Goal:
  
  A : Type
  B : Type
  C : Type
  R : A → B → C → Type
  b0 : All3 R [] [] []
  x : A
  y : B
  z : C
  l : list A
  l' : list B
  l'' : list C
  r : R x y z
  b : All3 R l l' l''
  ============================
   ({|
      pr1 := {| pr1 := []; pr2 := {| pr1 := []; pr2 := [] |} |}; pr2 := b0
    |} =
    {|
      pr1 :=
        {| pr1 := x :: l; pr2 := {| pr1 := y :: l'; pr2 := z :: l'' |} |};
      pr2 := All3_cons r b
    |}
    → ∀ (H := CoreTactics.block) (e : NoConfusionHom_All3 A B C R [] [] []
                                        All3_nil b0),
        let H0 := CoreTactics.block in
        noConfusionHom_All3_obligation_2 A B C R [] [] [] All3_nil b0
          (noConfusionHom_All3_obligation_1 A B C R [] [] [] All3_nil b0 e) =
        e)


DEBUG:Going to execute:
match goal with
           | |- context [ eq_rect_r _ _ eq_refl ] => progress simpl eq_rect_r
           | |- context [ eq_rect _ _ _ _ eq_refl ] => progress simpl eq_rect
           | |- context [ Prop.Logic.transport _ eq_refl _ ] =>
                 progress simpl Prop.Logic.transport
           | |- context [ Logic.eq_elim _ _ _ _ _ eq_refl ] =>
                 progress simpl eq_rect
           | |- context [ Logic.eq_elim_r _ _ _ _ eq_refl ] =>
                 progress simpl Logic.eq_elim_r
           | |- context [ noConfusion_inv _ ] =>
                 progress simpl noConfusion_inv
           | |- DepElim.opaque_ind_pack_eq_inv ?G eq_refl =>
                 apply (DepElim.simplify_ind_pack_inv B x p G)
           | |- let _ := CoreTactics.block in _ => fail 1
           | |- _ => simplify * || simplify ?; cbv beta
           | |- _ → ?B =>
                 let ty := type of B in
                 intro || (let H := fresh in
                           intro
                           H)
           | |- ∀ x, _ => let H := fresh x in
                          intro
                          H
           | |- _ => intro
           end