Goal:
  
  A : Type
  P : nat → A → Type
  f : nat → A → A
  n : nat
  H : ∀ (n : nat) (x : A), P n x → f n x = x
  ============================
   ([] = [])


DEBUG:Going to execute:
<Coq.Init.Tauto.flatten_contravariant_disj> flags X1 X2 id
Level 2: evaluation returns
<coq-core.plugins.tauto::flatten_contravariant_conj@0>
where
tauto_flags := 
of type
tauto_flags
id := f
of type
constr
X2 := A → A
of type
constr
X1 := nat
of type
constr of type tacvalue

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.