[Haskell-cafe] Type synonyms vs standard types

Hi everyone, Dumb question about declaring a function and type synonyms. There are to different declarations of the same function: attrNames :: String -> AttrDict -> [String] attrNames :: AttrClass -> AttrDict -> AttrNames First gives you the idea about exact types it expects (except AttrDict for which user has to take a look into the docs or sources) while the second one gives you the idea about meaning of parameters. Both reasons make sense. The question is when which one should be used? I'm using type synonyms everywhere and possibly without too much reasons... Maybe I should stop doing it? :) Cheers, Oleksandr.