cpp: Fix evmc::result's move assignment operator

include/evmc/evmc.hpp

@@ -39,16 +39,22 @@ public:
     /// Move constructor.
     result(result&& other) noexcept : evmc_result{other}
     {
-        // Disable releaser of the rvalue object.
-        other.release = nullptr;
+        other.release = nullptr;  // Disable releasing of the rvalue object.
     }
 
     result(result const&) = delete;
 
-    /// Move-and-swap assignment operator.
-    result& operator=(result other) noexcept
+    /// Move assignment operator.
+    ///
+    /// The self-assigment MUST never happen.
+    ///
+    /// @param other The other result object.
+    /// @return      The reference to the left-hand side object.
+    result& operator=(result&& other) noexcept
     {
-        std::swap(*this, other);
+        this->~result();                           // Release this object.
+        static_cast<evmc_result&>(*this) = other;  // Copy data.
+        other.release = nullptr;                   // Disable releasing of the rvalue object.
         return *this;
     }