fact: Fixpoint var_bound M := match M with | var x => 1 + x | app M N => 1 + var_bound M + var_bound N | lam M => var_bound M end.
imports: Undecidability.IntersectionTypes(CD Util.CD_facts) Undecidability.LambdaCalculus.Util.term_facts List PeanoNat Lia ssreflect