fn check_discriminators(message: &ControlMessage) -> Result<(), CodecError>Expand description
Refuse a message whose optional fields disagree with the field that decides whether they are on the wire.
Presence is not a property of the Rust value: the decoder derives it from a
Filter Type, a Content Exists flag or a Fetch Type, and reads exactly the
fields that discriminator names. An encoder that instead writes whatever
happens to be Some produces a frame its own reader refuses - short by the
missing fields, so the declared length runs out mid-payload, or long by the
surplus ones, so bytes are left over. Section 7 makes either a session
close, which is why this refuses rather than papering over it.