Goal:
  
  ============================
   (∀ (A B C : Type) (R : A → B → C → Type) (l0 : list A) 
      (l1 : list B) (l : list C) (a b : All3 R l0 l1 l),
      a = b → NoConfusionHom_All3 A B C R l0 l1 l a b)


DEBUG:Going to execute:
simpl; intros