proposition: Lemma HF_refl' T x : HFeq <<= T -> T ⊢ x ≡ x.
proof: Proof. intros H. change (T ⊢ ($0 ≡ $0)[x..]). apply AllE. apply Ctx. firstorder. Qed.
imports: Undecidability.FOL.ZF Undecidability.FOL.Syntax.Facts Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Sets.ZF Undecidability.FOL.Reductions.PCPb_to_HF Undecidability.PCP(PCP Util.PCP_facts Reductions.PCPb_iff_dPCPb) Undecidability(Shared.ListAutomation)