Section RestrictActionTheory.
Variables (aT : finGroupType) (D : {set aT}) (rT : finType).
Variables (to : action D rT).
Variables (A : {set aT}) (sAD : A \subset D).
Canonical morph_action := Action mact_is_action.

Lemma injm_faithful : 'injm phi -> [faithful D, on setT | morph_action].