have htp : app (app (fn 1) arg) arg ∶ argument :=
  HasType.appZero (HasType.appSucc HasType.fn HasType.arg) HasType.arg
hneg : ∀ {e : FnExp} {τ : FnType}, e ∶ τ → Value e ∨ ∃ e', BadStep e e'
⊢ False
hneg : ∀ {e : FnExp} {τ : FnType}, e ∶ τ → Value e ∨ ∃ e', BadStep e e'
htp : app (app (fn 1) arg) arg ∶ argument
⊢ False