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

Lemma semShrinking_id {C A} {HCheck : Checkable C}
(sh : A -> list A) (x : A) (pf : A -> C)  :
semChecker (shrinking sh x pf) <->
semCheckable (pf x).