fix smart convert panic

proto/smart_convert.go

@@ -47,7 +47,8 @@ func SmartConvert(from reflect.Value, to reflect.Type) (ret reflect.Value) {
 		if from.IsNil() {
 			return reflect.Zero(to)
 		}
-		ret = SmartConvert(from.Elem(), to.Elem()).Addr()
+		ret = reflect.New(to.Elem())
+		ret.Elem().Set(SmartConvert(from.Elem(), to.Elem()))
 	case reflect.Slice:
 		l := from.Len()
 		ret = reflect.MakeSlice(to, l, l)

proto/smart_convert_test.go

@@ -46,3 +46,23 @@ func TestRegisterUntilLatest(t *testing.T) {
 		t.Errorf("handler not called")
 	}
 }
+
+var TestData = []struct{ V, T, E any }{
+	{V: &v1_21_9.PlayToClientPacketPosition{Flags: v1_21_9.PlayToClientPositionUpdateRelatives{Val: 2}, X: 5}, T: &v1_21_8.PlayToClientPacketPosition{}},
+	{V: &v1_21_9.ConfigurationToClientPacketTags{}, T: &v1_21_8.ConfigurationToClientPacketTags{}},
+	{V: &v1_21_11.PlayToServerPacketChatMessage{Signature: &[256]byte{}}, T: &v1_21_8.PlayToServerPacketChatMessage{}},
+}
+
+func TestSmartConvert(t *testing.T) {
+	for _, d := range TestData {
+		can := proto.SmartConvertibleTo(reflect.TypeOf(d.V), reflect.TypeOf(d.T))
+		if !can {
+			t.Errorf("can't smart convert %#v to %#v", d.V, d.T)
+			continue
+		}
+		got := proto.SmartConvert(reflect.ValueOf(d.V), reflect.TypeOf(d.T))
+		if d.E != nil && !reflect.DeepEqual(got.Interface(), d.E) {
+			t.Errorf("got %#v, want %#v", got.Interface(), d.E)
+		}
+	}
+}