Definition no_msg_from_to from to (d : soup) :=
forall i tms b,
find i d = Some (Msg tms from to b) -> b = false.

Lemma msg_spec_consume s from to tg cnt cnt' i :
valid s ->
find i s = Some {| content := TMsg tg cnt';
from := from; to := to; active := true |} ->
msg_spec from to tg cnt s ->
no_msg_from_to from to (consume_msg s i).