Goal:
  
  A : Type
  p : A → bool
  a : A
  l : list A
  IHl : forallb p l → Forall (λ x : A, p x) l
  H : is_true (p a && forallb p l)
  ============================
   (locked false = true)


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