fact: Definition Γ_step : list ty := map s_rule rs.
imports: Undecidability.IntersectionTypes.CD Undecidability.IntersectionTypes.Util.CD_facts Undecidability.StringRewriting.SSTS Undecidability.LambdaCalculus.Util.term_facts Relations List PeanoNat Lia ssreflect ssrfun