Goal:
  
  A : Type
  B : Type
  R : nat → A → B → Type
  n : nat
  l0 : list A
  l : list B
  a : All2i R n l0 l
  b : All2i R n l0 l
  e : NoConfusionHom_All2i A B R n l0 l a b
  ============================
   (noConfusionHom_All2i_obligation_2 A B R n l0 l a b
      (noConfusionHom_All2i_obligation_1 A B R n l0 l a b e) = e)


DEBUG:Going to execute:
match type of id with
           | sigma ?P =>
               let idx := fresh "idx" in
               destruct id as [idx id]; repeat CoreTactics.destruct_sigma idx;
                simpl in id
           | _ => idtac
           end