partially applied type synonyms

[Herbert Valerio Riedel]

Arie Peterson writes:

> Is there a good reason that partially applied type synonyms cannot be made
> instances of classes?

[...]

> Partially applied type synonyms are, in a sense, the anonymous functions
> at the type level, and one might argue that they deserve the same
> 'first-class member status' as the lambda at the value level.

According to SPJ, the problem seems to be requiring higher-order
unification for this to happen:

 http://www.haskell.org/pipermail/glasgow-haskell-users/2005-April/008340.html

Does anyone here know (as SPJ's response is quite a few years old) if
there's been made any progress since back then?

cheers,
hvr