From 66514f61ff23d377f02f051a1600772613bfaef0 Mon Sep 17 00:00:00 2001
From: Eric Niebler <eric@boostpro.com>
Date: Wed, 24 Jan 2007 06:44:20 +0000
Subject: [PATCH] fix result_of ambiguity error for nullary functions

[SVN r36773]
---
 .../utility/detail/result_of_iterate.hpp      | 13 +++++++----
 include/boost/utility/result_of.hpp           | 23 ++++++++++++++++---
 test/result_of_test.cpp                       |  7 ++++++
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/include/boost/utility/detail/result_of_iterate.hpp b/include/boost/utility/detail/result_of_iterate.hpp
index 2c148bc..fa0ab89 100644
--- a/include/boost/utility/detail/result_of_iterate.hpp
+++ b/include/boost/utility/detail/result_of_iterate.hpp
@@ -24,25 +24,27 @@ struct result_of<F(BOOST_RESULT_OF_ARGS)>
     : detail::result_of_impl<F, F(BOOST_RESULT_OF_ARGS), (detail::has_result_type<F>::value)> {};
 #endif
 
+#undef BOOST_RESULT_OF_ARGS
+
+#if BOOST_PP_ITERATION() >= 1 
+
 namespace detail {
 
 template<typename R,  typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
          BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
-struct result_of_impl<R (*)(BOOST_RESULT_OF_ARGS), FArgs, false>
+struct result_of_impl<R (*)(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), FArgs, false>
 {
   typedef R type;
 };
 
 template<typename R,  typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
          BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
-struct result_of_impl<R (&)(BOOST_RESULT_OF_ARGS), FArgs, false>
+struct result_of_impl<R (&)(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), FArgs, false>
 {
   typedef R type;
 };
 
-#undef BOOST_RESULT_OF_ARGS
-
-#if BOOST_PP_ITERATION() > 1 && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
+#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
 template<typename R, typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
          BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct result_of_impl<R (T0::*)
@@ -84,3 +86,4 @@ struct result_of_impl<R (T0::*)
 #endif
 
 }
+#endif
diff --git a/include/boost/utility/result_of.hpp b/include/boost/utility/result_of.hpp
index 5c5c3d2..c2e6478 100644
--- a/include/boost/utility/result_of.hpp
+++ b/include/boost/utility/result_of.hpp
@@ -31,6 +31,24 @@ BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
 
 template<typename F, typename FArgs, bool HasResultType> struct result_of_impl;
 
+template<typename F>
+struct result_of_void_impl
+{
+  typedef void type;
+};
+
+template<typename R>
+struct result_of_void_impl<R (*)(void)>
+{
+  typedef R type;
+};
+
+template<typename R>
+struct result_of_void_impl<R (&)(void)>
+{
+  typedef R type;
+};
+
 template<typename F, typename FArgs>
 struct result_of_impl<F, FArgs, true>
 {
@@ -44,9 +62,8 @@ struct result_of_impl<F, FArgs, false>
 
 template<typename F>
 struct result_of_impl<F, F(void), false>
-{
-  typedef void type;
-};
+  : result_of_void_impl<F>
+{};
 
 } // end namespace detail
 
diff --git a/test/result_of_test.cpp b/test/result_of_test.cpp
index ea48e73..ca1cfae 100644
--- a/test/result_of_test.cpp
+++ b/test/result_of_test.cpp
@@ -50,10 +50,13 @@ int main()
 
   typedef int (*func_ptr)(float, double);
   typedef int (&func_ref)(float, double);
+  typedef int (*func_ptr_0)();
+  typedef int (&func_ref_0)();
   typedef int (X::*mem_func_ptr)(float);
   typedef int (X::*mem_func_ptr_c)(float) const;
   typedef int (X::*mem_func_ptr_v)(float) volatile;
   typedef int (X::*mem_func_ptr_cv)(float) const volatile;
+  typedef int (X::*mem_func_ptr_0)();
 
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_type(float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_of(double)>::type, int>::value));
@@ -69,9 +72,13 @@ int main()
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_type_and_float_result_of_template<void>(char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<func_ptr(char, float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<func_ref(char, float)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ptr_0()>::type, int>::value)); 
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ref_0()>::type, int>::value)); 
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_c(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_v(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_cv(X,char)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_0(X)>::type, int>::value)); 
+
   return 0;
 }