Merge pull request #1112 from uyha/same-type-variant

Fix compilation error when `std::variant` has the same types

Author: redboltz

include/msgpack/v1/adaptor/cpp17/variant.hpp

@@ -40,11 +40,11 @@ Variant construct_variant(
     std::index_sequence<current_index, indices...>
 ) {
     if constexpr(sizeof...(Ts) == 0) {
-        return object.as<T>();
+        return Variant{std::in_place_index<current_index>, object.as<T>()};
     }
     else {
         if (index == current_index) {
-            return object.as<T>();
+            return Variant{std::in_place_index<current_index>, object.as<T>()};
         }
         return construct_variant<Variant, Ts...>(
             index,

test/msgpack_cpp17.cpp

@@ -474,6 +474,28 @@ BOOST_AUTO_TEST_CASE(variant_pack_unpack_as) {
         oh.get().as<std::variant<bool, int, float, double> >();
     BOOST_CHECK(val1 == val2);
     BOOST_CHECK_THROW((oh.get().as<std::variant<bool>>()), msgpack::type_error);
+
+    {
+      std::stringstream same_ss;
+      std::variant<int, float, int> same_expected{std::in_place_index<2>, 2};
+      msgpack::pack(same_ss, same_expected);
+      std::string const& same_str = same_ss.str();
+      msgpack::object_handle same_oh =
+          msgpack::unpack(same_str.data(), same_str.size());
+      std::variant<int, float, int> same_actual = same_oh->as<std::variant<int, float, int>>();
+      BOOST_CHECK(same_expected == same_actual);
+    }
+
+    {
+      std::stringstream same_ss;
+      std::variant<int, int> same_expected{std::in_place_index<1>, 2};
+      msgpack::pack(same_ss, same_expected);
+      std::string const& same_str = same_ss.str();
+      msgpack::object_handle same_oh =
+          msgpack::unpack(same_str.data(), same_str.size());
+      std::variant<int, int> same_actual = same_oh->as<std::variant<int, int>>();
+      BOOST_CHECK(same_expected == same_actual);
+    }
 }
 
 BOOST_AUTO_TEST_CASE(variant_with_zone) {