Goal:
  
  A : Type
  B : Type
  C : Type
  Q : C → Type
  P : C → A → Prop
  x : A
  xs : list A
  y : C
  X : Q y
  h1 : list A
  ============================
   (All (P y) h1
    → x :: xs = h1
      → let H := CoreTactics.block in
        let H0 := CoreTactics.block in All (P y) xs)


DEBUG:Going to execute:
intros p