Definition perm_of of phant T := perm_type.Identity Coercion type_of_perm : perm_of >-> perm_type.Notation pT := (perm_of (Phant T)).Canonical perm_eqType := Eval hnf in EqType perm_type perm_eqMixin.Canonical perm_choiceType := Eval hnf in ChoiceType perm_type perm_choiceMixin.Canonical perm_countType := Eval hnf in CountType perm_type perm_countMixin.Canonical perm_finType := Eval hnf in FinType perm_type perm_finMixin.

Lemma perm_proof (f : T -> T) : injective f -> injectiveb (finfun f).