Goal:
  
  A : Type
  B : Type
  C : Type
  Q : C → Type
  P : C → A → Prop
  fn : ∀ x : A, (∀ y : C, Q y → P y x) → B
  l : list A
  Hl : ∀ y : C, Q y → ∥ All (P y) l ∥
  call := map_All fn l Hl : list B
  ============================
   (#|call| = #|l|)


DEBUG:Going to execute:
lazymatch goal with
           | call:=?fp:_ |- _ => subst call; Init.funelim_constr fp
           end
DEBUG LTAC Evaluated term: (map_All fn l Hl)