Definition Iso_respects_atoms_eq   := third  respects_atoms_eq_mutual.
Definition DefEq_respects_atoms_eq := fourth respects_atoms_eq_mutual.
(* Instance Iso_atoms_eq_mor : Morphisms.Proper (eq ==> AtomSetImpl.Equal ==> eq ==> eq ==> iff) Iso.  Instance DefEq_atoms_eq_mor : Morphisms.Proper (eq ==> AtomSetImpl.Equal ==> eq ==> eq ==> eq ==> iff) DefEq.  *)
(* ----- *)
Ltac binds_cons :=
let H5 := fresh in
match goal with
[
H4 : (∃ phi : constraint, binds ?x (Co phi) ?G) → False
|- ((exists phi, binds ?x (Co phi) ([(?y, ?s)] ++ ?G)) -> False) ] =>
intro H5; destruct H5; apply H4; simpl in H5;
destruct (binds_cons_1 _ x y _ s G H5); split_hyp; subst;
try done; eauto
end.

Lemma strengthen_available_noncovar:
(forall G1  a A,    Typing G1 a A -> True) /\
(forall G1  phi,    PropWff G1 phi -> True) /\
(forall G1 D p1 p2, Iso G1 D p1 p2 -> forall x, not (exists phi, binds x (Co phi) G1) ->
Iso G1 (remove x D) p1 p2) /\
(forall G1 D A B A1,DefEq G1 D A B A1 ->  forall x, not (exists phi, binds x (Co phi) G1) ->
DefEq G1 (remove x D) A B A1) /\
(forall G1 ,        Ctx G1 -> True).