From 379200dfd15c4f239870cb81d4ebe31a981a540f Mon Sep 17 00:00:00 2001
From: Andrey Semashev <andrey.semashev@gmail.com>
Date: Fri, 8 Sep 2017 18:12:02 +0300
Subject: [PATCH] Force result_of use decltype whenever possible to maximize
 testing of function input iterator with lambdas.

---
 test/function_input_iterator_test.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/test/function_input_iterator_test.cpp b/test/function_input_iterator_test.cpp
index 5443a11..6be27d2 100644
--- a/test/function_input_iterator_test.cpp
+++ b/test/function_input_iterator_test.cpp
@@ -10,6 +10,16 @@
 #include <vector>
 
 #include <boost/config.hpp>
+
+#if !defined(BOOST_NO_CXX11_DECLTYPE)
+// Force boost::result_of use decltype, even on compilers that don't support N3276.
+// This enables this test to also verify if the iterator works with lambdas
+// on such compilers with this config macro. Note that without the macro result_of
+// (and consequently the iterator) is guaranteed to _not_ work, so this case is not
+// worth testing anyway.
+#define BOOST_RESULT_OF_USE_DECLTYPE
+#endif
+
 #include <boost/core/lightweight_test.hpp>
 #include <boost/iterator/function_input_iterator.hpp>
 
@@ -90,7 +100,7 @@ int main()
         BOOST_TEST_EQ(generated[i], static_cast<int>(42 + i));
 
 #if !defined(BOOST_NO_CXX11_LAMBDAS) && !defined(BOOST_NO_CXX11_AUTO_DECLARATIONS) \
-    && (!defined(BOOST_NO_CXX11_DECLTYPE_N3276) || defined(BOOST_RESULT_OF_USE_DECLTYPE))
+    && defined(BOOST_RESULT_OF_USE_DECLTYPE)
     // test the iterator with lambda expressions
     int num = 42;
     auto lambda_generator = [&num] { return num++; };