If I load the following into ghci:

{-# LANGUAGE TypeFamilies,
             PolyKinds
 #-}

type family Foo a

and then get the info on Foo, I get the following printout:

type family Foo k a :: *

It seems that ghc is inserting the kind variable k into the name of the type function Foo. Perhaps this was intended, but it seems counter-intuitive. A kind of * is also sometimes printed in different situations when compiling with PolyKinds.