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


DEBUG:Going to execute:
fun tac => lazymatch goal with
                      | H:_ |- _ => tac H
                      end