Added upcasting to Util::ReturnVal

Common/modules/Result.h

@@ -78,6 +78,20 @@ namespace LXC::Util
                 : m_Error(error.error), m_FunctionFailed(true)
             {}
 
+            // Constructor to support upcasting //
+            template<typename Other>
+                requires std::is_convertible_v<Other, ResultType>
+            ReturnVal(ReturnVal<Other, ErrorType>&& other)
+                : m_FunctionFailed(other.m_FunctionFailed)
+            {
+                // Transfers the correct member of the union //
+                if (m_FunctionFailed)
+                    m_Error = std::move(other.m_Error);
+
+                else
+                    m_Result = std::move(other.m_Result);
+            }
+
             // Destructor //
             ~ReturnVal() {};