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- // 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 <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>( v2 );
- }
- 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
- }
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