(** Administrative lemmas for Fsub.  Authors: Brian Aydemir and Arthur Chargu\'eraud, with help from Aaron Bohannon, Jeffrey Vaughan, and Dimitrios Vytiniotis.  This file contains a number of administrative lemmas that we require for proving type-safety.  The lemmas mainly concern the relations [wf_typ] and [wf_env].  This file also contains regularity lemmas, which show that various relations hold only for locally closed terms.  In addition to being necessary to complete the proof of type-safety, these lemmas help demonstrate that our definitions are correct; they would be worth proving even if they are unneeded for any "real" proofs.  Table of contents: - #<a href="##wft">Properties of wf_typ</a># - #<a href="##oktwft">Properties of wf_env and wf_typ</a># - #<a href="##okt">Properties of wf_env</a># - #<a href="##subst">Properties of substitution</a># - #<a href="##regularity">Regularity lemmas</a># - #<a href="##auto">Automation</a># *)
Require Export Fsub.Fsub_LetSum_Infrastructure.
(* ********************************************************************** *)
(** * #<a name="wft"></a># Properties of [wf_typ] *)
(** If a type is well-formed in an environment, then it is locally closed. *)
(** The remaining properties are analogous to the properties that we need to show for the subtyping and typing relations. *)
Proof with simpl_env; eauto.
intros T E F G Hwf_typ Hk.
remember (G ++ E) as F'.
generalize dependent G.
induction Hwf_typ; intros G Hok Heq; subst...
Case "type_all".
pick fresh Y and apply wf_typ_all...
rewrite <- app_assoc.
apply H0...
Qed.
Proof with simpl_env; eauto.
intros V U T E F X Hwf_typ.
remember (F ++ X ~ bind_sub V ++ E) as G.
generalize dependent F.
induction Hwf_typ; intros F Heq; subst...
Case "wf_typ_var".
analyze_binds H...
Case "typ_all".
pick fresh Y and apply wf_typ_all...
rewrite <- app_assoc.
apply H0...
Qed.

Lemma wf_typ_strengthening : forall E F x U T,
wf_typ (F ++ x ~ bind_typ U ++ E) T ->
wf_typ (F ++ E) T.