Program Instance unsizedMonotonicChecker (c : Checker) `{UnsizedChecker c} :
SizeMonotonicChecker c.
Next Obligation.
rewrite unsizedChecker. move => b Hb. by eauto.
Qed.

Lemma semCallback_id {C} `{Checkable C} (cb : Callback) (c : C) :
semChecker (callback cb c) <-> semCheckable c.