proposition: Lemma nf_hf_atom Gamma N a : normal_form N -> type_assignment Gamma N (atom a) -> neutral normal_form N.
proof: Proof. case. + by constructor. + by move=> > ? /type_assignmentE. + by do ? constructor. + move=> > /normal_form_app_neutral *. by constructor. Qed.
imports: Undecidability.IntersectionTypes.CD Undecidability.IntersectionTypes.Util.CD_facts Undecidability.StringRewriting.SSTS Undecidability.LambdaCalculus.Util.term_facts Relations List PeanoNat Lia ssreflect ssrfun