AK: Destroy original value when assigning to Variant

Author: https://github.com/BertalanD
Commit: https://github.com/SerenityOS/serenity/commit/39dd13fd17f
Pull-request: https://github.com/SerenityOS/serenity/pull/8391
Reviewed-by: https://github.com/alimpfard

AK/Variant.h

@@ -266,6 +266,9 @@ public:
         requires(!(IsTriviallyCopyConstructible<Ts> && ...) || !(IsTriviallyDestructible<Ts> && ...))
 #endif
     {
+        if constexpr (!(IsTriviallyDestructible<Ts> && ...)) {
+            Helper::delete_(m_index, m_data);
+        }
         m_index = other.m_index;
         Helper::copy_(other.m_index, other.m_data, m_data);
         return *this;
@@ -276,6 +279,9 @@ public:
         requires(!(IsTriviallyMoveConstructible<Ts> && ...) || !(IsTriviallyDestructible<Ts> && ...))
 #endif
     {
+        if constexpr (!(IsTriviallyDestructible<Ts> && ...)) {
+            Helper::delete_(m_index, m_data);
+        }
         m_index = other.m_index;
         Helper::move_(other.m_index, other.m_data, m_data);
         return *this;

Tests/AK/TestVariant.cpp

@@ -57,6 +57,12 @@ TEST_CASE(destructor)
         Variant<DestructionChecker> test_variant { DestructionChecker { was_destroyed } };
     }
     EXPECT(was_destroyed);
+
+    bool was_destroyed_when_assigned_to = false;
+    Variant<DestructionChecker, int> original { DestructionChecker { was_destroyed_when_assigned_to } };
+    Variant<DestructionChecker, int> other { 42 };
+    original = other;
+    EXPECT(was_destroyed_when_assigned_to);
 }
 
 TEST_CASE(move_moves)