ConstraintKinds and default associated empty constraints

[Bas van Dijk]

On 23 December 2011 17:44, Simon Peyton-Jones <simonpj at microsoft.com> wrote:
> My attempt at forming a new understanding was driven by your example.
>
> class Functor f where
>    type C f :: * -> Constraint
>    type C f = ()
>
> sorry -- that was simply type incorrect.  () does not have kind *  ->
> Constraint

So am I correct that the `class Empty a; instance Empty a` trick is
currently the only way to get default associated empty constraints?

Will this change in GHC-7.4.1? (For example by having an overloaded `()`)

The reason I ask is I would like to know if it's already feasible to
start proposing adding these associated constraints to Functor,
Applicative and Monad.

Cheers,

Bas