Notation fun_of_fin := FunFinfun.fun_of_fin.Notation finfun := FunFinfun.finfun.Canonical fun_of_fin_unlock := Unlockable FunFinfun.fun_of_finE.Canonical finfun_unlock := Unlockable FunFinfun.finfunE.Notation "y .-support" := (support_for y)
  (at level 2, format "y .-support") : fun_scope.Notation fT := {ffun aT -> rT}.Implicit Types (f : fT) (R : pred rT).

Lemma ffunK : cancel (@fun_of_fin aT rT) (@finfun aT rT).