decoder does not support a different type def for the same field in a message with two versions.

[Mark Turner]

Some messages have two versions. In most cases the same fields are used in both versions but in a different order. If a field is used in both versions then it must have the same type def for both versions because the decoder only creates storage for the superset of field names within a message. For example, there is no way to store a unit16_t for version 2 while storing a uint32_t for version 1. The python message code generator should produce an error if there is a type mismatch between fields with the same name in both versions of a message.