Goal:
  
  A : Type
  B : Type
  x : A
  xs : list A
  f0 : A → B
  H : ∀ (H := CoreTactics.block) (f : A → B) (l : list A) 
        (g : ∀ x : A, In x l → B),
        g = (λ (x : A) (_ : In x l), f x)
        → {| pr1 := xs; pr2 := λ (x : A) (_ : In x xs), f0 x |} =
          {| pr1 := l; pr2 := g |}
          → map_InP xs (λ (x : A) (_ : In x xs), f0 x) = map_InP l g
            → let H0 := CoreTactics.block in map_InP l g = map f l
  ============================
   (let H := CoreTactics.block in
    map_InP (x :: xs) (λ (x0 : A) (_ : In x0 (x :: xs)), f0 x0) =
    map f0 (x :: xs))


DEBUG:Going to execute:
cbn beta in hyp