[Haskell-cafe] understanding typeable

i am trying to figure out how typeable works, so i have this data type data Foo = FooC Int deriving (Data, Typeable, Show) So how come this works:

funResultTy (typeOf ((+) 1)) (typeOf 1) Just Integer

but this doesnt:

funResultTy (typeOf FooC) (typeOf 1) Nothing

FooC is of type t -> u and 1 is of type t so the result should be u? I don't think t and u need to be the same since

funResultTy (typeOf (\a -> a:[1])) (typeOf 1) Just [Integer]

works fine. So given a constructor, how come i cant seem to construct a type out of it?