Goal:
  
  A : Type
  l : list A
  P : A → bool
  n : nat
  d : A
  H : is_true (forallb P l)
  HH : #|l| ≤ n
  ============================
   (#|l| ≤ n)


DEBUG:Going to execute:
fun => <coq-core.plugins.ltac::assumption@0>