Hugo Pacheco:

> Yes, but doesn't the confluence problem only occur for type synonyms
> that ignore one or more of the parameters? If so, this could be
> checked...

You can't check this easily (for the general case).

Given

  type family G a b

  type FList a x = G a x

  type instance F [a] = FList a

Does FList ignore its second argument?  Depends on the type instances
of G.

Manuel