Goal:
  
  A : Type
  B : Type
  C : Type
  P : nat → A → B → Type
  Q : B → C → Type
  R : nat → A → C → Type
  S : nat → A → C → Type
  l'' : list C
  n : nat
  b1' : list B
  b1 : list C
  b : All2 Q b1' b1
  ============================
   ({| pr1 := []; pr2 := l'' |} = {| pr1 := b1'; pr2 := b1 |}
    → let H := CoreTactics.block in
      All2i R n [] l''
      → (∀ (n : nat) (x : A) (y : B) (z : C),
           P n x y → Q y z → R n x z → S n x z)
        → let H0 := CoreTactics.block in All2i S n [] l'')


DEBUG:Going to execute:
let eliminator := eval simpl in DepElim.elim in
           tac p eliminator
DEBUG LTAC Evaluated term: b
DEBUG LTAC Evaluated term: (All2 Q b1' b1)