Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  a : A
  Γ : list A
  d' : A
  Γ'0 : list A
  Hrel : All2_fold P Γ Γ'0
  p : P Γ Γ'0 a d'
  ============================
   (Some d' = Some ?d')


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

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.