Goal:
    A : Type  B : Type  R : nat → A → B → Type  n : nat  H : True
  ============================
   (All2i_nil = All2i_nil)


DEBUG:Going to execute:
(DepElim.is_introduced H; CoreTactics.block_goal;
             CoreTactics.revert_until H; CoreTactics.block_goal) ||
             (let H' := fresh H in
              intros until H'; CoreTactics.block_goal) ||
               (intros; CoreTactics.block_goal)