Goal:
    A : Type  P : list A → list A → A → A → Type
  ============================
   (let H := CoreTactics.block in
    let H0 := CoreTactics.block in
    All_fold (λ (Γ : list A) (d : A), P Γ Γ d d) [])


DEBUG:Going to execute:
match T with
           | context [ CoreTactics.block ] =>
               change T; CoreTactics.intros_until_block
           end