Add test/variant_default_construct(_cx)

test/Jamfile

@@ -19,3 +19,5 @@ run get_by_index.cpp : : : $(REQ) ;
 compile get_by_index_cx.cpp : : : $(REQ) ;
 run get_by_type.cpp : : : $(REQ) ;
 compile get_by_type_cx.cpp : : : $(REQ) ;
+run variant_default_construct.cpp : : : $(REQ) ;
+compile variant_default_construct_cx.cpp : : : $(REQ) ;

test/variant_default_construct.cpp

@@ -0,0 +1,95 @@
+
+// Copyright 2017 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <utility>
+#include <string>
+
+using namespace boost::variant2;
+
+struct X
+{
+    X();
+};
+
+int main()
+{
+    {
+        variant<int> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+    }
+
+    {
+        variant<int const> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+    }
+
+    {
+        variant<int, float, std::string> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+    }
+
+    {
+        variant<int, int, std::string> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+    }
+
+    {
+        variant<std::string> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), std::string() );
+    }
+
+    {
+        variant<std::string const> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), std::string() );
+    }
+
+    {
+        variant<std::string, int, float> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), std::string() );
+    }
+
+    {
+        variant<std::string, std::string, float> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), std::string() );
+    }
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int const>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int, X>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int, float, X>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int, int, X>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_nothrow_default_constructible<variant<int, X, X>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_nothrow_default_constructible<variant<X>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_nothrow_default_constructible<variant<X, int>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_nothrow_default_constructible<variant<X, int, float>>));
+    }
+
+    return boost::report_errors();
+}

test/variant_default_construct_cx.cpp

@@ -0,0 +1,51 @@
+
+// Copyright 2017 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+int main()
+{
+    {
+        constexpr variant<int> v;
+
+        STATIC_ASSERT( v.index() == 0 );
+        STATIC_ASSERT( get<0>(v) == 0 );
+    }
+
+    {
+        constexpr variant<int const> v;
+
+        STATIC_ASSERT( v.index() == 0 );
+        STATIC_ASSERT( get<0>(v) == 0 );
+    }
+
+    {
+        constexpr variant<int, float> v;
+
+        STATIC_ASSERT( v.index() == 0 );
+        STATIC_ASSERT( get<0>(v) == 0 );
+    }
+
+    {
+        constexpr variant<int, int, float> v;
+
+        STATIC_ASSERT( v.index() == 0 );
+        STATIC_ASSERT( get<0>(v) == 0 );
+    }
+
+    {
+        constexpr variant<int, float, float> v;
+
+        STATIC_ASSERT( v.index() == 0 );
+        STATIC_ASSERT( get<0>(v) == 0 );
+    }
+}