Bot will stuck in infinite loop when receive "group upgraded to supergroup" message about telegram HOT 1 CLOSED

Got it, thanks for reporting!
I pushed a fix (786ef9c) to v3.0.13, which is also updated to the latest Telegram Bot API (v3.4).

Overview

Just a de-serialization issue; these are easy to fix, but hard to find.
I'll look some property-based testing library so I can fuzz the (de)serialization routines.

Issue

Some fields (Message.migratetoChatId) were typed ChatId.Chat, serialization was covered for the super type ChatId but not for ChatId.Chat.

Fix

Replace ChatId.Chat by Long. This is the least-resistance solution. Also considered adding yet another custom serializer for ChatId.Chat.

Compatibility issues

This change should be transparent for most users, except for a few methods that expect Option[ChatId].
e.g.

SendGame(msg.source, ...)

becomes

SendGame(ChatId(msg.source), ...)

from telegram.