proposition: Lemma typing_var_eq x: x ∈ Vars__de E -> Gamma__deq ⊢₂(2) varEQ x : alpha → alpha → alpha.
proof: Proof. intros; unfold varEQ; split; cbn [fst snd]. all: autotype; auto. Qed.
imports: RelationClasses Morphisms List Lia Init.Nat Setoid Undecidability.HOU(calculus.calculus second_order.diophantine_equations systemunification nth_order_unification)