iox-eclipse-iceoryx#2414 Use placement new to construct a new object during assignment

Author: yuanxingyang

doc/website/release-notes/iceoryx-unreleased.md

@@ -148,6 +148,7 @@
 - Depend on @ncurses when building with Bazel [#2372](https://github.com/eclipse-iceoryx/iceoryx/issues/2372)
 - Fix windows performance issue [#2377](https://github.com/eclipse-iceoryx/iceoryx/issues/2377)
 - Max Client and Server cannot be configured independently of Max Publisher and Subscriber [#2394](https://github.com/eclipse-iceoryx/iceoryx/issues/2394)
+- Use placement new to construct a new object during assignment [#2414](https://github.com/eclipse-iceoryx/iceoryx/issues/2414)
 
 **Refactoring:**
 

iceoryx_hoofs/test/moduletests/test_vocabulary_variant.cpp

@@ -467,13 +467,13 @@ TEST_F(variant_Test, DirectValueAssignmentResultsInCorrectIndex)
     EXPECT_THAT(schlomo.index(), Eq(0U));
 }
 
-TEST_F(variant_Test, DirectValueAssignmentWhenAlreadyAssignedWithDifferentType)
+TEST_F(variant_Test, DirectValueAssignmentWhenAlreadyAssignedWithDifferentTypeResultsInCorrectIndex)
 {
-    ::testing::Test::RecordProperty("TEST_ID", "a058c173-497b-43ec-ba03-2702f3ba8190");
+    ::testing::Test::RecordProperty("TEST_ID", "f9f10061-b7f2-4e8f-a4b2-c04478046dcd");
     iox::variant<int, float> schlomo;
     schlomo = 123;
     schlomo = 123.01F;
-    EXPECT_THAT(schlomo.index(), Eq(0U));
+    EXPECT_THAT(schlomo.index(), Eq(1U));
 }
 
 TEST_F(variant_Test, HoldsAlternativeForCorrectType)

iceoryx_hoofs/vocabulary/include/iox/detail/variant.inl

@@ -149,25 +149,21 @@ template <typename T>
 inline typename std::enable_if<!std::is_same<T, variant<Types...>&>::value, variant<Types...>>::type&
 variant<Types...>::operator=(T&& rhs) noexcept
 {
-    if (m_type_index == INVALID_VARIANT_INDEX)
+    if (m_type_index != internal::get_index_of_type<0, T, Types...>::index)
     {
+        call_element_destructor();
+        // NOLINTJUSTIFICATION clang-tidy suggests that std::move(rhs) might erroneously move an lvalue, but here rhs is already T&&, so it's safe.
+        // NOLINTNEXTLINE(bugprone-move-forwarding-reference)
+        new (&m_storage) T(std::move(rhs));
         m_type_index = internal::get_index_of_type<0, T, Types...>::index;
     }
-
-    if (!has_bad_variant_element_access<T>())
+    else
     {
         // AXIVION Next Construct AutosarC++19_03-M5.2.8: conversion to typed pointer is intentional, it is correctly aligned and points to sufficient memory for a T by design
         // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
         auto storage = reinterpret_cast<T*>(&m_storage);
         *storage = std::forward<T>(rhs);
     }
-    else
-    {
-        error_message(__PRETTY_FUNCTION__,
-                      "wrong variant type assignment, another type is already "
-                      "set in variant");
-    }
-
     return *this;
 }