Goal:
  
  A : Type
  B : Type
  R : nat → A → B → Type
  n : nat
  x : A
  y : B
  l : list A
  r : list B
  r0 : R n x y
  a : All2i R (S n) l r
  b : All2i R n (x :: l) (y :: r)
  b0 := {|
          pr1 := {| pr1 := n; pr2 := {| pr1 := x :: l; pr2 := y :: r |} |};
          pr2 := b
        |}
     : sigma
         (λ index : sigma (λ _ : nat, sigma (λ _ : list A, list B)),
            All2i R (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
  ============================
   (let H := CoreTactics.block in
    NoConfusionHom_All2i A B R n (x :: l) (y :: r) (All2i_cons r0 a) b
    → let H0 := CoreTactics.block in All2i_cons r0 a = b)


DEBUG:Going to execute:
lazymatch goal with
           | id':=?v:_
             |- context [ id ] =>
                 generalize (eq_refl : v = id'); clearbody id'; simpl in id';
                  cont id id' id v
           | id':=?v:_
             |- _ =>
                 let id'1 := fresh id' in
                 let id'2 := fresh id' in
                 set (id'2 := pr2 id'); set (id'1 := pr1 id') in id'2;
                  hnf in (value of id'1), (value of id'2);
                  try red in (type of id'2);
                  match goal with
                  | id'1:=?t:_
                    |- _ =>
                        generalize (eq_refl : t = id'1); clearbody id'2 id'1;
                         clear id' id; try unfold signature in id'2;
                         hnf in id'2; simpl in id'2; rename id'2 into id;
                         cont id id id'1 t
                  end
           end