Admitted. (* QuickChick andb_false_r. *)
Derive ArbitrarySizedSuchThat for (fun m => le n m).
Derive SizeMonotonicSuchThatOpt for (fun m => le n m).
Derive GenSizedSuchThatSizeMonotonicOpt for (fun m => le n m).
Derive SizedProofEqs for (fun m => le n m).
Derive GenSizedSuchThatCorrect for (fun m => le n m).

Theorem plus_ble_compat_l : forall n m p : nat,
leb n m = true -> leb (p + n) (p + m) = true.