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 : sigma
         (λ index : sigma (λ _ : nat, sigma (λ _ : list A, list B)),
            All2i R (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
  ============================
   ({|
      pr1 := {| pr1 := n; pr2 := {| pr1 := x :: l; pr2 := y :: r |} |};
      pr2 := b
    |} = b0
    → 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:
try rename id into id',id' into id
Level 4: evaluation returns
try rename id into id',id' into id; cont id'1 id
where
t := {|
       pr1 := {| pr1 := n; pr2 := {| pr1 := x :: l; pr2 := y :: r |} |};
       pr2 := b
     |}
of type
constr
id'1 := b
of type
constr
id' := b0
of type
constr
id := b
of type
constr
cont := fun id id' => DepElim.decompose_exists id id'
        where
        id := b
        of type
        constr
of type
tacvalue of type tacvalue