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
  H : NoConfusionHom_All2i A B R n l0 l a b
  ============================
   (a = b)


DEBUG:Going to execute:
CoreTactics.destruct_sigma b
Level 3: evaluation returns
idtac of type tacvalue