Goal:
  
  A : Type
  B : Type
  R : nat → A → B → Type
  l2 : list A
  r2 : list B
  n : nat
  h2 : All2i R n l2 r2
  ============================
   (All2i R n l2 r2)


DEBUG:Going to execute:
fun => <coq-core.plugins.ltac::assumption@0>