symbols should/might be type level lists of chars
I thought I had seen that feature request in trac but did not find it. Sorry if I am wrong.
A simple use case might be a type safe routing framework, e.g.
get :: Route "/a/:id" $ do idA <- param :: Param "idA" ...
I spoke with pedro at hacberlin last weekend and he told me simonp and iavor might tell me where to start looking.