ) type;
+};
+
+#endif // BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
+
 } // namespace detail 
 
 #else // defined(BOOST_RESULT_OF_USE_DECLTYPE)
diff --git a/include/boost/utility/result_of.hpp b/include/boost/utility/result_of.hpp
index 93b7264..222c9c9 100644
--- a/include/boost/utility/result_of.hpp
+++ b/include/boost/utility/result_of.hpp
@@ -25,6 +25,7 @@
 #include <boost/type_traits/is_member_function_pointer.hpp>
 #include <boost/type_traits/remove_cv.hpp>
 #include <boost/utility/declval.hpp>
+#include <boost/utility/enable_if.hpp>
 
 #ifndef BOOST_RESULT_OF_NUM_ARGS
 #  define BOOST_RESULT_OF_NUM_ARGS 16
@@ -59,7 +60,22 @@ namespace detail {
 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;
+
+#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
+
+template<typename F> class is_callable;
+template<typename F, bool TestCallability = true> struct cpp0x_result_of_impl;
+
+#else // BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
+
+template<typename T>
+struct result_of_always_void
+{
+    typedef void type;
+};
+template<typename F, typename Enable = void> struct cpp0x_result_of_impl {};
+
+#endif // BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1700))
 
 template<typename F>
 struct result_of_void_impl
diff --git a/test/result_of_test.cpp b/test/result_of_test.cpp
index 3f6da9e..0c2834f 100644
--- a/test/result_of_test.cpp
+++ b/test/result_of_test.cpp
@@ -129,6 +129,27 @@ struct no_result_type_or_result_template
 #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()
@@ -268,5 +289,10 @@ int main()
 #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;
 }