Goal:
  
  A : Type
  p : A → bool
  n : nat
  a : A
  l : list A
  IHl : ∀ n : nat, forallb p l → forallb p (skipn n l)
  H : p a ∧ forallb p l
  ============================
   (is_true (forallb p l))


DEBUG:Going to execute:
elim id
Level 2: evaluation returns
<coq-core.plugins.tauto::is_conj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := p a ∧ forallb p l
of type
constr of type tacvalue