Program Instance unsizedMonotonicChecker (c : Checker) `{UnsizedChecker c} : 
  SizeMonotonicChecker c.

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).