constexpr the copy/move constructors; change copy/move assign to not require constexpr lambdas

2017-06-09 17:24:23 +03:00
parent f216bb5c1f
commit 82104cd55e
6 changed files with 291 additions and 25 deletions
@@ -0,0 +1,113 @@
+
+// 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
+
+#if !defined( __cpp_constexpr ) || __cpp_constexpr < 201603
+
+// no constexpr lambda support
+int main() {}
+
+#else
+
+#include <boost/variant2/variant.hpp>
+#include <utility>
+
+using namespace boost::variant2;
+
+struct X
+{
+    int v;
+    X() = default;
+    constexpr X( int v ): v( v ) {}
+    constexpr operator int() const { return v; }
+};
+
+struct Y
+{
+    int v;
+    constexpr Y(): v() {}
+    constexpr Y( int v ): v( v ) {}
+    constexpr operator int() const { return v; }
+};
+
+enum E
+{
+    v
+};
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+template<class T, class V> constexpr T test( V&& v )
+{
+    V v2( std::forward<V>(v) );
+    return get<T>(v);
+}
+
+int main()
+{
+    {
+        constexpr auto w = test<int>( variant<int>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+    {
+        constexpr auto w = test<X>( variant<X>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+#if defined( BOOST_LIBSTDCXX_VERSION ) && BOOST_LIBSTDCXX_VERSION < 50000
+#else
+
+    {
+        constexpr auto w = test<Y>( variant<Y>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+#endif
+
+    {
+        constexpr auto w = test<int>( variant<int, float>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+    {
+        constexpr auto w = test<float>( variant<int, float>( 3.0f ) );
+        STATIC_ASSERT( w == 3.0f );
+    }
+
+    {
+        constexpr auto w = test<float>( variant<int, int, float>( 3.0f ) );
+        STATIC_ASSERT( w == 3.0f );
+    }
+
+    {
+        constexpr auto w = test<X>( variant<E, E, X>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+    {
+        constexpr auto w = test<X>( variant<int, int, float, float, X>( X(1) ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+#if defined( BOOST_LIBSTDCXX_VERSION ) && BOOST_LIBSTDCXX_VERSION < 50000
+#else
+
+    {
+        constexpr auto w = test<Y>( variant<E, E, Y>( 1 ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+    {
+        constexpr auto w = test<Y>( variant<int, int, float, float, Y>( Y(1) ) );
+        STATIC_ASSERT( w == 1 );
+    }
+
+#endif
+}
+
+#endif // constexpr lambda support