Goal:
  
  A : Type
  B : Type
  C : Type
  Q : C → Type
  R : C → A → Prop
  f : ∀ x : A, (∀ y : C, Q y → R y x) → B
  x : A
  xs : list A
  h : ∀ y : C, Q y → ∥ All (R y) (x :: xs) ∥
  X : (λ (l : list A) (Hl : ∀ y : C, Q y → ∥ All (R y) l ∥) (x : list B),
         ∀ (H := CoreTactics.block) (P : C → A → Prop) 
           (Q' : B → Type) (args : list A) (ha : ∀ y : C,
                                                 Q y → ∥ All (R y) args ∥),
           {| pr1 := l; pr2 := Hl |} = {| pr1 := args; pr2 := ha |}
           → x = map_All f args ha
             → let H0 := CoreTactics.block in
               (∀ y : C, Q y → All (P y) args)
               → (∀ (x0 : A) (y : C) (rx : ∀ y0 : C, Q y0 → R y0 x0),
                    P y x0 → Q' (f x0 rx))
                 → ∀ y : C, Q y → All Q' (map_All f args ha)) xs
        (map_All_obligation_2 x xs h)
        (map_All f xs (map_All_obligation_2 x xs h))
  P : C → A → Prop
  Q' : B → Type
  ============================
   (let H := CoreTactics.block in
    (∀ y : C, Q y → All (P y) (x :: xs))
    → (∀ (x : A) (y : C) (rx : ∀ y0 : C, Q y0 → R y0 x), P y x → Q' (f x rx))
      → ∀ y : C,
          Q y
          → All Q'
              (map_All f (x :: xs)
                 (rew [λ l : list A, ∀ y0 : C, Q y0 → ∥ All (R y0) l ∥]
                      eq_refl in h)))


DEBUG:Going to execute:
match goal with
           | |- context [ rew <- [_] eq_refl in _ ] =>
                 progress simpl eq_rect_r
           | |- context [ rew [_] eq_refl in _ ] => 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