Goal:
  
  ============================
   (∀ (A B : Type) (R : A → B → Type) (R' : ∀ (a : A) (b : B), R a b → Type) 
      (xs : list A) (ys : list B) (a : All2 R xs ys) 
      (a0 b : All2_dep R' a),
      a0 = b → NoConfusionHom_All2_dep A B R R' xs ys a a0 b)


DEBUG:Going to execute:
simpl; intros