Add tests for holds_alternative

test/holds_alternative_cx.cpp

@@ -0,0 +1,43 @@
+
+// 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( holds_alternative<int>( v ) );
+    }
+
+    {
+        constexpr variant<int, float> v;
+        STATIC_ASSERT( holds_alternative<int>( v ) );
+        STATIC_ASSERT( !holds_alternative<float>( v ) );
+    }
+
+    {
+        constexpr variant<int, float> v( 3.14f );
+        STATIC_ASSERT( !holds_alternative<int>( v ) );
+        STATIC_ASSERT( holds_alternative<float>( v ) );
+    }
+
+    {
+        constexpr variant<int, float, float> v;
+        STATIC_ASSERT( holds_alternative<int>( v ) );
+    }
+
+    {
+        constexpr variant<int, int, float> v( 3.14f );
+        STATIC_ASSERT( holds_alternative<float>( v ) );
+    }
+}