Right now the definition of Control.Monad.void is:

void :: Functor f => f a -> f ()

void = fmap (const ())

I propose we replace it with
void :: Functor f => f a -> f ()
void = (() <$)
This expands out to the former definition by the default definition of (<$) and Data.Functor.Functor exports (<$) explicitly to make it possible to optimize this sort of thing. It seems a shame not to use it.
Discussion Period: 2 weeks