Goal:
  
  A : Type
  B : Type
  k : nat
  Q : nat → A → Type
  R : nat → A → B → Type
  l : list A
  l' : list B
  n : nat
  q1 : sigma (λ _ : nat, list A)
  q2 : (λ index : sigma (λ _ : nat, list A), Alli Q (pr1 index) (pr2 index))
         q1
  ============================
   ({| pr1 := n; pr2 := [] |} = q1
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in
      All2i (λ (i : nat) (x : A) (y : B), Q i x × R i x y) n [] [])


DEBUG:Going to execute:
try unfold signature in id'2