fact: Definition SU (I: sysuni) := exists (Delta: ctx) (sigma: fin -> exp X), (Delta ⊩ sigma : Gammaᵤ') /\ forall s t, (s, t) ∈ Eᵤ' -> sigma • s ≡ sigma • t.
imports: List Lia Undecidability.HOU(std.std calculus.calculus unification.higher_order_unification)