From c4cba6086bc4d3080c4e6bf1d69662e3fad0437e Mon Sep 17 00:00:00 2001
From: Khomutov Nikita <inikitah@gmail.com>
Date: Mon, 10 Feb 2020 13:39:12 +0300
Subject: [PATCH] Create default.cpp

The test is related to issues #91 and #95 . It is a regression introduced to 1.71 release on compilers supporting C++11.

Since 1.71 the result of `Params::foo_t` is `B` which means that provided parameter `type_foo_param` (set to `A`) is dropped and failed back to default one (`B`).
---
 test/default.cpp | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 test/default.cpp

diff --git a/test/default.cpp b/test/default.cpp
new file mode 100644
index 00000000..1470ef6f
--- /dev/null
+++ b/test/default.cpp
@@ -0,0 +1,64 @@
+#include <boost/parameter/parameters.hpp>
+#include <boost/parameter/name.hpp>
+
+#if __cplusplus >= 201103L
+  #include <type_traits>
+#else // C++03
+  #include <boost/mpl/bool.hpp>
+  #include <boost/mpl/not.hpp>
+  #include <boost/mpl/assert.hpp>
+  #include <boost/type_traits/is_same.hpp>
+#endif
+
+
+BOOST_PARAMETER_TEMPLATE_KEYWORD(type_foo_param)
+BOOST_PARAMETER_TEMPLATE_KEYWORD(type_bar_param)
+
+class A {};
+class B {};
+class C {};
+
+
+#if __cplusplus >= 201103L
+    template<class... Args>
+    class DefaultParams 
+    {
+    public:
+        typedef typename boost::parameter::parameters<
+            boost::parameter::optional<tag::type_foo_param>
+        >::bind<Args...>::type args;
+  
+        typedef typename boost::parameter::value_type<
+            args, tag::type_foo_param,  B
+        >::type foo_t;
+    };
+#else // C++03
+    template<class Arg0, class Arg1>
+    class DefaultParams 
+    {
+    public:
+        typedef typename boost::parameter::parameters<
+            boost::parameter::optional<tag::type_foo_param>
+        >::bind<Arg0, Arg1>::type args;
+  
+        typedef typename boost::parameter::value_type<
+            args, tag::type_foo_param,  B
+        >::type foo_t;
+    };
+#endif 
+
+void test()
+{
+    typedef DefaultParams<
+        type_bar_param<C>,
+        type_foo_param<A>
+    > Params;
+
+#if __cplusplus >= 201103L
+    static_assert(std::is_same<Params::foo_t, A>::value, "Expected A type");
+    static_assert(!std::is_same<Params::foo_t, B>::value, "Failing back to default value is not allowed here");
+#else // C++03
+    BOOST_MPL_ASSERT(( boost::is_same<Params::foo_t, A> ));
+    BOOST_MPL_ASSERT(( boost::mpl::not_< boost::is_same<Params::foo_t, B> > ));
+#endif
+}