fact: Definition nf P := match P with abs s P => normal_form P | ty_abs P => normal_form P | P => head_form P end.
imports: Undecidability.SystemF.SysF Undecidability.SystemF.Autosubst.syntax Undecidability.SystemF.Autosubst.unscoped Undecidability.SystemF.Util.typing_facts Undecidability.SystemF.Util.term_facts Coq.Relations.Relation_Operators Coq.Program.Equality