proposition: Lemma contains_stepI {s t t'}: t' = subst_poly_type (s .: poly_var) t -> contains_step (poly_abs t) t'.
proof: Proof. move=> ->. by apply: contains_step_subst. Qed.
imports: List Lia Relation_Definitions Relation_Operators Operators_Properties Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Autosubst.unscoped Undecidability.SystemF.Util(Facts poly_type_facts pure_term_facts term_facts typing_facts iipc2_facts) ssreflect ssrbool ssrfun