Goal:
    A : Type  B : Type  R : nat → A → B → Type  n : nat  H : True
  ============================
   (let H := CoreTactics.block in All2i_nil = All2i_nil)


DEBUG:Going to execute:
CoreTactics.block_goal
Level 8: evaluation returns
idtac of type tacvalue

Level 6: evaluation returns
idtac of type tacvalue

Level 5: evaluation returns
idtac of type tacvalue