CanModifyFP

Capability: the focused A inside an S can be rewritten effectfully under any Functor[G] — the carrier-free surface of any optic whose carrier admits forgetful.ForgetfulTraverse[F, Functor] (today: Lens).

Prefer this trait in consuming signatures; the monomorphic CanModifyF alias covers the common case. See CanGet for the doctrine and the coherence rule.