Message.Marshal() does not return an error for rootless messages

[rmmh]

Is there ever a reason you'd want to marshal a message without setting its root? It took me a while to discover why I couldn't Unmarshal the resulting bytes.

[matheusd]

Ultimately, that's a mix of an implementation and API issue. I can't think of a reason to marshal a rootless message.

The underlying issue is that the current API for new messages already allocates the space for the root pointer (but doesn't make it point anywhere), so that's why you get a weird stream instead of a nil, len(0) or error.